ULTRASTRUCTURAL ORGANIZATION EPIDERMAL GLANDS IN THE INTEGUMENT OF THE SEA SPIDERS NYMPHON-GRACILE LEACH 1814, ACHELIA-LONGIPES HODGES 1864, AND PYCNOGONUM-LITTORALE (STROM, 1762) (CHELICERATA, PYCNOGONIDA)

The present paper describes the ultrastructural organisation of the ep idermal 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 compose d of at least five cells : two secretory cells, one enveloping cell, a nd 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.