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This study examined the metrics of the macroparasite community in fishes from the Jaguaribe River basin, state of Ceará, before and after receiving water from the São Francisco River in Northeastern Brazil. This research assessed the association of environmental factors (water parameters) and the traits of 30 fish species on the parasite richness and abundance across space (river course) and time (seasons, pre- and post-transposition periods). Generalized linear models reveal associations between parasite metrics and host traits, water parameters, and river sub-basin. Host size and body condition positively correlated with parasite richness and abundance, while reproductive phase was negatively related. Water quality impacted ecto- and endoparasites differently, with seasonal and sub-basins variations and differences among sub-basins. The general models also indicate that the period is a significant variable, where parasite richness decreases while abundance increases in the post-transposition period. This study underscores the importance of considering diverse environmental and host variables for understanding parasite dynamics in river ecosystems. These findings could lead to valuable insights for ecosystem management and conservation, elucidating the potential consequences of environmental alterations on parasite-host interactions and ecosystem health.

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Different groups parasitize the gills of fishes, and the organisms can interact in positive, negative, or neutral ways, depending on parasitic abundance, environmental conditions, and the availability of resources. Here, we studied the distribution of ectoparasites on the gills of the mullet Mugil curema in the Cabedelo port region (Brazil), asking if (1) the gill parasites of M. curema fix on specific host gill arches and/or (2) co-occur in the same gill arches within a host individual; (3) if the abundance of one parasite taxon affects the abundance of another on the same gill arches; and (4) considering distinct major groups, if parasites present patterns of co-occurrence on hosts and gill arches different from the expected at random. We used generalized linear models, generalized linear mixed models, and models with zero inflation to define the microhabitats (arches) with the highest abundances of parasites and null models to analyze the co-occurrences of gill parasite groups. Three taxa of Monogenea (Ligophorus brasiliensis Abdallah, Azevedo & Luque, 2009, Ligophorus sp. 1 and Ligophorus sp. 2) and six species of Copepoda were recorded (Bomolochus nitidus Wilson, 1911; Caligus praetextus Bere, 1936; Ergasilus atafonensis Amado & Rocha, 1997; Ergasilus bahiensis Amado & Rocha, 1997; Ergasilus caraguatatubensis Amado & Rocha, 1997 and Ergasilus lizae Krøyer, 1863). We found that, in general, the gill parasites were more abundant/prevalent on specific arches (I and II) of the hosts, shared such preferences and co-occurred on the gill arches. The presence of one taxon influenced the occurrence of another only in the arches I and II; as a result, the infracommunities were characterized as interactive in the gills of this host species.

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Bomolochidae Claus, 1875 is a copepod family with worldwide distribution that parasitizes marine fishes. This study provides the first report of Hamaticolax scutigerulus (Wilson, 1935) (Copepoda: Bomolochidae) in the spotted goatfish Pseudupeneus maculatus (Bloch, 1793), in the coastal waters of Pernambuco, northeastern Brazil. Prevalence of 35%, mean intensity of infestation of 1.9±1.3 and mean abundance of 0.7±1.2 were found. The setae and spines of the leg armor of the Hamaticolax species were analyzed to identify the present species.

Bomolochidae Claus, 1875, é uma família de copépodes cujas espécies encontram-se amplamente distribuídas pelo mundo e são parasitas de peixes marinhos. Este estudo relata, pela primeira vez, Hamaticolax scutigerulus (Wilson, 1935) (Copepoda: Bomolochidae) no saramunete Pseudupeneus maculatus (Bloch, 1793) do litoral de Pernambuco, nordeste do Brasil. Prevalência de 35%, intensidade média de infestação de 1,9±1,3 e abundância média de 0,7±1,2 foram observadas. As setas e os espinhos da armadura das pernas do parasito das espécies de Hamaticolax foram analisadas para identificar a presente espécie.

