Limacia annulata, Vallès & Valdés & Ortea, 2000

Vallès, Yvonne, Valdés, Ángel & Ortea, Jesús, 2000, On the phanerobranch dorids of Angola (Mollusca, Nudibranchia): a crossroads of temperate and tropical species, Zoosystema 22 (1), pp. 15-31 : 20-22

Limacia annulata n. sp.

( Figs 4 ; 5 )

TYPE MATERIAL. — Holotype and one paratype ( MNHN).

MATERIAL EXAMINED. — Bengo Province. Praia São Tiago , 08°35’S, 13°21’E, 6.I.1985, 1 specimen 6 mm preserved length (holotype) ; 1 specimen 9 mm preserved length (paratype).

ETYMOLOGY. — We named this species annulata based on the distinctive red rings present near the apex of each lateral papilla.

DISTRIBUTION. — So far Limacia annulata has only been collected from Angola.

DESCRIPTION

The background body colour is opaque white in the living animal, with a few red spots dispersed over the whole dorsum. The mantle does not cover the foot and it can be seen on the sides and the posterior part of the body. The laterals of the dorsum bear 26 club-shaped papillae of different sizes on each side ( Fig. 4 ). All of them are white and have a large red ring near the apex, where a rounded opaque white body is arranged. Ventrally to the lateral papillae one tubular oral tentacle emerges at each side of the head of the animal. The rhinophores are retractile and have the same colour as the lateral papillae, but the red ring is open on the posterior side of the rhinophore. There are five white bipinnate branchial leaves that may have red spots.

The radular formula is 53 × (11.1.1.1.1.1.11) for the 9 mm specimen. The innermost lateral tooth is much thinner than the second lateral being also a little longer ( Fig. 5B ). The second lateral tooth has a small pointed denticle on the inner side and a basal irregular cusp on the outer side. Both lateral teeth have a hook-shaped form. The rachidi- an plate consists of a rudimentary, thin and long plate that goes all long the radula and contains many small papillations. There are 11 outer lateral teeth, which are approximately quadrangular in shape ( Fig. 5A ). All of them have almost the same size except for the innermost one, which is shorter, and the outermost one, which is thinner.

REMARKS

Limacia annulata n. sp. is different from all other species of the genus Limacia already described. Following Ortea et al. (1989), the European and African species Limacia clavigera seems to be the one that differs most from L. annulata . Both species have a white background colour and both of them have spots on the dorsum, lateral papillae, gill and rhinophores. However, L. annulata has no tubercles on the dorsum nor spherical yellow bodies on the apex of the dorsal papillae (as in L. clavigera ), but a red ring near the apex of the papillae and a spherical opaque white body on the apex itself (absent in L. clavigera ). The number of lateral papillae is much higher in L. annulata (26 on each side) than in L. clavigera (9-10 on each side), and the former has a red ring on the rhinophores absent in L. clavigera . One of the most conspicuous differences between these two species is the branchial leaves, which are three in number in L. clavigera and five in L. annulata . On the other hand, L. clavigera lacks a radular rachidian plate, which is present in L. annulata .

Limacia lucida (Stimpson, 1855) , described from South Africa, has an external morphology very close to L. clavigera , and it has been considered a junior synonym of the latter (Bergh 1907; Macnae 1958; Gosliner 1987a). Regardless, this species differs from L. annulata in having dorsal tubercles, and spherical red bodies in the apex of the lateral papillae as does L. clavigera .

Another species of the genus Limacia is Limacia janssi (Bertsch & Ferreira, 1974) , originally described from the Pacific coast of Central America. Limacia janssi has an orange background colour instead of white, as in L. annulata , and the colour of the spots is not red but orange. Both species have many lateral papillae, but L. janssi has two different forms of them (the largest ones being fewer in number than the smaller ones), whereas L. annulata has only one club-shaped papillar type. On the dorsum, L. janssi has many tubercles forming rows, a character that does not appear in L. annulata . The rhinophores of L. janssi are orange as the rest of the body, while they are white with a red ring in L. annulata .

Limacia cockerelli (MacFarland, 1905) , originally described from the Pacific coast of North America (MacFarland 1905), seems to be the most similar species to L. annulata . Both have a distinct rachidian plate of the radula (MacFarland 1966), white background colour and five bipinnate branchial leaves. Even if both species have numerous white lateral papillae, L. cockerelli has them in a much higher number, more than 60 on each side, whereas in L. annulata there are only 26 on each side. Also there is a red-orange body at the apex of the lateral papillae in L. cockerelli , while in L. annulata the apex is white. Limacia cockerelli , as well as L. janssi , differs from L. annulata by the presence of two different lateral papillae forms. In these two species the larger papillae are fewer in number than the thinner ones. The absence of tubercles on the dorsum of L. annulata is another difference with L. cockerelli .

Figures

FIG. 4. — Limacia annulata n. sp., paratype (MNHN), dorsal view of the living animal. Scale bar: 1 mm.

FIG. 5. — Limacia annulata n. sp., paratype (MNHN); A, radular teeth; B, detail of the rachis and lateral teeth morphology. Scale bars: A, 20 µm; B, 10 µm.