Glycoproteins in daphnids : potential signals for mating ?

Glycoproteins are used as mating signals by several aquatic organisms. We have developed techniques for selectively probing surface glycoproteins in zooplankters using fluorescently labeled lectins. We used these techniques to localize glycoproteins that could be used in cladoceran mating. Daphnia obtusa and Ceriodaphnia dubia females were screened for 12 lectins representing a wide variety of carbohydrate affinities. The structure exhibiting fluorescence in both species was the ovary. The signal contrast (signal/background ratio) across the ovary ranged from 2 to 21 which seems sufficient for males to discriminate a glycoprotein signal from noise. Results indicate that several glycoproteins which might be important in mating are present in the ovary of both species.