Paradoris indecora, Bergh, 1881

Dayrat, Benoît, 2006, A taxonomic revision of Paradoris sea slugs (Mollusca, Gastropoda, Nudibranchia, Doridina), Zoological Journal of the Linnean Society 147 (2), pp. 125-238 : 171-188

PARADORIS INDECORA ( FIGS 34–44 )

Discodoris indecora Bergh, 1881: 108–112 , plate J, figs 26–33, plate K, figs 11–19. – Bergh, 1884: 93. – Carus, 1893: 221. – Eliot, 1906 c: 136–137. – Vayssière, 1913: 320. – O’Donoghue, 1929: 764. – Pruvot-Fol, 1951: 14, plate II, fig. 13. – Pruvot-Fol, 1954: 270–272, fig. 107. – Sordi & Majidi, 1956: 240. – Haefelfinger, 1960: 336. – Schmekel, 1968: 115. – Barash & Danin, 1971: 180. – Nordsieck, 1972: 62, plate XI, fig. 15. – Barash & Danin, 1982: 102. – Schmekel & Portmann, 1982: 81– 83, fig. 7.14, plate 3, fig. 8, plate 30, fig. 9. – Templado, 1982: 251. – Ballesteros et al., 1986: 50–51. – Marin & Ros, 1987: 141. – Barash & Danin, 1992: 213–214. – Marin et al., 1997: 431–439, figs 1–5.

Paradoris indecora . – Templado, 1984: 519. – Cervera et al., 1988: 35. – Cattaneo-Vietti, Chemello & Giannuzzi-Savelli, 1990: 90–91, plate 5, fig. 8. – Perrone, 1990: 367. – Koutsoubas & Koukouras, 1993: 196. – Ortea, 1995: 6–13, figs 1D, 1F, 2–4. – Valdés, 2002: 595–599 , figs 34A, 35, 36.

Paradoris granulata Bergh, 1884: 686–691 , plate LXXVI, figs 10–24. – Carus, 1893: 223. – Vayssière, 1913: 320–321. – O’Donoghue, 1929: 765. – Pruvot-Fol, 1951: 19. – Gantès, 1956: 45. – Pruvot-Fol, 1954: 276– 277, fig. 111. – Franc, 1968: 870. – Perrone, 1990: 367– 370, figs 1, 2. – Cattaneo & Chemello, 1991: 293.

Paradoris granulata var. Bergh, 1884: 691–693, plate LXXVI, figs 25–32.

Discodoris cavernae Starmühlner, 1955: 219–223 , figs 5–9. – Schmekel & Portmann, 1982: 81. – Cattaneo- Vietti et al., 1990: 90–91. New synonym.

Paradoris inversa Ortea, 1995: 14–17 , figs 1C, 6–8. New synonym.

Paradoris ceneris Ortea, 1995: 21–25 , figs 1A, 1E, 13– 15. New synonym.

Paradoris mollis Ortea, 1995: 18–21 , figs 1B, 9–12. New synonym.

Type material: Holotype of indecora , by monotypy: [Adriatic Sea], Italy, Trieste [Zoological Station], March 1880 [the label indicates ‘? March 1880 ’], one specimen 20/ 12 mm preserved, leg. Dr Graeffe ( ZMUC GAS-2017). A note written in 1997 on the label of this specimen by Kathe Jensen, who has curated an important part of the malacological collection held by the ZMUC, indicates: ‘almost certainly is holotype of Discodoris indecora Bergh, 1881 ’. Contrary to what Valdés (2002) asserted, the type material of indecora is not lost. The holotype was entirely dissected prior to the present study. Only the body wall remains in the jar. Also, the rhinophores and the right oral tentacle are missing.

Seven syntypes of granulata : [Adriatic Sea], Italy, Zoological Station, Trieste. April–May 1879 −1880 [the label indicates ‘? 4–5/1879−1880?’], seven specimens 30/20 (#1), 28/17 (#2), 28/16 (#3), 24/16 (#4), 20/14 (#5), 18/13 (#6), and 11/10 (#7) mm preserved, leg. Dr Graeffe ( ZMUC GAS-2120). Valdés (2002) designated a lectotype (24 mm long) and six paralectotypes (from 8 to 24 mm long). However, the lectotype was not separated from the paralectotypes, and the current label still considers the seven specimens as syntypes (all under the same catalogue number ZMUC GAS-2120). In conclusion, Valdés’ designation of a lectotype did not contain information to ensure recognition of the specimen designated, and therefore is invalid. I decided to give a number to every syntype in order to avoid confusion (see remarks on the original description). The seven syntypes were entirely dissected prior to the present study. No internal organs remain, except for a digestive gland and six branchial plumes that could not be attributed to any specimen, a nervous system (syntype #5), and the distal part of the reproductive system (with the accessory glands and stylet sacs) attached inside the body wall (syntypes #5 and #6). Valdés (2002) did not point out the presence of these internal organs. The body wall of all specimens was still entire, except for syntype #2: its oral area and anterior foot were missing; a piece of its dorsal notum had been cut, probably by Valdés (2002: fig. 35E). Valdés (2002: fig. 35A–D) represented the radula and the jaw rodlets of one of the syntypes. Also, Valdés has not sent back the SEM stubs to the ZMUC and I could not re-examine them for the present study. I prepared several SEM stubs from the syntypes of granulata (Appendix 1): pieces of the dorsal notum (syntype #3); a rhinophore (syntypes #1, #5, #6, and #7); an oral tentacle (syntypes #1 and #4); and two branchial plumes.

Two syntypes of granulata var. Adriatic Sea , Italy, Trieste [the label indicates ‘? Triest’ but the original description clearly indicates that the specimens were collected from Trieste, at the Zoological Station], April / May 1879 /1880 [the label indicates ‘? 4–5/1879− 1880?’], two specimens 20/12 and 14/ 13 mm preserved, leg. unknown [the label currently indicates ‘ Coll:?’ but according to the original description both specimens were collected by Dr Graeffe] ( ZMUC GAS-2121). Both specimens were entirely dissected prior to the present study. No internal organs remain. The rhinophores are missing. Six gills remain in one specimen. These two specimens may have been dried for some time and are currently in very poor condition .

Syntypes of cavernae: Starmühlner did not indicate exactly how many specimens of cavernae he had collected. However, it seems that he collected many individuals because he explained that cavernae was abundant in the subtidal sea caves that he had explored. All the specimens used by Starmühlner in his description are syntypes because he did not designate a holotype. However, the material has not been deposited in a Viennese institution, neither at the university nor at the museum. I could not find where this type material could be – if it still exists. According to the original description, the type locality was the Capo di Sorrento, Italy. Finally, the condition of this type material is unknown.

Holotype of ceneris , by original designation: [Atlantic Ocean, Canary Islands], Lanzarote, Puerto de Arrecife , [28°57′N, 13°33′W], 13 December 1981, one specimen 20/ 13 mm preserved, leg. J. Ortea ( MNHN, no catalogue number). The holotype was entirely dissected by Ortea. The gills are still present in the jar as well as most internal organs: the distal area of the reproductive system (accessory glands, stylet sacs, etc.) and the buccal mass are missing; the prostate and the deferent duct are separated from the rest of the reproductive system. No slides or SEM stubs could be found at the MNHN.

Holotype of inversa , by original designation: [Atlantic Ocean, Canary Islands], Tenerife, El Medano, 28°02′N, 16°32′W, 23 July 1980, one specimen 25/ 15 mm preserved, 2 m depth, leg. J. Ortea ( MNHN, no catalogue number). The holotype was entirely dissected by Ortea. Most internal organs are still in the jar: the distal area of the reproductive system (accessory glands, stylet sacs, etc.) and the buccal mass are missing. No slides or SEM stubs could be found at the MNHN. The type material also includes two paratypes, not examined for the present study. One paratype was deposited at the MICN, Tenerife , and another paratype was deposited at the Laboratorio de Zoología de la Universidad de Oviedo. The paratypes have not been collected from the Canary Islands but from the Gulf of Guinea: one from Principe and the other from São Thomé.

