The Secretory System of the Spines of Ophiocomina Nigra (Echinodermata, Ophiuroidea)

Abstract

The morphology of the spines of the ophiuroid Ophiocomina nigra is described, with particular reference to the nervous system and the sensory and secretory structures of the epidermis. The nervous system is composed of two main spinal nerves, located at the centre of the spine, and their associated branches. There are three secretory cell-types described: (1) fibrillar secretory cells which produce long, javelin-shaped secretory packages and, occurring exclusively in the basal two thirds of the spine, penetrate deeply with their basal regions lying close to the axial nerve running through the spine centre; (2) granular secretory cells, which also penetrate deep within the spine, contain secretory granules in the form of spherical dense vesicles (-1-3 |im in diameter); and (3) goblet secretory cells, filled with packages of loose amorphous material, are superficial in location and usually found associated with a type A ciliated sensory cell. The secretions of the fibrillar and granular secretory cells are thought to perform the functions of defence and feeding respectively. A number of different ciliated sensory cell-types have been identified. Apart from the situation with the goblet cells, no close association was found between secretory and sensory cells. It is suggested that the nervous, sensory and secretory cells act together to form a mucous secretion system with centralized, rather than local control. This system appears to operate when it is advantageous to produce secretion all over the body simultaneously once any portion is stimulated. Stimulation of sensory cells might result in axonal excitation of the spinal nerves and hence to the entire epineural nervous system. In this way, glands located anywhere in the body, which are controlled by the epineural system could be quickly activated to cause mucus release. This contrasts with the situation in the podia where closely associated sensory and secretory cells acting together form a secretory system with localized control.

Functional Morphology of the Arm Spine Joint and Adjacent Structures of the Brittlestar Ophiocomina nigra (Echinodermata: Ophiuroidea)

“…The histology and ultrastructure of this tightly anchored type of epidermis in O . nigra have been described in detail elsewhere [40–42]. …”

“…of the lateral arm plates and spine base, of O . nigra have been published [18,19,42], but unaccompanied by any consideration of their functional implications.…”

Exceptional population genomic homogeneity in the black brittle star Ophiocomina nigra (Ophiuroidea, Echinodermata) along the Atlantic-Mediterranean coast

“…In this work, we carry out a phylogeographic and population genomic study of the brittle star Ophiocomina nigra , for which different biological traits such as the feeding and social behaviour 46 , 47 , bioluminescence activity 48 , and secretory systems 49 , 50 have been explored. O. nigra presents a wide distribution including the Mediterranean Sea and the Northeastern Atlantic Ocean, from the Azores Islands to Norway 37 , 47 , from shallow waters to relatively deep habitats (400 m).…”

<p><strong>Study of the luminescence in the black brittle-star Ophiocomina nigra: toward a new pattern of light emission in ophiuroids*</strong></p>

“…This species lives often associated with O. fragilis (Mortensen 1927;Moyse & Tyler 1990;Picton 1993;Stöhr & O'Hara 2007). The mucus, produced at the arm level when the brittle star is attacked, is known for its anti-fooling properties (Ball & Jangoux 1990, 1996. It could also play a role in the locomotion and feeding behaviour of the species.…”