Euthyonidiella occidentalis ( Ludwig 1875 ) Ludwig, 1875

Martins, Luciana & Souto, Camilla, 2015, Taxonomic review of four western Atlantic dendrochirotids (Holothuroidea) with the description of a new Brazilian cucumariid species and designation of neotypes, Zootaxa 3919 (2), pp. 362-374 : 363-368

Euthyonidiella occidentalis ( Ludwig 1875) comb. nov.

( Figures 1–4 )

Thyonidium occidentale Ludwig 1875: 119 –120.

Euthyonidiella dentata Cherbonnier 1961: 611 –613, fig. 1. Thyone constituta — Sluiter 1910: 340, fig. F.

Phyllophorus occidentalis — Deichmann 1930: 148, pl. 18. Phyllophorus (Urodemella) occidentalis — Heding & Panning 1954: 164, fig. 76.

Type material. Neotype: designated herein, Itapuã beach, Salvador, BA, Brazil (12°57’ S; 38°21’ W): intertidal, 12 January 2014, 1 spm 8 cm long ( MZUSP 1139). [Holotype originally at the ZMB; type locality: Suriname, now lost (Dr. Carsten Lueter, pers. comm.)].

Other material examined. Panama, Caribbean Sea: 1973, 5 spms 2–5 cm long ( USNM E 22300 ). Itaparica Island, BA, Brazil (12°54’ S; 38°37’ W): 7 February 1993, 1 spm 3 cm long ( EQMN 1719). Itapuã beach, Salvador, BA, Brazil (12°57’ S; 38°21’ W): intertidal, 12 January 2014, 4 spms 3–5 cm long ( MZUSP 1067). Amaralina beach, Salvador, BA, Brazil (13°00’ S; 38°28’ W): intertidal, 8 April 2008, 3 spms 2–6 cm long ( UFBA 635); intertidal, 19 April 2011, 14 spms 2–10 cm long ( UFBA 1335); intertidal, 21 April 2011, 19 spms 1–5 cm long ( UFBA 1341); intertidal, 1 May 2011, 1 spm 5 cm long ( UFBA 1379). Porto Seguro, BA, Brazil (16°25’ W; 39°02’ S): 27 August 1980, 11 spms 2–5 cm long ( EQMN 607). Cumuruxatiba, BA, Brazil (17°56’ S; 39°12’ W): 14 October 1982, 2 spms 2.5 cm long ( UFPB 1876). Abrolhos, BA, Brazil (18°03’ S; 38°41’ W): 29 October 1997, 7 spms 1–5 cm long ( EQMN 1878); 31 May 1998, 1 spm 3.5 cm long ( EQMN 1879). Piloto beach, Vitória, ES, Brazil (19°49’ S; 40°02’ W): 28 January 1979, 1 spm 3 cm long ( EQMN 726); 20 July 1981, 3 spms 2–5 cm long ( EQMN 726). Armação beach, Búzios, RJ, Brazil (22°45’ S; 41°51’ W): May 1983, 1 spm 4 cm long ( EQMN 891). Ferradura beach, Búzios, RJ, Brazil (22°46’ S; 41°52’ W): 12 May 1999, 1 spm 4 cm long ( EQMN 1923).

Comparative material examined. Euthyonidiella dentata — holotype slides deposited in the MNHN (edentata dorsal hol 001; edentata dorsal hol 002; edentata dorsal hol 003; edentatatenthol 001; edentatatenthol 002; edentatatenthol 003; edentata ventral hol 001; edentata ventral hol 002; edentata ventral hol 003).

Neotype diagnosis. Body U-shaped; twenty tentacles distributed in two circles (10+10), the inner circle has smallest tentacles. Calcareous ring compact; radials with short and undivided posterior processes. Deposits in body wall are tables with two pillars low spire, and dentate margins; introvert with rosettes and tables; tentacles with rods and rosettes; tube feet with rods and endplate.

