cDNA nucleotide sequence encoding the ZPC protein of Australian hydromyine rodents: a novel sequence of the putative sperm-combining site within the family Muridae

This comparative study of the cDNA sequence of the zona pellucida C (ZPC) glycoprotein in murid rodents focuses on the nucleotide and amino acid sequence of the putative sperm-combining site. We ask the question: Has divergence evolved in the nucleotide sequence of ZPC in the murid rodents of Australia? Using RT-PCR and (RACE) PCR, the complete cDNA coding region of ZPC in the Australian hydromyine rodents Notomys alexis and Pseudomys australis, and a partial cDNA sequence from a third hydromyine rodent, Hydromys chrysogaster, has been determined. Comparison between the cDNA sequences of the hydromyine rodents reveals that the level of amino acid sequence identity between N. alexis and P. australis is 96%, whereas that between the two species of hydromyine rodents and M. musculus and R. norvegicus is 88% and 87% respectively. Despite being reproductively isolated from each other, the three species of hydromyine rodents have a 100% level of amino acid sequence identity at the putative sperm-combining site. This finding does not support the view that this site is under positive selective pressure. The sequence data obtained in this study may have important conservation implications for the dissemination of immunocontraception directed against M. musculus using ZPC antibodies.     

Comparative studies on the timing of reproduction and foetal number in six species of Australian conilurine rodents (Muridae: Hydromyinae)

The timing of reproduction and number of foetuses in the wild caught conilurine rodents Notomys mitchelli, N. alexis, Pseudomys albocinereus, P. hermannsburgensis, P. delicatulus and P. nanus was ascertained from museum preserved specimens. The two species from southern Australia ( N. mitchelli, P. albocinereus ) appeared to have a breeding season from late winter to early summer, whereas in those from the central region ( N. alexis and P. hermannsburgensis ) no such breeding season was evident. The little data available for the northern species, P. delicatulus , suggests at least reproduction during the winter. Foetal number was similar for the four species from southern and central Australia but tended to be slightly less in the two northern species. The significance of these findings in relation to the control of reproduction is briefly discussed.     

Short- and long-term effects of litter size manipulation in a small wild-derived rodent

Iteroparous organisms maximize their overall fitness by optimizing their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation has however revealed few short-term reproductive adjustments, suggesting that female laboratory rodents express maximal rather than optimal levels of reproductive investment as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole; Microtus arvalis), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups’ energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had long-term consequences, with females that had previously reared an enlarged litter being lighter at the birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimization.     

川西平原大足鼠的种群生态学 III.繁殖

在川西平原利用标志重捕、夹捕解剖和半自然条件下笼养的方法,提供了1989～1995年大足鼠种群雄性和雌性个体处于繁殖状态的比例、胎次数、每胎幼仔数、幼年个体的补充和发育等有关繁殖的基本资料。结果显示,大足鼠极灵活的繁殖策略 提高了这个物种幼年个体的存活,使该物种在可预见而频繁的周期性变化的农田环 境中能够保持相对稳定的种群。大足鼠的繁殖特征主要有：处于繁殖状态的雄性比例较大（平均0.491,95%置信区间0.451和0.534）,怀孕雌性的比例较小（平均0.227,95％置信区间0.213和0.301）,较高和相对稳定的繁殖能力（每年4胎,每胎8.245±0.452只）,雌性幼仔较慢的生长和性成熟（4月）,以及幼年个体加入种群与春季的小麦和秋季的水稻成熟相同步。这些繁殖特征使得大足鼠的繁殖活动集中在有利的时间。结果,虽然伴随繁殖活动雌雄性的个体质量下降,但仍能在短暂的时间里恢复到原来的水平。将大足鼠的胎仔数与一些关于中国啮齿动物繁殖参数地理变异 的研究进行了分析比较,发现后者提供的资料尚不足以支持中国所有啮齿动物都有 "胎仔数随纬度增加"的过分简单的一般结论。每一个物种种群都有自己的最优胎 仔数,但最优胎仔数不一定随纬度而增加。我们认为在大尺度上研究如胎仔数这样的生活史性状时,生活史多样性的提法比单一性状的过分简单的一般化更好。     

Reproduction in female gundis(Rodentia: Ctenodactylidae)

Five species of the Ctenodactylidae have been studied both in the wild and in captivity. Ctenodactylids have vaginal closure membranes, lateral nipples, relatively long oestrous cycles and relatively long gestation periods for small rodents. In these features they resemble the caviomorph rodents of the New World and some of the hystricomorphs of the Old World. Many of the reproductive features such as well-developed young, small litter size, the position of the nipples and the generally low reproductive rate may equally well be attributed to adaptation to a desert rock habitat.     