Holotype of mollis , by original designation: [Atlantic Ocean, Canary Islands], Tenerife, Adeje , 28°20′N, 16°55′W, 15 July 1980, one specimen 13/ 9 mm preserved, leg. J. Ortea ( MNHN, no catalogue number). The holotype was entirely dissected by Ortea. Parts of the digestive system (digestive gland, stomach, intestine) are still present in the jar: the reproductive system and the buccal mass are missing. No slides or SEM stubs could be found at the MNHN.

Additional material dissected: [Adriatic Sea, Croatia], Istria, Premantura, station M10, 1– 2 m depth, 22 August 1968, nine specimens 9/4 (#1), 7/4 (#3), 6/3 (#2), 6/3 (#4), 5/2 (#5), 5/2 (#6), 4/2 (#7), 3/2 (#8), and 4/ 2 (#9) mm preserved, leg. H. Lemche, identified as D. indecora by H. Lemche ( ZMUC, no catalogue number); [Adriatic Sea, Croatia], Istria, Premantura, station M 9, 3 m depth, 21 August 1968, two specimens 12/7 (#10) and 5/3 (#11) mm preserved, leg. H. Lemche, identified as D. indecora by H. Lemche ( ZMUC, no catalogue number) [the large specimen was dissected prior to the present study, probably by Lemche; the radula, extracted, numbered #175, could not be found at the ZMUC]; [Adriatic Sea, Croatia], Istria, Premantura, station M 8, 2 m depth, 19 August 1968, two specimens 5/3 (#12) and 5/3 (#13) mm preserved, leg. H. Lemche, identified as D. indecora by H. Lemche ( ZMUC, no catalogue number); [Mediterranean Sea, off North African coasts], Spain, Ceuta, 28 May 1986, one specimen 25/ 18 mm preserved, leg. J. Ortea, identified as P. indecora by J. Ortea ( MNHN, no catalogue number) [this specimen was dissected by Ortea (1995); the rhinophores, the buccal mass, and the distal area of the reproductive system are missing; no slides or SEM stubs could be found at the MNHN]; [Mediterranean Sea, Spain], Murcia, Cabo de Palos, 1 January 1983, one specimen 7/ 3 mm preserved, leg. J. Templado, identified as P. indecora probably by J. Templado ( MNCN 15.05/18232); [Atlantic Ocean], Portugal, Sagres, 16 m depth, 13 May 1988, one specimen 30/ 20 mm preserved, leg. J. Ortea, identified as P. indecora by J. Ortea ( MNHN) [this specimen was dissected by Ortea (1995); the buccal mass and the distal part of the reproductive system are missing; no slides or SEM stubs could be found at the MNHN].

Type localities: Trieste ( indecora , granulata , granulata var.); near Naples ( cavernae ); and Canary Islands ( ceneris , inversa , mollis ).

Distribution: Mediterranean and eastern Atlantic Ocean. So far, indecora has been recorded from many localities from the western Mediterranean: Italy ( Bergh, 1881, 1884, as granulata and granulata var.; Pruvot-Fol, 1954, as granulata ; Starmühlner, 1955, as cavernae ; Sordi & Majidi, 1956; Schmekel, 1968; Schmekel & Portmann, 1982; Perrone, 1990, as granulata ; Cattaneo & Chemello, 1991, as granulata ; Marin et al., 1997; present study), Sardinia (Cattaneo- Vietti et al., 1990), France ( Pruvot-Fol, 1951, 1954; Haefelfinger, 1960), Spain ( Templado, 1982, 1984; Ballesteros et al., 1986; Marin & Ros, 1987; Cervera et al., 1988; Ortea, 1995, as indecora ; Marin et al., 1997; Valdés, 2002; present study), and off Ceuta, North African coasts ( Ortea, 1995; present study). It has also been recorded from the eastern Mediterranean, off Israel ( Barash & Danin, 1971, 1982, 1992) and in the Aegean Sea ( Koutsoubas & Koukouras, 1993). In the eastern Atlantic Ocean, indecora is known from the coasts of Portugal ( Ortea, 1995; present study), Morocco ( Gantès, 1956), the Canary Islands ( Ortea, 1995, as ceneris , indecora , inversa , and mollis ; present study). Note that indecora is cited under five names ( P. ceneris , P. granulata , P. indecora , P. inversa , and P. mollis ) in the European Register of Marine Species ( Costello, Emblow & White, 2001). Also, several authors recorded indecora without any description or with a very brief one ( Gantès, 1956; Sordi & Majidi, 1956; Haefelfinger, 1960; Schmekel, 1968; Barash & Danin, 1971, 1982, 1992; Nordsieck, 1972; Templado, 1982, 1984; Marin & Ros, 1987; Cervera et al., 1988; Cattaneo-Vietti & Chemello, 1991; Koutsoubas & Koukouras, 1993). These records should not be taken for granted, although they are probably correct; they will have to be verified, in particular the presence of indecora in the eastern Mediterranean. O’Donoghue (1929) simply mentioned the presence of indecora and granulata in the Mediterranean based on Bergh’s (1881, 1884) and Vayssière’s (1913) contributions, without adding new material or observations. Eliot (1906) described three specimens of indecora from the Cape Verde Island and Ortea (1995) described two specimens of inversa from Principe and São Thomé, Gulf of Guinea. However, the presence of indecora in the Gulf of Guinea and the Cape Verde Islands is not assumed here (see Discussion).

Internet: Several pictures of specimens of indecora are posted on the internet. Although they do not change our knowledge of the distribution, those pictures provide interesting information about the colour variation in live animals. Erwin Koehler’s website on the Opisthobranchs from the Mediterranean Sea and elsewhere includes several pictures taken by Mauro Doneddu, in Sardinia in 1994. These specimens, from 8 to 25 mm long, were collected up to 3 m depth. They are light grey, light cream; one is almost whitish; one bears patches of clearly distinct brown dots. Bill Rudman’s ‘Sea slug forum’ includes two pictures of indecora : one 5 mm long specimen, light cream, photographed by Franco De Lorenzi, from Finale Ligure, Italy, at 5 m depth; one 20 mm long specimen, cream, photographed by Arthur J. Telle from Gran Canaria Island, Canary Islands, at 4 m depth.

Occurrence: It seems that indecora is not a rare species in the western Mediterranean. Several authors have collected many specimens: 69 individuals from the Gulf of Naples ( Schmekel & Portmann, 1982), 53 and 56 individuals from the Cabo de Palos, Murcia, Spain ( Templado, 1982, 1984). However, this abundance may be seasonal. Only one record is known from the eastern Mediterranean. This suggests that indecora is probably more rare in the eastern part of the Mediterranean (although this might be due to fewer collections).

Habitat: So far, indecora has been found in a wide range of habitats: rocky bottoms, under stones ( Cattaneo-Vietti et al., 1990), on rocks and sea-grasses ( Haefelfinger, 1960), on Posidonia ( Templado, 1982; Marin & Ros, 1987), on sponges ( Ortea, 1995; as indecora and mollis ; present study, specimens ZMUC #12– 13), on algae (present study, specimens ZMUC #1–11). Individuals were collected within or just below the tidal zone ( Bergh, 1881, 1884, as granulata ; Starmühlner, 1955, as cavernae ; Haefelfinger, 1960; Cattaneo-Vietti et al., 1990; Ortea, 1995, as ceneris and inversa ; Valdés, 2002; present study), up to 30 m depth: at 6 m depth ( Ballesteros et al., 1986), from 2 to 25 m ( Schmekel, 1968), up to 16 m ( Ortea, 1995, as indecora and mollis ), from 9 to 11 m depth ( Perrone, 1990, as granulata ), at 23 m depth ( Templado, 1982), and finally up to 30 m depth ( Schmekel & Portmann, 1982). Marin et al. (1997) demonstrated that some specimens of indecora feed on Ircinia sponges. Of course, the fact that populations with a different ecology and a different feeding behaviour might be reproductively isolated cannot be excluded, but this would need to be tested.

