Lehnert Matthew S, Tarver Lauren A, Feng Jiansheng
Department of Biological Sciences, Kent State University at Stark, North Canton, OH 44720, USA.
School of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325, USA.
Insects. 2022 Feb 17;13(2):207. doi: 10.3390/insects13020207.
Prestomal teeth are cuticular projections on the mouthparts of some fly species that rasp surfaces when feeding. Although prestomal teeth morphology has been reported for several fly species, their material properties have not been investigated. Here we report the morphology, elemental composition, extent of sclerotization, hardness, and elastic modulus of prestomal teeth and relate these findings to feeding habits. Scanning electron microscopy revealed that species categorized as flower visitors have a large labellum with numerous pseudotracheae and lack prestomal teeth, generalist species have these same features but with prestomal teeth, and specialist species that feed on blood or other insects have a smaller labellum with few or no pseudotracheae and relatively large prestomal teeth. Confocal microscopy revealed that prestomal teeth are heavily sclerotized and the labellum contains resilin, an elastomeric protein. Hardness and elastic modulus were explored with nanoindentation and showed that the insectivorous had the hardest prestomal teeth and the highest modulus. Energy dispersive x-ray spectroscopy revealed that prestomal teeth had low concentrations of inorganic elements, suggesting that hardness might be partially supplemented by inorganic elements. Our findings indicate that prestomal teeth morphology and material properties relate more to feeding habits than to phylogeny.
口前齿是一些蝇类口器上的表皮突起，在取食时会刮擦表面。尽管已经报道了几种蝇类的口前齿形态，但它们的材料特性尚未得到研究。在此，我们报告口前齿的形态、元素组成、硬化程度、硬度和弹性模量，并将这些发现与取食习性联系起来。扫描电子显微镜显示，被归类为访花者的物种有一个带有许多假气管的大唇瓣且没有口前齿，多食性物种有这些相同特征但有口前齿，而以血液或其他昆虫为食的专食性物种有一个较小的唇瓣，几乎没有或没有假气管且口前齿相对较大。共聚焦显微镜显示口前齿高度硬化，且唇瓣含有弹性蛋白 resilin。通过纳米压痕法探究了硬度和弹性模量，结果表明食虫性物种的口前齿最硬且模量最高。能量色散X射线光谱显示口前齿中无机元素浓度较低，这表明硬度可能部分由无机元素补充。我们的研究结果表明，口前齿的形态和材料特性与取食习性的关系比与系统发育的关系更大。
