Palicoidea, Bouvier, 1898

GUINOT, DANIÈLE, TAVARES, MARCOS & CASTRO, PETER, 2013, Significance of the sexual openings and supplementary structures on the phylogeny of brachyuran crabs (Crustacea, Decapoda, Brachyura), with new nomina for higher-ranked podotreme taxa, Zootaxa 3665 (1), pp. 1-414 : 212-216

Affinities between Palicoidea , Retroplumoidea and Hexapodoidea

The affinities between Palicoidea ( Crossotonotidae and Palicidae ), Retroplumoidea , and Hexapodoidea , as well as with Dorippoidea ( Dorippidae and Ethusidae ), have been questioned, all of these groups having have been considered heterotremes or thoracotremes at one time or another. The extreme modifications of the last thoracic somite (somite 8) and the P5 have raised substantial difficulties in defining the heterotreme or thoracotreme nature of these families. Differences in the P5, combined with those concerning the body aspect (very flat in Retroplumoidea , somewhat flat in Palicoidea and Ethusidae , thick in Dorippidae , globular in Hexapodoidea ), could mask some of the similarities observed between the families.

The male gonopore is coxal in Dorippoidea , Palicoidea , Retroplumoidea , and Hexapodoidea , with a coxosternal condition in most of Dorippoidea and in all Palicoidea , which excludes any possible relationships with Thoracotremata. Their heterotreme condition is herein well established so that their affinities with other heterotreme families should be investigated (see Affinities between Dorippoidea and Hymenosomatoidea ).

The Dorippoidea , Palicidae, Retroplumoidea, and Hexapodoidea are the only extant heterotremes with posterior pereopods that are reduced and dorsally located (P4 and P 5 in Ethusidae and Dorippidae ; only P 5 in Palicidae and Retroplumoidea ) or reduced to a vestigial P5 coxa ( Hexapodoidea ). The retroplumid P5 is short, thin, plumose, and can be dorsally oriented. The palicid P5 is filiform, highly mobile, can be dorsally held, and ends in a curved, moveable dactylus, in contrast to the crossotonotid P5, which is not particularly reduced in size and is similar in shape and orientation to the P2–P4 (see Castro 2000: 445). The Dorippoidea , with reduced, mobile, and prehensile P4 and P5, was until now the only non-podotreme group with a well-known carrying behaviour ( Holthuis & Manning 1990; Guinot et al. 1995) (see Concealment behaviour: Carrying behaviour).

In describing Palicus caronii, Roux (1830 : leaf 46) pointed out its occurrence deep in the mud and assumed a carrying behaviour similar to that of Medorippe lanata , found in the same habitat. There are no published reports of carrying behaviour in Palicidae although it was not excluded that palicids may carry light organisms with their narrow P5 ( Castro 2000: 585). Such carrying behaviour among palicids has now been demonstrated by Y. Fujita (University of the Ryukyus, unpublished), who photographed several specimens of Exopalicus maculatus and Palicoides whitei performing carrying behaviour with the dactyli of their thin, raised P5, both in the field and in aquaria ( Fig. 54 ). That such small animals (rarely more than 20 mm in carapace width) can support with their delicate P5 objects that can be larger and heavier than themselves is remarkable. The Palicidae is the second nonpodotreme group in which carrying behaviour is observed, being reported here for the first time.

Retroplumids live in muddy substrates, where they bury at least temporarily, with only the anterior portion of the body exposed ( Saint Laurent 1989: 143). Their P5 were suspected to serve as floating organs ( Alcock 1902, 1906) or even as gills ( Tesch 1918a). Observations of live Retropluma quadrata by Saint Laurent (1989: 142) showed that individuals bury in mud, at least temporarily, leaving the body obliquely positioned with only the anterior part exposed. Observations of live retroplumids show a weak burying activity and no carrying behaviour, the P5 resting by the side of the carapace when crabs are on the substrate (P.K.L. Ng, pers. comm. 2012). McLay (2006a: 385) suggested that the retroplumid P5, supposedly sensorial in function, were “held above the mud surface rather than being buried”. The P5 dactyli of Retroplumoidea ( Fig. 44C ) are not subchelate, and carrying behaviour has never been recorded. It is unlikely that their fragile, setose P5, which, moreover, do not have the required mobility to carry even light objects. In contrast, the different disposition and mobility of the fragile P5 of Palicidae ( Fig. 44A ) and Latreilliidae ( Castro et al. 2003: 629) allow carrying objects for camouflaging (see Concealment behaviour: Carrying behaviour).

