MEPS 385:165-178 (2009)  -  DOI: https://doi.org/10.3354/meps07984

ABSTRACT: We investigated the spatial morphological variability of the most abundant small planktonic copepod Oithona similis in the Barents and White Seas. Four areas differing in temperature and salinity were delineated in each sea. The average prosome length increased but relative antennae size decreased in both sexes from south to north in both seas. Antennule length tended to decrease from north to south and from east to west in the White Sea, and from north to south and west to east in the Barents Sea. In both areas examined, the average body size and relative setae length correlated negatively with temperature and positively with salinity, while total antennule length, total number of setae, total setae length and relative antennule length correlated negatively with salinity and positively with temperature. In the Barents Sea, the morphological parameters of O. similis were more significantly correlated with temperature, while those in the White Sea were more strongly correlated with salinity. We suggest that O. similis body size and morphological parameter variations along the south–north axis in the Barents and White Seas can be explained by water temperature and salinity variations, respectively, and have an adaptive significance. Our data suggest that food conditions had less effect on body size and morphological variation. Through analysis of morphological parameters over a wide spatial scale, the present study has shown that 3 and 4 groups of O. similis were present in the Barents and White Seas, respectively.

KEY WORDS: Oithona similis · Body size · Morphology · Temperature effects · Salinity effects · Barents Sea · White Sea