Neotype description. Body U-shaped ( Fig. 1 A, C, D). Tube feet scattered over entire body. 20 tentacles arranged in 2 circles (10+10): 5 large pairs in outer circle alternating with 5 small pairs in inner circle ( Fig. 1 E, F). Anal region bears five groups with three papillae each. Calcareous ring compact; radials with a deep anterior notch, and short and undivided posterior processes; interradials slightly shorter than the radials, with a broad base that overlap with the radials, and very short posterior bifurcation ( Figs. 1 B, 2). Two Polian vesicles 4 mm long ( Fig. 3 A, C), madreporite filamentous, stone canal 4.8 mm long ( Fig. 3 A, B). Deposits: body wall tables (40–60 Μm) with dentate margins, 4–8 perforations ( Fig. 4 A), and a reduced spire with two short pillars ending in four spines; introvert with rosettes (30–60 Μm) ( Fig. 4 B) and tables with several perforations ( Fig. 4 C, D); tentacles with rudimentary rods (35–75 Μm) (Fig. E) and rosettes ( Fig. 4 B); tube feet with rods ( Fig. 4 E) and endplate (150–300 Μm) ( Fig. 4 F). Body color light brown (in vivo and preserved specimen).

Distribution. U.S.A. (Florida), Caribbean Sea ( Antigua, Aruba, Barbados, Puerto Rico, Trinidad and Tobago), Suriname and Brazil (up to Rio de Janeiro); depth: intertidal region up to 2 m ( Hendler et al. 1995; present paper).

Biological notes. Specimens of E. occidentalis comb. nov. live burrowed in soft sediment, under rocks and associated with seagrass ( Hendler et al. 1995; present paper).

Genus change. We noticed that Euthyonidiella occidentalis comb. nov. was distinct from the members of the family Phyllophoridae by possessing a calcareous ring compact, which in turn characterizes the family Sclerodactylidae . Within this family, this species should be placed within the subfamily Cladolabinae , which is characterized by the presence of 15–20 tentacles (vs. 10 tentacles in Sclerodactylinae and Sclerothyoninae ); and within this subfamily, this species fits perfectly the diagnosis of the genus Euthyonidiella , by possessing 20 tentacles (vs. 15 in Clarkiella ), short spired tables in the body wall (vs. no tables in Afrocucumis ; and tall spired tables in Cladolabes ), and regular rods and plates (vs. thorny rods and spinuos plates in Ohshimella ).

Pawson & Miller (1992, p. 483) discussed inconsistencies regarding the tentacles’ arrangement and the morphology of the calcareous ring within the subgenus Urodemella ; nevertheless, they preferred to describe the species Phyllophorus (Urodemella) arenicola Pawson & Miller 1992 in this subgenus because of its similarity to E. occidentalis comb. nov. Therefore, we believe that P. (U.) arenicola should also be transferred to the genus Euthyonidiella , and be accepted as Euthyonidiella arenicola comb. nov.

A revision of the families Phyllophoridae and Sclerodactylidae is needed since the classification of these dendrochirotids was built on divergent opinions and an agreement has not yet been reached. Regarding the calcareous ring, there are clearly two extreme morphologies that define the family Phyllophoridae and the subfamily Sclerodactylinae: plates subdivided in a mosaic of pieces vs. plates compact (see Thandar 1989, fig. 1A, B). However, the calcareous ring of Phyllophorus (i.e. plates subdivided in large pieces) and of Sclerothyoninae (radial processes long and subdivided in small pieces), for instance, fall in between those two extremes.

Moreover, Heding & Panning (1954) described the subfamily Cladolabinae and divided it into two groups based on the presence of tables in the body wall and on the presence of subdivisions in the calcareous ring. Given the great amount of tables in the body wall of these taxa it would be probably hard to miss it; however, the radial processes of their calcareous ring are generally short and fragile, breaking easily when manipulated. For instance, some processes broke down into smaller pieces recalling subdivided posterior processes ( Fig. 2 A) when we removed the tentacles from the calcareous ring or after bleaching it. In addition, the subfamily Cladolabinae and the genus Phyllophorus possess an uncommon number and arrangement of tentacles (i.e. 10+10, 15+5, 15+5+5), distinguishing these taxa from the other dendrochirotids, which are mainly 10+0 and 8+2.