There is a morphological similarity, a long P5 ischium, between Palicidae and Retroplumoidea . In Palicidae the P5 basis-ischium is not short as in other Brachyura , being long in comparison to the usual condition of the P5 articles and the P2–P4 basis-ischia ( Fig. 44A ). The P5 ischium is fused with a short basis although the suture is visible, as normally in Brachyura . The P2–P4 ischia are short and fused to the basis as normal, but with a distinct suture. A similar pattern is present in Retroplumoidea , in which the P5 basis-ischium is unusually long in comparison to the P2–P4 basis-ischia and the typical P5 condition among the Eubrachyura ( Fig. 44C ; Saint Laurent 1989: fig. 9). The Crossotonotidae , in contrast to Palicidae , has a short P5 basis-ischium without a distinct suture (as on P2–P4) ( Fig. 44B ), a condition linked to a minimised modification of the P5.

The similarities between the reduced, slender P5, with all articles of similar width, and with a long ischium of Palicidae and Retroplumoidea can be interpreted as either the result of convergence or inherited from a close common ancestor. It should be noted that the reduced, slender, and thin P5 of some Cyclodorippidae independently show a similar lengthening of the ischium, following a short basis, e.g., Cyclodorippe bouvieri Rathbun, 1934 ( Rathbun 1934: pl. 1), Tymolus daviei ( Tavares 1997: 264, fig. 1B), Ketamia depressa ( Ihle 1916: fig. 71), K. handokoi Tavares, 1993 ( Tavares 1993a: fig. 17a).

Attempts to group together crabs with reduced and dorsal posterior legs date back to Latreille (1817: 24, 25), who referred to brachyurans with posterior “legs on the back” as “ Notopodes ” and established, in the family-series Brachyura , the section Notopoda (see also Latreille 1825a: 273, as a tribe; 1831: 329, 330, 354, as a tribe; Berthold 1827: 259). The Notopoda included Dromia , Dynomene Desmarest, 1823 , Homola , Ranina (podotremes), Palicus (as Cymopolia Roux, 1830 ), Dorippe and Ethusa (Eubrachyura) . Risso (1826: 31) used the nomen Notopodes or Notopoda for a taxon that included podotremes and non-podotremes. Guérin (1832a: 283, 285; 1835) included in Notopoda Palicus (as Cymopolia ), Dromia , Dynomene , Dorippe , and Ethusa , all with reduced, dorsal posterior pereopod(s), as well as Caphyra Guérin, 1832 , but excluded Homola and Ranina . Lucas (1840: 112, 114) recognised at a rank below the family Brachyura two groups of Notopoda: the “ Dromites ”, including the podotremes Dromia , Dynomene , Homola , Ranina , and the “ Dorippites ”, including the eubrachyurans Dorippe , Ethusa , and Palicus (as Cymopolia ). Dromia , Homola , and Dorippe were assigned to “Dorsipedata” by Haworth (1825: 106). The Notopoda of Claus (1868: 237) included Dromia but later ( Claus 1872: 507; 1876a: 556) four families: Porcellanidae , Lithodidae, Dromiadae (consisting of Dromia , Dynomene , but also of Homola , Latreillia , Corystoides , and Bellia ), and Dorippidae . The Notopoda of Neumann (1878: 29) included Dorippidae and Dromiadae , which consisted of Dromia and Homola . The Notopoda Latreille, 1817, must not be confused with Notopterygia Latreille, 1831 ( Latreille 1831: 368) established as a tribe within “ Macrouri ” and actually including exclusively the Raninoidea (See Monophyletic Podotremata; Appendix II; Van Bakel, Guinot, Artal, Fraaije & Jagt 2012).

In establishing the tribe “ Dorippiens ” within Oxystomata, H. Milne Edwards (1837a: 99, 151) called attention to both their broad thoracic sternum and dorsal insertion of the two last pereopods. Based on larval characters, Cano (1891b; see also 1893b) grouped Dorippe , Ethusa , and Palicus in the same family, the Dorippidae . As far as Hexapodidae is concerned, its palaeontological and stratigraphic records suggest that they “may have perhaps evolved from the Dorippoidea ” ( Glaessner & Secretan 1987: 10). Based on the foregut structures, Brösing et al. (2007) found some similarities between Retroplumoidea and Palicidae .

