Ultrastructural organisation of the epiderrnal glands in the integument of the sea spiders Nymphon gracile Leach 1814, Achelia longipes Hodges 1864, and Pycnogonum littorale (Ström, 1762) (Chelicerata, Pycnogonida).

The present paper describes the ultrastructural organisation of the epidermal glands in three pycnogonid species : Nymphon gracile, Achelia longipes, and Pycnogonum littorale. These glands are distributed over the whole body surface and lodged in cuticular holes. They are composed of at least five cells : two secretory cells, one enveloping cell, and two (or more) accessory cells. The presence of nerve extensions in contact with the enveloping cell strongly suggests that the glands are under nervous control. They may play a defensive role.