Nutritional ecology of marine herbivorous fishes: ten years on

Abstract

Summary 1.Marine herbivorous fishes are considered to be of critical importance in determining the biological structure of shallow reef environments, and by implication have key roles in carbon flux in reef ecosystems. Despite this, the nutritional processes that underpin these critical ecological roles have received comparatively little attention. 2.Here we give an overview of recent progress in the nutritional ecology of marine herbivorous fishes, and then examine two recent paradigms that we consider important in the development of the field: (i) the role of temperature in latitudinal gradients of diversity and abundance, and (ii) the impact of these fishes on coral reefs. Our aim is to illustrate how an integrative nutritional ecology approach can enrich insights gained from studies of fish herbivory, and to emphasize the distinctive differences between herbivory in marine and terrestrial systems. 3. We argue that much of the work on trophic biology in marine herbivorous fishes has focused on the ecological impacts of fishes on reefs, the deterrent properties of marine algae, and the morphological and mechanical aspects of ingestion. This has come at the expense of two of the elements necessary for an integrative understanding of feeding ecology, that is, food composition and the physiological processes involved in nutrient extraction and utilization. Together, these factors have hindered the development of the nutritional framework for analysing food resources, feeding patterns and evolutionary trends that has proved successful for terrestrial vertebrate herbivores. 4. The reef grazing and algal secondary metabolite paradigms, while both extremely productive, have failed to develop the clear predictive framework for diet choice required in broader contexts such as reef management and understanding the evolution of herbivory. The lack of a focus on nutritional factors has led to premature conclusions on the influence of temperature on algal digestion, both at the level of digestive processes and the biogeography of marine faunas. 5. Some marine herbivorous fishes appear to be bending the 'rules' of hindgut fermentation, especially with respect to temperature and fermentation substrates, and so the study of nutritional ecology in these animals has potential to generate novel insights for the field of vertebrate nutrition in general.

A Pharm-Ecological Perspective of Terrestrial and Aquatic Plant-Herbivore Interactions

“…In contrast to the broad knowledge base that exists on the mechanisms required to process nutrients as well as mechanisms used by domestic and laboratory species to metabolize drugs, there is a general lack of understanding of how PSMs are processed by herbivores, especially in the context of a variable nutrient environment (Appel, 1993;Casarett et al, 2008;Gross and Bakker, 2012;Karasov and Hume, 1997). The gap in knowledge related to mechanisms required to process nutrients in marine herbivorous fishes, for example, has only recently begun to close (Choat and Clements, 1998;Clements et al, 2009). Moreover, despite a long history of investigating how aquatic animals process chemical contaminants (Chambers and Yarbrough, 1976;Katagi, 2010;Rewitz et al, 2006;Smital et al, 2004), studies investigating how they process dietary secondary metabolites have only recently been initiated (Gross and Bakker, 2012;Liang et al, 2007;Richardson et al, 2009).…”

“…There is increasing evidence that most mammalian herbivores, and many invertebrate herbivores harbor large populations of microbes (bacteria, protozoa and fungi) in their gut that can play a variety of roles including making nutrients more available to the host animal (Broderick et al 2004;Chandler et al, 2008;Clark et al 2010;Clements et al, 2009;Janson et al, 2008;Mountfort et al, 2002;Stevens and Hume, 1998).…”

“…For several decades now, a central focus in the field of nutritional ecology has been to understand the factors that influence the foraging behavior of terrestrial and aquatic herbivores (Choat and Clements, 1998;Clements et al, 2009;Dearing et al, 2005;Foley et al, 1999;Scriber and Slansky, 1981). There is ample evidence from each of these areas that the foraging behavior of herbivores is driven by both nutrients and chemical defenses.…”

“…There is ample evidence from each of these areas that the foraging behavior of herbivores is driven by both nutrients and chemical defenses. Variation in macro-and micronutrients (e.g., protein, carbohydrates, sodium) in foods coupled with the nutritional requirements of herbivores influence intake and food preference (Barboza et al, 2009;Behmer, 2009;Clements et al, 2009;Raubenheimer and Simpson, 1997).…”

“…Although both nutrients and secondary metabolites influence foraging behavior, there is a general lack of ability to a priori predict diet selection even when the nutritional and chemical profiles of available plants are well documented (Clements et al, 2009;Cruz-Rivera and Hay, 2003;Kool, 1992;Sotka et al, 2009;Yeager et al, 1997).…”