Reproduction of the least weasel in captivity: basic observations and the influence of food availability

The least weaselMustela nivalis nivalis Linnaeus, 1766 is unique among carnivores because of its small body size and capacity for fast reproduction. It has been suggested to be the main agent for maintaining cyclic fluctuations in northern vole populations, largely based on its high reproductive potential and dependence on small rodents. This study describes basic reproductive data on the least weasel obtained during a captive breeding program. In the experiments, food availability was manipulated at the onset of breeding. Altogether, 65 litters were born during the 5-year study. The mean litter size was 5.1 (in 53 litters of known litter size), the most common litter size being six. The sex ratio of weaned young was not biased from 1∶1. The median date of birth was June 4. Food manipulations did not affect mating frequency suggesting that the observation of failure in breeding in years of low abundance of small mammals is due to mortality of embryos or young before weaning, but not due to avoidance of breeding at low food availability. In this respect, weasels differ from other main vole predators, owls and raptors, which often skip breeding if small mammals are scarce.     

Food limitation in Australian desert rodents: experiments using supplementary feeding

Supplementary feeding experiments were used to directly test the hypotheses that populations of two species of Australian desert rodents ( Pseudomys hermannsburgensis and Notomys alexis ) are food limited. Addition of sunflower seeds to a series of trap plots resulted in an increase in the captures of P. hermannsburgensis . Captures of P. hermannsburgensis were related directly to the amount of supplementary food provided and the amount of food consumed. Supplementary feeding was not, however, able to reverse a population decline, yet it did slow the overall rate of the decline in P. hermannsburgensis . Notomys alexis showed an increase in mean body mass in response to supplementary feeding, but population numbers did not change. Neither species showed a long-term response to the dispersion of supplementary food (clumped vs spread). The combination of pattern analyses and experimental manipulations suggests that the population of P. hermannsburgensis is limited by the availability of food, whereas the population of N. alexis is not. This contrasts with natural patterns of increase, which suggest similar mechanisms are involved in both species, highlighting the need for experimental evidence to support correlative studies.     

Effects of litter accumulation and water table on morphology and productivity of Phragmites australis

Phragmites australis (Common reed) occurs in the interface between water and land. The water depth gradient from deep water to dry land is inversely related to litter accumulation. Eutrophication can result in an excessive production of litter, which may have a large impact on the occurrence of P. australis in this gradient. In an outdoor pot experiment, it was investigated how water tables in combination with substrates containing variable amounts of litter affect morphology and productivity of P. australis. Vegetatively propagated P. australis was grown in pots filled with river sand, litter, and different mixtures of sand and litter (25, 50 and 75% by volume). Four water table treatments were applied; drained (–12 cm), waterlogged (0 cm), flooded (+12 cm), and weekly fluctuating drained and flooded conditions (–12/+12 cm of water relative to substrate level). When drained, no differences between substrate treatments were present. Waterlogging, flooding fluctuating water table treatments caused growth reduction in substrate containing litter. The plants formed short shoots and thin rhizomes. With increasing water table, allocation of dry matter to stems increased at the expense of leaves and rhizomes. At intermediate levels of litter in the substrate, allocation to leaves was lowest. In both instances a lower leaf weight ratio (LWR) was (partly) compensated for by a higher specific leaf area (SLA), resulting in less pronounced differences in leaf area ratio (LAR). Aquatic roots developed when plants were waterlogged or flooded, and increased when litter was present in the substrate. Aquatic roots were formed in the top soil layer when waterlogged. The percentage of aquatic roots increased with increasing amount of litter in the substrate when plants were flooded. It was concluded that the morphological responses of P. australis to litter strongly constrain its ability to maintain itself in deep water when the substrate contains litter. This might one of the explanations for the disappearance of P. australis along the waterward side of littoral zones.     

