Talpa Occidentalis Research Articles

Sequential silver staining and in situ hybridization reveal a direct association between rDNA levels and the expression of homologous nucleolar organizing regions: a hypothesis for NOR structure and function.

We have developed a procedure for sequential silver staining and in situ hybridization to analyze the relationship between the amount of rDNA present in nucleolar organizer regions, as estimated by in situ hybridization, and their level of expression, as estimated by the silver signal. For simplicity we used cells from the insectivorous mole Talpa occidentalis, which have a single pair of nucleolar organizer regions in chromosome pair 3. The relative content of ribosomal cistrons was also related to the hierarchy of activation of the nucleolar organizer regions present in this chromosomal pair. Statistical analyses demonstrated that both the relative level of expression and the activation hierarchy depended mainly on the number of ribosomal cistrons in nucleolar organizer regions. We propose a functional two-step hypothesis, which is consistent with most known data concerning interchromosomal, intercellular and interindividual variation in a number of plant and animal species, including Talpa occidentalis. In step one, the first available transcription factors bind randomly to the ribosomal promoters, such that larger nucleolar organizer regions are more likely to recruit them. In the second step the remaining transcription factors are recruited in a cooperative way, thus completing activation of one nucleolar organizer region, before the next one becomes active.

Interchromosomal, intercellular and interindividual variability of NORs studied with silver staining and in situ hybridization.

We investigated the relationship between transcriptional activity and the quantity of ribosomal cistrons of the nucleolar organizing regions (NORs) in chromosomal pair 3 of the Spanish mole Talpa occidentalis. Transcriptional activity was estimated by the size of conventional silver-staining signals. The number of ribosomal cistrons was estimated by the size of the in situ hybridization signals obtained with a ribosomal DNA probe. A sample of cells was studied with each method in four different individuals, and the results obtained with the two techniques were compared. Furthermore, sequential analysis on the same cells was carried out to study the association of interstitial nucleolar constrictions with silver staining and in situ hybridization. Interchromosomal, intercellular and interindividual variability were found with both silver staining and in situ hybridization methods. Our results show that transcriptional activity of NORs does not depend exclusively on the number of ribosomal cistrons they have as a high percentage of cells had two NORs with abundant ribosomal cistrons, only one of which was active. Additional factors, probably responsible for the activation of transcription, may be involved in this variability.

Ovotestis variability in young and adult females of the mole Talpa occidentalis (insectivora, mammalia).

The age-related evolution and ontogenic origin of the ovotestes in fertile females of the Spanish mole (Talpa occidentalis) were studied. Volume of the ovotestis and its ovarian and testicular components, size of the epididymis and testicular cords, number of ovarian follicles and testicular cords, uterus weight, and age index were analyzed statistically in a large sample of young and adult individuals of this species. Comparison of means and linear correlation analyses were done. Most variables were shown to be age dependent, with a period of rapid change during puberty. In adult animals, volume of the ovarian portion and uterus weight followed a seasonal cycle of sexual activity. Interindividual variability was evident in most of the variables investigated except for the number of testicular cords per ovotestis, which remained unchanged throughout the animal's life and hence was not inversely correlated with the number of ovarian follicles. This finding ruled out an ovary-testis transdifferentiation hypothesis for the ontogenic origin of the testicular tissue in the ovotestes of female moles. An alternative hypothesis based in the absence of oocytes in a portion of the undifferentiated fetal gonad is proposed in accordance with a new general model for mammalian sex determination.

Fertile females of the mole Talpa occidentalis are phenotypic intersexes with ovotestes

We investigated the origin of XX sex reversal in the insectivorous mole Talpa occidentalis. Cytogenetic, histological and hormonal studies indicate that all XX individuals analyzed from two different populations are true hermaphrodites, with ovotestes. This suggests that XX sex reversal may be the norm in this species. The intersexes are functional fertile females and the trait is transmitted and maintained in the population. Intersexes lack the Y chromosome gene SRY (sex determining region Y gene), shown to be the testis determining gene. These results suggest that XX intersex moles may have arisen from a mutation of a gene located downstream from SRY/TDY in the testis determining pathway.

The reproductive cycle of Talpa occidentalis in the southeastern Iberian Peninsula

The small Iberian mole Talpa occidentalis Cabrera, 1907, is sexually active during a period lasting from September to May. Both males and females reach season maturity after the age of one year, and their reproductive organs undergo seasonal histological and functional fluctuations.

Synaptonemal complex analysis of spermatocytes of <i>Talpa occidentalis</i>(Insectivora, Mammalia): autosomal synapsis and substaging of zygonema and pachynema

Spermatocytes from the mole, Talpa occidentalis, a species that includes both XX males and intersexes, were surface-spread and silver-stained to substage meiotic prophase from early zygonema through pachynema. In zygonema, only the Z2 and Z3 substages were found. This stage differed in comparison with such species as the Chinese hamster, laboratory mouse, and deer mouse, which belong to orders other than Insectivora. Pachynema, in which five substages were established (P1-P5), seems to be a more homogeneous stage, and remarkable differences with respect to the above-mentioned species were not found. Synaptic adjustment was demonstrated in X-Y pairing. Nonhomologous pairing was evident at the Y-centromeric region and considered likely in the proximal arm of this chromosome. In addition to sequencing the events taking place during zygonema and pachynema in males from a wild population in which some members show sex reversal, our finding represents the first attempt to substage zygonema and pachynema in an Insectivore species, thus contributing to current knowledge of the nature and degree of variability in the mammalian synaptic process.

