Five of the most common macrophytes from an aquaculture facility with high densities of the herbivorous Asian grass carp (Ctenopharyngodon idella) were commonly unpalatable to three generalist ...consumers--grass carp and the native North American crayfishes Procambarus spiculifer and P. acutus. The rooted vascular plant Micranthemum umbrosum comprised 89% of the total aboveground plant biomass and was unpalatable to all three consumers as fresh tissues, as homogenized pellets, and as crude extracts. Bioassay-guided fractionation of the crude extract from M. umbrosum led to four previously known compounds that each deterred feeding by at least one consumer: 3,4,5-trimethoxyallylbenzene (1) and three lignoids: β-apopicropodophyllin (2); (-)-(3S,4R,6S)-3-(3',4'-methylenedioxy-α-hydroxybenzyl)-4-(3",4"-dimethoxybenzyl)butyrolactone (3); and (-)-hibalactone (4). None of the remaining four macrophytes produced a chemically deterrent extract. A 16-mo manipulative experiment showed that the aboveground biomass of M. umbrosum was unchanged when consumers were absent, but the biomass of Ludwigia repens, a plant that grass carp preferentially consumed over M. umbrosum, increased over 300-fold. Thus, selective feeding by grass carp effectively eliminates most palatable plants from this community and promotes the persistence of the chemically defended M. umbrosum, suggesting that plant defenses play critical yet understudied roles in the structure of freshwater plant communities.
Four novel alkaloids, lepadins B (
2) and C (
3) and villatamines A (
4) and B (
5), have been isolated from the predatory flatworm Prostheceraeus villatus and its tunicate prey Clavelina ...lepadiformis. Lepadins A (
1) and B (
2) and villatamine B (
5) exhibit significant in vitro cytotoxicity against human cancer cell lines.
Four novel alkaloids, lepadins B (
2) and C (
3) and villatamines A (
4) and B (
5), have been isolated from the predatory flatworm
Prostheceraeus villatus and its tunicate prey
Clavelina lepadiformis. The lepadins and villatamines exhibit significant
in vitro cytotoxicity.
Three novel 2-alkylpyrrole sulfamates (1−3) were isolated from the marine worm Cirriformia tentaculata. The structures were elucidated by the interpretation of spectral data obtained on inseparable ...mixtures of the unstable compounds. This suite of metabolites deterred feeding by the generalist predatory fish Thalassoma bifasciatum.
Stable isotope incorporation studies with 1,2-13C2acetate, 1,2-13C2,18O1acetate, and 2-13Cmevalonolactone have been used to investigate the biosynthesis of the terpenoids albicanyl acetate (1), ...cadlinaldehyde (2), and luteone (3) by the dorid nudibranch Cadlina luteomarginata. The results have shown that all three terpenoids are synthesized de novo by C. luteomarginata and the incorporation patterns are consistent with the biogenetic proposal that the new cadlinalane and luteane carbon skeletons are formed by degradation of a sesterterpenoid precursor. This represents the first demonstration of sesterterpenoid biosynthesis by a marine mollusc. Quantitative analysis has shown that only a small turnover of metabolites takes place during the feeding experiments but that the newly formed molecules have extremely high levels of incorporation of labeled precursors.
Stable isotope incorporation experiments using sodium 1, 2-13C2acetate have demonstrated that the 3-hydroxybutyrate substituent of diaulusterol A (1) is biosynthesized de novo by the dorid nudibranch ...Diaulula sandiegensis. There was no evidence for acetate incorporation into the steroid portion of 1, nor were radiolabeled mevalonate or cholesterol incorporated.
Gas chromatography (GC) analyses of whole animal skin extracts and individual tissue extracts obtained from specimens of Cadlina luteomarginata collected in British Columbia and southern California ...were used to determine if concentrations of the nudibranch's biosynthetic products--albicanyl acetate (1), cadlinaldehyde (2), and luteone (3)--vary significantly between two populations, among individuals of a population, and among body tissues of individual specimens. The major biosynthetic product, albicanyl acetate (1), has the same concentration in both British Columbia and California populations, while the British Columbia population contains greater total amounts of 2 and 3 than the California population. Within individuals from one population, the largest proportion of endogenous metabolites is in the dorsum, specifically in the mantle dermal formations and margins. The GC analyses show that across geographically separated populations and within geographically localized populations the concentration of endogenous metabolites is inversely correlated with availability of structurally similar compounds from dietary sources. This suggests that the de novo biosynthesis of defensive compounds might be regulated according to need.PUBLICATION ABSTRACT
A chiral synthesis of tri-
O-methylimbricatine (
2), the tri-
O-methyl derivative of the unique benzyltetrahydroisoquinoline alkaloid imbricatine (
1) isolated from the starfish
Dermasterias ...imbricata, has been accomplished. As a result of the synthesis, the correctness of the structure and absolute stereochemistry proposed for imbricatine has been unequivocally confirmed.
A chiral synthesis of tri-
O-methylimbricatine (
2), the tri-
O-methyl derivative of the benzyl-tetrahydroisoquinoline alkaloid imbricatine (
1), is described.
In recent years it has become increasingly clear that chemical interactions play a fundamental role in aquatic habitats and have far-reaching evolutionary and ecological consequences. A plethora of ...studies have shown that aquatic organisms from most taxa and functional groups respond to minute concentrations of chemical substances released by other organisms. However, our knowledge of this ‘chemical network’ is still negligible. Chemical interactions can be divided into two larger sub-areas based on the function of the chemical substance. First, there are interactions where chemical substances are toxic to other organisms and are used as a defence against consumers (including both herbivores and predators) or a weapon against competitors (allelopathy). Second, chemical substances may be used as a source for information on the environment; for example: how can I find the optimal habitat, the best food, the nicest partner, and avoid being eaten? Aquatic organisms are able to detect and respond to extremely low concentrations of chemical cues to answer all these questions. The book aims at connecting these intriguing chemical interactions with traditional knowledge of organism interactions. It covers a wide range of studies, both plant and animal, from different geographic regions and habitats — pelagic as well as benthic. Most of the chemical interactions are similar in freshwater and marine habitats and this book therefore strives at integrating work on both systems.
