Ilyocryptus brevidentatus Ekman, 1905

Dartnall, Herbert J. G. & Hollwedel, Werner, 2007, A limnological reconnaissance of the Falkland Islands; with particular reference to the waterfleas (Arthropoda: Anomopoda), Journal of Natural History 41 (21 - 24), pp. 1259-1300 : 1272

Ilyocryptus brevidentatus Ekman, 1905

Originally described from the Falkland Islands and South Georgia ( Ekman 1905), this species has subsequently been recorded many times from South Georgia ( Sars 1909; Dartnall and Heywood 1980; Hansson et al. 1996; Dartnall 2005a) as well as from the South Orkney Islands ( Heywood 1967, 1970; Heywood et al. 1979; McInnes and Ellis- Evans 1990). Kotov et al. (2002) published a redescription of the species, recording it from the southern-most portion of Argentina and Chile. The specific name refers to the short denticles of the secondary armament of the post-anal section of the post-abdomen. In our specimens these denticles are slightly longer than those of both Ekman’s and Sars’ illustrations, with their tip reaching beyond the post-abdominal margin ( Figure 18 ), as shown by Kotov et al. (2002, Figures 41–43). They are of different lengths, proximally four small ones curved proximally, followed by two groups of 5 + 3 long ones; between these and the post-abdominal claw is a row of setae. The preanal section of the post-abdomen bears 19 denticles; the first three proximal ones are somewhat longer, the next 11 are of medium size followed by five long ones, the last three of which are the shortest, post-anal portion with two short and seven long denticles. Adult females are 0.65 mm long. Although Verkhov (1993) states I. brevidentatus is an inhabitant of the southern circum-polar district, Green (1981) lists it from tropical South America.

Figures

Figure 18. Ilyocryptus brevidentatus, female, post-abdomen.