Quarterly Journal of Microscopical Science, Vol s3-104, 337-350, Copyright © 1963 by Company of Biologists

A Histological Study of the Peripheral Receptors in the Thorax of Land Isopods, with Special Reference to the Location of Possible Hygroreceptors

¹ Zoological Laboratory, University of Leiden, Netherlands
² Zoological Laboratory, University of Leiden, Netherlands. Present address, Regional Neurological Centre, Newcastle General Hospital, Newcastle upon Tyne 4, England

By double embedding whole isopods in paraffin wax and celloidin, after fixing them in Bodian's fluid, it was possible to obtain complete sets of undamaged serial sections through the thoracic and abdominal regions of females of Oniscus asellus L. and Porcellio scaber Latr., and also some incomplete series through males of these species and a species of the genus Armadillidium. These sections were stained by the methods of Bodian and of Holmes to show the nerve-fibres. They were then carefully studied, and the distribution and the morphology of all peripheral nerveendings and receptors in the body were determined as completely as possible.

In all, 6 different types of terminations were found; and in some cases it was possible to draw valid inferences about their probable function from a consideration of their location and their morphology alone. Three of them are probably tactile. The function of the other three is much more uncertain; but one of them, a group of pit-like terminations situated on the under side of the lateral plates on each side of the thoracic segments, is particularly suitably located to function as a receptor of temperature or humidity, and morphologically it bears some resemblance to certain proven hygroreceptors in other arthropods. This particular termination and one of the other types, consisting of ventrally situated partially retracted hairs, do not appear to have been described previously in the land isopods.