Comparative morphology and evolutionary pathways of the mouthparts in spore‐feeding Staphylinoidea (Coleoptera)

Abstract

Abstract Betz, O., Thayer, M.K., and Newton, A.F. 2003. Comparative morphology and evolutionary pathways of the mouthparts in spore-feeding Staphylinoidea (Coleoptera). -Acta Zoologica (Stockholm) 84 : This study surveys the external morphology of the mouthparts in the guild of spore-feeders among the coleopterous superfamily Staphylinoidea, evaluating the influence of different phylogenetic and ecological starting points on the formation of their mouthparts. Our emphasis is on a scanning electron microscope analysis (SEM) of the involved trophic structures in spore-feeding larvae and adults of the Ptiliidae, Leiodidae and Staphylinidae, describing the fine structure of their main functional elements. Functionally, mouthpart structures resemble brushes, brooms, combs, rakes, rasps, excavators, knives, thorns, cram-brushes, bristle troughs, blocks and differently structured grinding surfaces. Their different involvement in the various aspects of the feeding process (i.e. food gathering, transporting, channelling and grinding) is deduced from our SEM analyses plus direct video observations. We infer five different patterns of food transport and processing, discriminating adults of ptiliids, leiodids plus staphylinids (excluding some aleocharines), several aleocharine staphylinids, and the larvae of leiodids and staphylinids. The structural diversity of the mouthparts increases in the order from (1) Ptiliidae, (2) Leiodidae towards (3) Staphylinidae, reflecting the increasing systematic and ecological diversity of these groups. Comparisons with non-spore-feeders show that among major lineages of staphylinoids, shifts from general microphagy to sporophagy are not necessarily constrained by, nor strongly reflected in, mouthpart morphology. Nevertheless, in several of these lineages the organs of food intake and grinding have experienced particular fine-structural modifications, which have undergone convergent evolution, probably in response to specialized mycophagy such as spore-feeding. These modifications involve advanced galeal rakes, galeal or lacinial 'spore brushes' with arrays of stout bristles, reinforced obliquely ventrad orientated prosthecal lobes and the differentiations of the molar grinding surfaces into stout teeth or tubercles. In addition, several staphylinids of the tachyporine and oxyteline groups with reduced mandibular molae have evolved secondary trituration surfaces, which in some aleocharines are paralleled by considerable re-constructions of the labium-hypopharynx.

On the head morphology of Lepiceridae (Coleoptera: Myxophaga) and the systematic position of the family and suborder

“…The preferred food and feeding behaviour of Lepicerus is unknown, but is is likely that they largely rely on algae as do other myxophagans and Hydraenidae, which live in similar habitats. As in other groups with weakly developed mandibular apices (Hydraenidae, Ptiliidae; Betz et al, 2003), the strongly sclerotised and toothed lacinia is used to collect food, whereas the mechanical processing takes place between the mandibular molae (see also Beutel et al, 2001). …”

Pollen grains adhere to the moist mouthparts in the flower visiting beetle Cetonia aurata (Scarabaeidae, Coleoptera)

“…Pollen and spore feeding behaviour of Staphylinoidea was studied in detail by Betz et al (2003). Sporophagy is a common feeding preference with particular demands on mouthpart morphology that are functionally similar to those of pollen feeding.…”

“…The mola is often reinforced with grinding structures, and the prostheca shows a microstructural diversification for sweeping particulate food material off the maxillae. The cibarial roof, epi-and hypopharynx show various microtrichia and bristle-troughs, for guiding the food through the cibarium (Betz et al 2003). e Wavy bristles and serrated bristles covered with fluid in Cetonia aurata (Scarabaeidae).…”

“…Insect mouthparts are highly integrated structural units, forming interfaces with the environment (Betz et al 2003). They often possess dense bristles for harvesting small pollen grains, as well as structural modifications for the manipulation of ingested pollen.…”

Using DNA-barcoding to make the necrobiont beetle family Cholevidae accessible for forensic entomology

“…All are small (mostly 2-6 mm in length), ovoid in body shape, brown, grey or black, and as adults distinguishable only by subtle differences in the proportions of antennal articles, pronotal shape, and the genitalia [12]; identification of the larvae is equally cumbersome (Zwick, personal communication). Although they include some groups that are highly derived cave-dwellers (such as the subfamily Leptodirinae) or specialised inhabitants of mammal nests and burrows (e.g., the genus Choleva), the majority of the species are found above-ground on decaying matter, most commonly animal cadavers, where they probably feed predominantly on fungal spores [13,14]. In temperate regions, they are among the dominant insect groups found on animal carcasses, both above-ground [5] and buried [15].…”