Functional significance of intramandibular bending in Poeciliid fishes |
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Authors: | Alice Gibb Lara A Ferry-Graham L Patricia Hernandez Rebecca Romansco Jessica Blanton |
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Institution: | (1) Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011-5640, USA;(2) Moss Landing Marine Laboratories, California State University, 8272 Moss Landing Rd, Moss Landing, CA 95039, USA;(3) Department of Biological Sciences, The George Washington University, Washington, DC 20052, USA |
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Abstract: | Substrate-feeding teleosts show multiple, independent evolutionary acquisitions of intramandibular bending (bending within
the lower jaw)—a behavior that likely enhances performance when feeding on attached or encrusting food items. However, intramandibular
bending has only been quantified for marine teleosts. Here, we examine substrate feeding in eight species from the order Cyprinodontiformes
and quantify movements produced by the anterior jaws of four target species selected from the family Poeciliidae to represent
a variety of trophic strategies. Intramandibular bending, defined here as bending between the dentary and angular–articular
bones of the lower jaw, is not present in some poeciliids (i.e. Gambusia affinis), nor is it present in outgroup cyprinodontiforms (i.e. Fundulus rubrifrons). However, intramandibular bending is present in certain poeciliids (i.e. Poecilia sphenops), and can exceed 90°. Such jaw bending enables the production of a gape angle that approaches 120°, which likely allows the
fish to maximize contact between the toothed tips of the jaws and the substrate during the bite. Intramandibular bending in
poeciliid species is associated with specific trophic shifts: the greater the intramandibular bending in a given species,
the more attached algae (periphyton) reported in its diet. This result supports the hypothesis that intramandibular bending
enhances performance when feeding on encrusting food items. We predict that additional examples of functional convergence
are likely to be documented in freshwater teleosts as more herbivorous species are examined, and we propose that intramandibular
bending represents an excellent model system in which to examine the functional processes that underlie convergent evolution.
An erratum to this article can be found at |
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Keywords: | Convergent evolution Algae scraping Substrate feeding Trophic evolution Herbivory Poeciliidae Cyprinodontiformes Oral jaws Grazing |
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