Spatio-temporal variation in the structure of a chromosomal polymorphism zone in the house mouse.

Several long-term temporal analyses of the structure of Robertsonian (Rb) hybrid zones in the western house mouse, Mus musculus domesticus, have been performed. Nevertheless, the detection of gradual or very rapid variations in a zone may be overlooked when the time elapsed between periods of study is too long. The Barcelona chromosomal polymorphism zone of the house mouse covers about 5000, km(2) around the city of Barcelona and is surrounded by 40 chromosome telocentric populations. Seven different metacentrics and mice with diploid numbers between 27 and 40 chromosomes and several fusions in heterozygous state (from one to seven) have been reported. We compare the present (period 2008-2010) and past (period 1996-2000) structure of this zone before examining its dynamics in more detail. Results indicate that there is not a Rb race in this area, which is consistent with the proposal that this zone was probably originated in situ, under a primary intergradation scenario. The lack of individuals with more than five metacentrics in heterozygous state in the current period suggests that selection acted against such mice. By contrast, this situation did not occur for mice with fewer than five fusions in heterozygous condition. Changes in human activity may affect the dynamics of gene flow between subpopulations, thus altering the chromosomal composition of certain sites. Although these local variations may have modified the clinal trend for certain metacentrics, the general staggered structure of the zone has not varied significantly in a decade.

Evolutionary modularity of the mouse mandible: dissecting the effect of chromosomal reorganizations and isolation by distance in a Robertsonian system of Mus musculus domesticus.

The mouse mandible consists of several morphogenetic units that are usually grouped into two main modules: the alveolar region and the ascending ramus. The genetic/ontogenetic modularity of the two regions implies that they might evolve independently to some extent. In particular, evolutionary modularity in quantitative traits could arise during chromosomal speciation due to lower gene flow in rearranged chromosomes. With the aim of uncovering the autonomous evolution of the mandible modules, the form variation of each of them was assessed in the house mouse Robertsonian system from Barcelona, in which chromosomal variation and geographical distance may act as isolation factors. The association between these factors and morphological changes was analysed to determine their contribution to the differentiation of each module. Although size changes in the two modules were highly correlated, shape changes were not, and their association with karyotype differences, but not geographical distance, was dependent on the module. The results support the existence of two evolutionary modules and highlight the importance of size in morphological integration of the mandible. They also suggest that geographical distance and chromosomal reorganizations reduce gene flow between karyotypically divergent populations, but although geographical distance represents a global barrier to gene flow, the isolation produced by a set of chromosomal reorganizations only affects particular modules, probably depending on the number and location of loci with effects on a particular morphological region.

Haematology, genotoxicity, enzymatic activity and histopathology as biomarkers of metal pollution in the shrew Crocidura russula.

Haematological (WBC, RBC, Hgb and Hct) and genotoxicity (MNT) parameters, hepatic enzymatic activities (GST, GPx and GR), and a histopathological evaluation of liver, kidneys and gonads were assessed as general biomarkers of metal pollution in the shrew Crocidura russula inhabiting a pyrite mining area. Specimens exposed to metals presented a few significant alterations when compared with reference animals: GST activity decreased; micronuclei increased; and evident liver alterations related to metal exposure were observed. On the basis of all the parameters studied, age was an important factor that partly explained the observed variation, whereas sex was the least important factor. Significant correlations were also found between heavy metal concentrations and biomarkers evaluated, demonstrating the great influence of these metals in the metabolic alterations. To the best of our knowledge, these data constitute the first measurements of a battery of biomarkers in shrews from a mine site and are among the few available for insectivorous mammals.

Eye morphology in some wild rodents.

