Ascidia panamensis, 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 : 21-24

Ascidia panamensis sp. nov.

( Figs. 13–14 )

Material examined. Holotype: MZUSP 00021—1 ind.; Casa Blanca; 0.5 m, on PVC recruitment plates; 05/vii/ 2009.

Paratypes: DZUP ASC 97—1 ind.; Casa Blanca; 0.5 m, mangrove roots; 26/iii/2009. DZUP ASC 91—1 ind.; STRI dock; 1.0 m; 12/viii/2003; DZUP ASC 95—1 ind.; STRI dock; 1.0 m, on PVC recruitment plates; 03/viii/ 2008; DZUP ASC 98—1 ind.; STRI dock; 1.5 m; 10/iv/2009. DZUP ASC 96—1 ind.; Bastimentos island; 0.5 m, mangrove roots; 04/viii/2008; DZUP ASC 99—1 ind.; Bastimentos island; 0.5 m, on recruitment plates; 09/vii/ 2009. DZUP ASC 33—1 ind.; Solarte; 0.5 m, mangrove roots; 11/viii/2003; DZUP ASC 34—1 ind.; Solarte; 0.5 m, mangrove roots; 11/viii/2003; DZUP ASC 92—1 ind.; Solarte; mangrove roots; 15/viii/2006. DZUP ASC 94—4 ind.; Crawl Cay; coral reef; 25/viii/2006; MZUSP 00022—1 ind.; Crawl Cay; 14/vi/2009. DZUP ASC 32—1 ind; Pastores island; 0.5 m, coral reef; 10/viii/2003; DZUP ASC 93—7 ind.; Pastores island; coral reef; 17/viii/2006; MZUSP 0 0 0 23 —2 ind.; Pastores island; 13/vi/2009. DZUP ASC 90—1 ind.; Almirante Bay; 04/viii/2003.

Etymology. The name is in homage to the Republic of Panama, where the species was discovered.

Diagnosis. Thick and cartilaginous tunic with black or very dark and ramified vessels, especially around the siphons; in the field, the oral siphon usually has radial, short, white lines; musculature of the right side comprises a net of fibers in different directions; on the left side complete transverse fibers appear at the anterior region; oral tentacles united by a thick membrane; pharynx with 43–77 longitudinal vessels on the right side and 37–68 on the left; 5–7 stigmata per mesh; rectum forms a round sac; lobed ovary inside the primary intestinal loop.

Animals attach to the substrate on the left side of their body, usually without incrustations or epibionts. In coral reefs, only the large oral siphon is visible, with white stripes between the lobes; in mangrove roots, the small atrial siphon can be seen on the posterior region. The tunic is semi-transparent, gray or dark gray when alive, with numerous black vessels conspicuous mainly around the siphons. The tunic is cartilaginous, 0.2–3.0 mm thick, without projections. The body is elongated (2.6–7.0 cm long without the oral siphon; 0.9–2.9 cm wide); the body wall is opaque and brown with darker siphons. Siphons are 0.2–1.4 cm long, both have 10–16 lobes with smooth margins and a black spot between lobes; young individuals (up to 2.0 cm long) have eight lobes on the oral siphon and ten on the atrial.

On the right side, the body wall musculature comprises a net of strong fibers. On the left side of the body are complete transverse vessels close to the base of the oral siphon, longitudinal fibers from the oral siphon to the tip of the primary intestinal loop, and short fibers on the dorsal margin. Longitudinal muscles fibers in the siphons do not form bands.