The close relationship between Dorippidae and Palicidae has been discussed several times (see above). The Retroplumidae was tentatively placed with Palicidae and Dorippidae within Dorippoidea ( Guinot 1978a: 214, table). The possible relationships of the Hexapodidae with the Retroplumidae and Palicidae were briefly mentioned by Guinot & Quenette (2005: 334).

The assertion of Brösing et al. (2007: 28) that the molecular studies of Schubart, Cuesta, Diesel & Felder (2000) and of Schubart, Neigel & Felder (2000) supported a “closer relationship of the Palicidae with the Thoracotremata” is erroneous. Schubart, Cuesta, Diesel & Felder (2000: 180, 181), using Palicidae (Palicus) as outgroup, only asserted that the family holds “a basal position with respect to the Thoracotremata”. Schubart, Neigel & Felder (2000a: 826) only referred to the status of Palicidae ( Crossotonotus and Palicus ) as “unresolved”. The diagnosis of Palicidae by Castro (2000: 444) as “male opening sternal; sperm ducts under sternal plates, penis soft, curved, free on inner side of coxae” was similarly misinterpreted by Brösing et al. (2007: 28; see also Brösing 2008: 281), who did not recognise the particular coxo-sternal condition of Palicidae and concluded to the thoracotreme nature of the family.

The study of the neglected characters of the foregut-ossicle system ( Brösing et al. 2007; Brösing 2008) led to the creation of a new taxon, Neobrachyura Brösing, Richters & Scholtz, 2007, which includes the entire Thoracotremata plus some heterotreme taxa, i.e., Palicidae , Pinnotheridae , Potamonautidae , and Retroplumidae ( Brösing et al. 2007: 23, figs. 1, 2; Brösing 2008: 281). Several propositions of these papers are untenable (see Monophyletic Podotremata), and in addition they are based on some misinterpretations (see above). The proposed classification “goes against almost every scheme that has been proposed, and contradicts a substantial body of adult and larval morphology, as well as DNA evidence” ( Ng, Guinot & Davie 2008: 8). There is no substantial diagnosis of Neobrachyura, a certainly puzzling diagnosis due to the families that were included, which renders the taxon clearly polyphyletic, a reason perhaps why Neobrachyura has not been used ever by carcinologists since its establishment, being only cited in a list of new taxa created since 1994 ( Fernández 2007: 372). Furthermore, the statement by Brösing (2008: 281) “for the Thoracotremata as originally proposed by Guinot (1977a, 1977b) ( Ocypodidae , Mictyridae , Gecarcinidae , and Grapsidae ) one may assume a monophyletic origin, supported by characters of gonopores in both sexes” implies a non-monophyly when the heterotreme taxa assigned to Neobrachyura are added.

The dorsal and modified last pair or last two pairs of pereopods in Dorippoidea , Retroplumoidea and Palicidae coexist(s) with an abdomen having the first two or three somites dorsally positioned. The first abdominal somite is often concealed under the carapace in the strongly specialised Hexapodoidea (De Angeli et al. 2010; Guinot et al. 2010).

In Hexapodidae, Palicoidea, and Retroplumoidea , all sutures 4/5–7/8 are incomplete. A median line is present in Palicoidea along sternites 5–7, i.e., sternal pattern 5 subpattern 5d, and corresponds to a raised median plate ( Figs. 32A, E , 45A , 53J ). Both median line and median plate are absent in Hexapodidae and Retroplumidae ( Fig. 45B ), both with sternal pattern 5, subpattern 5a (see Thoracic sternum; Evolution of the thoracic sternum in the Eubrachyura and its patterns). Sternite 4 shows in these three taxa a similar latero-anterior extension that does not reach the pterygostome but joins the branchiostegite, posterior to the chelipeds in Palicoidea and Retroplumoidea , but not in Hexapodoidea . In Dorippidae , on the contrary, sternite 3 is so extended and the thoracic sternum/pterygostome junction so considerable that the branchial openings become two independent, deep slits excavated into the pterygostome ( Fig. 42C ; Ihle 1916: fig. 45), a condition already appearing in the first juvenile crab ( Quintana 1987: figs. 3F, 8E, 15G). Such a sternum/pterygostome junction does not occur in Ethusidae ( Fig. 42A ). By comparison, there is a trend to a junction, which may be very developed, by the extended sternite 4 in Hymenosomatoidea ( Figs. 42B , 43C ).

