Development of mouthparts in the cicada Meimuna mongolica (Distant): successive morphological patterning and sensilla differentiation from nymph to adult.

Yanan Hao,Christopher H Dietrich,Wu Dai

doi:10.1038/srep38151

Abstract

Development of the mouthparts in the cicada Meimuna mongolica (Distant) is investigated here for the first time using scanning electron microscopy in order to document changes occurring in different nymphal instars and from nymph to adult, during which a shift from subterranean root-feeding to feeding on aboveground parts of the host plant occurs. The structure and component of mouthparts is similar to those found in other hemipteran insects. Fourteen types of sensilla and five types of cuticular processes were found on the mouthparts of nymphs and adults. Significant general transformations during development include changes in: (a) the size and shape of the labrum from square to long and shovel-shaped; (b) increases in type and quantity of sensilla with the stage of development; (c) the ridges at the tips of the mandiblar stylets become more prominent in later stages of nymphal development, while odontoid protrusions more prominent in the female than in the male of the adult; and (d) the cross section of the stylets is subcircular in nymphal stages but oblong elliptical in the adult. The implications of these mouthpart transformations on the feeding ability of nymphs and adults and their possible relationship to the feeding niche are discussed.

Highlights

Evolutionary adaptations for the nutritional exploitation of host plants represent a major force driving the diversification of phytophagous insects
Our research has revealed that the labrums of Cicadoidea are nearly rectangular flat structures, while in other Cicadomorpha the labrum is conical and triangular or pyramidal[10,12,37]
Further study of variation in the morphology of the labrum of nymphs may prove useful for classification and identification[38], as well as for ecological or physiological study

Summary

Introduction

Evolutionary adaptations for the nutritional exploitation of host plants represent a major force driving the diversification of phytophagous insects. Several previous studies have examined the mouthpart morphology of adult Hemiptera based on light and scanning electron microscopy[1,2], including as Aphidoidea[3,4,5], Psyllidae[6,7], Aleyrodidae[8,9], Cicadellidae[10,11,12,13] and Fulgoroidea[14,15]. These studies demonstrated that the structures of the mouthparts vary between different species and that some such differences are related to differences in feeding behavior. Nymphs remain little studied[27,30] because they are subterranean and difficult to obtain

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Conclusion