Patterns of Arrangement and Connectivity in the Central Nervous System of Arachnids

Abstract

In arthropods the organization of the central nervous system is related to the body segmentation and to the degree of development of segmental appendages and sense organs. In arachnids the body is divided into a prosoma and opisthosoma. Arachnids do not have antennae or appendages on the opisthosoma apart from spinnerets and the appendages they have are concentrated on the prosoma. In addition, arachnids have developed special sensory structures like pectines, malleoli, flagella, modified sensory legs, slits and other sense organs. These and other characteristic features are reflected by the structure of the arachnid central nervous system (CNS). This chapter gives a comparative account of the external morphology and internal anatomy of the CNS of five wellknown arachnid orders (scorpions, whip scorpions, tailless whip scorpions, wind scorpions and spiders). What we know of the major features of the arachnid CNS is mostly due to the work of a few authors (Saint-Remy 1890, Borner 1904; Gottlieb 1926; Hanstrom 1928; Kaestner 1932, 1933, 1940; Millot 1949; Babu 1965, Babu and Barth 1984). A brief review of its less-known functions is included.