The posterior part of the cephalothorax of Hexapodoidea ( Figs. 27 , 28 ), Palicoidea ( Fig. 32 ) and Retroplumoidea ( Fig. 34 ) is modifed (a modification not shared with the Dorippoidea ; see Position of the Dorippoidea within the Brachyura ; Affinities between Dorippoidea and Hymenosomatoidea ), which results in the following shared features:

(1) P5 strongly reduced, dorsal, markedly reentrant, with all articles present, with long basis-ischium ( Palicidae, Retroplumoidea ; Fig. 44A, C , respectively); only slightly reduced and reentrant, slightly dorsal, with all articles present, with short basis-ischium ( Crossotonotidae ; Fig. 44B ); vestigial, restricted to the coxa, and completely concealed under the abdomen (male Hexapodoidea ), or lost (female Hexapodoidea ; Fig. 27 ).

(2) Thoracic somite 8 strongly reduced in relation to somite 7 ( Palicoidea , Retroplumoidea ) or vestigial ( Hexapodoidea ).

(3) Sternite 8 markedly different from the large preceding sternites 5–7, obliquely oriented, perpendicular to preceding sternites ( Fig. 34 ; Retroplumoidea ), nearly aligned with preceding sternites ( Fig. 32 ; Palicoidea ), or vestigial ( Figs. 27 , 28 ; Hexapodoidea ); sternite 8 invaginated, showing as two narrow portions and largely concealed under the abdomen and affected by the complex interlocking mechanism between carapace and cephalothorax ( Palicoidea ); sternite 8 not exposed except for a very small portion visible between abdominal somites 1 and 2 ( Retroplumoidea ); sternite 8 mostly concealed under the carapace, only a small portion remaining exposed dorsally, or indistinct in dorsal view ( Hexapodoidea ).

(4) Pleurite 8 modified in both sexes, reduced, completely concealed and fused with sternite 8, without a recognisable suture between them ( Fig. 34 ; Retroplumoidea ), reduced ( Fig. 32 ; Palicoidea ), or completely lost ( Figs. 27 , 28 ; Hexapodoidea ). [For Doprippidae, with exposed pleurites, see Figs. 46A, B , 47A, B ].

These characters are not shared by any other groups of Eubrachyura. Some additional fundamental traits are shared by Palicoidea and Retroplumoidea : the presence of a marked pterygostomial lobe ( Palicidae , see Castro 2000: fig. 2A; Retroplumoidea , see Saint Laurent 1989: figs. 3, 4); a wide junction of the thoracic sternum (episternite 4) with the branchiostegite, posterior to the chelipeds ( Palicidae , Fig. 32A ; Retroplumoidea , see Fig. 5D ; Saint Laurent 1989: fig. 4) (not to be confused with the sternite 3/pterygostome junction anterior to the cheliped in the Dorippidae , Fig. 42C ). A sternum/pterygostome or sternum/branchiostegite junction does not characterise the Hexapodoidea , where a rather long anterolateral extension of sternite 4 may be present anterior to the cheliped without, however, joining the pterygostome ( Fig. 5A–C ; Manning & Holthuis 1981: fig. 33b; Manning 1982: fig. 1b; Guinot 2006: fig. 4A, B; De Angeli et al. 2010: figs. 4C, 5C, 7C; Guinot et al. 2010: figs. 2D, 4B, C). The Palicoidea ( Fig. 32A, E ), Retroplumoidea ( Fig. 5D ), and Hexapodoidea ( Fig. 5A–C ) share a wide thoracic sternum, with largely interrupted sutures 4/5–7/8 and a press-button for abdominal-locking mechanism that remains operational in mature females. See Axial skeleton; Thoracic sternum.

The axial skeleton of Palicoidea , Retroplumoidea and Hexapodoidea is regularly compartmentalised, with parallel, equidistant phragmae and similar narrow sella turcica. These taxa share a similar pattern of sternal sutures, pattern 5, but with a different median line subpattern: subpattern 5a ( Fig. 56G ), without neither a median line nor a median plate, as in Retroplumoidea ( Fig. 45B ) and Hexapodidae ; subpattern 5d, with a median line and median plate extending along sternites 5–7 in Palicoidea ( Figs. 45A , 56J ). In Retroplumoidea and Hexapodoidea the endosternites only reach the sides of the wide inflated median area formed by the sterno-abdominal cavity. In Palicidae the endosternites are medially attenuated, confined laterally for most part; the central portion is only marked by a raised longitudinal septum, the median plate, and posteriorly by the thin transversal sella turcica ( Figs. 45A , 56J ). A similar median line and its corresponding median plate characterise the Crossotonotidae .

