CHEMICAL-COMPOSITION OF UTERINE FLUID IN 4 SPECIES OF VIVIPAROUS SHARKS (SQUALUS-ACANTHIAS, CARCHARHINUS-PLUMBEUS, MUSTELUS-CANIS AND RHIZOPRIONODON-TERRAENOVAE)

1. Uterine fluid and blood plasma samples from pregnant specimens of t he viviparous sharks Squalus acanthias, Carcharhinus plumbeus, Mustelu s canis and Rhizoprionodon terraenovae were analysed for total protein , total lipid, total glucose and osmolarity. 2. Intracapsular uterine fluids of the matrotroph. Rhizoprionodon terraenovae, whose embryos be ar appendiculae, exhibit higher concentrations of protein, lipid and g lucose than those of placental matrotrophs lacking appendiculae. 3. In near-term specimens R. terraenovae, intracapsular protein and lipid l evels in excess of those within the maternal blood plasma suggest acti ve concentration of these molecules within intracapsular fluids. 4. Th ere exists a significant osmotic differential between maternal blood p lasma and intracapsular uterine fluid in both R. terraenovae and M. ca nis. 5. These results are discussed in relation to the evolution of ma ternal embryonic transfer mechanisms in viviparous sharks.