PARASITES COMMUNITY IN Chaetobranchus flavescens HECKEL , 1840 , ( CICHLIFORMES : CICHLIDAE ) FROM THE EASTERN AMAZON , BRAZIL

The aim of this study was to investigate the component communities of parasites in Chaetobranchus flavescens from a tributary of the Amazon River system, northern Brazil. Out of 39 fish examined, 1,124,710 parasites were collected, such as Ichthyophthirius multifiliis, Piscinoodinium pillulare (Protozoa), Gussevia spilocirra, Gussevia elephus (Monogenea), metacercariae of Clinostomum marginatum and Posthodiplostomum sp. (Digenea), Pseudoproleptus sp. larvae. (Nematoda), Echinorhynchus paranensis, Gorytocephalus spectabilis (Acanthocephala), Braga patagonica (Isopoda) and leeches Glossiphonidae (Hirudinea). However, I. multifiliis was the dominant and abundant species, while B. patagonica and Hirudinea gen. sp. were the least prevalent and abundant parasites. These parasites had an aggregate dispersion, with mean richness of 4.7 ± 1.5 per fish, Brillouin diversity of 0.32 ± 0.29 and evenness of 0.15 ± 0.13. No correlation between the length and the parasite species richness and the Brillouin diversity was found, as well as regarding host size and abundance of parasites. Body condition of the hosts was not affected by the moderate parasitism. The low diversity of endoparasites indicates that C. flavescens is a host with low position in the food web. Finally, this was the first study on parasites of C. flavescens.

model in evolutionary research (KOBLMÜLLER et al., 2012;VANHOVE et al., 2016).Cichlids fish are considered an ideal study system for evolutionary studies because of their remarkable species richness, high rates of speciation and often-high levels of endemicity, derived from diverse speciation and adaptive radiation.Moreover, they are important ornamental fishes and are among the most important protein sources in many parts of the world (VANHOVE et al., 2016) and many species have their great importance to aquaculture.Studies about cichlid adaptation mechanisms provides important information, generally applicable in evolutionary biology.Given their often-high degree of host specificity in cichlid species, some parasites, such monogenoideans, have been used as a potential tool to uncover host species relationships (KMENTOVÁ et al., 2016).
Chaetobranchus flavescens Heckel, 1840 is a Cichliformes that have distribution in South America including the Amazon River basin, in Peru and Brazil; Orinoco River basin in Venezuela (Apure River), and rivers of the Guyana and Suriname (KULLANDER, 2003;FROESE and PAULY, 2017).This benthopelagic fish inhabits mostly swamps or flooded grounds of coastal zones, either in turbid or clear stagnant water.This species of cichlid has importance in Amazonian fishery and is a zooplankton feeder, mainly of microcrustacean species (SOARES et al., 2011;FROESE and PAULY, 2017).In addition, due to its zootechnical characteristics, it is a cichlid species with great potential for management in controlled environments aiming at human nutrition and ornamental purposes.However, to allow breeding to become entirely feasible, it is necessary to know the diseases and parasites that can affect this species in natural environments to solve these problems of diseases aquaculture.
Despite the importance of C. flavescens to the ornamental aquaculture and fishery, this was not considered in the studies on parasitic ecology.However, parasites are representative components of global biodiversity, they have their community composition and structure influenced by biotic (e.g.host size, life mode of host, life cycle of parasite, etc.) and abiotic factors (POULIN, 2004a,b;MARCOGLIESE et al., 2006;SILVA et al., 2011;COSTA-PEREIRA et al., 2014).Thus, the aim of the present study was to evaluate the parasites community of C. flavescens from the Igarapé Fortaleza River, tributary from the Amazon River, northern Brazil.
The Igarapé Fortaleza basin is an important tributary of the Amazonas River system in State of Amapá, in the Brazilian eastern Amazon region, and it is in the estuarine coastal sector.It has a river system with extensive floodplains, constituting physical systems with clogged river, drained by freshwater and connected to a main watercourse.This tributary eutrophized by urbanization is widely used for refuge and feeding by many fish species (GAMA and HALBOTH, 2004;TAVARES-DIAS et al., 2013), including cichlid species.