In comparison, the Dorippoidea shows a particular configuration of the median plate, which makes possible observing its origin, initially an invagination of the sternal floor. A median line is absent in both sexes of Medorippe lanata , but the median plate is sexually dimorphic, males displaying a median plate that is dissimilar along sternites 5 – 7 and females being devoid of a typical median septum ( Figs. 46C , 47A, B ). See also Evolution of the axial skeleton in the Eubrachyura.

The Palicoidea and Retroplumoidea plesiomorphically share a well-developed pterygostomial lobe and a long abdomen that reaches sternite 3 in Palicoidea and the anterior half of sternite 4 in Retroplumoidea .

The Palicoidea (sensu Hartnoll 1968a: 296, fig. 14C; Guinot 1979a: 113, fig. 31, pl. 24, fig. 9; Castro 2000: 44; Guinot & Quenette 2005: 334) and to a greater extent the Hymenosomatoidea (see Richer de Forges 1976, 1977; Guinot 1979a: 111, pl. 24, fig. 10; Lucas 1980: 151; Guinot & Richer de Forges 1997: fig. 2D, F; Naruse, Ng & Guinot 2008; Naruse, Mendoza & Ng 2008: figs. 1a, 6a, 9a, table 1) are probably the only eubrachyuran groups, together with some other Majoidea , to show a marked anterior displacement of the vulvae in the fused median part of the thoracic sternum. The Inachoididae and Inachidae display a peculiar forward orientation of sternite 6 ( Fig. 48A, B , respectively; see Female sternal gonopores, or vulvae). This may be compared to the forward displacement of the spermathecae encountered in several taxa within the Podotremata, such as Dromiidae , some Cyclodorippoidea , and Raninoidea .

The two superfamilies Palicoidea and Retroplumoidea , which appear as deeply rooted clades, could be grouped together in a higher-ranked taxon within Eubrachyura, awaiting a new classification scheme. The incorporation of the highly modified Hexapodoidea in the same higher-ranked taxon deserves further investigation.

The fossil record reveals the difficulty to separate Retroplumoidea from the Palicoidea . Glaessner (1969: R531) considered † Archaeopus and † Retrocypoda as possible members of Palicidae : for instance, McLay (2006a: 387, table 3) included in the Palicidae all the species of † Archaeopus and several other retroplumids (see Fossil Retroplumidae ).

The affinities of the Retroplumoidea , Palicoidea , and Hexapodoidea with Dorippoidea are not evident. Dorippoids only partially show the modifications mentioned above and, in contrast, have both the P4 and P5 that are dorsal, highly mobile, and reduced. See Position of the Dorippoidea within the Brachyura below; Position of the Hymenosomatoidea within the Brachyura ; Affinities between Dorippoidea and Hymenosomatoidea .

Figures

FIGURE 5. Vulvae in Hexapodidae (A–C) and Retroplumidae (D). A,?Hexapus sexpes (Fabricius, 1798), 10.6 × 18.0 mm, Persian Gulf (MNHN-B10209). B, Hexapodidae sp., female 3.0 × 4.7 mm, Gabon (MNHN-B27907). C, Thaumastoplax anomalipes Miers, 1881, female 4.0 × 6.0 mm, Congo (R.O.C.) (MNHN-B27913). D, Bathypluma forficula Saint Laurent, 1989, female 12.0 × 14.0 mm, Indonesia, Makassar Strait (MNHN-B11229). p.b., press-button; v.c., sternal vulvar cover; 4–7, thoracic sternites 4–7; 5/6, thoracic sternal sutur 5/6. Scales bars: 5 mm (A, D), 2 mm (B, C).

FIGURE 27. Vestigial P5 coxa, penis, and organisation of posterior portion of cephalothorax in Hexapodidae. A, B, Hexaplax megalops Doflein, 1904, male 13.0 × 19.0 mm, Fiji (MNHN-B29154); C,?Hexapus sexpes (Fabricius, 1798), female 10.6 × 18.0 mm, Persian Gulf (MNHN-B10209): exposed, translucent apodeme prolonging into sclerotised P4 platelet (left). a, apodeme; a.p., apodemal platelet; c, coxo-sternal condyle; cx4, P4 coxa; cx5, vestigial coxa of P5; e7, episternite 7; p, penis; p4, pereopod 4; pl7, pleurite of thoracic somite 7; 7, thoracic sternite 7; 8, reduced thoracic sternite 8; 6/7, thoracic sternal suture 6/7. Scale bar: 5 mm (C).

