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PubMed2006

The evolutionary radiation of Arvicolinae rodents (voles and lemmings): relative contribution of nuclear and mitochondrial DNA phylogenies.

BACKGROUND: Mitochondrial and nuclear genes have generally been employed for different purposes in molecular systematics, the former to resolve relationships within recently evolved groups and the latter to investigate phylogenies at a deeper level. In the case of rapid and recent evolutionary radiations, mitochondrial genes like cytochrome b (CYB) are often inefficient for resolving phylogenetic relationships. One of the best examples is illustrated by Arvicolinae rodents (Rodentia; Muridae), the most impressive mammalian radiation of the Northern Hemisphere which produced voles, lemmings and muskrats. Here, we compare the relative contribution of a nuclear marker--the exon 10 of the growth hormone receptor (GHR) gene--to the one of the mitochondrial CYB for inferring phylogenetic relationships among the major lineages of arvicoline rodents. RESULTS: The analysis of GHR sequences improves the overall resolution of the Arvicolinae phylogeny. Our results show that the Caucasian long-clawed vole (Prometheomys schaposnikowi) is one of the basalmost arvicolines, and confirm that true lemmings (Lemmus) and collared lemmings (Dicrostonyx) are not closely related as suggested by morphology. Red-backed voles (Myodini) are found as the sister-group of a clade encompassing water vole (Arvicola), snow vole (Chionomys), and meadow voles (Microtus and allies). Within the latter, no support is recovered for the generic recognition of Blanfordimys, Lasiopodomys, Neodon, and Phaiomys as suggested by morphology. Comparisons of parameter estimates for branch lengths, base composition, among sites rate heterogeneity, and GTR relative substitution rates indicate that CYB sequences consistently exhibit more heterogeneity among codon positions than GHR. By analyzing the contribution of each codon position to node resolution, we show that the apparent higher efficiency of GHR is due to their third positions. Although we focus on speciation events spanning the last 10 million years (Myr), CYB sequences display highly saturated codon positions contrary to the nuclear exon. Lastly, variable length bootstrap predicts a significant increase in resolution of arvicoline phylogeny through the sequencing of nuclear data in an order of magnitude three to five times greater than the size of GHR exon 10. CONCLUSION: Our survey provides a first resolved gene tree for Arvicolinae. The comparison of CYB and GHR phylogenetic efficiency supports recent assertions that nuclear genes are useful for resolving relationships of recently evolved animals. The superiority of nuclear exons may reside both in (i) less heterogeneity among sites, and (ii) the presence of highly informative sites in third codon positions, that evolve rapidly enough to accumulate synapomorphies, but slow enough to avoid substitutional saturation.

Animals↗
PubMed1987

Species-specific processing of prodynorphin in the posterior pituitary of mammals.

The steady state levels of the prodynorphin-derived opioid peptides, dynorphin A, dynorphin B, and alpha-neo-endorphin, have been extensively studied in the magnocellular/posterior pituitary system of the rat. To determine whether the rat system serves as a general model for prodynorphin processing in the mammalian posterior pituitary, we examined the steady state levels of prodynorphin-derived opioid peptides in the posterior pituitary systems of representatives of three diverse orders of mammals: guinea pig (order Rodentia), pig (order Artiodactyla), and rhesus monkey (order Primates). In each species studied there was evidence for species-specific deviations from the rat model. The most pronounced differences were observed with respect to the conversion of dynorphin A-(1-17) to dynorphin A-(1-8). In rodents, rats, and guinea pigs, under steady state conditions, the molar ratios of these forms are approximately 1:2 and 2.5:1, respectively. However, in the pig and rhesus monkey, the molar ratios of these forms are 10:1 and 14:1, respectively. Thus, under steady state conditions, the conversion of dynorphin A-(1-17) to dynorphin A-(1-8) appears to be a minor event in porcine and rhesus monkey posterior pituitary. Species-specific variations were also observed with respect to the steady state levels of alpha-neo-endorphin and dynorphin B-(1-13). In addition, the results of these studies suggest that the conversion of prodynorphin-derived opioids to leu-enkephalin probably represents a minor event in the species studied.

