Ellis, M.T. and Otway, N.M., 2011. Uterine fluid composition of the dwarf ornate wobbegong shark (Orectolobus ornatus) during gestation. Marine & Freshwater Research, 62(6): 576–582.

Summary

An understanding of the reproductive cycles of sharks can be greatly improved through the biochemical analysis of uterine fluid. The uterine fluid composition of the dwarf ornate wobbegong (Orectolobus ornatus) was quantified throughout pregnancy. In the early stages of development, Orectolobus ornatus embryos had complex uterine fluids with concentrations of urea, sodium, and potassium greater than those in seawater and the uterine fluids surrounding mid to late stage embryos. The uterine fluid then showed a gradual change in composition from complex to simple and for the remainder of the 11–12 month gestation period, the uterine fluid resembled seawater. A uterine seawater environment suggests that seawater exchanges occur within the uterus and this has been documented in Squalus acanthias and observed in the current study. The uterine retention of embryos until birth, despite an ambient seawater environment, indicates the fundamental uterine roles of accommodation, protection, maintenance, osmoregulation and respiration. A combined methodology of uterine fluid biochemistry, uterine wall structure and embryonic weight gain will assist in better defining the reproductive mode of individual shark species.