Molgula citrina Alder & Hancock, 1848

Monniot, Françoise, 2018, Ascidians collected during the Madibenthos expedition in Martinique 3. Stolidobranchia, Pyuridae and Molgulidae, Zootaxa 4459 (3), pp. 401-430 : 423-427

Molgula citrina Alder & Hancock, 1848

Fig. 24

Monniot C.: 1969 and synonymy; Lambert et al 2010.

Station AB 181 (MNHN S3 MOL A 442; slide S3. 880).

The single specimen 7mm in diameter has a thin tunic covered with sand. The body wall is thin with a musculature reduced to the siphons and short bundles radiating from each siphon ( Fig. 24A ). There are 6 large oral tentacles with small ramifications of first order. The dorsal tubercle opens to the right in a C. The branchial sac has 7 folds on each side ( Fig. 24B ). The formula on the right side is: E- 4-5-7-7-8-5-3- DL. The infundibula are divided at the top of the folds. The gut forms a long open loop ( Fig. 24A ). The short stomach is covered by a dark brown hepatic gland. The anus has 2 lips. The kidney is ovoid ( Fig. 24A ). The gonads ( Fig. 24A ), one on each side, are made of a central ovary encircled and partly covered with numerous testis vesicles. The left gonad ( Fig. 24C ) lies in the secondary gut loop and the right gonad is applied against the dorsal side of the kidney ( Fig. 24A ). The oviduct is long and wide ( Fig. 24C ). The ducts of groups of testis vesicles join in the centre of the ovary surface to make tubes protruding into the atrial cavity, one in the right gonad and 2 on the left gonad ( Fig. 24C ) in the Martinique specimen. Specimens from Sweden and the Channel have been re-examined in comparison; the samples from Roscoff, of a smaller size than arctic specimens, are the same as those from Madibenthos and their identification as M. citrina was ascertained by a genetic study (Shenkar & Swalla 2010).

M. citrina is recorded for the first time in the tropical western Atlantic. This species is widely distributed in the north-eastern and north-western Atlantic Ocean and in Arctic regions ( Van Name 1945, Monniot 1970). It has been also recently found in the Pacific Ocean ( Lambert et al. 2010) and can be considered as an invasive ascidian in the Caribbean region..

Figures

FIGURE 24. Molgula citrina. A, dissection, scale bar = 1mm; B, branchial sac; C, left gonad.