Ciona gelatinosa Bonnevie, 1896

Sanamyan, Karen & Sanamyan, Nadya, 2007, Poorly known Ascidiacea collected in the vicinity of the Commander Islands and East Kamchatka, NW Pacific, Zootaxa 1579 (1), pp. 55-68 : 58-60

Ciona gelatinosa Bonnevie, 1896

( Figure 2 )

Ciona gelatinosa Bonnevie, 1896: 3 . Not Monniot, 1969a: 1133.

Ciona intestinalis form gelatinosa: Van Name, 1945: 163 (synonymy).

Ciona intestinalis gelatinosa: Hoshino and Nishikawa, 1985: 68 .

Although this species is not recorded in the Pacific, it is described here to establish its separate identity and relationships to other Ciona species including C. pomponiae .

Material examined: Canada, Baffin Island , Frobisher Bay, 63°42.657'N, 68°35.335'W, muddy bottom, about 33 m, 23 September 2003 , one specimen. Collector T. Siferd. KBPIG 1127 /1. The collector noted the species to be fairly common at this location but that currents and bottom type may exclude it from depths less than about 25m.

Previous records: Arctic and North Atlantic ( Van Name 1945, Hoshino and Nishikawa 1985).

Description. According to the collector the living specimens are quite flexible and gelatinous with about 15–20 cm of the body above the substrate and another approximately 6–8cm below the surface anchoring the animal to the soft bottom. Although Van Name (1945, p.163) said that "there is no pedicel", the cylindrical body narrows posteriorly to a stalk which usually is not visible as it is below the surface of the sediment. Occasionally individuals are raised above the bottom on this narrow stalk (T. Siferd, pers. comm). Underwater photographs show that the stalk is bent in a right angle so that the body lies parallel to the bottom ( Fig. 2C ) and oriented along the water current. Both apertures are on well marked siphons at the anterior end of the body. The branchial siphon is the largest and is curved posteriorly so the aperture faces the water current.

A preserved specimen is about 20 cm long, with soft, thick and translucent test. Short thick branched rootlike processes are at the posterior end, otherwise the surface is smooth, without outgrowths. The whole length of the posterior abdominal extension is hollow and contains an extension of the body wall. The contracted body removed from the test is only 10 cm long. Seven longitudinal muscle bands are on each side of the body, four originating on the branchial siphon and three on the atrial. Adjacent bands sometimes fuse ( Fig. 2A ). They all reach the posterior end of the post-abdominal extension where they are wider and less crowded, although individual muscle fibers in the muscle band are thicker. Thin circular transverse muscle fibers form a continuous coat in the anterior contracted third of the specimen. These are less crowded in the middle of the body and are completely absent from the post-abdominal extension.

About 40 branchial tentacles are on a high muscular velum. A small dorsal tubercle has a C-shaped slit with the open interval to the right. The neural gland and ganglion form a compact, thick, almost spherical body protruding from the outside of the body wall between the siphons ( Fig. 2A ). The branchial sac is thick and resembles Ciona intestinalis , with numerous (more than 80) dorsal languets and about 40 internal longitudinal vessels on each side. These are not significantly raised on papillae but are close to the surface of the branchial sac. An endostylar appendix is absent and a pair of pharyngeo-epicardiac openings is close to the endostyle. The gut forms a horizontal loop behind the branchial sac. The short stomach has internal longitudinal plications but is not clearly differentiated from the intestine. The straight rectum ends in a lobed anus. The ovary is a compact pear-shaped mass in the gut loop and numerous small male follicles spread over the gut loop. Genital apertures are situated anterior to the anus. Numerous male papillae are on a swollen end of the male duct ( Fig. 2B ). There are no pigment spots around male papillae or on other parts of the body (including siphons of living specimens).

Remarks. The branchial sac of this species is robust, with crowded vessels and is closer to shallow-water C. intestinalis (Linnaeus, 1767) and C. savignyi Herdman, 1882 than to the deep-water C. pomponiae and C. mollis . The species is characterized by its large muscular post-abdominal extension of the body wall allowing easy identification. For many years it was regarded as a form or subspecies of C. intestinalis (see Hoshino and Nishikawa 1985: 68). However, unlike the latter species, its endostylar appendage is either very indistinct or is absent altogether as in the newly examined material; and living specimens have no pigment spots on either genital aperture or between the siphonal lobes. The whole habitus of living specimens with curved branchial siphon and long peduncle is quite different from C. intestinalis . Ciona intestinalis may occur on soft bottom but never develops a peduncle containing a post-abdominal extension of the body.

Figures

FIGURE 2. Ciona gelatinosa (KBPIG 1127/1). A, body removed from the test; B, rectum and genital papilla; C, position of the specimen on the sea floor (from a photo).