Ophiocomina Nigra Research Articles

The metabolism of biphenyl. V. Phenolic metabolites in some marine organisms.

The phenolic metabolites of biphenyl in the crustacean Cirolana borealis LILJEBORG (ISOPODA), the gastropod Buccinum undatum L and the ophiuroid Ophiocomina nigra ABILDGAARD have been analysed qualitatively and semi-quantitatively as trimethylsilyl (TMS) ethers by combined gas chromatography/mass spectrometry and gas chromatography, respectively. The findings demonstrate the in vivo metabolic capacity of these organisms to convert biphenyl into its hydroxylated derivatives. Thus, 2-hydroxybiphenyl is the most prominent metabolite detected in all these experiments, which also showed that minor amounts of the 4-hydroxy and 4,4'-dihydroxy metabolites are formed. Metabolites of biphenyl origin are found both in the sea water from the aquaria and in the tissue of the respective marine organisms. The experiments, moreover, indicate a slow metabolism of biphenyl in C. borealis, B. undatum and O. nigra, between which no qualitative metabolic differences are found.

Suspension-feeding in the brittle-star Ophiothrix fragilis

Basket-stars are suspension-feeders and suspension-feeding by other brittle-stars was suspected long ago on circumstantial grounds, but it is only in the last twenty years that it has been actually demonstrated, and detailed descriptions of suspension-feeding behaviour are still available for only a handful of species. Blegvad (1914) pointed out that Ophiothrix fragilis (Abildgaard) and other species lead sedentary lives and feed largely on detritus on, or near, the sea-floor. Wintzell (1918) explicitly suggested tha and Ophiopholis aculeata (L.) are suspension-feeders, primarily on the grounds that they are commonly found in current-swept localities where plankton is rich, in association with known suspension-feeders such as Modiolus, Lima and Alcyonium. The same suggestion was made by Vevers (1952) who noted the occurrence of dense aggregations of O. fragilis in offshore, current-washed areas near Plymouth, and who later observed suspension-feeding behaviour in that species and in Ophiocomina nigra (Abildgaard) (Vevers, 1956). This was only the second time that suspension-feeding had been documented for any (ophiurid) brittle-star, but now it has been described in about a dozen species and suspected in others, mostly members of the Amphiuridae, Ophiactidae, Ophiothricidae and Ophiocomidae (MacGinitie, 1949; Kuznetsov & Sokolova, 1961; Moore, 1962; Magnus, 1964; Buchanan, 1964; Fontaine, 1965; Fricke, 1970; Pentreath, 1970).

Direct observations on the sublittoral marine algae of Argyll, Scotland

The distribution with depth of sublittoral marine algae has been investigated at 11 sites on the west coast of Scotland. More than half of the species found were confined to the sublittoral zone. The greatest variety of species was found in shallow water at sites sheltered from excessive turbulence. With increasing depth the number of species found steadily decreased. There was no evidence of a specifically distinct algal flora confined to deeper water. No algae were found deeper than 36 m below ELWS at any site, but the lower limit of algal growth was reduced to 9 m in a turbid water loch and to 3 m at a site where the herbivorous echinoderm Ophiocomina nigra was abundant. Fairly distinct algal communities were found on different substrates. The major communities recognised underwater were algae attached to stable substrata, algae attached to unstable substrata and epiphytic on other algae, especially on the stipes of Laminaria hyperborea. On stable rock in areas subject to water movement L. hyperborea forest was the dominant vegetation whereas on unstable substrata and in sheltered localities L. saccharina was dominant.

TheLithothamnioncommunity in Nord-Möre, Norway with notes on the epifauna ofDesmarestia viridis(Müller)

Abstract The animal community on densely branched clumps of Lithothamnion at a depth of 5 to 10 m was studied in the neighbourhood of Kristiansund in Nord-More (Norway). The community resembles the Modiolus modiolus community and belongs to the boreal offshore gravel association. Only seven of the 55 species or so recorded yielded more than 100 specimens each. Nereis pelagica, Hiatella arctica, Acmaea virginea, and Ophiopholis aculeata were found on nearly every clump of Lithothamnion. The epifauna on Desmarestia viridis was dominated by Ophiocomina nigra.

The feeding mechanisms of the ophiuroid Ophiocomina nigra

The feeding mechanisms of Ophiocomina nigra have been re-examined. A new mechanism, the mucus-net method, is described for the first time. This is essentially a method of suspension feeding in which seston is trapped in a net of mucous threads between the arm spines. The entangled material is formed into boluses by simultaneous activities of ciliary currents and the tube-feet and is transported to the mouth by the tube-feet.

