Low levels of crustacean parasite infestation in fish species from the Matapi River in the state of Amapá, Brazil

30, 2019 Abstract This first study investigated the crustacean parasite fauna in 66 species of fish from the Matapi River basin, state of Amapá (Brazil). Fish were collected every two months between March 2012 and August 2013, encompassing dry and rainy seasons. Among the 66 species examined (corresponding to 722 fish specimens) only 11 species were parasitized. The infestation prevalence was 2.2%, and a total of 48 specimens of parasites were distributed between three different parasite groups. These included Argulus elongatus , Dolops reperta and Argulus multicolor (Branchiura), Ergasilus xinguensis and Gamidactylus sp. (Copepoda), and Isopoda ( Braga patagonica ), but branchiuran species were predominant. This was the first report of these parasite species for Leporinus fasciatus , Astyanax bimaculatus , Curimata incompta , Pygocentrus nattereri , Crenicichla cincta , Crenicichla johanna , Geophagus camopiensis , Pterophyllum scalare , Plagioscion squamosissimus , Hypostomus plecostomus and Propimelodus eigenmanni . Lastly, this study expands the range of occurrence of these six parasite species to the Matapi River basin in

the rich ichthyofauna of the Matapi River, little is known about the diversity of crustacean parasites infesting these fishes.
Among crustaceans, there are many ectoparasites of fish. These are found in various habitats and require a host during at least one phase of their life cycle (MAMANI et al., 2004;TAVARES-DIAS et al., 2015;OLIVEIRA et al., 2017). Ergasilidae, Argulidae, Lernaeidae, Lernaeopodidae and Cymothoidae are the families most frequently found, and these infest the gills, oral cavity, nostrils and tegument of fish in Brazil. Parasitic crustaceans are just some of the ectoparasites taxa found on freshwater fish species in Brazil (TAVARES-DIAS et al., 2015). Many of these parasites have received significant attention because of the damage that they cause to fishery resources, which includes reduced fish growth, reproduction and host activities such as natation (MAMANI et al., 2004;TAVARES-DIAS et al., 2015). Some of these parasite crustaceans require specific fish as hosts and parasitize specific sites, particularly in fish with certain lifestyles, while other parasites do not have any preferences (TAVARES-DIAS et al., 2015;OLIVEIRA et al., 2017). Thus, some species of these ectoparasites have a broad pattern of distribution in different places, while others are restricted to certain geographical areas (TAVARES-DIAS et al., 2015) and host species.
The objective of the present study was to investigate the species of crustaceans infesting the gills of 66 species of fish in the Matapi River basin, in state of Amapá, northern Brazil.
Between March 2012 and August 2013, 66 species of fish were sampled every two months from the Matapi River (Table 1), in the municipality of Santana, state of Amapá, Brazil (Figure 1) for analyses on crustacean parasites in their gills, operculum and tegument. Fish were collected using gill nets of various mesh sizes (20,25,30,35,40 and 70 mm between knots), matapi traps, casting nets, hand lines and longlines, and the mean duration of fishing was 8 hours. Sampling was conducted in two seasonal periods: the dry period between July and November 2012 and in August 2013 (temperature of 28.3 ± 1.6 °C, pH 5.5 ± 0.7, electrical conductivity 3.1 ± 1.9 µS/cm, suspended solids 24.0 ± 22.5 mg/L, transparency 83.9 ± 55.3 cm and rainfall 100.5 ±128.1 mm); and the rainy period between March and May 2012 and between January and March 2013 (temperature of 27.6 ± 1.0 °C, pH 5.5 ± 0.6, electrical   The tegument and operculum of all the fish were examined at the collection site and the gills were then fixed in formalin (5%). The gills were removed and analyzed using a stereomicroscope. The crustaceans found were fixed in 70% ethyl alcohol with 10% glycerin (EIRAS et al., 2006) and were then identified (LUQUE et al., 2013;TABORDA et al., 2016). The ecological terms used were those recommended by Bush et al. (1997).
A total of 722 fish of 66 species were collected. Their length and weight are described in  (Table 1), and they were present in all sampling sites. The number of individuals collected was greater during the dry season, corresponding to 63% of the total sample.
The prevalence of crustacean parasites was 2.2% among the 722 fish of 66 species that were examined. Among the 48 parasite specimens collected, there was high abundance of three taxa (Branchiura, Copepoda and Isopoda) with diversity of six species (Table 2). Alsarakibi et al. (2014) reported that the density of argulids was lower in lotic environments such as rivers, in comparison with lentic environments such as fish farms.
Vasconcelos & Tavares-Dias (2016) studied the crustacean parasite fauna in six species of fish in a reservoir in the state of Amapá and reported prevalence of 30.4%. They collected 878 parasites, which included one species of Branchiura, one of Copepoda and one of Isopoda. Oliveira et al. (2017) reported that in 13 host species of the Jari River (state of Amapá), the prevalence of parasites was 63.8%; they collected 399 parasite specimens. However, the diversity of crustacean parasites and their levels of infestation can be influenced by various factors relating to the biology of parasites and hosts, and by environmental factors, among others (CARVALHO et al., 2003;MAMANI et al., 2004;FONTANA et al., 2012;ALSARAKIBI et al., 2014;MIKHEEV et al., 2015;VASCONCELOS & TAVARES-DIAS, 2016). Fish hosts may be are used by these parasites for transportation (CARVALHO et al., 2003), which could be facilitated by migrating fish species. However, this low prevalence of parasites in the hosts of the Matapi River may be due to the influence of daily tides from the Amazon River, considering that certain crustacean parasites respond to water movement to reach their hosts (MIKHEEV et al., 2015).
No crustacean parasites were found on the body surface of the fish from the Matapi River that were examined. However, among fish living in lotic environments, it is more difficult to estimate the prevalence of parasite crustaceans in the tegument when hosts are caught using fishing nets because these fish make strong movements and attempt to resist. Moreover, with time, the hosts' stress increases and their metabolism tends to decrease, which could stimulate these ectoparasites in the tegument of the fish to explore new habitats for their survival (BRANDÃO et al., 2013). Another factor that needs to be considered is the strong influence of diary tides from the Amazon River on the velocity of the Matapi River (CUNHA et al., 2011;SILVA et al., 2016), given that these parasites need to swim to find adequate hosts, while others depend on the flow of water and swimming speed (FONTANA et al., 2012;MIKHEEV et al., 2015).
Among the hosts in the Matapi River, Argulidae species predominated. Among these, Argulus elongatus Heller, 1857, and Dolops reperta Bouvier, 1899, were the most prevalent. However, Ergasilus xinguensis Taborda  are known for frequently switching hosts and for having lower host specificity than that of other parasite groups. Among the factors that influence the infestation rates of these ectoparasites are the genetic similarities of the hosts and ecological factors that may be involved (MAMANI et al., 2004;OLIVEIRA et al., 2017). To conclude, in 66 host species, the rates of infestation with crustacean parasites were low, and most of the fish examined had low abundance of parasites, except C. johanna and G. camopiensis. Lastly, this study reports these fish species as new hosts for the crustacean parasites species that were found and expands the range of occurrence of the six parasite species to the Matapi River basin in eastern Amazon (Brazil).