NEW RECORD OF PENILIA AVIROSTRIS DANA, 1849 (CLADOCERA) IN THE GULF OF ST. LAWRENCE

摘要

The cladoceran, Penilia avirostris, was collected in zooplankton samples from Colville Bay, Prince Edward Island (46°N 62°W) in the southern Gulf of St. Lawrence, in the autumns of 2000 and 2001. This is the first report of the species from Canadianwaters, and represents a northeasterly range extension of 5 degrees of latitude or approximately 1130 km. The most likely vector for this introduction was ballast water from international shipping. In October 2000, when the species was first detected, the observed population density of 0.073 individuals/m3 represented less than 0.3% of the zooplankton community. One year later, the density was 27.5 individuals/m~3 and Penilia was the fourth most abundant zooplankter, accounting for 8% of the community.All females were parthenogenetic, but 0.3% of the individuals collected in 2001 were males, implying that sexual reproduction by resting eggs could occur in this population. The size of males (mean length 684 mu m, range 591-773 mu m) and parthenogenetic females (mean 840 fim, range 409-1000 mu m) was similar to those reported in the literature. Three percent of the females were juveniles, and a reproducing population appeared to be well established.