Distaplia stylifera

Distaplia stylifera (Kowalevsky, 1874)

(Figure 27 B)

Didemnum stylifera Kowalevsky 1874:43, Red Sea

Distaplia stylifera: Kott 1990: 127 fig. 46 pl. 9 f–g, and synonymy. Monniot F. & Monniot C. 2001: 258 fig. 119C. and synonymy, widely distributed

Stations. TA 52 (MNHN A3 DIS 104). TA 60 (MNHN A3 DIS 103).

Three colonies, one with a short peduncle and two others sessile, the largest 15mm in diameter, have kept their orange colour in formalin. The consistency of the tunic is spongy, the pigment is limited to the upper part of the colonies. The zooids form circular systems. They are small and contracted, colourless. The atrial languet is large and wide. The 4 rows of stigmata lack parastigmatic vessels. The gut loop is wide with a short stomach asymmetrical and longitudinally folded. A well marked annular widening takes place between the stomach and the intestine. The gonads hang below the abdomen (Fig. 27 B). The testis has 5 to 6 vesicles in a rosette; the sperm duct (Fig. 27 B) begins with a deep loop directed posteriorly to encircle the single oocyte before running upwards to the gut loop. No larvae are present in these small colonies.

The genus Distaplia as opposed to Sycozoa is defined as having parastigmatic vessels in the branchial sac and this is not the case here. Kott (1990) mentioned that the parastigmatic vessels are sometimes missing in D. stylifera which has a very constant anatomy around the world.

D. stylifera is recorded in many places in the Pacific and Atlantic oceans, in the Red Sea, but for the first time here in the western Indian Ocean.