Seasonal Influence on the Parasite Fauna of a Wild Population of Astronotus ocellatus (Perciformes: Cichlidae) from the Brazilian Amazon

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1 Seasonal Influence on the Parasite Fauna of a Wild Population of Astronotus ocellatus (Perciformes: Cichlidae) from the Brazilian Amazon Author(s): Lígia R. Neves, Felipe B. Pereira, M. Tavares-Dias, and José L. Luque Source: Journal of Parasitology, 99(4): Published By: American Society of Parasitologists DOI: URL: BioOne ( is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne s Terms of Use, available at Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research.

2 J. Parasitol., 99(4), 2013, pp Ó American Society of Parasitologists 2013 Seasonal Influence on the Parasite Fauna of a Wild Population of Astronotus ocellatus (Perciformes: Cichlidae) from the Brazilian Amazon Lígia R. Neves, Felipe B. Pereira*, M. Tavares-Dias, and José L. Luque, Laboratório de Aquicultura e Pesca, Embrapa Amapá, Caixa Postal 10, CEP , Macapá, AP, Brazil; *Curso de Pós-Graduação em Ciências Veterinárias, Universidade Federal Rural do Rio de Janeiro, CEP , Seropédica, RJ, Brazil; Departamento de Parasitologia Animal, Universidade Federal Rural do Rio de Janeiro, Caixa Postal 74508, CEP , Seropédica, RJ, Brazil. Correspondence should be sent to: luqueufrrj@gmail.com ABSTRACT: Parasite infracommunities were studied in 202 specimens of Astronotus ocellatus collected from a freshwater lake in the State of Amapá, northern Brazil. Relationships between some host attributes (i.e., ontogeny, sex, and body size) and parasite infections were analyzed, but the primary focus was the seasonal variation in the parasite fauna. In total, 6,308,912 parasites belonging to 11 different taxa were found. Protozoa were the most abundant and dominant taxa, but monogeneans, trematode metacercariae, and nematode larvae were also prevalent and abundant. Fish ontogeny had a weak influence on parasite infection rates; juveniles were more parasitized by Dolops nana and Posthodiplostomum sp. The abundances of all parasite species were weakly correlated with host body size (low r 2 values), except D. nana, Contracaecum sp., and Posthodiplostomum sp., which exhibited no correlation between abundance and host body size. Prevalence and abundance were different between flood and drainage seasons for all parasite species, except for D. nana and the 2 metacercarial species. Astronotus ocellatus may represent a link in food-web transmissions for parasites because it is used both as definitive and intermediate host. The parasite fauna of A. ocellatus was composed primarily of ectoparasites, and this could be considered typical of fishes that inhabit lentic waters. Seasonality was a strong determinant in the parasite community structure. The Amazon rain forest biome is composed of a series of environments, several of which exhibit marked seasonal variations based on flood and drainage periods (Moraes et al., 2005; Cunha et al., 2010). This seasonal pattern is annual and, together with fish attributes such as sex, age, body size, behavior, and feeding habits, may clearly affect a parasite community structure (Wootten, 1973; Leong and Holmes, 1981; Price and Clancy, 1983; Kennedy and Bush, 1994). The Oscar Astronotus ocellatus (Agassiz, 1831) (Perciformes: Cichlidae) is native to rivers and lakes of the Amazon Basin (Pavanelli, 2000), but it is also found in drainage basins in northeastern, southeastern, and southern Brazil as an introduced species, due to its great economic value (Azevedo et al., 2007) and trophic plasticity (Firouzbakhsh et al., 2011). In nature, A. ocellatus individuals are commonly found in shaded lentic areas of calm and clear waters, where they can seek shelter under submerged branches (Azevedo et al., 2007; Soares et al., 2008). This species has the capacity to ambush and capture prey, which are mainly small fishes, crustaceans, gastropods, and larvae of aquatic insects (Santos et al., 2006; Azevedo et al., 2007; Soares et al., 2008). Studies addressing ecological aspects of the parasite fauna from A. ocellatus in Brazilian waters are still scarce, with only 1 survey from a natural habitat of the Amazon (Malta, 1984), and 1 of introduced fishes from the Guandu River in the State of Rio de Janeiro (Azevedo et al., 2007). As a result, the present investigation was conducted to evaluate the seasonal influence on the parasite community structure of a wild population of A. ocellatus collected in a lake from the Brazilian Amazon, as well its relationship with some of the host attributes. DOI: / Fishes were collected monthly with gillnets in the northern portion of Pracuúba Lake ( N, W), located in the municipality of Pracuúba, State of Amapá, northern Brazil, and kept in thermal boxes filled