Pathology caused by adult Pseudochondracanthus diceraus (Copepoda: Chondracanthidae), a parasite of bullseye puffer fish Sphoeroides annulatus

The chondracanthid copepod Pseudochondracanthus diceraus is a parasite commonly found on the gills of wild bullseye puffer fish, Sphoeroides annulatus, in Sinaloa, Mexico. This paper provides the first description of some blood parameters and gill histology of wild bullseye puffer fish infected by an adult parasitic copepod P. diceraus. Sixty two wild fish were acclimatized for 15 days in experimental tanks, and then on days 16 and 21, samples were taken. Results showed a 100% prevalence and a mean intensity of 7.16 (1-17) copepods per fish. P. diceraus preferred the anterior and posterior sector of each gill arch. The percentage of leukocytes was significantly lower in fish with the highest intensity of infection. The gill response of the host was most evident near the parasite's attachment site. It was characterised by hyperplasia and fusion of secondary lamellae, chondrocyte hyperplasia of primary lamellae, atrophy of the lamellar epithelium and an increase in the number of mucous cells. The damaged gill tissue of the bullseye puffer fish was caused by the large and strong antennae of P. diceraus that is modified as a claw to attach to the host gills. Thus, a high prevalence and intensity of this copepod could become a potential health risk to the bullseye puffer fish culture.