Convergent evolution of aquatic foraging in a new genus and species (Rodentia: Muridae) from Sulawesi Island, Indonesia.

The island of Sulawesi, in Indonesia, lies at the crossroads of the Indo-Australian Archipelago and has remained isolated from the Asian (Sunda) and Australian (Sahul) continental shelves for at least the last 10 million years. Of the 50 native species of rodents on Sulawesi, all are endemic and represent the evolution of a variety of ecological and morphological forms within the Muridae and Sciuridae. Carnivorous rodents have evolved, perhaps independently, in Muridae from the Philippines, Sulawesi, and Sahul, but semi-aquatic murids are only known from Sahul. Here we describe a new genus and species of insectivorous water rat from Sulawesi. Phylogenetic analyses demonstrate that it is related to the shrew rats of Sulawesi and represents an origin of aquatic carnivory that is independent from the evolution of water rats on Sahul. Many areas of Sulawesi have not been surveyed systematically and current lists of mammal species are likely to dramatically underestimate actual diversity.

Morphometric analysis of the placenta in the New World mouse Necromys lasiurus (Rodentia, Cricetidae): a comparison of placental development in cricetids and murids.

BACKGROUND: Stereology is an established method to extrapolate three-dimensional quantities from two-dimensional images. It was applied to placentation in the mouse, but not yet for other rodents. Herein, we provide the first study on quantitative placental development in a sigmodontine rodent species with relatively similar gestational time. Placental structure was also compared to the mouse, in order to evaluate similarities and differences in developmental patterns at the end of gestation. METHODS: Fetal and placental tissues of Necromys lasiurus were collected and weighed at 3 different stages of gestation (early, mid and late gestation) for placental stereology. The total and relative volumes of placenta and of its main layers were investigated. Volume fractions of labyrinth components were quantified by the One Stop method in 31 placentae collected from different individuals, using the Mercator software. Data generated at the end of gestation from N. lasiurus placentae were compared to those of Mus musculus domesticus obtained at the same stage. RESULTS: A significant increase in the total absolute volumes of the placenta and its main layers occurred from early to mid-gestation, followed by a reduction near term, with the labyrinth layer becoming the most prominent area. Moreover, at the end of gestation, the total volume of the mouse placenta was significantly increased compared to that of N. lasiurus although the proportions of the labyrinth layer and junctional zones were similar. Analysis of the volume fractions of the components in the labyrinth indicated a significant increase in fetal vessels and sinusoidal giant cells, a decrease in labyrinthine trophoblast whereas the proportion of maternal blood space remained stable in the course of gestation. On the other hand, in the mouse, volume fractions of fetal vessels and sinusoidal giant cells decreased whereas the volume fraction of labyrinthine trophoblast increased compared to N. lasiurus placenta. CONCLUSIONS: Placental development differed between N. lasiurus and M. musculus domesticus. In particular, the low placental efficiency in N. lasiurus seemed to induce morphological optimization of fetomaternal exchanges. In conclusion, despite similar structural aspects of placentation in these species, the quantitative dynamics showed important differences.

Non-target organism effects tests on Vip3A and their application to the ecological risk assessment for cultivation of MIR162 maize.

Transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt) provide economic, environmental and health benefits by maintaining or increasing crop yields with fewer applications of insecticide. To sustain these benefits, it is important to delay the evolution of insect resistance to the proteins, and to ensure that the proteins do not harm non-target organisms, particularly those that may control secondary pests that would otherwise flourish because of reduced insecticide applications. Vip3A is a Bt vegetative insecticidal protein that is active against lepidopterous pests. It has a different mode of action from other proteins for control of Lepidoptera in current Bt crops, and when combined with these proteins, it should help to delay the evolution of pest resistance to Bt crops. This paper presents data on the effects of Vip3A on non-target organisms, and an ecological risk assessment of MIR162 maize, which expresses Vip3Aa20. Laboratory studies indicate few adverse effects of Vip3A to non-target organisms: 11 of 12 species tested showed no adverse effects when exposed to high concentrations of Vip3A relative to estimated exposures resulting from cultivation of MIR162 maize. Daphnia magna exposed to Vip3Aa20 were unaffected in terms of survival or fecundity, but grew slightly more slowly than unexposed controls. The data indicate that cultivation of MIR162 maize poses negligible risk to non-target organisms, and that crops producing Vip3A are unlikely to adversely affect biological control organisms such that benefits from reduced insecticide applications are lost.

[The adaptive strategy of rodent populations living in conditions of radioactive and chemical environmental pollution].

