Aiptasiogeton hyalinus ( Delle Chiaje, 1822 )

Grajales, Alejandro & Rodríguez, Estefanía, 2014, Morphological revision of the genus Aiptasia and the family Aiptasiidae (Cnidaria, Actiniaria, Metridioidea), Zootaxa 3826 (1), pp. 55-100 : 75-80

Aiptasiogeton hyalinus ( Delle Chiaje, 1822)

( Figs. 11 –13, Table 4)

Actinia hyalina Delle Chiaje, 1822

Actinia pellucida Hollard, 1848

Non Actinia lacerata Dalyell, 1848

Paractis comata Andres, 1881

Aiptasia lacerata: Andres 1884 (part.) Solecnactinia erythrochila Fisher, 1874 Sagartia erythrochila Fisher, 1889

Aiptasiogeton comatus Schmidt, 1972 Aiptasiogeton pellucidus Manuel 1981 Non Aiptasiogeton comatus: Seaton 1985 Non Haliplanella lineata: Ramil 1987 Aiptasiogeton hyalinus: Ocaña & den Hartog 2002

Material examined. (See Appendix 1).

Description. External anatomy ( Fig. 11 ): Pedal disc to 5 mm diameter, wider than column in living specimens. Column elongate, not divisible into scapus and capitulum, 7–20 mm height and 10–15 mm diameter in preserved specimens. Cinclides in mid-column, few, scattered. Mesenterial insertions visible. Oral disc to 10 mm diameter in preserved specimens. Tentacles to 96, smooth, tapering toward tips; inner tentacles longer than outer ones, 3–5 mm and 1–3 mm length in preserved specimens, respectively; two innermost tentacles (corresponding to directive mesenteries) distinctly colored in live specimens ( Figs. 11 A, D).

Internal anatomy and microanatomy ( Fig. 12 ): Mesogleal marginal sphincter muscle diffuse, strong; fibers closer to gastrodermis ( Fig. 12 G). Mesenteries hexamerously arranged in five cycles (to 64 pairs). More mesenteries distally than proximally. First cycle and one pair of second cycle perfect; rest imperfect ( Figs. 12 A, B). Fifth cycle only present distally (not shown). All perfect mesenteries fertile, including directives. Two pairs of directives each associated with siphonoglyph. Gonochoric. Retractor muscles restricted to reniform. Parietobasilar muscles differentiated, weak; fibers on thick mesogleal processes ( Fig. 12 C). Longitudinal muscles of tentacles ectodermal ( Fig. 12 E). Strong longitudinal ectodermal muscles in distal column ( Fig. 12 F). Basilar muscles well differentiated, with fibers on short but thick mesogleal pennon ( Fig. 12 D). Acontia few, well developed.

Color ( Fig. 11 ): In living specimens, column translucent with longitudinal rows of orange spots distally. Oral disc reddish. Tentacles translucent greyish with tips reddish to pink; those two corresponding with endocoels of directives distinct, with white base ( Figs. 11 A, D). Preserved specimens uniform yellowish in color ( Fig. 11 C).

Cnidom: Spirocysts, basitrichs, microbasic b- mastigophores and p -amastigophores (Fig. 13). See Table 4 for size and distribution.

Geographic and bathymetric distribution. Aiptasiogeton hyalinus has been recorded in the western Mediterranean Sea, Atlantic coast of France and northern Spain, British Isles, Canary Islands, Atlantic coast of Morocco, Madeira, Azores, and Israel (reviewed in den Hartog & Ates 2011). In this study, we provide a new record from the southern Atlantic coast of Spain (see Appendix 1). Aiptasiogeton hyalinus is a shallow water species, found between 0– 7 m.

Taxonomic remarks. The name of this species has a relatively complex history. Delle Chiaje (1822) provided a drawing and then in 1823 described with few details Actinia hyalina . Hollard (1848) concisely described Aiptasiogeton hyalinus in his thesis as Ac. pellucida on the French Atlantic coast but he did not recognize that it was the same species as Ac. hyalina . Fisher (1889) provided an adequate description of the species but named it Sagartia erythrochila ( Fisher, 1874) because he thought it was different than Ac. pellucida . Andres (1881) FIGURE 13. Cnidae of Aiptasiogeton hyalinus . A, C, F, I, K, L, N, O) Microbasic p -amastigophores. B, D, G, J, M, P) Basitrichs. E) Microbasic b -mastigophore. H) Spirocyst.

described Paractis comata but then ( Andres 1884) placed it and Ac. pellucida under the name Aiptasia lacerata Dalyell, 1848 and identified these former species as varieties. Aiptasia lacerata planifrons and A. lacerata crucifrons , as corresponding to Aiptasiogeton hyalinus but the third variety, A. lacerata ungicolata , corresponded to Paractis comata (synonym of Sagartiogeton laceratus ( Dalyell, 1848) [ Tur 1989; Fautin 2013]). In addition, Andres (1884) synonymized Ac. hyalina with Aiptasia lacerata (although with some reservations) and then revised A. lacerata .

