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Diseases of Aquatic Organisms

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DAO 132:229-239 (2019)  -  DOI: https://doi.org/10.3354/dao03307

The parasitic isopod Mothocya nana drives dietary shifts and poorer condition of Brazilian silversides Atherinella brasiliensis

Joice Silva de Souza1,2, Bruna Garcia da Cruz Canellas1, Roberson Sakabe3, Luciano Neves dos Santos4, Alejandra Filippo Gonzalez Neves dos Santos1,2,*

1Laboratory of Applied Ecology, Department of Zootechny and Sustainable Socioenvironmental Development, Fluminense Federal University (UFF), 24230-340, Niterói, RJ, Brazil
2Graduate Course in Ocean and Earth Dynamics (DOT), Fluminense Federal University (UFF), 24210-346, Niterói, RJ, Brazil
3Laboratory of Aquaculture, Department of Zootechny and Sustainable Socioenvironmental Development, Fluminense Federal University (UFF), 24230-340, Niterói, RJ, Brazil
4Laboratory of Theoretical and Applied Ichthyology (LICTA), Federal University of the State of Rio de Janeiro (UNIRIO), CEP 22290-240, Rio de Janeiro, RJ, Brazil
*Corresponding author:

ABSTRACT: Cymothoids are ectoparasites that may attach to various parts of the fish for molting and reproductive purposes, thus increasing the energetic costs of the host. This study investigated the influence of the parasitic isopod Mothocya nana on the physiological condition and diet of adult Brazilian silversides Atherinella brasiliensis at a sandy beach in southeastern Brazil. We collected 268 A. brasiliensis individuals, of which 230 fish were non-parasitized (mean ± SE total weight [TW] = 16.92 ± 0.38 g; total length [TL] = 127 ± 0.88 mm) and 38 were parasitized by up to 2 isopods (TW = 15.89 ± 0.79 g; TL = 126 ± 1.96 mm). Parasitic prevalence (P) and intensity (I) reached highest values in June 2015 (P = 20.88%; I = 1.31) and were slightly higher on males (P = 17.39%; I = 1.33) than on females (P = 13.07%; I = 1.27). Parasitized fish revealed poorer condition than non-parasitized ones, among which male hosts were especially burdened by M. nana’s attachment. The condition factor, the eviscerated condition factor and the fullness index each showed a decreasing trend according to the parasite’s development and offspring weight (i.e. increase in egg and larval weight). Parasitized and non-parasitized Brazilian silversides fed mainly on microcrustaceans, but the first group showed reduced phytoplankton intake and was associated with fewer trophic categories in comparison to non-parasitized fish. These dietary shifts revealed correlation with the poorer physiological condition reported for infected A. brasiliensis, whose decreased feeding efficiency is likely related to potential impairment of the filter-feeding mechanism and/or altered behaviour due to pressure atrophy and the increased energetic costs imposed by M. nana’s development.


KEY WORDS: Parasitism · Cymothoidae · Diet · Physiological condition · Generalized linear models · Partial redundancy analysis


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Cite this article as: Souza JSd, Canellas BGdC, Sakabe R, Santos LNd, Santos AFGNd (2019) The parasitic isopod Mothocya nana drives dietary shifts and poorer condition of Brazilian silversides Atherinella brasiliensis. Dis Aquat Org 132:229-239. https://doi.org/10.3354/dao03307

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