The comparative analysis of demographic, morphological and physiological processes in mouselike rodents in pollution zones (90Sr + 90Y, 137Cs) on East-Ural radioactive track (EURT) and (Cu + Cd + Pb + Zn + SO2) on a site near copper-smelting factory is carried out. The direct (not mediated) defeat of animals by an irradiation leads to inherited adaptation (density preservation, tolerance increase to pollution, migration decrease and so forth). The mediated defeat of animals at pollution by metals influences animals as a result of degradation of a vegetative cover, reducing a forage reserve, shelters and reproduction places. Population is decreasing, migration is increasing. Hence, population reacts onto direct defeat of animals or on inhabitancy locuses degradation, id est unspecifically, without dependence from the physical and chemical nature of pollution.

[The metabolic homeostasis of the small mammals in the conditions of the East Ural radioactive trace].

The difference in the mechanism of radioresistance, the strategy and the level of the adaptation are determined at Apodemus (Sylvaemus) Uralensis and Clethrionomys Rutilus living on the territory of the East Urals Radioactive Trace with the 90Sr contamination density of 180-450 Ci/km2. The mechanism of radioresistance Apodemus (Sylvaemus) Uralensis is based on the use of lipid reserves in energy provision of the physiological functions, what provided of the growth oxidation metabolism in the mitochondria. Found changes testify in favor of stress-realization mechanism of increase of the level energy homeostasis and, inquest, heightened regime of the functioning cells. As a result there is the cellular disadaptation, marked of decrease nuclear, mitochondrial proteins and process of the cellular regeneration, that put obstacles in tissue adaptation. The opposite focus of the metabolic homeostasis at Clethrionomys Rutilus points to limitation use of the lipid reserves in energy provision of the physiological functions, what provided the suppression oxidation metabolism in the mitochondria. The minimization of the functional activity cellular and subcellular structures compensate the growth of theirs numbers as a result of the level tissue and longtime adaptation. This fact characterizes more safety of the level adaptability at Clethrionomys Rutilus to radiation surroundings.

[An input of heterochronies to the formation of interspecific differences in wood mice, Sylvaemus (Rodentia)].

Difference in adult size and body shape among the closely related species is the result of diversification in morphogenetic processes. We examined age variation in various external and craniometric characters of four Sylvaemus species from Ukrane fauna, S. uralensis, S. arianus, S. sylvaticus, and S. tauricus, using cross-sectional techniques. The intensive growth period occurred to be different in various species. Rapid growth of S. tauricus continues during all life span, while in other species growth rate becomes slower at different stages. This peculiarity of S. tauricus may be the result of prolonged and more intensive production of somatotropin by adenohypophysis. Side effects of adenohypophysis activation are resulted from changes in S. tauricus skull shape and more intensive pigmentation in comparison with three other species. Prolongation of growth could be developmental mechanism for size increasing in evolution of S. tauricus. The independence of body size and pigmentation is principally the same at interspecific and intraspecific level.

Climate change and size evolution in an island rodent species: new perspectives on the island rule.

As stated by the island rule, small mammals evolve toward gigantism on islands. In addition they are known to evolve faster than their mainland counterparts. Body size in island mammals may also be influenced by geographical climatic gradients or climatic change through time. We tested the relative effects of climate change and isolation on the size of the Japanese rodent Apodemus speciosus and calculated evolutionary rates of body size change since the last glacial maximum (LGM). Currently A. speciosus populations conform both to Bergmann's rule, with an increase in body size with latitude, and to the island rule, with larger body sizes on small islands. We also found that fossil representatives of A. speciosus are larger than their extant relatives. Our estimated evolutionary rates since the LGM show that body size evolution on the smaller islands has been less than half as rapid as on Honshu, the mainland-type large island of Japan. We conclude that island populations exhibit larger body sizes today not because they have evolved toward gigantism, but because their evolution toward a smaller size, due to climate warming since the LGM, has been decelerated by the island effect. These combined results suggest that evolution in Quaternary island small mammals may not have been as fast as expected by the island effect because of the counteracting effect of climate change during this period.

A comparative study of myelination in precocial and altricial murid rodents.

The development of myelin staining was compared in two closely related rodent species, the precocial Acomys cahirinus and altricial Rattus norvegicus. While the progression of myelin staining was similar in both species (motor tracts myelinated before sensory systems, which were followed by forebrain fiber systems), the timing of maturation differed considerably: (1) at the same postconception age (PC38) Rattus was substantially more mature than Acomys, suggesting a relatively earlier onset of myelination in Rattus; although (2) from PC38-PC45, Acomys exhibited much more rapid growth than Rattus, indicating divergence in the rate of myelination. Both species appeared to reach maturity at a common postconception age corresponding to the time of weaning (PC45).

A stereological study of neocortical maturation in the precocial mouse, Acomys cahirinus.

