Austrodiplostomum sp., Bolbophorus sp. (Digenea: Diplostomidae), and Clinostomum marginatum (Digenea: Clinostomidae) metacercariae in inland silverside Menidia beryllina from catfish aquaculture ponds, with notes on the infectivity of Austrodiplostomum sp. cercariae in channel catfish Ictalurus punctatus

Abstract

In the southeastern USA, catfish aquaculture is burdened by predation from piscivorous birds and the digenetic trematodes they carry. In addition to cultured ictalurid fish, other forage or incidental fish species inhabit catfish production ponds. Of these, the inland silverside Menidia beryllina was recently found to harbor larval metacercariae of several trematode species. Three species of metacercariae were reported, two of which represent the first morphological descriptions of an Austrodiplostomum sp. and Bolbophorus sp. metacercaria, respectively. A total of 15 silversides were collected from a commercial catfish pond and examined for trematode infection. These fish were parasitized by metacercariae of an Austrodiplostomum sp. (100 % prevalence) in the eyes and brain, a Bolbophorus sp. (86.7 % prevalence) in the musculature, and Clinostomum marginatum (33.3 % prevalence) in the musculature and fins. All three trematode species were characterized morphologically and molecularly by sequencing of the cytochrome c oxidase subunit 1 gene (CO1). In addition, the internal transcribed spacer 1 region (ITS1), 5.8S rRNA gene, and ITS2 region were determined for the Bolbophorus sp., which linked this metacercaria to a Bolbophorus sp. cercaria from a planorbid snail Planorbella trivolvis and an unnamed Bolbophorus sp. adult from the American white pelican Pelecanus erythrorhynchos. Furthermore, Biomphalaria havanensis snails were collected from the same pond and found actively shedding cercariae morphologically and molecularly consistent with a diplostomid cercaria reported from Bi . havanensis in catfish ponds in Mississippi, USA. Sequence comparisons deemed these cercariae conspecific to the Austrodiplostomum sp. from inland silverside described here. Channel catfish fingerlings were exposed to these cercariae at doses of 50 and 100 cercariae per fish. The infectivity of this Austrodiplostomum sp. in channel catfish was assessed at 10 and 20 days post exposure (dpe). Metacercariae were observed in both the eyes and brain of infected channel catfish, supporting molecular data that suggests the cercaria and metacercaria are both stages of a previously unidentified Austrodiplostomum sp. life cycle.

Clinostomum poteae n. sp. (Digenea: Clinostomidae), in the trachea of a double-crested cormorant Phalacrocorax auritus Lesson, 1831 and molecular data linking the life-cycle stages of Clinostomum album Rosser, Alberson, Woodyard, Cunningham, Pote & Griffin, 2017 in Mississippi, USA

“…Clinostomid cercariae collected from infected snails were pooled into a 500-ml beaker, the water was gently agitated with a magnetic stir bar, and the average number of cercariae per milliliter was determined from ten 0.1 ml aliquots according to previously established protocols (Griffin et al, 2012(Griffin et al, , 2014Rosser et al, 2016b;Alberson et al, 2017). Channel catfish fingerlings (c.2-4 cm) reared indoors for infectious disease research at the Thad Cochran National Warmwater Aquaculture Center in Stoneville, MS, were used in infectivity studies.…”

“…For all cercariae and metacercariae gDNA extracts, three regions were amplified as described previously using the BD1/BD2 primers for the ribosomal ITS regions, cox1_schist5'/acox650r primers for the cox1 gene, and NDJ11/NDJ2a primers for the nad1 gene. Additionally, the nad1 gene was amplified from archived gDNA of an adult of Clinostomum marginatum from a great egret (n = 1) , metacercaria of C. marginatum from an inland silverside (n = 1) (Rosser et al, 2016b), and an adult of Clinostomum album collected from a great egret (n = 1) .…”

“…Metacercariae of C. album are morphologically ambiguous and ranges for most morphological characters used to describe metacercaria overlap with C. marginatum, which is known to occur in cultured channel catfish (Lorio, 1989) and other forage fish in catfish production systems in Mississippi (Rosser et al, 2016b). Catfish experimentally challenged with C. album cercariae and controls contained no developing metacercariae suggesting that catfish are not a host for C. album.…”

Patterns ofClinostomum marginatuminfection in fishes and amphibians: integration of field, genetic, and experimental approaches

“…Although classical studies contend that species identity varies as a function of intermediate host identity (amphibians vs fishes), our findings indicated that C. marginatum often infects amphibians as well as fishes in the same habitats. Prior to recent molecular studies (Caffara et al , 2011; Sereno-Uribe et al , 2013, 2018; Pérez Ponce de León et al , 2016; Rosser et al , 2016, 2017), Clinostomum species determination was often based on geographical location (New vs Old World) and intermediate host identity (fishes vs amphibians) (Yamaguti, 1933; Hunter and Hunter, 1935; McAllister, 1990). Alongside the findings of Bonnet et al (2011), our results indicate that C. marginatum frequently infects both amphibians and fishes that co-occur in the same aquatic environment.…”

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

“…The high densities of fish present in catfish ponds have provided ideal foraging grounds for piscivorous birds, such as the American white pelican Pelecanus erythrorhynchos , great blue heron Ardea herodias , great egret Ardea alba , and double‐crested cormorant Phalacrocorax auritus . The presence of these birds has led to massive depredation and optimal conditions for propagation of trematode life cycles (Levy et al 2002; Glahn and King 2004; Yost et al 2009; Griffin et al 2012; Rosser et al 2016b, 2016c; Alberson et al 2017).…”