Characterization of the Life Cycle of a Fish Eye Fluke,Austrodiplostomum ostrowskiae(Digenea: Diplostomidae), with Notes on Two Other Diplostomids InfectingBiomphalaria havanensis(Mollusca: Planorbidae) from Catfish Aquaculture Ponds in Mississippi, USA

Abstract

Ocular diplostomiasis is caused by trematode species in the family Diplostomidae, specifically those in the genera Austrodiplostomum, Diplostomum, and Tylodelphys. Diplostomid trematodes are globally distributed parasites of fish. Heavy infections of diplostomids that parasitize the eyes of fish can result in acute mortality while chronic infections are often characterized by impaired vision or blindness. In the southeastern United States, commercial catfish production is threatened by piscivorous birds and the many trematode species that parasitize them. The life cycles typically involve a piscivorous avian definitive host, a mollusk first intermediate host, and a fish second intermediate host. A survey of parasites infecting the snail host Biomphalaria havanensis (= B. obstructa ) in catfish production ponds was undertaken. Snails were collected from 2 separate ponds during the summer of 2014 and observed for the release of trematode cercariae. A total of 1,740 snails were collected. Three distinct longifurcate pharyngeate cercariae were observed and these cercariae were characterized morphologically and molecularly. Sequencing of ∼4,200 base pairs (bp) of the nuclear ribosomal genes and ∼450 bp of the mitochondrial cytochrome c oxidase gene revealed 3 genetically distinct species. One morphotype shared 99-100% sequence identity with metacercariae from the aqueous and vitreous humors of gizzard shad Dorosoma cepedianum and channel catfish Ictalurus punctatus as well as an adult trematode, Austrodiplostomum ostrowskiae, a parasite of the double-crested cormorant Nannopterum auritus. The remaining 2 cercariae morphotypes shared 99-100% sequence identity with an unidentified Tylodelphys sp. and Austrodiplostomum sp. metacercaria from the brain and eyes of several freshwater fish. Herein we molecularly link the cercaria, metacercaria, and adult stage of the life cycle of A. ostrowskiae, identifying the snail host for this parasite, in addition to providing notes on 2 cercariae representing 2 other diplostomids.

Helminth parasites of South American fishes: current status and characterization as a model for studies of biodiversity

“…Despite several records of metacercariae from freshwater fish in South America (Ostrowski de Núñez & Gil de Pertierra, 2004), few data are available using an integrated morphological and molecular approach, e.g. Austrodiplostomum compactum (Lutz, 1928) (= A. mordax ) has been isolated from more than 30 fish hosts (see references in Rosser et al ., 2016); however, several of these larval diplostomids may corresponds to A. ostrowskiae Dronen, 2009. Sequences of mitochondrial genes from metacercarie in Satanoperca spp.…”

Comparative Mortality of Juvenile Channel and Hybrid Catfish Exposed to Bolbophorus damnificus Cercariae

“…It is thought—although not empirically confirmed—that recent industry contraction and reductions in total water acreage devoted to catfish farming have increased bird pressure on the remaining operations, as loafing and foraging sites for piscivorous birds have been depleted while bird populations have remained stable (Cristie et al 2021). As a result, catfish operations will continue to battle piscivorous birds and the trematodes they carry (Burr and Dorr 2016; Rosser et al 2016a, 2016b, 2016c, 2017, 2018; Griffin et al 2018). Fortunately, management strategies and pond treatments are available to reduce snail populations in catfish ponds (Wise et al 2004, 2006; Mitchell et al 2007).…”

Metacercariae of Austrodiplostomum compactum (Trematoda, Diplostomidae) in non-native fish species in Brazil: a possible explanation for the high rate of parasitic infection

“…In South America, diplostomiasis is mainly caused by species of the genus Austrodiplostomum Szidat & Nani, 1951. The adults of Austrodiplostomum compactum (Lutz, 1928) were recorded in several countries from America (Argentina, Brazil, U.S.A., Mexico and Venezuela) inhabit the intestine of the piscivorous birds Nannopterum auritus (Lesson, 1831) (=Phalacrocorax auritus) and Nannopterum brasilianus (Gmelin, 1789) (=Phalacrocorax brasilianus) (Szidat & Nani 1951, Dubois 1968, Ostrowski de Núñez 1982, Dronen 2009, Monteiro et al 2011, O'Hear et al 2014, Garcia-Varela et al 2016, Rosser et al 2016. Although, cercariae emerge from the tegument of gastropods such as: Biomphalaria straminea (Dunker, 1848), Biomphalaria glabrata (Say, 1818) (Pinto & Melo 2013), Biomphalaria prona (Martens, 1873) (Ostrowski de Núñez 1982), Biomphalaria obstructa (Morelet, 1849) (Rosser et al 2016) and larval forms (metacercariae) can inhabit the eyes of several species of freshwater fishes (Yamada et al 2008, Ramos et al 2013). According to Ramos et al (2013Ramos et al ( , 2016 and Campos et al (in press), metacercariae of A. compactum have been reported in 38 Brazilian fish species belonging to 13 families of four orders, highlighting the high infection rates in Plagioscion squamosissimus (Heckel, 1840).…”