Ascidia corallicola, Bonnet, Nadia Y. K. & Rocha, Rosana M., 2011

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 : 10-13

Ascidia corallicola sp. nov.

( Figs. 6–7 )

Material examined. Holotype: MZUSP 0 0 0 17 —1 ind.; Solarte; 07/vi/2009; 0.5 m; coral reef.

Paratypes: DZUP ASC 130—1 ind.; Casa Blanca; 05/vii/2009; 0.5 m, on polyethylene recruitment plate. DZUP ASC 128—1 ind.; STRI Bay; 06/vi/2009. DZUP ASC 125—1 ind.; Garden; 7.0 m, in death coral; 10/viii/2008; DZUP ASC 131—1 ind.; Garden; 7.0 m, coral reef; 23/xii/2008. DZUP ASC 127—1 ind.; Bastimentos island; 18/v/ 2009; 0.5 m, on polyethylene recruitment plate. MZUSP 00018—1 ind.; Solarte; 07/vi/2009; 0.5 m; coral reef. DZUP ASC 129—4 ind.; Pastores island; 13/vi/2009; 1.0–2.0 m, coral reef. DZUP ASC 126—1 ind.; Almirante Bay; 0.5 m, mangrove roots; 25/iii/2009.

Etymology. The name derives from the coral reefs in which it is most commonly found.

Diagnosis. Tunic thick and cartilaginous with red and slightly branching vessels, especially around the siphons; the transparent body wall is slightly orange on the siphons and on the dorsal margin of the body; musculature on the right side comprises a dense net of fibers in different directions, especially oblique and horizontal with few longitudinal fibers; oral tentacles slender and separated from each other; 49–56 longitudinal vessels on the right side and 40–53 on the left side of the pharynx; 7–12 stigmata per mesh; primary pharyngeal papillae may have lateral expansions; alimentary canal with a sac-like dilation; anus margin smooth; ovary cauliflower-shaped, inside the primary intestinal loop; testis follicles elongated and not very ramified.

The animals attach by the left and ventral side to coral, in a vertical position. The body is orange or slightly reddish especially the tips of the siphons. The tunic is smooth without incrustations, but it may have some triangular projections on the left side. Except for the reddish tint of the blood vessels, it is colorless and translucent. The tunic is also 1.0– 2.5 mm thick and firm, of cartilaginous consistency. The body is elongate, cylindrical, slightly flat on both sides, 6.3 cm long (including the oral siphon) and 1.6 cm wide, without the tunic. Siphons are short (around 0.3–1.2 cm), with conspicuous circular and longitudinal musculature with evenly spaced fibers. There are 8–9 triangular lobes on the oral siphon and 6–10 on the atrial, both with a red spot between the lobes and without projections on the margin. The atrial siphon projects slightly anterior to the midpoint of the dorsal margin.

The body wall is colorless, except for the orange siphons and dorsal margin. On the right side, the body wall musculature comprises a dense net of fibers mostly in oblique and horizontal directions. A few longitudinal fibers extend along the body till the posterior margin. On the left side, the ends of the longitudinal fibers from both siphons are found as are short perpendicular fibers along the dorsal margin of the body.

The 49–71 oral tentacles are of four sizes, the largest 1.8–3.1 mm long, slender and well spaced. The tentacles project from a conspicuous muscular ring. The prepharyngeal groove is double; the anterior membrane with projections. The space between the line of tentacles and the prepharyngeal groove is 0.4–1.3 mm wide in which are large papillae. The prepharyngeal groove forms a slight curve past the dorsal tubercle which is U-shaped, with or without enrolled ends. The neural ganglion is midway between the oral and atrial siphons, slightly away from the dorsal tubercle. The dorsal lamina is double anteriorly (along the first 20 rows of stigmata), with finger like projections formed by the ends of the left transverse vessels among which are smaller projections; may have projections on the wall close to the esophageal aperture. The dorsal lamina is uniformly wide throughout and passes the left side of the esophageal aperture to the end of the pharynx, which extends 2.5–6.9 mm past the stomach. The pharynx has 49–56 longitudinal vessels on the right, 40–53 on the left and 151–248 transverse vessels, is very pleated with meshes of 7–12 stigmata. The primary papillae are trilobed or simple; the secondary papillae and parastigmatic vessels are absent.

The alimentary canal is large, filling more than half of the left side of the body. The stomach is oval and wide, with 8–11 internal folds. The intestine forms two loops, the descending part of which is dilated and forms a sac-like pouch. The anus is 9.0–28.0 mm from the oral tentacles, is large and has a plain rim. The renal vesicles are 0.07– 0.15 mm in diameter, and cover the entire alimentary canal on its atrial side.

The ovary is cauliflower-shaped and fills the primary intestinal loop; it is visible both from the outside and the atrial cavity side. In recently fixed animals, oocytes are brown. The testis comprises long follicles, not very branched, spread out over the entire alimentary canal wall on the atrial side (except the rectum). From the outside the testis is visible only inside the primary intestinal loop. Both gonoducts are linked to the rectum wall and open just behind the anus. The oviducal aperture is a large slit, is more external while the sperm duct aperture is smaller and between the oviduct and the rectum.

Remarks. Similar to Ascidia interrupta , A. corallicola sp. nov. has body musculature formed by a net of fibers, trilobed papillae in the pharynx, area between the prepharyngeal groove and tentacles with many papillae, prepharyngeal groove with projections and ovary inside the primary intestinal loop. The orange to reddish color in life, the absence of round projections on the tunic surface and fewer lobes on the oral siphon allow identification of A. corallicola sp. nov. from A. interrupta . In the same region, A. monnioti sp. nov. is also found, and has a similar dilated rectum and shape and position of the ovary, but has a very rigid tunic, yellow color in life, muscles fibers that are mainly transverse on the right side of the body and many lobes on the siphons (10–16) all of which differ from A. corallicola sp. nov.

Ascidia gemmata Sluiter, 1895 , from the Pacific Ocean, is orange in life, body musculature formed by a net of fibers, large papillae overlying the area between the prepharyngeal groove and the ring of tentacles, 5–6 stigmata per mesh and the ovary is inside the primary intestinal loop ( Kott 1985). The round projections on the tunic, six lobes on the atrial siphon, smooth prepharyngeal groove, languets on the right side of the esophageal aperture, trilobed papillae in the pharynx and stomach with four internal folds are all characteristics that distinguish A. gemmata from A. corallicola sp. nov.

Figures

FIGURE 6. Ascidia corallicola sp. nov. A, B. Animal in the field. C. Right side of body (without tunic). D. Left side of body (without tunic). Scale bar: C, D = 1.0 cm.

FIGURE 7. Ascidia corallicola sp. nov. A. Right side of body (external), showing muscles. B. Dorsal tubercle and anterior part of dorsal lamina. C. Gut and gonads (internal). D. Left side of body (external), showing the gut and gonads. Scale bar: A, C, D = 0.5 cm; B = 1.0 mm.