Genetic evidence supports polygamous mating system in a wild population of Prochilodus lineatus (Characiformes: Prochilodontidae), a Neotropical shoal spawner fish

Behavioral observations made on fish have revealed remarkably diverse reproductive strategies, including polygamy by both sexes. Still, to date, most Neotropical species remain unstudied as to whether the observed reproductive behavior in natural populations correlates with their genetic mating systems. Here, we investigated the genetic mating system of a wild population of Prochilodus lineatus settled in the Middle Uruguay River basin. By using sibship reconstruction and parental inference methods based on microsatellites? genotypes, we inferred 45 females and 47 males as potential parents of the 87 larvae analyzed. We found evidence supporting polygamous mating in both sexes: while a high percentage of males (44.7%) fertilized the eggs of one female, 55.3% of the inferred males fertilized eggs of up to four females. Likewise, while 44.5% of the inferred females had their eggs fertilized by one only male, 55.5% of females were fertilized by multiple males. The estimated proxy of the effective population size (Nb) was 126, exhibiting moderate to high levels of genetic diversity. The genetic evidence contributed in this study complements earlier behavioral observations of formation of spawning nuclei of aggregating breeders, which may be promoting a polygamous mating strategy in this long-distance migratory fish.Observações do comportamento de peixes neotropicais têm revelado estratégias reprodutivas marcadamente variáveis, incluindo poligamia nos dois sexos. Ainda assim, até então, a correlação entre comportamento reprodutivo observado em populações naturais e sistemas de acasalamento genético permanece pouco explorada para maioria de espécies Neotropicais. Neste estudo investigamos o sistema genético de acasalamento de Prochilodus lineatus em uma população natural estabelecida no Médio rio Uruguai. Utilizando métodos de reconstrução de grupos familiares e inferências parentais baseados em genótipos de microssatélites, inferimos 45 fêmeas e 47 machos como os possíveis parentais das 87 larvas amostradas. Encontramos evidência que permite apoiar a ocorrência de acasalamento poligâmico em ambos os sexos: enquanto uma percentagem alta de machos (44,7%) fertilizou somente uma fêmea, 55,3% dos machos inferidos fertilizaram mais de uma fêmea (até quatro por macho). Da mesma forma, enquanto que 44,5% das fêmeas inferidas tiveram seus ovos fertilizados por apenas um único macho, 55,5% das fêmeas tiveram ovos fertilizados por múltiplos machos. A estimativa do tamanho populacional efetivo (Nb) foi 126, exibindo níveis entre moderados e altos de diversidade genética. A evidência genética que apresentamos nesse estudo complementa observações iniciais da formação de núcleos de desova que podem promover estratégias de acasalamento poligâmico nessa espécie migratória de longa distância.Fil: Ribolli, Josiane. Universidade Federal Da Santa Catarina. Centro de Ciencias Biológicas; BrasilFil: Miño, Carolina Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Scaranto, Bianca Maria Soares. Universidade Federal Da Santa Catarina. Centro de Ciencias Biológicas; BrasilFil: Reynalte Tataje, David Augusto. Universidade Federal Da Fronteira Sul; BrasilFil: Zaniboni Filho, Evoy. Universidade Federal Da Santa Catarina. Centro de Ciencias Biológicas; Brasi

The influence of the trawl net mouth size and collection cod-end type on catch of ichthyoplankton / A influência do tamanho da rede e do tipo de copo coletor na captura do ictioplâncton

Currently, there are several types and models of plankton nets available on the market. However, it is not known for sure how the differences in size and shape of these nets influence the capture of eggs and larvae. Therefore, the objective of this study was to investigate the influence of mouth size and collection cod-end type on the capture of ichthyoplankton organisms. Collections were carried out in October and November 2019 on the Ibicuí River (Rio Grande do Sul, Brazil) using four different plankton trawl nets: T1: Wide mouth pelagic net with closed collection cod-end; T2: Wide mouth pelagic net with opened collection cod-end; T3: Narrow mouth pelagic net with closed collection cod-end and T4: Narrow mouth pelagic net with opened collection cod-end. At the laboratory, the samples were screened and the larvae were classified in the Yolk-Sac, Pre-Flexion, Flexion and Post-Flexion stages. To evaluate the variation of eggs, total larvae and developmental stages in each of the trawl nets, a two-way Analysis of Variance (ANOVA) was used. When the ANOVA results were significant, Tukey's a posteriori test was performed to detect differences. There was no statistically significant difference (P>0.05) in the capture of eggs and total larvae in the different nets in October. However, November has registered the highest number of total larvae in the widest mouth nets. In both months of sampling, there was greater capture of the Flexion and Post-Flexion stages on the wide mouth and opened collection cod-ends nets. The efficiency of ichthyoplankton capture seems to be related to larval developmental stages, which demonstrates the importance of choosing a net that adapts to the objectives of each study

Diets and trophic structure of fish assemblages in a large and unexplored subtropical river: The Uruguay river

This article belongs to the Special Issue Trophic Interactions in Warm Freshwater EcosystemsThe Neotropics represent a hotspot for freshwater biodiversity with vast number of fish species of scarce ecological knowledge. This holds true for the Uruguay River, where fish assemblages and their diets remain unexplored. Fish assemblages were surveyed in 14 sites along the river main course, from headwaters to mouth (approximately 1800 km), with the aim to identify the trophic roles of fishes and to describe trophic structure of these assemblages, following standardized sampling campaigns and laboratory procedures. One hundred species (2309 gut contents) were analysed and classified into four trophic groups subdivided into eight lower-level groups: Piscivore, piscivore-invertivore, detritivore, omnivore-detritivore, omnivore-invertivore, omnivore-planktivore and omnivore-herbivore. The trophic structure of the assemblages varied along the river, with the relative species richness of fish consuming terrestrial invertebrates increasing towards the middle river section, probably driven by the large floodplains in that areas, supporting global theories such as the flood pulse concept. This study describes the feeding habits of fish along the Uruguay River, being the first dietary description for 29 species. This knowledge is essential for management and conservation, serving as baseline in the context of future environmental changes while generating novel evidence on the functioning of ecosystems in this scarcely studied climatic region