Liver Condition And Maternal Offloading In The Bonnethead Shark (Sphyrna Tiburo)
Florida Southern College
Many marine organisms, including sharks, may be susceptible to accumulating high concentrations of toxins from exposure to their environment and as top predators through biomagnification. The bonnethead shark (Sphyrna tiburo) is a coastal elasmobranch belonging to the hammerhead family. Bonnethead reproduction involves a close connection between mother and embryo through a placental analogue. Maternal offloading refers to the transfer of various toxins from the system of a mother to her offspring and may be an important source of contaminant loading in species with an umbilical connection throughout development. The presence of maternal offloading in this species was tested by examining non-pregnant female bonnethead sharks, pregnant female bonnethead sharks, and the respective unborn offspring of the pregnant individuals captured from middle Tampa Bay, FL. The Hepatosomatic index and the Condition Factors were calculated for 15 non-pregnant, 4 pregnant, and 26 embryos as a means of analyzing the health of the organisms. Measurements in the offspring were then compared to measurements of the respective mothers and non-pregnant individuals. These results may have implications for shark populations residing in areas with high levels of pollution, specifically for sharks with placental viviparity, whereby mothers may pass significant levels of contaminants to their unborn offspring in much higher relative concentrations than found in each of the mothers.
Honors Thesis Spring 2017
Pollution, Bonnethead Sharks, Sphyrna Tiburo, Liver conditions, Pregnancy