Morphological and morphometric features of nematode-cysts in Gymnotus inaequilabiatus liver in the Brazilian Pantanal.

Gizela Melina Galindo,Robson Andrade Rodrigues,Carlos Eurico Fernandes,Priscilla Soares,Luiz Eduardo Roland Tavares,Sandriely Fernanda Marcondes

doi:10.1590/s1984-29612017044

Gizela Melina Galindo, Robson Andrade Rodrigues + Show 4 more

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https://doi.org/10.1590/s1984-29612017044

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Abstract

The aim of this study was to determine the morphometric measures and morphological aspects of nematode-cysts in Gymnotus inaequilabiatus, and the presence of melanomacrophage centers (MMCs) associated with the periphery of cysts and in the liver parenchyma. Adult specimens, 34 female (123.1 ± 43.9g) and 45 male (135.5 ± 43.4g), from Paraguay River, Corumbá, Brazil, were used. The number of nematode-cysts was determined in 79 livers and 25 of them randomly selected for histopathological analysis and morphometric measures of nematode-cysts (mean diameter, thickness of collagen layer, and cyst-wall layer). The percentage of cysts with MMCs on the periphery and density in the liver parenchyma was estimated. The average number of macroscopic cysts was of 48.7 ± 2.78. Granulomatous reaction was observed surrounding the cysts. Diameter, collagen layer and cyst-wall measurements were 293.0 ± 75.18 (µm), 17.72 ± 6.01 (µm) and 12.21 ± 9.51 (µm), respectively. The number of nematode-cysts was correlated with hepatosomatic index, (r=0.26, P<0.05). Collagen layer was correlated with cyst diameter (r=0.62, P<0.01). Pericystic and parenchymatous MMCs were moderately (r=0.48) and highly (r=0.90) correlated with nematode-cysts number. Morphological characteristics of hepatic tissue and cysts-nematodes measures suggest that G. inaequilabiatus acts as a paratenic host to nematodes in the larval stage.

Highlights

The Gymnotiformes constitute a small endemic group of Neotropical ichthyofauna (REIS et al, 2003)
Morphological characteristics of hepatic tissue and cysts-nematodes measures suggest that G. inaequilabiatus acts as a paratenic host to nematodes in the larval stage
The Gymnotus inaequilabiatus (Actinopterygii: Gymnotiformes) is popularly referred to as “tuvira” or “sarapó,” and, in general, it is active at night in aquatic macrophyte under lentic environments

Summary

Introduction

The Gymnotiformes constitute a small endemic group of Neotropical ichthyofauna (REIS et al, 2003). The Gymnotus inaequilabiatus (Actinopterygii: Gymnotiformes) is popularly referred to as “tuvira” or “sarapó,” and, in general, it is active at night in aquatic macrophyte under lentic environments These conditions provide a suitable habitat for the fish to feed on insects, their preferred food (GRASS & HÖFLING, 1992; PEREIRA & RESENDE, 2006). In the Pantanal region, these fish experience the transition from dry to flood seasonal conditions and may have developed adaptive physiological strategies to survive During these periods, many fish species are subjected to adverse situations such as large temperature fluctuations, food scarcity and a broad spectrum of pathological agents (BRITSKI et al, 2007; BARTON et al, 2002, RIOS et al, 2005). The synergism between lethal and sublethal parasitic infections and the population structure is a complex issue and many aspects are yet unknown (FEIST & LONGSHAW, 2008)

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