Morphology and Distribution of Antennal Sensilla in Three Species of Thripidae (Thysanoptera) Infesting Alfalfa Medicago sativa.

Yan-Qi Liu,Jin Li,Li-Ping Ban

doi:10.3390/insects12010081

Abstract

Thrips are important pests to alfalfa Medicago sativa. Similar as many other plant-feeding insects, thrips rely on the antennae to receive chemical signals in the environment to locate their hosts. Previous studies indicated that sensilla of different shapes on the surface of insect antenna play an important role in signal recognition. However, morphological analysis of the antennal sensilla in Thysanoptera has been limited to only a few species. To expand the understanding of how antennal sensilla are related to semiochemical detection in thrips, here we compared the morphology and distribution of antennal sensilla in three thrip species, Odontothrips loti, Megalurothrips distalis, and Sericothrips kaszabi, by scanning electron microscope (SEM). The antennae of these three species are all composed of eight segments and share similar types of sensilla which distribute similarly in each segment, despite that their numbers show sexual dimorphism. Specifically, nine major types of sensilla in total were found, including three types of sensilla basiconica (SBI, SBII, and SBIII), two types of sensilla chaetica (SChI and SChII), and one type for each of sensilla coeloconica (SCo), sensilla trichodea (ST), sensilla campaniformia (SCa), and sensilla cavity (SCav). The potential functions of sensilla were discussed according to the previous research results and will lay a morphological foundation for the study of the olfactory mechanism of three species of thrips.

Highlights

Alfalfa Medicago sativa is one of the most important forages worldwide cultivated, and thrips are one of the most destructive pests to alfalfa [1,2]
Western flower thrips, F. occidentalis can be attracted by stereoisomers, a type of volatiles released by their host plants [12], and they can react quickly when perceiving alarm pheromones released by other second-instar nymphs [13]
This study provided the complete antennal morphology of the three thrip species parasitic on alfalfa (O. loti, M. distalis, and S. kaszabi), with emphasis on the types, number, and location of sensilla

Summary

Introduction

Alfalfa Medicago sativa is one of the most important forages worldwide cultivated, and thrips are one of the most destructive pests to alfalfa [1,2]. More than 10 thrip species, including Odontothrips loti, Odontothrips confusus, Frankliniella occidentalis, Frankliniella intonsa, Thrips tabaci, Megalurothrips distalis, and Sericothrips kaszabi, have been documented as pests of legumes [1,3,4], and O. loti was the predominant one found in the legume-growing areas in China [5] Thrips at their adult and nymph stages can damage the young tissues of alfalfa, including leaves and flower organs, resulting in leaf curling and withering. Western flower thrips, F. occidentalis can be attracted by stereoisomers, a type of volatiles released by their host plants [12], and they can react quickly when perceiving alarm pheromones released by other second-instar nymphs [13]. Another example is that male Poinsettia thrips, Echinothrips americanus, can avoid mating with mated females by identifying the pheromone dimethyl adipate (DBE-6) produced by males during mating [14]

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Results

Discussion

Conclusion