Coelenterate Genus

Friedrich August von Quenstedt (1809-1889), German geologist and palaeontologist. Five genera are named after him including the bivalve mollusc genus Quenstedtia (Morris and Lycett 1854), the coelenterate genus Quenstedtia (Rominger 1876), the coelenterate genus Quenstedtiphyllia (Melnikova 1975), the ammonite genus Quenstedtoceras (Hyatt, 1876), and the crinoid genus Quenstedticrinus (Klikushin 1987). This artwork dates from 1870.

coelenterate genus

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STATOCYSTS are sensory organs which detect the direction of gravitational force, and usually consist of a vesicle which contains a nodule (statolith) resting on a bed of sensory hairs (generally cilia). Changes in orientation cause the statolith to roll onto and stimulate new groups of hairs which pass information to the nervous system. This pattern is true of most coelenterate statocysts1. I wish to describe a coelenterate statocyst in which cilia and nerves are absent, the statolith resting directly on the wall of its vesicle.

Hydra (Cnidaria) is the first animal organism to have developed a neural network, which has been proposed to control, inter alia, the "feeding response", i.e. a mechanism through which the coelenterate opens and then closes its mouth in the presence of prey and/or glutathione. Here, we report that Hydra contains: (i) selective cannabinoid binding sites; (ii) the endogenous cannabinoid receptor ligand, anandamide (arachidonoylethanolamide); (iii) a fatty acid amide hydrolase-like activity catalysing anandamide hydrolysis; and (iv) the putative biosynthetic precursor of anandamide, N-arachidonoylphosphatidylethanolamine. We suggest that this "endogenous cannabinoid system" is involved in the modulation of the "feeding response". Anandamide (1 nM-1 microM) potently inhibited (up to 45%) the glutathione-induced "feeding response" by accelerating Hydra vulgaris mouth closure. The effect was maximal at 100 nM anandamide and was reversed by the selective antagonist of the CB1 subtype of mammalian cannabinoid receptors, SR 141716A (50-100 nM). Specific cannabinoid binding sites were detected in membranes from Hydra polyps by using [3H]SR 141716A (Kd= 1.87 nM, Bmax = 26.7 fmol/mg protein), and increasing anandamide concentrations were found to displace the binding of [3H]SR 141716A to these membranes (Ki = .505 nM). Hydra polyps were also found to contain amounts of anandamide (15.6 pmol/g) and N-arachidonoylphosphatidylethanolamine (32.4 pmol/g), as well as the other "endocannabinoid" 2-arachidonoylglycerol (11.2 nmol/g), comparable to those described previously for mammalian brain. Finally, a fatty acid amide hydrolase activity (Vmax = 3.4 nmol/min/mg protein), with subcellular distribution, pH dependency and sensitivity to inhibitors similar to those reported for the mammalian enzyme, but with a lower affinity for anandamide (Km = 400 microM), was also detected in Hydra polyps. These data suggest that the endocannabinoid signalling system plays a physiological role in Hydra that is to control the feeding response. Hydra is the simplest living organism described so far to use this recently discovered regulatory system.

This paper reviews the literature data on the composition, structure, and distribution of the main lipid classes and their fatty acids in reef-building and soft corals and in hydrocorals of the genus Millepora. The review presents information about more than 150 coral species from tropical and cold waters of the World Ocean, as well as data on the influence of environmental factors on the lipid compositions of corals. The possible pathways of polyunsaturated fatty acid biosynthesis in corals are discussed.

Fautin, D.G. & Chia, F.S. 1986. Revision of sea anemone genus Epiactis (Coelenterata: Actiniaria) on the Pacific coast of North America, with descriptions of two new brooding species. Can. J. Zool., 64: 1665-1674. -250

Grebernyi, S.D. 1980. Distribution of sea anemones in the Arctic. In: D.V. Naumov & S.D. Stepanjants (eds). Teoreticheskoe i prakticheskoe znachenie kishechnopolostnykh [The theoretical and practical importance of the coelenterates]: 20-33. Leningrad. (In Russian).

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