Oocyte-expressed fertilization factor that mediates sperm-egg binding and is essential for sperm entry into the egg (PubMed:30190407). Necessary and sufficient to mediate species-specific gamete recognition and fertilization, which is essential for vertebrate species performing external fertilization (PubMed:30190407). External fertilization cannot guarantee that only conspecific sperm reaches the egg by precopulatory mate choice: proteins such as Bouncer can therefore support the selection of conspecific sperm (PubMed:30190407). Highly expressed in oocytes (PubMed:30190407). Not expressed in testis (PubMed:30190407). N-glycosylated. Females are almost sterile: only 7 of 3024 eggs derived from mutant females develop into cleavage-stage embryos, as opposed to the majority of eggs from wild-type (PubMed:30190407). Both male and female fishes develop normally and are overtly healthy (PubMed:30190407). Males are fertile (PubMed:30190407). Was named bouncer (bncr) in reference to the colloquial name of a security guard at a bar. Belongs to the SPACA4/bouncer family. Silent walls - Issue 210 of January 2019