FIGURE 28. Coxal condition in Hexapodidae. A, Paeduma cylindraceum (Bell, 1859), female, 9.4 × 14.4 mm, west coast of Mexico (USNM 170897): posterior view of cephalothorax, with carapace slightly displaced to expose pleurite of thoracic somite 7 (pleurite 7). B, C, Hexaplax megalops Doflein, 1904, male 12.0 × 17.0 mm, New Caledonia (MNHN-B19244): schematic representation of posterior part of body, abdomen removed. a1–a3, abdominal somites 1–3; c, P5 coxo-sternal condyle; cx4, P4 coxa; cx5, vestigial coxa of P5; e7, episternite 7; p, penis; pl7, pleurite of thoracic somite 7; s8, exposed, visible dorsally portion of thoracic sternite 8; 6–8, thoracic sternites 6–8; 6/7, thoracic sternal suture 6/7. Scale bar: 5 mm (A).

FIGURE 32. Coxo-sternal condition in Palicidae (A, B, E), Crossotonotidae (C, D), schematic representation. A, B, Palicus caronii (Roux, 1830), male 9.0 × 11.0 mm, Canary Is. (MNHN-B16335). A, thoracic sternum and abdomen in situ; B, detail of A. C, D, Crossotonotus spinipes (de Man, 1888), New Caledonia (MNHN-B26811): detail of sternites 7 and 8. C, male 36.0 × 44.0 mm; D, female 29.0 × 32.0 mm. E, Palicus zonatus (Rathbun, 1893), male 10.0 × 13.0 mm, Gulf of California (MNHN- B26745): ventral view, abdomen removed; invaginated sternite 8 has been partially cut to expose underlying penis (left). a1, abdominal somite 1; b, press-button; cx4, cx5, P4, P5 coxae; e3–e7, episternites 3–7; l, invagination line of sternite 8; m.l., median line; p, penis (schematically represented too thin, straight in A and B, correctly represented thick and at an angle in Fig. E); p5, pereopod 5; 6, 7, thoracic sternites 6, 7; 8, thoracic sternite 8 in the form of double plate. Scale bar: 3 mm (E).

FIGURE 34. Coxal condition in Retroplumidae, with penis emerging from extremity of P5 coxo-sternal condyle. Retropluma quadrata Saint Laurent, 1989, male 10.4 × 12.0 mm, Philippines (MNHN-B19535). A, ventral view; B, posteroventral view; C, D, schematic representations of A and B. c, coxo-sternal condyle; cp, carapace (indicated by dotted line in C); cx4, cx5, P4, P5 coxae; p, penis; p5, fifth pereopod; pl7, pleurite of thoracic somite 7; pl8, pleurite of thoracic somite 8 fused to sternite 8; 6–8, thoracic sternites 6–8; 5/6–7/8, thoracic sternal sutures 5/6–7/8.

FIGURE 42. Milne Edwards openings and cases of thoracic sternum/pterygostome junction. A, Ethusa magnipalmata Chen, 1993 (Dorippoidea Ethusidae), male 12.4 × 11.6 mm, holotype, Loyalty Is. (MNHN-B21524): no junction, “normal” Milne Edwards openings; B, Amarinus lacustris (Chilton, 1882) (Hymenosomatidae Odiomarinae), male 4.7 × 4.7 mm, New Zealand, Oratia stream (ZRC2010.0238): sternum/pterygostome junction, Milne Edwards opening sealed by largely exposed, falbelliform, whitish mxp3 coxa, and separated from the cheliped; C, Medorippe lanata (Linnaeus, 1767) (Dorippoidea Dorippidae), female 17.8 × 23 mm, Mediterranean Sea (MNHN, skeleton prepared by S. Secretan): Milne Edwards openings as pterygostomial slits; D, Coleusia signata (Paul'son, 1875) (Leucosioidea Leucosiidae), male 24 × 21 mm, Suez Canal (MNHN- B31894): large junction, absence of Milne Edwards openings; E, Ranina ranina (Linnaeus, 1758) (Raninoidea Raninidae), female 85.8 × 73.1 mm, Madagascar, Tulear (MNHN-B31983): large junction, absence of Milne Edwards openings. cm, mxp3 coxa; e, sternal extension; j, sternum/pterygostome junction; l, leucosiid abdominal-locking structure; m, Milne Edwards openings; p, sternal perforation; pt, pterygostome; p.b., press-button; s, dorippid Milne Edwards opening as pterygostomial slit; v, vulva with operculum; 3–6, thoracic sternites 3–6; 3/4, 4/5, thoracic sternal sutures 3/4, 4/5. Scale bars: 3 mm (C), 5 mm (D). (B, photograph by J.C. Mendoza).