Discrimination of alternative male phenotypes in Scapanes australis (Boisduval) (Coleoptera: Scarabaeidae: Dynastinae)

Abstract  The palm pest Scapanes australis has been the object of considerable recent research to develop control measures that target male reproductive behaviour. This study investigated horn size scaling relationships and frequency distributions in two subspecies of S. australis for evidence of alternative male reproductive strategies. Indeed, a sigmoidal horn size allometry in both populations was detected as a significant vertical discontinuity by a piece-wise regression model, which indicates that distinct minor and major male phenotypes are expressed in both taxa. A non-linear regression algorithm showed that these subspecies differ significantly in two modelled parameters of horn allometry. A likelihood model was used for probabilistic discrimination of the alternative male phenotypes by estimating their ratios across the bimodal frequency distribution. The latter is intended to aid field investigation of the reproductive biology of S. australis by statistically discriminating the alternative male phenotypes on the basis of easily measured parameters in live samples.     

Factors influencing the postweaning reproductive performance of sows on commercial farms

The objective of this study was to investigate the effects of various factors, including lactational feed intake, on the reproductive performance of sows in commercial herds. The 4 measures of reproductive performance were weaning-to-first-service interval, weaning-to-conception interval, litter weight at weaning, and subsequent litter size. Parity, farrowing season, lactation length, farrowing-to-conception interval, litter size, and lactation feed intake were investigated as risk factors common to the 4 measures of post-weaning reproductive performance. Using 4 basic multiple regression models for each measure, the least-square means for sets of factors were compared using the GLM procedure of SAS. Parity 1 sows had the longest weaning-to-first-service interval and weaning-to-conception interval, and the lighter litter weight at weaning (P < 0.05) than mid-parity sows. Sows in Parities 2 to 5 had larger subsequent litter size (P < 0.05) than those in Parities 1 and >/= 7. Sows farrowing in summer and spring had the longest and second longest weaning-to-conception interval (P < 0.05), respectively, while sows farrowing in summer had longer weaning-to-first-service interval than those that farrowed in spring (P < 0.05). Sows farrowing in summer produced the lightest litter weight at weaning (P < 0.05). No differences in subsequent litter sizes were found due to farrowing season (P > 0.10). As lactation length increased, weaning-to-first-service interval and weaning-to-conception interval decreased, and litter weaning weight increased. Longer lactation length and farrowing-to-conception interval were associated with larger subsequent litter size (P < 0.05). Litter size did not affect weaning-to-first-service interval or weaning-to-conception interval. Larger litter sizes were associated with heavier litter weight at weaning. Greater lactation feed intake improved the 4 measures of reproductive performance.     

No apparent effects of soil inoculum on green frog (Lithobates clamitans Latreille) tadpole performance

Invasions by nonnative plant species are transforming plant communities across the globe. An important challenge for ecologists is to understand how animals will respond to these changes. One way that plant invasions could affect aquatic animals is by changing the rate at which soil communities decompose litter, which could alter the flow of energy and nutrients from plant litter to aquatic communities. In this study, we measured larval amphibian responses to soil conditioned by either introduced or native genotypes of Phragmites australis L. (common reed) in northeastern North America. We collected soil from adjacent stands of introduced and native P. australis at three sites in central New York and inoculated outdoor aquatic mesocosms with soil extracts. Mesocosms contained six Lithobates clamitans Latreille (green frog) tadpoles and either low- or high-quality native P. australis americanus litter. We found that litter decomposition differed based on soil inoculum, and we observed a significant interaction between litter quality and soil inoculum; higher-quality litter tended to decompose faster when exposed to inocula from introduced P. australis, while lower-quality litter tended to decompose faster when exposed to inocula from native P. australis americanus. Tadpoles raised with high-quality litter developed faster and achieved greater body size, but soil inocula had no apparent effect on tadpoles. Our results suggest that plant invasions may alter microbial communities, causing subtle changes in litter decomposition rates, but these changes do not appear strong enough to influence larvae of a widespread amphibian.     

