Mate selection in captive-breeding rockfishes Sebastes spp.: inference from parentage analysis and the major histocompatibility complex (MHC)

Abstract

Rockfish species of the genus Sebastes are notable for being numerous and diverse. Rockfishes are unusual among fish because they fertilize their eggs internally and release live, swimming larvae. They undergo complex courting behaviors, which may allow females to be selective about their mates. The major histocompatibility complex (MHC) is implicated as having an important influence on mate selection in other fishes, especially in sticklebacks and salmonids. Research suggests that females choose mates that optimize the MHC genotypes of their offspring. Previous research on rockfishes indicates that multiple functional MHC sequences may be found in each species, and that multiple mating is common in the genus, possibly as a bet-hedging strategy against uncertain or incomplete mate-selection information. In this project, we characterized the MHC genotypes of copper (S. caurinus) and quillback (S. maliger) rockfish parents, assessed parentage of 14 larval broods, and assessed the MHC genotypes of the parents to determine if MHC-mediated mate choice was occurring. As in previous studies, we found that rockfishes possess multiple, highly variable MHC genes, and that females may mate with multiple males. We also found evidence of female preference for particular males. However, we found no strong evidence of selection based on MHC genotype. Females were not consistently selective based on relatedness, allele count, proportion of shared alleles, or minimum, mean, or maximum DNA or amino acid genetic distance. Instead, it appears that females were selective based on other measures of mate quality not considered in this study, with some hedging of bets through multiple mating also occurring.

Multiple‐brooding rockfishes (Sebastes spp.) can utilize stored sperm from individual sires to fertilize consecutive broods

“…In some mammals, the female reproductive tract can recognize and interpret spermatozoon's genetic signature (Holt & Fazeli, 2015); nonetheless, it is unknown if rockfishes have the capability for distinguishing among sperm and for biased use of stored sperm. In some rockfishes ( Sebastes alutus , S. atrovirens , Sebastes caurinus , Sebastes maliger and S. schlegelii ), the distribution of fertilization success among males was observed to be skewed, which could point to potential post‐copulatory selection, disproportionate quantity of sperm from different males or study sampling effects (Gao et al ., 2017; Johansson et al ., 2012; Sogard, Gilbert‐Horvath, et al ., 2008; Van Doornik et al ., 2008). It is unclear if there is an influence of paternal attributes on offspring quality to drive such processes, although female mate preference for large males has been observed in copper ( S. caurinus ) and quillback ( S. maliger ) rockfishes (Johansson et al ., 2012).…”

“…Multiple studies employing genetic paternity analysis have demonstrated that rockfishes can be polyandrous (documented in at least 15 species to date), with as many as four sires per brood observed in studies of wild fishes and as many as six sires per brood observed in studies of captive fishes (Gao et al ., 2017; Gray et al ., 2015; Hyde et al ., 2008; Johansson et al ., 2012; Karageorge & Wilson Jr., 2017; Sogard, Gilbert‐Horvath, et al ., 2008; Van Doornik et al ., 2008). This may be a diversified bet‐hedging strategy when mate selection criteria are uncertain (Yasui, 1998, Hyde et al ., 2008, Sogard, Gilbert‐Horvath, et al ., 2008, Johansson et al ., 2012).…”

“…Multiple studies employing genetic paternity analysis have demonstrated that rockfishes can be polyandrous (documented in at least 15 species to date), with as many as four sires per brood observed in studies of wild fishes and as many as six sires per brood observed in studies of captive fishes (Gao et al, 2017;Gray et al, 2015;Hyde et al, 2008;Johansson et al, 2012;Karageorge & Wilson Jr., 2017;Sogard, Gilbert-Horvath, et al, 2008;Van Doornik et al, 2008). This may be a diversified bethedging strategy when mate selection criteria are uncertain (Yasui, 1998, Hyde et al, 2008, Sogard, Gilbert-Horvath, et al, 2008, Johansson et al, 2012. Polyandry is more prevalent in larger and older females of some species (Van Doornik et al, 2008) and, in some rockfishes, older and larger females also contribute disproportionately to larval quality (Berkeley et al, 2004;Stafford et al, 2014) F I G U R E 1 (a) Macroscopic view of a chilipepper (Sebastes goodei) ovary with evidence of multiple brooding: a secondary brood of developing embryos, with a small number of residual eyed larvae from the first brood retained post-parturition and visible through the ovarian wall.…”

Testing mate choice and overdominance at MH in natural families of Atlantic salmon Salmo salar

“…Sampling soon after spawning, for instance collecting eggs in nests, may limit the problem of selective mortality that cumulates through a cohort's life. Although such sampling can readily be done in experiment of captive spawning (Johansson et al, 2012;Whitcomb et al, 2014), logistic and ethical problems may constrain its feasibility in natural populations (but see Grimardias et al, 2010).…”

Contrasting effect of hybridization on genetic differentiation in three rockfish species with similar life history

“…Finally, rockfish are documented to have complex courting rituals (Helvey, 1982) and apparent mate choice (Johansson et al, 2012).…”