Material Properties and Morphology of Prestomal Teeth in Relation to the Feeding Habits of Diptera (Brachycera)

Abstract

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 Scathophaga stercoraria 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.

Mechanical properties, degree of sclerotisation and elemental composition of the gastric mill in the red swamp crayfish Procambarus clarkii (Decapoda, Crustacea)

“…Knowledge about material properties complements morphology and gives rise to a profound understanding of function and also—when feeding structures are studied comparatively—of trophic specialisations. For invertebrate feeding structures, only very few studies comparing multiple taxa in the light of trophic specialisation implement both material properties and morphology [for fly teeth, see 37 ; for butterfly proboscises, see 38 and for radular teeth, see 39 – 43 .…”

Mandible mechanical properties and composition of the larval Glossosoma boltoni (Trichoptera, Insecta)

“…Additionally, alkaline earth metals (Ca, Mg), potentially as part of biomineralization, can be present in small proportions 27 , 38 – 41 . P, Si, Si, Cl, K or Na, can also be detected in such localities 27 , 40 , 74 , 85 – 95 . As especially Zn, Mn, Ca and Mg seem to relate directly to an increase in hardness and thus wear resistance in insects 28 , 29 , 41 , 71 , 73 , 74 , 77 , 78 , 92 , 96 – 98 , such components were found in structures that are prone to structural failure or wear.…”

“…As especially Zn, Mn, Ca and Mg seem to relate directly to an increase in hardness and thus wear resistance in insects 28 , 29 , 41 , 71 , 73 , 74 , 77 , 78 , 92 , 96 – 98 , such components were found in structures that are prone to structural failure or wear. Examples for this are claws 74 , ovipositors 40 , 94 , 99 and mouthparts 28 , 29 , 71 , 73 , 82 , 95 , 100 – 106 . In Glossosoma boltoni , we did not detect high proportions of transition and earth alkaline metals (see Figs.…”

Qualitative Analyses of Textile Damage (Cuts and Tears) Applied to Fabrics Exposed to the Decomposition of Carcasses and Associated Insect Activity in an Austral Summer

“…In carrion blow flies such as C. vomitoria and L. sericata, the prestomal teeth have a width of approximately 15 µm and are highly sclerotized, with various degrees of serration. In addition to this, the scraping action of the labellum has been reported to be able to cut through 50 µm of tissue [58][59][60]. The combined action of the prestomal teeth and labellar hooks on bloodstained fabrics may result in the fracture and displacement of yarns and the overall distorted appearance of the fabric structure.…”