Literature: Several authors have provided some information about the colour, general morphology, and radular features ( Bergh, 1881, 1884, as granulata and granulata var.; Eliot, 1906; Pruvot-Fol, 1951, 1954, as granulata and indecora ; Starmühlner, 1955, as cavernae ; Schmekel & Portmann, 1982; Ballesteros et al., 1986; Cattaneo-Vietti et al., 1990; Perrone, 1990, as granulata ; Ortea, 1995, as ceneris , indecora , inversa , and mollis ; Valdés, 2002). Several colour drawings or pictures of live animals have been published ( Schmekel & Portmann, 1982; Cattaneo-Vietti et al., 1990; Ortea, 1995, as ceneris , indecora , inversa , and mollis ; Valdés, 2002). A few authors have described the reproductive system ( Bergh, 1881, 1884, as granulata and granulata var.; Eliot, 1906; Pruvot-Fol, 1951, 1954, as granulata – largely based on Bergh’s original drawings; Starmühlner, 1955, as cavernae ; Schmekel & Portmann, 1982; Ortea, 1995, as ceneris , indecora , inversa , and mollis ; Valdés, 2002). However, individual variation has never been addressed. Marin et al. (1997) studied thoroughly the defence behaviour of indecora . Finally, note that several authors mentioned or commented on indecora , granulata , and cavernae when describing new species of Discodoris or Paradoris , but without providing new data (e.g. Bergh, 1884; Marcus, 1965, 1976; Marcus & Marcus, 1967; Baba, 1989; Miller, 1995).

Remarks on the original description of indecora ( Figs 34B, C , 37B, E ): The original description of indecora was based on a single specimen collected from Trieste, Adriatic Sea. Bergh (1881) observed this specimen when it was still alive, but ‘dying’, in Copenhagen. Alive, it measured 21 mm in length and 11 mm in width. The colour of the dorsal notum was covered with ‘olive-green-brown’ dots and ‘numerous scattered, small and large (diameter <1 mm), whitish, slightly elevated, roundish plumps’. These plumps certainly refer to what authors currently designate as the typical ‘granulation’ of indecora . The ventral surface was whitish with green-brown dots. The stalk of the rhinophores was whitish and the edge of the lamellae was black. The colour of the gills was similar to the dorsal notum, although a little bit darker. Thirteen months later, in alcohol, the same specimen was 18 mm long and 10 mm wide. The colour had just changed a little. This specimen is currently homogeneously colourless, whitish. The dorsal notum bears small roundish tubercles on the edges ( Fig. 34C ). Bergh mentioned several features such as: six tripinnate branchial plumes, rhinophores with 15–20 lamellae, grooved oral tentacles ( Bergh, 1881: fig. 26), a notched upper lip of the bilabiate anterior foot. The left oral tentacle is grooved ( Fig. 34B ). Bergh did not describe holes on the surface of the dorsal notum: I could not observe any wide holes with a dissecting microscope, but preservation may have greatly modified the notum. Bergh described the nervous system in detail. A few features noteworthy are: the smooth surface of the ganglia, the pedal ganglia independent from the cerebro-pleural ganglia, and the short circum-oesophageal nerve ring. The labial cuticle was composed of more than two lateral jaw plates, but Bergh did not clearly described three distinct jaw plates. However, Bergh (1884: plate K, fig. 14, 15) clearly represented jaw rodlets with a curved tip ( Fig. 37B ). Bergh mentioned a radular formula of 48 × (19-0-19) and distinctly represented teeth with a groove on the outer edge of the hook ( Fig. 37E ). However, Bergh did not mention whether the outermost lateral teeth had a dorsal spur, nor did he describe whether the base of the last outermost tooth bore a spur. In the reproductive system, Bergh described several features, such as a prostate divided into two parts (the first one whitish and the second one yellowish), a penis unarmed, a whitish, spherical bursa copulatrix (called ‘spermatotheke’), a pearshaped receptaculum seminis (called ‘spermatocyste’). Bergh did not explain whether the ‘penis’ was just the evaginable distal end of the deferent duct or a distinct, permanent, copulatory organ. More importantly, Bergh described a lobed gland in the vestibule, near the penis. However, he could not give a precise description of the distal area of the reproductive system because of ‘insufficient material.

Remarks on the original description of granulata ( Figs 34A, D , 35A, B , 36 , 37A, D , 38 ): The original description of granulata was based on seven alcoholpreserved specimens that measured up to 27 and 28 mm long and 17 and 19 mm wide (according to Dr Graeffe’s field notes, the largest specimens were 40 mm long alive). The colour of the dorsal notum of live animals was greyish with white ‘bumps’, i.e. low bosses. The rhinophores and the gills were whitish. Preserved, the specimens were greyish. The ventral surface was whitish with dark dots. These specimens are currently colourless. The dorsal surface is creamish or light greyish with (#3, #4, #5, #7) or without (#1, #2, #6) traces of small black dots ( Fig. 34A ); the ventral surface is creamish-whitish with (#1, #3, #4, #7) or without (#2, #5, #6) black dots. The dorsal notum is granulated with small roundish tubercles ( Figs 34A , 5A ). However, granulation can be dense (e.g. #1) or sparse (e.g. #6). Bergh mentioned six to eight tripinnate branchial plumes ( Fig. 36B ). This feature could not be verified because only six branchial plumes remain in the jar. Bergh mentioned rhinophores with 25 lamellae in the largest specimen. Four rhinophores were prepared for SEM in the present study, but it was very difficult to determine the exact number of lamellae: approximately 15 lamellae (#1, #5), probably less than 15 (#6), between 15 and 20 (#7). Bergh also described a notched upper lip of the bilabiate anterior foot, and a grooved oral tentacle ( Fig. 36A ). Bergh did not describe holes on the surface of the dorsal notum. These holes were difficult to recognize in the pieces of notum I prepared for SEM: the notum of syntype #1 was very poorly preserved and its surface was completely destroyed; the notum of syntype #3 was covered with numerous, round hollows separated by narrow ridges ( Fig. 35A, B ); those hollows, probably artificial, have obscured my observations of the wide holes. Bergh described the nervous system in detail. The nervous system of syntype #5, similar to Bergh’s description, is represented here. A few features are noteworthy ( Fig. 34D ): the smooth surface of the ganglia, the pedal ganglia fused from the cerebro-pleural ganglia, and the short circumoesophageal nerve ring. The labial cuticle was composed of two lateral plates and an additional, ventral one ( Fig. 37A ). Also, Bergh clearly described jaw rodlets with a curved tip ( Fig. 37D ). Apparently, Bergh observed the radula of the seven specimens. However, he did not give a formula for each of them. He gave a general range of variation. The total numbers of rows were 47, 48, 51, 53, and 56; and the total numbers of teeth per half-row were 16, 19, and 21. Bergh distinctly represented grooved teeth, which is confirmed by the pictures of the radula of one of the syntypes published recently ( Valdés, 2002; fig. 35). Valdés, however, gave a very unexpected radular formula of 20 × (22-0-22). This formula contradicts Bergh’s original description and all radular formulae published so far in Paradoris . Valdés did not discuss this peculiarity, and I could not re-examine the radula – Valdés has not sent back the SEM stub to the ZMUC with the rest of the type material. Bergh did not describe whether the outermost lateral teeth had a dorsal spur, nor did he describe whether the base of the last outermost tooth bore a spur. In the reproductive system, Bergh described several features, such as a penis, a greyish, spherical bursa copulatrix (called ‘spermatotheke’), a short pear-shaped, opaque whitish-yellow, receptaculum seminis (called ‘spermatocyste’). More importantly, Bergh described ‘some reverse-conical’ stylet sacs near the penis, but he did not describe their exact number. He pointed out that the stylet inside these sacs was similar to the spicules observed in the mantle. However, Bergh (1884: 690) admitted in a footnote that the condition of the examined material did not allow him to be certain of the anatomy of the distal part of the reproductive system. Actually, I could find some accessory glands and stylet sacs inside the body wall of two syntypes, embedded within some conjunctive tissue ( Fig. 38 ). Bergh must have overlooked them when he pulled the reproductive system out from the body wall, and Valdés (2002) overlooked them when he re-examined the type material of granulata . In one syntype (#5), I found three stylets and two ramified accessory glands, all in good condition ( Fig. 38A, B ). In the other syntype (#6), I observed one inconspicuous glandular structure that could be an accessory gland (or part of it) and three conspicuous stylet sacs, but this distal area was probably not complete ( Fig. 38C, D ). Bergh certainly did not see the accessory structures in these two specimens, which could explain why he did not give a precise number of glands and sacs in his description.