In this regard, phylogenetic studies based on morphological data could help to redefine the dendrochirotid clades by assessing phylogenetically informative traits. In addition, molecular data can provide a great set of characters in the absence of unambiguous morphological data, especially within the genera. However, regardless of the classification used, we believe the genus Euthyonidiella best fit both species (i.e. E. occidentalis comb. nov., and E. arenicola comb. nov.).

Euthyonidiella occidentalis and Euthyonidiella dentata . After analyzing slides of the holotype of E. dentata and its original description (in Cherbonnier 1961), we concluded that there is no difference between this species and E. occidentalis c omb. nov. Euthyonidiella dentata is known only from its holotype, collected in Bahia ( Brazil), and was never mentioned again, probably because the specimens collected were identified as “ P. (U.) occidentalis ”. Therefore, we suggest that E. dentata should be designated as a junior synonym of E. occidentalis comb. nov.

Comparison with other species. Considering the modifications proposed herein, ten species of Euthyonidiella are recorded: E. occidentalis comb. nov., E. aculeata ( Ludwig 1894) , E. trita ( Sluiter 1910) , E. destichata ( Deichmann 1930) , and E. arenicola comb. nov. [West Atlantic]; E. dubia Cherbonnier 1958 [East Atlantic]; E. tungshanensis ( Yang 1937) and E. kyushuensis Heding & Panning 1954 [West Pacific]; E. zacae ( Deichmann 1938) [East Pacific], and E. ambigua ( Heding 1942) [Mediterranean]. Euthyonidiella occidentalis comb. nov. differs from E. trita , E. ambigua , E. kyushuensis and E. dubia by the arrangement of the tentacles in two circles with ten tentacles each (vs. 15+5, 10+5+5, 14, 10+5+5, respectively), from E. aculeata , E. zacae , E. destichata , E. kyushuensis and E. dubia by the presence of tables with dentate margins (vs. oval or circular shape), from E. tungshanensis by the presence of tables with low spire (vs. high spire), and from E. arenicola comb. nov. by the morphology of the tables, which have pointy projections in their discs (vs. blunt projections) and pillars fusing together at the base (vs. pillars linked by a horizontal ridge).

Figures

FIGURE 1. Neotype of Euthyonidiella occidentalis comb. nov. (Ludwig 1875) (MZUSP 1139): (A) lateral view of body, and (B) calcareous ring. Additional specimens, in vivo, (UFBA 1379 A): (C) lateral view of body (on the left, notice calcareous ring visible across the translucent body wall); (D) specimen relaxed in the aquaria (in the bottom left, drawing of one tentacle); and (E) detail of expanded dendritic tentacles in lateral view; (UFBA 1335): (F) brownish dendritic tentacles (white arrow indicates inner circle of tentacles). Scale bars: A, 4 cm; B, 0.2 cm; C – D, 3 cm; E – F, 1 cm.

FIGURE 2. Euthyonidiella occidentalis comb. nov. (Ludwig 1875), (MZUSP 1067 A): (A – B) calcareous ring (white arrow indicates broken points on a posterior process); SEM images of (C) the calcareous ring stereom; (D) a radial plate, (E) the anterior view of a radial plate (white arrow indicates the insertion point of the retractor muscle), and (F) an interradial plate. Scale bars: A – B, 1 cm.

FIGURE 3. Euthyonidiella occidentalis comb. nov. (Ludwig 1875), (MZUSP 1067 A): (A) red arrow indicates insertion of stone canal, yellow arrow indicates the madreporite, and white arrows indicate the two Polian vesicles attached to the calcareous ring; (B) red arrow indicates the stone canal in detail and the yellow arrow indicated the madreporite; and (C) detail of Polian vesicles.

FIGURE 4. Neotype of Euthyonidiella occidentalis comb. nov. (Ludwig 1875), (MZUSP 1139): SEM images of the ossicles— (A) table from body wall; (B) rosettes from introvert and tentacles; (C – D) tables from introvert; (E) rods from tentacles and tube feet; and (F) endplate from tube feet. Scale bars: (A – E), 10 µm; (F), 50 µm.