The development of neocortical area 17 of Acomys cahirinus was studied by quantifying changes in the numerical density of neurons and glia, and by examinations of subjects treated on the day of birth with tritiated thymidine. Unlike most laboratory species, Acomys is born in a relatively advanced state, with open and functional ears and eyes and coordinated locomotor abilities. Rapid neocortical growth occurred during the first 60 postnatal days and was accompanied by a 65% decrease in neuronal packing density. No evidence of neuronal proliferation was found in the neocortex, although labelling was found in the dentate gyrus and olfactory bulb. Glial densities remained relatively constant through the same time period, a consequence of continued proliferation. While previous studies have demonstrated that Acomys and the laboratory mouse undergo quite different patterns of olfactory bulb and hippocampal formation growth, the present study indicates that patterns of neocortical maturation are very similar in the two species. These findings suggest large variations both within and between species in patterns of brain growth.

Postnatal maturation of brain cholinergic systems in the precocial murid Acomys cahirinus: comparison with the altricial rat.

The spiny mouse (Acomys cahirinus) is the only precocial murid species. It has some neuroanatomical peculiarities such as a relatively thin cerebral cortex and a large hippocampus. The levels of choline acetyltransferase, membrane-bound acetylcholinesterase and muscarinic receptor sites (measured as [3H]quinuclidynil benzilate binding) were assessed in the whole brain on days 1, 7, 14, 21, 28 and 80 (adult), and compared with those of Wistar rats of the corresponding ages. At birth choline acetyltransferase was significantly higher in spiny mice than in rats but the adult levels were similar, with an overall increase of about 5.2- and 14-fold for the former and the latter species, respectively. Membrane-bound acetylcholinesterase level and maximal density of muscarinic receptor sites in spiny mice were considerably higher at birth, in contrast adult levels were significantly lower than in rats with a respective overall increase of about 1.5- and over 4.5-fold. The high degree of maturity attained at birth by spiny mice partially depends on the long gestation period. However, if we consider postconception age, the maturation of choline acetyltransferase appears to be delayed at birth in the spiny mice, probably in relation to the lack of external stimulation during intrauterine life. In the cerebral cortex, hippocampus and striatum of adult spiny mice, when compared with the rats, there were similar levels of choline acetyltransferase but lower levels of membrane-bound acetylcholinesterase and, in the cerebral cortex, lower density of muscarinic receptor sites.

Evolution of biological effects of Aznalcóllar mining spill in the Algerian mouse (Mus spretus) using biochemical biomarkers.

The status of Guadiamar stream, polluted in 1998 by metals spilled from a pyrite tailings dam, was monitored from 1999 to 2001 to assess possible biological effects in terrestrial ecosystems of Doñana National Park (DNP) (Andalusia, SW Spain). The Algerian mouse (Mus spretus) was used as bioindicator at different Guadiamar and Doñana sites. Eleven biochemical parameters, including the activities of antioxidative and biotransforming enzymes and oxidative damages to biomolecules, were assayed in liver as biomarkers responsive to metals and organic pollutants. In 2001, metals were also determined in kidney and their possible correlation with biomarker responses was studied. Contents of Pb, Cd and As significantly correlated with several antioxidative enzymes. Biomarkers responsive to oxidative stress indicate the presence of transition metals in the high and medium Guadiamar course, and their response diminished with the distance to the collapsed dam. The high ethoxyresorufin-O-deethylase (EROD) activity of mice from the medium and low Guadiamar course point to organic pollutants, such as the pesticides used in intensive crops grown in areas nearby Doñana. The increasing responses of several biomarkers at reference sites may suggest a progressive pollution of key Doñana ecosystems.

Sexual dimorphism and seasonal variation in submandibular gland histology of Bolomys lasiurus (Rodentia, Muridae).

Wild rodents (Bolomys lasiurus) of both sexes were caught in a cerrado grassland area during the dry (July-September) and rainy (January-March) seasons of Brazil. Fasted animals were perfused with Karnovsky fixative through the left ventricle, under ether anesthesia, and the submandibular gland was processed for embedding in historesin. Histological and histometric data show sexual dimorphism at both seasons. In the volume percentage of the granular convoluted tubules (GCT) and their secretory granules, the males exhibited higher values. The absolute volume occupied by these structures, however, was dimorphic only in the rainy season. The diameter of the GCT, the height of its epithelium, and its total length were also greater in males during the rainy season. The absolute volumes of the acini and of the ductal tree were identical in both sexes in the dry and rainy seasons but the acinar diameter increased in the males and females during the rainy season. The sexual dimorphism and the seasonal variations now described in the B. lasiurus submandibular glands could be explained by the augmented reproductive activity of the males in the rainy period.

