The zebra-snout seahorse, Hippocampus barbouri, is an economically important marine fish and a potential candidate for aquaculture in Thailand. However, the reproductive ultrastructure of this seahorse is still poorly known. Transmission Electron Microscope (TEM) was used to characterize cellular morphology and ultrastructure of gametogenic stages in both sexes of H. barbouri. Based on morphology of the nucleus and unique characteristics of cytoplasmic organelles, oocytes in the oogenesis process of H. barbouri was classified into three distinct phases: primary growth phase (PG), secondary growth phase (SG) and atretic oocyte phase (AO). The early PG oocytes contained multiple nucleoli in close proximity to the nuclear membrane, showing the formation of cortical alveoli. The cytoplasm of late PG oocytes contained two distinctive cellular structures including lipid droplets and cortical alveoli and was enriched in rough endoplasmic reticulum, ribosome and mitochondria. The follicular complex complelety covered the oocyte at this phase and was classified into four distinct layers including zona pellucida, granulosa cells, basement membrane and theca cells. The yolk-granule formation was firstly observed in the early SG oocytes with well-developed microvilli in the zona pellucida and granulosa cells. During the late SG, the single-layered zona pellucida and the granulosa cells were well-organized. The dilated smooth endoplasmic reticulum and mitochondria were clearly visible in the granulosa cells. The AO oocytes exhibited disorganization of follicular complex. In male H. barbouri, spermatogonia and Sertoli-like cells occupied periphery of the germinal epithelium; however, the spermatocytes and spermatozoa were not observed in the germinal epithelium, possibly due to unique testis characteristics at this stage, season of the samples or aquaculture conditions. Taken together, this study unraveled characteristics of sexual differentiation in the zebra-snout seahorse and would provide benefit to monitor reproductive success of seahorse under aquaculture.

Objective: The study was carried out to investigate the use and impact of veterinary drugs, anti¬microbials, and supplements in commercial aquaculture for fish health management measures in three selected areas of Mymensingh, Bangladesh. Materials and Methods: Data collection was conducted through questionnaire interviews with owners of 50 fish farms and 25 drug shop owners from Trishal, Fulpur, Tarakanda, and Sadar Upazila of Mymensingh district. Results: A total of 15 trade-named veterinary antibiotics and six categories of other compounds were identified in this study. Antibiotics were found as the most used veterinary drugs (80.85%), followed by disinfectants, nutritional supplements, saline, ammonia removal agents, probiotics, and pesticides. These veterinary compounds performances for fish health management were found to vary (10%60%) significantly. Conclusion: This studys findings urge the necessity to produce and approve effective aqua drugs and treatments to ensure farmed fish and public health. [J Adv Vet Anim Res 2021; 8(1.000): 36-43]