Gametogenesis and Spawning Induction in Batissa violacea Lamarck, (1806) at Cagayan River, Philippines

Batissaviolacea Lamarck (l806) locally known as “cabibi” is considered endemic in Cagayan River at Lallo, Philippines and the most expensive freshwater bivalve in the region. This study described through monthly histological examination the cytological characteristics of gametogenesis and sexual dimorphism of the gonad of B. violacea collected from the wild, and determined spawning response using serotonin. Eight category sizes of the species were established, and 10 samples from each size were processed. Gonads were preserved, and subjected for histological processes to confirm gametogenesis. Using descriptive data analysis, confirmation of the identified mature stage at 31-35 mm was further tested through induction of serotonin. Results showed progressive stages of sperm formation in male follicles. Follicles could be seen in clusters and identified as to their sizes from spermatogonia, spermatocytes, spermatids and spermatozoa. Growing female follicles appeared attached to a cytoplasmic stalk in different sizes and shapes. Initially male germ cells appeared tiny and became concentrated at the lumen in radiating bands as they become mature. Likewise, mature oocytes with enlarged nucleus and tiny nucleolus fill the center of the lumen of the female gonad was observed. B. violacea successfully spawn using either 0.2 ml or 0.5 ml earlier (0.21 hour) compared to 36.70 hour when no injection was administered. This is a first time report in the country along the possibility of breeding the species in captivity.Keywords: Aquatic ecology, Batissa violacea, gametogenesis, Cagayan River, induced spawning,experimental design, Cagayan river