雌二醇对动物子代性比的影响

控制家畜性比的实验报道很多,但是用特定的化学试剂来稳定控制家畜子代性比的研究却很少.因此开展这项试验研究并将研究成果加以推广,将会给我国畜牧业生产带来巨大的经济效益.     

亲体状态对子代性比的影响

<正> 动物的性别控制是一个具有重大意义而又富有吸引力的课题.在哺乳动物中,人们一直在致力于x精子和y精子的分离,以期获得“性别精液”来实现对哺乳动物性别的控制.从Lush(1925)首次用超速离心机分离精子到Pinkcl等(1985)首次用流式细胞仪分离精子~2的几十年间,人们尝试了分离精子的多     

蜜蜂性比的研究

蜜蜂性比是指一群蜂内雌性蜂与雄性蜂的比例。本文应用 Fisher 性比法则,来研究蜜蜂性比问题,结果如下:(1)在交尾季节,由于雄蜂的有效交配日龄 N=12～35天,则工蜂所“希望”的理论比值 Hw=(1.41N+4.53)∶1=(21.5～53.9)∶1,Hw 值与实际性比值((?)=26.1∶1)相符;(2)在非交尾季节,蜂群内只有雌性蜂。以上结果,从理论和实践相结合的角度,证实了蜂群内的性比值是由工蜂决定。     

蜜蜂性比的分子调控机制研究

蜜蜂性比是指蜂群中雌性蜜蜂与雄性蜜蜂的比例。按亲属选择理论和性比原理预测 ,工蜂则可能对雌性性别更多地投资 ,这样蜂王和工蜂在决定性比问题上存在矛盾。本试验通过RAPD技术测定蜂王交配次数 ,并利用亲属选择和性比理论 ,研究了蜂群中的性比冲突问题。研究结果支持了工蜂调控蜜蜂性比的观点。     

不同授精时间对仔猪性比影响的研究

有研究报道认为，在母牛排卵前授精易得雌性后代，在接近排卵时授精易得雄性后代，在授精当时预测的犊牛性别与实产犊牛性别的符合率达到约７０％。为了检验这一现象是否也存在于猪的繁殖活动，特别安排在同一发情母猪的排卵前和后，分别用不同毛色的公猪配种，观察在不同排卵期授精是否也影响仔猪的性比。为了探讨不同排卵期授精当时的内分泌活动，在二次配种当时分别在尾动脉采血，测定血清中雌二醇和促黄体素含量。２２窝母猪的试验结果表明，排卵前授精得母仔５５．６％（６９／１２４），排卵后授精得公仔５７．３％（７５／１２４），Ｐ＜０．０５。其中有１窝只在排卵前授精（母仔占６９．２％，９／１３）和５窝只在排卵后授精（公仔占６７．４％，２９／４３），更加显著地（Ｐ＜０．０２５）表现出对仔猪性比的影响。激素测定表明，排卵前授精时血清中雌二醇和促黄体素水平分别比排卵后授精高２．３和６．３倍，对测定结果的进一步分析表明，母猪在授精当时血清中雌二醇含量较高时，后代母仔的比例较高。     

蜜蜂性比的生理生化调控机制研究

试验研究了不同季节不同蜂群子脾间温度、湿度和CO2体积分数等巢内环境因素变化规律,同时测定不同状况不同蜂群中不同日龄工蜂保幼激素酯酶的活性及血淋巴中K+/Na+变化。结果表明,巢内CO2体积分数和湿度环境因素改变,引起群内15—20日龄工蜂保幼激素含量提高和血淋巴中K+/Na+降低,从而使蜂群表现出调控蜜蜂性比行为。     

精氨酸对科尔沁黄牛后代性比的影响

用精氨酸处理发情母牛，经人工授精后统计后代牛犊的性比。结果发现：处理母牛的尿液pH值降低，怀孕率降低，空怀率升高，牛犊中母犊达70．27％。这结果说明精氨酸可提高黄牛的X型精子的受精率。     

