The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Joseph R. Pawlik - One of the best experts on this subject based on the ideXlab platform.
-
Variability in the Chemical Defense of the sponge Chondrilla nucula against predatory reef fishes
Marine Biology, 1998Co-Authors: David C Swearingen, Joseph R. PawlikAbstract:Chondrilla nucula is a common Caribbean demosponge that grows in a range of habitats, from coral reefs to mangrove swamps. On reefs, C. nucula grows as a thinly encrusting sheet, while in mangrove habitats it surrounds submerged mangrove roots as fleshy, lobate clumps. Previous feeding experiments using predatory reef fish revealed a high degree of variability in the Chemical Defenses of C. nucula. The present study was undertaken to determine whether a relationship exists between habitat, growth form, and Chemical Defense of C. nucula. Both laboratory and field feeding-assays of crude extracts confirmed that C. nucula possesses a Chemical Defense with high intercolony variability, but there was no significant variation in feeding deterrency between reef and mangrove habitats at either geographic location (Bahamas and Florida). Extracts of C. nucula collected during September and October 1994 from the Bahamas were significantly more deterrent than those collected during August 1993, May 1994, and May 1995 from Florida, and extracts of these spring and summer Florida collections were more deterrent than extracts of C. nucula collected in December 1994 and February 1995 in the same locations. There was no evidence that deterrent compounds were concentrated in the surface tissues of the sponge, or that Chemical Defense could be induced by simulated predation. Laboratory and field assays of the fractionated crude extract revealed that feeding deterrency was confined to the most polar metabolites in the extract. Field transplants were used to determine whether predation influenced the growth form of C. nucula. Uncaged sponges transplanted from the mangrove to the reef were readily consumed by spongivorous reef fishes. Lobate mangrove sponges became thinner after being caged on the reef for 3 mo, but encrusting reef sponges did not become thicker after being caged in the mangroves for the same period of time. Reef sponges that were caged for 3 to 15 mo thickened by only a small amount (
-
variability in the Chemical Defense of the sponge chondrilla nucula against predatory reef fishes
Marine Biology, 1998Co-Authors: David C Swearingen, Joseph R. PawlikAbstract:Chondrilla nucula is a common Caribbean demosponge that grows in a range of habitats, from coral reefs to mangrove swamps. On reefs, C. nucula grows as a thinly encrusting sheet, while in mangrove habitats it surrounds submerged mangrove roots as fleshy, lobate clumps. Previous feeding experiments using predatory reef fish revealed a high degree of variability in the Chemical Defenses of C. nucula. The present study was undertaken to determine whether a relationship exists between habitat, growth form, and Chemical Defense of C. nucula. Both laboratory and field feeding-assays of crude extracts confirmed that C. nucula possesses a Chemical Defense with high intercolony variability, but there was no significant variation in feeding deterrency between reef and mangrove habitats at either geographic location (Bahamas and Florida). Extracts of C. nucula collected during September and October 1994 from the Bahamas were significantly more deterrent than those collected during August 1993, May 1994, and May 1995 from Florida, and extracts of these spring and summer Florida collections were more deterrent than extracts of C. nucula collected in December 1994 and February 1995 in the same locations. There was no evidence that deterrent compounds were concentrated in the surface tissues of the sponge, or that Chemical Defense could be induced by simulated predation. Laboratory and field assays of the fractionated crude extract revealed that feeding deterrency was confined to the most polar metabolites in the extract. Field transplants were used to determine whether predation influenced the growth form of C. nucula. Uncaged sponges transplanted from the mangrove to the reef were readily consumed by spongivorous reef fishes. Lobate mangrove sponges became thinner after being caged on the reef for 3 mo, but encrusting reef sponges did not become thicker after being caged in the mangroves for the same period of time. Reef sponges that were caged for 3 to 15 mo thickened by only a small amount (<1 mm) compared to uncaged and open-caged (i.e. in cages lacking tops) sponges. Simulated bite marks on both reef and mangrove sponges were repaired at a rapid rate (0.8 to 1.6 mm d−1). Fish predation has an important impact on the distribution and abundance of C. nucula, but the thin growth form common to reef environments may be more the result of hydrodynamics than of grazing by spongivorous fishes.