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Fish parasites are often related to some characteristics of their hosts, especially the length or age and the sex. The aims of the present study were to investigate the endoparasitic fauna of Rhaphiodon vulpinus and to test: (1) whether the parasitism is positively correlated with the standard length of the hosts; (2) parasitism levels in males and females, with the objective of detecting possible differences in the reproductive behaviour of the hosts. Samples of fish were taken from the floodplain of the upper Paraná River, from July 2004 to September 2008, quarterly; methodology for fish necropsy and fixation, conservation and preparation of parasites was based on specialized literature. The analysis of 39 hosts revealed that 15 fish were parasitized by at least one species of endoparasite. The species Contracaecum sp. (Nematoda) and Quadrigyrus sp. (Acanthocephala) were recorded, both at the larval stage. Considering both parasites, the prevalence and abundance of parasitism were not correlated with the standard length or the sex of hosts. From these results it is possible to infer that the length and the sex of the hosts had no influence on the immune response to infection, and that males and females present ecological similarities. This is the first record of the genera Quadrigyrus parasitizing R. vulpinus.

Os parasitas de peixes são frequentemente relacionados com algumas características de seus hospedeiros, especialmente o comprimento ou a idade e o sexo. O objetivo do presente estudo foi investigar a fauna endoparasitária de Rhaphiodon vulpinus e testar as hipóteses: (1) o parasitismo está correlacionado positivamente com o comprimento padrão dos hospedeiros, (2) detectar diferenças no nível de parasitismo entre hospedeiros machos e fêmeas. As amostras de peixes foram coletadas trimestralmente na planície de inundação do alto rio Paraná, entre 2004 à 2008; a metodologia para a necropsia de peixes e de fixação, conservação e preparação dos parasitas foi baseada na literatura especializada. A análise dos 39 hospedeiros revelou que 15 peixes estavam parasitados por pelo menos uma espécie de endoparasitas. As espécies Contracaecum sp. (Nematoda) e Quadrigyrus sp. (Acanthocephala) foram registradas, todas na fase larval. Considerando ambos os parasitas, a prevalência e a abundância de parasitismo não foram correlacionadas com o comprimento padrão ou o sexo dos hospedeiros. A partir desses resultados é possível inferir que o tamanho e o sexo dos hospedeiros não influenciaram na resposta imune à infecção, e que os peixes machos e fêmeas apresentam similaridades ecológicas. Este é o primeiro registro do gênero Quadrigyrus parasitando R. vulpinus.

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A new species of Demidospermus Suriano, 1983 is described from the gills of Auchenipterus osteomystax Miranda-Ribeiro, 1918 (Auchenipteridae), collected in the upper Paraná river floodplain, Brazil. The gills were removed and preserved in 5% formalin. Later the parasites were removed from the gills with the aid of a stereomicroscope and conserved in 70% alcohol. Some specimens were stained with Gomori’s trichrome, dehydrated in absolute alcohol and cleared with faia creosote to observe the internal organs. Other specimens were mounted in Hoyer’s medium for the study of the sclerotized structures. The present study describes a new monogenetic species, Demidospermus osteomystax n. sp., characterized by: tandem gonads; V-shaped haptoral bars with articulation; sinistral, non-sclerotized vagina; same-size anchors and absence of bulb in the cirrus.

Uma nova espécie de Demidospermus Suriano, 1983 parasita de brânquias de Auchenipterus osteomystax Miranda-Ribeiro, 1918 (Auchenipteridae) é descrita. Os peixes foram coletados na planície de inundação do alto rio Paraná, Brasil. As brânquias foram removidas e conservadas em formalina 5% e posteriormente os parasitas foram removidos com o auxílio de um esteromicroscópio e conservados em álcool 70%. Alguns espécimes foram corados com Tricômio de Gomori, desidratados em álcool absoluto e clarificados com creosoto de faia para a observação dos órgãos internos. Outros espécimes foram montados em Hoyer para estudo das estruturas esclerotizadas. O presente estudo descreve uma nova espécie de monogenético, Demidospermus osteomystax n. sp., caracterizada pela presença de gônadas em tandem; barras do haptor em forma de V, com articulação; vagina sinistra, não-esclerotizada; ancoras do mesmo tamanho e ausência do bulbo do cirro.

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