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

Abstract

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.

Population genetics of the freshwater fishProchilodus magdalenae(Characiformes: Prochilodontidae), using species-specific microsatellite loci

“…Another biological cause of observed heterozygosity deficit, assortative mating, does not seem to explain the results found in this study because P. magdalenae is iteroparous and characterized by total spawning (Jaramillo-Villa & Jiménez-Segura, 2008) as described in its congeners, P. costatus (Carolsfield et al, 2004) and P. lineatus (Roux et al, 2015). Even more, in this latter species, the genetic analysis based on microsatellite loci support polygamous mating in both sexes (Ribolli et al, 2020).…”

Social behaviors as welfare indicators in teleost fish

“…One of the few characiform species in which the reproductive behavior has been formally studied is the sabalo Prochilodus lineatus , a Neotropical migratory fish with shoaling behavior during reproduction. DNA and multilocus genotyping methods suggest that this species shows a monogamous genetic mating system in combination with polygamy ( 82 , 83 ). This knowledge on mating strategies and reproductive behavior of Neotropical migratory fishes in nature constitutes relevant evidence for the management and conservation of such an important fishery resource.…”

First record of the mating behaviour of the spotted surubim Pseudoplatystoma corruscans in the Uruguay River

“…Males predominated in the school, in the proportion of five males to one female. Brito and Bazzoli (2003) observed a similar ratio in the São Francisco River, with three males to one female, and genetic studies have revealed that polygamy is common among some migratory fish, with a greater number of males per female (Ribolli et al ., 2016; Ribolli et al ., 2020).…”

“…The spotted surubim is highly fecund, and a single female is capable of releasing hundreds of thousands eggs, i.e ., 1 g of eggs contains more than 2500 eggs (Sato, 1999). Under these conditions, with several males simultaneously releasing gametes in the water current, the number of fertilized eggs and genetic variability tend to increase, although genetic studies have shown that reproductive success is variable within breeding schools (Ribolli et al ., 2016; Ribolli et al ., 2020), as fertilized eggs may belong to a few breeders. The authors recorded males competing strongly for females, and it is possible that not all males were capable of spawning.…”