Meeting Abstract
Egg size is one of the most important features of marine invertebrate reproduction because it provides insight into developmental patterns, offspring size, and adult investment per offspring. Intraspecific variation in egg size and the resulting hatchling size may depend on many factors including environmental and maternal conditions and geographic location. Therefore, both the season in which eggs are laid and the spatial heterogeneity of deposition sites may influence egg size and hatchling size. Natica chemnitzii deposits egg masses on sandy beaches along the coast of the Bay of Panama. During the wet (non-upwelling) season hatchling size is unimodal. However, monthly sampling in the same transect of beach shows that in the dry (upwelling) season hatchling size is bimodal with a peak at 136.5 microns, the normal hatchling size during the wet season and an additional peak at 152.9 microns. To determine if this bimodal pattern in hatchling size is due to either plasticity in one species or the concurrent seasonal reproduction of two species, we performed a more extensive survey of eggmass morphology and deposition site conditions at four sites around the Bay of Panama, during the dry season. Small hatchlings (< 145 microns) that appear in both the wet and dry seasons are produced from small to medium sized masses (30 to 70 mm diameter) and are abundant at all four sites. Large hatchlings (> 145 microns) which appear only in the dry season are produced from a wide distribution of eggmass sizes (> 20 mm diameter up to < 100 mm diameter), and only commonly occur at two sites. Hatchling size based on eggmass morphology and geographic location suggests that dimorphism in the upwelling season is due to two species. Sediment and DNA analyses are underway.