二型花柱植物红蓼的繁殖生物学研究

本研究发现了红蓼的异型花柱现象,红蓼野外居群存在长柱型花和短柱型花。研究表明长/短柱花型具有精确的交互式异位特征,其花大小,柱头形态,乳突大小,花粉粒数目、大小都表现出两型性(P<0.01)。与长柱型花相比,短柱型花较大,有短且排列紧密的柱头乳突细胞,花药产生较少且大的花粉。长/短柱型花花瓣长度无显著差异(P>0.01)。扫描电镜显示两型花的花粉均具有散孔,孔近似圆形,边缘形状不规则。野外调查发现蓟马、蚂蚁、食蚜蝇为主要访花者。人工授粉,红蓼长/短柱型花自交、型内异交以及型间异交花粉管均萌发,0.5 h花粉管已萌发至子房,只有部分花粉管能萌发至子房且沿花柱壁及子房壁生长,说明其受精方式为合点受精。长/短柱型花型内异交座果率分别为14.00%和13.33%,自交座果率分别为4.62%和2.86%,型间异交的座果率分别为43.33%和44.61%,表明红蓼长/短柱型花自交表现出一定的亲和性,但座果率低,仍以异交为主。     

Existing theories do not explain sex ratio variation at birth in monomorphic roe deer (Capreolus capreolus)

The phenomenon of skewed sex ratios at birth has been reported in many ungulate species. So far, no consistent trend has emerged for roe deer (Capreolus capreolus), because male‐biased, female‐biased and equal sex ratios at birth have all been found. Nevertheless, both the Trivers‐Willard hypothesis and the theory of local resource competition have gained support. Despite the great number of studies carried out regarding the ecology of roe deer, too many aspects remain unclear, and contradictory results have been produced with respect to several crucial elements. Without further research, the discussion on which theory applies will therefore remain inconclusive. We put forward the argument that eventually the theories of Trivers‐Willard and local resource competition can be considered as being not essentially different. After all, both theories explain the observed skewed sex ratios as being due to the effect of the progeny's sex on the mother's body condition and hence her reproductive success in subsequent years. Furthermore, neither theory is likely to prove to be suitable for roe deer, as several assumptions are unlikely to be met. In roe deer, skewed ratios probably only have a temporal character. As a matter of fact, several observations of skewed sex ratios in birds and mammals did not withstand the accumulation of further data, as sex ratios that were initially believed to be biased turned out to be equal in the long term. This is likely to be the case in roe deer as well. We hypothesize that roe deer, as r‐strategists, will produce as many offspring as possible, regardless of sex.     

Latitudinal gradients in body size and sexual size dimorphism in fleas: males drive Bergmann's pattern

We tested for the effects of latitude and geographic range size (GRS) on body size, leg length, and sexual size dimorphism (SSD) across 103 species of fleas, taking into account phylogenetic between-species relationships. When the data on body size were combined for males and females, the positive correlation between body size and latitude, but not GRS, was revealed. When the analysis was restricted to one sex only, the effect of latitude appeared to be non-significant for females, whereas male body size increased with an increase in latitude. Intraspecific body size variation was not associated with either the latitude or the latitudinal span of the geographic range, independently of which data subset was analyzed. No evidence of association between size-independent tibia length and latitude was found for either females, males, or both sexes combined. The degree of SSD decreased with a decrease in latitude but was not affected by GRS. We conclude that macroecological patterns might be manifested differently in males and females. This should be kept in mind while searching for these patterns.     

Identification of genomic regions that exhibit sexual dimorphism for size and muscularity in cattle

Sexual dimorphism, the phenomenon whereby males and females of the same species are distinctive in some aspect of appearance or size, has previously been documented in cattle for traits such as growth rate and carcass merit using a quantitative genetics approach. No previous study in cattle has attempted to document sexual dimorphism at a genome level; therefore, the objective of the present study was to determine whether genomic regions associated with size and muscularity in cattle exhibited signs of sexual dimorphism. Analyses were undertaken on 10 linear-type traits that describe the muscular and skeletal characteristics of both males and females of five beef cattle breeds: 1,444 Angus (AA), 6,433 Charolais (CH), 1,129 Hereford, 8,745 Limousin (LM), and 1,698 Simmental. Genome-wide association analyses were undertaken using imputed whole-genome sequence data for each sex separately by breed. For each single-nucleotide polymorphism (SNP) that was segregating in both sexes, the difference between the allele substitution effect sizes for each sex, in each breed separately, was calculated. Suggestively (P ≤ 1 × 10⁻⁵) sexually dimorphic SNPs that were segregating in both males and females were detected for all traits in all breeds, although the location of these SNPs differed by both trait and breed. Significantly (P ≤ 1 × 10⁻⁸) dimorphic SNPs were detected in just three traits in the AA, seven traits in the CH, and three traits in the LM. The vast majority of all segregating autosomal SNPs (86% in AA to 94% in LM) had the same minor allele in both males and females. Differences (P ≤ 0.05) in allele frequencies between the sexes were observed for between 36% (LM) and 66% (AA) of the total autosomal SNPs that were segregating in both sexes. Dimorphic SNPs were located within a number of genes related to muscularity and/or size including the NAB1, COL5A2, and IWS1 genes on BTA2 that are located close to, and thought to be co-inherited with, the MSTN gene. Overall, sexual dimorphism exists in cattle at the genome level, but it is not consistent by either trait or breed.     

