Polycitorella peresi Plante & Vasseur, 1966

Monniot, Françoise, 2012, Some ascidians from the southern coast of Madagascar collected during the “ AtimoVatae ” survey, Zootaxa 3197, pp. 1-42 : 29-30

Polycitorella peresi Plante & Vasseur, 1966

( Figure 23 B,D)

Polycitorella peresi Plante & Vasseur, 1966 , Madagascar, Tulear.

Station. TA 52 (MNHN A3 POL.B 13). The colonies are thick hard cushions with a circular or undulated outline, sometimes divided into lobes. The largest colony is 10cm in length and 3cm in thickness. The top surface, without spicules, is glistening, opaque, black ( Fig. 23 B) or brown with patches of darker brown pigment spots in formalin. The oral apertures are not arranged in circular systems. The oral and atrial apertures of each individual are close to each other and slightly protruding at the colony surface, but the zooids are deeply withdrawn inside the colony. The zooids are encased in hollows of the tunic which contains densely packed spicules ( Fig. 23 D). Both siphons are tubular with 6 lobes. The thoracic musculature is continuous extending in 2 strong ribbons along the abdomen.The branchial sac has 12 or 13 rows of stigmata. At the base of the thorax, on each side and near the endostyle, a circular depression without spicules can be seen remembering the didemnid lateral organs. This structure, difficult to see without staining, is different from the protruding organs described in other Polycitorella , more related to a fold of the body wall. These cup-like spots are also present in some re-examined zooids of two other species of Polycitorella : P. coronaria and P. mariae . The stomach is smooth-walled followed by a narrow tube posteriorly enlarged. A constriction separates the posterior intestine. Numerous testis vesicles and a central ovary occupy the gut loop. No larvae have been found. The spicules ( Fig. 23 D) have an average size of 30 to 40µm, a few reach 55µm. All of them have the same shape in irregular rays with a blunt tip.

Remarks. Eight species of Polycitorella have been described. P. hospitiolum ( Savigny, 1816) and P. stellifera Monniot & Monniot, 2001 , both differ by few stigmata rows. P. setoensis Nishikawa, 1980 has disk-shaped spicules. P. coronaria Monniot F., 1988 has circular systems and up to 20 rows of stigmata. P. orientalis Kott, 1990 has no dark pigment, spicules of 25–35µm, 10 rows of stigmata and no circular systems. P. m a r i a e Michaelsen, 1924 from New Zealand lacks dark pigment, lacks circular systems and the spicules are smaller. P. pallida Millar, 1962 , with 16 stigmata rows, has no dark pigment.

The type specimen of P. p e re s i (MNHN A3 POL.B 11) consists in small pieces. The colour in life was said to be red. In formalin, the upper layer of the samples is soft and black, the columnar base is white and hard. The zooids are damaged, with about 13 rows of stigmata. The general aspect is the same as in Atimo Vatae samples and the spicules are the same in shape and size.

P. p e re s i is only known from Madagascar.

Figures

FIGURE 23. Polycitoralla graphicum n. sp.: A, colony in formalin; C, spicules. Polycitorella peresi: B, colony in formalin, D, spicules. Scale bars A = 1 cm; B = 2 cm, C, D = 10 µm.