Aplidium selenium, Rocha, Rosana Moreira Da, Gamba, Gustavo Antunes & Zanata, Thais Bastos, 2012

Rocha, Rosana Moreira Da, Gamba, Gustavo Antunes & Zanata, Thais Bastos, 2012, Aplidium (Ascidiacea, Polyclinidae) in central coast, Brazil, Zootaxa 3565, pp. 18-30 : 25-28

Aplidium selenium n. sp.

( Figures 5 , 6 E, F, 7B, C)

Etymology: Species name refers to the fact that the colony have rings around the oral siphons of the zooids, giving the impression of craters found on the surface of the moon.

Material examined: Holotype: MZSP 0 0 0 33, 1 colony, Quebramar Norte, Salvador, Bahia; 12°57'7"S, 38°31'2"W, 9 m, Col. R. M. Rocha, 11.12.2007. Paratypes: DZUP APL-11 1 colony, Quebramar Norte, Salvador, Bahia, 12°57'7"S, 38°31'2"W, 9 m, Col. R. M. Rocha, 01.08.1999; DZUP APL-12 2 colonies, Quebramar Norte, Salvador, Bahia, 12°57'7"S, 38°31'2"W, 9 m, Col. R. M. Rocha, 08.06.2004; DZUP APL-13 1 colony, Forte São Marcelo, Salvador, Bahia, 12°58'13"S, 38°31'03"W, 6 m, Col. R. M. Rocha, 01.08.1999; DZUP APL-14 1 colony, Naufrágio Germânia, Salvador, Bahia, 13°00'34"S, 38°31'59"W, 8 m, Col. R. M. Rocha, 10.12.2007; DZUP APL- 15 1 colony, Naufrágio Germânia, Salvador, Bahia, 13°00'34"S, 38°31'59"W, 8 m, Col. R. M. Rocha, 10.12.2007; DZUP APL-17 1 colony, Naufrágio Maraldi, Salvador, Bahia, 13°00'31"S, 38°32'02"W, 8 m, Col. R. M. Rocha, 10.12.2007; DZUP APL-18 1 colony, Naufrágio Maraldi, Salvador, Bahia, 13°00'31"S, 38°32'02"W, 8 m, Col. R. M. Rocha, 10.12.2007; DZUP APL-191 colony, Naufrágio Maraldi, Salvador, Bahia, 13°00'31"S, 38°32'02"W, 8 m, Col. R. M. Rocha, 10.12.2007; DZUP APL-20 1 colony, Boião da Barra, Salvador, Bahia; 13°00'31"S, 38°32'02"W, 8 m, Col. R. M. Rocha, 0 4.03.2012.

Diagnosis: white or grayish colonies with white rings around the oral siphons, pharynx with 9?11 rows of stigmata, 12–25 stigmata per half row, reddish structure on the base of the thorax, stomach with 22?30 longitudinal folds, arc-shaped structure that supports the 30 pairs of epidermal vesicles in the dorsal region of the larva.

Colony diameter 2.5–5.0 cm and 5–9 mm thick, cushion-shaped with rounded edges. Color varies from white to light gray, sometimes green due to superficial algae ( Fig. 6 E). The tunic has a soft consistency and smooth texture. The base of the colony may have sand, and polychaete tubes may also be found within the tunic. Systems are mostly elongated but can be circular and formed by 9?12 zooids ( Fig. 6 F). The cloacae are circular and variable in number.

Zooids are light yellow, transparent, perpendicular to the surface, with elongated thorax 1.3?2.5 mm long, abdomen 1? 2 mm long, and post-abdomen extends to the bottom of the colony, 6? 7 mm long. A horizontally elongated red structure with glandular appearance is in the base of the thorax and on each side ( Fig. 5 A, 7C). The oral siphon is short and the circular musculature forms a sphincter at the base, with six rounded and long lobes. The atrial languet is short, narrow, pointed, with longitudinal muscle fibers, in the upper rim of the atrial opening or anterior to that opening. The atrial opening is between the first and third rows of stigmata ( Fig. 5 A). The longitudinal musculature is thin and composed of 10?15 fibers that leave the base of the siphons until the end of the post-abdomen. The pharynx has 9?11 rows of stigmata, ranging between 12−25 stigmata per half row. There are 21 filiform oral tentacles of three sizes. The esophagus is short and narrow; the stomach is large, rounded and has 22?30 longitudinal folds which can be discontinuous. The duodenum is narrow, with half the length of the stomach, followed by a subsequent oval and curved post-stomach, placed at the intestinal loop. The intestine is wide and starts with wide and short rectal caeca. The anus has two or three lobes and opens at the level of the sixth or seventh row of stigmata ( Fig. 5 A). Gonads are in the posterior half of the post-abdomen ( Fig. 5 B, C). The ovaries may have a fertilized egg, and two to five oocytes ( Fig. 5 B). The testis has 18?27 pairs of ovoid follicles posterior to the ovary ( Fig. 5 C).

Larvae are yellowish, ovoid and the trunk is around 0.9 mm long. Ocellus and otolith are in the posterior region. Three rows of stigmata are visible in the pharynx, nine stigmata in the first row and 10 in the second and third rows. The three adhesive papillae have wide cups are far apart and are supported by long, thin stalks. The ectodermal vesicles are pyriform and arranged in about 30 pairs. In the dorsal region of the larva, an arc-shaped structure supports the vesicles. The tail is on the same level of the adhesive papillae and involves half or less of the larva ( Figs. 5 D, 7B). One or two larvae are incubated in the thorax.

Remarks. Of the Atlantic species, A. selenium may be confused with Aplidium accarense ( Millar, 1953) due to the shape and consistency of the preserved colony and very similar zooids. However, A. accarense has iridescent blue spots (only seen in live colonies), 10 pairs of testicular follicles and larvae have only 10 pairs of ectodermal ampullae. In the Pacific, Kott (1992) shows pictures of colonies very similar to A. selenium , with rings around the oral siphons, which she identified as A. multiplicatum Sluiter, 1909 . Monniot & Monniot (1996) reviewed the type of A. multiplicatum and described it as having the post-abdomen not continuous with the abdomen, short, with grouped testis follicles. Thus, the Brazilian material is clearly different from A. multiplicatum .

Figures

FIGURE 5. Aplidium selenium n. sp. A, zooid, thorax and abdomen. B, post-abdomen with ovary. C, post-abdomen with testicular follicles. D, larva. Scales: A, B, C: 1 mm, D: 0.5 mm.

FIGURE 6. A, Aplidium antillense at shipwreck Reliance, Salvador, Bahia. B, Aplidium elongatum below two colonies of Didemnum psammatodes (Sluiter, 1895), Island Pacotes, Vila Velha, Espírito Santo. C, Aplidium elongatum in cross section. D, Aplidium lobatum at Praia da Barra, Salvador, Bahia. E, F, Aplidium selenium at Quebramar norte, Salvador, Bahia.