-
Chemical Defense of the caribbean sponge agelas clathrodes schmidt
Journal of Experimental Marine Biology and Ecology, 1997Co-Authors: Brian Chanas, Joseph R. Pawlik, Thomas Lindel, William FenicalAbstract: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.
David C Swearingen - One of the best experts on this subject based on the ideXlab platform.
-
Variability in the Chemical Defense of the sponge Chondrilla nucula against predatory reef fishes
Marine Biology, 1998Co-Authors: David C Swearingen, Joseph R. PawlikAbstract:Chondrilla nucula is a common Caribbean demosponge that grows in a range of habitats, from coral reefs to mangrove swamps. On reefs, C. nucula grows as a thinly encrusting sheet, while in mangrove habitats it surrounds submerged mangrove roots as fleshy, lobate clumps. Previous feeding experiments using predatory reef fish revealed a high degree of variability in the Chemical Defenses of C. nucula. The present study was undertaken to determine whether a relationship exists between habitat, growth form, and Chemical Defense of C. nucula. Both laboratory and field feeding-assays of crude extracts confirmed that C. nucula possesses a Chemical Defense with high intercolony variability, but there was no significant variation in feeding deterrency between reef and mangrove habitats at either geographic location (Bahamas and Florida). Extracts of C. nucula collected during September and October 1994 from the Bahamas were significantly more deterrent than those collected during August 1993, May 1994, and May 1995 from Florida, and extracts of these spring and summer Florida collections were more deterrent than extracts of C. nucula collected in December 1994 and February 1995 in the same locations. There was no evidence that deterrent compounds were concentrated in the surface tissues of the sponge, or that Chemical Defense could be induced by simulated predation. Laboratory and field assays of the fractionated crude extract revealed that feeding deterrency was confined to the most polar metabolites in the extract. Field transplants were used to determine whether predation influenced the growth form of C. nucula. Uncaged sponges transplanted from the mangrove to the reef were readily consumed by spongivorous reef fishes. Lobate mangrove sponges became thinner after being caged on the reef for 3 mo, but encrusting reef sponges did not become thicker after being caged in the mangroves for the same period of time. Reef sponges that were caged for 3 to 15 mo thickened by only a small amount (
-
variability in the Chemical Defense of the sponge chondrilla nucula against predatory reef fishes
Marine Biology, 1998Co-Authors: David C Swearingen, Joseph R. PawlikAbstract:Chondrilla nucula is a common Caribbean demosponge that grows in a range of habitats, from coral reefs to mangrove swamps. On reefs, C. nucula grows as a thinly encrusting sheet, while in mangrove habitats it surrounds submerged mangrove roots as fleshy, lobate clumps. Previous feeding experiments using predatory reef fish revealed a high degree of variability in the Chemical Defenses of C. nucula. The present study was undertaken to determine whether a relationship exists between habitat, growth form, and Chemical Defense of C. nucula. Both laboratory and field feeding-assays of crude extracts confirmed that C. nucula possesses a Chemical Defense with high intercolony variability, but there was no significant variation in feeding deterrency between reef and mangrove habitats at either geographic location (Bahamas and Florida). Extracts of C. nucula collected during September and October 1994 from the Bahamas were significantly more deterrent than those collected during August 1993, May 1994, and May 1995 from Florida, and extracts of these spring and summer Florida collections were more deterrent than extracts of C. nucula collected in December 1994 and February 1995 in the same locations. There was no evidence that deterrent compounds were concentrated in the surface tissues of the sponge, or that Chemical Defense could be induced by simulated predation. Laboratory and field assays of the fractionated crude extract revealed that feeding deterrency was confined to the most polar metabolites in the extract. Field transplants were used to determine whether predation influenced the growth form of C. nucula. Uncaged sponges transplanted from the mangrove to the reef were readily consumed by spongivorous reef fishes. Lobate mangrove sponges became thinner after being caged on the reef for 3 mo, but encrusting reef sponges did not become thicker after being caged in the mangroves for the same period of time. Reef sponges that were caged for 3 to 15 mo thickened by only a small amount (<1 mm) compared to uncaged and open-caged (i.e. in cages lacking tops) sponges. Simulated bite marks on both reef and mangrove sponges were repaired at a rapid rate (0.8 to 1.6 mm d−1). Fish predation has an important impact on the distribution and abundance of C. nucula, but the thin growth form common to reef environments may be more the result of hydrodynamics than of grazing by spongivorous fishes.