with ice prior to examination. The local climate is typical of the tropical rain forest, with maximum rainfall rates in summer and spring (December to May) and minimum rainfall rates in winter and autumn (June to November) (Souza and Cunha, 2010), consisting of 2 seasonal periods (i.e., flooding and drainage). In total, 202 (115 females, 73 males, and 14 juveniles) fishes were sampled over 12 mo (May 2010 to April 2011), 93 during flooding and 109 in the drainage season. Fishes were measured for total length (L T ), weighed, sexed, and then examined first for ectoparasites (skin, mucus, eyes, gills, and mouth cavity) and afterward for endoparasites (all visceral organs, blood vessels, and body cavity). The methods described by Eiras et al. (2006) were used to detect and quantify protistan parasites. To quantify metazoan parasites, each organ was dissected separately and washed in running water. All material retained on a 154-lm mesh was examined under a stereomicroscope. Parasites were fixed, preserved, and stained using standard techniques (Amato et al., 1991; Eiras et al., 2006). Voucher specimens were deposited at Instituto de Pesquisas Cient ıficas e Tecnológicas do Estado do Amapá (IEPA)/ Curadoria das Colec oes Cient ıficas, Fauna do Amapá (CCFA) (accession numbers: IEPA 001-P to IEPA 008-P). The parasitological terminology used throughout follows that described by Bush et al. (1997). Prevalence, abundance, and mean abundance were calculated and used for the analysis of the parasite community. Statistical analyses were performed only for those parasite species with a greater than 10% prevalence rate. The variance-to-mean ratio of parasite abundance (dispersion index) and discrepancy index (Poulin, 1993) were computed using the Quantitative Parasitology 3.0 software program and employed to detect distribution patterns of the parasite infracommunities (Ro zsa et al., 2000). The following community descriptors were calculated on the parasite infracommunity level: number of parasite individuals (total abundance), species richness, and frequency of dominance (percentage of infracommunities in which a parasite species was numerically dominant) (Magurran, 1988; Rohde et al., 1995). Linear regression analysis was performed to evaluate the association between fish weight and L T. One-way ANOVA, followed by a post hoc Tukey test, was used to compare the L T values among male, female, and juveniles of A. ocellatus (Zar, 1999). Possible differences in prevalence, abundance, and species richness among juvenile, male, and female fishes were evaluated with ANOVA, followed by a post hoc Tukey test (Zar, 1999). Abundance and species richness were log-transformed (log 10 [x þ 1]), and prevalence was arcsine-transformed (Zar, 1999). Seasonal variations in prevalence were evaluated by a logistic regression (Dohoo et al., 2003); the same variations in abundance and species richness were evaluated by a Poisson regression model (Dohoo et al., 2003). A linear regression analysis was employed to evaluate the relationship between parasite abundance (log-transformed) and fish L T, as well species richness (log-transformed) and fish L T (Zar, 1999). All means are followed by standard deviation (6SD) values. Statistical tests were performed using the SYSTATt and R program with the Vegan package included (Wilkinson, 1990; Oksanen et al., 2007). The significance level was set to 5% (P, 0.05). 718

3 RESEARCH NOTES 719 TABLE I. Site of infection (SI), prevalence (Prev.), mean 6 SD abundance (MA), variance-to-mean ratio (ID), index of discrepancy (D), and frequency of dominance (FD) of the parasites collected from Astronotus ocellatus in State of Amapá, northern Brazil. Parasite species SI Prev. (%) MA ID D FD (%) Protozoa Ichthyophthirius multifiliis Gills , ,536 7,073.5 * 87.2 Piscinoodinium pillulare Gills , ,290 9,458.0 * 2.1 Trichodina sp. Gills Monogenea Gussevia asota Gills Gussevia astronoti Gills Gussevia rogersi Gills Digenea Herpetodiplostomum sp. metacercariae Gills Posthodiplostomum sp. metacercariae Gills Nematoda Contracaecum sp. larvae Mesenteries Branchiura Dolops nana Gills Hirudinea Glossiphoniidae gen. sp. Gills * Sample size too large, precluding calculation. Fish weight was positively associated with L T (r 2 ¼ 0.8, P, 0.001). Females (L T ¼ 2, mm, 1,600 to 2,900 mm) were larger than males (L T ¼ 2, mm, 1,700 to 2,900 mm) (P ¼ 0.02) and juveniles (L T ¼ 2, mm, 1,500 to 2,920 mm) (P ¼ 0.01); males and juveniles did not differ in body size (P ¼ 0.36). In total, 6,308,912 parasites were collected. The specimens belonged to 11 different taxa: 3 Protozoa, 3 Monogenea, 2 Digenea metacercariae, 1 larval Nematoda, 1 Branchiura, and 1 Hirudinea (Table I). Among the entire fish sample, 92.0% were parasitized by at least 1 species. The protist Ichthyophthirius