FIGURE 43. Hymenosomatidae. A, B, Limnopilos naiyanetri Chuang & Ng, 1991, Thailand, observed in aquarium in Singapore: (A) crawling; B, male mating with an ovigerous female (photographs by R. Yeo, courtesy of P.K.L. Ng); C, Amarinus lacustris (Chilton, 1882), male 4.7 × 4.7 mm, New Zealand, Oratia stream: largely exposed, white, flabelliform coxae of mxp3 (ZRC2010.0238). Photographs by J.C. Mendoza.

FIGURE 44. P5 ischium, long in Palicidae (A) and Retroplumidae (C), short in Crossotonotidae (B). A, Palicoides longimanus (Miyake, 1936), female 14.7 × 17.0 mm, New Caledonia (MNHN-B26791); B, Crossotonotus spinipes (de Man, 1888), male 36.9 × 43.3 mm, New Caledonia (MNHN-B26803): penis emerging from P5 coxo-sternal condyle and pulled out from sternite 8 invagination; basis-ischium concealed under coxa. C, Retropluma quadrata Saint Laurent, 1989, with attached ciliates (after Saint Laurent 1989: fig. 9; unknown size). b, basis; c, coxo-sternal condyle; cx5, P5 coxa; i, ischium; p, penis; pa, papilla. Scale bars: 3 mm (A); 1 cm (B).

FIGURE 45. Skeletons with parallel endosternites and narrow sella turcica. A, Pseudopalicus declivis Castro, 2000 (Palicidae), male, New Caledonia (MNHN-B30492): medially attenuated endosternites, remaining lateral portions covered by pleurites; marked median plate; B, Bathypluma spinifer Saint Laurent, 1980 (Retroplumidae), male, Philippines (MNHN-B37017): cx5, P5 coxa; m, median plate; p, pleurite; P5, pereopod 5; s, sella turcica; s.c., convexity of sterno-abdominal cavity; t, endosternite.

FIGURE 46. Axial skeleton of Medorippe lanata (Linnaeus, 1767) (Dorippidae), male, Mediterranean Sea (MNHN). A, carapace (partially removed) covering all pleurites except exposed lateral portions of pleurites 5–7; B, detail of lateroposterior region of carapace to show exposed, calcified external portion of pleurites 5–7, with setting gutter for carapace; thick line indicates carapace border; C, skeleton with endosternites, median plate, and sella turcica. a1, first abdominal somite; b, sclerotised penial bulb; c, carapace edge; ce, ventral extension of carapace posterior edge; cp5, cp6, calcified portion of pleurites 5, 6 covered by carapace; cx2–cx5, coxae of P2–P5; c6, c7, coxo-pleural condyles of P3, P4; e, epimere (membrane); e6, extension of pleurite 6 covered by carapace; ep5–ep7, exposed pleurites 5–7; e4/5–e6/7, endopleurites 4/5–6/7; g, setting gutter of carapace; ga, gap between laminae of median plate; m, articulating membrane; m.p., median plate; P4–P8, pleurites 4–8; 8, exposed portion of sternite 8; s, sella turcica. Skeletons prepared by S. Secretan.

FIGURE 47. Skeletons of Dorippidae (A, B), Inachidae (C), Hymenosomatidae (D–F), and Inachoididae (G–I). A, B. Medorippe lanata (Linnaeus, 1767), Mediterranean Sea, dorsal view. A, male, after removal of carapace; B, female, after removal of pleurites; C, Inachus dorsettensis (Pennant, 1777), female, Mediterranean Sea (MNHN): sagittal section. D–F, Odiomaris pilosus (A. Milne-Edwards, 1873), New Caledonia (MNHN): D, dorsal view after partial removal of carapace; E, axial skeleton, dorsoventral view after removal of pleurites; F, axial skeleton, sagittal section. G, H, Paulita tuberculata (Lemos de Castro, 1949); G, male 23.0 × 23.0 mm, French Guiana (MNHN-B19511): exposed pleurites 5–8 visible after removal of carapace; H, female: axial skeleton, sagittal section. I, Leurocyclus tuberculosus (H. Milne Edwards & Lucas, 1842), Brazil (MNHN): sagittal section. a, abdomen with pleopods; a1, first abdominal somite; c, carapace; cx5, P5 coxa; e, endopleurite; e.p., exposed pleurite; e5–e8, exposed pleurites 5–8; g, setting gutter of carapace; h, hymenosomian rim; j, junction plate; m, median plate; p, pleurite; pi, pillar; pl, pleopod; s, sella turcica; st, thoracic sternum; t, endosternite; v, location of vulva; y, eye; 3/4–6/7, endosternites 3/4–6/7; 4–8, pleurites 4–8. C, F, H, I: skeletons prepared by S. Secretan.