Remarks on the original description of granulata var. ( Fig. 37C ): The original description of the variety of granulata was based on two specimens 34/14 and 25/ 17 mm, alive. According to Bergh (1884), only the colour was different from the typical form of granulata : the specimens of the variety were darker than the typical form. Here I simply emphasize some interesting features. The colour of the dorsal notum of the large specimen was ‘blackish-grey-brown’ whereas the colour of the small specimen was ‘grey-brown’ alive and ‘olive-green’ preserved. These specimens are currently colourless. The large syntype is greyish dorsally and creamish ventrally, with black dots. The small syntype is creamish with dark dots dorsally and ventrally (similar to syntype #4 of granulata ). The stalk of the rhinophores was white, with lamellae similar to the dorsal colour; the gills were grey-brown too. The dorsal notum of both syntypes is granulated with small roundish tubercles. Bergh mentioned rhinophores with 25–30 lamellae. This could not be verified because the rhinophores are missing. Bergh did not describe holes on the surface of the dorsal notum: I could not observe any holes because the notum was not in good condition. The labial cuticle was composed of two lateral jaw plates, and an additional ventral plate. Apparently, Bergh gave the radular formula of both specimens: 56 × (23/24-0-23/24) in the large specimen, and 51 × (18-0-18) in the small specimen. In the reproductive system, Bergh described several features, such as a ‘penis’, a whitish, spherical bursa copulatrix (called ‘spermatotheke’), a pear-shaped, opaque yellow-whitish, receptaculum seminis (called ‘spermatocyste’). More importantly, Bergh described three stylet sacs and one accessory gland ramified in four or five branches in the distal part of the reproductive system ( Fig. 37C ). However, Bergh (1884: 693, footnote 2) pointed out that he could not determine with certainty the relationships among these glands and sacs.

Remarks on the original description of cavernae: The original description of cavernae includes little information about character variation, although Starmühlner (1955) apparently collected several specimens. The latter measured from 11/7 to 15/ 11 mm (either alive or preserved). The colour of the dorsal notum was bright brown with white ‘pustules’ (i.e. probably the dorsal granulation) and brown dots. The rhinophores and the gills were whitish. Starmühlner mentioned five to six tripinnate branchial plumes. He also described a notched upper lip of the bilabiate anterior foot, and a ‘rod-like’ oral tentacle. Starmühlner certainly overlooked the groove of the oral tentacles. The number of rhinophoral lamellae was not specified either. Starmühlner (1955: fig. 8) described and represented the nervous system in detail: the three ganglia (pedal, cerebral, pleural) seemed to be separate; the surface of the ganglia was smooth; the short circum-oesophageal nerve ring was short. The labial cuticle was composed of two lateral plates and an additional ventral plate. Starmühlner gave a range of variation for the radular formula: the number of rows varied from 35 to 40 and the number of teeth per half-row from 15 to 17. Starmühlner did not mention whether: (1) the teeth were laterally grooved, (2) the outermost lateral teeth had a dorsal spur, and (3) the base of the last outermost tooth had a spur. Starmühlner drew (schematically) the reproductive system of cavernae and described several features, such as a penis, a brown, oval bursa copulatrix (called ‘spermatotheca’), a spherical, whitish receptaculum seminis (called ‘spermatocyste’). More importantly, he described two digitiform ‘praeputial glands’, following Bergh’s terminology, i.e. the accessory glands. Starmühlner did not describe stylet sacs, but he may have overlooked them.

Remarks on the original description of ceneris ( Figs 35C, D , 39A, B ): The original description of ceneris was based on a single 25 mm long specimen. The dorsal colour of the holotype was cream-grey, with dark brown areas. The edges of the dorsal notum were yellowish. The ventral surface of all specimens was light grey, with no dots. Rhinophores were brown and white (12 lamellae). This specimen is currently whitish. The dorsal notum was granulated with conical tubercles of various sizes. It is currently almost smooth. The largest tubercles were brown with a white tip, and the smallest ones were white. Ortea (1995) mentioned six tri- quadripinnate branchial plumes, grey with dark brown pigments. The upper lip of the bilabiate anterior foot was notched; the oral tentacles were grooved. Ortea did not describe wide holes on the surface of the dorsal notum. A piece of notum of the holotype that I prepared for SEM was unfortunately not very well preserved. However, wide holes seemed to be present on the dorsal notum ( Fig. 35C, D ). The nervous system, not described by Ortea, could not be re-examined because it is missing. The labial cuticle was composed of two lateral plates, and an additional ventral plate. Also, Ortea described jaw rodlets with a curved tip. The radular formula was 50 × (17-0-17). Ortea’s (1995: fig. 11) drawings of the lateral teeth do not distinctly represent grooved teeth. The outermost lateral teeth seemed to have a dorsal spur; the last outermost tooth was vestigial. Ortea described a free, large stomach, above the digestive gland. In the reproductive system ( Fig. 39A, B ), Ortea described a few features: a ‘hyaline’ bursa copulatrix with a yellow centre, a receptaculum of ‘similar colour and shape’, a prostate bent upon itself, no stylet sac or accessory gland. I could re-examine part of the reproductive system (both the distal area and the prostate were missing): Ortea overlooked a distinct loop of the vaginal duct, near the bursa copulatrix.

Remarks on the original description of inversa ( Figs 35E, F , 39C, D ): Ortea (1995) created the new name inversa based on three specimens: the holotype, from the Canary Islands, and two paratypes from Principe and São Thomé, in the Gulf of Guinea. The fact that these three specimens are part of a single species is questionable. In that regard, the original description of inversa is highly problematic, because Ortea did not indicate which specimen(s) he used to draw and describe the general anatomy, the reproductive system, and the jaws. The specimens, probably alive, were 20 mm long (holotype), 26 mm long ( Principe), and 23 mm long (São Thomé). The dorsal colour of the holotype was dark grey with minute grey-blue dots, whereas the paratypes were cream. The ventral surface of all specimens was white-grey, with no reddish dots. The holotype is currently light grey on the dorsal surface and whitish on the ventral surface. The rhinophores of the holotype were greypurple (stalk) and white and black-purple (12 lamellae). The dorsal notum was granulated with tubercles of various sizes. Ortea mentioned six tripinnate branchial plumes, the three anterior ones being smaller than the three posterior ones. All preserved branchial plumes have the same size. The upper lip of the bilabiate anterior foot was notched, and the oral tentacles were grooved. Ortea did not mention the presence of holes on the surface of the dorsal notum. A piece of notum of the holotype that I observed with SEM was unfortunately covered with many round hollows separated by narrow ridges that may have obscured the wide holes ( Fig. 35E, F ). The nervous system, not described by Ortea, was drawn for the present study. The labial cuticle was composed of two lateral plates, and an additional, ventral plate. Also, Ortea described jaw rodlets with a curved tip. The latter was deeply grooved in the middle. The radular formula of the holotype was 46 × (16-0-16). Ortea’s (1995: fig. 7E) drawings of the lateral teeth do not distinctly represent grooved teeth, nor do they indicate the precise shape of the outermost teeth. Ortea described a stomach ‘not well differentiated from the intestine’. In the holotype, it is actually free, large, above the left, anterior side of the digestive gland, and well differentiated from the intestine, unlike in Ortea’s drawing ( Ortea, 1995: fig. 8A): Ortea probably represented the stomach of a paratype. In the reproductive system ( Fig. 39D ), Ortea described several features, such as a brown, oval bursa copulatrix (called ‘glándula gametolítica’), a pear-shaped, white receptaculum seminis, two branched accessory glands, and two stylet sacs. The reproductive system of the re-examined holotype differs from Ortea’s drawing. In particular, the receptaculum is spherical (not elongated, pear-shaped), the bursa copulatrix is surrounded with the ampulla and the prostate (not free), and the vaginal duct makes a distinct loop near the bursa copulatrix (not straight). Again, Ortea probably represented the reproductive system of a paratype.

