Uterine fluid composition of the dwarf ornate wobbegong shark (Orectolobus ornatus) during gestation.
Ellis MT and Otway NM (2010) Uterine fluid composition of the dwarf ornate wobbegong shark (Orectolobus ornatus) during gestation. Presentation given at the Sharks International conference, 6 – 11 June 2010, Rydges Esplanade, Cairns, Queensland, Australia.
An understanding of the reproductive cycles of elasmobranchs can be greatly improved through the biochemical analysis of uterine fluids. The uterine fluid composition of the (dwarf ornate) wobbegong (Orectolobus ornatus) was quantified throughout pregnancy. The fluids surrounding eggs and early stage embryos (3 – 4 months gestation) had a complex composition with urea (98.48 mM), sodium (560.25 mM) and potassium (13.93 mM) concentrations significantly greater than those in seawater. Following this, the uterine fluids showed a gradual change in composition from complex to simple with electrolyte concentrations ultimately resembling seawater for the remaining 6 – 7 months of gestation, suggesting uterine flushing with seawater as documented in Squalus acanthias. The mean electrolyte concentrations in uterine fluid were significantly greater than those in the maternal plasma throughout gestation, indicating the fundamental role played by the uterus in accommodation, osmoregulation (especially during early development), respiration and the maintenance of an appropriate environment until parturition. The behaviour of this wobbegong during pupping may be related to the uterine seawater environment maintained during the latter part of pregnancy. Incorporating uterine fluid analyses, together with data on uterine wall structure and weight gain from egg to embryo will enable better determinations of the reproductive modes of elasmobranchs.