Mouth asymmetry in the textbook example of scale-eating cichlid fish is not a discrete dimorphism after all

Kusche, Henrik; Lee, Hyuk Je; Meyer, Axel

Mouth asymmetry in the textbook example of scale-eating cichlid fish is not a discrete dimorphism after all

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Datum

2012

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Zeitschriftenartikel

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Proceedings of the Royal Society B: Biological Sciences. 2012, 279(1748), pp. 4715-4723. ISSN 0962-8452. eISSN 1471-2954. Available under: doi: 10.1098/rspb.2012.2082

Zusammenfassung

Individuals of the scale-eating cichlid fish, Perissodus microlepis, from Lake Tanganyika tend to have remarkably asymmetric heads that are either left-bending or right-bending. The ‘left’ morph opens its mouth markedly towards the left and preferentially feeds on the scales from the right-hand side of its victim fish, and the ‘right’ morph bites scales from the victims’ left-hand side. This striking dimorphism made these fish a textbook example of their astonishing degree of ecological specialization and as one of the few known incidences of negative frequency-dependent selection acting on an asymmetric morphological trait, where left and right forms are equally frequent within a species. We investigated the degree and the shape of the frequency distribution of head asymmetry in P. microlepis to test whether the variation conforms to a discrete dimorphism, as generally assumed. In both adult and juvenile fish, mouth asymmetry appeared to be continuously and unimodally distributed with no clear evidence for a discrete dimorphism. Mixture analyses did not reveal evidence of a discrete or even strong dimorphism. These results raise doubts about previous claims, as reported in textbooks, that head variation in P. microlepis represents a discrete dimorphism of left- and right-bending forms. Based on extensive field sampling that excluded ambiguous (i.e. symmetric or weakly asymmetric) individual adults, we found that left and right morphs occur in equal abundance in five populations. Moreover, mate pairing for 51 wild-caught pairs was random with regard to head laterality, calling into question reports that this laterality is maintained through disassortative mating.

Fachgebiet (DDC)

570 Biowissenschaften, Biologie

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ISO 690

KUSCHE, Henrik, Hyuk Je LEE, Axel MEYER, 2012. Mouth asymmetry in the textbook example of scale-eating cichlid fish is not a discrete dimorphism after all. In: Proceedings of the Royal Society B: Biological Sciences. 2012, 279(1748), pp. 4715-4723. ISSN 0962-8452. eISSN 1471-2954. Available under: doi: 10.1098/rspb.2012.2082

BibTex

@article{Kusche2012-12-07Mouth-20881,
  year={2012},
  doi={10.1098/rspb.2012.2082},
  title={Mouth asymmetry in the textbook example of scale-eating cichlid fish is not a discrete dimorphism after all},
  number={1748},
  volume={279},
  issn={0962-8452},
  journal={Proceedings of the Royal Society B: Biological Sciences},
  pages={4715--4723},
  author={Kusche, Henrik and Lee, Hyuk Je and Meyer, Axel}
}

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