Comparative morphology of the axial skeleton in the family trichodactylidae freshwater crabs (Crustacea: Decapoda: Brachyura)

Abstract

The axial skeleton is a complex structure of cuticular origin, formed by sclerotic plates of thoracic sternite and pleurites as well as its internal invaginations. The ventral characters of the axial skeleton, reflected externally in the suture lines of the thoracic sternum, are an important classification criteria for the current suprageneric system of Trichodactylidae: (Trichodactylinae & Dilocarcininae (Dilocarcinini + Valdiviini)). In order to test this hypothesis, the internal and external characters of the axial skeleton of 42 adult crabs belonging to 17 species and 10 genera were examined. For the material preparation the crabs were dissected and their skeletons submerged in a hot solution of potassium hydroxide (KOH) for a period of 24 to 48 hours. Variations in the shape, orientation and conformation of the thoracic sternum, pleural roof, ventral and dorsal phragmas and junction plate were described from anatomical preparations. Based on these characteristics, the species were separated into three groups, which are consistent with the proposed classification of Trichodactylidae into subfamilies and tribes. This study highlights the importance of the morphological characteristics of the axial skeleton for Trichodactylidae taxonomy.