Aplidium elongatum, 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 : 21-23

Aplidium elongatum n. sp.

( Figures 3 , 6 B, C)

Etymology: Species name refers to the great length of zooid.

Material examined: Holotype: MZSP 0 0 0 31 1 colony, Ilha dos Pacotes, Vila Velha, Espírito Santo, 20°21'04" S, 40°15'12" W, 12 m, Col. R. M. Rocha, 13.2.2011. Paratypes: DZUP APL-21 1 colony, Ilha dos Pacotes, Vila Velha, Espírito Santo, 20°21'04”S, 40°15'5”W, 12 m, Col. R. M. Rocha, 13.02.2011; DZUP APL-23 1 colony, Ilha Escalvada, Guarapari, Espírito Santo, 20°42'00”S, 40°24'30”W, 8 m, Col. R. M. Rocha, 27.01.2012.

Diagnosis: Colony a half sphere, totally encrusted with sand, long oral siphon, zooid about 20 mm long, stomach with five longitudinal folds, ovary in the median region of the post-abdomen.

The colony may be up to 9 cm in diameter and 10–14 mm thick, with irregular outline. It is completely encrusted with sand, less densely so at the thorax level, although soft. When alive, it is opaque gray which in preservation becomes light-brown due to the color of the sand. The colony has many cloacae, but zooids are not organized in systems around them ( Fig. 6 B).

The zooids are about 20 mm long, vertical throughout the entire colony section ( Fig. 6 C). The thorax is elongated (about 4 mm) and narrow; the abdomen is approximately 3 mm long and the post-abdomen is 13 mm long. Zooids are transparent and the stomach is light brown. The oral siphon has six rounded lobes and the small circular atrial opening is smooth and between the second and third or third and fourth rows of stigmata ( Fig. 3 A). The atrial languet is simple, narrow, can be short or long, sometimes exceeding the length of the oral siphon; it projects from the level of the first row of stigmata or ahead of the cloacal aperture. The longitudinal musculature is very delicate, formed of 16−18 fibers in each side of the thorax and extends to the base of the post-abdomen.

The pharynx has 15−17 rows of stigmata, with 10–12 stigmata on each side in anterior and more central rows and 9−10 stigmata in subsequent rows. The stigmata of the ventral and dorsal regions of the pharynx are shorter than in the central region. The 21−23 oral tentacles of three sizes form a single circle. The esophagus is long and narrow. The stomach is large and elongate with five well-marked longitudinal folds, in the midline of the abdomen. The duodenum is narrow and half the length of the stomach. A constriction between the duodenum and the mid intestine is followed by an oval and curved post-stomach at the intestinal loop. The ascending intestine starts with rectal caeca; the anus is bilobed and opens at the base of the thorax, between the fourteenth and fifteenth rows of stigmata ( Fig. 3 A). In mature zooids, the ovary is in the median region of the post-abdomen, containing two to four small oocytes and one large fertilized egg ( Fig. 3 B). The testis has 7−16 ovoid follicles aligned or overlapping, posteriorly to the ovary ( Figure 3 C). Larvae were not found.

Remarks. Of the Atlantic species that have five folds in the stomach, four resemble our species. Aplidium pentatrema ( Monniot, 1972) has sand in the colony but it is lobed, the oral siphon has eight short lobes and the thorax has five rows of stigmata. Aplidium effrenatum ( Herdman, 1886) also forms a sandy encrusting dark colony, but zooids are short (~ 2.5 mm long) without an atrial languet ( Van Name 1945). Aplidium fuegiense (Cunningham, 1871) is a cold water species with variably shaped colonies, that may be small lobes or large encrusting cushions, sometimes elongated. Although with variable quantities of sand, colonies can be transparent or translucent and light colored zooids are seen from the surface. It has only 12 oral tentacles, the anus opens at the level of the eighth or ninth rows of stigmata, the ovary is immediately after the intestinal loop and there are more (25) testicular follicles ( Van Name 1945; Millar 1960). Zooids in Aplidium pantherinum ( Sluiter, 1898) are bright red or purple, giving the colony a red color, evident in the area surrounding the cloacal openings where the sand may be absent. The atrial opening is at the level of the fourth row of stigmata, the atrial languet is short and the ovary is immediately after the intestinal loop.

In the Pacific, some species also have 15−18 rows of stigmata and five folds in the stomach. Aplidium nadaense ( Nishikawa, 1980) has short zooids and 2 mm long thorax, about eight stigmata per half row and only 12 oral tentacles. In Aplidium globosum ( Herdman, 1886) sand is absent in the tunic, zooids are also short, the atrial languet projects from the rim of the atrial aperture and the anus opens in the midle of the thorax. Aplidium caelestis Monniot, 1987 with sand also absent, has the zooids aligned along the iridescent cloacal channels. Zooids are yellow or orange and the ovary is close to the intestinal loop. Aplidium nottii ( Brewin, 1951) has 7 mm long zooids and the pharynx has only seven stigmata per half row. Aplidium novaezealandiae Brewin, 1952 has zooids organized in polygnal systems with 10−12 zooids and the atrial aperture is bilobed with a three forked languet.

Figures

FIGURE 3. Aplidium elongatum n. sp. A, zooid, thorax and abdomen. B, zooid, post-abdomen. C, zooid, post-abdomen. Scales: 1 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.