The structure and function of thoracic exopodites in the larvae of the lobster Homarus gammarus (L.).

The first three larval stages of the lobster Homarus gammarus are pelagic swimming animals. A description is given of the exopodite apparatus of the thoracic appendages that provide lift and propulsive power in these stages. Setal arrangement and display provides greater surface area during power strokes. Musculature is peculiar to the exopodites and concerned with rotational movements of the appendage. Metachronal beating takes place with the segmental appendages moving in a variable sequence.