Animals↗
PubMed2005

Evidence for the use of reflected self-generated seismic waves for spatial orientation in a blind subterranean mammal.

Subterranean mammals like the blind mole-rat (Rodentia: Spalax ehrenbergi) are functionally blind and possess poor auditory sensitivity, limited to low-frequency sounds. Nevertheless, the mole-rat demonstrates extremely efficient ability to orient spatially. A previous field study has revealed that the mole-rat can assess the location, size and density of an underground obstacle, and accordingly excavates the most efficient bypass tunnel to detour around the obstacles. In the present study we used a multidisciplinary approach to examine the possibility that the mole-rat estimates the location and physical properties of underground obstacles using reflected self-generated seismic waves (seismic 'echolocation'). Our field observations revealed that all the monitored mole-rats produced low-frequency seismic waves (250-300 Hz) at intervals of 8+/-5 s (range: 1-13 s) between head drums while digging a bypass to detour an obstacle. Using a computerized simulation model we demonstrated that it is possible for the mole-rat to determine its distance from an obstacle boundary (open ditch or stone) by evaluating the amplitude (intensity) of the seismic wave reflected back to it from the obstacle interface. By evaluating the polarity of the reflected wave the mole-rat could distinguish between air space and solid obstacles. Further, the model showed that the diffracted waves from the obstacle's corners could give the mole-rat precise information on the obstacle size and its relative spatial position. In a behavioural experiment using a special T-maze setup, we tested whether the mole-rat can perceive seismic waves through the somatosensory system and localize the source. The results revealed that the mole-rat is able to detect low frequency seismic waves using only its paws, and in most cases the mole-rats determined accurately the direction of the vibratory source. In a histological examination of the glabrous skin of the mole-rat's paws we identified lamellate corpuscle mechanoreceptors that might be used to detect low frequency seismic waves. The combined findings from these different approaches lead us to suggest that a specialized seismic 'echolocation' system could be used by subterranean mammals to determine the most energy-conserving strategy with which to bypass an obstacle, as well as to estimate their distance from the surface, keeping their tunnels at the optimal depth.

Adaptation, Physiological↗
PubMed2002

Torque patterns of the limbs of small therian mammals during locomotion on flat ground.

In three species of small therian mammals (Scandentia: Tupaia glis, Rodentia: Galea musteloides and Lagomorpha: Ochotona rufescens) the net joint forces and torques acting during stance phase in the four kinematically relevant joints of the forelimbs (scapular pivot, shoulder joint, elbow joint, wrist joint) and the hindlimbs (hip joint, knee joint, ankle joint, intratarsal joint) were determined by inverse dynamic analysis. Kinematics were measured by cineradiography (150 frames s(-1)). Synchronously ground reaction forces were acquired by forceplates. Morphometry of the extremities was performed by a scanning method using structured illumination. The vector sum of ground reaction forces and weight accounts for most of the joint force vector. Inertial effects can be neglected since errors of net joint forces amount at most to 10 %. The general time course of joint torques is comparable for all species in all joints of the forelimb and in the ankle joint. Torques in the intratarsal joints differ between tailed and tail-less species. The torque patterns in the knee and hip joint are unique to each species. For the first time torque patterns are described completely for the forelimb including the scapula as the dominant propulsive segment. The results are compared with the few torque data available for various joints of cats (Felis catus), dogs (Canis lupus f. familiaris), goats (Capra sp.) and horses (Equus przewalskii f. caballus).

Animals↗
PubMed1997

Effect of ovariectomy in the early first half of the diestrus on induction or maintenance of canine deciduoma.

The effect of ovariectomy in the early first half of the diestrus was examined on the induction or maintenance of suture-induced canine deciduoma. Ovariectomy immediately, or some days, after the insertion of suture had no effect on the induction or maintenance of deciduoma. Even when ovariectomy was performed within 4 days before insertion, deciduoma could be induced in spite of there being no ovary. However, when ovariectomy was done 4 or more days before suture insertion, the rate of deciduoma was decreased or no deciduoma was induced. These results indicate that the influence of the ovary on the endometrium may persist for at least 4 days after ovariectomy. Ovariectomy after the suture insertion had few effects. It is suggested that canine uterine glands in the early first half of the diestrus maintain a certain degree of self-proliferative ability even after ovariectomy, and thus canine deciduoma is not as dependent on the ovary that of the rodentia.

