Description of glochidia of five species of freshwater mussels (Hyriidae: Unionoidea) from South America.

The glochidia of South American Hyriidae were first described and illustrated by Lea (1868); 52 years later Ortmann (1921), followed by Bonetto (1954, 1955, 1960a, b, 1961a-c, 1962a, b) and others, described the larva of various species. However, many larvae are still unknown. The valves of five glochidia of two different types are here illustrated and described: two fish-parasitizing glochidia with the presence of a S-shaped tooth in each valve, and three glochidia that do not parasitize fish, with valves devoid of teeth or spinulae. The valves are measured and compared in: (a) length, (b) height, (c) dorsal hinge length, (d) displacement of the ventral point in relation to the middle of the hinge, and (e) angle of the ventral point in relation to the center of the hinge. Statistics of these measurements are also provided. The internal anatomy of the glochidium of Diplodon martensi (Ihering, 1891) and D. koseritzi (Clessin, 1888) are briefly described. Some of the larvae illustrated were photographed with a scanning electron microscope and some were drawn using a biological microscope with camera lucida.