CYTOCHEMICAL INVESTIGATIONS ON TUNIC MORPHOGENESIS IN THE SEA PEACH HALOCYNTHIA-PAPILLOSA (TUNICATA, ASCIDIACEA) .2. DEMONSTRATION OF PROTEINS

In a previous paper, cellulose fibres were demonstrated in the larval, the metamorphosing, and the juvenile tunics. In this paper we used cy tochemical methods and X-ray microanalysis to obtain additional inform ation on tunic morphogenesis in Halocynthia papillosa. The chemical co mposition of the tunic evolves with its structural complexity. The lar val and juvenile fibres are shown to be structurally and chemically di fferent. While neither proteins nor glycosaminoglycans seem to be asso ciated with the larval fibres, the juvenile fibres consist of a cellul ose core wrapped in a sheath of tannophilic proteins. Patches of glyco saminoglycans line their longitudinal axes. In the course of metamorph osis, the cuticle undergoes profound modifications in regions of spine morphogenesis. Granular material that was previously called fibro-gra nular material (Lubbering et al., 1993) is essential to the formation of cuticular plates and spines. During metamorphosis, this material ac cumulates in epidermal granules and is discharged into the tunic. It c rosses the fundamental layer of the tunic and reaches the cuticle. Our results strongly suggest that this material consists of proteins rich in cysteine and hydrophobic amino acids.