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Abstract Intensifying climate change and an increasing need for understanding its impacts on ecological communities places new emphasis on testing environmental stress models (ESMs). Using a prior literature search plus references from a more recent search, I evaluated empirical support forESMs, focusing on whether consumer pressure on prey decreased (consumer stress model;CSM) or increased (prey stress model;PSM) with increasing environmental stress. Applying the criterion that testingESMsrequires conducting research at multiple sites along environmental stress gradients, the analysis found thatCSMswere most frequent, with ‘No Effect’ andPSMsoccurring at low but similar frequencies. This result contrasts to a prior survey in which ‘No Effect’ studies were most frequent, thus suggesting that consumers are generally more suppressed by stress than prey. Thus, increased climate change‐induced environmental stress seems likely to reduce, not increase impacts of consumers on prey more often than the reverse
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Killing them softly: Ontogeny of jaw mechanics and stiffness in mollusk‐feeding freshwater stingrays
Abstract Durophagous predators consume hard‐shelled prey such as bivalves, gastropods, and large crustaceans, typically by crushing the mineralized exoskeleton. This is costly from the point of view of the bite forces involved, handling times, and the stresses inflicted on the predator's skeleton. It is not uncommon for durophagous taxa to display an ontogenetic shift from softer to harder prey items, implying that it is relatively difficult for smaller animals to consume shelled prey. Batoid fishes (rays, skates, sawfishes, and guitarfishes) have independently evolved durophagy multiple times, despite the challenges associated with crushing prey harder than their own cartilaginous skeleton.Potamotrygon leopoldiis a durophagous freshwater ray endemic to the Xingu River in Brazil, with a jaw morphology superficially similar to its distant durophagous marine relatives, eagle rays (e.g.,Aetomylaeus, Aetobatus). We used second moment of area as a proxy for the ability to resist bending and analyzed the arrangement of the mineralized skeleton of the jaw ofP. leopoldiover ontogeny using data from computed tomography (CT) scans. The jaws ofP. leopoldido not resist bending nearly as well as other durophagous elasmobranchs, and the jaws are stiffest nearest the joints rather than beneath the dentition. While second moment has similar material distribution over ontogeny, mineralization of the jaws under the teeth increases with age. Neonate rays have low jaw stiffness and poor mineralization, suggesting thatP. leopoldimay not feed on hard‐shelled prey early in life. These differences in the shape, stiffness and mineralization of the jaws ofP. leopoldicompared to its durophagous relatives show there are several solutions to the problem of crushing shelled prey with a compliant skeleton.
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- PAR ID:
- 10461646
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Morphology
- Volume:
- 280
- Issue:
- 6
- ISSN:
- 0362-2525
- Format(s):
- Medium: X Size: p. 796-808
- Size(s):
- p. 796-808
- Sponsoring Org:
- National Science Foundation
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