Remarks on the original description of mollis: The original description of mollis was based on a single 30 mm long specimen. The dorsal colour of the holotype was blackish, but lighter on the edges. The ventral surface of all specimens was light grey, with no dots. This specimen is currently light grey on the dorsal surface and whitish on the ventral surface: it could not be distinguished from the holotype of inversa . Rhinophores are grey (stalk) and white and dark grey (ten lamellae). The dorsal notum was granulated with white tubercles of various sizes. It is currently almost smooth. The texture of the mantle was soft, not hard. Ortea (1995) mentioned six tripinnate branchial plumes, an upper lip of the bilabiate anterior foot notched. The oral tentacles are grooved (a feature not described by Ortea). Ortea did not describe wide holes on the surface of the dorsal notum. Some may be present, but they are certainly not conspicuous. The nervous system, not described by Ortea, could not be re-examined because it is missing. The labial cuticle was composed of two lateral plates, and an additional, ventral one. Also, Ortea described jaw rodlets with a curved tip. The radular formula was 54 × (18-0-18). Ortea’s (1995: fig. 11) drawings of the lateral teeth do not distinctly represent grooved teeth. The outermost lateral teeth seemed to have a dorsal spur; the last outermost tooth was vestigial. Ortea described a free, large stomach, on the left above the digestive gland. In the reproductive system, Ortea described a few features: a ‘bursa copulatrix much larger than the receptaculum seminis and comprised physically between the ampulla and the prostate’, two stylet sacs, no branched accessory gland. According to Ortea’s (1995: fig. 12B) drawing, the bursa copulatrix is larger than the receptaculum seminis, but this is not strikingly different from what he drew for inversa ( Ortea, 1995: fig. 8C). I could not verify any of these features because the receptaculum seminnis was missing.

Description of additional specimens ( Figs 40–44 ): Unfortunately, no colour picture or field notes were available for the additional material dissected. Preserved specimens are: creamish with some greyish areas and brown dots dorsally ( Fig. 41A ) and whitish ventrally ( ZMUC); greyish dorsally and creamish with a few dots ventrally ( MNHN); and light greyish creamish on both surfaces ( MNCN).

The body is oval, slightly elongated in small specimens. The largest specimen is 30 mm long preserved, i.e. approximately 35/ 40 mm long alive ( MNHN Sagres), but this specimen was dissected prior to the present study ( Ortea, 1995). The largest specimen not dissected prior to the present study is 9 mm long, preserved, i.e. approximately 13 mm long alive ( ZMUC #1). The foot is rounded posteriorly and anteriorly. The width of the foot equals approximately one-third or one-half of the width of the dorsal notum (in preserved specimens). The anterior margin of the foot is bilabiate and the upper lip is notched ( Fig. 41B ). The two grooved oral tentacles are digitiform or conical ( Fig. 41B ). The dorsal notum ( Figs 40 , 41C ) bears low conical tubercles of unequal sizes. Wide holes could be observed on the surface of the dorsal notum ( Fig. 40 ), although the poor condition of the notum or the presence of hollows and ridges sometimes obscured them ( Fig. 40C–E, I ). Small holes (diameter <10 µm) and tufts of cilia could not be recognized, because of the poor condition of the notum. In preserved specimens, the margins of the rhinophoral and branchial sheaths are smooth or loosely crenulate. There are six ( MNHN Sagres, MNHN Ceuta, ZMUC #10) tripinnate branchial plumes; the number of branchial plumes was not distinguishable in the small specimens from Istria ( ZMUC). The rhinophores have between five and 15 lamellae, depending on the size of the specimen: for example, five ( ZMUC #13), eight ( MNCN), 12 or 13 ( ZMUC #10), ten to 15 ( MNHN Sagres). Rhinophores are missing in the specimen from Ceuta ( MNHN).

The stomach is (as in most other Paradoris ) intermediary between a narrow, median pouch, and a free, large pouch. The shape and the position of the stomach clearly vary. For example, in a specimen from Istria ( ZMUC #10 ), the stomach is narrow and median; in another specimen from Istria ( ZMUC #2 ) and in the specimen from Ceuta ( MNHN), the stomach is intermediary ( Fig. 41D ). The caecum is not conspicuous in all specimens. The intestine is straight and dorsal. The labial cuticle is armed with two lateral jaw plates, and an additional, ventral plate. Rodlet tips are irregularly shaped, pointed or rounded ( Fig. 42 ). Jaw rodlets have a curved tip. The radula is elongated ( Fig. 43 ): its length equals at least three times its width. The radular sac can be seen by dorsal dissection. Radular formulae are: 30 × (16-0-16) in a 9 mm long specimen ( ZMUC #1 ), c. 29 × (12-0-12) in a 7 mm long specimen ( ZMUC #3 ),> 16 × (12-0-12) in a 6 mm long specimen ( ZMUC #2 ),> 25 × (12-0-12) in a 6 mm long specimen ( ZMUC #4 ), 24 × (13-0-13) in a 5 mm long specimen ( ZMUC #6 ), 20 × (11-0-11) in a 5 mm long specimen ( ZMUC #5 ), and c. 21 × (10-0-10) in a 3 mm long specimen ( ZMUC #8 ). Note that part of the radula of one specimen was lost during its preparation ( ZMUC #2 ), and its small number of rows is artificial. Also, the radular formula of the specimen from Murcia ( MNCN) could not be determined. All radulae are symmetrical: the left and the right sides have the same number of teeth. The rachidian teeth are absent and the rachidian space is narrow. The rows of lateral teeth are at an angle of approximately 45 degrees with the rachidian axis. The size of the lateral teeth is globally constant, although the size of lateral teeth tends to smoothly increase towards the margins, except for the three or four innermost ones and the last three or four outermost ones, which are smaller. All teeth are hamate, except for the outermost one that may be vestigial (e.g. ZMUC #1). The hook of all lateral teeth is grooved on its outer edge. Teeth have no denticles. A ‘dorsal spur’ is present on the hook of the outermost teeth in all specimens. The base of the last outermost tooth can bear a spur ( ZMUC #2 ) or not ( ZMUC #2 ); in many cases, I could not see this feature or it was ambiguous .

The nervous system was missing in the two large specimens ( MNHN Ceuta, MNHN Sagres). In small individuals ( MNCN, ZMUC), the nervous systems were in very poor condition and not informative.

