Ascidia cf. gemmata Sluiter, 1895

Bonnet, Nadia Y. K., Rocha, Rosana M. & Carman, Mary R., 2013, Ascidiidae Herdman, 1882 (Tunicata: Ascidiacea) on the Pacific coast of Panama, Zootaxa 3691 (3), pp. 351-364 : 356-357

Ascidia cf. gemmata Sluiter, 1895

( Figs. 3–4 )

Material examined: DZUP ASC 193 – 1 ind.; Isla Canales de Afuera; 10.0 m, under rock; 13/i/2009; col.: R.M. Rocha. DZUP ASC 194 – 1 ind.; Shark Point; 6.0 m, under dead coral; 14/i/2009; col. R.M. Rocha.

The animals are up to 3.5 cm total length and attached to the substrate by the left side. The body is orange but color vibrancy is lost after fixation. It may have some epibionts (bryozoans and algae). The tunic is cartilaginous (0.6–1.8 mm thick), slightly wrinkled and translucent. There are small conical projections irregularly distributed on the surface of the animal, each one corresponding to the end of blood vessels.

Small individuals have an oblong body, 1.4–2.6 cm long (including the oral siphon) and 0.5–1.0 cm wide, without tunic. Both siphons are 0.3–0.5 cm long. The oral siphon has eight smooth lobes, while the atrial siphon has 6–8 smooth lobes and is 0.2–0.8 cm away from the tentacles. The nervous ganglion is close to the oral siphon.

A net of thin fibers (0.03–0.06 mm thick) forms the musculature on the right side. On the left side, the longitudinal muscles extending from the oral siphon are short and there is a band of short parallel transverse fibers on the dorsal margin. The longitudinal fibers in the siphons are not organized in bands.

There are 58–69 oral tentacles, of four sizes; the largest is 2.0– 2.5 mm long. They project from a thick muscular ring. The prepharyngeal groove is double and the anterior membrane has projections. The distance between the line of tentacles and the prepharyngeal groove is short (up to 0.3–0.6 mm), with some papillae. The peritubercular area is small and the dorsal tubercle aperture is C or U-shaped with enrolled ends. The smooth dorsal lamina is double anteriorly and without any projections on the right side close to the esophageal aperture. The dorsal lamina passes by the esophageal aperture on its left to the end of the pharynx, which extends 1.8–5.2 mm beyond the stomach. There is a narrow lamina with smooth margin on the right of the esophageal aperture. The pharynx has 39–43 longitudinal vessels on the right side, 33–41 vessels on the left and 62–74 transverse vessels; it is very pleated and meshes have 6–8 stigmata. The primary papillae are simple or slightly trilobed and no intermediate papillae or parastigmatic vessels were found.

The alimentary canal is not large, occupying approximately half of the left side of the body. The stomach is globular, with 7–9 internal folds. The intestine is isodiametric and form two loops. The anus is 3.8–5.9 mm distance from the oral tentacles; it has a bilobed rim. The renal vesicles are 0.12–0.16 mm in diameter, and cover the alimentary canal on its atrial side. There are conspicuous conic projections on the peritoneum that cover the alimentary canal.

The cauliflower-shaped ovary lays within both the primary and secondary loops of the intestine; it is visible in the primary loop from the outside and atrial cavity, but in the second loop it is observed only from the inside. Oocytes are 0.12–0.14 mm in diameter. The testis is ramified and spread on the intestine wall. Gonoducts open close to the anus aperture.

Remarks. Specimens are provisionally identified as Ascidia gemmata because of their general resemblance to most of the descriptions of the color, size, right side musculature, shape and position of the ovary, and network of blood vessels inside the tunic which form small papillae on the surface of the tunic.

Nonetheless, there is some incongruence among descriptions of A. gemmata . For example, it is possible to find 3–6 stigmata per mesh in the pharynx (Tokioka 1961; Nishikawa 1991) and up to 8–12 stigmata per mesh (Monniot & Monniot 2001); the intestine may be isodiametric (Tokioka 1961; Monniot 1991) or with a dilatation in the posterior region (Tokioka 1950; Monniot & Monniot 2001); the dorsal tubercle is usually U-shaped, but it may be meandric or subdivided in many slits (Tokioka 1950; Nishikawa 1991); and the number of oral tentacles may vary between 35–60 in specimens from Palao Is. and New Caledonia (Tokioka 1950; Monniot 1991; Monniot & Monniot 2001), 80 in specimens from Japan (Nishikawa 1991) and approximately 100 in specimens collected from Australia (Kott 1985). Therefore we agree with the suggestion of Monniot and Monniot (2001) about the presence of more than one species in the available descriptions of A. gemmata and the necessity of a detailed revision of the group. If confirmed, this record is the first one of this species on the Central American Pacific coast.

Figures

FIGURE 3. Ascidia cf. gemmata. A. Right side of body (without tunic). B. Left side of body (without tunic). Scale bar: A, B = 0.5 cm.

FIGURE 4. Ascidia cf. gemmata. A. Right side of body (external), showing muscles. B. Left side of body (external), showing gut and gonads. C. Dorsal tubercle and anterior part of dorsal lamina. D. Gut and gonads (internal). Scale bar: A, B = 0.5 cm; C, D = 1.0 mm.