Cockroach Antennae

Abstract

Cockroach antennae have been extensively used for studying the multifunctional sensory appendage that generates the olfactory, gustatory, tactile, thermal, and humidity senses. Of the variety of senses, the tactile sense is thought to play a key role for perceiving physical objects. Because most cockroach species are nocturnal, the tactile sense of the antenna would be essential to determine the position, shape, and texture of surrounding objects in the dark. Mechanoreceptors on the surface of the antenna are primarily responsible for the generation of tactile sense. In addition, the motor function of antenna also contributes to the active tactile sense (Staudacher et al. 2005; Comer and Baba 2011). The antennal movement is accompanied by the activation of proprioceptors at the antennal joints. Cockroach Antenna as a Tactile Sense Organ Cockroaches are insect species that are classified into the order Blattaria. Currently, over 4,000 species have been found in Blattaria, but of these, only a few are known to be pests. Because these species can tolerate the human environment, and are easily reared in laboratories, they are often used for various biological studies. Periplaneta americana, which is also known as the American cockroach, can be considered as the most representative species used for studying the antennal system. Each antenna of adult P. americana is as long as its body length (≈40 mm), and consists of approximately 140 segments (Figures 1 and 2). The first and second proximal segments are called the scape and the pedicel, respectively, and the remaining distal segments are collectively referred to as the flagellum. Each seg-ment is connected to the neighboring segments via flexible joints. However, only the head-scape and scape-pedicel joints can move actively with muscle contraction. The other joints connecting the flagellar segments are deflected only passively.