The structure of the spiny mouse (Acomys cahirinus) ovary during development.

The study presents the structure of the ovaries of the spiny mouse (Acomys cahirinus) during the first months of life. The ovaries in neonate females exhibit a large number of primordial and primary follicles, sometimes clustered in nests. The growing follicles were also observed within the ovary at that period. The first, early antral follicles appeared in the ovary during the second week of life. In the group of 60-day old females, the structure of the ovaries was characterized by a significant increase in the connective tissue elements. Moreover, ovarian follicles at various stages of development were observed, except for the antral ones with cumulus oophorus. The first mature follicles were identified in 3-month old females. In the ovarian follicles, apoptosis occurs at all stages of follicle development, especially in the early antral follicles. In the atretic follicles, apoptotic cells were identified in the layer of granulosa cells.

The relation of growth performance to dietary oil source in African giant rat (Cricetomys gambianus Waterhouse).

An experiment is described in which palm-oil, groundnut oil, cottonseed oil and soybean oil were each fed as a 5% dietary supplement to the African giant rat (AGR). 4 AGR were fed each diet from 6-12 weeks of age. The groundnut oil-based diet supported the best liveweight gain of 4.23 g/day, while AGR fed the cottonseed oil diet lost an average weight of 1.42 g/day during the 6-week study. The efficiency of feed utilization was similar for AGR fed on palm-oil and soybean oil diets, but this was significantly (P less than 0.05) better than the 3.24 g feed/g gain obtained for AGR fed on groundnut oil diet. There was an abnormally low feed intake by AGR fed the cottonseed oil diet, and this probably resulted in their poorest performance. In terms of feed conversion efficiency, the results suggest that either palm-oil or soybean oil can be used in the diet of AGR. This observation is not in line with the practice whereby groundnut oil was used in the diet of albino rat.

Assessing the effect of litter size on growth pattern and homeothermy acquisition in the Pampas mice Akodon azarae (Rodentia, Muridae).

We evaluated in pups of Akodon azarae both the growth pattern from birth to 48 days of age and the effect of litter size on growth pattern and homeothermy acquisition from birth to weaning age. Individual pups gained weight as expected by a Gompertz growth pattern. Until weaning, litter size affected both the slope of the relationship between body temperature and age and the rate of growth of pups. Pups from small litters increased both body temperature and weight until body temperature and body weight of adults at higher rates than those from large litters.

[Species-specific odor in closely related species: period of development in ontogenesis of house (Mus musculus musculus) and mound-building (Mus spicilegus) mice]. / Vidospetsificheskii zapakh u blizkorodstvennykh vidov: vremia formirovaniia v ontogeneze u domovykh (Mus musculus musculus) i kurganchikovykh (Mus spicilegus) myshei.

In two-choice odor tests, it was shown that house and mound-building mice began to discriminate the species-specific odor of young at the age of 17 days. The mice investigated the odor of conspecific urine significantly longer than that of heterospecific urine, when the young donors of urine, were 17 days old or older. Thus, the species-specific odor appears in ontogenesis of these species on the 17th day of life.

[A morphometric study of postnatal synaptogenesis in the neocortex of precocial and altricial rodents]. / Morfometricheskoe issledovanie postnatal'nogo sinaptogeneza v neokortekse zrelo- i nezrelorozhdaiushchikhsia gryzunov.

Quantitative electronmicroscopic studies have been made on the development of synapses in two modally different areas of the brain (V-VI layers of the visual and auditory cortex) in the rat and mouse Acomys cahirinus within first two weeks of their postnatal life. The density of synapses as well the relative amount of different types of synapses (symmetrical, asymmetrical, axo-spinal and synapses with large amounts of synaptic vesicles) were measured. It was shown that only in rats the development of synapses in the visual area usually is faster than in the auditory one.

[Dynamic model of seasonal breeding rodent pest population controlled with short-acting sterilant].

Rodent pests bring great damage to human beings, while rodenticide and sterilant can be used to control the pests. After ingesting sterilant, rodent pests lose their fertility, but in some cases, the sterile individuals may gain their fertility again, produce offspring, and enlarge population size. In this paper, the dynamic models of rodent pest population under lethal control and shortacting contraception control were formulated, and, with the prerequisite of the seasonal breeding of rodent pest population, the models were used to regularly analyze their behaviors and the effects of the contraception rate, lethal rate, control interval, and sterilant valid period on the dynamics of the pest population. The results showed that larger contraception rate and lethal rate and shorter control interval could have better control effect, making the controlled population become smaller and even died out. Short-acting sterilant limited the control effect. At the later period of breeding season, the rodent pest population controlled with short-acting sterilant would have a weak recovery.