. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AM. B Figure 2. Relative positions of components of the apical sensory organ in veligers ofTectuiu .\i-niitin at 52 h postfertilization (A) and 90 h postfertilization (B). Sketches are traced from transmission electron micrographs of sections cut parallel to the apical surface of the larva at a level close to the epithelial surface (same enlargement for both sketchesl. Numbers refer to groups of dendrites (see text). Arrows indicate that dendrites in groups 5 and 6 join those of groups 3 and 4, respectively, at a deeper leve
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AM. B Figure 2. Relative positions of components of the apical sensory organ in veligers ofTectuiu .\i-niitin at 52 h postfertilization (A) and 90 h postfertilization (B). Sketches are traced from transmission electron micrographs of sections cut parallel to the apical surface of the larva at a level close to the epithelial surface (same enlargement for both sketchesl. Numbers refer to groups of dendrites (see text). Arrows indicate that dendrites in groups 5 and 6 join those of groups 3 and 4, respectively, at a deeper level. Filled profiles are dendrites of serotonin-immunoreactive neurons; unfilled profiles are dendrites from other sensory neurons ot the apical ganglion. Abbreviations: AM, dendrite of ampullary neuron; AP, apical pit; ATC, apical tuft cell; LTC, lateral tuft cell. Orientation arrows, D. dorsal; L, left; R, right; V, ventral. Figure 2A, is largely due to the fact that the middle zone of these cells becomes progressively longer and narrower be- tween 52 and 90 h postfertilization. Cilia arising from the lateral ciliary tuft cells are anchored by forked, striated rootlets that are much shorter than the ciliary rootlets ex- tending from the basal bodies of apical tuft cilia Apicul i>un^li(in The larval apical ganglion of T. scutum is a cluster of neurons located immediately beneath the dorsal half of the apical epidermal disc. Most and possibly all of the apical ganglion neurons give rise to distal cytoplasmic extensions (putative dendrites) that extend to the exposed epidermal surface of the larva within the plus-shaped apical ciliary field. Two to four cilia arise from the distal terminals of these dendrites. The sketch in Figure 2A shows the positions of the dendritic terminals, relative to the apical and lateral ciliary tuft cells and the apical pit, in veligers at the onset of ontogenetic torsion. The sensory dendrites at the exposed surface of the apical epithelium are clu
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
