Structure—function relationships in the integument of Salamandra salamandra during ontogenetic development

Abstract

Morphological, cytological and transport properties of the integument of Salamandra salamandra were investigated during natural ontogenetic development, from birth to adult. Three stages were operationally defined: I, larvae, from birth to metamorphosis; II, metamorphosis (judged externally by the colour change and loss of the gills); and III, post-metamorphosis to adult. Pieces of skin were fixed at various stages for immunocytochemical examinations, and the electrical properties were investigated on parallel pieces. Distinct cellular changes take place in the skin during metamorphosis, and lectin (PNA, WGA and ConA) binding indicates profound changes in glycoprotein composition of cell membranes, following metamorphosis. Band 3 and carbonic anhydrase I (CA I) were confined to mitochondria-rich (MR)-like cells, and were detected only in the larval stage. CA II on the other hand, was detected both in MR-like and in MR cells following metamorphosis. The electrical studies show that the skin becomes more tight (transepithelial resistance increases) upon metamorphosis, followed by manifestation of amiloride-sensitive short-circuit current (I(SC)) indicating that functional Na+ uptake has been acquired. The skin of metamorphosed adults had no finite transepithelial Cl- conductance, and band 3 was not detected in its MR cells. The functional properties of MR-like and MR cells remain to be established.

Skin epithelial transport and structural relationships in naturally metamorphosing Pelobates syriacus

“…Similar conclusion for this sequence of transport capacity following tightening can be drawn for Rana catesbeiana larval development (Cox and Alvarado,'79; Fig. 3), as well as in Salamandra (Pederzoli et al, 2002). Selective permeability changes seem therefore to be prerequisite for transepithelial Na þ transport to be expressed.…”

“…It shows that a similar pattern of functional and structural changes common to both anurans (Cox and Alvarado,'79) and urodeles (Pederzoli et al, 2002) takes place in the acquirement of active Na þ transport properties of amphibian skin epithelium during metamorphosis.…”

“…However, the temporal changes in the binding of the above two probes do not correlate with the appearance of activated G Cl (Table 1), and provides direct evidence that band three protein is not a necessary component of the activated G Cl . In Salamandra on the other hand, band three protein was confined to the single cells of the larval integument and absent from the skin epithelial MR cells (Pederzoli et al, 2002), both lacking activated G Cl . H þ ATPase was detected in MR cells of Rana esculenta (Klein et al,'97), Bufo marinus (Brown and Breton,'96), and Xenopus laevis (Katz and Gabbay, unpublished observations), but not in MR cells of Pelobates.…”

“…It was verified earlier that the different cellular composition of the integument of tadpole and the adult changes upon metamorphosis (Gabbay et al,'92). Other studies addressed the question of transformation in the epithelial function, particularly of Na þ transport both in anurans and urodeles (Takada, '85;Hillyard and Van Driessche, '91;Pederzoli et al, 2002). In the latter study of Salamandra skin, it was observed that band three protein, assumed to be involved in Cl À translocation is localized to the single dispersed cells of the larval stage and not to MR cells of the adult.…”

“…In the latter study of Salamandra skin, it was observed that band three protein, assumed to be involved in Cl À translocation is localized to the single dispersed cells of the larval stage and not to MR cells of the adult. It suggested that activated epithelial G Cl could be associated with band three protein since the latter lacks activated G Cl (Pederzoli et al, 2002). The large size of Pelobates tadpoles provides a convenient experimental model for reproducible electrical investigation, parallel with morphological and immunocytochemical study.…”