Ornamental fish mortality reveals an old parasite introduction: A case study of Koi carp and fish louse.

Koi carp are globally known for their colors and cultural significance. The introduction of these fish to new environments poses a threat to local biodiversity, in addition to releasing parasites, such as argulid ectoparasites. This study presents a record of Argulus japonicus infecting carp in an artificial lake in Southern Brazil using morphological and molecular methods, with a 100% prevalence (n = 3) and a mean intensity of 21.6 parasites per host, distributed over the body surface. The invasion history of hosts in the study locality indicates that the introduction of A. japonicus occurred decades before its first formal record in Brazil.

The functional traits of host fish can act as good predictors for parasite composition in a neotropical floodplain.

Parasite diversity can be influenced by the interaction of environmental factors and host traits, but understanding which traits can be decisive for the establishment of the parasite may provide subsidies for a better understanding of the host-parasite relationship. In this study, we investigated whether functional traits, diet, and host phylogeny can predict the similarity of the endoparasite composition of a fish assemblage in a Brazilian floodplain. Of the three evaluated components, the host's diet was the factor that showed the greatest influence on the composition and similarity of endoparasites, demonstrating the highest value of the explanation. The functional traits and phylogeny, despite presenting significant values (unique effect and global effect), showed low explainability in the composition of the endoparasites. When analyzing the joint effects, all components showed significant influence. Hosts that live in the same environment that are phylogenetically related and have a similar ecology have a certain degree of homogeneity in their parasite assemblages and, because they are endoparasites (which are acquired trophically along the chain), diet is the main driver of parasite richness and similarity. Overall, host traits can be one of the main determinants of parasite composition, so studies that address the functional traits of the host provide a representation of local diversity and define the possible patterns of these parasite communities.

First record of two Copepoda species parasitizing Colomesus tocantinensis (Tetraodontiformes: Tetraodontidae) in the Tocantins-Araguaia basin, Brazil.

Considering the lack of studies on freshwater fishes of the genus Colomesus, we conducted a survey the parasite fauna of Colomesus tocantinensis collected from the Tocantins River, Brazil. We first recorded the presence of the ectoparasites Ergasilus colomesus and Lernaea sp. where 96.77% of the fish were parasitized.

Components influencing parasitism by Dadaytrema oxycephala (Digenea: Cladorchiidae) in Neotropical fish.

The components that mold the structure of parasitic fauna are used as objects of study in an attempt to find patterns in their distribution. It is known that phylogeny (represented by specificity), host ecological traits (for example, feeding habits, position of the water column, reproductive strategies, body size, and age), and the environment affect the distribution and occurrence of parasites. In tropical regions, digeneans show high diversity, and the species Dadaytrema oxycephala is known to parasitize a wide range of host species. In this context, the objective of the present study is to analyze the components that affect the occurrence of D. oxycephala in Neotropical fish. We used data from the literature that contained the abundance of this parasite, as well as the geographic location and host species, and evaluated the influence of ecological traits, specificity, and latitude on parasite abundance, using a generalized linear mixed model (GLMM). The abundance of D. oxycephala can be explained by trophic level and position in the water column and latitude. However, coevolutionary processes are also extremely important, and the distribution of this parasite was not equal, showing high abundance for the genus Piaractus, which are the preferred hosts, even if the parasite is considered generalist. In short, host ecological traits are the important components in the distribution and occurrence of D. oxycephala, as well as the latitude.

Effect of burrowing cymothoid parasitism on loricariids.

Cymothoids belong to the order Isopoda and are ectoparasites of fishes, and their main parasitism strategies are by penetrating, burrowing, and lodging in the abdominal cavity of the hosts. Due to this complex parasitism strategy, they are considered highly host-specific parasites. We investigated the effects of parasitism of the burrowing cymothoid Artystone sp. on the loricarids Hisonotus chromodontus and Curculionichthys luteofrenatus in the Selma stream, a tributary of the Teles Pires river, Southern Amazon. The hypothesis under study is that parasitism causes negative effects on the feeding, reproduction, and length-weight relationship of the hosts. The presence of alternative hosts was also investigated. The parasitic interaction of Artystone sp. with Curculionichthys luteofrenatus and Hisonotus chromodontus was monitored for one year with standardized monthly collections, and was found to be highly specific when there were no other parasitized fish species. Parasitic castration caused by Artystone sp. occurred in Curculionichthys luteofrenatus and Hisonotus chromodontus hosts, and there was a higher prevalence of infestation in females. The weight-length relationship was lower in parasitized Hisonotus chromodontus hosts, indicating a negative effect on somatic increment, although all hosts had fully replete stomachs and gastrointestinal tracts. The greatest standard-length values for both species were observed in the parasitized hosts. The presence of parasitized young specimens with undifferentiated sex and immature males and females suggests that the parasitic interaction in both species starts at a young age.

Checklist of parasites in fish from the upper Paraná River floodplain: An update.

This study provides an updated list of parasite species and their respective hosts in the upper Paraná River floodplain. The list of parasites is structured by phylum, class, order and family, followed by a record of each host species. A total of 315 taxa of parasites were reported, of which 201 were identified at the species level. These 201 species comprise 3 Flagellata, 3 Myxozoa, 50 Monogenea, 43 Digenea, 40 Cestoda, 41 Nematoda, 8 Acanthocephala, 6 Copepoda, 5 Branchiura and 2 Pentastomida, arranged in 84 host fish species. This work carried out in the floodplain of the upper Paraná River contributes to the listing of parasite species and host interactions of the local ichthyofauna. Little is known about these communities and its riches are underestimated due to the high density of fish found in this region, highlighting the importance of conducting studies on the local fauna.

Checklist of parasites in fish from the upper Paraná River floodplain: An update / Lista de parasitos em peixes da planície de inundação do alto rio Paraná: uma atualização

Abstract This study provides an updated list of parasite species and their respective hosts in the upper Paraná River floodplain. The list of parasites is structured by phylum, class, order and family, followed by a record of each host species. A total of 315 taxa of parasites were reported, of which 201 were identified at the species level. These 201 species comprise 3 Flagellata, 3 Myxozoa, 50 Monogenea, 43 Digenea, 40 Cestoda, 41 Nematoda, 8 Acanthocephala, 6 Copepoda, 5 Branchiura and 2 Pentastomida, arranged in 84 host fish species. This work carried out in the floodplain of the upper Paraná River contributes to the listing of parasite species and host interactions of the local ichthyofauna. Little is known about these communities and its riches are underestimated due to the high density of fish found in this region, highlighting the importance of conducting studies on the local fauna.

Resumo Este estudo fornece uma lista atualizada de espécies de parasitos e seus respectivos hospedeiros da planície de inundação do alto rio Paraná. A lista de parasitos está estruturada em filo, classe, ordem e família, seguida do registro de cada espécie de hospedeiro. São relatados 315 táxons de parasitos e, destes, 201 foram identificados por espécie. Essas 201 espécies compreendem: 3 Flagellata, 3 Myxozoa, 50 Monogenea, 43 Digenea, 40 Cestoda, 41 Nematoda, 8 Acanthocephala, 6 Copepoda, 5 Branchiura e 2 Pentastomida, distribuídos em 84 espécies de hospedeiros. Este trabalho, realizado na planície de inundação do alto rio Paraná, contribui para a listagem de espécies de parasitos e interações parasito-hospedeiro da ictiofauna local. Pouco dessas comunidades é conhecida, e suas riquezas são subestimadas devido à alta densidade de peixes encontrados nessa região, destacando-se a importância da realização de estudos sobre a fauna local.