Occurrence of metacercariae of Austrodiplostomum compactum (Lutz, 1928) (Trematoda, Diplostomidae) in Pimelodus platicirris in the Ilha Solteira Reservoir, São Paulo, Brazil

Denis W.J Campos,Letícia O Manoel,Rosilene L Delariva,Rosicleire Veríssimo-Silveira,Lidiane Franceschini,Cristiéle S Ribeiro,Igor P Ramos

doi:10.1590/0001-3765202020180649

Abstract

This study reports the occurrence of metacercariae of Austrodiplostomum compactum in Pimelodus platicirris from a Neotropical reservoir in the Grande River, SP, Brazil. A total of 164 fish were collected, of which 12.80% were infected with metacercariae in the eyes. The mean intensity of infection and mean abundance were 1.52±0.14 (1‒3) and 0.23±0.05 (0‒3), respectively. The presence of this parasite with a high intensity of infection can cause exophthalmos, retinal displacement, opacity of the lens, blindness or even death. This is the first record of ocular metacercariae for P. platicirris, thus increasing the number of hosts for A. compactum.

Highlights

The superfamily Diplostomoidea Poirier, 1886, comprises a group of digenetic trematodes possessing a holdfast organ found posterior to the ventral sucker, a morphological innovation unique to this trematode group
Miracidia actively penetrate planorbid gastropods belonging to the genus Biomphalaria Preston, 1910 (in Brazil this has been reported in B. glabrata (Say, 1818) and B. straminea (Dunker, 1848)) (Pinto & Melo 2013), undergo morphological alterations, such as the loss of cilia, becoming saccular with cells from which several redia originate and from which the cercariae develop
As for the parasitological parameters, 21 were infected with metacercariae of A. compactum, with a mean intensity of infection and mean abundance of 1.52 ± 0.14 (1‒3) and 0.23 ± 0.05 (0‒3), respectively. These results may be associated with the availability of organic matter from fish farming deposited in the sediment (Beveridge 2004), increasing the abundance of gastropod mollusks in these areas (Edgar et al 2005)

Summary

Introduction

The superfamily Diplostomoidea Poirier, 1886, comprises a group of digenetic trematodes possessing a holdfast organ found posterior to the ventral sucker, a morphological innovation unique to this trematode group. This superfamily contains over 250 described species, 88 genera, 16 subfamilies and 6 families, including the family Diplostomidae (Blasco-Costa & Locke 2017). The biological cycle of diplostomids involves a first intermediate host (gastropod mollusks), a second intermediate host (fish) or rarely observed paratenic host (amphibians), and a definitive host (piscivorous birds). Adults of diplostomid species reproduce sexually in the intestine of infected piscivorous birds, depositing their eggs into the water through feces, with the hatching and release of miracidia (free-swimming larva) occurring within 22 days (Grobbelaar et al 2014). Piscivorous birds prey the infected fish, giving continuity to the cycle (Thatcher 2006, Rassier et al 2015)

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