Alternative Development Strategies of Clinostomum chabaudi (Digenea) Metacercariae in Frog Hosts (Hyperolius spp.)

Ulrich Sinsch,Carsten Balczun,J Maximilian Dehling,Patrick Scheid

doi:10.3390/d13020093

Ulrich Sinsch, Carsten Balczun + Show 2 more

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https://doi.org/10.3390/d13020093

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Abstract

Clinostomum metacercariae are common endoparasites of fish and frogs. In this study, we examine taxonomic identity and developmental strategy of Clinostomum metacercariae infesting reed frogs Hyperolius kivuensis and H. viridiflavus in Rwanda. Moreover, we evaluate the impact of infestation on demographic and morphological life-history traits of the hosts. Morphological and molecular features, particularly genital morphology and COX1 sequences, provided evidence that the metacercariae belong to C. chabaudi Vercammen-Grandjean, 1960. Depending on the host’s defensive behavior and the availability of resources, metacercariae develop either as sedentary “yellow grubs” encysted in the lymphatic sacs or mouth of the host or as initially encysted, but later free-ranging individuals invading the host´s body cavity. Nutrition on lymphatic fluid within the cyst leads to yellow-colored gut content, feeding on blood or host tissue, to brownish green gut content in free-ranging individuals. Almost all metacercariae opted for the first developmental strategy in H. kivuensis, whereas the second strategy dominated in metacercariae infesting H. viridiflavus. Hyperolius kivuensis suffered significant morphological modifications, when infested with encysted metacercariae. Both developmental modes permitted a coexistence with the host of less than one year. We hypothesize that the presence of alternative development modes is an adaptation of C. chabaudi to cope with resource limitation within host-produced cysts.

Highlights

Clinostomum spp. (Digenea: Clinostomidae) are digenetic trematodes with freshwater snails as first intermediate hosts, freshwater fishes and amphibians as second intermediate hosts, and fish-eating birds, reptiles and occasionally mammals as definite hosts [1]
Forty-five reed frogs H. kivuensis and H. viridiflavus were infested by numerous Clinostomum metacercariae, which were morphologically identified as C. chabaudi VercammmenGrandjean, 1960 (Figure 1)
Sucker and genital morphology did not differ among the specimens collected from H. kivuensis and H. viridiflavus, and those collected

Summary

Introduction

Clinostomum spp. (Digenea: Clinostomidae) are digenetic trematodes with freshwater snails as first intermediate hosts, freshwater fishes and amphibians as second intermediate hosts, and fish-eating birds, reptiles and occasionally mammals as definite hosts [1]. (Digenea: Clinostomidae) are digenetic trematodes with freshwater snails as first intermediate hosts, freshwater fishes and amphibians as second intermediate hosts, and fish-eating birds, reptiles and occasionally mammals as definite hosts [1]. They are distributed to all ecozones of the world. Clinostomum spp. infest a wide variety of intermediate and definite host species, indicating a remarkable variability in the developmental requirements of distinct life stages [2,3,4,5]. The ‘Old World’ clade includes currently ten morphologically and genetically distinct species (C. complanatum, C. cutaneum, C. phalacrocoracis, C. phillipinense, C. sinensis, C. tilapiae, C. ukolii, morphotypes 2–4) [7,9,10]. The validity of the taxon C. chabaudi Vercammen-Grandjean (1960) from DR Congo remains currently unresolved, as the description is based exclusively on morphological features of metacercariae [11]

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