Fig. 3From: Massive expansion and diversity of nicotinic acetylcholine receptors in lophotrochozoansMassive intronless nAChR genes in molluscs. a Number of nAChR genes with > 2, 1–2 and no introns in different species. b Neighbor-joining tree of nAChRs from C. gigas, P. f. martensii and H. sapiens, showing lineage-specific expansion and close relationship between nAChR genes with no or 1–2 intronsBack to article page