Contribución a la sistemática de "Vipera seoanei" Lataste, 1879 ("Reptilia, Viperidae"). I. Ultraestructura de la cutícula de las escamas

Abstract

In this paper the results of a research work on the ultrastructural morphology of the scales' cuticle of four species of European Viperidae (Vipera b. berus, V. seoanei, V. aspis and V. latastei) are presented. The motivation of the study has been the enquiry about the transformation of the subspecies. V. berus seoanei in to the species V. Seoanei (LATASTE, 1879).
Scanning microscopical techniques have been used (see HEYWOOD, 1971; COLE & VAN DEVENDER, 1976; GANS & BAIC, 1977). For each species, facial, labial, ventral and dorsal scales from several specimens, caught in different localities, have been studied.
From the different observations, it has been possible to define the kind of cuticle growth, mainly the dorsal one. The cuticle base (which is the imbrication zone between two scales) presents several dented strias, more or less parallel. A differential process takes place, and dented series with anterior sharp points are originated. These points are driven in to the base of the anterior ones that originate long cords. Between each two points some other fibres are born which, on its turn, form nets or arcs. For each one of the four studied species the growth results are different.
V. b. berus presents a uniform structure, formed by parallel fibres. In V. seoanei, the fibres form transversal arcs in a regular way. In V. aspis, fibres form thick fascicles, with transversal arcs between them. In V. latastei, the structure is more complex than that of V. aspis because there are several arcs between the fibrilar cords. All these structures are specifical and there are not variations among the different studied populations of each species.
For each species the cuticular ultrastructure at the end of the growth period is the same for all the scales. The only exception are the ventral scales, that are very similar in all the species. It seems that they are stopped in a intermediate growth phase.
As one can see, the cuticle ultrastructure of V. seoanei is intermediate between these of V. b. berus and V. aspis. It is possible to think that V. seoanei was originated by a hybrid of V. b. berus and V. aspis when the interspecific crossing was still possible. Anyway, the results agree with the conclusions of SAINT GIRONS & DUGUY (1976).
The structure sequence would be: Vipera b. berus, V. seoanei, V. aspis and V. latastei. From V. b. berus to V. latastei the cuticle increases in thickness. The more meridional the species distribution, the thicker is the cuticle, and also more complex. I think this would be an adaptation to the evaporation. Although V. aspis can be found at the same latitude as V. seoanei, the former lives in higher places than the latter and its termopreferendum is lower.