NUCHAL ORGANS OF THE POLYCHAETE PARAPIONOSYLLIS-MANCA (SYLLIDAE)

Citation
Ga. Lewbart et Nw. Riser, NUCHAL ORGANS OF THE POLYCHAETE PARAPIONOSYLLIS-MANCA (SYLLIDAE), Invertebrate biology., 115(4), 1996, pp. 286-298
Citations number
31
Categorie Soggetti
Zoology
Journal title
ISSN journal
10778306
Volume
115
Issue
4
Year of publication
1996
Pages
286 - 298
Database
ISI
SICI code
1077-8306(1996)115:4<286:NOOTPP>2.0.ZU;2-C
Abstract
Nuchal organs are known to be important sensory organs of many polycha ete annelid species. This study describes the fine structure of the nu chal organs and associated glands of Parapionosyllis manca. In each nu chal organ, the ciliated epithelium of the nuchal cleft encloses an ol factory chamber through which sensory cilia and microvillus-like proce sses radiate. These sensory components originate from bulbs of sensory cells that are closely associated to form a sensory bundle. Each bund le of cells is encased in a palisade of support cells bearing motile c ilia. Numerous secretory vesicles occur in the cytoplasm of the suppor t cells and beneath the modified cuticle of the nuchal organ. The supp ort cells of the olfactory region extend posteriorly to form the nucha l lobes, or glands. The cells are elongate and taper to a thin neck ju st before leaving the sensory area of the nuchal organ. There are esse ntially no nuclei in the sensory region as these and most of the other cellular organelles are concentrated in the lobes that extend into th e body cavity but are contained by the epidermal basement matrix. The nuchal organ is innervated by the nuchal nerve, which extends posterio rly from the hind portion of the brain.