# Report on Leg Sensilla of Notonectidae (Hemiptera, Heteroptera)

## TL;DR

This study identifies ten types of leg sensilla in water bugs, including two new types, and highlights their role in sensing aquatic environments and finding prey.

## Contribution

The first report of arch-shaped and spoon-shaped sensilla in Notonectidae, along with unique subtypes in Anisops.

## Key findings

- Ten types of leg sensilla were identified across seventeen Notonectidae species.
- Sensilla arch-shaped and spoon-shaped were newly reported in Anisops.
- Leg sensilla are crucial for environmental perception and prey detection in aquatic habitats.

## Abstract

The purpose of this study was to analyze the morphological types and arrangement of leg sensilla in Anisops, Enithares and Notonecta, which belong to Notonectidae. In this study, we examined seventeen species from three genera of Notonectidae and found ten types of sensilla on the legs. Sensilla arch-shaped (SAr) and sensilla spoon-shaped (SSp) were reported for the first time.

Notonectidae belongs to the infraorder Nepomorpha within the order Hemiptera. The aim of this study was to analyze the morphological types and arrangement of leg sensilla in Anisops, Enithares and Notonecta. A variety of sensilla are distributed on the legs. These sensilla are responsible for receiving signals from the external environment. Mechanoreceptors exhibit the highest diversity. Using a scanning electron microscope, ten types of sensilla were identified on the legs of seventeen species from Notonectidae. Basic types of mechanoreceptors, including sensilla trichodea (ST1, ST2), sensilla chaetica (SCh1, SCh2), sensilla basiconica (SB2) and sensilla campaniformia (SCa), were distributed across all the studied species. In Anisops, sensilla arch-shaped (SAr) and sensilla spoon-shaped (SSp) were reported for the first time. Additionally, six subtypes of ST were distinguished in Anisops, among which ST3, ST4, ST5 and ST6 are unique. In Enithares and Notonecta, sensilla styloconica (SS) were observed; these sensilla are hypothesized to function as both mechanoreceptors and gustatory receptors. Beyond mechanoreceptors, we also identified thermo-hygroreceptors—sensilla ampullacea (SA) and sensilla coeloconica (SCo)—as well as a potential olfactory sensilla type, namely, sensilla placodea multilobated (SPM). These findings suggest that Notonectidae leg sensilla play an important role in the perception of aquatic environments and prey localization.