Meiotic behaviour of sex chromosomes and polymeiosis in three species of insectivores

A study of male meiosis has been carried out on air-dried testicular preparations from three insectivore species: Crocidura russula, Neomys anomalus and Talpa occidentalis. Two particularities in relation to the meiotic process were found. The sex-chromosomes show a special allocycly. In the zygotene and pachytene stages, only some cells (a maximum of 50% in some individuals) present a typical sex-vesicle. In the majority of cells in these stages, the X-chromosome appears unfolded, isopycnotic or negatively heteropycnotic, with the ends of the arms together. The Y-chromosome is more condensed and it is associated with the ends of the X-chromosome. At diakinesis and metaphase I the sex chromosomes show end-to-end pairing. A second interesting feature in these species is the existence of spontaneous polymeiosis in a relative high frequency. The origin of this phenomenon, and the influence of these two particularities on fertility and the relation with the phylogeny of these species are discussed.

Karyotype and Chromosome Banding in the Mole (Talpa Occidentalis) from the South-East of the Iberian Peninsula. Implications on its Taxonomic Position

SUMMARYG- and C-band pattern and NOR's of Talpa occidentalis metaphase chromosomes are described. The C-band pattern shows that the chromosomal pair causing karyotypic differences in the genus Talpa presents their short arm totally heterochromatic. The implication of this fact in the karyotypic evolution of this genus and the taxonomic status of T. occidentalis are discussed.

Composition of greek vases

Gorham’s cave is located in the British territory of Gibraltar in the southernmost end of the Iberian Peninsula. The cave was discovered in 1907 and first excavated in the 1950s by John Waechter of the Institute of Archaeology in London. New excavations, which started in 1997, have exposed 18 m of human occupation in the cave, spanning the Late Pleistocene, as well as including brief Phoenician, Carthaginian and Neolithic occupations. The Late Pleistocene levels consist of two Upper Palaeolithic occupations, attributed to the Solutrean and Magdalenian technocomplexes (Level III), and which are dated, by AMS radiocarbon, to between 18,000 and 10,000 years ago. The underlying Mousterian layer (Level IV), dated by AMS radiocarbon to between 23,000 and 33,000 years ago, is separated from Level III by an archaeologically sterile layer, which spans some 4000 years.This paper presents previously unpublished palaeoenvironmental and paleoclimatic reconstructions of Gorham’s cave, during these Pleistocene occupations, using the small mammal assemblage. The small mammal assemblage at Gorham’s cave comprises of at least 12 species: 4 insectivores (Crocidura russula, Sorex gr. coronatus-araneus, Sorex minutus and Talpa occidentalis); 3 chiropters (Myotis myotis, Myotis nattereri and Miniopterus schreibersii); and 5 rodents (Microtus (Iberomys) cabrerae, Microtus (Terricola) duodecimcostatus, Arvicola sapidus, Apodemus sylvaticus and Eliomys quercinus). The presence of these small mammal species indicates that the landscape surrounding the Rock of Gibraltar was predominantly an open habitat, with the presence of woodland and water stream meadows, as well as the presence of larger bodies of water. These results are then compared with pollen and charcoal analysis as well as other faunal proxies, such as the herpetofauna, bird and large mammal assemblages, providing an accurate reconstruction of the climatic and environmental conditions that prevailed during the Late Pleistocene in the southernmost of the Iberian Peninsula.

A carthaginian lamp

Gorham’s cave is located in the British territory of Gibraltar in the southernmost end of the Iberian Peninsula. The cave was discovered in 1907 and first excavated in the 1950s by John Waechter of the Institute of Archaeology in London. New excavations, which started in 1997, have exposed 18 m of human occupation in the cave, spanning the Late Pleistocene, as well as including brief Phoenician, Carthaginian and Neolithic occupations. The Late Pleistocene levels consist of two Upper Palaeolithic occupations, attributed to the Solutrean and Magdalenian technocomplexes (Level III), and which are dated, by AMS radiocarbon, to between 18,000 and 10,000 years ago. The underlying Mousterian layer (Level IV), dated by AMS radiocarbon to between 23,000 and 33,000 years ago, is separated from Level III by an archaeologically sterile layer, which spans some 4000 years.This paper presents previously unpublished palaeoenvironmental and paleoclimatic reconstructions of Gorham’s cave, during these Pleistocene occupations, using the small mammal assemblage. The small mammal assemblage at Gorham’s cave comprises of at least 12 species: 4 insectivores (Crocidura russula, Sorex gr. coronatus-araneus, Sorex minutus and Talpa occidentalis); 3 chiropters (Myotis myotis, Myotis nattereri and Miniopterus schreibersii); and 5 rodents (Microtus (Iberomys) cabrerae, Microtus (Terricola) duodecimcostatus, Arvicola sapidus, Apodemus sylvaticus and Eliomys quercinus). The presence of these small mammal species indicates that the landscape surrounding the Rock of Gibraltar was predominantly an open habitat, with the presence of woodland and water stream meadows, as well as the presence of larger bodies of water. These results are then compared with pollen and charcoal analysis as well as other faunal proxies, such as the herpetofauna, bird and large mammal assemblages, providing an accurate reconstruction of the climatic and environmental conditions that prevailed during the Late Pleistocene in the southernmost of the Iberian Peninsula.