Lurus evelinae Marcus, 1950

Steenkiste, Niels Van, Volonterio, Odile, Schockaert, Ernest & Artois, Tom, 2008, Marine Rhabdocoela (Platyhelminthes, Rhabditophora) from Uruguay, with the description of eight new species and two new genera, Zootaxa 1914, pp. 1-33 : 22-23

Lurus evelinae Marcus, 1950

( Figs. 9 A–9B)

New locality. Playa del Barco, Parque Nacional de Santa Teresa, Departamento de Rocha, Uruguay (33°59’52.12”S, 53°32’6.51”W). Coarse-grained sand just in between the dunes and the water line, up to 30 cm deep (16/07/2004).

Playa Grande, Parque Nacional de Santa Teresa, Departamento de Rocha, Uruguay (34°1’55.17”S, 53°32’10.86”W). Between filiform, rather large brown algae from rocks exposed to heavy wave action (18/ 07/2004).

Known distribution. Baía de Santos, São Paulo, Brazil ( Marcus, 1950).

Material. Observations on a live individual. Two whole mounts (one without a stylet). Type material from Lurus evelinae Marcus, 1950 : SMNH 95803, SMNH 95804.

Discussion. The Uruguayan specimens clearly belong to the taxon Luridae Sterrer & Rieger, 1990 . Typical of this taxon is the fact that the overall organisation resembles that of the Provorticidae and that a polylithophoric statocyst is present ( Marcus 1950; Faubel et al. 1994; Sterrer & Rieger 1990; Sterrer 1992).

Based on the morphology of the stylet (a spirally-winding tube, two turns), the Uruguayan specimens can be classified in Lurus evelinae Marcus, 1950 (see Marcus 1950). The specimens measure 0.3 mm. The stylet has an axial length of 165 μm. Since no whole mounts are available in the material from Brazil, the length of the stylet is estimated based on the figure drawn by Marcus (1950). Axially they measure 140 μm.

Although Sterrer & Rieger (1990) already mentioned some clear differences between Lurus evelinae Marcus, 1950 and all other species of Luridae , it was Faubel et al. (1994) who divided the monogeneric taxon Luridae into Lurus Marcus, 1950 (one species: L. evelinae ) and Luriculus Faubel et al., 1994 (four species: L. australiensis Faubel et al., 1994 , L. castor Sterrer & Rieger, 1990 , L. minos Sterrer, 1992 , and L. tyndareus Sterrer & Rieger, 1990 ). Lurus evelinae stands unique because it has paired (sometimes coalescing) testes and vasa deferentia, separate ovaries and vitellaria, and a clear differentiation between the seminal vesicle and the prostate vesicle. All other species of Luridae have a single testis, one median vas deferens, ovovitellaria and a combined seminal vesicle and prostate vesicle. Therefore they were transferred to the new genus Luriculus (see Faubel et al. 1994; Marcus 1950; Sterrer & Rieger 1990). One species, Lurus pollux Sterrer & Rieger, 1990 , remains a species inquirenda. Although L. pollux has only a single testis, one medioventral vas deferens and a seminal vesicle inside the copulatory bulb, Faubel et al. (1994) did not place it in Luriculus because vitellaria have not been observed. Besides the stylet, no other confirmative features could be observed in the live specimens of L. evelinae from Uruguay. The single testis could well be two coalescing testes and no vasa deferentia were seen. However, ovaries and vitellaria seemed rather separate.

As was discussed by Marcus (1950) and Sterrer & Rieger (1990), Lurus evelinae apparently always has two statoliths, whereas all other species of Luridae mostly have a variable number of statoliths (see Sterrer & Rieger 1990; Sterrer 1992): two to four in L. castor , two to five in L. pollux and three to four in L. tyndareus and L. minos . L. australiensis always has a constant number of three intracapsular and three extracapsular statoliths. In the whole mounts of the specimens from Uruguay, the statoliths were not visible. Only two statoliths were observed in the specimen that was studied alive. This seems to confirm the observations by Marcus (1950), which were made on serial sections, and were therefore doubted by Sterrer (1992).

After Luriculus minos (see Sterrer 1997), Lurus evelinae is the second species of Luridae to be reported from outside its type locality.

Figures

FIGURE 9. Lurus evelinae Marcus, 1950 (A) Habitus of a live animal. (B) Stylet. Vauclusia multistriata n. sp. (C) Habitus of a live animal.