Cytochemical investigations on tunic morphogenesis in the sea peach Halocynthia papillosa (Tunicata, Ascidiacea). 1: demonstration of polysaccharides.
The distribution of carbohydrates was demonstrated in the embryonic, larval, and juvenile tunics of Halocynthia papillosa. An enzyme-gold marker (cellobiohydrolase-Au) was used to identify cellulose on ultrathin sections. This is the first time this biopolymer has been detected in the embryonic or larval tunic of an ascidian. Cellulose is present from the initial tail-bud stage onwards, as soon as the outer compartment of the tunic appears. Both compartments of the larval tunic also contain non-cellulosic polysaccharides, as demonstrated by the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) method. Our observations point to two types of cellulose synthesis. One occurs during the embryonic and larval stages, when glycogen-like material is stored in epidermal intracellular lacunae and discharged into the tunic where it is presumably used to synthesize cellulose throughout the depth of the tunic. The second occurs from the onset of metamorphosis onwards, just above the apical plasmalemma of epidermal cells, like cellulose biogenesis in plants.
Lübbering-Sommer
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Laboratoire de Biologie générale et de Morphologie ultrastructurale, Université de Liège, Institut de Zoologie, 22 Quai Van Beneden, Liège, Belgium.
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Goffinet
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