Despite a century of intensive research, fertilization is one of the least understood fundamental biological processes. Current theory predicts that membrane-bound proteins promote gamete recognition, but soluble-egg compounds attracting conspecific sperm could also act as pre-zygotic factors maintaining species integrity while increasing fertilization rates. Whereas cell contact recognition between male and female gametes is critical for sexual reproduction, the role of soluble egg factors remains undetermined. Using abalone (genus Haliotis), this project combines a formative conceptual framework with unprecedented techniques and infrastructure to establish the chemical 'language' of sperm and egg. It is expected to provide the first concrete evidence that barriers to hybridization can function prior to gamete contact, and that remote chemical signals can promote speciation. This study has implications for reproductive biology in humans as well as wildlife conservation. Future research could advance innovative approaches for solving problems in human contraception and infertility, using abalone as a valuable animal model: working with German colleagues, the investigators have identified and cloned genes coding for chemoreceptors on human sperm membranes. Recent discoveries link receptor function with sperm attraction to egg. Compelling challenges in conservation biology also will benefit from new knowledge of sensory stimuli controlling fertilization. For many threatened or endangered species, from abalone and corals to apes and elephants, fertilization is the bottleneck to species proliferation. Basic research on sperm chemoattraction is likely to yield original solutions to age old problems in reproductive biology. In captive breeding programs, for example, soluble sperm attractants could be used to identify the most promising sperm donors. Assuming gamete compatibility between mates, a donor with fast and chemo-responsive sperm may enhance the probability of fertilization while potentially improving offspring quality. The investigators have a strong tradition of active community outreach and undergraduate and graduate education. In particular, this project will invigorate training of women and underrepresented students in interdisciplinary research, towards careers in physiology, genetics, and environmental sciences.
