Application of DNA fingerprint to link megalopas and adults of Johngarthia lagostoma (H. Milne Edwards, 1837) (Decapoda, Gecarcinidae) and description and illustration of the megalopa stage

Abstract

Johngarthia lagostoma is a terrestrial crab species endemic to a limited number of oceanic islands in the south Atlantic Ocean, separated by hundreds or thousands of open seas, namely Rocas Atoll, Fernando de Noronha, Trindade and Martin Vaz, and Ascension. Such a narrow distribution range adds to the vulnerability of this species. The remoteness of the islands, combined with a narrow breeding window, accounts for information gaps in its developmental biology so that, before this study, only the first zoeal stage of its larval development had been described. Here, a DNA fingerprint using partial sequences of the 16S and barcode regions of COI mitochondrial genes was successfully applied to link megalopas recovered in Trindade from inside burrows of J. lagostoma to adults of this species. Megalopas and adults were confirmed to be conspecific, with an average pairwise p-distance of 0.001% (range 0–0.004%). The current finding that the megalopas belong to J. lagostoma provides additional evidence for the megalopas being the stage of terrestrial recruitment in J. lagostoma, not the first crab stage as initially thought. The megalopa stage of J. lagostoma is herein described and illustrated, and a synoptic table is provided to facilitate the morphological comparison of the megalopa stage of J. lagostoma with those of its congeners and closely related species in the genus Gecarcinus.