Little is known of the morphology and physiology of stretch receptors in isopods (Alexandrowicz, 1967; Alexander, 1971). The pill bug (Armadillidium vulgare), a terrestrial isopod, rolls up in a spherical shape in response to a noxious stimulus given to its body or to the removal of its substratum. In this study we show that stretch receptor organs which might detect the displacement of the tergites during this conglobating behaviour are present in the thorax, which forms a large part of the body. We describe the spatial organization of the receptors and their response to stretch stimuli.
Experiments were performed on male and female pill bugs, 12–14 mm in total length. For morphological identification of the stretch receptor organs, conventional vital staining with Methylene Blue and axonal filling with nickel chloride were used. In the latter staining technique, the cut distal stump of the dorsal branch...