Sexual size dimorphism in the lizard Oplurus cuvieri cuvieri (Squamata,Opluridae) from Madagascar

Sexual size dimorphism in the medium-sized lizard Oplurus cuvieri cuvieri, which is endemic to the dry deciduous forest of Madagascar, is presented. Adults are sexually dimorphic in body size, head size, and tail length. Males have a greater snout–vent length (SVL), head depth, head width, jaw length, tail length and body mass than females. Juvenile males have greater annual SVL growth rates than juvenile females, contributing to adult sexual size dimorphism. Moreover, the rates of increase in head depth and width differ significantly between the sexes after reaching maturity so that adult males have larger heads for a given body size than adult females. I suggest three proximate mechanisms that may cause sex-related differences in adult head size of O. c. cuvieri based on natural selection; to reduce intersexual food competition, sexual selection involving mate acquisition in males, and ontogenetic change of allometry to improve reproductive output in females.     

Sex ratio variation and sex determination in the mallee dragon Ctenophorus fordi

Recent evidence suggests that many Australian agamids show temperature‐dependent sex determination (TSD) with variation in sex determining mechanisms among closely related taxa. However, as shown in other vertebrates, sex ratios can also be influenced by genetic or phenotypic differences among females in their propensity to produce sons or daughters, and these influences might confound any thermal effects of incubation per se. To address these issues, we investigated the determinants of sex ratios in the mallee dragon Ctenophorus fordi, together with a detailed analysis of karyotypes. There was no detectable variation in sex ratios arising from variation among females, clutches or incubation temperatures, which might indicate genetic sex determination for this species. However, there was no evidence of cytologically distinct sex chromosomes using standard banding techniques. The sex ratio pattern in C. fordi strongly contrasts with the results for the congener Ctenophorus pictus, where sex ratios show variation among females. Thus, Australian agamids offer promising opportunities to address fundamental issues in sex ratio biology.     

Multivariate analysis of sexual size dimorphism in local turkeys (Meleagris gallopavo) in Nigeria

Sexual size dimorphism is a key evolutionary feature that can lead to important biological insights. To improve methods of sexing live birds in the field, we assessed sexual size dimorphism in Nigerian local turkeys (Meleagris gallopavo) using multivariate techniques. Measurements were taken on 125 twenty-week-old birds reared under the intensive management system. The body parameters measured were body weight, body length, breast girth, thigh length, shank length, keel length, wing length and wing span. Univariate analysis revealed that toms (males) had significantly (P < 0.05) higher mean values than hens (females) in all the measured traits. Positive phenotypic correlations between body weight and body measurements ranged from 0.445 to 0.821 in toms and 0.053–0.660 in hens, respectively. Three principal components (PC1, PC2 and PC3) were extracted in toms, each accounting for 63.70%, 19.42% and 5.72% of the total variance, respectively. However, four principal components (PC1, PC2, PC3 and PC4) were extracted in hens, which explained 54.03%, 15.29%, 11.68% and 6.95%, respectively of the generalised variance. A stepwise discriminant function analysis of the eight morphological traits indicated that body weight, body length, tail length and wing span were the most discriminating variables in separating the sexes. The single discriminant function obtained was able to correctly classify 100% of the birds into their source population. The results obtained from the present study could aid future management decisions, ecological studies and conservation of local turkeys in a developing economy.     

Hepatocellular adenoma in a Eurasian otter (Lutra lutra)

A 7-year-old female Eurasian otter (Lutra lutra) at the Seoul Grand Park, Korea, died after displaying depression, anorexia, weight loss and rough skin for several days. At necropsy, a solitary friable round mass, which was approximately 12 × 9 × 5 cm and mottled dark red and yellow, was found bulging from the right hepatic lobe. Microscopically, the nonencapsulated, poorly circumscribed mass was composed of solid sheets of neoplastic hepatocytes. In addition, numerous small tan foci, ranging from 0.5 to 1.0 cm in diameter, were evenly scattered throughout the pancreatic tissue. These foci were found to be nonencapsulated, well-demarcated hyperplastic nodules of the exocrine pancreatic gland. We observed neither intrahepatic nor extrahepatic metastases. Based on the gross and microscopic changes, we diagnosed the animal as having a hepatocellular adenoma accompanied by exocrine pancreatic nodular hyperplasia.     

