Aplidium stellatum (Verrill, 1871)

Fortaleza, Maria Tarciana Vieira & Lotufo, Tito Monteiro Da Cruz, 2018, Polyclinidae (Ascidiacea: Aplousobranchia) from the Gulf of Mexico, collected during the “ Hourglass ” cruises (1965 - 1967), Zootaxa 4422 (4), pp. 519-536 : 528-529

Aplidium stellatum (Verrill, 1871)

( Figures 12, 13)

Amaroucium stellatum Verrill, 1871: 291 .

Aplidium stellatum Van Name, 1945: 34 (and synonymy). Sanamyan and Gleason, 2009: 52. Examined material: collected in 11/5/1967, 27°35’N, 082°50’W, 6.1 m, specimen # EJ-67-158.

Description: Colony large and rounded, cream colored when preserved, measuring 4.8 cm x 3.0 cm, attached by an area of around 3.5 cm. Tunic firm and devoid of incrustations. The zooids are positioned close to the colony surface, forming systems that are marked by depressions on the surface.

Zooids are yellowish with an average length of 10.29 mm (length range – thorax plus abdomen = 2.53–3.35 mm; post-abdomen = 2.0 5–9.91 mm). Tubular branchial siphon with six rounded lobes, 0.13–0.32 mm long. Atrial opening is small and slightly lobed, positioned between the second and fourth stigmata rows. Atrial languet is simple and short measuring up to 0.23 mm. Muscles are thin and inconspicuous with about 15 longitudinal bundles running in parallel along each side of the body. Pharynx with 13–15 rows of stigmata. It was not possible to count the number of slits per row. Esophagus elongated, connected to a stomach in the middle of the abdomen. Stomach also elongated or slightly flattened in the anterior and posterior extremities, with 12 irregular longitudinal folds. The size of the esophagus and the stomach together is equal to slightly more than half the abdomen length. Posterior stomach absent, and the rectal valve is in the intestinal loop. Anal opening at the level of the tenth stigmata row. Abdomen and post-abdomen not separated by a constriction. Gonads in the post-abdomen, ovary in central position and testicular follicles distributed specially in the distal portion in single or double rows. Each zooid with up to two developing embryos, located in the posterior portion of the thorax. Larvae measured up to 0.77 mm, three adhesive papillae with short peduncles, four small ampullae, and a tail wound ¾ way around the trunk.

Remarks. Several larvae brood were found in the thorax of Aplidium stellatum . This colony was sampled during May, a period Gotelli (1987) identified as the reproductive peak for the species in the Florida region. The original description of A. stellatum is very short; however, according to later descriptions, the pharynx may have 11–14 stigmata rows and 9–12 well-marked longitudinal folds in the stomach ( Van Name, 1921; Van Name, 1945; Sanamyan & Gleason, 2009). The gonads seem to be the major diagnostic feature of the species, all fully developed in the examined material. However, the presence of epidermal vesicles was not described in the larvae examined by Sanamyan and Gleason (2009).