Experimental infection of yellow perch (Perca flavescens) with Apophallus brevis (Digenea, Heterophyidae): parasite invasion, encystment, and ossicle development

Abstract

Yellow perch (Perca flavescens) were exposed to cercariae of Apophallus brevis collected from naturally infected snails and maintained for up to 63 d postinfection (PI). Histochemistry revealed that attachment, penetration, migration, and encystment were complete by 2 d PI. By 14 d PI, a precursor to a host ossicle capsule surrounded the encysted metacercaria. Between 14 and 63 d PI a calcified matrix aggregated in a specific developmental pattern of islets, crescent, band, then ring, within an equatorial band at the cyst–capsule interface. The result was an ossicle ring of calcified tissue separating two uncalcified-matrix poles. Ossicle rings thickened and advanced over the cyst, but did not seal it off completely, forming an intermediate ossicle 49 d PI with two polarized canals. Pigmentation of ossicles through the appearance of melanocytes was not consistent between infections of the same age. Scanning electron microscopy revealed two distinct regions within fully developed ossicles. Randomly distributed interstitial fibres and ovoid and tubular lacunae surrounded by perilacunar collars formed the inner cellular region. The interstitial fibres within the outer region formed acellular/lamellar bands.

Joint effects of parasitism and pollution on oxidative stress biomarkers in yellow perch Perca flavescens

“…Furthermore, results suggest that infection with A. brevis can cause pathological effects away from the site of infection, as metacercariae are found on the skin and in muscle, but effects were measured in liver. This parasite is unique in that it induces a host reaction consisting of the formation of a mineralized ossicle or cyst (Taylor et al 1993) which conceivably may pose an oxidative stress to the host as a result of the chronic inflammation at the infection site (Taylor et al 1994). The effects of parasitic infection are all the more interesting because they were evident at relatively low intensities, especially for R. acus.…”

Ectopic ossicles associated with metacercariae of Apophallus brevis (Trematoda) in yellow perch, Perca ftavescens (Teleostei): development and identification of hone and chondroid bone

“…1). Details of free-swimming cercariae, penetration of cercariae into the host, and burrowing and pre-encystment are described in Taylor et al (1993).…”

“…Four lines of evidence can be used to evaluate cell types involved in ossicle formation: (1) morphology of the primary responding cells abutting the surfaces of the cysts, (2) location of ossicles within skeletal muscle connective tissue and surface-lining connective and supporting tissues of the eyes and brain (Taylor et al 1993), (3) regularity of fibroblast involvement in host cyst formation in other parasitisms (other than digenic trematodes) and (4) plasticity of piscine fibroblasts as shown by their ability to transform into chondrocytes (Blazer and Gratzek 1984).…”

Parasitisation by Bathycreadium elongatum ­(Digenea, Opecoelidae) in pyloric caeca of Trachyrincus scabrus (Teleostei, Macrouridae)

“…Platyhelminth presence within intra-abdominal tissues normally results in a granulomatous response by the host, which may include encapsulation and melanisation, that surrounds the parasite in order to isolate and destroy it (Sharp et al 1992, Torres et al 2002, as occurs with Bathycreadium elongatum in the visceral cavity of Trachyrincus scabrus. Studies of the histopathology associated with digenean infection in fish are scarce and are mostly limited to freshwater hosts (Taylor & Hall 1993, Taylor et al 1994, Dezfuli et al 1997. These studies are focused on the penetration and migration of digenean larval stages (Paperna & Dzikowski 2006) or digenean endoparasites that naturally invade host tissues as a part of their life cycle (Ogawa et al 1989, Mladineo 2006.…”