Energetics of food selection by the herbivorous parrotfish Sparisoma radians: roles of assimilation efficiency, gut evacuation rate, and algal secondary metabolites

Targett, Timothy E.; Targett, NM

doi:10.3354/meps066013

Cited by 62 publications

(49 citation statements)

References 37 publications

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“…4), a rate less than 25% that of the bucktooth parrotfish. However, the reduced time for complete gut clearance by the emerald parrotfish, compared to that of the bucktooth reported by Targett & Targett (1990), 9.35 h vs. 22.4 h, suggests that the total impact of the 2 species is more similar than the difference in consumption rates suggests. For example, since both species are likely visual, diurnal feeders, as are all the better known species of Caribbean parrotfish (Wilson et al 2003), we can assume for comparison purposes that both species feed an average of 12 h d −1…”

Section: Discussionmentioning

confidence: 68%

“…For comparison, Targett & Targett (1990) calculated the average feeding rate of starved Sparisoma radians to be 0.383 g DW over 4 h, while we estimated average turtlegrass consumption rate of starved Nicholsina usta to be approximately 0.095 g DW over 4 h (Fig. 4), a rate less than 25% that of the bucktooth parrotfish.…”

Section: Discussionmentioning

confidence: 99%

“…Weights were then converted into percentages of food remaining in the alimentary tract of each individual. Alimentary tract evacuation rates were calculated for each fish following the regression equation developed by Targett & Targett (1990):…”

Section: Evacuation Rate Estimatesmentioning

confidence: 99%

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Seagrass consumption by native and a tropically associated fish species: potential impacts of the tropicalization of the northern Gulf of Mexico

Heck¹,

Fodrie²,

Madsen³

et al. 2015

Mar. Ecol. Prog. Ser.

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Temperatures are rising in most temperate and polar environments, and a welldocumented effect of this change is a poleward range shift by a wide variety of terrestrial and aquatic species. In the northern Gulf of Mexico (GOM), an increasing number of tropical species have recently become established among the extant warm-temperate fauna. These include a diversity of tropical fishes, manatees, green turtles, warm-water corals, and black mangroves. The impact of these species may be profound, primarily because temperate species are restricted from shifting northward by the North American land mass. Thus, as tropical species expand northward in the GOM, they must interact with the extant species and potentially compete for essential resources or become prey for each other. Here we focus on tropical immigrants capable of transforming the vast and highly productive seagrass systems of the northern GOM, emphasizing herbivorous parrotfishes and comparing their impact with endemic seagrass-resident fishes. Increased numbers of these herbivores (plus green turtles and manatees) would likely shift detritus-based food webs in seagrass meadows to webs dominated by direct consumption of seagrasses. We provide estimates of some expected consumption rates and effects of these tropically associated seagrass herbivores and predict that the consequences of the increased tropicalization of northern GOM seagrass meadows will be: substantially reduced standing crops and structural complexity of seagrass meadows; increased energy flux through grazing food webs; and a greatly reduced nursery role that will result in much smaller adult populations of those finfish and shellfish species that rely on seagrasses as nurseries.

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Section: Discussionmentioning

confidence: 68%

Section: Discussionmentioning

confidence: 99%

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Seagrass consumption by native and a tropically associated fish species: potential impacts of the tropicalization of the northern Gulf of Mexico

Heck¹,

Fodrie²,

Madsen³

et al. 2015

Mar. Ecol. Prog. Ser.

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“…The ecological relevance of this assay can be questioned because although this concentration can occur in some tropical species of the Dictyotales, it is extremely unlikely that any fish would consume nothing but one of these species for an extended period. A different approach was taken by Targett and Targett (1990) who assayed the effect of crude extracts from a deterrent green seaweed by coating this on a palatable seagrass and evaluating its effects on parrotfish assimilation efficiency. Although the extract had no effect on assimilation efficiency, this does not exclude the possibility of negative effects on growth, development, or fecundity.…”

Section: Physiological Effects Of Defensive Compounds On Natural Enemiesmentioning

confidence: 99%

Marine chemical ecology: what's known and what's next?

