布氏田鼠标志种群的繁殖参数

采用标志重捕和染色观测法跟踪了内蒙古典型草原区布氏田鼠野外种群,按绝对时间年龄研究其种群繁殖参数。结果3表明：4－5月份出生的雄鼠能在当年达到性成熟,性成熟发育历期约为1．5个月,6月后出生的雄鼠当年达不到性成熟。在达到性成熟的当年雄鼠中,多数个体再度转入性休止期,其平均繁殖结束时间要林越冬雄鼠早1个月,而越冬雄鼠则在整个繁殖期保持性活动状态。雌鼠性成熟发育历期约为1个月,首次产仔时间约为2月龄。雌鼠在一年中的产仔窝数与其年龄有关;越冬鼠能产3－4窝,4月份出生的雌鼠能产2－3窝,5月份出生的雌鼠当年能产1－2窝,6月份出生的雌鼠能产0－1窝,7月份之后出生雌鼠当年不参加繁殖,在自然条件下,布氏田鼠一年中最多能产4窝。     

长爪沙鼠种群繁殖的季节性特征

长爪沙鼠是分布于我国北方典型和荒漠草原及农牧交错区的优势鼠种之一。2000 年10 月至2004 年10 月通过标志重捕法研究了栖息于内蒙古农牧交错区草地生境的种群动态。对其不同季节出生群性成熟特征和种群性成熟比率、繁殖个体比例、个体月补充率等繁殖参数的季节特征研究显示:冬季和春季出生的个体性成熟较夏季出生的个体快,尤雌鼠表现突出,其3 个季节出生群的性成熟时间分别为4. 6 ± 0.2、4. 4 ± 0.8 和7.7 ± 0.4月龄。种群性成熟比率、繁殖个体比例和个体补充率月间差异显著,季节消长明显,即春季最高,秋季(9 ～10月间)最低。结果还显示,种群性成熟比率与气温和降水负相关。长爪沙鼠喜栖于植被稀疏、低矮的干燥沙质土壤环境。从初春到夏末,随降水和气温增加其栖息生境的植被由低矮稀疏变得高而稠密,土壤湿度和粘性亦随之提高,地面种子库因发芽贮量减少,适宜生境的减少可能加剧了社群竞争,抑制了种群的繁殖表现。长爪沙鼠种群繁殖的季节变化反映了其生活史对策中适应高纬度气候和食物的季节波动的重要特征。     

大沙鼠种群空间分布格局的研究

大沙鼠“家族”式的生活方式导致其种群聚集分布格局,且季节差异不显著。每一“家族”占据单一洞群,这些“家族”间在其最适生境内呈明显的均匀分布格局。雄鼠之间为争夺雌鼠在繁殖初期排斥性增强,末期关系趋于缓和。雌鼠对雄鼠的吸引力在整个繁殖期表现强烈,二者呈聚集分布,越冬时则显示扩散趋势;雄鼠的空间格局受雌鼠分布的影响;雌鼠之间为争夺生存空间以利于其繁殖呈强烈的均匀分布格局。     

布氏田鼠标志种群的社群等级及其季节变化

在内蒙古锡林郭勒地区,通过标志重捕、染色标记和直接观测法对布氏田鼠社群等级的季节变化进行了研究。结果表明:在繁殖季节,布氏田鼠洞群内存在明显的社群等级。越冬雄鼠在社群内社群序位最高,其次是越冬雌鼠、当年成体雌鼠、当年成体雄鼠,亚成体鼠和幼鼠的社群地位最低。在繁殖末期,越冬雄鼠的地位明显下降,而当年成体雄鼠的等级序位逐渐上升。在繁殖季节,当年雄鼠在洞群中的等级序位依然很低,很少能有机会进行有效的交配,有效交配主要由越冬雄鼠来完成,因而越冬雄鼠对种群繁殖的贡献较大。本实验倾向于支持该鼠的婚配制度为一雄多雌制的观点。     

长爪沙鼠体质量生长模式特征

通过Gompertz方程拟合分析了野外围栏条件下当年春季出生的长爪沙鼠(Merioties unguiculatus)体质量生长模式.结果表明:雌、雄鼠体质量生长系数相近,该结果支持生长系数具有种的特异性,反映物种固有特征的结论;但雄鼠的当年稳定体质量和体质量日瞬时增长率高于雌鼠,雄鼠的体质量增长的拐点时间、生长速率降低到起始值的时间以及达到稳定体质量90%的时间均较雌鼠的晚,这些指标呈现的性别差异提示了长爪沙鼠婚配策略中的多配倾向.     