Animals↗
PubMed2006

Proliferation and apoptosis in early molar morphogenesis-- voles as models in odontogenesis.

Proliferation and apoptosis play crucial roles in the development of multicellular organisms. Their precise balance is necessary for tissue homeostasis throughout life. The developing dentition is a suitable model to study proliferation and apoptosis during embryogenesis, but the corresponding studies have been carried out principally in the mouse. The present study aimed to examine proliferation and apoptosis in the vole (Microtus sp., Rodentia) during the early morphogenesis of the first upper molar and compare it to what is known from the mouse. To this end, apoptosis and proliferation were investigated using histology and computer-aided 3D reconstruction. Mitoses accumulated predominantly in the developing cervical loop. Apoptosis during early odontogenesis showed highly specific spatio-temporal patterns in the dental epithelium. Apoptotic bodies were localised in non-dividing cell populations. They accumulated in the same places as described in the mouse: antemolar vestiges (ED 12.5 15.5), enamel knot (ED 14.5 15.5), stalk and palatally along the whole first molar tooth germ longitudinal axis (ED 15 - 15.5). Early tooth development in the field vole, including the distribution of apoptosis and mitosis, is very similar to that reported in the mouse, with the exception of the antemolar region. The microtine antemolar vestige is preserved longer than the murine one. It is conceivable that additional distinct differences in morphogenetic processes appear later in tooth development.

Animals↗
PubMed2000

Eimeria burdai sp. n. (Apicomplexa: Eimeriidae), a new parasite species from subterranean African silvery mole-rat, Heliophobius argenteocinereus.

A new coccidian parasite of the genus Eimeria Schneider, 1875 is described from the subterranean African silvery mole-rat Heliophobius argenteocinereus Peters, 1846. Oocysts of Eimeria burdai sp. n. were subspherical to broadly ellipsoidal 17.8 (16-19) x 14.1 (12-15), with a shape index 1.2 (1.1-1.4). Oocyst wall was bilayered, smooth and colourless, approximately 1.0 thick. Outer layer was significantly thicker than inner one. A micropyle and oocyst residuum were absent. One or two ellipsoidal or spherical polar granules were present. Sporocysts were ellipsoidal, 10.8 (9-12) x 6.2 (5-8) with a shape index 1.7 (1.5-1.9). Sporocyst wall was single-layered, thin, smooth and colourless, with small Stieda body at the pointed end. In freshly sporulated oocysts, spherical sporocyst residuum was composed of small granules enclosed by a thin membrane. Sporozoites were elongate, lying length-wise in the long axis of the sporocyst, partially curled around each other, with single large refractile body located posteriorly. Faintly distinguishable nucleus was in the central part of the sporozoite. This eimerian represents the first coccidian species described from subterranean African silvery mole-rat (Rodentia: Bathyergidae).

Africa↗
PubMed2003

Correlation between DNA synthesis in the second, third and fourth generations of spermatogonia and the occurrence of apoptosis in both spermatogonia and spermatocytes.

In the seminiferous epithelium, both DNA synthesis and apoptosis occur at equivalent stages in various species, with apoptosis taking place mainly at the same stages as DNA replication in the second, third and fourth spermatogonial generations. As preservation of the cellular associations found at these stages may have some functional significance, it is important to determine whether there is a correlation between these cellular events. In this study, pairs of immunoperoxidase-stained adjacent testis sections from rats, mice, rabbits and cats in which either bromodeoxyuridine incorporated into the newly synthesized DNA strand (BrdU labelling) or DNA 3' end labelling of the apoptotic DNA fragments (TUNEL assay) were detected were compared. In addition, both events were analysed in double-labelled sections. These two methods revealed a clear correlation between the occurrence of DNA replication in the second to fourth generations of spermatogonia and most physiological apoptosis taking place in both spermatogonia and spermatocytes in the three different mammalian orders (Rodentia, Lagomorpha and Carnivora). This correlation may result from the synchronization of mitotic spermatogonial and meiotic spermatocyte cell cycle checkpoints operating at these stages.

