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More than meets the eye: functionally salient changes in internal bone architecture accompany divergence in cichlid feeding mode.

Albertson RC, Cooper WJ, Mann KA - Int J Evol Biol (2012)

Bottom Line: We focus on the maxilla, which is an integral part of the feeding apparatus and an element that should be subjected to significant bending forces during biting.This was supported by the results of a genetic mapping experiment, where suction feeding alleles were dominant to biting alleles at two loci that affect bone architecture.Overall, these data suggest that the internal structure of the cichlid maxilla has a tractable genetic basis and that discrete shifts in this trait have accompanied the evolution of alternate feeding modes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Massachusetts Amherst, 611 North Pleasant Street, Amherst, MA 01003, USA.

ABSTRACT
African cichlids have undergone extensive and repeated adaptive radiations in foraging habitat. While the external morphology of the cichlid craniofacial skeleton has been studied extensively, biomechanically relevant changes to internal bone architecture have been largely overlooked. Here we explore two fundamental questions: (1) Do changes in the internal architecture of bone accompany shifts in foraging mode? (2) What is the genetic basis for this trait? We focus on the maxilla, which is an integral part of the feeding apparatus and an element that should be subjected to significant bending forces during biting. Analyses of μCT scans revealed clear differences between the maxilla of two species that employ alternative foraging strategies (i.e., biting versus suction feeding). Hybrids between the two species exhibit maxillary geometries that closely resemble those of the suction feeding species, consistent with a dominant mode of inheritance. This was supported by the results of a genetic mapping experiment, where suction feeding alleles were dominant to biting alleles at two loci that affect bone architecture. Overall, these data suggest that the internal structure of the cichlid maxilla has a tractable genetic basis and that discrete shifts in this trait have accompanied the evolution of alternate feeding modes.

No MeSH data available.


Related in: MedlinePlus

(a) LF and MZ exhibit clear differences in internal bone architecture. Both frontal and transverse sections are shown. Frontal sections were taken approximately halfway through the bone. Lines through the elements show the level at which transverse sections were taken. Differences in bone architecture were quantified as bone bending stiffness (i.e., Imax⁡ mm4, (b)) and bone cross-sectional area (mm2, (c)). For both measures, the F1 and F2 hybrid generations are intermediate, with a statistical bias toward MZ values. For both (b) and (c), the “a, b, and c” indicate statistical groupings according to a two-tail t-test, and bars indicate standard errors. (d) Linear regression of bone area on bending stiffness. The relationship between bone bending stiffness and area is approximately the same for MZ and both hybrid generations, but different for LF, which are more efficient in terms of generating greater bending stiffness via the distribution of bone.
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fig2: (a) LF and MZ exhibit clear differences in internal bone architecture. Both frontal and transverse sections are shown. Frontal sections were taken approximately halfway through the bone. Lines through the elements show the level at which transverse sections were taken. Differences in bone architecture were quantified as bone bending stiffness (i.e., Imax⁡ mm4, (b)) and bone cross-sectional area (mm2, (c)). For both measures, the F1 and F2 hybrid generations are intermediate, with a statistical bias toward MZ values. For both (b) and (c), the “a, b, and c” indicate statistical groupings according to a two-tail t-test, and bars indicate standard errors. (d) Linear regression of bone area on bending stiffness. The relationship between bone bending stiffness and area is approximately the same for MZ and both hybrid generations, but different for LF, which are more efficient in terms of generating greater bending stiffness via the distribution of bone.

Mentions: We have shown previously that the forces generated during biting will be transmitted from the lower jaw, through the maxillae, and to the anterior portions of the neurocranium and palatine ([34], Figure 1). Bending force load should also be high in the maxilla, since it acts as a lever that pivots around the pterygoid process of the palatine (Figure 1), and which is moved by the A1 division of the adductor mandibulae muscle during biting and by its connection to the lower jaw during mouth opening [32]. The shape of the maxillae is conspicuously different in LF and MZ (Figures 1 and 2(a)), with LF possessing an element that is much wider and more conspicuously bent along the medial-lateral axis compared to MZ, where the maxilla is thin and straight. See Albertson and Kocher [42] for a more comprehensive discussion of the craniofacial anatomy of these two species and Otten [45] and Cooper et al. [34] for a description of the functional anatomy of the cichlid oral jaws.


