Infection patterns and molecular data reveal host and tissue specificity ofPosthodiplostomumspecies in centrarchid hosts

Abstract

Posthodiplostomum minimum utilizes a three-host life cycle with multiple developmental stages. The metacercarial stage, commonly known as 'white grub', infects the visceral organs of many freshwater fishes and was historically considered a host generalist due to its limited morphological variation among a wide range of hosts. In this study, infection data and molecular techniques were used to evaluate the host and tissue specificity of Posthodiplostomum metacercariae in centrarchid fishes. Eleven centrarchid species from three genera were collected from the Illinois portion of the Ohio River drainage and necropsied. Posthodiplostomum infection levels differed significantly by host age, host genera and infection locality. Three Posthodiplostomum spp. were identified by DNA sequencing, two of which were relatively common within centrarchid hosts. Both common species were host specialists at the genus level, with one species restricted to Micropterus hosts and the other preferentially infecting Lepomis. Host specificity is likely dictated by physiological compatibility and deviations from Lepomis host specificity may be related to host hybridization. Posthodiplostomum species also differed in their utilization of host tissues. Neither common species displayed strong genetic structure over the scale of this study, likely due to their utilization of bird definitive hosts.

First report of Posthodiplostomum minimum metacercariae and resulting histopathological changes in Bagrus bajad from Lake Nasser, Egypt

“…Lane et al (2015) recorded ''white grub'' P. minimum metacercariae in many fish species. Boone et al (2018) detected white grub (P. minimum) metacercariae in the visceral organs of many centrarchids freshwater fishes. Kvach et al (2017) detected Posthodiplostomum cf.…”

“…distinctly bipartite body and tribocytic organ was discshaped with a median slit) and showed well-developed gonads and anlagen of some genital organs, but no melanin. (Boone et al 2018) mentioned that P. minimum metacercariae has limited morphological variation among a wide range of hosts.…”

“…This family contains different species of Posthodiplostomum (Dubois 1936). The metacercariae of Posthodiplostomum cuticola causing ''neascus'' or ''black spot'' disease in fish (Karimian et al 2013) and Posthodiplostomum minimum (MacCallum 1921) encysts in viscera and sometimes in musculature of fish given what is known ''white grub'' (Grizzle and Goldsby 1996;Lane and Morris 2000;Lane et al 2015;Boone et al 2018). The penetration of large numbers of the P. minimum cercariae into a fish may cause its death especially during the first few days after infection (Meade and Bedinger 1967).…”

Validity of the Diplostomoidea and Diplostomida (Digenea, Platyhelminthes) upheld in phylogenomic analysis

“…However, as seen above, morphometric deviations relative to these studies were small, and Palmieri (1977) showed that adult morphology varies a great deal within P. centrarchi. Also, deviations were obtained from hologenophores genetically matching P. centrarchi common in centrarchid hosts (e.g., see records in (Boone et al, 2018;Locke et al, 2010)), and therefore there is no doubt they represent P. centrarchi.…”

New record of metacercariae of the North American Posthodiplostomum centrarchi (Digenea, Diplostomidae) in pumpkinseed (Lepomis gibbosus) in Hungary

“…Hoffman (1958Hoffman ( , 1999 considered P. centrarchi a subspecies of P. minimum and named it P. minimum centrarchi because he proved that it could infect only centrarchid fishes while P. minimum minimum was able to infect only cyprinids. The strict host specificity of the P. minimum subspecies was supported by Locke et al (2010a,b), Lane et al (2015), Stoyanov et al (2017a) and Boone et al (2018). Accordingly, Stoyanov et al (2017a) elevated P. minimum centrarchi to species rank as P. centrarchi, and this novel name has become general since then (Kvach et al, 2018a;Ondra ckov a et al, 2019).…”