Corynascidia suhmi Herdman, 1882

Maggioni, Tamara, Rimondino, Clara, Taverna, Anabela, Reyna, Paola, Lagger, Cristian, Alurralde, Gastón, Calcagno, Emilia & Tatián, Marcos, 2022, Abyssal ascidians (Chordata, Tunicata) from the Weddell Sea, Antarctica, including a new Styela species and stomach content identifications, Zootaxa 5093 (3), pp. 296-314 : 300-301

Corynascidia suhmi Herdman, 1882

Figure 3

Corynascidia suhmi Herdman 1882: 186 ; Sanamyan K. & Sanamyan N. 2002: 335, fig. 19 and synonymy; Sanamyan K. & Sanamyan N. 2005: 2006, fig. 1.

? Corella eumyota: Monniot F. et al. 2011: 24-26 , fig. 16.

? Corynascidia suhmi: Hartmeyer 1924: 19 (= Corynascidia hartmeyeri Monniot C. & Monniot F., 1994 ).

Material examined: 68°32’S, 20°24’W, station 9, 4930 m, 27 Feb 2005, one specimen.

Description. The body of the specimen measures 7.5 cm high and 2 cm wide. The peduncle measures 5 cm in length. Its diameter remains constant until half of its extension, where it widens slightly until reaching the base. The base of the peduncle does not have rests of sediment nor tunic projections, probably because it was anchored to hard substratum. The tunic is transparent, thin and completely free of epibionts and exogenous material. Its consistency is extremely feeble. Both apertures are on the same side of the animal. The oral aperture is located a short distance from the peduncle. The atrial aperture is located approximately half-distance between the peduncle and the posterior region ( Fig. 3A ). The oral tentacles are long and filiform. In total, there are 104 oral tentacles, of two alternate sizes, disposed in a circle. The pre-pharyngeal band is circular, with smooth borders. It is composed of two lamellae. With a short “V” it surrounds a “C”-shaped dorsal tubercle ( Fig. 3B ). The dorsal lamina is composed of triangular languets. Strong muscular bands run through the dorsal region, from the oral to the atrial aperture. They extend from the medial dorsal region until ⅓ of the body, ending abruptly. Thinner circular muscles are distributed around both apertures. Transverse rows of branchial spiral stigmata, each with two to three coils, extend along the body axis. There are approximately 49 transverse rows on the left side and 45 on the right side. Each stigmata is crossed by two to four thin radial vessels. T-shaped papillae arise from the transverse vessels, most commonly at the intersection between stigmata. Some also arise at a mid-distance from a stigma. In some regions of the branchial sac, these papillae give support to longitudinal vessels. When present, there are one or two longitudinal vessels per stigmata ( Fig. 3C ). In total, there are 73 longitudinal vessels on the right side of the branchial sac and 80 on the left side. The gut-loop is under the branchial sac, displaced to the right side of the body. The small barrel-shaped stomach has 20 longitudinal folds. The rectum runs parallel to the dorsal lamina and to the gonoducts, whose openings lie next to the anus. The anal border is smooth. Testis follicles and ovaries are distributed in the gut-loop, the former being spread over the proximal end of the former.

Stomach contents. No items were found in this specimen.

Remarks. This is the first record of Corynascidia suhmi in the Weddell Sea.

Based on the revision of specimens of Corynascidia suhmi from the southern hemisphere reported by Kott (1969) and Millar (1988) and the specimens from the North Atlantic reported by Hartmeyer (1924), Monniot C. & Monniot F. (1994) considered two different specific entities. The authors proposed for the northern populations a new species: Corynascidia hartmeyeri Monniot C. & Monniot F., 1994 . The characters that would differentiate C. hartmeyeri are: a plain dorsal lamina, less longitudinal vessels per spiral stigmata and a smooth-bordered anus. New material collected in the North Atlantic (Sanamyan K. & Sanamyan N. 2005) and in the SW Atlantic oceans (Sanamyan K. & Sanamyan N. 2002) allowed the latter authors to question the existence of C. hartmeyeri . They considered erroneous the observations about the dorsal lamina and the anal border performed by Monniot C. & Monniot F. (1994). We decided not to maintain C. hartmeyeri as a separate species nor to consider it a synonym of C. suhmi until the original material is reexamined or new evidence is found.

Sanamyan K. & Sanamyan N. (2005) suggested three characters to differentiate between Corynascidia suhmi populations from the northern and southern hemispheres. One of them, (the number of transverse vessels) is not considered, because it might be associated with animal growth. Our specimen possesses one of the characters signaled by these authors for the southern hemisphere populations (shape of the pre-pharyngeal band). The remaining character (number of longitudinal vessels or papillae), coincides partially with what has already been described for those populations. As signaled by Sanamyan K. & Sanamyan N. (2005), more samples are required to definitively confirm this hypothesis.

Based on molecular data, Monniot F. et al. (2011) found that specimens of Corella eumyota Traustedt, 1882 from Adelie Land, Antarctica, were in fact closer, with 93.75% similarity, to the specimens of Corynascidia suhmi from the same place than to any other sequence of specimens of the same genus ( Corella spp. ) or even species ( C. eumyota ). Alurralde et al. (2018) confirmed those findings with phylogenetic analysis. Although the finding of Monniot F. et al. (2011) might most probably be the result of an incorrect identification or mixed sequencing, it only stresses the need to reevaluate the taxonomic status of the genus Corynascidia , since it might be possible that the morphological differences observed are only a product of adaptations of Corella spp. to the deep-sea, as was stated by Van Name (1945).

Figures

FIGURE 3. Corynascidia suhmi. A: individual; B: pre-pharyngeal band around dorsal tubercle; C: branchial sac.