The 41–115 oral tentacles are of three sizes, the longest 1.5–3.6 mm long. A thick membrane connects the tentacles. The double prepharyngeal groove has projections in the anterior lamina of some individuals; the area between it and the ring of tentacles is smooth, but it may have some small papillae. The peritubercular area is small and the dorsal tubercle aperture is U-shaped with or without curved ends. The neural ganglion is away from the dorsal tubercle, close to the atrial siphon. The dorsal lamina is double anteriorly, single and with toothed margin posteriorly (projections formed by the ends of the transverse vessels). The dorsal lamina passes by the left of the esophageal aperture to the end of the pharynx (2.5–14.0 mm beyond the stomach). There is a narrow lamina on the right of the esophageal aperture. The pharynx has 53–77 longitudinal vessels on the right side, 49–68 on the left, and 143–316 transverse vessels; it is very pleated, with 5–7 stigmata per mesh. The primary papillae in the pharynx are bilobed; secondary papillae and parastigmatic vessels are absent.

The alimentary canal occupies half or more of the left side of the body. The stomach is elongated, with 8–16 internal longitudinal folds. The intestine has primary and secondary loops; rectum has dilation forming a large pouch. The anus is located 9–38 mm from the oral tentacles and has a bilobed rim. Renal vesicles of 0.1–0.2 mm diameter cover the intestine and stomach.

The cauliflower-shaped ovary is restricted to the primary intestinal loop, more conspicuous externally; oocytes are 0.15 mm in diameter. The testis is ramified, with numerous follicles overlying the digestive tube. Both gonoducts open near, and just posterior, to the anal aperture.

Remarks. The gray tunic with dark vessels mostly around the siphons is very characteristic, in only one known Atlantic species: Ascidia interrupta . This species also has many lobes in the siphons, a net of muscle fibers on the right side of the body, a dilated rectum and a lobed ovary inside the primary intestinal loop. However, A. interrupta has a rigid tunic, with fewer vessels and with rounded projections on the surface. Moreover, A. interrupta does not have transverse musculature on the left side, has papillae overlying the area between the prepahryngeal groove and the ring of tentacles, papillae on the right face of the dorsal lamina (close to esophageal aperture), and trilobed papillae in the pharynx—characters never found in A. panamensis sp. nov.

From the Pacific Ocean, Kott (1985) redescribed Ascidia empheres Sluiter, 1895 with conspicuous dark vessels in the tunic after fixation, body musculature formed by a net on the right side of the body, a U-shaped dorsal tubercle and toothed dorsal lamina. Ascidia empheres differs from A. panamensis sp. nov. due to the reduced number of lobes in the siphons (7–8 in the oral and 6–7 in the atrial), papillae on the area between the prepahryngeal groove and the tentacles, eight stigmata per mesh, isodiametric intestine and ovary inside and outside of the primary intestinal loop ( Kott 1985). Another three Pacific species have vessels that are visible in the tunic, a net of muscle fibers on the right side of the body and toothed dorsal lamina: A. gemmata Sluiter, 1895 , A. ornata Monniot & Monniot, 2001 and A. glabra Hartmeyer, 1922 . However, A. gemmata has short muscle fibers on the left side of the body, few lobes on the siphons and isodiametric intestine ( Kott 1985), differing from A. panamensis sp. nov. Described recently, A. ornata differs from A. panamensis sp. nov. by the weak body musculature, fewer oral tentacles (about 30), the number of stigmata per mesh (6–10) and the stomach position (almost vertical) ( Monniot & Monniot 2001). Ascidia glabra is the most similar species to A. panamensis sp. nov., because they share the number of tentacles (60–100) and stigmata per mesh (4–8) ( Kott 1985; Monniot 1990). However, they differ in that A. glabra is yellow in life, has 9–12 lobes in the oral siphon and 6–8 lobes in the atrial, short longitudinal muscles on the left side of the body, papillae between the prepharyngeal groove and the ring of tentacles, trilobed papillae in the pharynx, and the ovary in both intestinal loops ( Kott 1985; Monniot 1990).

Figures

FIGURE 13. Ascidia panamensis sp. nov. 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.

FIGURE 14. Ascidia panamensis sp. nov. A. Black vessels in the tunic. B. Dorsal tubercle and anterior part of dorsal lamina. C. Right side of body (external), showing muscles. D. Left side of body (external), showing the gut and gonads. Scale bar: B = 1.0 mm; C, D = 1.0 cm.