Maternal effects on cloning frequency, larval development and juvenile size in the seastar Asterias forbesi
College of Willam and Mary
A fundamental life-history trade-off occurs between the size and number of offspring that a female produces. Traditionally, biologists have assumed that there is a species-specific optimal egg size, the value of which can fluctuate with changing environmental parameters. However, in unpredictable environments a bet-hedging strategy resulting in variable offspring sizes may be favored. The sea star Asterias forbesi produces eggs that vary more than two-fold in volume within a single clutch (110µm - 150µm diameter). In addition, the larvae derived from these eggs have frequently been observed to produce clones. To test for maternal effects on cloning frequency and larval development we sorted sibling embryos at the blastula stage into large (190µm mean diameter) or small (140µm mean diameter) size classes. Previous studies have shown that exogenous cues can alter the frequency of cloning, but it is unclear whether endogenous reserves might also influence the asexual production of larvae. Our results suggest that despite an initial disadvantage in energy reserves, small treatments produced clones at frequencies similar to their large siblings. Since little is known how maternal investment affects juvenile quality in sea stars, we continued to follow these larvae and examined the effect of maternal investment on time to and size at metamorphosis. Small treatments took about 2 additional days compared to large treatments before settling as juveniles, a 6.3% increase in developmental time. Because the experiment ended early, our estimate of the developmental period for larvae from small eggs is highly conservative. Size at metamorphosis did not appear to be affected by maternal investment and varied greatly within treatments.
Blackburn, Holly N. and Allen, Jonathan D., "Maternal effects on cloning frequency, larval development and juvenile size in the seastar Asterias forbesi" (2013). Marine Lab Student Papers and Projects. Paper 10.