高原鼠兔种群繁殖生态的研究

1985—1988年,在青海湖黑马河地区以耳标法对高原鼠兔的繁殖生态进行了研究。在繁殖群体中主要是来自上年出生的第1、2胎的鼠兔(82.85％),第3胎和老体占少数。成年雌鼠兔100％参加繁殖,通常年产3胎,有的年份可产4胎或5胎。产仔数1—8只(平均为4.52±0.12),1只雌鼠兔终生可产2—29只。妊娠期为22.2±0.13天。洞内哺乳期为11.65±0.01天。有的年份当年出生的少数雌鼠兔到36.8+3.05日龄可达到性成熟并参加繁殖,生1—2胎。雄鼠兔性成熟较晚。     

高原鼠兔种群敏殖生态的研究

1985-1988年,在青海湖黑马河地区以耳标法对高原鼠兔的繁殖生态进行了研究。在繁殖群体中主要是来自上年出生的第1、2胎的鼠兔（82.85%）,第3胎和老体占少数。成年雌鼠兔100%参加繁殖,通常年产3胎,有的年份可产4胎或5胎。产仔数1-8只（平均为4.52±0.12）,1只雌鼠兔终生可产2-29只。妊娠期为22.2±0.13天。洞内哺乳期为11.65±0.01天。有的年份当年出生的少数雌鼠兔到36.8±3.05日龄可达到性成熟并参加繁殖,生1-2胎,雄鼠兔性成熟较晚。     

粪便激素水平反映不同出生时期雄性布氏田鼠的繁殖策略

布氏田鼠是我国内蒙古草原的主要害鼠之一,具有明显的季节繁殖特征,不同季节出生个体可能具有不同的繁殖策略,但尚缺乏内分泌证据支持。本研究采用标志重捕法,连续监测大型自然围栏中不同年龄雄性布氏田鼠的繁殖状态和应激水平的季节变化,分析各年龄组雄鼠的繁殖发育策略。结果表明,越冬雄鼠可保持较高的睾丸下降率和睾酮水平至8月初;而部分5月生雄鼠的繁殖期睾酮水平较接近越冬鼠,但8月初已降至年内最低水平,而6月及以后出生雄鼠睾酮始终处于较低水平;这说明越冬鼠的繁殖状态可贯穿繁殖期始终,只有部分5月生雄鼠可能参与当年繁殖,而6月及以后出生雄鼠则不能在当年繁殖。越冬鼠皮质醇水平高于当年鼠,繁殖期高于非繁殖期,这可能是越冬鼠由于繁殖需要而保持较高应激状态,从而造成繁殖盛期后死亡率升高。这些结果说明,不同时期出生的雄性布氏田鼠具有不同的出生后性腺发育模式和繁殖策略,反映出生存与繁殖之间的权衡。     

长爪沙鼠生长繁殖性能的研究

目的　动物的生长繁殖性能是其生理学数据的重要组成部分 ,对实验动物的开发和应用具有指导意义。方法　选择离乳的长爪沙鼠 80只 (雌雄各半 ) ,一雌一雄长期同居。结果　每胎产仔 3～ 7只的居多 ,占总胎数的 77% ;平均每胎产仔 (5 .0 2± 2 .1 1 )只 ;每年产仔胎数 5～ 9胎的较多 ,占总胎数的 91 .7% ,平均 (7.4 9± 2 .0 1 )胎 /年 ;最早的初产周龄为 1 3周龄 ,最长的 5 2周龄 ,在 1 3～ 2 0和 2 5～ 2 8周龄的居多 ,占总对数的 80 %。长爪沙鼠的平均出生重为 3.5g ,成年鼠平均体重雌性 5 5 .6g ,雄性 6 7.2g。结论　普通级长爪沙鼠封闭群配种日龄最早在 6 5日龄 ,初产日龄超过 2 0 0日龄的长爪沙鼠应淘汰 ;性别对长爪沙鼠体重无显著影响     

不同生活史阶段长爪沙鼠尿标记行为的遗传和空间距离效应

气味标记普遍存在于哺乳动物类群中,它能向同类传达领地占有、社会等级及繁殖状态等多种信息。2014年4月至10月,我们在内蒙古锡林郭勒正蓝旗对长爪沙鼠 (Meriones unguiculatus) 野外种群进行了标志重捕,采用中立场的方式测定了不同社群间同性别长爪沙鼠的尿标记行为。通过建立洞群样地坐标后用勾股弦方法计算群间距离,并用微卫星DNA分子标记估算个体间的亲缘系数,以探讨野生动物标记行为是否受个体间空间和遗传距离的影响。广义线性混合效应分析显示,雄鼠间的尿标记强度在繁殖期和贮食期受空间距离或遗传距离的影响均不显著。繁殖期雌鼠间的尿标记强度受空间或遗传距离的影响亦不明显,但在贮食期,遗传距离对雌鼠间标记的强度有显著影响,且遗传距离与空间距离对标记强度有明显的交互作用。本研究结果暗示亲缘关系和空间距离对长爪沙鼠的尿标记行为具有一定影响,这与长爪沙鼠的繁殖或贮食行为相适应。     

Reproductive life history correlates of early and late sexual maturation in female Mongolian gerbils (Meriones unguiculatus)

Age at vaginal introitus is bimodally distributed in female domesticated Mongolian gerbils; some exhibit vaginal perforation before eye-opening (day 16), others after weaning (day 25). We found early- and late-maturing female gerbils to differ significantly in reproductive life history. Early-maturing females first reproduced when younger, had more litters, with more young per litter, and consequently had more than twice as many offspring as late-maturing females. In comparison with late-maturing females, early-maturing females gave birth to and weaned a greater proportion of females per litter and a higher proportion of early-maturing daughters per litter. Further, early-maturing females exhibited reduced maternal behaviour; they spent less time nursing their young and retrieved fewer offspring displaced from the nest than late-maturing females. Even under constant laboratory conditions, there were significant, correlated, circannual rhythms in female fecundity, the proportion of males per litter and the proportion of early-maturing daughters per litter. Review of the field literature suggests that wild Mongolian gerbils may exhibit similar variability in reproductive pattern.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured by age 1⁺, and all the females matured by age 2⁺. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season. The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them. After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year, and moderate growth rates after maturity.     

