Effects of Secondary Metabolites on Digestion in Marine Herbivores

Targett, Nancy M.; Arnold, Thomas

doi:10.1201/9781420036602.sec3

Cited by 52 publications

(52 citation statements)

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“…Research in this field has advanced significantly since the early studies in the 1980's. Laboratory and field based behavioral studies have begun to classify compounds as attractants, protectants or deterrents; however, more recently others have begun to address the physiological and biochemical mechanisms underlying these responses (Targett & Arnold 2001).…”

Section: Introductionmentioning

confidence: 99%

Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance

Whalen¹

2008

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Understanding how organisms deal with potentially toxic or fitness-reducing allelochemicals is important for understanding patterns of predation and herbivory in the marine environment. The ability of marine consumers to tolerate dietary toxins may involve biochemical resistance mechanisms, which increase the hydrophilicity of compounds and facilitate their active efflux out of sensitive cells and tissues. While several allelochemical-responsive detoxification enzymes have been sequenced and functionally characterized in terrestrial invertebrates feeding on chemically defended host plants, there is virtually no information concerning the role of these biotransformation enzymes that may mediate feeding tolerance in marine invertebrates. The objective of this research was to assess the diversity and dietary regulation of cytochrome P450s (CYP), glutathione S-transferases (GST) and ABC transporters in the generalist marine gastropod Cyphoma gibbosum feeding on a variety of chemically defended gorgonian corals, and to identify those dietary natural products that act as substrates for these proteins.Molecular and proteomic techniques identified both allelochemically-responsive CYPs, and constitutively expressed GSTs and transporters in Cyphoma digestive glands. Inhibition of Cyphoma GST activity by gorgonian extracts and selected allelochemicals (i.e., prostaglandins) indicated that gorgonian diets are likely to contain substrates for molluscan detoxification enzymes. In vitro metabolism studies with recombinant CYPs suggested those Cyphoma enzymes most closely related to vertebrate fatty acid hydroxylating enzymes may contribute to the detoxification ofichthyodeterrent cyclopentenone prostaglandins found in abundance in selected gorgonian species. Finally, the presence and activity of multixenobiotic resistance transporters in Cyphoma and the co-occuring specialist nudibranch, Tritonia hamnerorum, suggests these efflux transporters could function as a first line of defense against dietary intoxication. Together, these results suggest marine consumers that regularly exploit allelochemicalrich prey have evolved both general (GST and ABC transporters) and allelochemicalspecific (CYP) detoxification mechanisms to tolerate prey chemical defenses.Thesis Supervisor: Mark E. Hahn Title: Senior Scientist, Biology Department, WHOI COMPLETE ABSTRACT Intense consumer pressure in tropical marine ecosystems not only structures the organization and functioning of marine communities, but has a profound effect on the phenotype of resident organisms. In order to persist in the midst of extreme predation and herbivory, sessile benthic marine organisms, afforded with no means of escape, often produce chemical defenses, termed allelochemicals, which render their tissues unpalatable or toxic to most potential consumers. Despite the fitness-reducing consequences of consuming noxious/toxic prey, less mobile consumers, frequently drawn to their hosts by the chemical refugia they provide, are able to tolerate the toxicological challe...

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Section: Introductionmentioning

confidence: 99%

Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance

Whalen¹

2008

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“…This led us to assume that the grazer Parhyalella penai does not respond to extracted phlorotannins, at least not at the concentrations found in the two studied algae. There might be long-term eVects of phlorotannin consumption, e.g., on reproductive or food-assimilation rates of the amphipod grazers (Cruz-Rivera and Hay 2000; Targett and Arnold 2001), but this was not examined herein. It also should be considered that the highly watersoluble phlorotannins might have leached out of the prepared food pellets during the assays , possibly reducing the deterrence eVect on P. penai.…”

