The search for ancestral nervous systems: an integrative and comparative approach

Abstract

Even the most basal multicellular nervous systems are capable of producing complex behavioral acts that involve the integration and combination of simple responses, and decision-making when presented with conflicting stimuli. This requires an understanding beyond that available from genomic investigations, and calls for a integrative and comparative approach, where the power of genomic/transcriptomic techniques is coupled with morphological, physiological and developmental experimentation to identify common and species-specific nervous system properties for the development and elaboration of phylogenomic reconstructions. With careful selection of genes and gene products, we can continue to make significant progress in our search for ancestral nervous system organizations.

Atlas of the neuromuscular system in the Trachymedusa Aglantha digitale: Insights from the advanced hydrozoan

“…Neural systems in cnidarians and medusozoans, in particular, are very complex and diverse with multiple adaptive modifications reflecting long evolutionary histories in these lineages. Cnidarian neurons cannot be viewed as simple neural nets (see reviews Satterlie & Spencer, ; Satterlie, , , , ; Mackie, ), rather they are comparable in their heterogeneity and multifunctionality to bilaterian nervous systems.…”

“…Each of this lineage shows examples of centralized neural systems (Mackie, ; Satterlie, ). The jellyfishes' CNSs coexist together with the diffuse nerve nets, which might represent a secondary adaptation to control two‐dimensional myoepithelial subumbrella, and therefore, mediate synchronous contractions of the bell and jet‐propulsion locomotion (Satterlie, , ).…”

“…Neural systems in cnidarians and medusozoans, in particular, are very complex and diverse with multiple adaptive modifications reflecting long evolutionary histories in these lineages. Cnidarian neurons cannot be viewed as simple neural nets (see reviews Satterlie & Spencer, 1983;Satterlie, 2002Satterlie, , 2011Satterlie, , 2015aSatterlie, , 2015bMackie, 2004) (Eakin & Westfall, 1962;Singla, 1978a;Spencer, 1978Spencer, , 1979King & Spencer, 1979;Weber, 1982;Grimmelikhuijzen & Spencer, 1984;Arkett, 1985;Anderson & Spencer, 1989;Spencer, Przysiezniak, Acosta-Urquidi, & Basarsky, 1989;Przysiezniak & Spencer, 1992, 1994Lin, Gallin, & Spencer, 2001) and Aequarea (Colin & Costello, 2002;Horridge, 1955;Satterlie, 1985aSatterlie, , 1985bSatterlie, , 2008.…”

“…Thus, Eumetazoa could be a polyphyletic taxon, and Cnidaria is a key reference group to understand the origin of integrative systems in bilaterians. However, cnidarian neuromuscular systems are highly diverse in their structures and forms, which reflect enormous biodiversity within this group (Bullock & Horridge, ; Leitz, ; Mackie, ; Satterlie, , , ; Spencer & Arkett, ; Steinmetz et al, ).…”

“…Most detailed recent studies of cnidarian neuromuscular systems are focused on two reference species (Leitz, 2016): Hydra (a highly specialized freshwater hydrozoan, which lost the medusa stage) and Nematostella (an anthozoan, with a primary absence of medusas in its life cycle). Unfortunately, Medusozoa received less attention of neuroscientists, despite substantial and widespread occurrences of jellyfishes word-wide (see reviews Satterlie & Nolen, 2001;Satterlie, 2002Satterlie, , 2011Satterlie, , 2015aSatterlie, , 2015bMackie, 2004;Steinmetz et al, 2012).…”