Scale Overlap,a Directional Sign Stimulus for Prey Ingestion by Ophiophagous Snakes1

This paper describes in detail the elements of social behaviour and social organizations of four closely related rodents (Notomys alexis, Pseudomys albocinereus, P. shortridgei and P. desertor) from diverse habitats, and the social organizations of seven other conilurine rodents are described briefly. Most of the data were determined from quantitative observations of animals caged in twos or in larger groups for at least ten days. Breeding pairs were observed daily throughout pregnancy and parenthood. A dispersed organization and three types of communal organization are described, and evolutionary trends in dispersion and territoriality, cohesion, communication and co-operation are discussed.     

The Ontogeny of Social Behaviour in Four Conilurine Rodents (Muridae) of Australia

This paper describes the ontogeny of social behaviour in 4 closely related rodents from diverse habitats. These rodents, Notomys alexis, Pseudomys albocinereus, P. shortridgei and P. desertor exemplify 4 different social organizations. The young were observed daily under semi-natural conditions until weaning, and subsequently at intervals of one week until sexual maturity. Relationships between the young and their families were determined from the relative frequencies of attracting (amicable) and repelling (agonistic) behaviour. The social behaviour of the young is correlated with the social behaviour of adults. Social interactions experienced from birth throughout sub-adulthood appear to prepare these species for their adult social life.     

Structure and changes of macroinvertebrate community colonizing decomposing rhizome litter of common reed at Lake Fertő/Neusiedler See (Hungary)

Hydrobiologia - Rhizome litter of Phragmites australis were enclosed in litter bags of 1 mm mesh size and submerged in a die-back reed stand of Lake Fert?/Neusiedler See (Hungary). Species...     

大仓鼠种群繁殖参数的估算

西文根据大仓鼠自然种群雌体怀胎率,各种类型子宫斑率和幼鼠比率的季节变动规律,估算了1986年河北饶阳县大仓鼠种群的繁殖参数,其研究结果如下：在当年的繁殖季节,大仓鼠越冬雌鼠繁殖3胎次;4、5月份的幼鼠繁殖2胎次;6、7月份的幼鼠繁殖1胎次;9月份左右的幼鼠不参加繁殖。越冬雌鼠春季怀胎和产仔近似正态分布,分布标准差约为13天,平均值为4月20日。幼鼠成熟历期（幼雌体自产出至其产仔）为62天。生殖时滞（雌体两次繁殖间隔）为59天。平均胎仔数为9.1260±2.5971。雌雄性比为1∶1.4926。幼鼠上铗历期为24天。繁殖终止平均日期为9月20日。     

Determinants of reproductive success in voles: space use in relation to food and litter size manipulation

Spacing behaviour of female mammals is suggested to depend on the distribution and abundance of food. In addition, food limitation has been found to constrain the reproductive success of females. However, whether females maximize their reproductive success by adjusting space use in relation to current food availability and reproductive effort (e.g. litter size) has not been experimentally studied. We examined these questions by manipulating simultaneously food resources (control vs. food supplementation) and litter sizes (control vs. plus two pups) of territorial female bank voles (Clethrionomys glareolus) in large outdoor enclosures. Females with supplementary food had smaller home ranges (foraging area) and home range overlaps than control females, whereas litter size manipulation had no effect on space use. In contrast, the size of territory (exclusive area) was not affected by food supplementation or litter size manipulation. As we have previously shown elsewhere, extra food increases the reproductive success of bank vole females in terms of size and proportion of weaned offspring. According to the present data, greater overlap of female home ranges had a negative effect on reproductive success of females, particularly on survival of offspring. We conclude that higher food availability increases the reproductive success of bank vole females, and this effect may be mediated through lower vulnerability of offspring to direct killing and/or detrimental effects from other females in the population. Moreover, it seems that when density of conspecifics is controlled for, home range sizes of females, but not territoriality, is related to food resources in Clethrionomys voles.     