No reproductive system was found in several specimens, because of their small size ( ZMUC #2–9). Two reproductive systems were immature ( ZMUC #1, MNCN). The reproductive system of the largest specimen from Istria ( ZMUC #10) was missing. Finally, the reproductive system of specimens dissected prior to the present study was incomplete ( MNHN Sagres, MNHN Ceuta). However, a few features could be observed ( Fig. 44 ). The white ampulla makes two or three loose loops before it disappears into the female gland mass. The division of the ampulla into a male duct and a female duct is hidden within the female gland mass, and could not be seen by dissection. The prostate is flattened and divided in a proximal, whitish part, and a yellowish, distal part ( MNHN Sagres); the prostate of the specimen from Istria ( ZMUC #1) was homogeneously whitish; the prostate of the specimen from Ceuta ( MNHN) was missing. The white deferent duct is almost straight ( ZMUC #1); the deferent duct of the other specimens was missing. There is no distinct penis at the distal end of the deferent duct ( ZMUC #1). The vaginal duct is straight ( MNHN Ceuta, MNHN Sagres) or loosely convoluted near the bursa copulatrix ( ZMUC #1). The fertilization duct is convoluted, with a few distinct loops ( MNHN Ceuta, MNHN Sagres). The duct of the receptaculum seminis is short and straight, but distinct. The disappearance of the fertilization duct into the female gland mass (where it connects to the fertilization chamber) is distinguishable. The size of the bursa copulatrix equals approximately two or three times the size of the receptaculum seminis. Both pouches are spherical-ovate, smooth, not attached to each other. In the distal part of the reproductive system of the specimen from Murcia ( MNCN), there is a small pouch that could be interpreted as a developing stylet sac ( Fig. 44B ). There is no accessory gland or stylet sac in the distal part of the immature specimen from Istria ( ZMUC #1). The distal part of the reproductive system of the other specimens ( MNHN Ceuta, MNHN Sagres) was missing.

Diagnostic features: No diagnostic character could be found for indecora .

Character variation: Here I give a synthesis of the character variation based on the original descriptions, my own observations, and the additional literature on specimens identified (other than original descriptions). I clearly indicate the sources of information in order to avoid confusion. The specimens described from the Cape Verde Islands ( Eliot, 1906) and the Gulf of Guinea ( Ortea, 1995) are not considered here (see Discussion).

The maximum length is 40 mm long, alive: 18 mm ( Sordi & Majidi, 1956), 20 mm ( Schmekel & Portmann, 1982), 20 and 26 mm ( Perrone, 1990), generally 15–20 mm and maximum 23 mm ( Cattaneo-Vietti et al., 1990), approximately 25 mm ( Pruvot-Fol, 1951), 29 mm ( Ballesteros et al., 1986); 30 mm ( Ortea, 1995), 40 mm ( Bergh, 1884).

All descriptions have mentioned a minutely granular dorsal notum with roundish or conical tubercles of unequal sizes. This granulation is referred to as ‘ indecora -like’ granulation throughout the present contribution.

The colour has been described as: light grey dorsal notum with white and black dots (the latter around the large tubercles), light branchial plumes with yellow edges, white ventral surface with black dots ( Pruvot-Fol, 1951); grey-brown or golden-brown dorsal notum covered with black, brown, and white dots at higher magnification, with golden-brown spots on the margin, golden-brown rhinophores and gills, whitish ventral surface with some brown spots ( Schmekel & Portmann, 1982); pale grey dorsal notum, pale brown in the centre ( Valdés, 2002); grey-brown or golden-brown dorsal notum, often ‘covered by minute dark brown, opaque white or golden dots, which may be concentrated in groups forming clear spots’ ( Cattaneo-Vietti et al., 1990); grey-brown dorsal notum, transparent rhinophores, brown gills, ventral surface whitish with brown dots ( Ballesteros et al., 1986); brown dorsal notum ( Sordi & Majidi, 1956); yellowish, with a few dark dots on the ventral surface ( Perrone, 1990). In summary, the colour varies from cream, light grey, to grey-brown and blackish. I think that addressing colour variation will require many colour pictures of live animals from different localities: written colour descriptions are not satisfactory.

Several authors mentioned grooved oral tentacles ( Schmekel & Portmann, 1982; Ballesteros et al., 1986; Perrone, 1990; Valdés, 2002). Authors who did not mention grooved oral tentacles certainly overlooked the groove (e.g. Pruvot-Fol, 1951; Starmühlner, 1955).

The number of gills varies from six to eight ( Schmekel & Portmann, 1982; Ballesteros et al., 1986; Ortea, 1995; Valdés, 2002). The number of rhinophoral lamellae varies from five (present study) to 20 (types of indecora and granulata ).

There are two lateral plates and an additional ventral plate. Valdés (2002), who described only two jaw plates, certainly overlooked the ventral plate.

In addition to the radulae described in original descriptions, seven radular formulae have been published prior to the present study: 38 × (12-0-12) and 40 × (15-0-15) in two 9 mm long specimens ( Schmekel & Portmann, 1982); 40 × (15-0-15), probably based on Schmekel & Portmann’s work ( Cattaneo-Vietti et al., 1990); 51 × (20-0-20) in a 30 mm long specimen ( Ortea, 1995); Perrone (1990) mentioned 20–21 teeth per halfrow, but did not give the number of rows; Pruvot-Fol (1951) also mentioned 16 teeth per row without giving the exact number of rows of the ‘long and narrow’ radula. The formula provided by Valdés (2002), 20 × (22-0- 22), contradicts all other formulae: the radula was surely not complete (see remarks on the original description of granulata ). In summary, the number of rows varies from 20 (for 11 teeth per half-row) in a 5 mm long specimen, preserved (present study, ZMUC #5), to 56 (for 23/24 teeth per half-row) in a 34 mm long specimen, alive ( Bergh, 1884, as granulata var.); the number of teeth per half-row varies from ten (for approximately 21 rows) in a 3 mm long specimen, preserved (present study, ZMUC #8), to 23/24 (for 56 rows) in a 34 mm long specimen, alive ( Bergh, 1884, as granulata var.). The number of rows is always superior to at least twice the number of teeth per half-row, as in all Paradoris species.

In the reproductive system, different combinations of ramified, accessory glands and stylet sacs have been observed: no gland and no sac ( Ortea, 1995, as ceneris ), no gland and two sacs ( Ortea, 1995, as mollis ), one gland and one sac ( Schmekel & Portmann, 1982), one gland and two sacs ( Valdés, 2002), one gland and three sacs ( Bergh, 1884, as granulata var.; Perrone, 1990), two glands and no sac ( Starmühlner, 1955), two glands and three sacs ( Ortea, 1995, as indecora ; syntype of granulata , present study). Also, I found no gland and no sac in some immature reproductive systems. In summary, there is a maximum of two ramified, accessory glands, and three stylet sacs.

Discussion: My main goal here is to demonstrate that the names cavernae , ceneris , inversa , and mollis are synonyms of indecora . I discuss separately the case of the specimens collected from the Cape Verde Islands ( Eliot, 1906) and the Gulf of Guinea ( Ortea, 1995).

Contrary to what Ortea (1995) and Valdés (2002) asserted, the first author who transferred indecora from Discodoris to Paradoris was, as far as I can discern, Templado (1984). Bergh (1881) specifically mentioned at the end of his description of indecora that the placement of this species in Discodoris was a preliminary, uncertain choice, because of the granulated dorsal notum and the grooved oral tentacles. Some authors have not shared his doubts. For example, Pruvot-Fol (1951) asserted that, despite Bergh’s original doubt concerning the placement of indecora , there was no doubt that it belonged to Discodoris .