Ophiacantha danaemortensen synonymous withOphiocomina nigra(Abildgaard)

Abstract A revision of Norwegian material of Ophiacantha danae Mortensen leads to the conclusion that this species is synonymous with Ophiocomina nigra (Abildgaard). Type specimens of O. danae can not be distinguished from O. nigra by any taxonomic characters of importance.

The Integumentary Mucous Secretions of the Ophiuroid Ophiocomina Nigra

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.

The Colours of Ophiocomina Nigra (Abildgaard): I Colour Variation and its Relation to Distribution

The ophiuroid, Ophiocomina nigra, is noted for its variability of colour, a phenomenon most pronounced where the species also has its greatest distribution in depth. Observations have been made on two geographically distinct populations, from the vicinities of Millport and Plymouth. The body colour of the observed animals ranges in a continuously graded series from black to orange-yellow. While both populations exhibit analogous variations, there is a distinct difference in the range and tone of coloration which each displays. It is suggested that this geographical difference is correlated in some degree with differences in colour tone of the substratum. It was observed that the incidence of light-coloured phases in each population increased with increasing depths, and some statistical evidence supports this conclusion. Thus, at least two factors, depth and substratum, may affect the distribution of colour variations in O. nigraIn addition to the variations in general body colour, there are two distinct colour patterns found on the disk. These are probably truly polymorphic and may be of cryptic value.A scheme of colour classification is described which facilitates observations in the field and in the laboratory.

The Colours OfOphiocomina Nigra(Abildgaard): III. Carotenoid Pigments

The red to orange-yellow colours of the ophiuroid,Ophiocomina nigra, are due to carotenoid pigments contained in specialized lipocytes. These cells are dendritic, with their cell bodies located in the dermis below a melanocyte layer and with dendrites approaching, but not penetrating, the epidermis. The lipocytes are either yellow or orange-red.Five principal pigments were detected in addition to two minor constituents, at least one of which may be an artifact. These major pigments are: β-carotene, an acid carotenoid similar to mytiloxanthin, and four xanthophylls of uncertain identity.

The Colours ofOphiocomina Nigra(Abildgaard): II. The Occurrence of Melanin and Fluorescent Pigments

The ophiuroid,Ophiocomina nigra, displays a colour variation ranging from black to yellow-orange. The pigment responsible for the dark colours has been studied histochemically and by means of chemical techniques applied to extracts. The solubility, oxidation-reduction, fluorescence and other chemical properties of this pigment indicate that it is a true melanin. The visible colour of die melanin depends upon its oxidation state in the integument. Fully oxidized pigment is dark brown; partially reduced pigment is fawn coloured.

Ophiuroids feeding on Phytoplankton

RECENTLY, Nagabhushanam and Colman1 have described carrion-eating by some species of ophiuroids including Ophiocomina nigra (Abild.) and Ophiothrix fragilis (Abild.), from observations both in the laboratory and in the sea, a phenomenon which has been recorded previously2,3. The two species mentioned as well as Ophiopholis aculeata (L.) have, however, been reported to feed on a wide range of food from seston and plankton to bottom invertebrates2,3. In particular, Ophiothrix fragilis and Ophiopholis aculeata are considered to be mainly suspension feeders4,5 (using strong ciliary currents6 in catching detritus), being also facultatively carnivorous. Of the species mentioned, Ophiocomina is anatomically well adapted for a carnivorous habit3. Nevertheless, all the species mentioned are considered to feed in essentially the same way2,3.

Carrion-Eating by Ophiuroids

OPHIUTROIDS are known1,2 to eat a wide range of food, including phytoplankton, zooplankton, polychaetes and detritus; carrion-eating can now be added to the list, for it has recently been observed in this laboratory on the part of Ophiocomina nigra (Abild.), Ophiothrix fragilis(Abild.), Ophiura texturata Lam. and O. abilda Forbes. In aquaria these brittle-stars were seen to eat on one occasion a dead lesser weever (Trachinus viper C. and V.), and on another a small dead cephalopod (Sepiola atlantica d'Orb.). Each ophiuroid's stomach was scarcely everted at all while feeding, but the long tube-feet round the mouth made strong tugging movements, breaking off small pieces from the prey which were later found in the ophiuroid's stomach.

Secretion of a Highly Sulphated Acid Mucopolysaccharide by the Brittle-star, Ophiocomina nigra

THE secretion of a mucus from the tube-feet of ophiuroids is well known1, although the chemical nature of this substance has not been investigated. In a study of the feeding mechanisms of ophiuroids, I find that Ophiocomina nigra (Abildgaard), a common littoral species widespread in the north-east Atlantic and Mediterranean, in addition to the mucin of the tube-feet, secretes all over the body surface an abundant mucus used in conjunction with a detritus-feeding mechanism. Attempts to find the source of this secretion have revealed two types of mucus glands previously undescribed for the species.