Reproductive behaviour of the branchial ectoparasite <i>Bopyrus crangorum</i> (Isopoda: Bopyridae) following ecdysis of the host <i>Palaemon serrifer</i> (Caridea: Palaemonidae)

Abstract The reproduction of bopyrid isopod parasites is thought to occur immediately following host ecdysis, but direct observations supporting this hypothesis are limited. aim study was describe the reproductive behaviour Bopyrus crangorum relative ecdysis based on video recordings. Several hours after biphasic moulting female observed. cuticle posterior body shed before that anterior at an interval 1 h. Two moulting, male repeatedly moved from its initial position between pleopods and stopped end fifth oostegite, above gonopore. To our knowledge, repeated visiting by males has not been previously observed in isopods. Oviposition through gonopore occurred 33 min later. male-removal experiment showed females with their removed visits oviposited eggs, whereas did not. We propose attempts inseminate female. hypothesised sperm released onto external surface each eggs fertilised as they pass opening, which would explain synchronous development inside marsupium. present provides new information life history isopods, allows for a better understanding host–parasite relationship.