Alligator gar (Atractosteus spatula, Lacépède 1803) vitellogenin: Purification, characterization and establishment of an enzyme-linked immunosorbent assay

Alligator gar (Atractosteus spatula) is a non-teleost bony fish distributed in North America. Gar populations have drastically declined as a consequence of habitat deterioration and the lack of regulation for their capture. Control of reproduction is critical for recovering their natural populations. The impossibility to distinguish genders and the determination of sexual maturity have hindered their successful reproduction. This research was aimed at developing an enzyme-linked immunosorbent assay (ELISA) for the quantitative estimation of vitellogenin (VTG), a female-specific protein. Plasmatic VTG from 17β-estradiol (E2)-induced juveniles and ovary vitellin from adult females were purified and characterized. Polyclonal antibodies against both proteins were produced to develop an ELISA. The immunoassay was validated by quality tests such as sensitivity, parallelism, recovery, reproducibility and specificity. Vitellogenin was determined in different tissues (plasma, mucus, liver and gills) of alligator gar. Vitellogenin and E2 concentrations in female breeders were found to be higher in November, before the spring spawning season. This approach represents a quick, reliable and non-invasive practical alternative to distinguish genders and evaluate gonad maturation.