Section: Palatability Of Pellets and The Role Of Phlorotanninsmentioning

confidence: 99%

Species-specific defense strategies of vegetative versus reproductive blades of the Pacific kelps Lessonia nigrescens and Macrocystis integrifolia

et al. 2008

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Chemical defense is assumed to be costly and therefore algae should allocate defense investments in a way to reduce costs and optimize their overall Wtness. Thus, lifetime expectation of particular tissues and their contribution to the Wtness of the alga may aVect defense allocation. Two brown algae common to the SE PaciWc coasts, Lessonia nigrescens Bory and Macrocystis integrifolia Bory, feature important ontogenetic diVerences in the development of reproductive structures; in L. nigrescens blade tissues pass from a vegetative stage to a reproductive stage, while in M. integrifolia reproductive and vegetative functions are spatially separated on diVerent blades. We hypothesized that vegetative blades of L. nigrescens with important future functions are more (or equally) defended than reproductive blades, whereas in M. integrifolia defense should be mainly allocated to reproductive blades (sporophylls), which are considered to make a higher contribution to Wtness. Herein, within-plant variation in susceptibility of reproductive and vegetative tissues to herbivory and in allocation of phlorotannins (phenolics) and N-compounds was compared. The results show that phlorotannin and N-concentrations were higher in reproductive blade tissues for both investigated algae. However, preferences by amphipod grazers (Parhyalella penai) for either tissue type diVered between the two algal species. Fresh reproductive tissue of L. nigrescens was more consumed than vegetative tissue, while the reverse was found in M. integrifolia, thus conWrming the original hypothesis. This suggests that future Wtness function might indeed be a useful predictor of anti-herbivore defense in large, perennial kelps. Results from feeding assays with artiWcial pellets that were made with air-dried material and extract-treated Ulva powder indicated that defenses in live algae are probably not based on chemicals that can be extracted or remain intact after airdrying and grinding up algal tissues. Instead, anti-herbivore defense against amphipod mesograzers seems to depend on structural traits of living algae.

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“…Phlorotannins are a class of polyphenolic compounds found exclusively in brown algae. Their ecological functions, especially as anti-herbivore agents for temperate and tropical species have frequently been discussed (Targett and Arnold 2001;Amsler and Fairhead 2006). Phlorotannins were shown to be present in Antarctic brown algae (Iken 1996;Iken et al 2001;Fairhead et al 2005b), but their ecological significance remains ambiguous Iken unpubl.…”

Section: Chemical and Physical Defences Against Herbivory And Foulingmentioning

confidence: 99%

Life strategy, ecophysiology and ecology of seaweeds in polar waters

Wiencke

Clayton

Gómez

et al. 2006

Rev Environ Sci Biotechnol

136

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Polar seaweeds are strongly adapted to the low temperatures of their environment, Antarctic species more strongly than Arctic species due to the longer cold water history of the Antarctic region. By reason of the strong isolation of the Southern Ocean the Antarctic marine flora is characterized by a high degree of endemism, whereas in the Arctic only few endemic species have been found so far. All polar species are strongly shade adapted and their phenology is finely tuned to the strong seasonal changes of the light conditions. The paper summarises the present knowledge of seaweeds from both polar regions with regard to the following topics: the history of seaweed research in polar regions; the environment of seaweeds in polar waters; biodiversity, biogeographical relationships and vertical distribution of Arctic and Antarctic seaweeds; life histories and physiological thallus anatomy; temperature demands and geographical distribution; light demands and depth zonation; the effect of salinity, temperature and desiccation on supraand eulittoral seaweeds; seasonality of reproduction and the physiological characteristics of C. Wiencke (&) AE U. H. Lü der

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Effects of Secondary Metabolites on Digestion in Marine Herbivores

Cited by 52 publications

References 1 publication

Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance

Functional characterization and expression of molluscan detoxification enzymes and transporters involved in dietary allelochemical resistance

Species-specific defense strategies of vegetative versus reproductive blades of the Pacific kelps Lessonia nigrescens and Macrocystis integrifolia

Life strategy, ecophysiology and ecology of seaweeds in polar waters

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