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

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

doi:10.1002/ece3.6309

Philippe Munyandamutsa, Austin Mtethiwa + Show 2 more

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https://doi.org/10.1002/ece3.6309

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Abstract

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: Haplochromis kamiranzovu, H. insidiae, and H. astatodon 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 H. kamiranzovu and H. insidiae at geographical, habitat, and gender levels. No comparison at habitat level was done for H. astatodon because it is found only in littoral zone. The analysis revealed significant tooth shape differences among the three species. Haplochromis astatodon had a significantly longer major cusp height and a longer and larger minor cusp than that of H. insidiae. It had also a longer major cusp height and a longer and larger minor cusp than that of H. kamiranzovu. Tooth shape differences of H. kamiranzovu and H. insidiae species were not significantly different between littoral and pelagic fish (p > .05) while differences were significant between southern and northern Lake Kivu populations (p < .05). Tooth sizes in H. kamiranzovu and H. insidiae were significantly different, both in height and width as well as in their ratios, and this was true at sex and geographic levels (p < .05), but not at habitat level (p > .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.

Highlights

Tooth shape is often used as a taxonomic tool in vertebrates
We examined the hypothesis that tooth size vary among Haplochromis astatodon, H. insidiae and H. kamiranzovu
The purpose of this study was to determine whether there is a diagnostic value of tooth shape in the identification of the Lake Kivu haplochromines

Summary

| INTRODUCTION

Tooth shape is often used as a taxonomic tool in vertebrates. For example, the enamel–dentine junction morphology and enamel thickness in early hominid molars proved to be useful for taxonomic studies (Ayvazyan, Vasilyan, & Böhme, 2019; Delgado et al, 2015) and the cranial dental morphology was used to assess the taxonomic status of the hoolock species in China (Fan et al, 2017). Studying tooth size variation of the haplochromines species offers an opportunity to explore the relationship between crown size and habitat gradient from the littoral versus pelagic zone haplochromines of Lake Kivu. We tested the hypothesis that tooth shape varies among Haplochromis astatodon, H. insidiae and H. kamiranzovu, and is a taxonomically reliable trait among these Lake Kivu cichlids. We examined whether Haplochromis astatodon, H. insidiae, and H. kamiranzovu can be identified using tooth shape, and whether tooth size (i.e., height and width) of major cusps can be another tool to aid in diagnosis of the three species. We tested for tooth shape differences between sexes, habitat, and region in major cusp heights and widths of the three species

| MATERIALS AND METHODS

Findings

| DISCUSSION