Phallusia nigra Savigny, 1816

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 : 29-31

Phallusia nigra Savigny, 1816

( Fig. 18 )

Material examined. DZUP PHA 14—1 ind.; STRI Bay; 0.5 m, on PVC recruitment plate; 20/x/2008; DZUP PHA 15—1 ind.; 0.5 m, mangrove roots; 17/ii/2009; DZUP PHA 27—1 ind.; City; on PVC recruitment plate; 12/ vii/2009. DZUP PHA 09—1 ind.; Solarte; 15/viii/2003. DZUP PHA 02—1 ind.; South Solarte; 06/viii/2003. DZUP PHA 03—3 ind.; Mangrove Inn; 07/viii/2003.

This species is very common on mangrove prop roots, on coral reefs and artificial substrates. The tunic is black, but young individuals may be gray. The atrial siphon is long and anterior, its aperture is very close to the oral aperture which is usually bent dorsally.

Since this is a well known species, this is a complementary description to Van Name's (1945). There are 8–12 lobes on the oral siphon and 8–10 on the atrial, with one red spot between each in living animals. These spots turn black with formalin fixation. The lobes are large, round, transparent with plain rim. There are conspicuous longitudinal muscles over a net of more transverse and oblique slender fibers covering the right side of the body, while on the left side the longitudinal fibers from both siphons extend till the intestinal loop. Fibers from the atrial siphon sometimes cover the secondary intestinal loop. Some oral tentacles are very wide and flat at their bases (around one third of them) while the others are short and slender. The prepharyngeal groove is double, the posterior membrane inflated, forming a V area surrounding the dorsal tubercle with a U or V-shaped aperture. The neural ganglion and gland are very close to the atrial siphon. The 9–26 accessory openings between the dorsal tubercle and the neural gland are underneath the dorsal lamina. The dorsal lamina is double from the dorsal tubercle to the neural ganglion, beyond which it forms a wide membrane with long languets on the margin formed by the ends of the transverse vessels. The lamina decreases in width along the esophageal aperture and it ends just after the end of the aperture. The extremities of transverse vessels form long languets on the right side of the esophageal aperture and posterior to the pharynx. The pharynx is very pleated, with 6–9 small oval stigmata per mesh. There are 50–90 longitudinal vessels on the right side of the pharynx and 40–80 on the left; instead of parallel, the longitudinal vessels are oblique to the dorsal lamina in the portion where it is double. The primary papillae are flat, wide and round at the tip with a lobe at the base; there are some intermediate papillae, similar to but smaller than the primary. The alimentary canal comprises a long esophagus, a folded large stomach, an intestine with closed primary and secondary loops without dilation and the anus with a multilobed margin. The renal accumulation vesicles are abundant and transparent spheres on the wall of the intestinal tract, on both the atrial and body faces. The cauliflower-shaped ovary is dark and ramified laying inside both intestinal loops. The testis follicles are very difficult to see underneath the renal vesicles in old large animals. Follicles spread on intestinal wall in both loops. Both gonoducts are attached to the rectum wall and open beside the anus.

Remarks. The species has an extensive geographical distribution in warm seas. In the western Atlantic the most northern locality is Bermuda ( Van Name 1945; Monniot 1972) while the southern geographical distribution limit is São Paulo, Brazil ( Rodrigues 1962).

Table 2. Tabular key for the identification of Caribbean Ascidiidae species

Figures

FIGURE 18. Phallusia nigra Savigny, 1816. A. Animal in the field. B. Right side of body (without tunic). C. Left side of body (without tunic). Scale bar: B, C = 1.0 cm.