Georg Pohnert - One of the best experts on this subject based on the ideXlab platform.
-
conserved and species specific oxylipin pathways in the wound activated Chemical Defense of the noninvasive red alga gracilaria chilensis and the invasive gracilaria vermiculophylla
Beilstein Journal of Organic Chemistry, 2012Co-Authors: Martin Rempt, Florian Weinberger, Katharina Grosser, Georg PohnertAbstract:Chemical Defense of the invasive red alga Gracilaria vermiculophylla has been studied and compared to that of the noninvasive but related Gracilaria chilensis. Both species rely on a wound-activated Chemical Defense that makes them less attractive to the herbivorous sea snail Echinolittorina peruviana. The Chemical stress response of both species was monitored by LC–ESIMS-based metabolic profiling and revealed commonalities and differences. Both algae rely on a rapid lipoxygenase mediated transformation of arachidonic acid to known and novel oxylipins. Common products are 7,8-dihydroxyeicosatetraenoic acid and a novel eicosanoid with an unusual γ-lactone moiety. Several prostaglandins were predominantly formed by the invasive species. The role of some of these metabolites was investigated by surveying the attachment of E. peruviana on artificial food containing the respective oxylipins. Both algae species are defended against this general herbivore by 7,8-dihydroxyeicosatetraenoic acid, whereas the prostaglandins and the novel oxylipins were inactive at naturally occurring concentrations. The role of different oxylipins in the invasive potential of Gracilaria spp. is discussed.
-
diatom copepod interactions in plankton the indirect Chemical Defense of unicellular algae
ChemBioChem, 2005Co-Authors: Georg PohnertAbstract:Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that Chemical signals and Chemical Defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use Chemical Defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the Chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a Chemical Defense for the plankton community structure are also discussed.
-
diatom copepod interactions in plankton the indirect Chemical Defense of unicellular algae
ChemBioChem, 2005Co-Authors: Georg PohnertAbstract:Max-Planck-Institut fur Chemische Okologie, Hans-Knoll-Strasse 8, 07745 Jena, Germany. pohnert@ice.mpg.de Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that Chemical signals and Chemical Defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use Chemical Defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the Chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a Chemical Defense for the plankton community structure are also discussed.
-
Diatom/copepod interactions in plankton: The indirect Chemical Defense of unicellular algae
Chembiochem : a European journal of chemical biology, 2005Co-Authors: Georg PohnertAbstract:Numerous coexisting species can be observed in the open oceans. This includes the complex community of the plankton, which comprises all free floating organisms in the sea. Traditionally, nutrient limitation, competition, predation, and abiotic factors have been assumed to shape the community structure in this environment. Only in recent years has the idea arisen that Chemical signals and Chemical Defense can influence species interactions in the plankton as well. Key players at the base of the marine food web are diatoms (unicellular algae with silicified cell walls) and their main predators, the herbivorous copepods. It was assumed that diatoms represent a generally good food source for the grazers but recent work indicates that some species use Chemical Defenses. Secondary metabolites, released by these algae immediately after wounding, are targeted not against the predators themselves but rather at interfering with their reproductive success. This strategy allows diatoms to reduce the grazer population, thereby influencing the marine food web. This review addresses the Chemical ecology of the defensive oxylipins formed by diatoms and the question of how these metabolites can act in such a dilute environment. Aspects of biosynthesis, bioassays, and the possible implications of such a Chemical Defense for the plankton community structure are also discussed.
-
Chemical Defense strategies of marine organisms
Topics in current chemistry, 2004Co-Authors: Georg PohnertAbstract:The diverse habitats of the marine environment and the adaptation required to live either in the open water or attached to a substrate resulted in various Defense strategies. This review covers different ways how organisms from the plankton can maintain a Chemical Defense as well as the dynamic Chemical Defense strategies of benthic organisms. It opens with a detailed discussion of recent studies of Chemical Defenses among organisms floating in the open water. These Defenses include the production of toxins by harmful algal blooms as well as the rapid production of defensive metabolites from non-toxic precursors upon cell disruption. A comprehensive account of recent advances in the field of dynamic Chemical Defense strategies of benthic organisms is then presented. It includes the known examples of activated Defense based on the enzymatic transformation of storage metabolites as well as induced Chemical Defense strategies. These strategies depend on the recognition of signals from an herbivore or pathogen, followed by the up-regulation of the biosynthesis of metabolites involved in the Chemical Defense.