More than meets the eye: functionally salient changes in internal bone architecture accompany divergence in cichlid feeding mode.

Albertson RC, Cooper WJ, Mann KA - Int J Evol Biol (2012)

(a) LF and MZ exhibit clear differences in internal bone architecture. Both frontal and transverse sections are shown. Frontal sections were taken approximately halfway through the bone. Lines through the elements show the level at which transverse sections were taken. Differences in bone architecture were quantified as bone bending stiffness (i.e., Imax⁡ mm4, (b)) and bone cross-sectional area (mm2, (c)). For both measures, the F1 and F2 hybrid generations are intermediate, with a statistical bias toward MZ values. For both (b) and (c), the “a, b, and c” indicate statistical groupings according to a two-tail t-test, and bars indicate standard errors. (d) Linear regression of bone area on bending stiffness. The relationship between bone bending stiffness and area is approximately the same for MZ and both hybrid generations, but different for LF, which are more efficient in terms of generating greater bending stiffness via the distribution of bone.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3362014&req=5

fig2: (a) LF and MZ exhibit clear differences in internal bone architecture. Both frontal and transverse sections are shown. Frontal sections were taken approximately halfway through the bone. Lines through the elements show the level at which transverse sections were taken. Differences in bone architecture were quantified as bone bending stiffness (i.e., Imax⁡ mm4, (b)) and bone cross-sectional area (mm2, (c)). For both measures, the F1 and F2 hybrid generations are intermediate, with a statistical bias toward MZ values. For both (b) and (c), the “a, b, and c” indicate statistical groupings according to a two-tail t-test, and bars indicate standard errors. (d) Linear regression of bone area on bending stiffness. The relationship between bone bending stiffness and area is approximately the same for MZ and both hybrid generations, but different for LF, which are more efficient in terms of generating greater bending stiffness via the distribution of bone.
Mentions: We have shown previously that the forces generated during biting will be transmitted from the lower jaw, through the maxillae, and to the anterior portions of the neurocranium and palatine ([34], Figure 1). Bending force load should also be high in the maxilla, since it acts as a lever that pivots around the pterygoid process of the palatine (Figure 1), and which is moved by the A1 division of the adductor mandibulae muscle during biting and by its connection to the lower jaw during mouth opening [32]. The shape of the maxillae is conspicuously different in LF and MZ (Figures 1 and 2(a)), with LF possessing an element that is much wider and more conspicuously bent along the medial-lateral axis compared to MZ, where the maxilla is thin and straight. See Albertson and Kocher [42] for a more comprehensive discussion of the craniofacial anatomy of these two species and Otten [45] and Cooper et al. [34] for a description of the functional anatomy of the cichlid oral jaws.

Bottom Line: We focus on the maxilla, which is an integral part of the feeding apparatus and an element that should be subjected to significant bending forces during biting.This was supported by the results of a genetic mapping experiment, where suction feeding alleles were dominant to biting alleles at two loci that affect bone architecture.Overall, these data suggest that the internal structure of the cichlid maxilla has a tractable genetic basis and that discrete shifts in this trait have accompanied the evolution of alternate feeding modes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Massachusetts Amherst, 611 North Pleasant Street, Amherst, MA 01003, USA.

ABSTRACT
African cichlids have undergone extensive and repeated adaptive radiations in foraging habitat. While the external morphology of the cichlid craniofacial skeleton has been studied extensively, biomechanically relevant changes to internal bone architecture have been largely overlooked. Here we explore two fundamental questions: (1) Do changes in the internal architecture of bone accompany shifts in foraging mode? (2) What is the genetic basis for this trait? We focus on the maxilla, which is an integral part of the feeding apparatus and an element that should be subjected to significant bending forces during biting. Analyses of μCT scans revealed clear differences between the maxilla of two species that employ alternative foraging strategies (i.e., biting versus suction feeding). Hybrids between the two species exhibit maxillary geometries that closely resemble those of the suction feeding species, consistent with a dominant mode of inheritance. This was supported by the results of a genetic mapping experiment, where suction feeding alleles were dominant to biting alleles at two loci that affect bone architecture. Overall, these data suggest that the internal structure of the cichlid maxilla has a tractable genetic basis and that discrete shifts in this trait have accompanied the evolution of alternate feeding modes.

No MeSH data available.


Related in: MedlinePlus