A comparison of reproductive patterns in epifaunal and infaunal gammaridean amphipods

Abstract

Comparisons of egg size and number are made for 10 epifaunal and 16 infaunal species of shallow-water marine or estuarine gammaridean amphipods from the north-western Atlantic. Epifaunal species have significantly more, smaller eggs than infaunal species of the same size and geographic region. Strong latitudinal and seasonal effects are also evident. For several species, egg size increases and egg number decreases in populations at more northern latitudes and in populations breeding during colder seasons. The few exceptions to the above patterns may reflect unique differences in the biology of particular species. A hypothesis is proposed that adult mortality risk is correlated positively with egg number and inversely with egg size.