Inheritance of litter size at birth in farmed arctic foxes (Alopex lagopus, Canidae, Carnivora)

Natural populations of the arctic fox (Alopex lagopus, Canidae, Carnivora) differ drastically in their reproductive strategy. Coastal foxes, which depend on stable food resources, produce litters of moderate size. Inland foxes feed on small rodents, whose populations are characterized by cycling fluctuation. In the years with low food supply, inland fox populations have a very low rate of reproduction. In the years with high food supply, they undergo a population explosion. To gain insight into the genetic basis of the reproductive strategy of this species, we performed complex segregation analysis of the litter size in the extended pedigree of the farmed arctic foxes involving 20,665 interrelated animals. Complex segregation analysis was performed using a mixed model assuming that the trait was under control of a major gene and a large number of additive genetic and random factors. To check the significance of any major gene effect, we used Elston-Stewart transmission probability test. Our analysis demonstrated that the inheritance of this trait can be described within the frameworks of a major gene model with recessive control of low litter size. This model was also supported by the pattern of its familial segregation and by comparison of the distributions observed in the population and that expected under our model. We suggest that a system of balanced polymorphism for litter size in the farmed population might have been established in natural populations of arctic foxes as a result of adaptation to the drastic fluctuations in prey availability.     

Pre- and postnatal growth of the Cape porcupine Hystrix africaeaustratis

Pre- and postnatal growth of the Cape porcupine Hystrix africaeaustralis is evaluated by means of the Huggett & Widdas equation, a modification thereof, and the von Bertalanffy equation. Specific foetal growth velocity for the Cape porcupine is higher than that recorded for most other hystricomorph rodents, but similar to that recorded for large-bodied rodents of the same group. Relatively high foetal growth velocity in porcupines is ascribed to their relatively short gestation period, the latter being longer than expected for mammals of equal size, but shorter than expected for a hystricomorph rodent.
Postnatal growth is nearly linear up to the age of 20 weeks and asymptotic body weight is attained at an age of 52 weeks, this coinciding with the observed age at sexual maturity. Growth rates of males and females are similar. Their high rate of postnatal growth and development results in an extended reproductive period, thereby enhancing individual reproductive values by counteracting the effects of seasonal breeding and small litter size.     

Morphological variation in the female reproductive tract of Australian rodents in the genera Pseudomys and Notomys

Morphological studies of the vagina and cervix from females of several species of Pseudomys (pseudo-mice) and Notomys (hopping-mice) have shown marked interspecific differences. In females of all four species of Pseudomys and in N. cervinus there was a relatively thin walled, dorsoventrally flattened, vagina with a large lumen, longitudinal epithelial folds, and conspicuous fornices. By contrast, in females of N. alexis and N. mitchelli the vagina had a much smaller lumen, few or no folds, minute fornices, but a well developed muscle coat. The cervix of the Pseudomys females was a conspicuous fibrous structure, rich in collagen, with two canals throughout its length. In N. cervinus females it was smaller and the two canals, although separated by a median septum for much of their lengths, joined just before the external os. In N. alexis and N. mitchelli females the cervix was much less extensive, its boundaries could not be discerned externally, and, histologically, it was more cellular and less fibrous. This variation in morphology of the female reproductive tract appears to complement that of the excurrent ducts, accessory sex glands and external genitalia of males of these species of Australian murid rodents.     

炔雌醚对布氏田鼠繁殖的抑制效果

明确炔雌醚对鼠类繁殖抑制最适剂量及持续有效作用时间,对其后续相关理论研究和实践应用具有基础性作用。本研究以0.5 mg/kg、1.0mg/kg、2.0mg/kg、3.0mg/kg、6.0mg/kg浓度炔雌醚分别连续灌胃雄性和雌性布氏田鼠7d 后,与正常异性配对观察90ｄ。按繁殖启动期、繁殖率和繁殖力等最直观的指标综合评价了5个浓度炔雌醚对雌雄布氏田鼠的不育效果。室内条件下,炔雌醚能够延迟雌雄布氏田鼠的生殖启动,但可能由于样本量小,未达统计显著性。90ｄ 内,一定浓度的炔雌醚能够降低雌雄个体的繁殖率和平均每窝产仔数,同样未达统计显著性。一些浓度的药物能够显著降低布氏田鼠的繁殖力,其抑制效果无剂量相关性。推断炔雌醚对雄性布氏田鼠的最适不育作用浓度为2.0mg/kg左右,对雌性的最适不育作用浓度为1.0mg/kg左右。实际综合应用剂量2.0mg/kg左右,能有效降低布氏田鼠产仔总数,其持续时间可达90d。