Euthyonidiella huwi O’Loughlin, 2014

O’Loughlin, P. Mark, Mackenzie, Melanie, Paulay, Gustav & VandenSpiegel, Didier, 2014, Four new species and a new genus of Antarctic sea cucumbers with taxonomic reviews of Cladodactyla, Pseudocnus, Paracucumidae and Parathyonidium (Echinodermata: Holothuroidea: Dendrochirotida), Memoirs of Museum Victoria 72, pp. 31-61 : 34

Euthyonidiella huwi O’Loughlin sp. nov.

Zoobank LSID. http://zoobank.org:act:8DD8AA4E-E46C-4FDE-

8A14-F796CA2B0427

Figure 1

Material examined. Holotype. Western Antarctica, Shag Rock , 53º38'S 40º54'W, 206 m, BAS BIOPEARL I stn SR–EBS–4, 11 Apr 2006, NMV F168650 ( UF tissue sequence code MOL AF 816 ).

Paratypes. Type locality and date, NMV F189889 (3 small juveniles) ; NHMUK 2010.137 – 138 (2).

Other material (not Euthyonidiella huwi ). Euthyonidiella kyushuensis Heding and Panning, 1954 . NW Australia, 17º29'S 120º28'E, 184–187 m, RV Southern Surveyor, SS05/2007 stn 91, 20 Jun 2007, NMV F149748 (1) (UF tissue sequence code MOL AF 408).

Description. Body cylindrical, slightly pentagonal in transverse section, rounded anterior and posterior, up to 7 mm long (tentacles deeply withdrawn), up to 2 mm diameter; thin calcareous body wall with surface bristle of table spires; 20 dendritic tentacles, 5 pairs large, 5 pairs very small, latter probably in slightly inner ring; tube feet in irregular single to double radial series, some spread inter-radially; calcareous ring high, not segmented; anterior end of radial plates with deep division at muscle attachment and with lateral notch, posterior prolongations short, forked, not segmented (ring of 2 mm long paratype specimen lacking posterior prolongations); inter-radial plates with anterior taper, blunt posterior, lacking posterior prolongations; short stone canal with bean-shaped madreporite free in coelom; single tubular polian vesicle.

Body wall with abundant irregular tables: discs round to slightly oval, margins lobed around perforations, 2 large central perforations, frequently 6 (up to 14) additional perforations, perforations most numerous in smallest specimens, discs predominantly 70 µm long, up to 90 µm long; spires with 2 pillars up to 40 µm long, spinous distally, sometimes with connecting bridges distally, distal bridges sometimes with spines on mid-bridge. Tentacles with irregular thick elongate perforated plates, up to 88 µm long. Peri-anal body wall with abundant tables and internal thick knotted scale-like ossicles.

Colour (preserved). White.

COI DNA barcode of holotype: AATAAT- GATCGGGGGGTTTGGGAACTGATTAATCCCAC- TA ATGAT TGGAGCACCAGACATGGCT T T TCCC- CGAATGAAAAAAATGAGATTCTGACTAATCCCCCC- CTCATTTATTTTACTCTTAGCTTCAGCAAGAGTA- GAAAGAGGGGCAGGAACTGGTTGGACGGTATACC- CCCCTCTTTCAAGAAAAATAGCTCACGCAGGAG- GCTCAGTTGACTTAGCAATATTTTCCCTTCAC- CTAGCGGGAGCCTCATCAATTCTAGCTTC- TATAAAATTTATAACTACAATAATAAAAATGC- GAACCCCAGGGGTAAGTTTTGACCGACTATCC- CTATTTGTGTGGTCAGTATTTATTACAGC- CTTTCTTCTACTTCTGAGACTCCCAGTATTAGC- CGGGGCTATAACCATGTTACTAACTGATCGTAAT- ATTAATACAACGTTTTTTGACCCTGCGG- GAGGGGGTGATCCCATATTATTTCAACATCTATTCT- GATTCTTTGGTCATCCAGAAGTGTACATTCTAATCT- TACCAGGCTTCGGTATGATTTCCCATGTCATTGCT- CATTATAGAGGAAAGCAAGAACCCTTCGGATATT- TAGGTATGGTCTATGCAATGGTAGCCATAGGTATTT- TAGGATTTTTAGTTTGAGCCCAC

Distribution. Western Antarctica, Shag Rock , 54°S 41°W, 206 m.

Etymology. Named for Huw Griffiths (British Antarctic Survey), in appreciation of his role in the BAS BIOPEARL expeditions, his contribution to collecting the specimens studied here, and with gratitude for his gracious collaboration in Antarctic holothuroid research.

Remarks. Euthyonidiella huwi O’Loughlin sp. nov. is distinguished from the other species of Euthyonidiella by a combination of: predominantly radial occurrence of tube feet; table discs that sometimes have more than eight perforations; relatively short posterior prolongations on the radial plates of the calcareous ring. The provisionally determined specimen of Euthyonidiella kyushuensis from NW Australia and Euthyonidiella huwi from Antarctica are sister taxa among 19 sequenced sclerodactylids sensu lato based on CO1 sequences, although they are quite divergent from each other (K2P pairwise distance = 0.20). We observed that the calcareous ring of a 2 mm long juvenile of Euthyonidiella huwi lacked posterior prolongations. We recognize that the relatively short posterior prolongations in the 7 mm long holotype may represent ontogenetic change, as may the sometimes more numerous perforations in the table discs and predominantly ambulacral occurrence of the tube feet. We acknowledge the unsatisfactory element in describing a new species from a few small specimens that may represent developmental stages, but we judge that it is important to establish the occurrence of genus Euthyonidiella Heding and Panning in Antarctica.

Figures

Figure 1. Holotype of Euthyonidiella huwi O’Loughlin sp. nov. (NMV F168650). a, preserved holotype; b, photo of calcareous ring, single polian vesicle (lower right), madreporite and stone canal (upper right) (insert: drawing of radial (bottom) and inter-radial (top) plates of the calcareous ring); c, SEM images of ossicles from the tentacles; d, SEM images of table ossicles from mid-body wall (insert: drawing of one common form of variable table discs).