multifiliis (Fouquet, 1866) (Ciliophora: Ichthyophthiriidae) was the most prevalent, abundant, and dominant species. Hirudinea species had the lowest prevalence rate and was the only parasite taxon excluded from the statistical analysis. The least abundant species was Dolops nana Lemos de Castro, 1950 (Branchiura: Argulidae). All parasite species exhibited an aggregated distribution pattern (Table I), with mean richness of (0 to 9) per fish. Species richness did not differ among juveniles (P ¼ 0.60), male (P ¼ 0.94), and female (P ¼ 0.98) fishes, nor between seasons (P ¼ 0.18). Dolops nana was more prevalent in juveniles than in adults (P ¼ 0.02); Posthodiplostomum sp. was more prevalent (P ¼ 0.02) and abundant (P ¼ 0.002) in juveniles than in adults. All protists and the nematode Contracaecum sp. were more abundant and prevalent during the flood season (Table II); all monogenean species were more abundant and prevalent during the drainage season (Table II); the infection rates of the 2 digenean metacercariae Herpetodiplostomum sp. and Posthodiplostomum sp., and of the crustacean D. nana were not seasonally different (Table II). Fish L T was weakly and positively correlated with the abundance for all parasite species, except for Contracaecum sp., D. nana, and Posthodiplostomum sp. (Table II), and L T was positively correlated (weak correlation) with species richness (r 2 ¼ 0.028, P ¼ 0.017). This is the first ecological survey reporting the complete parasite fauna of A. ocellatus from a natural habitat in Brazil, and its seasonal variations. Moreover, this is the first record of Ichthyophthirius multifiliis, Pscinoodinium pillulare (Schaperclaus, 1954) (Dinoflagellida), Dolops nana, metacercariae from Posthodiplostomum and Herpetodiplostomum, and the protist genus Trichodina parasitizing A. ocellatus in Brazil. The component community of parasites in the present work exhibited an aggregated pattern of distribution, which is very common among parasite component communities (Crofton, 1971; Poulin, 1993), mitigating harm to host populations and reducing interspecific competition among parasites (Ewald, 1995; Zuben, 1997). It is clear that protists, especially I. multifiliis and P. pillulare, exhibited a much higher parasite burden than the other species, perhaps due to the small size, low specificity, and high reproductive and infection rates among such parasites (Pavanelli et al., 2008; Tavares-Dias et al., 2001). Furthermore, aquatic environments favor the dispersion and survival of those ectoparasites with free-swimming stages during some phase of the life cycle (Dogiel, 1961; Malta, 1984). That is why adult monogenean and digenean metacercariae were also prevalent. Malta (1984) analyzed the crustacean parasites of a wild population of A. ocellatus in the Amazon; he found 3 Dolops spp. and 1 Argulus sp., with low prevalence values similar to that found for D. nana in the present study. In contrast, Azevedo et al. (2007) reported the monogenean Gusseiva sp. as the most prevalent and dominant species from A. ocellatus introduced in a river in Rio de Janeiro, whereas immature forms such as nematode larvae of Contracaecum sp. and the cystacanth of Polymorphus sp. were much less prevalent; protists were not studied. If we exclude the protists from the present work, the monogenean Gussevia asota Kritsky, Tatcher and Boeger, 1989 becomes the most prevalent and dominant species, followed by the 2 metacercariae species, and then by Contracaecum sp. larvae. Monogeneans of the genus Gussevia are well adapted to this host (Azevedo et al., 2007; Abdallah et al., 2008). In addition, the lentic habitat preferred by A. ocellatus favors the colonization by ectoparasites, and also the encounter between their free-swimming larvae and the host (Dogiel, 1961). Hirudinean and crustaceans seem to be the least abundant species in the parasite community structure of A. ocellatus, as reported here, and also by Azevedo et al. (2007). Sex differences did not appear to influence the parasite community structure, probably because male and female fishes share the same type of habitat and have similar feeding habits and behavior (Braga, 1962). However, D. nana was more prevalent in juvenile fishes, and Posthodiplostomum sp. was more prevalent and also more abundant in juvenile fishes. Young individuals of A. ocellatus are more vagile than adults

