Morphological and molecular characterization of Hysterothylacium spp. parasitizing Pomatomus saltatrix and Pagrus pagrus of the State of São Paulo, Brazil.

Raphidascarid nematodes have been the focus of several studies, mainly due to the zoonotic potential of some species, even though the cases are underreported. Due to the difficulty in identifying their larvae, the use of diagnostic techniques involving morphological and molecular analyses has grown in the last 20 years. The present study had as objective the morphological and molecular characterization of the L3 larval types of Hysterothylacium collected in Pomatomus saltatrix and Pagrus pagrus from the Brazilian coast, close to the municipality of Santos, State of São Paulo. Twenty specimens of P. saltatrix were necropsied and Hysterothylacium type V (n = 257) and Hysterothylacium type X (n = 5) larvae were found. Five specimens of P. pagrus were necropsied and all were parasitized by Hysterothylacium type V larvae. The analyses showed a genetic proximity relationship between Hysterothylacium types V with other Hysterothylacium V and with H. deardorffoverstreetorum, although this is a species inquirenda. Haplotypes for Hysterothylacium type X found in the present study formed a monophyletic group with other Hysterothylacium X, H. amoyense, and H. zhoushanense. Through this study, new hosts and localities were registered for Hysterothylacium type V and Hysterothylacium type X.

Qualitative and quantitative study of parasites of Pimelodus maculatus and Rhamdia quelen from the Jacaré-Pepira River, state of São Paulo, Brazil.

In the freshwater ecosystems of Brazil can be found high biodiversity of fish, about 5160 species. However, the Jacaré-Pepira River, located in the state of São Paulo, Brazil, presents a diversity of fish still to be explored in ichthyological studies. Metazoan parasites of Pimelodus maculatus and Rhamdia quelen were qualitatively and quantitatively diagnosed. Ten species of parasites (Demidospermus sp., D. majusculus, D. bidiverticulatum, D. paravalenciennesi, Ameloblastella paranaensis, Scleroductus sp., Riggia sp., Austrodiplostomum compactum, Helobdella sp. and Neochinorhynchus pimelodi) were collected in P. maculatus and eight species of parasites (Aphanoblastella robustus, A. mastigatus, Phyllodistomum rhamdiae, Crocodilicola pseudostoma, Henneguya jundiai, Contracaecum sp., Rhabdochona sp. and Capillariidae gen. sp.) were collected in R. quelen. All parasites presented aggregate distribution. A significant correlation was observed in P. maculatus concerning the weight with the prevalence of ectoparasite D. majusculus; however, R. quelen showed a relation to the length and weight with the abundance of ectoparasite A. mastigatus and endoparasites. The parasitic community of P. maculatus and R. quelen was characterized by high diversity, high richness, and low uniformity.

Biodiversity of parasites found in the trahira, Hoplias malabaricus (Bloch, 1794), collected in the Batalha River, Tietê-Batalha drainage basin, SP, Brazil.

Eighty-one Hoplias malabaricus specimens were collected between February 2014 and June 2016. A total of 29 species of metazoan parasites were found, 13 of which were identified as monogeneans, seven were digenean species, seven of which were nematodes, and two of which were from the subclass Hirudinea. The highest prevalence values ​​were presented by Contracaecum sp. and Tylodelphys sp. The highest mean abundance and mean intensity was recorded by Tylodelphys sp.; the values were ​​36.7 ± 61.8 and 55.65 ± 69.1, respectively. The abundance of the monogenean Urocleidoides cuiabai was found to be positively correlated with host weight. The abundance of Bucephalidae gen. sp. exhibited significant positive correlations with host weight and length. For Contracaecum sp., a significant negative correlation was found between its abundance and host length and weight. No significant differences between the diversity indexes (Margalef, Pielou and Shannon) of the parasites collected in the two points were found. The Sorensen similarity index, with a value of 0.82 between the two sampling points revealed that the parasitic diversity between them is similar. The findings from this study represent new records of occurrence of H. malabaricus, as well as of Urocleidoides margolisi, Scleroductus sp. and Helobdella sp.

Helminth parasites of Cichla ocellaris Bloch & Schneider, 1801 collected in the Jacaré-Pepira River, São Paulo state, Brazil.

Cichla ocellaris is native to the Amazon region. It is popularly known as tucunaré and is widely used for human consumption. It is difficult to breed in captivity due to its highly predatory habits, it is considered symbolic of sport fishing in Brazil. This study aimed to make a qualitative and quantitative survey of helminth parasites of C. ocellaris. Thirty specimens from the Jacaré-Pepira River, located in the municipality of Ibitinga, in the interior of the state of São Paulo, were studied. The river is located 13 km from the urban area and at an altitude of approximately 600 m. A total of four taxa of metazoan parasites were collected and identified in Cestoda, Digenea, Monogenea and Nematoda. The cestoid Proteocephalus macrophallus presented the highest prevalence (63.3%) and had the greatest abundance and intensity, being found only in the intestine and stomach. The parasites found showed a significant positive correlation between the total body length of the hosts and the prevalence, as did the weight. This is the first study of helminth parasites of this host conducted in the Jacaré-Pepira River and the first record of a new location for P. macrophallus.