The eye anatomy of six rodent species (Murinae: Apodemus sylvaticus, Mus domesticus, and Mus spretus; Arvicolinae: Clethrionomys glareolus, Arvicola terrestris and Microtus arvalis) was compared by means of light or electron microscopy to determine adaptive, and evolutive signals. Our observations revealed inter-specific morphological differences, which were moderate among representatives of the same subfamily. Specifically, traits that distinguished murines from arvicolines were the globe's relative size, the pupillary constrictor muscle, the amount of retinal epithelium melanin, and the thickness of certain ocular coats. Moreover, adaptations to new habitats and differences in temporal activity among species of the same subfamily determined discords respect to the phylogenetic patterns. This was true of the adaptations to underground conditions seen in A. terrestris, which involved the thickness of the cornea, sclera, and choroids. Likewise, A. sylvaticus had adaptations to its nocturnal lifestyle, as shown by the large overall size of the eye and lens, and by a large, thick cornea.

Clinal analysis of a chromosomal hybrid zone in the house mouse.

These studies centre on the 'Barcelona' karyotypic race of the western house mouse (Mus musculus domesticus), first described by Adolph & Klein (1981). This is one of many races within M. m. domesticus characterized by metacentric chromosomes that have originated by repeated Robertsonian fusions, with perhaps further modification by whole-arm reciprocal translocations. Data on 111 mice from 20 sites show that the race is centred 24 km to the west of Barcelona city and has a homozygous metacentric karyotype of 2n = 28 (3.8, 4.14, 5.15, 6.10, 9.11, 12.13). The race has a small range, and mice with the standard 40-acrocentric karyotype were caught only 30 km from the race centre. Throughout the area of occurrence of metacentrics there is polymorphism (i.e. presence of acrocentrics in the population), although all six metacentrics approach fixation close to the race centre. Thus, there is a hybrid zone between the Barcelona and standard races. The centres and widths of all clines (except 3.8) were determined. Likelihood ratio tests showed that most of the cline centres differed significantly in position (i.e. the clines were staggered) and the clines for metacentrics 6.10 and 9.11 were significantly narrower than those for 4.14, 5.15 and 12.13. Overall, the clines tended to be wider the further they were from the race centre. There are various possible explanations for this hybrid zone structure and further data are needed to distinguish between them.

Anatomical study of the abdominal arterial system in soricids (Insectivora, Mammalia): functional and phylogenetic implications.

BACKGROUND: Information on the anatomy of the abdominal arterial system in Insectivora is scarce. We described the origin, distribution, and variations of the visceral abdominal arteries in some Soricidae in order to provide the first comprehensive data on this subject in Insectivora. Results were interpreted from a functional and phylogenetic viewpoint. METHODS: The sample examined consisted of 46 shrews (25 Crocidura russula, 12 Sorex araneus, 5 S. coronatus, 4 S. minutus) captured in the field. Animals were analyzed by injection of coloured latex solution through the left ventricle of the heart and subsequent dissection. RESULTS: The coeliacomesenteric trunk was the first visceral branch of the abdominal aorta. The cranial mesenteric artery supplied those parts of the digestive tract attached to the cranial mesentery and usually gave rise to the colic, the caudal pancreaticoduodenal, and the jejunum-ileumcolic arteries. The coeliac artery mainly vascularized the stomach, the liver and the first portion of the duodenum, and the spleen by means of several branches of the left gastric, the "common" hepatic, and the lienal arteries, respectively. The lienal arteries were double. The renal, gonadal, and median sacral arteries were also branches of the abdominal aorta. The caudal mesenteric artery emerged either from the abdominal aorta or from one of the common iliac arteries. CONCLUSIONS: Differences in the abdominal blood supply between soricids and more advanced mammals are basically focused on the irrigation of the digestive tract. The presence of double lienal arteries and the absence of right gastric artery and left and right gastroepiploic arteries are related to the primitive type of gut presented in the order and are thought to be the plesiomorphic condition in Eutheria.

Arterial vascularization of the abdominal and pelvic regions in the degu, Octodon degus (Rodentia, Octodontidae).

