MORPHOLOGICAL ABERRATIONS IN FEMALES OF THE GENUS ACARTIA (COPEPODA, CALANOIDA) IN THE BALTIC SEA

Morphological aberrations of the 5th pair of legs (P5) of females of t he calanoid copepod genus Acartia from the Baltic Sea were observed. T he aberrant shape of P5 ranged from thickening to doubling or tripling of the apical spines on one or both legs or even introduction of addi tional segments. From 7 to 16% of A. bifilosa females showed a deforma tion of P5 in the samples taken recently from German coastal waters, t he Bornholm Sea, and the Lithuanian coast, but lower frequencies were observed in the specimens from the Polish coast (no abnormalities) as well as from the Gotland Sea (2%). In A. tonsa, A, longiremis, and A, discaudata, less than 4% of the females were abnormal. Coastal-open-se a or pollution gradients did not explain this. In A, bifilosa from the Kiel Bight, females from a sample collected in 1924 showed a similar frequency (14%) and the same structure of P5 aberrations in comparison with recent ones. It is suggested, that the described abnormalities a re most likely a natural phenomenon for this genus.