MAPPING OF SIFAMIDE-LIKE NEUROPEPTIDES IN THE ADULT AND DEVELOPING CENTRAL NERVOUS SYSTEM OF THE AMPHIPOD CRUSTACEAN <EM >PARHYALE HAWAIENSIS</EM>

Comparative neuroanatomical research remains essential for our understanding of the evolution and function of nervous systems across animal diversity. Within Pancrustaceans, past immunohistochemical analyses of neuropeptide distribution have largely focused on representatives of the decapod (‘ten-legged’) crustaceans and hexapods, leaving other taxa understudied in this respect. In this context one neuropeptide family of interest are the SIFamides, which are highly conserved in Arthropoda and appear to be involved in the integration of diverse sensory stimuli and behaviours like aggression, mating and sleep. Using immunohistochemistry, we provide a map of SIFamide in the post-embryogenic and adult brain and ventral nerve cord of the amphipod Parhyale hawaiensis. Strong SIFamide-like immunoreactivity was detected in the primary processing centres of sensory input, including lamina and olfactory lobe, as well as higher integrative centres such as the central body. Additionally, we consistently found three individually identifiable neurons within the central brain of adult and subadult animals. Analysis of the subesophageal and two adjacent thoracic ganglia of the ventral nerve cord, performed in adult animals, also revealed robust SIFamide-like labelling. This adds new comparative insights into nervous system function and evolution across Pancrustacea, including hexapods.