The Integumentary Mucous Secretions of the Ophiuroid Ophiocomina Nigra

Abstract

The general histology of the integument of the ophiuroid Ophiocomina nigra is outlined. Two types of integumentary mucous glands are described in detail for the first time. The first is a multicellular gland, the basal end of which is located deep within the calcareous layer of the integument. The source of the secretion is a variable number of nuclei embedded in a common cytoplasmic mass filled with fine basiphil granules. These cells contributed their secretion to a duct which pursues a tortuous course through the integument. The ducts frequently branch and anastomose so that any one exit pore may extrude mucin derived from a number of separate, polynuclear sources. The structure so formed is, thus, a massive, multicellular gland. Histochemical studies demonstrate that the mucin is a highly sulphated acid mucopolysaccharide. The second type of mucus-secreting unit is a unicellular gland usually located superficially in the calcareous layer or sometimes restricted to the epidermis and distributed universally over the body. The secretion product of these cells is shown histochemically to be a simple acid mucopolysaccharide. The mucin secreted by the tube-foot glands is demonstrated also to be a highly sulphated acid mucopolysaccharide.The function of these secretions has been investigated to some extent. The massive glands secrete only under conditions of alarm and it is suggested that this mucus serves as a defence against predation. The unicellular glands secrete in a periodic fashion correlated with the act of feeding. This secretion is probably utilized in a suspension-feeding mechanism.

Use of refuges by the ophiuroid Ophiopholis aculeata: contrasting effects of substratum complexity on predation risk from two predators

“…They avoid encounter with predators by responding to chemical exudates from the predators (Feder & Arvidsson 1967) or injured conspecifics (Rosenberg & Selander 2000) and by hiding in refuges (Hendler 1984, Witman 1985. Once there has been contact with a predator, ophiuroids can avoid being eaten by using active flight (Feder & Arvidsson 1967, Skold 1998, arm autotomy (Wilkie 1978), protective secretions (Fontaine 1964) and bioluminescence (which may function as aposematic coloration; Grober 1988a,b, Deheyn et al 2000. Cryptic ophiuroids may also retreat deeper into refuges to stay out of reach of the predator (Solan & Battle 2003) In the subtidal community of the Mingan Islands in the northern Gulf of St. Lawrence (eastern Canada), the brittle star Ophiopholis aculeata occurs in dense populations (up to 1700 ind.…”

Food and Feeding Habits ofLuidia CiliarisEchinodermata: Asteroidea

“…But he found that, unlike L. ciliaris, L. sarsi does not attack Ophiocomina even when starved. Ophiocomina secretes a mucous layer on the skin which has a repellent effect on predators (Fontaine, 1964). This does not appear to be effective against L. ciliaris (cf.…”

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

“…Although it has long been recognized that many ophiuroid spines had a hollow central axis bearing nervous tissue (Buchanan, 1963;Fontaine, 1964), the present work shows, for O. nigra, that this tissue consists of two distinct nerves. Presumably, the spine nerves originate from the segmental nerve that penetrates the lateral arm plate and enters the spine through an aperture located on the articular surface of the spine (Byrne, 1994).…”

“…Three types of secretory cells are generally recognized in the ophiuroid epidermis: (1) mucous cells containing an electron-lucent diffuse material packaged in irregular vesicles; (2) granulated cells containing an electron-dense compact material packaged in vesicles; and (3) fibrillar cells containing a moderately electron-dense material organized into parallel strands (Byrne, 1994). The secretory products of these cells are usually composed of mucopolysaccharides and have generally been attributed a feeding or defensive role (Buchanan, 1963;Fontaine, 1964;Pentreath, 1970). Recent work has concentrated on the sensory abilities of the spines ) and close association has been shown between sensory and secretory cells (Whitfield & Emson, 1983).…”