Although Templado (1984), Cervera et al. (1988), Perrone (1990), and Cattaneo-Vietti et al. (1990) did not justify their taxonomic decision, the fact that they would classify indecora within Paradoris directly implied that the description of indecora was no longer incompatible with Bergh’s (1884: 686) diagnosis of Paradoris : for example, dorsal notum granulated, labial cuticle composed of three jaw plates instead of two, presence of accessory glands near the genital opening, some containing stylets – note that Bergh did not mention the narrow, elongated radula in the diagnosis of Paradoris . Bergh described all these characters in the original description of indecora , except for the three jaws. However, Bergh’s description of the jaw plates of indecora was ambiguous: he wrote that the labial cuticle was armed with more than two jaw plates, but he could not determine exactly how many jaw pieces there were (see remarks on the original description of indecora ). Although they did not specifically write it, I guess that Templado (1984), Cervera et al. (1988), Perrone (1990), and Cattaneo-Vietti et al. (1990) thought that the number of jaws in Bergh’s original description could be ignored, and that indecora could thus be transferred to Paradoris . I cannot agree more with them. Surprisingly, Bergh did not mention the existence of indecora when he published the description of granulata , although both species were described from the same locality.

Ortea (1995) suggested that we regard granulata as a synonym of indecora . I certainly agree with this synonymy. However, it is regrettable that Ortea did not discuss it more thoroughly. Bergh was repeatedly cautious about the fact that he could not determine with certainty the number and the relationships of accessory glands and stylet sacs near the genital openings (see his footnotes in the descriptions of granulata and indecora ). Even after dissecting ten specimens (one specimen for indecora , seven for granulata , and two for granulata var.), Bergh still thought that he did not have enough material to describe properly the anatomy of these glands. It is worth pointing out that, to my knowledge, Bergh was rarely so cautious. However, accessory, genital structures are not conspicuous and I certainly understand Bergh’s hesitation. In this context, it is quite surprising that Ortea (1995) would then distinguish three new species – ceneris , inversa , and mollis – exclusively based on the number of accessory glands and stylet sacs.

According to Ortea (1995), indecora is characterized by having two ramified accessory glands and three stylet sacs. First, let us analyse the variation in the number of ramified accessory glands and stylet sacs in the literature cited by Ortea (1995) for granulata and indecora . Because Ortea did not cite P. granulata var. in the list of synonyms of indecora , I shall not assume here that Ortea included this variety within indecora . This issue is critical for two reasons: (1) Bergh created a variety because two specimens had a darker (grey) notum, which is a characteristic of one of Ortea’s new species, mollis ; (2) more importantly, the description of the variety of granulata is the only description where Bergh was explicit about how many glands and sacs he had observed. Ortea did not discuss the fact that Bergh had described one ramified gland and three stylet sacs in the variety of granulata , nor did he discuss its taxonomic status. Ortea also ignored the fact that Perrone (1990) mentioned one ramified gland and three stylet sacs in granulata . It is unclear whether Perrone observed those structures or simply cited Bergh’s description, but Ortea had to discuss Perrone’s description. Schmekel & Portmann (1982) reported one ramified accessory gland and one stylet sac. Ortea cited their contribution but did not discuss it.

I do not pretend that one must not use the number of ramified glands and stylet sacs as a criterion to distinguish species. However, I argue that one must evaluate the individual variation in this number before one uses it as a taxonomic character. The literature available when Ortea (1995) created three new species names – ceneris , inversa , and mollis – strongly indicated that the number of glands and sacs could vary among individuals of indecora . Because Ortea’s new species names were based on the description of one specimen ( ceneris and mollis ) and three specimens ( inversa ), the variation in the number of glands and sacs can be easily explained by infra-specific variation. There was no need to create three new species names.

More recently, Valdés (2002) mentioned one ramified gland and two stylet sacs in the reproductive system of a specimen of indecora from the Mediterranean coast of Spain. The two syntypes of granulata that I could re-examine had three ramified glands and two stylet sacs (syntype #5), and one accessory gland (or part of it) and three stylet sacs (syntype #6), although the distal area of the reproductive system of the latter specimen was probably not complete.

Let us briefly comment on some of the other differences that Ortea (1995) mentioned among indecora , ceneris , inversa , and mollis . According to Ortea (1995), the best diagnostic feature of inversa was the absence of reddish dots on the ventral surface. However, this absence could easily be explained by individual variation. Ortea also mentioned the presence of anterior branchial plumes larger than the posterior ones, and the ventral surface ‘a little spiculose’. Both of these differences are meaningless, especially the size of branchial plumes. According to Ortea, the best diagnostic feature of mollis is the soft texture of the mantle. This could easily be explained by individual variation. Ortea also mentioned differences in the colour, the branchial plumes ‘very posterior’, the shape of the three jaw plates, the shape of the teeth, and the number of accessory glands and stylets. All these differences are easily explained by individual variation. Finally, according to Ortea, the best diagnostic feature of ceneris is the lack of accessory glands and stylet sacs. He also mentioned differences in the colour, the branchial plumes, the shape of the rhinophores, and the shape of the third, ventral jaw plate. All these differences are easily explained by individual variation. Ortea considered that mollis was ‘primitive’ within Paradoris because of the lack of accessory glands and stylets, and because of the weak notch of the upper lip of the bilabiate anterior foot.

Valdés (2002) thought that ceneris , inversa , and mollis were ‘distinct [from indecora ] in several anatomical details’, but did not mention these details. It is actually difficult to know what features Valdés had in mind. Indeed, contrary to what Valdés asserted, the new specimen of indecora he described from Murcia, Spain, was not ‘identical to Ortea’s (1995) redescription of this species’. For example, Ortea described three jaw plates: Valdés described two jaw plates. Ortea described a 51 × (20-0-20) radular formula in a 30 mm long specimen: Valdés described a 20 × (22-0-22) formula in a 24 mm long specimen. Ortea described two ramified accessory glands and three stylet sacs: Valdés described one ramified accessory gland and three stylet sacs.

I also regard cavernae as a synonym of indecora . Several authors have noticed the similarity between cavernae and indecora . Schmekel & Portmann (1982) eventually commented on cavernae when they redescribed indecora . According to these authors, however, the main difference between cavernae and indecora is found in the shape and the colour of the spermatic pouches: the brown bursa copulatrix is oval in cavernae and spherical in indecora ; the receptaculum seminis is white and spherical in cavernae , bright in indecora . However, Schmekel & Portmann did not propose a synonymy between cavernae and indecora . Cattaneo-Vietti et al. (1990) argued (although with a question mark) that cavernae could be a synonym of indecora . This would imply that cavernae had to be transferred to Paradoris , which I entirely agree with because cavernae presents all the diagnostic features of Paradoris .

The difference in the number of accessory glands and stylet sacs between cavernae and indecora can be explained by individual variation or by the fact that Starmühlner may have overlooked stylet sacs. However, I wish to point out that the specimens studied by Starmühlner were significantly smaller (15 mm maximum length) than the other specimens known (30 mm maximum length) and it cannot be excluded that the specimens that Starmühlner dissected were not mature (as a matter of fact, his drawing of the reproductive system of cavernae represented a female gland mass smaller than the prostate, which indicates that the genital organs were not fully developed). Note that Marcus & Marcus (1967) briefly mentioned the existence of cavernae when they discussed the taxonomic status of a new species, D. phoca Marcus & Marcus, 1967 . However, they did not propose to transfer cavernae to Paradoris .

I cannot emphasize strongly enough that I do not refuse by principle the idea that several characters could be used as diagnostic characters to distinguish different species of Paradoris in the Mediterranean and the Canary Islands. Rather, I argue that, given our current knowledge, the simplest hypothesis is that all the specimens collected so far from the Canary Islands and the Mediterranean form one polymorphic species. Polymorphism can be due to different factors: different stage of maturity (e.g. radular formulae, number of accessory glands and stylet sacs), natural individual variation (e.g. colour), or difficulty of observation (e.g. number of accessory glands and stylet sacs).