Hay

1996

Journal of Experimental Marine Biology and Ecology

553

375

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In this review, I summarize recent developments in marine chemical ecology and suggest additional studies that should be especially productive. Direct tests in both the field and laboratory show that secondary metabohtes commonly function as defenses against consumers. However, some metabolites also diminish fouling, inhibit competitors or microbial pathogens, and serve as gamete attractants; these alternative functions are less thoroughly investigated. We know little about how consumers perceive secondary metabolites or how ecologically realistic doses of defensive metabolites affect consumer physiology or fitness, as opposed to feeding behavior. Secondary metabolites have direct consequences, but they do not act in isolation from other prey characteristics or from the physical and biological environment in which organisms interact with their natural enemies. This mandates that marine chemical ecology be better integrated into a broader and more complex framework that includes aspects of physiological, population, community, and even ecosystem ecology. Recent advances in this area involve assessing how chemically mediated interactions are affected by physical factors such as flow, desiccation, UV radiation, and nutrient availability, or by biological forces such as the palatability or defenses of neighbors, fouling organisms, or microbial symbionts. Chemical defenses can vary dramatically among geographic regions, habitats, individuals within a local habitat, and within different portions of the same individual. Factors affecting this variance are poorly known, but include physical stresses and induction due to previous attack. Studies are needed to assess which consumers induce prey defenses, how responses vary in environments with differing physical characteristics, and whether the 'induced' responses are a direct response to consumer attack or are a defense against microbial pathogens invading via feeding wounds. Although relatively unstudied, ontogenetic shifts in concentrations and types of defenses occur in marine species, and patterns of larval chemical defenses appear to provide insights into the evolution of complex life cycles and of differing modes of development among marine invertebrates. The chemical ecology of marine microbes is vastly underappreciated even though microbes produce metabohtes that can have devastating indirect effects on non-target organisms (e.g., red tide related fish kills) and significantly affect entire ecosystems. The natural functions of these metabolites are poorly understood, but they appear to deter both consumers and other microbes. Additionally, marine macro-organisms use metabolites from microbial symbionts to deter consumers, subdue prey, and defend their embryos from pathogens. Microbial chemical ecology offers unlimited possibilities for investigators that develop rigorous and more ecologically relevant approaches.

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“…Klumpp & Nichols 1983) and might influence preference and/or ingestion rates by consumers. Other factors such as caloric content, amount of organic matter, total protein and total lipid content may also be detected by grazers and result in enhanced consumption rates of higher quality plants (Montgomery & Gerking 1980, Targett & Targett 1990. Additionally, an array of marine plants is chemically defended and avoided by consumers (reviewed by Hay & Fenical 1988), thus providing indirect evidence that herbivores also detect chemical metabolites, presumably through olfaction and gustation.…”

Section: Introductionmentioning

confidence: 99%

Seagrass selection by omnivorous and herbivorous consumers: determining factors

Prado¹,

Heck²

2011

Mar. Ecol. Prog. Ser.

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Consumers of seagrasses are increasingly recognized for their ability to shape landscape features and regulate energy flux in coastal ecosystems. To date, however, the nutritional characteristics and morphological features by which herbivores and omnivores make feeding decisions are poorly understood. To elucidate how consumers of marine vascular plants discriminate among different food resources, we conducted food-preference assays with seagrass leaves and seagrassincorporated agar diets of the 3 most common seagrass species of the Gulf of Mexico (Thalassia testudinum, Halodule wrightii and Syringodium filiforme). These 3 species were offered simultaneously to the most abundant local consumers: the omnivorous pinfish Lagodon rhomboides and filefish Stephanolepis hispidus, the herbivorous emerald parrotfish Nicholstina usta, and the herbivorous sea urchin Lytechinus variegatus. Consumption rates (g fresh weight [FW]) of leaves or seagrass-incorporated agar diets were estimated over 24 h periods. Measured plant properties included C:N, N:P, total carbohydrates, protein and lipid concentrations, caloric content, percentage of organic matter, water and ash. Results showed that S. filiforme was preferred by all fish species (81, 60.2 and 59% of total leaf consumption of pinfish, filefish and parrotfish, respectively), whereas sea urchins consumed the highest amounts of H. wrightii (71.2% of total). However, when leaf structure was removed, by incorporating ground leaf tissue into agar matrices, pinfish and filefish did not show any significant dietary preference. In contrast, parrotfish and sea urchins maintained their preferences for S. filiforme and H. wrightii, respectively. Parrotfish preference for S. filiforme coincided with highest lipid and carbohydrate contents, whereas the preference of sea urchins for H. wrightii could be explained by higher levels of the percentage of organic matter and caloric content. Our results suggest that structural plant features (e.g. leaf manipulability and/or visual recognition of resources) are the most important factors driving discrimination between seagrass species by omnivorous fish, whereas strict herbivores make feeding decisions that are highly influenced by nutritional characteristics, presumably as recognized by both olfaction and gustation.

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Energetics of food selection by the herbivorous parrotfish Sparisoma radians: roles of assimilation efficiency, gut evacuation rate, and algal secondary metabolites

Cited by 62 publications

References 37 publications

Seagrass consumption by native and a tropically associated fish species: potential impacts of the tropicalization of the northern Gulf of Mexico

Seagrass consumption by native and a tropically associated fish species: potential impacts of the tropicalization of the northern Gulf of Mexico

Marine chemical ecology: what's known and what's next?

Seagrass selection by omnivorous and herbivorous consumers: determining factors

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