. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. leads to the central nervous system. The structural common denominator for all chemosensory cells is the presence of ciliary or microvillar extensions into the environment. The peripheral cells of the spionid palps and prostomium clearly meet this requirement (Figs. 2, 3). Dauer (1984, 1987. 1991, 1997) and Worsaee (2001) observed nonmotile cilia on palps and prostomia of several spionid species, including Dipolydora quadrilobata, and classified them as sensory on the basis of scanning electron microscopy data and positional
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. leads to the central nervous system. The structural common denominator for all chemosensory cells is the presence of ciliary or microvillar extensions into the environment. The peripheral cells of the spionid palps and prostomium clearly meet this requirement (Figs. 2, 3). Dauer (1984, 1987. 1991, 1997) and Worsaee (2001) observed nonmotile cilia on palps and prostomia of several spionid species, including Dipolydora quadrilobata, and classified them as sensory on the basis of scanning electron microscopy data and positional criteria. Our initial TEM observations (Figs. 4, 5) support these classifications, and suggest that these peripheral sensory cells have features similar to the caudal chemoreceptors that Jouin el ai. (1985) described in Arenicola marina—namely an abun- dance of apical mitochondria and short ciliary rootlets. Confocal laser scanning microscopy further reveals axonal processes to palp nerves from the lateral and abfrontal sensory tufts (Fig. 6), as well as many free nerve endings projecting to the lateral and abfrontal surfaces of the palps. Assigning function to cells based solely on morphologi- cal criteria can be difficult, however. For example, it ap- pears that no single morphological character defines che- moreceptor cilia: on the crustacean aesthetasc, olfactory cilia can have "significant" ciliary rootlets and motile cilia (Griinert and Ache, 1988). We used the activity-dependent labeling experiments to explore the possible function of the palp sensory cells. Although we designed the experiment to assay for cell activity in the presence or absence of chemical cues (amino acids), it is important to note that this method of labeling active sensory cells does not discriminate be- tween types of receptors. It simply identifies cells that have accumulated agmatine, regardless of the stimulus source. Thus, the labeled cells may include a variety of sensory cell typ
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
