Individual contributions to pooled-milt fertilizations of silver catfish Rhamdia quelen

Abstract

Supplementary stocking of fish in natural environments is a way to mitigate or compensate for the changes imposed on wild populations by river damming. Since little is known about the genetic composition of the supplementary stocks obtained by pooled-milt fertilization, the aim of this study was to determine the individual contributions of male jundiá Rhamdia quelen to offspring. Sperm from four males were mixed using equal volume of sperm from each of the males to fertilize eggs from only one female, kept in three blend with six males and three females. The proportions of larvae sired by the different males were quantified using five polymorphic DNA microsatellite loci. Analysis of these loci allowed paternal determination of 84% of the progeny, at a 0.972 combined exclusion probability. Broodstock milt had good fertilizing capacity when used alone, but when pooled the fertilizing capacities, its fertilizing possibility varied from 4 to 65%. Results show that milt pools favor gametes of some males over others, thus reducing the progeny's genetic variability.A estocagem de suplementação de peixes em ambientes naturais é uma das maneiras de mitigar ou compensar as alterações impostas pelo represamento dos rios às populações selvagens. Pouco se conhece sobre a composição genética dos estoques repovoadores obtidos através do manejo reprodutivo com fertilizações com o uso de pool de sêmen, de maneira que este trabalho teve como objetivo verificar a contribuição individual de machos de jundiá (Rhamdia quelen) na progênie. O mesmo volume de sêmen de quatro machos foi misturado para fertilizar os ovócitos de uma única fêmea, sendo mantidos em três combinações com seis machos e três fêmeas. A proporção de larvas geradas de diferentes machos foi quantificada através de cinco marcadores microssatélites. A análise dos cinco locus permitiu a determinação da paternidade de 84% da progênie, com 0,972 de probabilidade de exclusão combinada. O sêmen dos reprodutores apresentou boa capacidade de fertilização quando utilizados separadamente, porém, quando utilizados em pool apresentaram capacidade de fertilização entre 4 a 65%. Os resultados revelam que o pool de sêmen favorece alguns machos sobre outros, reduzindo a variabilidade genética da progênie.

Population Genomics in Rhamdia quelen (Heptapteridae, Siluriformes) Reveals Deep Divergence and Adaptation in the Neotropical Region

“…Previous studies in R. quelen using cytb and COI mitochondrial markers arrived at important evolutionary conclusions in the Neotropical region, but a comparative analysis between mtDNA lineages reported separately for both markers was lacking in the literature [5,6,9,10]. The studied area is inhabited by fish with three cytb mtDNA lineages that coexist in some basins and that would have diverged in allopatry 5.94-4.55 million years ago (MYA) [9]. According to Ríos et al [14], Rq2 and Rq4+Rq6 would belong to different clades, A and C, respectively.…”

“…Some of these lineages have dispersed widely during the post-glacial reclamation of habitat [6,7]. Among Neotropical silver catfish, Rhamdia quelen (Quoy and Gaimard, 1824) (Heptapteridae, Siluriformes) is distributed from the northeast end of the Andes mountain range to the central part of Argentina [8] and constitutes a valuable species exploited in artisanal fisheries and regional aquaculture [9][10][11]. Moreover, R. quelen has been proposed as a priority species for conservation in its southernmost distribution because of its cultural and economic value [12].…”

Contribuição parental em progênies de Curimba usando diferentes sistemas reprodutivos

“…Research has shown that using different sex ratios (semen pool or individual spawning) for reproduction of some fish species can influence the parental contribution to progeny, thus exercising reproductive dominance of some males (RIBOLLI and ZANIBONI-FILHO, 2009). This fact is undesirable in conservation programs, since the homogeneity of genetic inheritance can minimize inbreeding that may compromise the progeny viability (LOPERA-BARRERO et al, 2014;GOES et al 2017).…”

Induction of triploidy in Rhamdia quelen (Siluriformes, Heptapteridae) by double temperature shock

“…The sperm was stripped on the egg mass and homogenized. Gametes were then activated using hatchery water (Ribolli & Zaniboni-Filho, 2009). In order to estimate the amount of eggs for subsequent incubation procedures, an aliquot (0.5 g) from each batch was fixed in 4% formalin.…”