Stefania Bucci-Innocenti

Experimental hybridization within the genus Triturus (Urodela: Salamandridae)

The spermatogenesis of 9 F1 hybrids of Triturus cristatus carnifex ♀ × T. vulgaris meridionalis ♂ was studied in squash preparations of testicular fragments, treated by the C-staining method. The chromosome number of these hybrids was examined in spermatogonial metaphases and found to be diploid. The two parental sets were always recognized, which means that a regular, although heterospecific, amphimixis occurred (2n=n♀+n♂). Meiotic prophase I is greatly altered owing to a failure of typical chromosome pairing and chiasma formation. At metaphase I and/or meta-anaphase I, the effects of the hybrid combination of the 2 specific parental sets are clearly visible. Most primary spermatocytes contain only univalents. A few show chromosome associations (bivalents, trivalents and, more rarely, quadrivalent chains) besides univalents. Such associations are of 2 types: (a) intragenomal associations = associations of 2 chromosomes by a terminal (a1) or subterminal chiasma (a2); (b) intergenomal associations = associations of 2 chromosomes by a terminal (b1) or subterminal chiasma (b2). Univalents segregate at random while the associations often lag on the equatorial plane or migrate entire to a spindle pole. Primary spermatocytes with chromosome multivalents can encounter greater difficulties in accomplishing the first cytokinesis. Secondary spermatocytes are numerically and qualitatively unbalanced; however, some of them undergo spermiogenesis and can give rise to a small number of sperms, generally abnormal and never united in bundles. — Problems related to the occurrence of “anomalous” chiasmata and of intra- and inter-genomal homologies are discussed.

Chromosome and C-heterochromatin polymorphisms in the Italian newt, Triturus italicus

A combined chromosome and C-heterochromatin polymorphism in pair 12 in the complement of the newt species, T. italicus is described. The C-heterochromatin polymorphism is presumably due to a loss in the proximal C-band, whereas the chromosomal polymorphism has its origin in two different independent pericentric inversions both including the centromere and the proximal C-band of chromosome 12. The double-inversion polymorphism has a wide distribution over the range and follows a clear bipolarity between a northern area where the karyotype is homomorphic for the standard type of pair 12 (ST/ST) and an opposite area where the ST type is completely replaced by variant M1 and M2 metacentric chromosomes 12. Various karyophylogenies are possible, but the simplest and the most probable presumes an ancestral karyotype of ST/ST and a mechanism of gradual replacement of the heterobrachial chromosome ST by two independent pericentric inversions. The present data are discussed in relation to existing theories on karyological evolution of Urodeles and the functional significance of telocentric chromosomes suggested by Sessions et al. (1982).

Chromosome polymorphism in the Italian newt, Triturus italicus.

A chromosomal variation, changing shape and C-banding pattern of chromosome XII of Triturus italicus was detected among the offspring of two F1 hybrid families of T. italicus ♀ × T. vulgaris meridionalis ♂. In both families a number of individuals appeared to have a metacentric instead of the expected subtelocentric chromosome XII of T. italicus. — Investigations in three well separated localities in the range of the species showed the polymorphism to have a wide distribution and to be part of a complex pattern involving at least two inversions and (presumably) deficiencies of large C-bands. At meiosis, the shape of bivalent XII, and the location and frequency of chiasmata in the bivalent varied with the karyomorph involved. It is suggested that large rearrangements may still play an important role in the karyological evolution of Triturus.

An ammoniacal silver staining technique for mitotic chromosomes ofTriturus (Urodela: Salamandridae)

An ammoniacal silver staining technique was applied to mitotic metaphase chromosomes of 2 species of Newts (Triturus). The method is useful for identifying nucleolar organizer regions. In addition, it reveals other sites of unknown significance.

The karyotypes of the Corsican and Sardinian mountain salamanders, Euproctus montanus and E. platycephalus (Urodela: Salamandridae).

