Comparative biology of the predatory cladoceran Cercopagis pengoi from Lake Ontario, Baltic Sea and Caspian Sea

Document Type

Article

Publication Date

2000

Publication Title

Archiv fur Hydrobiologie

Volume

149

Issue

1

First Page

23

Last Page

50

Abstract

Cercopagis pengoi, an onychopod cladoceran native to the Ponto-Caspian-Aral region, was first found in the Baltic Sea in 1992 and in Lake Ontario in 1998. Morphological studies of C. pengoi from Lake Ontario, Baltic Sea and Caspian Sea revealed a high degree of variability in body length, structure and length of the caudal process, and shape and size of the brood pouch. The female brood pouch changed dramatically in size and shape between instar stages, resulting in distinctive appearances. Males had significantly shorter body length, caudal process length and distances between adjacent articular spines than did females. Instar III parthenogenetic females dominated populations of C. pengoi from all geographical localities. Body length of all instar stages, genders, and reproductive modes from Lake Ontario was smaller than that of comparable individuals from European localities. The ratio of caudal process length to body length also varied geographically, with highest values observed for individuals from Lake Ontario. Clutch size for instar III parthenogenetic females from Lake Ontario was lower than values reported from the Baltic Sea and Caspian Sea. Observed differences in morphological and reproductive characteristics of geographically remote populations may reflect C. pengoi's vulnerability to zooplanktivory or responses to environmental conditions.

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