POPULATIONS OF TRIOPS-CANCRIFORMIS (BOSC) (NOTOSTRACA) IN GERMANY NORTH OF 50-DEGREES-N ARE NOT CLONAL AND AT BEST FACULTATIVELY HERMAPHRODITIC

Populations of Triopsidae (Notostraca) exhibit a wide variation in sex ratio and, therefore, have received enormous interest. However, inves tigations focusing on this subject are often suffering from problems i n discriminating males and females phenotypically. In the present stud y 29 individuals of Triops cancriformis found in two locations in Germ any were characterized ethologically, morphologically, and histologica lly in order to investigate the reliability of the sex ratio of popula tions north of 50 degrees N. Among ten distinct morphological characte ristics the structure of the eleventh pair of legs turned out to be th e only suitable one for discriminating the gender of (fixed) Triops ma terial. This was confirmed by histological examination of the respecti ve gonads. In total, three sexual males were found. Their sperms were round and non-flagellar, contained large nuclei, and showed no signs o f degeneration. Histologically, there was no evidence for the occurren ce of hermaphroditic individuals. These findings suggest that Triops c arcriformis populations in Ger many north of 50 degrees N are not clon al and at best facultatively hermaphroditic. In conclusion, the result s of the present study provide evidence for the occurrence of sexual T riops cancriformis males and females in European populations at latitu des beyond 50 degrees N for the first time. Generally, this is the nor thernmost find of male Triops cancriformis in Europe and the first rep ort of recent males in Middle Europe since 1955.