Fish and locality of collection
From 2012 December to 2013 November, 39 specimens of C. flavescens (14.7 ± 3.7 cm and 72.8 ± 52.2 g) were collected in the Igarapé Fortaleza basin (Figure 1) for parasitological analysis.All fish were collected with nets of different meshes (10-40 mm).This study was developed in accordance with the principles adopted by the Brazilian College of Animal Experimentation (COBEA), with authorization from the Ethics Committee in the Use of Animals of Embrapa Amapá (# 004 -CEUA/CPAFAP) and ICMBio (# 23276-1).

Collection procedures and analyses of parasites
All fish were euthanized on ice, weighed (g) and measured for total length (cm), and then necropsied for parasitological analysis.Each specimen's mouth, opercula, gills and gastrointestinal tract were examined to collect parasites (protozoans and metazoans).Gills were removed, fixed in formalin (5%) and analyzed with the aid of a microscope.To quantify metazoan parasites, each viscera was dissected separately in Petri dish and was examined stereomicroscopically.Previously described techniques were used to collect, fix, conserve, count and stain the parasites for identification (EIRAS et al., 2006;BOEGER and VIANA, 2006).
To analyze the parasite infracommunities, the ecological terms used were those recommended by BUSH et al. (1997).
The following descriptors for the parasite community were calculated: the species richness, the Brillouin diversity index (HB), evenness (E) in association with diversity index, and the Berger-Parker dominance index (d) and dominance frequency (percentage of the infracommunities in which a parasite species is numerically dominant) (ROHDE et al., 1995;MAGURRAN, 2004), using the Diversity software (Pisces Conservation Ltd., UK).The variance-to-mean ratio (ID) and the index of discrepancy of Poulin (D) were calculated using the Quantitative Parasitology 3.0 software to detect the distribution pattern of parasite infracommunity (RÓZSA et al., 2000) for species with prevalence >10%.The ID significance for each infracommunity was tested using the d-statistics (LUDWIG and REYNOLDS, 1988).
Fish data on weight (g) and total length (cm) were used to calculate the relative condition factor (Kn) of hosts, which was compared to a standard value (Kn = 1.00) using the Mann-Whitney test (U).Body weight (g) and total length (cm) were used to calculate the relative condition factor (Kn) of fish using the length-weight relationship (W = aL b ) after logarithmic transformation of length and weight and subsequent adjustment of two straight lines, obtaining lny = lnA + Blnx (LE CREN, 1951).The Spearman correlation coefficient (rs) was used to determine possible correlations between parasite abundance, length and weight, as well as between the species richness and the Brillouin diversity of the hosts (ZAR, 2010).
No correlation between length (rs = -0.143,p = 0.386) and species richness of parasites and the Brillion diversity (rs = -0.088,p = 0.595) was found.In addition, predominance of hosts infected by 4 and 6 parasites was found (Figure 2).
The abundance of I. multifiliis showed no correlation between the length (rs = 0.125, p = 0.445) and weight (rs = 0.117, p = 0.480) of hosts.Also, the abundance of P. pillulare and its length (rs = -0.001,p = 0.994) and weight (rs = -0.036,p = 0.826) was not correlated.There was no correlation between the abundance

