Reproductive behaviour of three species of freshwater crabs of the family Trichodactylidae (Crustacea: Decapoda) including forced copulation by males

Abstract

This report includes a detailed description of the reproductive behaviour of the freshwater crab Zilchiopsis collastinensis in the family Trichodactylidae and some observations on two other genera. It presents observations on the courtship, copulation, spawning, incubation and maternal care in Z. collastin- 15 ensis. No discernible courtship behaviour occurred. We found instead that forced copulation is practised by males. Z. collastinensis copulations were observed in between April and October, for Dilocarcinus pagei between January and August, and throughout the year for Trichodactylus borellianus. The spawning behaviour of all of the species observed took place out of the water. 20 Incubation lasted between 46 and 62 days in D. pagei, 37 and 41 days in Z. collastinensis and 8 and 12 days in T. borellianus. The number of juveniles carried by each ovigerous female ranged from 651 ± 172 in Z. collastinensis, through 582 ± 8 in D. pagei to 63 ± 33 in T. borellianus. The results support the proposition that members of the family Trichodactylidae, comprising 25 exclusively endemic freshwater crabs, have evolved unusual adaptive reproductive behaviours to optimize their reproductive fitness in unstable environments.