Schmidt (1972) described the genus Aiptasiogeton for this species, calling material from the Mediterranean Sea Aiptasiogeton comatus . Manuel (1979) used this name for specimens in the British Isles. However, Manuel (1981) later corrected the name of the species to A. pellucidus because Paractis comata was introduced by Andres (1881) to designate a species that today is considered as Sagartiogeton laceratus .

TABLE 4. Size ranges of the cnidae of Aiptasiogeton hyalinus . x, mean; SD, standard deviation; S, ratio of number of specimens in which each cnida was found to number of specimens examined; N, Total number of capsules measured; F, frequency; +++, very common; ++, common; +, rather common; Abbreviations: M, Microbasic.

According to den Hartog and Ates (2011), Aiptasiogeton hyalinus is the correct name for this species; they argued that the name pellucidus is probably not available because it was published in a thesis ( Hollard 1848, see Tubbs 2001). We agree with those authors in considering the description of Delle Chiaje (1825) diagnostic — although the date of publication of the description provided by den Hartog and Ates (2011) is incorrect and we correct it here to 1822 ( Fautin 2013). Thus, the name A. hyalinus precepts A. pellucidus .

There are slight differences among the cnida data provided by Schmidt (1972), by den Hartog and Ates (2011), and by this study. However, we consider most of these differences attributable to different interpretation of cnida categories (e.g. we consider one category of microbasic p -amastigophores in the filaments whereas den Hartog and Ates (2011) consider two, but the ranges of these nematocysts coincide), to low numbers of studied specimens (den Hartog and Ates (2011) only examined one specimen, and Schmidt (1972) and this work only examined two specimens) and the intraspecific variability among localities (Schmidt material was from the Mediterranean whereas den Hartog and Ates (2011) and ours are from the Atlantic coast of Spain). Our specimens and that of den Hartog and Ates (2011) show an additional smaller category of microbasic p -amastigophores (1) in the acontia rather than only one as described by Schmidt (1972).

Aiptasiogeton eruptaurantia was initially described from the Western Atlantic coast ( Field 1949). Carlgren (1952) examined additional material, added cnida data and corrected several observations made by Field (1949) (particularly the fertility of the first cycle of mesenteries and that “warts” described by Field were simply elevations corresponding with the cinclides). Carlgren (1952) placed A. eruptaurantia as an aberrant species within Aiptasia because it has microbasic p -amastigophores in the column and tentacles; however, this is the case for all the other members of Aiptasiidae . Schmidt (1972) noticed the similarities of A. eruptaurantia and the genus Aiptasiogeton . Aiptasiogeton eruptaurantia differs from A. hyalinus in the number of tentacles (170 vs. 96), cnidae (microbasic p -mastigophores from column, tentacles and acontia are slightly longer in A. eruptaurantia , see Carlgren 1952 and Table 4) and geographic distribution (western Atlantic vs. eastern Atlantic and western Mediterranean).

Carlgren (1938) described Aiptasia parva from South Africa, including an account of cnida size ranges but his description is incomplete. This species is described having accumulations of nematocysts in the column, up to 70 tentacles, cinclides in mid-column but not distinctly arranged, lower number of mesenteries in mid-column and only eight mesenteries were perfect proximally in two of the examined specimens, suggesting pedal laceration ( Carlgren 1938, pages 73–74, figs. 34, 35). In addition, Carlgren (1938) did not mention the presence of zooxanthellae. The lack of zooxanthellae, occurrence of pedal laceration, having only eight perfect mesenteries proximally, cinclides not distinctly arranged and the size range of the longer microbasic p -amastigophores in the acontia (up to 74 Μm in length) are features that correspond to Aiptasiogeton . We have examined the type material of A. parva and confirmed the presence (although in low frequency) of the diagnostic microbasic b -mastigophores of the column (11–15 Μm in length). Thus, we consider the appropriate name to be Aiptasiogeton parva and distinguish it from the other two species of the genus by the accumulations of nematocysts in the column and by geographic distribution (Indian Ocean vs. Atlantic Ocean).

Figures

FIGURE 11. External anatomy of Aiptasiogeton hyalinus. A) Oral view of living specimen; notice the distinct tentacles corresponding with directives. B) Lateral view of living specimen; notice spots. C) Lateral view of preserved specimen. D) Lateral view of living specimen. E) Oral view of living specimen undergoing pedal laceration. Scale bars: A – E, 10 mm.

FIGURE 12. Internal anatomy of Aiptasiogeton hyalinus. A) Cross section of the column at the level of the actinopharynx showing the cycles of mesenteries (indicated by roman numerals between pairs). B) Detail of fourth cycle of mesenteries (arrows). C) Detail of restricted retractor muscles. D) Detail of a longitudinal section of the proximal end showing the welldeveloped basilar muscles (arrows). E) Cross section through a tentacle showing the ectodermal longitudinal musculature; notice the absence of zooxanthellae in the gastrodermis. F) Cross section through distal column showing strong ectodermal longitudinal musculature. G) Longitudinal section of the distal column showing strong mesogleal marginal sphincter muscle. Abbreviations: ep, epidermis; ga, gastrodermis; me, mesoglea; s, siphonoglyph. Scale bars: A – G, 0.1 mm.