DISCUSSION
This first ecological survey reporting the parasite fauna of C. flavescens and parasite-host relationship showed that in this host there was a dominance of ectoparasites species, constituted by protozoans.Protozoans such as I. multifiliis and P. pillulare showed 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.Furthermore, aquatic environments favor the dispersion and survival of those ectoparasites with free-swimming stages during some phase of the life cycle (NEVES et al., 2013;TAVARES-DIAS et al., 2013).The Igarapé Fortaleza basin, environment of this study, located in the domain of an Amazon tropical rain forest is characterized by urban eutrophication (TAVARES-DIAS et al., 2014).However, the low richness of endoparasites indicates the C. flavescens as a host at the bottom in the food web, as as other Amazonian cichlid species such as Astronotus ocellatus Agassiz, 1831(NEVES et al., 2013) and Aequidens tetramerus Heckel, 1840 (TAVARES-DIAS et al., 2014).If we exclude such protozoan species from the present study, metacercariae of Posthodiplostomum Dubois, 1936 (Diplostomidae), becomes the most dominant species.Posthodiplostomum metacercarial stage has been reported in many freshwater fish around the world (ONDRACKOVA et al., 2002;RITOSSA et al., 2013;KARIMIAN et al., 2013).Lentic habitat is preferred by C. flavescens, which lives associated with roots of aquatic macrophytes, and this favors the colonization by these ectoparasites, and the encounter between their free-swimming larvae and the host (MARCOGLIESE et al., 2006;MORLEY, 2012).In addition, hirudineans and isopods were the least abundant species in the parasitic community structure of C. flavescens.
The lentic environment favors dispersal and reproduction of monogeneans, ectoparasites with free-living stages during some phases of its lifecycle (NEVES et al., 2013;TAVARES-DIAS et al., 2014).Monogeneans of Cichlidae species are known by high specificity (BRAGA et al., 2014), because they are well adapted to these hosts.Gussevia spilocirra and G. elephus are ectoparasites of different species of Amazon cichlids (KRITSKY et al., 1986).Gussevia spilocirra and G. elephus were found on gills of C. flavescens with higher infection levels than Gussevia alioides Kritsky, Thatcher and Boeger, 1986 and Gussevia disparoides Kritsky, Thatcher andBoeger, 1986 of A. tetramerus (TAVARES-DIAS et al., 2014).
In C. flavescens, infection levels by I. multifiliis and P. pilullare were similar to those reported for A. ocellatus (NEVES et al., 2013) and A. tetramerus (TAVARES-DIAS et al., 2014).These high infection levels by I. multifiliis and P. pilullare are influenced by the characteristics of the local environment.However, in C. flavescens the infection levels by metacercariae of Posthodiplostomum sp. in the gills were higher than by metacercariae of Clinostomum marginatum Rudolphi, 1819 (Clinostomidae), because this digenean endoparasite exhibits a heteroxenic life cycle involving biotic and abiotic factors (KLAAS, 1963;PINTO et al., 2013).The presence of these helminths species in C. flavescens, an omnivorous fish that feeds on microcrustacean species (SOARES et al., 2011;FROESE and PAULY, 2017) and mollusks, suggest that this cichlid acts as an intermediate host of both digenean species.In addition, the presence of C. marginatum metacercariae in intestine indicate that is possible that this fish feed also on other smaller fish, although this is not part of the diet of this fish.In South America, the life  For C. flavescens, the equation of weight (W)-length (L) relationship was Wt = 0.0515Lt 2.6468 , r 2 = 0.949), with negative allometric, indicating a greater increase in body weight than in size.The Kn of the hosts was not different from the standard value (Figure 3), indicating good body conditions despite parasitism that observed.cycle of C. marginatum involves Planorbidae mollusks of the genus Biomphalaria Preston, 1910 as first intermediate hosts, and bird eating-fish are definitive hosts and fish as C. flavescens are secondary intermediate hosts.Metacercariae of C. marginatum has been reported in more than 20 freshwater fish species from Brazil (PINTO et al., 2013), once they have no parasitic specificity.
Low infection by larvae of Pseudoproleptus Khera, 1955 (Cystidicolidae) were found in C. flavescens when compared to Satanoperca jurupari Heckel, 1840(MELO et al., 2011) and A. tetramerus (TAVARES-DIAS et al., 2014), both cichlid from the Amazon River system.Pseudoproleptus is a nematode with a life cycle that includes crustaceans such as the Amazon river prawn Macrobrachium amazonicum Heller, 1862 as a first intermediate hosts (MELO et al., 2011), while fish C. flavescens serve either as a definitive or paratenic hosts.However, infection by Pseudoproleptus sp.still is little known in Brazilian fish, and only recently these endoparasites were registered by the first time by MELO et al. (2011); hence, no species have been identified yet.
In fish populations, the acanthocephalan life cycle involves a definitive host and an intermediate host that could be an arthropod amphipod, ostracod or copepod.However, some species present the paratenic hosts (SCHMIDT, 1985;SILVA et al., 2011;TAVARES-DIAS et al., 2013) in their life cycle.Thus, the main factor regulating the prevalence and intensity of infection of acanthocephalan is the predation of the intermediate hosts and the presence of infection in the environment.Larvae and adults of acanthocephalans E. paranensis and G. spectabilis were found in the intestine of C. flavescens and in higher infection levels than those reported for A. tetramerus, infected only by G. spectabilis (TAVARES-DIAS et al., 2014).Therefore, such results indicate the C. flavescens as definitive hosts for these acanthocephalan species, which are not specific-host.
The influence of the host size in parasitic richness, diversity and abundance has been registered by various studies (POULIN, 1997(POULIN, , 2004a,b;,b;NEVES et al., 2013;TAVARES-DIAS et al., 2013).In contrast, for C. flavescens the body size can not play an important role in determining the infection susceptibility and development of parasites.Therefore, these results indicate that factors other than host body size are more important in determining the variations of abundance, diversity and species richness among the host population.This lack of relationship seem to be due to diet composition, direct life cycles of some more abundant parasites.In addition, environmental conditions could influence infection patterns in C. flavescens.In contrast, negative correlation between the body condition of Plagioscion squamosissimus Heckel, 1840 and the abundance of Ascaridoidea gen.sp. was reflected by the pathogenicity of the larvae of these nematodes, which can cause serious damage to host fish (LACERDA et al., 2012).The body condition of fish may be expressed by the condition factor, reflecting the recent length-weight relationship of the individual.The environment, food intake or even parasitism may influence the condition factor, depending on the intensity variation of these biotic and abiotic factors (SILVA et al., 2011;LACERDA et al., 2012;TAVARES-DIAS et al., 2013).However, the relative condition factor (Kn) requires a comparison with a standard value (Le Cren 1951).Findings of this study have shown that moderate infections levels not affected the body conditions of C. flavescens.

