Engrailed-like immunoreactivity in the embryonic ventral nerve cord of the Marbled Crayfish (Marmorkrebs)

Abstract

The homeobox transcription factor Engrailed is involved in controlling segmentation during arthropod germ band formation but also in establishing individual neuronal identities during later embryogenesis. In Crustacea, most studies analysing the expression of Engrailed so far have focussed on its function as segment polarity gene. In continuation to these previous studies, we analysed the neuronal expression of the Engrailed protein by immunohistochemistry in the embryonic nerve cord of a parthenogenetic crustacean, the Marbled Crayfish (Marmorkrebs). We paid particular attention to the individual identification of Engrailed expressing putative neuroblasts in the crayfish embryos. Engrailed positive cells in the neuroectoderm were counted, measured and mapped from 38 to 65% of embryonic development. That way, several Engrailed positive putative neuroblasts and putative neurons were identified. Our findings are compared with earlier studies on Engrailed expression during germ band formation in Crustacea. Recent data on neurogenesis in an amphipod crustacean have provided compelling evidence for the homology of several identified neuroblasts between this amphipod and insects. The present report may serve as a basis to explore the question if during crustacean neurogenesis additional communalities with insects exist.

Axogenesis in the stomatopod crustacean Gonodactylaceus falcatus (Malacostraca)

“…Several neural apomorphic similarities are shared by hexapods and crustaceans to the exclusion of myriapods, e.g., the development of neuronal cells from neuroblasts (summarized in Richter & Wirkner 2004;Stollewerk & Simpson 2005;Fabritius-Vilpoux et al 2008; and the pattern of outgrowing axons of pioneer neurons (Bate & Grunewald 1981;Thomas et al 1984;Whitington et al 1991Whitington et al , 1993; for overview, see Whitington 2004Whitington , 2007. Hence, in addition to molecular data, it is mainly developmental and anatomical characters of the nervous system that have led to the Tetraconata or Pancrustacea hypothesis (e.g., Zrzavy´& Sty´s 1997; Giribet & Ribera 2000;Dohle 2001;Richter 2002;Mallatt et al 2004;Giribet et al 2005;Regier et al 2005).…”

Combining Old and New Tricks: The Study of Genes, Neurons, and Behavior in Crayfish

“…Marbled crayfish neurobiology is currently a wide-open field, and the number of publications is still very modest. Early work focused on the development of the nervous system and some of its neurotransmitters ( Vilpoux et al, 2006 ; Polanska et al, 2007 ; Fabritius-Vilpoux et al, 2008 ; Rieger and Harzsch, 2008 ). More recently, studies have investigated adult neurogenesis ( Brenneis et al, 2021 ), operant conditioning ( Okada et al, 2021 ), phototaxis ( Shiratori et al, 2017 ), and psychostimulant actions on marbled crayfish behavior ( Jackson and van Staaden, 2019 ).…”

Development of the nervous system in hatchlings of Spadella cephaloptera (Chaetognatha), and implications for nervous system evolution in Bilateria

“…The longitudinal tracts, where paired, are assumed to represent a potentially circumblastoporal component ( sensu Nielsen) even where they do not form a complete loop; the stomatogastric nerves more typically do form a loop, with or without ganglia, around the mouth, though the relation of the latter to the blastopore clearly differs between groups. Taxa with a clearly identifiable stomodeal invagination include arthropods (D, D′; a crustacean [egg] nauplius stage, modified from Fabritius‐Vilpoux et al. 2008) and protostomes with a muscular pharynx, e.g.…”