Cystodytes

Monniot, Françoise, 2016, Ascidians (Tunicata) of the French Guiana Expedition, Zootaxa 4114 (3), pp. 201-245 : 209

Cystodytes sp.

Stations. CP4381; CP4383.

The small cushion shaped colonies collected from Guiana do not exceed 6mm in diameter, nevertheless larvae were present. The tunic is vitreous with some brown pigment but the colour fades in formalin. The zooids are enclosed in capsules of disk-like spicules with a thin regular edge. Abundant small spheres of needles are also present in the tunic. The zooids are very contracted and the branchial sac cannot be detailed. The testis vesicles in a flat rosette lie inside the gut loop. The larvae 0.9mm in length have 3 adhesive papillae in the center of an ectodermal ring. They are incubated in a swelling of the oesophageal area. There are not enough clearly observed characters to be able to assign these colonies a species name. Only C. dellechiajei ( Della Valle 1877) and C. drachii Herdman 1886 are recorded from the western Atlantic. C. violaceus Van Name 1902 from Bermuda is considered as a synonym of the former.

Eudistoma alvearium Oliveira et al. 2014 Figure 6 .

Stations. SR4; SR5; SR7; SR8; SS1; SS2; SS3; SS4; SS10; SS11; SS12; SC7; SC12; SC13; SD8.

In thick cushions with a flat upper surface and a narrow base the colonies contain abundant fecal pellets ( Fig. 6 A). They are variably pigmented in brown in formalin. The pigment is mainly present in the zooids, either at the top of the thorax or spread over the whole body wall. The zooids are up to 1cm long and parallel to each other located at the upper part of the colonies. The transverse and longitudinal musculature is dense. The oral tentacles arise from 2 to 3 rings. The first row of stigmata is curved dorsally. There are 3 rows of stigmata, 18 to 22 stigmata were counted in a medium half row. The pyloric gland comprises parallel longitudinal tubules becoming undulated by constriction ( Fig. 6 B). The stomach is very far in the abdomen followed by a short posterior intestinal loop ( Fig. 6 C) where are pressed numerous testis lobes and 2 to 3 oocytes. The larvae ( Fig. 6 D) are incubated at the base of the thorax. The trunk is 0.6mm long. The 3 adhesive papillae with thick peduncles are widely separated. Intercalated ampullae are not in pairs but flattened transversally; one is dorsal, one between the most dorsal papillae, 2 in the following interval and 1 ventral. Dark pigment remained at the base of the papillae ( Fig. 6 D). The figure of the type larva (Oliveira et al. Fig. 9 ) is the same as ours but the text description differs saying that the ampullae are in pairs, in our material they are medial, single and laterally flattened. All other anatomical traits correspond.

This is the second record of E. alvearium which was only known from one colony from Bahia collected on a wreck.

E. alvearium differs from E. vannamei ( Millar 1977) by the shape and colour of the colony but the larval structure is similar except a very different size.

Figures

FIGURE 6. Eudistoma alvearium. A: colonies; B, stained gut loop with pyloric gland; C, gonad, D, larvae one stained with hemalum. Scale bars: A = 2 cm; D = 0.3 mm.

FIGURE 9. Eudistoma vannamei. A, colony; B, stained thorax; C, larva not stained. Scale bars: B = 0.2 mm; C = 0.5 mm.