Major morphological changes in a Lake Victoria cichlid fish within two decades

Authors

  • FRANS WITTE,

    Corresponding author
    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
      E-mail: f.witte@biology.leidenuniv.nl
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  • MONIQUE WELTEN,

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
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  • MARTIN HEEMSKERK,

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
    2. Dutch Transplant Foundation, Plesmanlaan 100, 2332 CB, Leiden, the Netherlands
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  • IRENE VAN DER STAP,

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
    2. Netherlands Institute of Ecology, Centre for Limnology, Rijksstraatweg 6, 3631 AC Nieuwersluis, the Netherlands
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  • LISANNE HAM,

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
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  • HENDRIKUS RUTJES,

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
    2. Grontmij AquaSense, PO Box 95125, 1090 HC Amsterdam, the Netherlands
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  • JAN WANINK

    1. Institute of Biology Leiden, University of Leiden, PO Box 9516, 2300 RA, Leiden, the Netherlands
    2. Koeman en Bijkerk bv, Ecological Research and Consultancy, PO Box 14, 9750 AA Haren, the Netherlands
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E-mail: f.witte@biology.leidenuniv.nl

Abstract

During the upsurge of the introduced predatory Nile perch in Lake Victoria in the 1980s, the zooplanktivorous Haplochromis (Yssichromis) pyrrhocephalus nearly vanished. The species recovered coincident with the intense fishing of Nile perch in the 1990s, when water clarity and dissolved oxygen levels had decreased dramatically due to increased eutrophication. In response to the hypoxic conditions, total gill surface in resurgent H. pyrrhocephalus increased by 64%. Remarkably, head length, eye length, and head volume decreased in size, whereas cheek depth increased. Reductions in eye size and depth of the rostral part of the musculus sternohyoideus, and reallocation of space between the opercular and suspensorial compartments of the head may have permitted accommodation of larger gills in a smaller head. By contrast, the musculus levator posterior, located dorsal to the gills, increased in depth. This probably reflects an adaptive response to the larger and tougher prey types in the diet of resurgent H. pyrrhocephalus. These striking morphological changes over a time span of only two decades could be the combined result of phenotypic plasticity and genetic change and may have fostered recovery of this species. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 41–52.

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