Comparative morphology of the stomach ossicles of four freshwater crabs species of Dilocarcinini (Crustacea, Decapoda, Trichodactylidae)

Abstract

Abstract The morphology of the foregut ossicles of representatives of four genera of Dilocarcinini were described to assess the usefulness of the ossicles as possible morphological characters in studies on the intrafamilial relationships of Trichodactylidae. Stomachs of specimens of Dilocarcinus pagei Stimpson, 1861, D. septemdentatus (Herbst, 1783), Moreirocarcinus emarginatus (H. Milne Edwards, 1853) and M. laevifrons (Moreira, 1901) were heated for 60 minutes in 10% KOH solution and then were stained with Alizarin Red 1% added into the KOH solution. The foregut ossicles of Dilocarcinini consists of 11 ossicles of the gastric mill, 10 of the lateral supporting cardiac region, 4 of the cardio-pyloric valve, 6 supporting the dorsal pyloric stomach, 9 supporting the ventral pylorus and bulb, 3 supporting the supra-ampullary region, 5 supporting the lateral pylorus region, totaling 48 ossicles and the following 34 are similar in shape, size and degree of calcification. The morphological differences between the majority of the ossicles were not very clear among the species, showing inconsistency intrageneric differences, however, species of different genera showed small similarities between them. There is a clear need for including more taxa in a comparative analysis, combined with external morphology and perhaps even molecular data to properly evaluate the phylogenetic relationships within Trichodactylidae and their systematic position within Brachyura.