Predatory Reef Fish Research Articles

Chemical defense of the Caribbean sponge Agelas clathrodes (Schmidt)

Marine sponges have been a rich source of natural products, but only in recent years have studies been undertaken to evaluate the ecological functions of these compounds. Previously, we found that crude organic extracts of the tissues of 6 species of the genus Agelas from the Caribbean were all strongly unpalatable to a predatory reef fish in aquarium assays. In this study, we used bioassay-directed isolation techniques to identify the deterrent metabolites in one of these species, Agelas clathrodes (Schmidt). Crude organic extracts of A. clathrodes at natural concentrations deterred feeding of the reef fish Thalassoma bifasciatum (Bloch) in aquarium assays, and of a natural suite of reef fishes in field assays. Separation of the crude extract by column chromatography yielded a series of fractions, of which only the polar fractions were deterrent in both aquarium and field assays. Two previously described compounds, oroidin ( 1) and 4,5-dibromopyrrol-2-carboxylic acid ( 2), were identified by high resolution mass spectrometry and NMR spectrometry as the deterrent metabolites in the active fractions. Purified samples of both compounds deterred feeding in aquarium assays, both separately and in combination, at concentrations found in the sponge tissue. In addition, both compounds were identified by analytical thin-layer chromatography as constituents of the crude extracts of A. conifera (Schmidt), A. dispar Duchassaing and Michelotti, A. inaequalis Pulitzer-Finali, A. sceptrum (Lamarck), and A. wiedenmeyeri Alcolado. These results suggest that sponges of the genus Agelas share a common chemical defense against fish predators.

Does the skeleton of a sponge provide a defense against predatory reef fish?

Sponge tissue often contains two structural components in high concentrations: spicules of silica, and refractory fibers of protein (spongin). Some terrestrial plants contain analogous structures, siliceous inclusions and refractory lignins, that have been demonstrated to deter herbivory. We performed feeding experiments with predatory reef fish to assess the deterrent properties of the structural components of three common Caribbean demosponges, Agelas clathrodes, Ectyoplasia ferox, and Xestospongia muta. The concentrations of spicules and spongin in the tissues varied widely between the three species, but when assayed at their natural volumetric concentrations, neither spicules (all three species assayed) nor the intact spiculated spongin skeleton (A. clathrodes and X. muta assayed) deterred feeding by reef fish in aquarium or field assays using prepared foods of a nutritional quality similar to, or higher than, that of sponge tissue. Spicules deterred feeding in aquarium assays when incorporated into prepared foods of a nutritional quality lower than that of sponge tissue (15-19 times less protein), but spiculated spongin skeleton was still palatable, even in prepared foods devoid of measurable protein, and even though spicules embedded in spongin were oriented in their natural conformation. Based on comparisons of the nutritional qualities of the tissues of the three sponge species and of the prepared foods, sponge tissue would have to be much lower in food value (5 times less protein or lower) for spicules to provide an effective defense, and spicules in combination with the spongin skeleton would be unlikely to provide an effective defense regardless of the nutritional quality of the tissue. Unlike terrestrial plants, marine sponges may use silica and refractory fibers solely for structural purposes.

Defenses of Caribbean sponges against predatory reef fish. II. Spicules, tissue toughness, and nutritional quality

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 127:195-211 (1995) - doi:10.3354/meps127195 Defenses of Caribbean sponges against predatory reef fish. II. Spicules, tissue toughness, and nutritional quality Chanas B, Pawlik JR Laboratory and field feeding experiments were conducted to assess the palatability to predatory reef fish of prepared foods containing natural concentrations of glass spicules from 8 species of Caribbean reef sponges. Sponge species with high concentrations of spicules in their tissues, and with variable spicule morphologies, were chosen for the experiments. The presence of spicules did not alter food palatability relative to controls for any of the sponges tested. Analyses of ash content, tensile strength, protein, carbohydrate, and lipid content, and total energy content were conducted on tissue samples from 71 species of Caribbean demosponges from reef, mangrove, and grassbed habitats, and compared to previously reported data on the chemical defenses of the same species. There was no evidence to support the hypothesis that sponge species with palatable extracts have higher concentrations of inorganic structural elements, as measured by the mean ash content of their tissues. In addition, the tissues of palatable sponges were not different from those of chemically deterrent species with regard to mean tensile strength, protein content, carbohydrate content, and total energy content, but the tissues of chemically defended species did have a higher mean lipid content than those of palatable species. Sponges that lack chemical antipredatory defenses do not appear to compensate with structural or nutritional defenses, but may instead direct energy otherwise used for the production and storage of secondary metabolites to increased growth and reproduction. Sponge . Defense . Caribbean . Coral reef . Predation . Spicules . Nutritional value . Toughness Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 127. Publication date: November 02, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

