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

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