To learn about superbugs and how they change. Most of the species in ontario are dioecious ( two houses ), meaning that they have separate males and females. Males release their sperm into the water through their exhalant siphon, which are then taken up by females downstream through their inhalant siphon. Fertilization is internal (i. e. , inside the female"s body), and the embryos develop inside modified pouches of the female"s gills called a marsupium. The embryos mature into specialized larvae called glochidia (singular glochidium), and it is these that represent the parasitic life stage. Specifically, the glochidia must attach to the gills of a fish in order to continue their development. Adult unionid mussels exhibit a wide variety of adaptations to attracting a host fish, as we will see in more detail later in the inquiry case. One of the most interesting is the modification of the mantle tissue to form a.