Animals↗
PubMed1980

[A morphological study on the early fertilized ova in rat--with special reference to the temporal changes of zona pellucida and implantatin process of blastocyst (author's transl)].

It has already been reported that the zona pellucida in the rodentia plays an important role in the mechanism of preventing polyspermatozoan fertilization. The implantation of the blastocyst is known to begin after the zona pellucida is taken off from the surface. The authors carried out a scanning electron microscopical observation on temporal changes in the zona pellucida after mating. After fertilization, a clear spongy structure having a double or triple construction was formed on the zonal surface. The structure was distinguishable until 2.5 days after mating, when it developed into the 2-cell stage. After that it became indistinct and thinned increasingly as the ovum grew further. When the blastocyst was formed completely 4.5 days after mating, the zonal surface was hatched. It is assumed that the existence of active zonal reaction may physiologically convert almost all the zona pellucida as a fine spongy structure. In the present research obsrvation was made on the implantation process and the implantation chamber with a scanning electron microscope. On the early morning of 5.5 days after mating, the blastocyst tended to adhere to the implantation chamber which had been formed previously in the endometrium by the secretion of mucoidal substances. After that, implantation proceeded. On the evening of 5.5 days after mating, however the implantation of blastocyst onto the endometrium progressed with interdigitation by microvilli.

Animals↗
PubMedDate not supplied

Schistosoma mansoni Sambon, 1907: comparative morphological studies of some Brazilian strains.

The morphology of Schistosoma mansoni adult male worms from three strains which have been maintained in albino mice for several generations, was compared to a strain that has been isolated from the natural host Nectomys squamipes (Rodentia:Muridae) captured in Sumidouro (Rio de Janeiro State) and have been maintained in the same sylvatic rodent under laboratory conditions. Total length of specimens, distance between suckers, the number of testes and extention of testes grouping were the taxonomic characters analysed. The worms recovered from N. squamipes showed expressive differences (p < 0.01) compared to the other strains regarding the considered morphological characters. The strains that were maintained in mice presented statistical differences (p < 0.01) in several characters. Some adult worms besides the normal position of the testes also showed an atypical arrangement of these glands. It can be concluded that the morphology of adult worms may be used to distinguish S. mansoni strains and that morphological changes in adult worms are not induced by successive inoculations of a strain in mice.

Animals↗
PubMed2004

Pattern of elevational distribution and richness of non volant mammals in Itatiaia National Park and its surroundings, in southeastern Brazil.

Itatiaia National Park (PNI) and its surroundings present a unique fauna due to different forest formations with well-defined climatic and vegetation bands. The Itatiaia massif has four vegetation types that follow an altitudinal gradient: lower montane forest, montane forest, upper montane forest, and Campos de Altitude. Hence, this region is ideal for studying geographical variation in biological diversity. The main objectives of this study were to report on nonvolant mammal species known to occur in Itatiaia National Park and its surroundings and to determine if their distributional pattern is related to elevation. A review of the literature and a complete survey of specimens deposited in museums, as well as small-mammal trapping were carried out in order to obtain a complete record of the species from the region. Precise locality data were obtained for all specimens recorded, allowing the inclusion of each collected or observed individual in an altitude and vegetational class. We made a direct ordination gradient of marsupial, primate, and rodent species abundance with the altitude. Sixty-nine mammal species were collected or reported for the Itatiaia massif, belonging to seven orders and 20 families. Of these, 33 species (47.8%) are included in the official list of threatened or believed-to-be threatened species in Rio de Janeiro State. The orders Rodentia, Carnivora, and Didelphimorphia had the highest species richness, with 25, 14, and 13 species respectively. When species were grouped according to the vegetation, 16 species occured in the lower montane, 56 in the montane forest, five in the upper montane, and 21 in the high-altitude fields (Campos de Altitude). The communities of marsupials, primates, and rodents have an ordination pattern related to the altitude. Species richness was higher between 500 m and 1,500 m above sea level in montane forest, which is in agreement with recent studies showing that species richness can reach its maximum at mid-elevations.

