A Rostral Sensory Mechanism in Oikopleura dioica (Appendicularia)

Abstract

Bollner, T., Holmberg, K., Olsson, R. 1986. A rostra1 sensory mechanism in Oikopleura dioica (Appendicularia). (Department of Zoology, University of Stockholm, Sweden.)-Acta zoof. (Stockh.) 67, 235-241.The ventral sense organ, below the mouth, is composed of 30 primary sensory cells situated in a row perpendicular to the long axis of the animal. Each cell carries one long and slender, modified cilium which arises from ap apical pocket in the cell. The sensory cells project 15 axons at each side of the pharynx to the brain, which is rostrally paired and terminates in bulb-like swellings. Each of these bulbs contains four cell bodies, which, according to their fine structure, as well as the synaptic connections with receptor and brain fibers, belong to three different types. It is suggested that the sense organ is a chemosensor and that its remarkable similarity to the vertebrate mechanisms for olfaction makes it probable that the appendicularian Oikopleura dioica possesses a 'protochordate' counterpart to the craniate olfactory apparatus.

Characterization of novel GPCR gene coding locus in amphioxus genome: Gene structure, expression, and phylogenetic analysis with implications for its involvement in chemoreception

“…It therefore appears that Amphi-GPCR-positive cells may be preliminary versions of the vertebrate olfactory sensory neurons, and that they could be supposed to be chemosensory in function. Bollner et al (1986) observed primary sensory neurons in the rostral epithelium of appendicularians, which represent a sister-group of the clade of the other urochordates (Wada, 1998), and proposed that they were counterparts of the vertebrate olfactory sensory neurons. If so, olfactory-related chemosensory cells in the rostrum may be a shared feature of the chordates.…”

The evolutionary history of placodes: a molecular genetic investigation of the larvacean urochordate Oikopleura dioica

“…Olsson, 1986;Cañestro et al, 2005). Its CNS consists of an enlargement, the 'anterior brain', containing fewer than 70 cells (Georges et al, 1988;Martini, 1909) (Fig.…”

“…These cells are primary sensory cells like vertebrate olfactory receptor cells, and their axons integrate into the rostral-most CNS (Bollner et al, 1986). To reflect these structural similarities to the vertebrate olfactory epithelium, they were called olfactory or chemosensory cells by various authors, although their function is unknown (Bollner et al, 1986;Lohmann, 1933).…”

“…The dilated cilia of the sensory cells of the ventral organ protrude into the environment from a slit-like pocket of ectoderm (Bollner et al, 1986). These cells are primary sensory cells like vertebrate olfactory receptor cells, and their axons integrate into the rostral-most CNS (Bollner et al, 1986).…”

“…Developmental morphologists proposed that the 'ventral organ' and the 'ciliary funnel' in the larvacean urochordate Oikopleura dioica, are homologs of the olfactory organ and the pituitary (Bollner et al, 1986;Holmberg, 1982;Olsson, 1969). The dilated cilia of the sensory cells of the ventral organ protrude into the environment from a slit-like pocket of ectoderm (Bollner et al, 1986).…”