Michael Heethoff - One of the best experts on this subject based on the ideXlab platform.
-
Temperature Affects Chemical Defense in a Mite-Beetle Predator-Prey System
Journal of Chemical Ecology, 2020Co-Authors: Christoph Merkel, Michael Heethoff, Adrian BrücknerAbstract:Temperature influences all bioChemical and biophysiological processes within an organism. By extension, it also affects those ecological interactions that are mediated by gland-produced Chemical compounds, such as reservoir-based Chemical Defense. Herein, we investigate how environmental temperature affects the regeneration of defensive secretions and influences the efficacy of Chemical Defense in a model predator-prey system: the oribatid mite Archegozetes longisetosus and the predaceous rove beetle Stenus juno . Through a combination of Chemical analyses, non-linear regression modeling and theoretical simulations we show that the amount of defensive secretion responded to temperature in a unimodal optimum curve: the regeneration rate followed a positive, linear relationship up to 35 °C, but rapidly broke down beyond this temperature (“tipping point” effect). Using functional response simulations, there is an initially positive dampening effect on the predation rate when regeneration is optimal, but at higher temperatures Chemical Defense does not counteract the previously described effects of elevated predatory pressure. In a larger context, our results demonstrate the need to integrate relevant environmental factors in predator-prey modeling approaches.
-
the effect of reservoir based Chemical Defense on predator prey dynamics
Theoretical Ecology, 2019Co-Authors: Tatjana Thiel, Michael Heethoff, Adrian Brückner, Andreas Brechtel, Barbara DrosselAbstract:Numerous animal species use Defense mechanisms such as Chemical secretion to defend against attacks of predators. Although Defense mechanisms have the potential to considerably change the dynamics and stability of a system, few theoretical studies exist. In this paper, we focus on predator-prey systems with reservoir-based Chemical Defense, which is also called “reducible Defense” and is widespread among invertebrates. The predator has to attack often enough to disarm and consume prey, and prey can biosynthetically restore lost secretion. The model includes these features in the functional response, and in a separate equation for the stored amount of secretion. Additionally, our model takes into account that Defense involves metabolic costs, reducing population growth of the prey. By performing computer simulations, we show that the Defense mechanism causes the predator to take more time to consume prey. This time is increased more efficiently when the prey invests in a large reservoir rather than in fast restoration of secretion. We also investigate the stationary states resulting on longer time scales, finding that both predator and prey can become considerably more abundant due to the Defense mechanism. However, investment into Defenses pays off only when predator density is large enough and costs of Defense are not too high.
-
Nutritional effects on Chemical Defense alter predator–prey dynamics
Chemoecology, 2018Co-Authors: Adrian Brückner, Michael HeethoffAbstract:Reservoir-based Chemical Defense (= reducible Defense) is a widespread mechanism to repel predators in many invertebrates. We investigated the influence of macronutrients on the availability and regeneration of defensive secretions and parametrize a theoretical functional response model for reducible Defense to predict nutritional effects on predator–prey dynamics. Our modeling approach showed that initially high amounts of defensive secretions provided an effective short-time Defense, while higher regeneration rates were favorable under permanent predation pressure. Regeneration rates were correlated to the amount of dietary fat and carbohydrates, indicating an adaptive connection of macronutrients on Chemical Defense and predatory success—an effect covering two trophic levels. Our results underpin the urgent need to integrate dynamical aspects of Chemical Defense into the modeling of predator–prey interactions in food webs.