Five specimens of Paradoris have been collected from tropical, eastern Atlantic: three specimens from the Cape Verde Islands that Eliot (1906) identified as D. indecora ; two paratypes of inversa , from Principe and São Thomé, Gulf of Guinea. Eliot’s specimens (30 mm maximum length) belong to Paradoris , because they have grooved oral tentacles, ‘perhaps an accessory folliculate gland in the vestibule’, and a radular formula of 51 × (16/17-0-16/17). Eliot’s description of the jaw plates was interesting: ‘The labial cuticle consists of two hatchet-shaped plates, which can also be possibly regarded as representing a circle with two processes extending backwards.’ This description represents exactly what one usually sees in Paradoris : the jaws form a circle; Eliot’s ‘processes’ are probably the third ventral jaw plate that seems to be composed of two distinct plates when it is deeply grooved in the front. However, it is difficult to decide whether these specimens are part of indecora . The colour of these specimens (blue-grey dorsally, with some white blotches, and white ventrally) is not incompatible with the colour of indecora , but this by no means indicates that they are part of indecora . Ortea (1995) thought that the specimens identified as indecora by Eliot were not part of indecora because they had only four branchial plumes. In reality, Eliot’s description of the gills is more complicated: Eliot mentioned four gills, but he also pointed out the existence of a ‘bifid’ plume in one specimen, and an additional, asymmetrical small plume in another individual; the number of plumes should certainly not be taken as a criterion to exclude these specimens from indecora . Given that there is no diagnostic feature for indecora , there is no real reason to exclude the specimens collected from the Cape Verde Islands and the Gulf of Guinea from indecora . However, these localities would represent a major extension of distribution for indecora , and I prefer to consider that indecora simply refers to individuals collected from the Mediterranean and the temperate waters of the eastern Atlantic.

In summary, I think that the data currently available do not support the hypothesis that there are five species of Paradoris in the Mediterranean and the eastern Atlantic Ocean. However, this does not mean that there is only a single polymorphic, widespread species. Currently, indecora can be regarded as a name that designates a species complex whose structure is still unknown. The fact that individuals of indecora have been found in many different habitats (algae, sponges, etc.) suggests that there might be different, sympatric species, with distinct feeding behaviours. Also, the fact that specimens from very distant localities are not distinguishable (at least with the information currently available), suggests that morphology may be limited for distinguishing units within this species complex. The most efficient way to address the taxonomy of Paradoris in the Mediterranean and eastern Atlantic would be an integrative approach combining phylogeography and a study of character variation in large populations (Dayrat, 2005). In this regard, it will be necessary to keep precise track of several features before specimens could be preserved, especially the nature of the habitat, and the colour of both the ventral and dorsal surfaces.

Ortea (1995) thought that Verany (1846a, b) may have provided an early description of indecora under the name ‘ Doris porri ’. Verany actually used the name ‘ Doride di Porro ’. Verany published twice the same, brief description. As far as I know, this description was not accompanied by a figure. It is thus impossible to know which species Verany wanted to designate. Ortea also cited Doris infranaevata Abraham, 1877 , from the Mediterranean, as a possible, early reference of indecora . This name actually refers to a species that belongs to Platydoris (because of the presence of grooved oral tentacles and a six-lobed gill opening). Its affinities with Platydoris argo Linnaeus, 1767 still need to be studied: Dorgan, Valdés & Gosliner (2001) did not consider infranaevata .

Figures

Figure 5. Paradoris dubia, paratype of leuca, MNZ M.117833. A, dorsal notum, scale = 100 µm. B, jaw rodlets, scale = 20 µm. C, jaw rodlets, scale = 10 µm. D, radula, scale = 300 µm. E, innermost lateral teeth, scale = 20 µm. F, right, outermost teeth, scale = 20 µm.

Figure 34. Paradoris indecora. A, granulation on the dorsal notum, with pigments, syntype #4 of granulata, scale = 1.8 mm. B, grooved oral tentacle, holotype of indecora, scale = 0.5 mm. C, granulation on the dorsal notum, holotype of indecora, scale = 1.3 mm. D, nervous system, dorsal view, syntype #5 of granulata, scale = 1.8 mm.

Figure 35. Paradoris indecora, dorsal notum. A, syntype #3 of granulata, scale = 300 µm. B, syntype #3 of granulata, scale = 30 µm. C, holotype of ceneris, scale = 20 µm. D, holotype of ceneris, scale = 10 µm. E, holotype of inversa, scale = 100 µm. F, holotype of inversa, scale = 10 µm.

Figure 36. Paradoris indecora. A, syntype #4 of granulata, scale = 100 µm. B, one of the syntypes of granulata, scale = 30 µm.

Figure 37. Paradoris indecora. A, three jaw plates, one syntype of granulata, after Bergh (1884: plate LXXVI, fig. 11), scale = 2 mm. B, jaw rodlets with curved tips, holotype of indecora, after Bergh (1881: plate K, fig. 14), scale = 20 µm. C, distal part of the reproductive system with one ramified, accessory gland and one stylet sac, one syntype of granulata var., after Bergh (1884: plate LXXVI, fig. 32), scale = 0.5 mm. D, jaw rodlets with curved tips, one syntype of granulata, after Bergh (1884: plate LXXVI, fig. 12), scale = 25 µm. E, external, lateral view of a grooved lateral tooth, holotype of indecora, after Bergh (1881: plate K, fig. 16), scale = 60 µm.

Figure 38. Paradoris indecora, reproductive system. A, remaining pieces of the distal part, with two accessory glands and three stylet sacs (only two sacs visible on this side), syntype #5 of granulata, scale = 0.85 mm. B, remaining pieces of the distal part, with two accessory glands and three stylet sacs (only two sacs visible on this side), syntype #5 of granulata, scale = 0.85 mm. C, remaining pieces of the distal part, with one accessory gland and three stylet sacs, syntype #6 of granulata, scale = 0.6 mm. D, remaining pieces of the distal part, with one accessory gland and three stylet sacs (only two sacs visible on this side), syntype #6 of granulata, scale = 0.6 mm.

Figure 39. Paradoris indecora. A, remaining pieces of the reproductive system, holotype of ceneris, scale = 2.3 mm. B, prostate, holotype of ceneris, scale = 1.6 mm. C, nervous system, dorsal view, holotype of inversa, scale = 1.4 mm. D, remaining pieces of the reproductive system, holotype of inversa, scale = 2.4 mm.

Figure 40. Paradoris indecora, dorsal notum. A, MNHN-Ceuta, scale = 200 µm. B, MNHN-Ceuta, scale = 100 µm. C, MNHN-Ceuta, scale = 100 µm. D, MNCN, scale = 100 µm. E, MNCN, scale = 100 µm. F, ZMUC #2, scale = 100 µm. G, ZMUC #9, scale = 200 µm. H, MNHN-Sagres, scale = 100 µm. I, MNHN-Sagres, scale = 100 µm.

Figure 41. Paradoris indecora. A, dorsal view, ZMUC #1, scale = 2.7 mm. B, anterior, ventral view, ZMUC #1, scale = 2 mm. C, granulation of the dorsal notum, ZMUC #1, scale = 1 mm. D, part of the digestive system, ZMUC #2, scale = 1.15 mm.

Figure 42. Paradoris indecora, jaw rodlets. A, ZMUC #1, scale = 30 µm. B, ZMUC #1, scale = 10 µm. C, MNCN, scale = 10 µm. D, ZMUC #2, scale = 10 µm.

Figure 43. Paradoris indecora, radular teeth. A, left rows, ZMUC #1, scale = 30 µm. B, lateral teeth, ZMUC #1, scale = 10 µm. C, radular rows, ZMUC #6, scale = 30 µm. D, right rows, ZMUC #4, scale = 20 µm. E, left, outermost teeth, ZMUC #2, scale = 10 µm. F, right, outermost teeth, ZMUC #2, scale = 3 µm.

Figure 44. Paradoris indecora, reproductive system. A, remaining pieces, MNHN-Sagres, scale = 3 mm. B, distal part, with a hypothetical stylet sac, MNCN, scale = 0.6 mm. C, general view, ZMUC #1, scale = 0.6 mm. D, remaining pieces, MNHN-Ceuta, scale = 4.3 mm.