Biology subjects

Wagle, R.

Publications and source records attributed to Wagle, R..

3 recordsLinked to original sources

bioRxiv2024

Reproductive fluids enabling cryptic female choice of paternity do not induce concomitant gamete-mediated paternal effects in embryos of hybridizing salmonid fishes

Post-mating sexual selection in the form of cryptic female choice provides opportunities for females to bias paternity to favor preferred males. However, little is known regarding how cryptic female choice might affect offspring outside of paternity, via female modified changes to sperm environmental experience. Gamete-mediated paternal effects are widespread, and female alteration of sperm experience may play an unrecognized role in shaping cryptic female choice. Using hybridizing salmonid fishes that have documented female mediated conspecific sperm preference via differential upregulation of sperm swimming performance, we created artificial split-brood and split-ejaculate fertilizations to determine if sperm experience in different conditions influences offspring development. Prior to contact with eggs, sperm experienced 20s of swimming in either water, or water with the addition of conspecific ovarian fluid or heterospecific ovarian fluid. Over 186 days, we quantified hatch timing, hatchling size, and developmental stage and found that differential sperm experience created biologically irrelevant (average effect size of 1.06%) changes on offspring development, which were much smaller than the effects of hybridization itself (average effect size of 10.45% for the species of the father). Since ovarian fluid drastically changes sperm experience when compared to water, we conclude that females can use ovarian fluid to bias paternity without concomitant consequences to offspring development.

evolutionary biology↗

bioRxiv2024

Endurance rivalry in capelin: insights from semen quality and regeneration

Male-biased adult sexual size dimorphism is often the result of intra-sexual selection driven by male-male competition. Capelin (Mallotus villosus) exhibit male-biased sexual size dimorphism but lack contest competition or clear scramble competition, and female mate choice, if present, is unrelated to male size. Consequently, it is hypothesized that adult sexual size dimorphism in capelin is due to a mating system that favours larger males with greater energy reserves, allowing them to compete for prolonged access to mating opportunities through endurance rivalry. To enable this, males need a continual supply of semen throughout the spawning season. However, they have unusually small testes and are predicted to deplete stored semen rapidly. Furthermore, their unique sperm physiology (i.e. the only known externally fertilizing vertebrate to release pre-activated semen) may constrain their ability to regenerate it. We found that the majority of capelin sampled on beaches had adequate semen, but towards the end of the spawning season, some fish had none. Capelin held in laboratory tanks could regenerate semen within two days, maintaining their ability to seize continual mating opportunities. These results support the endurance rivalry hypothesis.

evolutionary biology↗

bioRxiv2024

Does post-ejaculatory sperm experience prior to fertilization alter offspring performance beyond paternity in an external fertilizing fish?

Recent research has suggested that the environment encountered by sperm post-ejaculation may impact offspring development beyond the transfer of the paternal genome. The mechanisms that underlie such effects remain unclear, but two non-mutually exclusive processes have been proposed. 1) Haploid selection, whereby stressful conditions act as stronger post-ejaculation pre-fertilization selective pressures on semen than under benign situations, resulting in the fertilization of, on average higher quality sperm and the production of offspring that exhibit superior performance across all environmental conditions that they might encounter. 2) Epigenetic inheritance, where environmental conditions induce changes in sperm that are passed down to offspring, resulting in altered gene expression in offspring. This would be adaptive if sperm experiences anticipate what is to come and improve offspring performance to match those conditions. Capelin (Mallotus villosus) sperm and embryos are sensitive to salinity and may represent a good system to investigate these phenomena. We used a split-ejaculate and split-brood experimental block design to expose capelin sperm to known benign (25 psu) and stressful (35 psu) salinity prior to egg contact, and split each batch of fertilized eggs for incubation at matched and mismatched salinity to those of sperm exposure. Our findings revealed no differences in hatch characteristics between offspring produced by sperm exposed to benign and stressful salinity conditions. A follow-up experiment found the same result with an increased selection gradient at 5 psu and 35 psu. Our study does not support the hypothesis that sperm experiences exert an influence on the development of offspring characteristics, independent of paternity. Instead, our results suggest that the sole influential factor in sperm determining offspring characteristics is the transfer of the paternal genome.

evolutionary biology↗