The organization and development of the arthropod ventral nerve cord: insights into arthropod relationships

Abstract

The central nervous system (CNS) of arthropods is a particularly suitable organ in which to search for characters to reconstruct evolutionary relationships between the major arthropod groups. Evolution has clearly wrought changes in nervous systems --- indeed behavioural traits which are a prime target for natural selection are determined by the structure and function of this organ system. Despite this, the mature structure of the CNS and the developmental processes that generate it show a high degree of conservation compared with other, more malleable, features such as external body parts. Secondly, the CNS of arthropods is populated by an array of cells which can be recognized as individuals at a cellular level. Each neuron has a unique set of characters differentiating it from other neurons which can greatly assist the recognition of homologues between species, an essential first step when drawing inferences about evolutionary change.