Fine Structure of Statocyst Receptor of Astacus fluviatilis

Abstract

STUDIES with the light microscope^1–4 have produced a picture of the sensory element of the statocyst of decapod Crustacea, the innervation of which had not previously been understood. A typical hair of the crescent group of the cyst consists of a long shaft with a base that is shaped like a cask. One part of the wall of the cask is reinforced by sclerotized layers which form the “tooth”, the rest of the wall is membraneous^1,2 (Fig. 1). Opposite the tooth a light-refractive thread, the chorda^1,2, enters a cuticular spine of the shaft—the lingula. The chorda, composed of chitinous material², seems to originate close to the sense cells. Hensen¹ has described the chorda as the terminal fibre of the nerve, ending in the cask. Prentiss³ also thought the nerves ended in the cask. Kinzig², on the other hand, suspected that the chorda runs inside the nerve fibre as a stiffening element, and vom Rath⁴ recorded that the nerve terminated in the tip of the hair. He found several sense cells connected to one hair⁴; other investigators observed a one to one relationship^2,3.