MEPS 280:13-23 (2004)  -  doi:10.3354/meps280013

ABSTRACT: Marine larval biologists frequently assume that selection to shorten larval duration drives the evolution of reproductive strategies (e.g. egg size). If this assumption is correct, we would also expect larval duration to influence when adults spawn, because adult spawning time can influence the amount of food and temperatures larvae experience, and thus larval duration. Here we develop a simple model to predict development times for marine invertebrates with lecithotrophic larvae as a function of spawning date and sea-surface temperature for the NE Pacific Ocean. We focus on species with non-feeding (lecithotrophic) larvae because the duration of larval life is most influenced by seawater temperature alone. Because there are few empirical data on the relationship between larval development rate and temperature of lecithotrophic species, we used several different functions that represented a range of shapes. Our primary result reveals that the shape of the relationship of development rate to temperature has a pronounced influence on which spawning dates result in the shortest larval duration. For an increasing decelerating relationship, there is a broad range of spawning dates that minimize larval duration. This relationship did overlap with the empirical spawning data for lecithotrophic species in the region. However, for a linear and an increasing accelerating relationship, there is a narrower range of time that results in the shortest larval duration, and for these 2 relationships, observed spawning times did not match as well. Our model also predicted substantial inter-annual variation in development times for all relationships. In addition, we compared spawning times for species with planktotrophic and brooded larval development and found reproductive periods for species with planktotrophic larvae to be similar to those for lecithotrophic larvae, while species with brooded larvae are reproductive over broader periods. Our results suggest that earlier reproductive periods may be favored for reasons independent of development time, potentially including decreased larval predation and increased recruitment success.

KEY WORDS: Development time · Lecithotrophy · Larva · Spawning time · Temperature