-
tasty but protected first evidence of Chemical Defense in oribatid mites
Journal of Chemical Ecology, 2011Co-Authors: Michael Heethoff, Lars Koerner, Roy A Norton, Gunther RaspotnigAbstract:Oribatid mites (Acari, Oribatida) represent one of the most abundant and speciose groups of microarthropods in the decomposer food webs of soils, but little is known of their top-down regulation by predators. Oribatids are relatively long-lived and have numerous morphological defensive adaptations, and so have been proposed to live in ‘enemy-free space’. Most also possess a pair of large exocrine oil glands that produce species-specific mixtures of hydrocarbons, terpenes, aromatics, and alkaloids with presumably allomonal functions, although their adaptive value has never been tested empirically. We developed a protocol that discharges the oil glands of the model oribatid species, Archegozetes longisetosus. and offered ‘disarmed’ individuals as prey to polyphagous Stenus beetles (Staphylinidae), using untreated mites as controls. Stenus juno fed on disarmed mites with behavioral sequences and success rates similar to those observed when they prey on springtails, a common prey. In contrast, mites from the control group with full glands were almost completely rejected; contact with the gland region elicited a strong reaction and cleaning behavior in the beetle. This is the first evidence of an adaptive value of oribatid mite oil gland secretions for Chemical Defense. The protocol of discharging oil glands should facilitate future studies on top-down control of oribatid mites that aim to differentiate between morphological and Chemical aspects of defensive strategies.
Adrian Brückner - One of the best experts on this subject based on the ideXlab platform.
-
Temperature Affects Chemical Defense in a Mite-Beetle Predator-Prey System
Journal of Chemical Ecology, 2020Co-Authors: Christoph Merkel, Michael Heethoff, Adrian BrücknerAbstract:Temperature influences all bioChemical and biophysiological processes within an organism. By extension, it also affects those ecological interactions that are mediated by gland-produced Chemical compounds, such as reservoir-based Chemical Defense. Herein, we investigate how environmental temperature affects the regeneration of defensive secretions and influences the efficacy of Chemical Defense in a model predator-prey system: the oribatid mite Archegozetes longisetosus and the predaceous rove beetle Stenus juno . Through a combination of Chemical analyses, non-linear regression modeling and theoretical simulations we show that the amount of defensive secretion responded to temperature in a unimodal optimum curve: the regeneration rate followed a positive, linear relationship up to 35 °C, but rapidly broke down beyond this temperature (“tipping point” effect). Using functional response simulations, there is an initially positive dampening effect on the predation rate when regeneration is optimal, but at higher temperatures Chemical Defense does not counteract the previously described effects of elevated predatory pressure. In a larger context, our results demonstrate the need to integrate relevant environmental factors in predator-prey modeling approaches.
-
the effect of reservoir based Chemical Defense on predator prey dynamics
Theoretical Ecology, 2019Co-Authors: Tatjana Thiel, Michael Heethoff, Adrian Brückner, Andreas Brechtel, Barbara DrosselAbstract:Numerous animal species use Defense mechanisms such as Chemical secretion to defend against attacks of predators. Although Defense mechanisms have the potential to considerably change the dynamics and stability of a system, few theoretical studies exist. In this paper, we focus on predator-prey systems with reservoir-based Chemical Defense, which is also called “reducible Defense” and is widespread among invertebrates. The predator has to attack often enough to disarm and consume prey, and prey can biosynthetically restore lost secretion. The model includes these features in the functional response, and in a separate equation for the stored amount of secretion. Additionally, our model takes into account that Defense involves metabolic costs, reducing population growth of the prey. By performing computer simulations, we show that the Defense mechanism causes the predator to take more time to consume prey. This time is increased more efficiently when the prey invests in a large reservoir rather than in fast restoration of secretion. We also investigate the stationary states resulting on longer time scales, finding that both predator and prey can become considerably more abundant due to the Defense mechanism. However, investment into Defenses pays off only when predator density is large enough and costs of Defense are not too high.
-
Nutritional effects on Chemical Defense alter predator–prey dynamics
Chemoecology, 2018Co-Authors: Adrian Brückner, Michael HeethoffAbstract:Reservoir-based Chemical Defense (= reducible Defense) is a widespread mechanism to repel predators in many invertebrates. We investigated the influence of macronutrients on the availability and regeneration of defensive secretions and parametrize a theoretical functional response model for reducible Defense to predict nutritional effects on predator–prey dynamics. Our modeling approach showed that initially high amounts of defensive secretions provided an effective short-time Defense, while higher regeneration rates were favorable under permanent predation pressure. Regeneration rates were correlated to the amount of dietary fat and carbohydrates, indicating an adaptive connection of macronutrients on Chemical Defense and predatory success—an effect covering two trophic levels. Our results underpin the urgent need to integrate dynamical aspects of Chemical Defense into the modeling of predator–prey interactions in food webs.