Microscopic morphology and distribution of the antennal sensilla in the
double spine bark beetle, Ips duplicatus
Abstract
ABSTRACT The double-spined spruce bark beetle, Ips
duplicatus has become an infamous secondary pest of Norway spruce,
causing extensive ecological and economic destruction in many Central
European countries. Antennae are the primary olfactory organs that play
fundamental role in insect-host chemical communication; therefore,
understanding morphology is crucial before conducting
electrophysiological investigations. Here, we present our analysis of
sensilla types on the antennal surface of I. duplicatus for the
first time, using high-resolution-scanning electron microscopy. We
studied the external morphological characteristics of antennae and the
types, numbers, and distribution of the antennal sensilla in males and
females. Our results revealed the presence of five different types of
morphologically distinct sensilla: sensilla chaetica, sensilla
basiconica, sensilla trichodea, sensilla coeloconica, and Bӧhm’s
bristles. We observed two subtypes in sensilla chaetica (SChI and
SChII), four subtypes in sensilla basiconica (SBI, SBII, SBIII and
SBIV), three subtypes in sensilla trichodea (STrII, STrIII and STrIV)
and two subtypes in sensilla coeloconica (SCoI and SCoII), respectively
in I. duplicatus males and females. Minor differences in length
and numbers between the sexes for some sensilla types were found.
Distribution maps for different sensillar types were constructed and
specific areas for the respective sensilla were found. Possible
functions of observed sensilla types are discussed. The present study
provides a basis for future electrophysiological studies aimed at
understanding how I. duplicatus detects ecologically important
olfactory cues.