Dissotrocha guyanensis, Rougier & Pourriot, 2006

Rougier, Claude & Pourriot, Roger, 2006, On some rare and new species of rotifers (Digononta, Bdelloida; Monogononta, Ploima and Flosculariaceae) in the Kaw River estuary (French Guiana), Zoosystema 28 (1), pp. 5-16 : 7-9

Dissotrocha guyanensis n. sp.

(Fig. 2)

TYPE LOCALITY. — Kaw River estuary ( French Guiana), mud flat station ( V).

TYPE MATERIAL. — Holotype: ♀ mounted on a slide ( MNHN AM 871 ); paratypes: 3 ♀♀ mounted on slides ( MNHN AM 875 ).

DIAGNOSIS. — Among the bdelloids, D. guyanensis n. sp. is easily distinguished due to the presence of four toes and three pairs of strong dorsal thorns. Two of the pairs are located at the end of the second pseudosegment of the trunk (the first one being more lateral), and the third is situated at the third pseudosegment of the trunk. The foot bears two acutely pointed, long spurs. The rami have three median big teeth with many minor teeth. MEASUREMENTS (in µm). — Total length 280-330, spur length 40-50. OCCURRENCE. — Encountered at the three stations of the Kaw River (Fig. 1), in the wet season, during the spring and neap tides, and in the dry season.

DESCRIPTION

The anterior part, especially the corona, is inconspicuous in the preserved state, except for the dorsal antenna, which is slightly protruding in lateral view. The trunk is composed of three pseudosegments. The second pseudosegment is the widest, and the third is the narrowest. The posterior part of the body bears three pairs of spines: the first pair is the biggest and appears dorso-laterally on the larger part of the second pseudosegment, pointing forward. The two others are on the second and the third segment, respectively, and both point backward.

DISCUSSION

The French Guianan form undoubtedly belongs to the genus Dissotrocha in view of its four toes, long spurs and viviparity ( Donner 1965). To date, two species with very long toes, D. aculeata (Ehrenberg, 1832) and D. hertzogi Hauer, 1939 , have been recognized as belonging to the genus.

Although D. aculeata shows great variability ( Berzins 1982a), the French Guianan taxon cannot be related to this group. Indeed, some of the characters appear more related to D. hertzogi , and particularly to D. hertzogi aculeata Koste, 1996 from S Africa. The foot of D. guyanensis n. sp. has five articles as in D. hertzogi (three in D. aculeata ), the third bearing two long spurs. Although not as long as those of D. hertzogi (40-50 µm versus 80- 90 µm), these spurs are likewise straight, equally wide from the base to the tip, and acutely pointed. The distal point is about 1/5 the length of the entire spur. This shape is very different from that of D. aculeata , which is curved with an enlarged basis. In addition, the number and position of the thorns are characteristic: the posterior part of the body only bears three pairs of spines, whereas in D. aculeata the spines are spread out all over the trunk.

These characters seem sufficient to distinguish a new species.

Family EPIPHANIDAE Bartos, 1959