EVALUATION OF QUALITY INDICES OF THE GONAD AND SOMATIC TISSUES INVOLVED IN REPRODUCTION OF THE PEARL OYSTER PINCTADA MAZATLANICA WITH HISTOCHEMISTRY AND DIGITAL IMAGE ANALYSIS.

We evaluated indicators of quality for female gonads (ovary and oocytes), male gonads (testis and seminal tubules), and selected somatic tissues (fiber packages in the adductor muscle and adenomeres in the digestive gland) that participate in reproduction of the pearl oyster Pinctada mazatlanica. The goal was to identify timing of optimal broodstock condition for larval rearing practices. Tissue samples were collected seasonally and processed with a combination of histochemistry and digital image analysis to develop a gonad tissue index, a lipid index, and a glycogen index. Seasonal changes in these indicators were correlated with changes in water temperature and chlorophyll a in the water. P. mazatlanica uses a combination of stored reserves and food supply (conservative vs. opportunistic strategy) to regulate reproduction, but the way energy is acquired and allocated varies between sexes. Female gonads contained higher lipid contents during spring. We suggest energy allocation from digestive gland, because this tissue showed lower lipid contents in the same season (conservative strategy). Within oocytes, the accumulation of lipids occurred from nutrients obtained from food supply during winter (19.6°C and ~650 ng/L) (opportunistic strategy). Male gonads contained higher glycogen contents in spring. A decreasing trend in the glycogen content of the adductor muscle was also detected in spring. This suggests that sperm build-up occurs partly at the expense of the glycogen stored in this tissue (conservative strategy). In seminal tubules, no correlation with the glycogen content of adductor muscle was detected, suggesting that these reserves were obtained from food supply in spring (22°C and ~400 ng/L) (opportunistic strategy). Optimal broodstock condition occurs mainly in spring and secondly in early winter. [ABSTRACT FROM AUTHOR]