FIGURE 48. Location of vulvae. A–C, anterior displacement: A, Anasimus latus Rathbun, 1894 (Inachoididae), female 18.4 × 14.0 mm, French Guiana (MNHN-B17807); B, Capartiella longipes (Capart, 1951) (Inachidae), ovig. female 9.4 × 8.1 mm, Nigeria (MNHN-B19602). C, Halicarcinus planatus (Fabricius, 1775) (Hymenosomatidae), female 14.0 × 19 mm, South Pacific, Campbell I. (MNHN-B25960) (schematic); D, Hiroia krempfi Fize & Serène, 1956 (Cryptochiridae), female, Palau: vulvae not widely separated and sternal suture 7/8 complete (schematic, modified from Kropp 1990: fig. 6c); E, Pseudohapalocarcinus ransoni (Fize & Serène, 1956) (Cryptochiridae), female, Guam: vulvae located apart on broad thoracic sternite 6 (schematic, modified from Kropp 1990: fig. 12c). j, sternum/pterygostome junction; m.l., median line; v, vulva; 3–8, thoracic sternites 3–8; 4/5–7/8, interrupted thoracic sternal sutures 4/5–7/8; w, sternal wall.

FIGURE 53. Carrying behaviour in Dromiidae (A, B), Homolidae (C, D), and Cyclodorippidae (E). A, B, Tumidodromia dormia (Linnaeus, 1763), Mayotte, carrying sponges; C, Homola orientalis Henderson 1888, French Polynesia, with the carried sponge (detached); D, Lamoha inflata (Guinot & Richer de Forges 1981), French Polynesia, carrying a sea anemone; E, Deilocerus planus (Rathbun, 1900) carrying piece of shell (see Wicksten 1982). A, B, photographs by J. Dumas; C, D, by J. Poupin; E, sketch by M. Wicksten.

FIGURE 54. Carrying behaviour among palicid crabs. A, Exopalicus maculatus (Edmondson, 1930) carrying a foraminiferan shell (Marginopora sp.): both P5 visible, with dactyli holding camouflaging shell. B, C, Palicoides whitei (Miers, 1884): B, carrying fragment of coral rubble: dactyli of both P5 only slightly visible; C, carrying small pebble: clearly visible right P5. A, B in situ, C in aquarium, Okinawa, Japan. Photographs by Y. Fujita.

FIGURE 56. Diagrammatic representation of patterns of thoracic sternal sutures 4/5–7/8 and modalities of median line (median plate not taken into account) in Eubrachyura. A, pattern 1: sutures 4/5–7/8 complete (uninterrupted), median line along sternites 5–8, may extend on sternite 4; B, pattern 2: only suture 4/5 interrupted, median line along sternites 6–8; C, pattern 3: sutures 4/5, 5/6 interrupted, median line along sternites 7, 8; D, pattern 4: sutures 4/5–6/7 interrupted, median line on sternite 8; E, generalised pattern 5: sutures 4/5–7/8 incomplete, median line variable among subpatterns a-f; F, pattern 6: sutures 4/5–7/8 interrupted, suture 6/7 complete, median line along sternites 7, 8; G, subpattern 5a: sutures 4/5–7/8 interrupted, median line absent; H, subpattern 5b: sutures 4/5–7/8 interrupted, median line along sternites 3–8; I, subpattern 5c: sutures 4/5–7/8 interrupted, median line along sternites 5–8, sometimes partially on sternite 4; J, subpattern 5d: sutures 4/5–7/8 interrupted, median line along sternites 5–7; K, subpattern 5e: sutures 4/5–7/8 interrupted, median line along sternites 7, 8; L, subpattern 5f: sutures 4/5–7/8 interrupted, median line on sternite 4. Each thoracic sternum with same width; all sutures represented parallel, equidistant, and similar. Some additional patterns are not figured.