Ascidia archaia Sluiter, 1890

Bonnet, Nadia Y. K. & Rocha, Rosana M., 2011, The family Ascidiidae Herdman (Tunicata: Ascidiacea) in Bocas del Toro, Panama. Description of six new species, Zootaxa 2864, pp. 1-33 : 3-4

Ascidia archaia Sluiter, 1890

( Fig. 1 )

Material examined. DZUP ASC 58—1 ind.; City; on polyethylene recruitment plate; 12/xi/2009.

Individuals are usually small, around 1.0 cm long, oval in outline. This species is uncommon with only one specimen collected in this study. Living individuals are slightly red because the completely transparent and colorless tunic allows one to see the red vessels that branch within the tunic as well as the red transverse vessels of the pharynx. The reddish color stays for at least one month after fixing in formalin. In live animals the transverse vessels have bright white spots along the ventral region; these spots disappear in animals fixed in formalin.

Characteristics agree with descriptions of animals from the Pacific ( Tokioka 1953; Nishikawa 1986; Kott 1985) and Atlantic Oceans ( Van Name 1945; Monniot 1983). We report some differences here. The oral siphon is almost sessile, while the atrial siphon is 2.0 mm long and midway or slightly farther along the dorsal margin. Both siphons have eight wide and short rounded red lobes between each of which is one red spot. Lobes do not have projections.

Body musculature is formed by few thin fibers that are oblique from the oral siphon to the middle of body. Muscles in the siphons form longitudinal bands.

Eighteen oral tentacles are in four sizes. A wide area separates the circle of oral tentacles from the prepharyngeal groove, which lacks papillae. The neural ganglion is close to the dorsal tubercle. The dorsal lamina is toothed. Long languets appear on the right side of the esophageal aperture.

The pharynx does not extend posteriorly to the stomach. The pharynx has 32 longitudinal vessels on the right side, 28 on the left, 63 transverse vessels and 4–6 stigmata per mesh. The primary papillae are short and rounded at the end and the secondary papillae are very small and triangular.

The stomach is yellow in fresh specimens, with 4–5 internal folds. The intestine has a similar cross section throughout and forms two open loops and the anus has two smooth lips, 5.0 mm from the circle of oral tentacles. We confirm that round papillae form a band on the side of the stomach facing the atrial cavity and ascending the loop of the intestine, as described by Monniot (1983). Each papillae is crowned by other diminutive round projections. Renal vesicles are visible only on the stomach wall facing the atrial cavity.

The elongate ovary is lobed and completely enclosed within the primary loop of the intestine in a more or less vertical position. The elongate follicles of the testis are sparsely scattered on the external margin of the intestinal loop. Both gonoducts open side by side just posterior to the aperture of the anus.

Remarks. One individual was found in this study, and the body musculature, reduced number of oral tentacles and the ovary allow confirmation of the identification as compared with other descriptions. Nonetheless, morphological variations can be observed: Kott (1985) commented on the presence of around 40 oral tentacles in animals from Australia, while Monniot (1983) described 30 tentacles in animals from Guadalupe and Tokioka (1953) found 15 tentacles in samples from Japan. The two latter descriptions also spoke of fewer stigmata per mesh (3–5). Ascidia corelloides (Van Name, 1924) (Atlantic species) and A. rhabdophora Sluiter, 1904 (Pacific species) were synonymized by Tokioka (1953) and both were synonymized to A. archaia ( Kott 1985) . One difference with the original description of A. rhabdophora is that Sluiter (1904) described calcareous spicules in the tunic, but these were not found in this or any other study. The sample we dissected had white spots along transverse vessels of the pharynx and tests with hydrochloric acid proved that they were not calcareous. Therefore the synonymy is valid and the calcareous spicules described by Sluiter for A. rhabdophora were probably only pigmentation.

Figures

FIGURE 1. Ascidia archaia Sluiter, 1890. A. Animal in the field. B. Right side of body (without tunic). C. Left side of body (without tunic). Scale bar: B, C = 0.5 cm. Credit of field picture: Arjan Gittenberger.