CONCLUSIONS
The component community of parasites in C. flavescens, an omnivorous host, was characterized by aggregated dispersion, low abundance of endohelminths, low species richness, low diversity and uniformity, presence of parasites in larval stage and a predominant species and presence of parasites of ectoparasites.Moreover, the hosts' size was not a factor that influenced the structure of the component community.This is the first record of all these parasites to C. flavescens.Finally, as few hosts were collected over a year, the samples number should be increased to evaluate the effects of seasonality on the infracommunities and community of parasites.

Figure 1 .
Figure 1.Collection locality of Chaetobranchus flavescens in Igarapé Fortaleza River, a tributary from the Amazon River system in eastern Amazon, northern Brazil.

Figure 2 .
Figure 2. Species richness of parasites in Chaetobranchus flavescens from the eastern Amazon, northern Brazil.

Figure 3 .
Figure 3. Relative condition factor (Kn) of Chaetobranchus flavescens from the eastern Amazon, northern Brazil.Box plots represent medians, interquartile ranges, minimum-maximum ranges and outliers.Values were not different according to the t-test (t = 6.084, p = 0.840).
P: Prevalence; MI: Mean intensity; MA: Mean abundance; TNP: Total number of parasites; SI: Site of infection.

Table 2 .
Dispersion index (ID), statistic-d and discrepancy index (D) for the parasites infracommunities of Chaetobranchus flavescens from the eastern Amazon, northern Brazil.
FD: Frequency of dominance.

Table 3 .
Descriptors of diversity for parasites communities of