Laimella Cobb 1920

Genus Laimella Cobb, 1920

Emended diagnosis. Sabatieriinae with striate cuticle; fine punctations may be also observed. Anterior and posterior cephalic sensilla closely spaced, posterior setae usually longer than anterior. Buccal cavity small, three small teeth may appear as weak cuticularisation at base of anterior buccal cavity. Spicule simple arcuate, gubernaculum with posteriorly directed paired apophyses. Supplements minute or absent. Tail elongate, posterior section filiform.

Remarks. Presently, there are 7 species of Laimella recognised as valid species; L. filipjevi Jensen 1979, L. minuta Vitiello 1970, L. longicauda Cobb 1920 and L. vera Vitiello 1970 (following the revision by Jensen (1979)), and L. annae Chen & Vincx, 2000, L. sandrae Chen & Vincx, 2000 and L. subterminata Chen & Vincx, 2000, described by Chen & Vincx (2000). Two species formerly described as belonging to Laimella have been reclassified as Paracomesoma (P. quadrisetosum and P. hexasetosum, both B. Chitwood (1937)), and a third species reclassified as Paramesonchium (P. serialis Wieser 1954) all by Jensen (1979). However, Jensen (1979) also undertook a number of synonimisations, specifically:

1. Laimella filipjevi nom. nov., pro Laimella longicaudata, syn. Sabatieria longicaudata Filipjev 1922.

2. L. longicauda Cobb 1920, syn. L. filicaudata Ward 1974.

Laimella filipjevi has been recently re-examined by Tchesunov (2000) who additionally recorded the species in the White Sea. However, the current authors believe that the reasons given to refer L. filicaudata to the status of junior synonym of L. longicauda are not valid: The description of L. filicaudata and the differences listed therein between this species and L. longicaudata are well defined (Ward 1974). Namely, relative tail length (11.2 vs 17.7 abd, L. filicauda and L. longicauda respectively), proportion of tail cylindrical (81 % vs 66 %) and relative lengths of the cephalic setae (R2:R3 = 1:3 vs 1:4). Laimella filicaudata Ward, 1974 is therefore reinstated here.

Published descriptions of these now eight known species of Laimella differ in the morphological characters considered of note, but reviewing these species the relative body proportions, including the de Man’s ratios, are particularly important. Therefore Table 1 presents a comprehensive comparison of the morphometric measurements of these species and Table 2 provides the calculated body proportions, such as de Man's ratios. Where measurements were not presented in the original publications they are supplemented by measurements made by the authors from the original published figures where possible.