Fertilization in ungulates

Parasite intensity drives fetal development and sex allocation in a wild ungulate

An understanding of the mechanisms influencing prenatal characteristics is fundamental to comprehend the role of ecological and evolutionary processes behind survival and reproductive success in animals. Although the negative influence of parasites on host fitness is undisputable, we know very little about how parasitic infection in reproductive females might influence prenatal factors such as fetal development and sex allocation. Using an archival collection of Dall’s sheep (Ovis dalli dalli), a capital breeder that depends on its body reserves to overcome the arctic winter, we investigated the direct and indirect impacts of the parasite community on fetal development and sex allocation. Using partial least squares modelling, we observed a negative effect of parasite community on fetal development, driven primarily by the nematode Marshallagia marshalli. Principal component analysis demonstrated that mothers with low parasite burden and in good body condition were more likely to have female versus male fetuses. This association was primarily driven by the indirect effect of M. marshalli on ewe body condition. Refining our knowledge of the direct and indirect impact that parasite communities can have on reproduction in mammals is critical for understanding the effects of infectious diseases on wildlife populations. This can be particularly relevant for species living in ecosystems sensitive to the effects of global climate change.

Identification of homologous binding proteins in porcine and bovine gametes

The purpose of this study was to determine if sperm and oocyte proteins that mediate plasma membrane interaction during mammalian fertilization are conserved among porcine and bovine gametes. We examined homologous and heterologous sperm and zona-free oocyte interactions to determine the extent of cross-reactivity between the gametes of these two ungulate species. First, the numbers of ejaculated porcine and bovine sperm bound to the oocyte plasma membrane of intact porcine and bovine oocytes were determined in vitro. There was no significant difference between the number of porcine or bovine sperm that bound to porcine or bovine oocytes (P > 0.25). Second, individual porcine and bovine sperm plasma membrane proteins were identified by binding of homologous or heterologous oocyte plasma membrane to whole sperm plasma membrane on Western ligand blots. The relative amount of labeled oocyte plasma membrane bound to individual sperm plasma membrane proteins was analyzed by laser densitometry. Eight porcine sperm plasma membrane proteins and seven bovine sperm plasma membrane proteins were bound by both porcine and bovine oocyte plasma membrane. A significantly greater relative amount of porcine oocyte plasma membrane than bovine oocyte plasma membrane was bound to the 14- and 10-kD porcine sperm plasma membrane proteins (P < 0.001 and P < 0.01, respectively). A 27-kD bovine sperm plasma membrane protein bound proportionally more bovine oocyte plasma membrane probe than porcine oocyte plasma membrane probe (P < 0.04). These results are consistent with conservation of similar receptor ligand interactions at the gamete plasma membrane among porcine and bovine gametes.