Description, seasonal morphological variation, and molecular identification of Paraxanthus barbiger megalopae obtained from the natural environment

Abstract

Larval identiWcation represents a powerful tool for detailed studies on recruitment and population dynamics in marine invertebrates. However, intra-speciWc morphological variation can become a serious limitation for the correct identiWcation at species level. High morphological variation can be expected in species with continuous breeding periods because larvae are exposed to seasonal Xuctuations in physical and biological factors during their development in the plankton. We describe, for the Wrst time, the megalopae of Paraxanthus barbiger, one of the most common and abundant brachyuran crabs along the coast of Chile. To validate larvae identiWcation, the 16S rRNA gene was sequenced from both megalopae and adults, and was compared with sequences of three sympatric species. In addition, size, body shape, and appendage setation pattern variations were analyzed with a year-round sampling scheme. The results demonstrated high seasonal phenotypic plasticity in size. Despite these diVerences, certain conservative characteristics exist which can be very useful for identiWcation at species level.