Defenses of Caribbean sponges against predatory reef fish. I. Chemical deterrency

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 127:183-194 (1995) - doi:10.3354/meps127183 Defenses of Caribbean sponges against predatory reef fish. I. Chemical deterrency Pawlik JR, Chanas B, Toonen RJ, Fenical W Laboratory feeding assays employing the common Caribbean wrasse Thalassoma bifasciatum were undertaken to determine the palatability of food pellets containing natural concentrations of crude organic extracts of 71 species of Caribbean demosponges from reef, mangrove, and grassbed habitats. The majority of sponge species (69%) yielded deterrent extracts, but there was considerable inter- and intraspecific variability in deterrency. Most of the sponges of the aspiculate orders Verongida and Dictyoceratida yielded highly deterrent extracts, as did all the species in the orders Homosclerophorida and Axinellida. Palatable extracts were common among species in the orders Hadromerida, Poecilosclerida and Haplosclerida. Intraspecific variability was evident, suggesting that, for some species, some individuals (or portions thereof) may be chemically undefended. Reef sponges generally yielded more deterrent extracts than sponges from mangrove or grassbed habitats, but 4 of the 10 most common sponges on reefs yielded palatable extracts (Callyspongia vaginalis, Mycale laevis, Niphates erecta, Iotrochota birotulata), including those most commonly eaten by sponge-eating reef fish. The presence of symbiotic zoanthid cnidarians of the genus Parazoanthus in the tissues of otherwise palatable sponges had little effect on the deterrency of tissue extracts, indicating that these commensal polyps do not confer a chemical defense by association. There was no relationship between sponge color and deterrency, suggesting that sponges are not aposematic and that color variation is the result of other factors. There was also no relationship between the toxicity of sponge extracts (as determined in previous studies) and deterrency, confirming the invalidity of previous assessments of chemical defense based on toxicity. Although chemical antipredatory defenses are important strategies for most Caribbean sponges, some common species appear to rely on other tactics. Sponge . Chemical defense . Caribbean . Coral reef . Predation . Aposematism . Zoanthid Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 127. Publication date: November 02, 1995 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1995 Inter-Research.

A re-evaluation of the ichthyodeterrent role of prostaglandins in the Caribbean gorgonian coral Plexaura homomalla

A re-evaluation of the ichthyodeterrent role of prostaglandins in the Caribbean gorgonian coral Plexaura homomalla

The feeding biology of four predatory reef fishes off the south-eastern Cape coast, South Africa

The feeding of three sparid reef fish, Cheimerius nufar, Petrvs rupestris, Polysteganus praeorbitalis and one serranid, Epinephelus guaza, is described. Examination of stomach contents revealed that C. nufar takes both demersal and pelagic prey. Although reef fish dominate the diets of small C. nufar, larger individuals take pelagic prey frequently. P. rupestris takes reef prey almost exclusively and is an important top predator on hard substrata in the south-eastern Cape. P. praeorbitalis preys mainly on reef fishes and is found mainly in shallow water in this region. Hunting behaviour for both solitary and grouped prey by these sparids has been recorded from underwater observations in the wild, and in tanks. E. guaza is a solitary ambush predator of small fish, crabs and octopods. All four species show clear ontogenetic changes in diet and overlaps in their resource use are discussed.