The abdominal and the pelvic arterial supply of the degu, Octodon degus, were described in 19 specimens (10 males and 9 females) from a laboratory strain. Animals were injected through the left ventricle of the heart with coloured latex solution and subsequently dissected under a surgical microscope. The arrangement and variations of the visceral and muscular arteries were described. Comparative analysis among rodents revealed that, even though there was a wide range of interspecific variation in the characters considered, there were several constant anatomical features with phylogenetic value. In this sense, results on the degu and the guinea pig, Cavia porcellus, showed that these hystricognaths share particular features that differentiate them from the sciurognaths analysed to date. The distinguishing characteristics between these two groups of rodents were found in the arrangement of the coeliacomesenteric trunk, and in the cranial abdominal, right gastric, caudal mesenteric, and deep circumflex iliac arteries. The phylogenetic meaning of particular angiological features in rodents were commented.

Blood supply to the abdominal and pelvic regions in the Mediterranean pine vole, Microtus duodecimcostatus (Rodentia, Arvicolidae).

The abdominal and pelvic blood supply of the Mediterranean pine vole (Microtus duodecimcostatus) is described. A total of 13 individuals (seven males, six females) captured in the field (Sanaüja, Spain) were analysed by injection of coloured latex solution and subsequent dissection. The arrangements observed in all specimens show some common traits in relation to the patterns established in other Arvicolidae studied (Arvicola terrestris, Clethrionomys glareolus, Microtus H agrestis). These shared characteristics are centered on the origin of the deep circumflex iliac and the medial femoral circumflex arteries. As a particular variation from other Arvicolidae, some specimens of M. duodecimcostatus exhibit a gastrolienal trunk in the coeliac axis. Furthermore, the origin of the prostatic or the vaginal artery from the pudendoepigastric trunk observed in some specimens of M. duodecimcostatus has not previously been reported in other myomorph rodents.

The arterial system of the abdominal viscera and the pelvis of the dormouse, Eliomys quercinus (Gliridae, Rodentia).

This paper deals with the origin, arrangement and variations of the abdominal and pelvic arteries in the garden dormouse, Eliomys quercinus. Fourteen latex-injected specimens (10 males, 4 females) were analysed by dissection. Measurements from the aortic bifurcation to the origin of the major arterial trunks were taken. The results obtained are compared with those reported for other myomorph rodents. The general arterial system of the dormouse basically agrees with the patterns observed in other rodent species. However, Eliomys quercinus shows some distinguishing features, such as the particular origin of the left and right gastric arteries, the distal arrangement of the deep circumflex iliac arteries, especially the right one, and the source of the medial femoral circumflex artery as a branch of the femoral artery.

The arterial system of the wood mouse, Apodemus sylvaticus: the pelvic region.

In this paper we describe the origin, arrangement and variations of the major pelvic arterial trunks in the wood mouse, Apodemus sylvaticus. Seventy-six specimens have been analyzed by injection of coloured latex solution through the left ventricle of the heart and subsequent dissection of the pelvic region. Measurements of the origin of the major arterial trunks have been performed taking into account the number of anterior and posterior branches arising from its origin. Only the values of the internal iliac artery and the pudendoepigastric trunk show significant differences according to the number of previous branches. In general terms, the pattern of the pelvic arteries in the wood mouse agrees with those reported to for other rodent species. Nevertheless, some differences have been detected, especially in the origin of the major arterial trunks and the constitution of the internal iliac artery.

Arrangement of the branches of the aorta abdominalis in the wood mouse (Apodemus sylvaticus).

Data on the distribution and variation of the abdominal arteries in the wood mouse, Apodemus sylvaticus, are given. Seventy specimens (44 males and 26 females) caught in the field were analyzed by injection of green latex solution and dissection. The general branching pattern of the aorta abdominalis is similar to those described in other rodents. There are certain differences, however, especially in the branching of the coeliac trunk, the origin of the genital arteries and the arrangement of the caudal mesenteric artery. Significant variability was detected in the distribution of the iliolumbar arteries about the testicular and ovaric arteries. Based on the observations and measurements carried out, some branching patterns of the aorta abdominalis are presented.