Ritterella tokioka Kott, 1992

Monniot, Françoise, 2012, Some ascidians from the southern coast of Madagascar collected during the “ AtimoVatae ” survey, Zootaxa 3197, pp. 1-42 : 20

Ritterella tokioka Kott, 1992

( Figure 16 )

Ritterella tokioka Kott, 1992: 402 , Japan, nom. nov. for R. pedunculata Tokioka, 1953 . Monniot & Monniot 1997 (1999) and synonymy, Tanzania & Mozambique.

Stations. TA 23 (MNHN: A1 RIT 33)

Madagascar, Tulear, Vasseur col. 1969 (MNHN A1 RIT 29).

The colonies are sandy lobes arising from a common base ( Fig. 16 A). The widened head of the lobes is slightly transparent as the sand grains are less dense. The zooids correspond to the description and figures by Monniot & Monniot (1999). The branchial sac ( Fig. 16 B) counts 10 to 11 rows of stigmata with parastigmatic vessels incomplete or only present on some rows, according to the zooids. The stomach is always long with about 10 longitudinal folds. There is an annular post-stomach and a caecum at the base of the rectum. The ovary is placed very close to the gut loop followed by a series of testis vesicles limited to the anterior part of the post-abdomen. No larvae have been found. The zooids from the south of Madagascar remained yellow in formalin.

Remarks. The colonies of Madagascar are identified according to the description of the species given by Tokioka (1953) for the Japanese material. The geographic distance between the populations suggests a convergence more than a specific identity, the identification remains in absence of obvious anatomical differences.

Another Ritterella species: R. dispar ( Kott, 1957) is also recorded from Mozambique and Tanzania (Monniot & Monniot 1997–1999). It differs in having only 5 rows of stigmata.

Figures

FIGURE 16. Ritterella tokioka: A, parts of colony; B, branchial sac. Scale bar A = 1 cm.