Meeting Abstract

28.5  Friday, Jan. 4  Variability in Larval Provisioning and its effects on Juvenile Size and Survivorship in Four Bryozoan Species KOSMAN, E*; PERNET, B; California State University, Long Beach etkosman@yahoo.com

There are few estimates of the magnitude or partitioning of variation in offspring size (as a measurement of per-offspring investment, POI) in marine invertebrates. Yet, POI often has strong fitness-related effects on later stages of development, and variation in POI and its partitioning should affect a population�s approach to an optimum offspring size. We compared the amount of variation in POI found within and among broods in four species of bryozoans by measuring larvae released from individual colonies collected or reared in the field. We also examined the effects of interspecific variation in POI on juvenile size and survivorship in a low food environment. We found greater variability in larval volume within broods than among broods in three of the four species, with the average coefficient of variation of a brood ranging from 10.27+2.81 to 17.72+3.60 among species. Although there was no correlation between mean larval volume and mean juvenile lophophore volume among species (r=0.891, p=0.109), there was a positive correlation between mean larval volume and the mean number of lophophore tentacles in the first zooid (r=0.956, p=0.044). Juveniles that metamorphosed from the largest larvae (those of Watersipora subtorquata) survived significantly longer in a low food environment than those of the other three species of bryozoans. These results suggest that great variation in POI within broods may be common among bryozoan species that produce lecithotrophic larvae, and that as POI increases, additional energy maybe allocated to both producing more juvenile feeding structures and to juvenile maintenance.