The chromosomes ofEuproctus montanus andE. platycephalus were studied by means of the C-banding method and the AS-SAT technique which are useful for identifying the single pairs of the complement and for recognizing nucleolar organizer regions. According to the morpho-structural characteristics shown by the specific karyotypes, it has been possible to draw some cytotaxonomic deductions concerning the karyological evolution within the insular group.

Karyology of the Carpathian Newt Triturus Montandoni and Cytotaxonomic Considerations on the Species Group T. Vulgaris (Urodela: Salamandridae)

SUMMARYThe karyological knowledge of the Carpathian newt T. mpntandoni has been improved by the study of the mitotic chromosomes banded by the C-banding method and the analysis of the ovarian giant lampbrush chromosomes. The karyotype appears very similar, although not overlapping to that of the allied species T. vulgaris, as it results also from the analysis of hybrid complements. A modification of the content of the three species groups or Artenkreise including the European newts appears necessary, also on the basis of recent hybridological investigations.

Immunochemical identification of vitellogenin in the serum of the newt Triturus cristatus

The hematic yolk precursor — vitellogenin — has been identified immunochemically in the serum of estrogenized females of the newtTriturus cristatus by employing an antiserum prepared against yolk proteins.

Karyology of Neurergus strauchii (Steindachner, 1887) (Urodela: Salamandridae) and Cytotaxonomic Considerations on Palearctic Salamandrids

The karyotype of Neurergus strauchii shows pericentric and subterminal C-bands heterochromatin and nucleolar organizers on chromosome IX. This site is revealed by both a C-band and a chromomycin A3 fluorescent band; the GC-specific fluorochrome also highlights additional sites of fluorescence. The lampbrush chromosomes have a general morpho-structural feature known for Triturus lampbrush chromosomes, but giant loops are lacking. Nucleolar organizer and sphere sites are the main cytogenetic markers in the lampbrush karyotype of Neurergus. The implication of these results to our understanding of cytotaxonomy and evolutionary biology of Palearctic Salamandrids is discussed.

C-Banded Karyotype and Cytotaxonomy of Mertensiella caucasica (WAGA, 1876) (Caudata: Salamandridae)

Chromosome number, karyotype and chromosomal banding pattern of Mertensiella caucasica were studied in differentially stained mitotic preparations. The main feature of the C-banded appearance concerns the centromere regions, which are heavily stained by the Giemsa and are outlined by proximal C-bands. This morpho-structural character seems to be peculiar of the genome of M. caucasica, when compared with the C-banding pattern shown by the chromosomes of Salamandra, considered the most closely related form. Therefore, a preliminary cytotaxonomic survey seems to support the opinion that the Caucasian salamander can be referred to a well defined genus Mertensiella rather than a subgenus of Salamandra.

Experimental Hybridization within the Genus Triturus (Urodela: Salamandridae). II. The Lampbrush Chromosomes of F1 Species Hybrids Between Triturus Cristatus Carnifex and T. Vulgaris Meridionale

SUMMARYThe lampbrush phase of 6 F1 female hybrids of Triturus cristatus carnifex ♀ × T. vulgaris meridionalis ♂ and 1 female hybrid of the reciprocal cross was analyzed in several growing oocytes. The chromosome constitution of these hybrids was found to be diploid and derived from a regular, although heterospecific amphimixis (2n= n♀ + n♂). All the oocytes contained 24 unpaired lampbrush chromosomes, among which the single univalents of the 2 parental sets were recognized by their cytogenetic markers (loops, spheres, NORs, other objects and lateral projections). Lampbrush univalents can be joined to one another by transitional fusions of spheres and telomeres and, occasionally, by very rare chiasmata which may be defined as anomalous since they form between heterologous chromosomes and probably represent a further impediment to subsequent meiotic stages. Problems concerning chromosomal homologies and cytogenetic aspects of sexuality and sex determination in these species hybrids have been discussed in th...