キブ湖のシクリッド類における同種ハプロクロミン3種の歯形の種特異性と性的二型性

Species specificity and sexual dimorphism in tooth shape among the three sympatric haplochromine species in Lake Kivu cichlids.

• Philippe Munyandamutsa
• Wilson Lazaro Jere
• Daud Kassam
• Austin Mtethiwa

抄録

歯形は魚類を含む脊椎動物の形態学的に類似した種を区別するために用いられる。本研究では，同種の3種の歯形を定量することを目的とした。本研究では，キブ湖固有種である同種3種の歯形を定量的に解析することを目的とした．歯の形状を定量的に分析するために，デジタル化された歯の輪郭データをもとに楕円フーリエ解析を行い，3種間の違いを検定した．歯冠の形状と大きさの違いについては，地理的，生息地的，性別レベルでの違いを調べた。沿岸域にしか生息していないため，生息地レベルでの比較は行っていない。また，本種の歯形の違いは，沿岸域と遠洋域では有意な差は見られなかった（>.05）が，キブ湖南部個体群と北部個体群では有意な差が見られた（<.05）。歯の大きさは，高さと幅，比率の両方で有意に異なっており，性別と地理的レベル（<.05）では有意であったが，生息地レベル（>.05）では有意ではなかった。また、歯の形状も、南部個体群のオスと北部個体群のメスでは、オスの歯が鋭く、メスの歯は北部個体群と比べて有意に異なっていた。これらの形状や大きさの違いは、湖沼の生息地で利用可能な食料資源に対する採食戦略の違いを示唆している。さらなる研究により、観察されたパターンの遺伝的根拠が説明されるべきである。

Tooth shape is used to differentiate between morphologically similar species of vertebrates, including fish. This study aimed to quantify tooth shape of three sympatric species: , , and endemic to Lake Kivu, whose existing identification criteria are currently only qualitative. A quantitative tooth shape analysis was performed based on digitized tooth outline data with a subsequent elliptic Fourier analysis to test for differences among the three species. We looked at crown shape and size differences within and at geographical, habitat, and gender levels. No comparison at habitat level was done for because it is found only in littoral zone. The analysis revealed significant tooth shape differences among the three species. had a significantly longer major cusp height and a longer and larger minor cusp than that of It had also a longer major cusp height and a longer and larger minor cusp than that of . Tooth shape differences of and species were not significantly different between littoral and pelagic fish ( > .05) while differences were significant between southern and northern Lake Kivu populations ( < .05). Tooth sizes in and were significantly different, both in height and width as well as in their ratios, and this was true at sex and geographic levels ( < .05), but not at habitat level ( > .05). Tooth shape was also significantly different with sharp teeth for males compared with females of southern populations versus northern ones. These shape- and size-related differences between sexes suggest differences in the foraging strategies toward available food resources in the lake habitat. Further research should explain the genetic basis of the observed pattern.

© 2020 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.