Corellidae

Monniot, Françoise, Dettai, Agnès, Eleaume, Marc, Cruaud, Corinne & Ameziane, Nadia, 2011, Antarctic Ascidians (Tunicata) of the French-Australian survey CEAMARC in Terre Adélie, Zootaxa 2817, pp. 1-54 : 24-27

Corellidae

Corella eumyota Traustedt, 1882 ( Figure 15 )

Traustedt, 1882: 17 pl. 4 figs 2, 3, pl. 5 figs 13, 14. Monniot et al. 2001:63. Sanamyan & Sanamyan 2002: 36. Turon 1988: 280 figs 5, 6. Lambert 2004: 239 figs 1,2. Primo & Vazquez 2007: 1796. Varela et al. 2007: 1.

Stations (events when several trawling operations per station): 16A-21-31-54A-59-65(318)-65(322).

The specimens measure between 2.5 and 7 cm long and have a thin transparent tunic. The oral siphon is terminal, the atrial aperture at 1/2 or 1/3 of the body length. The oral tentacles are long and numerous. The dorsal tubercle opens in a simple hole. The dorsal lamina is made of long languets. The branchial tissue with spiral stigmata extends beyond the digestive tract and presents complete longitudinal vessels ( Fig. 15 B). The body wall is extremely thin with weak siphonal sphincters and the body musculature limited to the left side, in irregularly crossed fibres ( Fig. 15 A). The gut lies on the right side in horizontal position ( Fig. 15 A). The anus has numerous lobes. The testis lobes cover the external side of the stomach; the ovary occupies the lumen of the gut loop.

One sequence for specimen P4 COR.A 56 (BOLD: ASCAN026-10). This sequence diverges by more than 10% from the other sequences deposited with the same identification in BOLD. These other sequences are mined from GenBank, and come from specimens from North-Western Europe. The closest sequence is not from the same species or genus, it is actually ASCAN028 ( Corynascidia suhmi ) with 93.75% similarity.

The species distribution is particularly large in both hemispheres, Antarctic and Arctic Oceans, from shallow depths to 1300 m ( Sanamyan & Sanamyan 2002), but also Chile, Southern Africa and European coastal waters from Spain to England ( Lambert 2004; Varela et al. 2007; Nagar et al. 2010; Collin et al. 20110). This uncommon distribution, and the wide molecular divergence, need to be confirmed with further molecular studies.

Corynascidia suhmi Herdman, 1882 ( Figure 16)

Herdman, 1882: 186. Monniot & Monniot, 1994: 22 fig. 2 B. Sanamyan & Sanamyan, 2002: 335 fig. 19 and synonymy. Sanmyan & Sanamyan, 2005: 2006 fig. 1.

Station: 5.

The largest of the four specimens collected in Terre Adélie is 19 cm in length. The real shape cannot be precisely determined, the body is very soft and its width progressively decreases to form a peduncle. The atrial aperture is terminal and the oral siphon on a side. The muscles of the siphons are relatively weak compared to the strong bundles of fibres running on each side of the dorsal line. The branchial sac is wide and stretched to a pouch into the peduncle. The branchial tissue ( Fig. 16) comprises 3 superposed plans. The basal one, on the external side of the sac, is the thicker, in a lamina pierced of round or oval perforations. Above lies the web of spiral stigmata enclosed in crisscrossed flat vessels constituting the filtering tissue. Internally, complete longitudinal vessels in thin bridges are sustained by erect papillae ( Fig.16). When contracted the branchial tissue take a honeycomb aspect, thicker than previous descriptions noted for this species. The stomach has a smooth wall. The rectum is attached to the dorsal lamina. The anus has pointed lobes. The testis vesicles overlap the whole intestinal loop. The ovary is linear inside the loop.

One sequence for specimen P4 COR.C 5Aa (BOLD: ASCAN028-10). See Corella eumyota for further details.

The CEAMARC specimens are attributed to C. suhmi considering the general body shape and the place of the siphons. The arrangement of the stigmata is the same as in all Corynascidia species but the tissue is thicker here which may be due to a shallower habitat at 210 m depth when other specimens are known down to 6000 m; C. suhmi is mostly abyssal in the Antarctic seas.

Figures

FIGURE 15. Corella eumyota. A, body musculature and gut from external side, scale bar = 1 cm; B, part of the branchial sac.