Altitude↗
PubMed2000

A survey of hemoparasite infections in free-ranging mammals and reptiles in French Guiana.

Blood smears of 1,353 free-ranging mammals (35 species) and 112 reptiles (31 species) from French Guiana were examined for hemoparasites. Parasites from 3 major groups were recorded: Apicomplexa (including hemogregarines, piroplasms, and Plasmodium spp.), Trypanosomatidae, and Filaroidea. Fifty percent of the individuals (86% of the species) were infected by parasites from at least 1 group. Hemogregarines, identified as Hepatozoon sp., infected numerous snakes with high prevalences (30-100%); infection is reported for the first time in 5 host genera of snakes: Clelia, Oxybelis, Pseustes, Rhinobotryum, and Bothriopsis. Infections were also observed in 4 marsupial species and 1 rodent. Hepatozoon spp. recorded in Didelphis albiventris (Marsupialia) and Coendou prehensilis (Rodentia) may be new species. Plasmodium sp. were observed in 2 snake species, Dipsas indica (Colubridae) and Bothrops atrox (Viperidae). Plasmodium brasilianum was recorded in all 5 primate species examined. Piroplasms were observed in all mammal orders except primates. Large terrestrial rodents were the main hosts of members of the Babesidae; 42% of Myoprocta acouchy, 36% of Dasyprocta agouti, and 44% of Agouti paca were infected. Trypanosomes were common in mammals and were recorded in 70% of the examined genera. Trypanosoma cruzi-like infections were reported in 21 mammal species, including sloths, rodents, carnivores, and primates. Microfilariae were also widespread, with higher prevalences in sloths, anteaters, and porcupines (>40% of the individuals infected) and in tamarins (95% infected). This survey highlights some potential anthropozoonotic risks due to the recent further evidence of Plasmodium brasilianum and P. malariae as a single species and to the increased diversity of hosts for Trypanosoma cruzi.

Animals↗
PubMed2001

Hoplopleura janzeni n. sp. (Phthiraptera: Anoplura), a new sucking louse from a Central American swimming mouse.

Both sexes of a new species of sucking louse Hoplopleura janzeni (Phthiraptera: Hoplopleuridae) are described and illustrated from the Central American ichthyomyine swimming mouse Rheomys raptor (Rodentia: Muridae) collected in Costa Rica. The morphology of the new species is compared with that of Hoplopleura exima Johnson, the only other species of sucking louse known to parasitize an ichthyomyine rodent. Hoplopleura janzeni is unique in having posteriorly directed spurs on the first antennal segment, the fore- and midcoxae, and the hind femora of both sexes.

Animals↗
PubMed2003

A new genus of Nippostrongylinae (Nematoda: Heligmonellidae) from the water rat Scapteromys aquaticus (Sigmodontinae) in Argentina.

A new genus of Nippostrongylinae, Malvinema n. gen., with 3 coparasitic species M. frederici n. sp., M. carolinae n. sp., and M. victoriae n. sp. from the intestine of the water rat, Scapteromys aquaticus Thomas (Rodentia: Muridae), from the northeast of Buenos Aires Province, Argentina, is proposed in this study. The new genus shows similarities to 2 Neotropical Nippostrongylinae: Carolinensis (Travassos, 1937) by some characters of the synlophe and Stilestrongylus Freitas, Lent and Almeida, 1937, by the pattern of the caudal bursa. It is characterized by a synlophe with triple or quadruple gradient of size of the ridges, lateromedian, decreasing from the largest left and right ridges. The gradient situated in the right ventral quadrant is always present. The caudal bursa shows a pattern of type 1-4. Malvinema frederici possesses a synlophe with 17 ridges and an axis of orientation inclined at 45 degrees from the sagittal axis; M. carolinae possesses a synlophe with 22-24 ridges and an axis of orientation almost merged with the sagittal axis. Both species have a caudal bursa with the right lobe enlarged transversally. Malvinema victoriae possesses a synlophe with 22-24 ridges, an axis of orientation inclined at 45 degrees from the sagittal axis, and a caudal bursa with the right lobe enlarged vertically.

