Parasitic Crustaceans

This chapter provides a brief overview of crustacean parasites that infect commercially important fish and shellfish. Crustaceans are a diverse group of arthropods, with over 60,000 species that are significant to the aquaculture and fisheries sector, including parasitic species affecting other crustaceans, mollusks, and fishes. This chapter focuses on parasitic caligid copepods (sea lice), cymothoid isopods, and pea crabs of high economic impacts on commercially important aquatic species. The biology of the parasites, their effects on their hosts, the epidemiology of the infections, and economic impacts of these groups are described. Chemical treatments and husbandry modifications as management options for a range of crustacean parasites are presented, which includes the use of cleaner fish to remove parasites, specially designed cages to reduce infestation of parasites, or moving farms to deeper waters. The utilization of crustacean parasites as marine pest controls is further discussed, with emphasis on either its potential benefits or the negative effects on native crab populations. Despite the continuous adverse impacts parasitic crustaceans have on aquaculture, the progressive understanding of their biology and ecology may eventually lead to mitigation, if not complete eradication, of the parasites.

Crustacean parasites of Leporinus affinis, an Anostomidae fish from the Brazilian Amazon

This study investigated the fauna of ectoparasitic crustaceans in Leporinus affinis from Reservoir Coaracy Nunes, in eastern Amazon (Brazil), as well as the parasite-host interactions. The mouth, gills and tegument of 50.9% of the fish examined were parasitized by Argulus chicomendesi, Ergasilus turucuyus and Excorallana berbicensis, and a total of 118 parasites were collected. The dominance was found for E. berbicensis and the higher infestation levels were caused by E. berbicensis on the body surface of the hosts, but E. turucuyus had the highest prevalence on the gills of this host. The cluster analysis revealed higher similarity in the infestations by E. berbicensis and A. chicomendesi in relation to infestation site in hosts. Host sex and relative condition factor (Kn) were not influenced by moderate parasitism, but the abundance of parasites presented negative correlation with weight and Kn of the fish. This is the first study on the parasites of L. affinis showing low species diversity, with moderate prevalence and low parasite abundance.

Association of Epistylis spp. (Ciliophora: Peritrichia) with parasitic crustaceans in farmed piava Megaleporinus obtusidens (Characiformes: Anostomidae)

Parasitic diseases have caused significant problems to global aquaculture production. These studies will further our knowledge of this complex problem and help implement adequate prevention measures and control strategies. The present study aimed to investigate the presence of parasites in Megaleporinus obtusidens and to describe the epidemiology and pathology of parasitic infections in these fish. Five moribund fish were sent for parasitological examination. The integument and gills were scrapped off with a glass slide, and samples were examined under a light microscope. Parasitic crustaceans found in these specimens were submitted for scanning electron microscopy and histological analyses. The crustaceans Dolops carvalhoi and Lernaea cyprinacea and the Epistylis spp. were present in all fish examined. Epistylis spp. were also seen on the entire surface of the crustacean integument. Microscopic lesions observed in the parasitized gills included hyperplasia and hypertrophy of the lamellar epithelium, an inflammatory infiltrate, telangiectasia, foci of hemorrhage and necrosis, fusion of the secondary lamellae, and detachment of the lamellar epithelium. Crustacean parasites are important mechanical vectors of Epistylis infection and disseminate the disease in fish farming operations. Epistylis spp. infection affects the health of fish and has significant ecological and economical impact on aquaculture.