Divergent patterns of neural development in larval echinoids and asteroids

Abstract

The development and organization of the nervous systems of echinoderm larvae are incompletely described. We describe the development and organization of the larval nervous systems of Strongylocentrotus purpuratus and Asterina pectinifera using a novel antibody, 1E11, that appears to be neuron specific. In the early pluteus, the antibody reveals all known neural structures: apical ganglion, oral ganglia, lateral ganglia, and an array of neurons and neurites in the ciliary band, the esophagus, and the intestine. The antibody also reveals several novel features, such as neurites that extend to the posterior end of the larva and additional neurons in the apical ganglion. Similarly, in asteroid larvae the antibody binds to all known neural structures and identifies novel features, including large numbers of neurons in the ciliary bands, a network of neurites under the oral epidermis, cell bodies in the esophagus, and a network of neurites in the intestine. The 1E11 antigen is expressed during gastrulation and can be used to trace the ontogenies of the nervous systems. In S. purpuratus, a small number of neuroblasts arise in the oral ectoderm in late gastrulae. The cells are adjacent to the presumptive ciliary bands, where they project neurites with growth cone-like endings that interconnect the neurons. In A. pectinifera, a large number of neuroblasts appear scattered throughout the ectoderm of gastrulae. The cells aggregate in the developing ciliary bands and then project neurites under the oral epidermis. Although there are several shared features of the larval nervous systems of echinoids and asteroids, the patterns of development reveal fundamental differences in neural ontogeny.

Par6 regulates skeletogenesis and gut differentiation in sea urchin larvae

“…5c). The apkc-expressing cells in the ciliary band do not appear to match the serotonergic cells (four to six cells in the apical ganglion; Bisgrove and Burke 1986) or synaptotagmin-expressing cells (flask-shaped cell bodies on the basal side of ectoderm; Nakajima et al 2004), although apkc-expressing cells may partially overlap the neural cells. In par6 morphants, the first and second phases of apkc expression occurred as they do in controls (Fig.…”

Gonad-stimulating substance-like molecule from the radial nerve of the sea cucumber

“…The exploration of nervous system in the echinoderm larvae and adult made great strides during past decade in sea urchins (e. g. Beer et al, 2001;Sly et al, 2002;Yaguchi and Katow, 2003;Katow et al, 2004;Nakajima et al, 2004;Burke et al, 2006;Katow et al, 2007;Katow, 2008), starfishes (e.g. Elphick et al, 1995;Byrne et al, 2005), sea cucumbers (e.g.…”

Direct development of neurons within foregut endoderm of sea urchin embryos

“…cell fate specification | embryonic development | neurogenesis | enteric nerve T he nervous system of the sea urchin consists of an highly ordered array of neurons that develop sequentially in the anterior neuroectoderm, within or near the ciliary band, and in the pharyngeal region (1,2) (Fig. 1).…”