Marine natural products.  VIII.  Pachydictyol A, an exceptional diterpene alcohol from the brown alga, Pachydictyon coriaceum

The Structurally similar diterpenoid alcohols pachydictyol-A and dictyol-E are produced by the brown seaweed Dictyota dichotoma. This seaweed and several related species that also produce these compounds are known to be relatively low preference foods for tropical fishes and urchins. We evaluated the effect of various concentrations of these compounds on feeding by the three common types of herbivores that co-occur with Dictyota in coastal North Carolina. Fish (Diplodus holbrooki), sea urchins (Arbacia punctulata), and a mixed species group of gammarid amphipods were offered pieces of the palatable seaweed Gracilaria tikvahiae coated with either (1) dictyol-E or pachydictyol-A dissolved in diethyl ether or (2) diethyl ether alone. Dictyol-E significantly reduced consumption by fish and urchins at concentrations of 0.5 and 1.0% of algal dry mass, but had no effect on amphipod grazing. Pachydictyol-A significantly reduced fish grazing at the relatively high concentrations of 1.0 and 1.3% of plant dry mass; at 0.5% it tended to decrease grazing, but the effect was not significant (P = .07). Pachydictyol-A had no effect on urchin grazing and significantly increased amphipod grazing. When Pachydictyol-A was fed to fish as 1.0% of food dry mass, their growth rate was reduced by a significant 48%. In feeding preference experiments with several seaweeds, Dictyota ranks low for fish and urchins but high for amphipods. This is consistent with the hypothesis that the secondary metabolites produced by Dictyota play a major role in determining its susceptibility to herbivores. The ability of amphipods to circumvent the chemical defenses (Dictyota, and the fact that the two species of algae most readily consumed by amphipods (Codium and Dictyota) were the two species least readily consumed by fish, suggest that predation and herbivory by fishes may be major factors selecting for amphipods that can live on, and eat, seaweeds that are unpalatable to fishes. Amphipods that fed on Dictyota did not appear to sequester the Dictyota metabolites; when exposed to fish predation, Dictyota-fed amphipods were eaten as readily as amphipods that had fed on an alga with no defensive chemistry. Tubicolous amphipods and other small marine herbivores that may spend significant portions of their lives on only a few plants my be under very different evolutionary constraints than the larger, more mobile herbivores that commonly moved between many plants. Several characteristics of these smaller, less mobile, and much less studied, marine herbivores suggest that they may be ecologically similar to terrestrial insects and may play a large, but presently unappreciated, role in structuring marine plant communities.

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“…1) are relatively well studied (Hirschfeld et al 1973, McEnroe et al 1977, Norris and Fenical 1982, Hay et al 1987). …”

Section: Study Site and Organismsmentioning

confidence: 99%

Chemical Defense Against Different Marine Herbivores: Are Amphipods Insect Equivalents?

Hay¹,

Duffy²,

Pfister³

et al. 1987

Ecology

339

319

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“…Chadefaud (1956) suggested that Ando's terpene-physodes were actuaüy fat-bodies which might additionally contain a small amount of terpene. Terpenes have recently been isolated from brown algae (Katayama 1964;Hirschfeld et al 1973), and many terpenes have been shown to colour from blue to red with vanillin-hydrochloric acid (Attaway et al 1965).…”

Section: Evidencefor the Presence Ofterpenesmentioning

confidence: 99%

Physodes and the Phenolic Compounds of Brown Algae. Composition and Significance of Physodes in vivo

Ragan¹

1976

Botanica Marina

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The composition and significance of physodes, brown algal subcellulai bodies characterized by reactivity with vanillin-hydrochloric acid, have been the subject of debate for the past Century. This research is critically reviewed, and it is demonstrated that aJthough physodes aie primarily composed of phloroglucinol derivatives, they may also contain other tannins and terpenes. The recent discoveries of homologous series of phloroglucinol polymers in brown algal extracts provide an attractive chemical rationalization for the observed heterogeneity of physodes.

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“…Phenolic or related compounds have been isolated from 3 species of Phaeophyta, Zonaria furlowii (Gerwick & Fenical 1982), Dictyopteris undulata (Welch & Prakasa Rao 1978, Gerwick et al 1981, and Puchydictyon coriaceum (Hirschfeld et al 1973, Ishitsuka et al 1982, used in preferences studies, and were among the least preferred of all species tested. Surgussum muticum, recently introduced from Japan to this coast, ranked low in preference for all three herbivores, perhaps due to its known phenolic content (Glombitza et al 1978, Steinberg 1986).…”

Section: Discussionmentioning

confidence: 99%

Diet, food preference, and algal availability for fishes and crabs on intertidal reef communities in southern California

Barry

Ehret

1993

Environ Biol Fish

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SynopsisHerbivory by wide-ranging fishes is common over tropical reefs, but rare in temperate latitudes where the effects of herbivorous fishes are thought to be minimal. Along the west coast of North America, herbivory by fishes on nearshore reefs is largely restricted to a few members of the Kyphosidae, distributed south of Pt. Conception. This paper presents information on natural diets and results from feeding choice experiments for two abundant kyphosids from intertidal habitats in San Diego, California -Girella nigricans and Hermosilla azurea, and similar data for the lined shore crab, Pachygrapsus crassipes, which also forages over intertidal reefs. These results are compared with the availability of algae in intertidal habitats measured during summer and winter, on both disturbed and undisturbed habitats. The diets of juveniles of G. nigricans and H. azurea collected from nearshore habitats were dominated by animal prey (mainly amphipods), but adults of these fishes, and P. crassipes, consumed algae nearly exclusively, with 26,10, and 14 taxa of algae identified from G. nigricans, H. azurea, and P. crassipes, respectively. Algae with sheet-like morphologies (e.g. Ulva sp., Enteromorpha sp., members of the Delesseriaceae) were the principal algae in the diets of the fishes, and calcareous algae (e.g. Corallina sp., Lithothrix aspergillum) and sheet-like algae (Enteromorpha sp.) comprised the greatest identifiable portion of the shore crab's diet. Feeding choice experiments indicated that the fishes preferred filamentous algae (e.g. Centroceras clavulatum, Polysiphonia sp., Chondria californica) and sheet-like algae (e.g. Enteromorpha sp., Ulva sp., Cryptopleura crispa) over other algal morphologies, whereas the shore crab chose jointed calcareous algae (e.g. Lithothrix aspergillum, Corallina vancouveriensis, Jania sp.) most frequently. The diets and preferences for algae by the fishes were generally most similar to the assemblage of algae available in early successional (disturbed) habitats during summer when sheet-like and filamentous algae are abundant. The shore crab exhibited the opposite trend with a diet more similar to late successional (undisturbed) habitats.

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Marine natural products. VIII. Pachydictyol A, an exceptional diterpene alcohol from the brown alga, Pachydictyon coriaceum

Abstract: Recently we reported1•2 results for the gas-phase pro-

Cited by 82 publications

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Chemical Defense Against Different Marine Herbivores: Are Amphipods Insect Equivalents?

Chemical Defense Against Different Marine Herbivores: Are Amphipods Insect Equivalents?

Physodes and the Phenolic Compounds of Brown Algae. Composition and Significance of Physodes in vivo

Diet, food preference, and algal availability for fishes and crabs on intertidal reef communities in southern California

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