ANALYSIS OF GONADAL DEVELOPMENT BY DIPLOID, TRIPLOID, AND TETRAPLOID EASTERN OYSTER Crassostrea virginica BROODSTOCK IN LOUISIANA  

Managing broodstock based on gonadal development is a fundamental component of hatchery and breeding operations.  Maintaining diploid, triploid, and tetraploid oyster broodstock confounds this management.  To better understand gonadal development of broodstock oysters of three ploidy states in the Gulf of Mexico region, broodstock were analyzed histologically every month (n = 15 per ploidy per month) over a one-year period (January 2015 - January 2016).  Sex, gonad-to-body ratio, and gonadal development stages were analyzed.  Gonadal development stages were determined by analyzing stained histological sections by light microscopy and assigned to one of four stages: early development, late development, spawning, and advanced spawning and regression.  Gonadal conditions were quantified based on gonad-to-body ratios (GBR) determined by computer-based image analysis of digital images of histological sections.  GBR was estimated using the total area of gonad and body for each histological section.  Southern populations of oysters are multiple spawners.  Understanding gonad development of triploid and tetraploid oyster broodstock as they relate to diploid oysters is a critical component in managing breeding efforts that utilize diploid, triploid, and tetraploid oysters.