Palatability of Macroalgae that Use Different Types of Chemical Defenses

Abstract

This study compared algal palatability and chemical defenses from subtropical green algae that may use different types of defense systems that deter feeding by the rockboring sea urchin Echinometra lucunter. The potential defense systems present include (1) the terpenoid caulerpenyne and its activated products from Caulerpa spp., and (2) dimethylsulfoniopropionate (DMSP)-related defenses in Ulva spp. Secondary metabolites from these chemical groups have been shown to deter feeding by various marine herbivores, including tropical and temperate sea urchins. Live algal multiple-choice feeding assays and assays incorporating algal extracts or isolated metabolites into an artificial diet were conducted. Several green algae, including Ulva lactuca, Caulerpa prolifera, and Cladophora sp., were unpalatable. Nonpolar extracts from U. lactuca deterred feeding, whereas nonpolar extracts from C. prolifera had no effect on feeding. Polar extracts from both species stimulated feeding. Caulerpenyne deterred feeding at approximately 4% dry mass; however, dimethyl sulfide and acrylic acid had no effect at natural and elevated concentrations. E. lucunter is more tolerant than other sea urchins to DMSP-related defenses and less tolerant to caulerpenyne than many reef fish. Understanding the chemical defenses of the algae tested in this study is important because they, and related species, frequently are invasive or form blooms, and can significantly modify marine ecosystems.

Carbon self‐utilization may assist Caulerpa taxifolia invasion

“…are generally unpalatable to fish and invertebrates (Erickson et al 2006). Although some fishes and invertebrates assimilate carbon derived from Caulerpa spp.…”

Chemical Defenses: From Compounds to Communities

“…In one of the first studies to examine the chemical defenses of marine algal natural products, McConnell et al (1982) showed that caulerpenyne deterred feeding by the sea urchin Lytechinus variegatus. Erickson et al (2006) demonstrated that the subtropical sea urchin Echinometra lucunter was deterred by relatively high concentrations of caulerpenyne (4% dry mass).…”

Nutrient addition increases consumption rates of tropical algae with different initial palatabilities

“…We collected and cleaned epiphytes from 4 species of macroalgae that have a range of chemical defenses as shown in previous research (Dictyota dichotoma: Ce tru lo & Hay 2000, Wiesemeier et al 2007; Caulerpa sertularioides : Paul & Fenical 1986, Erickson et al 2006Sargassum polyceratium: Boettcher & Targett 1993, Thabard et al 2011Turbinaria turbinata: Meyer et al 1994, Stiger et al 2004, and a nonchemically defended species of algae (Acanthophora spicifera: Fong et al 2006). We weighed 5.0 ± 0.1 g (mean ± SE) samples of each alga after drying in a salad spinner for 1 min, and cable-tied a sample of each alga to each experimental unit, which were rocks collected from each site and covered with wire mesh to facilitate attachment.…”

“…resource availability and herbivory rates) may also cause variation in nutritional quality of coral reef algae, controlling the ability of producers to alter their palatability and reduce their consumption by herbivores (e.g. Erickson et al 2006). It is argued that when resources are low, primary producers that grow slowly and invest more in antiherbivore defense are favored, and that the opposite is also true (i.e.…”