Lifespan ontogeny of breeding and reproductive success in Mongolian gerbils

An analysis was made of demographic data collected from a colony of Mongolian gerbils (Meriones unguiculatus). The data on births of over 3800 gerbils provide evidence on several aspects of development and fecundity. Approximately 4% more females than males survived to weaning. Mean number of pups per dam per year was estimated to be 48.3, greater reproductive success than reported previously. The shortest period of gestation resulting in viable pups was 25 days. Implantation was delayed by the presence of suckling pups. When gestation was prolonged, there was a direct relationship between the number of pups being suckled concurrently and the length of the delay. Length of gestation did not affect the size of the subsequent litter. Female gerbils gave birth as early as 72 days of age. Gerbils continued to reproduce until after 2 years of age in some cases. There were fewer pups per litter born to older females, fewer pups per litter with increasing parity, and longer intervals between litters with increasing age.     

Age-related changes on marking, marking-like behavior and the scent gland in adult Mongolian gerbils (Meriones unguiculatus).

Marking behavior, marking-like behavior [3], and changes of the scent glands were observed in aged Mongolian gerbils. In Experiment 1, changes in the marking and marking-like behavior with aging were evaluated in adult male and female Mongolian gerbils of an inbred strain aged 6 to 36 months. The frequency of marking behavior in males was significantly higher than females throughout the observation period except at 36 months of age. On the other hand, frequency of marking-like behavior in males, but not in females decreased with aging, significantly. In Experiment 2, changes of the scent gland in adult males and females aged 6 to 36 months were morphologically evaluated. Macroscopic examination revealed an increase in the size length and width of the glands of males aged 12 months and females aged 6 months. Histologically the glands of all the males and females aged 6 months developed moderately or well. Some of the 12-month-old males and females showed acinar atrophy of the glands, and all the females aged 18 months or more had highly atrophied scent glands. From these results, we concluded that there is no relationship between the changes of marking behavior and those of the scent glands in aged male Mongolian gerbils, and assume that marking behavior in aged animals does not have an important meaning as marking. In Experiment 3, marking and marking-like behavior in castrated adult Mongolian gerbils aged 16 weeks were observed. The result showed that marking behavior, not marking-like behavior was inhibited after castration. From these findings, we consider that generally marking behavior in Mongolian gerbils consists of androgen-dependent marking behavior and androgen-independent marking behavior (marking-like behavior).     

Social influence on sexual maturation and breeding in the female Mongolian gerbil (Meriones unguiculatus)

Social factors influencing reproductive activity in laboratory groups of gerbils were investigated using the ventral scent-gland as an index of reproductive condition. Sexual maturation and breeding were suppressed in female offspring remaining with their parents. In family groups living in enclosures, daughters rarely bred in the presence of their mother but breeding activity increased after death. Intra-female aggression resulted in the re-establishment of a single breeding female in groups where more than one started to breed. In a controlled social situation in which females were caged with their mothers, sexual maturation was suppressed in the presence of their mother and the continuing presence of her second litter, but not in the presence of a non-pregnant mother or a mother whose second litter had been removed.     

Reproductive biology and implications for management of the orange-spotted grouper Epinephelus coioides in the southern Arabian Gulf

The reproductive biology of Epinephelus coioides was determined from the examination of 1455 individuals collected between July 2005 and June 2007 in the southern Arabian Gulf. Histological preparations of gonads indicated that males were either derived from a juvenile phase or the transition of postspawning females, confirming a diandric protogynous sexual pattern. The spawning season was well defined, occurring once a year during April and early May. Peaks in spawning occurred after the full and new moons and was completed within a single lunar cycle. The presence of mature males over the entire size and age range and the absence of inactive mature females during the spawning season suggested that the population was not constrained by sperm limitation. While specimens undergoing sexual transition were only observed in size and age ranges of 335–685 mm total length ( L _T) and 5–6 years, patterns in the proportion of males in size and age classes suggested that sex change occurred at a relatively constant rate after female maturation up to the maximum size (1002 mm L _T) and age (11 years). Relationships between reproductive output and capacity with size and age indicated that conventional regulations that equate the mean size at first capture to sexual maturation are unsuitable for the management of E. coioides . The maximum age, small size and young age at sexual maturation ( L _min= 320 mm L _T, 2 years, for females and 242 mm L _T, 1 year, for males) conflict with the general pattern for large epinepheline groupers and may be a direct result of the intensive demersal fishery in the southern Arabian Gulf.