Evaluating Reproductive Differences and Hybridization Between Zebra and Quagga Mussels

Abstract

Zebra mussels are a notorious invasive species that have caused significant ecological and economic impact. However, there is another species, the quagga mussels, that is as equally detrimental and even displaces zebra mussels in many locations. Because the two species have overlapping habitats, similar appearances and reproductive behaviors, hybridization between the two is a possibility. It is important to know whether hybridization will occur between the two species since they could possibly produce hybrids that might be stronger and more resistant offspring, causing even further detrimental effects to our water systems. In this experiment, we evaluate the reproductive differences between zebra mussels (Dreissena polymorpha) and quagga mussels(Dreissena bugensis) and observe if hybridization between the two species is possible. The basic morphologies of the different gametes are similar in many aspects, while having few differences. After spawning both species, we performed fertilization experiments using intraspecific (same species) and hybrid crosses looking at fertilization and early development. Despite differences in gamete morphology, chemotaxis was observed in both trials; both eggs successfully attracted the sperm of the other species. When observing the fixed samples, sperm binding was confirmed at five minutes after fertilization. Other areas we looked at are sperm entry and egg activation.