Scanning Electron Microscope Study of Antennae and Mouthparts in the Pollen-Beetle Meligethes (Odonthogethes) chinensis (Coleoptera: Nitidulidae: Meligethinae).

Qihang Li,Paolo Audisio,Andrea Di Giulio,Simone Sabatelli,Meike Liu,Longyan Chen,Wenkai Wang

doi:10.3390/insects12070659

Qihang Li, Paolo Audisio + Show 5 more

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https://doi.org/10.3390/insects12070659

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Abstract

Simple SummaryThe present paper is aimed to further explore the structure of the antennae and mouthparts of specialized beetle species living on flowers, as well as the functions of their associated sensilla. In this study, we used scanning electron microscopy (SEM) to observe and describe for the first time the fine morphology of sensilla on the antennae and mouthparts of the pollen-beetle Meligethes (Odonthogethes) chinensis, a common Chinese species associated with flowers of Rosaceae. The results show that there are six types and twelve subtypes of sensilla on male antennae; seven types and fourteen subtypes on female antennae; seven types and seventeen subtypes on male mouthparts; seven types and sixteen subtypes on female mouthparts. The sensilla on the antennae and mouthparts of Meligethinae that feed on pollen were finally compared with similar sensilla known to occur in other insects, in order to obtain more insights on the evolution of these sensorial structures in specialized flower-inhabiting insects.Meligethes (Odonthogethes) chinensis is a common Chinese phytophagous species in the family Nitidulidae. Its main larval host plant is Rubus idaeus L. (Rosaceae), and adults feed on pollen and other floral parts. In this study, we used scanning electron microscopy (SEM) to observe and study the fine morphology of sensilla on the antennae and mouthparts of M. chinensis. The results show that there are six types and twelve subtypes of sensilla on male antennae; seven types and fourteen subtypes on female antennae; seven types and seventeen subtypes on male mouthparts; seven types and sixteen subtypes on female mouthparts. Sensilla coeloconica (SCo) are found on the female antennae of M. chinensis only, and they are also reported on the antennae of Nitidulidae for the first time. SCo2 on the labrum present sexual dimorphism, and one subtype of sensilla basiconica (SB6) is presented on the tip of maxillary and labial palps of the male only, while other types of sensilla are very similar on the mouthparts of male and female. Finally, by comparing similar sensilla in other insects, we also attempted to discuss the functions of all sensilla on the antennae and mouthparts of M. chinensis.

Highlights

Nitidulidae is a family of the diverse superfamily Cucujoidea, including about 4500 species in the world, with heterogeneous feeding habits, such as phytophagy, saprophagy, and micetophagy [1,2,3,4]
The pollen-beetle M. chinensis was selected to study types, quantities, and distributions of sensilla on the antennae and mouthparts of males and females, respectively, for the first time by scanning electron microscopy (SEM), and to be compared with the sensilla described in the zoosaprophagous O. colon [14]. We present this comparative study on male and female M. chinensis, having the first Nitidulidae lineage with both sexes analyzed in detail and helping to understand the evolution of sensillar equipment, because if the stimuli that guide the male and female activities are different, it is completely predictable that there will be present sex dimorphism in the sensillar equipment [16]
The quantity and types of sensilla on the dorsal view of the antennae are greater than on the ventral view, whereas the quantity of dorsal and ventral sensilla is largest in the three terminal segments of the flagellomeres

Summary

Introduction

Nitidulidae is a family of the diverse superfamily Cucujoidea, including about 4500 species in the world, with heterogeneous feeding habits, such as phytophagy, saprophagy, and micetophagy [1,2,3,4]. Meligethinae is the only subfamily among Nitidulidae strictly anthophagous, with members commonly known as “pollen-beetles”; all members (about 700 species all over the world) of this lineage use pollen and other floral parts as larval and adult food resource [5,6,7,8,9,10,11]. (Rosaceae), and adults mainly feed on the pollen of this plant [7,11]. This species exhibits an apparently marked variation in body size, shape, pubescence, and color, and females are usually longer than males [9]

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