4 720 THE JOURNAL OF PARASITOLOGY, VOL. 99, NO. 4, AUGUST 2013 TABLE II. Regression analysis between fish L T (mm) and parasite abundance (log transformed), differences in prevalence (Prev.), and mean abundance 6 SD (MA) during the flood and drainage seasons, evaluated by logistic and Poisson models, respectively, for the parasites collected from Astronotus ocellatus in State of Amapá, northern Brazil. Parasite species Fish L T 3 abundance Drainage season Flood season Logistic Poisson r 2 * P* Prev. (%) MA Prev. (%) MA P P Ichthyophthirius multifiliis , , , , ,0.001 Piscinoodinium pillulare , , , , ,0.001 Trichodina sp ,0.001,0.001 Gussevia asota ,0.001,0.001 Gussevia astronoti ,0.001 Gussevia rogersi ,0.001,0.001 Herpetodiplostomum sp Posthodiplostomum sp Contracaecum sp , Dolops nana * r 2 ¼ coefficient of determination; P ¼ significance values. (Braga, 1962), which may increase the probability of encounter between these individuals and D. nana and Posthodiplostomum sp. in that case. Parasite abundance and species richness increased with the increase of host body size for most of the species, which agrees with some authors that consider hosts as islands for parasite colonization (Kellog, 1913; Janzen, 1968, 1973), using the analogy from island biogeography theory (MacArthur and Wilson, 2001). However, these correlations were very weak, as evidenced by extremely low values of r 2 (body size explained less than 10% of variance on parasite abundance and species richness). Thus, this indicates that factors other than host body size are more important determinants of variations of abundance and species richness among the host population. This also explains the lack of relationship between abundance of Contracaecum sp., D. nana, and Posthodiplostomum sp. and host body size. Diet composition may be important for Contracaecum sp. infection, since it is a heteroxenous nematode with hosts related to foodweb links; in the case of D. nana and Posthodiplostomum sp., which exhibit direct life cycles, environmental conditions could influence infection patterns. Pracuúba Lake is located in the domain of an Amazon tropical rain forest, which is characterized by 2 distinct seasons during a year, i.e., 1 flood period when the lakes are expanded and 1 drainage period when they remain much more reduced (Souza and Cunha, 2010). Our data show an accentuated seasonal influence in the parasite community structure, but this seasonality affects each parasite group in different ways. First, species richness was statistically similar between seasons, perhaps indicating that these parasites can, at least, infect the host independent of seasonal variations; parasite prevalence and abundance were seasonally different. Second, all protozoan species and Contracaecum sp. were more abundant and prevalent during flood season; in the case of protists, it is probable that chemical and physical variables of water (i.e., temperature, dissolved oxygen, ph, and turbulence) act on their demographic patterns (Pavanelli et al., 1997), since the intense variation in water levels at the lake may affect its physicochemical properties. Seasonal variation in the infection patterns of Contracaecum sp. may be related to the abundance of intermediate hosts for this parasite (i.e., small crustaceans), which are eaten by the fish. Furthermore, a decrease in water volume is known to cause nutritional imbalances, reducing the production of food in general (Madanire-Moyo et al., 2011). Lastly, the infection rates of monogenean species were higher during the drainage period; parasite infection is favored by reduced water levels, concentrating parasites and hosts, and increasing the probability of infection, since they have a simple direct life cycle (Madanire-Moyo et al., 2011). The 2 larval digeneans exhibited similar prevalence and abundance between seasons, probably because they have a complex life cycle, with low specificity of intermediate hosts and asexual reproduction, where a single miracidium results in a large number of free-swimming cercariae. This complexity of life cycle may overshadow seasonal variations in that case. This ecological survey is the first pass to understand patterns and processes of parasite infections in wild populations of A. ocellatus. Considering the complexity and diversity of the Amazonian ecosystems that are occupied by this fish, similar investigations need to be conducted in the future for a better understanding of the factors that determine these patterns and processes. Felipe B. Pereira was supported by a graduate fellowship from the CAPES (Coordenacão de Aperfeicoamento de Pessoal de N ıvel Superior). José L. Luque was supported by a fellowship from the CNPq (Conselho Nacional de Desenvolvimento Cient ıfico e Tecnolo gico, Brazil). LITERATURE CITED ABDALLAH, V. D., R. K. AZEVEDO, AND J. L. LUQUE Notes on the morphology of two species of Gussevia Kohn & Paperna (Monogenea: Dactylogyridae) parasitic on Astronotus ocellatus (Agassiz) (Perciformes: Cichlidae) from Brazil. Pan-American Journal of Aquatic Sciences 3: AMATO, J. F. R., A. B. WALTER, AND S. B. AMATO Protocolo para laboratório. Coleta e Processamento de Parasitas do Pescado, 1st ed. 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