PARTRIDGE, C.*; SHARDO, J.; BOETTCHER, A.; University of South Alabama, Mobile; Middle Tennessee State University, Murfreesboro; University of South Alabama, Mobile: Morphology and Reproductive Physiology of Syngnathus scovelli Brood Pouch

Syngnathids exhibit reversal of sex roles during mating and brooding. Females insert eggs into brood pouches of males, where they are incubated until the end of the larval period. The function of the brood pouch has been debated for over 100 years and two main theories have been proposed: (1) the brood pouch serves as a transfer site for nutrients and oxygen, and (2) the brood pouch serves an osmoregulatory function. To clarify the role that males play during the brooding period, this study examines changes in the inorganic and organic makeup of brood pouch fluid and blood of males at specific time points in the brooding cycle, and examines changes in the surface morphology of the brood pouch. In addition, baseline biomarkers including gonadosomatic (GSI) and hepatosomatic indices (HSI), and hematocrit were evaluated. The model system used was the Gulf pipefish, Syngnathus scovelli, found throughout the Gulf of Mexico in salinities from 0 – 30 ppt. Electron microscopy showed that once eggs were received, the brood pouch epithelium formed shallow depressions enclosing individual embryos. This enclosure may allow for increased surface area contact between male tissue and embryos. Male GSI values decreased significantly through the brood cycle. Hematocrit showed an increase followed by a significant decrease; however, no significant changes were observed for HSI, protein or glucose concentrations. Total osmolality data showed males incubated embryos at an osmotic concentration similar to that of their blood, regardless of their environment. We infer that the yolk serves as the main nutrient source for embryos, however, the brood pouch may serve as an important osmoregulatory device.