Going underwater: multiple origins and functional morphology of piercing-sucking feeding and tracheal system adaptations in water scavenger beetle larvae (Coleoptera: Hydrophiloidea)

Abstract

Larvae of water scavenger beetles (Coleoptera: Hydrophiloidea) are adapted to a wide variety of aquatic habitats, but little is known about functional and evolutionary aspects of these adaptations. We review the functional morphology and evolution of feeding strategies of larvae of the families Hydrophilidae and Epimetopidae based on a detailed scanning electron microscope (SEM) analysis, analysis of video records of feeding behaviour and observations of living larvae. There are two main types of feeding mechanisms: chewing and piercing-sucking. The character mapping using the latest phylogenetic hypothesis for Hydrophiloidea infers the chewing system as the ancestral condition. The piercing-sucking mechanism evolved at least four times independently: once in Epimetopidae (Epimetopus) and three times in Hydrophilidae (Berosini: Berosus + Hemiosus; Laccobiini: Laccobius group; Hydrobiusini: Hybogralius). The piercing-sucking apparatus allows underwater extra-oral digestion and decreases the dependence of larvae on an aerial environment. A detailed study of the tracheal morphology of the piercing-sucking lineages reveals four independent origins of the apneustic respiratory system, all of them nested within lineages with piercing-sucking mouthparts. We conclude that piercing-sucking mouthparts represent a key innovation, which allows for the subsequent adaptation of the tracheal system, influences the diversification dynamics of the lineages and allows the shift to new adaptive zones.

Laboratory rearing of Hydrochus japonicus (Coleoptera: Hydrochidae) suggests larvae live at the water bottom

“…2018; Rodriguez et al . 2020). These ‘specialized’ larvae are presumed to have evolved for a benthic way of life independently within the family Hydrophilidae (Rodriguez et al .…”

“…These ‘specialized’ larvae are presumed to have evolved for a benthic way of life independently within the family Hydrophilidae (Rodriguez et al . 2020). The Hydrochidae larvae, as described by Richmond (1920) and Archangelsky (1997), have large, open respiratory organs in the abdomen, suggesting that they breathe on the surface of the water; however, in reality, they remain in the water and do not come to the surface.…”

The complete aquatic life: Adaptation of Amphiops mater Sharp (Coleoptera: Hydrophilidae) to the water surface during the pupal stage

“…In recent years, the evolution of adult and larval morphology in Hydrophilidae has been studied (Short & Fikáček 2013; Rodriguez et al . 2020), but the pupae have not been thoroughly investigated.…”

“…Pupae of this species are thought to have evolved to breathe in water, and detailed observations of their morphology and respiratory organs will contribute to the study of the evolution of the Hydrophilidae. In recent years, the evolution of adult and larval morphology in Hydrophilidae has been studied (Short & Fik ac ˇek 2013;Rodriguez et al 2020), but the pupae have not been thoroughly investigated.…”

Pinching or stinging? Comparing prey capture among scorpions with contrasting morphologies

“…For example, some studies have shown that mammal and fish feeding ecology has a stronger evolutionary influence on functional morphology [2,3]. There are a small but increasing number of functional studies exploring the relationship between morphology and feeding ecology in invertebrates, mainly in arachnids and insects [4][5][6][7][8]. A few studies have shown that some parameters,including shape and force, play a key role in prey capture in some predators.…”