Animals↗
PubMed2006

A new species of Trichuris (Nematoda: Trichuridae) from Phyllotini rodents in Argentina.

A new species of Trichuris is described. Trichuris pardinasi n. sp. was recovered from Phyllotis xanthopygus Waterhouse (Rodentia: Muridae: Phyllotini) in Sierra de la Ventana, Buenos Aires Province, and Pampa de Achala, Córdoba Province (Argentina). This is the first record of Trichuris parasitizing Phyllotini rodents. The new species can be differentiated from the other 10 species parasitizing rodents from South America by the absence of the spicular tube, spicular sheath with spines uniformly distributed, the length of spicule, the J-shaped proximal cloacal tube, and the nonprotrusive vulva. Also, a description of the bacillary band is provided. The present and the future findings of shared parasite fauna from both populations of P. xanthopygus in these disjunct areas will support the hypothesis of a continuous distribution of this host species at a past time.

Animals↗
PubMed1993

Characterization of rabbit kappa-casein cDNA: control of kappa-casein gene expression in vivo and in vitro.

The rabbit kappa-casein cDNA was cloned and sequenced. One of the isolated clones included almost the entire 5' end, while another clone corresponded to the 3' end of the cDNA. No polyadenylation site was found and therefore this clone did not harbour the complete cDNA. The amino acid sequence of a full-length protein was deduced from the nucleotide sequence obtained for this partial cDNA. It revealed the presence of a chymosin cleavage site and five potential phosphorylation sites. Rabbit kappa-casein was compared with those already described in other species. The rabbit sequence is closer to the ovine than to the mouse sequence. This result supports the idea that Lagomorpha are not closer to Rodentia than to Artiodactyla. The cDNA described above was used to study kappa-casein gene expression in the rabbit mammary gland. This expression was induced primarily by prolactin in mammary gland organoids and was similar to alpha s1-casein gene expression in vivo. The kappa-casein gene present in the casein gene locus is thus subject to the same regulation as the alpha s1-casein gene, although it has evolved from a fibrinogen gene.

Amino Acid Sequence↗
PubMed1998

Phylogenetic positions of insectivora in eutheria inferred from mitochondrial cytochrome c oxidase subunit II gene.

For the elucidation of the phylogenetic position of insectivora in eutheria, we have sequenced the cytochrome c oxidase subunit II (COII) gene of mitochondria for three insectivoran species [musk screw (Suncus murinus), shrew mole (Urotrichus talpoides), Japanese mole (Mogera wogura)] and analyzed these amino acid sequences with neighbor-joining (NJ) method and maximum likelihood (ML) method. NJ analysis shows polyphyly of Insectivora and Chiroptera. Assuming that each of Primates, Ferungulata, Chiroptera, Insectivora and Rodentia is a monophyletic group, ML analysis suggests that Chiroptera is a sister group of Insectivora and that Ferungulata is the closest outgroup to the (Insectivora and Chiroptera) clade.

Animals↗
PubMed1996

Characterization of Oliveros virus, a new member of the Tacaribe complex (Arenaviridae: Arenavirus).

Oliveros virus is an agent isolated in cell culture from Bolomys obscurus (Rodentia, Muridae, Sigmodontinae) captured on the central Argentine pampa. Oliveros virus was shown to be related to members of the Tacaribe complex of the family Arenaviridae by immunofluorescent antibody (IFA) tests, electrophoretic pattern of viral proteins, and morphology as observed by electron microscopy. It was distinct from 12 other arenaviruses by a combination of plaque-reduction neutralization tests, comparison of endpoint titers among cross-IFA tests, and comparison of viral RNA sequence data. This agent is the third new arenavirus from South America described within the last three years.

Animals↗