Parasitic communities of Hoplosternum littorale (Hancock, 1828) as indicators of environmental impact.

The parasites are indicative of several biological aspects of their hosts, including their diet, migration, recruitment and phylogeny, but they can also be direct indicators of the environmental quality. Hoplosternum littorale is a fish that has a high commercial value in some South American countries. The fishes were collected from January to July 2012, in two locations of the Peixe River in the municipality of Anhembi, State of São Paulo, Brazil, which had different environmental and limnological characteristics (river mouth and Lagoa Cabeça de Boi). An amount of 30 fish specimens were captured in each location for the analysis of their parasitic fauna. Nine species of metazoan parasites were collected. Both Brillouin`s diversity index and Margalef`s richness index were greater in the Lagoa Cabeça de Boi. The ratio of heteroxenous and monoxenous parasite species richness (SH/SM) was higher in the Lagoa Cabeça de Boi. The results of the physicochemical analysis of the water showed that the mouth of the Peixe River can be considered an area that suffers more from anthropogenic actions than the Lagoa da Cabeça de Boi. Proteocephalus sp., Gyrodactylus sp., Scleroductus sp. and Capillaria (Neocapillaria) pterophylli are being registered for the first time in this host.

Contracaecum sp. parasitizing Acestrorhynchus lacustris as a bioindicator for metal pollution in the Batalha River, southeast Brazil.

Pollution in aquatic ecosystems due to negative human activities remains a problem in both freshwater and marine environments and is an ongoing subject of research. Several studies have shown that some fish parasites can be used as a tool for biomonitoring because they demonstrate higher metal accumulation capacity compared to their host tissues. However, compared to acanthocephalans, information regarding the absorption mechanisms and accumulation rates in nematodes is relatively limited. Here, we evaluated the potential of larvae Contracaecum sp. (L3) as indicators of contamination by metals by analyzing thirteen element concentrations: magnesium (Mg), aluminum (Al), titanium (Ti), chromium (Cr), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), barium (Ba), and lead (Pb) in the parasites and host Acestrorhynchus lacustris, using inductively coupled plasma mass spectrometry. Twelve of the thirteen analyzed elements were detected in at least 2-fold higher concentrations (e.g. Ni) and were up to approximately 50-fold higher (e.g. Pb) in parasites than in host tissues, including elements known for their high toxicity (As, Cd, Pb) and those considered to be essential (Cu and Zn). Our results suggest that Contracaecum sp. larvae can be used as bioindicators of metal contamination because even in early stages of development, numerous essential and non-essential elements were accumulated, making this system a useful tool for monitoring polluted environments.

Parasitic communities of Hoplosternum littorale (Hancock, 1828) as indicators of environmental impact

ABSTRACT The parasites are indicative of several biological aspects of their hosts, including their diet, migration, recruitment and phylogeny, but they can also be direct indicators of the environmental quality. Hoplosternum littorale is a fish that has a high commercial value in some South American countries. The fishes were collected from January to July 2012, in two locations of the Peixe River in the municipality of Anhembi, State of São Paulo, Brazil, which had different environmental and limnological characteristics (river mouth and Lagoa Cabeça de Boi). An amount of 30 fish specimens were captured in each location for the analysis of their parasitic fauna. Nine species of metazoan parasites were collected. Both Brillouin`s diversity index and Margalef`s richness index were greater in the Lagoa Cabeça de Boi. The ratio of heteroxenous and monoxenous parasite species richness (SH/SM) was higher in the Lagoa Cabeça de Boi. The results of the physicochemical analysis of the water showed that the mouth of the Peixe River can be considered an area that suffers more from anthropogenic actions than the Lagoa da Cabeça de Boi. Proteocephalus sp., Gyrodactylus sp., Scleroductus sp. and Capillaria (Neocapillaria) pterophylli are being registered for the first time in this host.

The patterns of organisation and structure of interactions in a fish-parasite network of a neotropical river.

The use of the complex network approach to study host-parasite interactions has helped to improve the understanding of the structure and dynamics of ecological communities. In this study, this network approach is applied to evaluate the patterns of organisation and structure of interactions in a fish-parasite network of a neotropical Atlantic Forest river. The network includes 20 fish species and 73 metazoan parasite species collected from the Guandu River, Rio de Janeiro State, Brazil. According to the usual measures in studies of networks, the organisation of the network was evaluated using measures of host susceptibility, parasite dependence, interaction asymmetry, species strength and complementary specialisation of each species as well as the network. The network structure was evaluated using connectance, nestedness and modularity measures. Host susceptibility typically presented low values, whereas parasite dependence was high. The asymmetry and species strength were correlated with host taxonomy but not with parasite taxonomy. Differences among parasite taxonomic groups in the complementary specialisation of each species on hosts were also observed. However, the complementary specialisation and species strength values were not correlated. The network had a high complementary specialisation, low connectance and nestedness, and high modularity, thus indicating variability in the roles of species in the network organisation and the expected presence of many specialist species.