Aplidium antillense ( Gravier, 1955 )

Sanamyan, Karen & Gleason, Daniel F., 2009, Ascidians of the genus Aplidium collected on shallow hard-bottom reefs of coastal Georgia (Atlantic coast of N America, U. S. A.), Zootaxa 2066, pp. 50-58 : 51-52

Aplidium antillense ( Gravier, 1955)

( Figures 1 , 2)

Amaroucium antillense Gravier, 1955: 618 .

Aplidium antillense: Monniot, 1972: 953 ; 1983: 414.

Material examined: collected in 2004, at 31°23.815' N, 80°53.461' W, specimen #172 ( KBPIG 1/1236) and at 31°36.056' N, 80°47.431' W, specimen #190 ( KBPIG 2/1237); 2006, specimen #36 ( KBPIG 3/1378) and specimen #38 ( KBPIG 4/1379) both collected at 31°36.056' N, 80°47.431' W.

Previous records: Martinique ( Gravier, 1955), Guadeloupe ( Monniot, 1983) and Bermudas ( Monniot, 1972).

Description. Colony is a small low cushion with irregular margins (KBPIG 1/1236, Fig. 1 A) or a flat sheet up to 40x 35 mm in extent and 8–9 mm thick (KBPIG 2/1237, Fig. 1 B). Zooids are arranged in double rows separated by oval or irregular zooid-free spaces that are slightly elevated. The limits of each system and a common cloacal opening are not discernible. Fine sand grains are spread over the surface and present throughout the colony, but only occasionally abundant. Otherwise the test is colourless and transparent. Living specimens are described by collectors as having an "almost transparent tunic with visible orange zooids inside".

Most zooids are strongly contracted and have short posterior abdomens. Less contracted zooids are rarer and up to 7.5 mm in length, half of which consists of the posterior abdomen. A simple atrial languet arises from the upper rim of the small atrial opening. The branchial sac has either 12 (KBPIG 1/1236) or 11 or 12 (KBPIG 2/1237) rows of stigmata. A cylindrical stomach, located in the middle of the abdomen, has 12–14 high, strait unbroken folds. The ovary, containing one or two large ova, is in the middle of the posterior abdomen. The testis follicles are serially arranged in two rows just posterior to the ovary. The sperm duct is very thick in all zooids and sometimes fills almost the entire width of the anterior part of the posterior abdomen.

Up to five serially arranged embryos are in the atrial cavity of almost all zooids examined. The trunk of the tailed larva is 0.75 mm in length. Three or occasionally four adhesive organs alternate with wide, short median ampullae (which are sometimes absent) and bunches of epidermal vesicles branching off of them. A single arc of vesicles is on each side of the adhesive organs.

Remarks. The present specimens conform to those described by Monniot (1972, 1983). The larva illustrated by Monniot (1972, Fig.2 D) appears to be immature and groups of epidermal vesicles between the adhesive organs are not shown.

Figures

FIGURE 1. Aplidium antillense, colonies.