Comparison of the rebound tonometer (TonoVet) with the applanation tonometer (TonoPen XL) in normal Eurasian Eagle owls (Bubo bubo)

OBJECTIVE: To examine the feasibility and accuracy of a handheld rebound tonometer, TonoVet, and to compare the intraocular pressure (IOP) readings of the TonoVet with those of an applanation tonometer, TonoPen XL, in normal Eurasian Eagle owls. ANIMALS STUDIED: Ten clinically normal Eurasian Eagle owls (20 eyes). PROCEDURES: Complete ocular examinations, using slit-lamp biomicroscopy and indirect ophthalmoscopy, were conducted on each raptor. The IOP was measured bilaterally using a rebound tonometer followed by a topical anesthetic agent after 1 min. The TonoPen XL tonometer was applied in both eyes 30 s following topical anesthesia. RESULTS: The mean +/- SD IOP obtained by rebound tonometer was 10.45 +/- 1.64 mmHg (range 7-14 mmHg), and by applanation tonometer was 9.35 +/- 1.81 mmHg (range 6-12 mmHg). There was a significant difference (P = 0.001) in the IOP obtained from both tonometers. The linear regression equation describing the relationship between both devices was y = 0.669x + 4.194 (x = TonoPen XL and y = TonoVet). The determination coefficient (r(2)) was r(2) = 0.550. CONCLUSIONS: The results suggest that readings from the rebound tonometer significantly overestimated those from the applanation tonometer and that the rebound tonometer was tolerated well because of the rapid and minimal stress-inducing method of tonometry in the Eurasian Eagle owls, even without topical anesthesia. Further studies comparing TonoVet with manometric measurements may be necessary to employ rebound tonometer for routine clinical use in Eurasian Eagle owls.     

Ultrasound-guided dorsal approach for the brachial plexus block in common kestrels (Falco tinnunculus): a cadaver study

ObjectiveTo develop an ultrasound-guided dorsal approach to the brachial plexus and to investigate the nerve distribution and staining of a dyed injectate in common kestrel (Falco tinnunculus) cadavers.Study designProspective, cadaver study.AnimalsA group of three common kestrel cadavers (six wings).MethodsAll cadavers were fresh-frozen at –20 °C and thawed for 10 hours at room temperature before the study. The cadavers were placed in sternal recumbency and their wings were abducted. A 8–13 MHz linear-array transducer was placed over the scapulohumeral joint, at the centre of a triangle formed by the scapula and the humerus. The brachial plexus was identified between the scapulohumeralis muscle and the pectoralis major muscle, as hypoechoic structures lying just cranially to the axillary vessels. After ultrasound-guided brachial plexus identification, a 22 gauge, 50 mm insulated needle was advanced in-plane using ultrasound visualization. A volume of 0.5 mL kg^–1 of a 3:1 (2% lidocaine:methylene blue) solution was injected. Following cadaver dissection, the pattern of the spread was assessed, and the extent of nerve staining was measured with a calliper and deemed adequate if more than 0.6 cm of the nerve staining was achieved.ResultsThe brachial plexus was clearly identified in all wings with the dorsal approach. After dye injection, all the branches of the brachial plexus defined as nerves 1–5 (N1, N2, N3, N4 and N5) were completely stained in five (83%) and partially stained in one (17%) of the six wings.Conclusions and clinical relevanceThe ultrasound-guided dorsal approach allows a clear visualization of the brachial plexus structure. The injection of 0.5 mL kg^–1of a lidocaine/dye solution produced complete nerve staining in most cases. Further in vivo studies are mandatory to confirm the clinical efficacy of this locoregional anaesthesia technique in common kestrels (Falco tinnunculus).     

Sexual dimorphism in the African legless skink subfamily Acontiinae (Reptilia: Scincidae)

The extent to which sexual dimorphism in snout–vent length, tail length and head shape (length, width and height) manifests itself in the legless fossorial skink subfamily Acontiinae was investigated in representatives of all four of its genera, Acontias, Microacontias, Acontophiops and Typhlosaurus. Where data were available fecundity selection and diet partitioning (ecological causation) were tested as possible proximate causes for dimorphisms found. The possibility of a relationship between head shape and microhabitat density was also investigated. The data showed that significant sexual dimorphism in snout–vent length and head shape was present in only a minority of taxa and that it was absent with respect to tail length. There are indications of a relationship between head shape and microhabitat density, and head shape seems to become increasingly more pointed as SVL increases. A serious impediment to placing the findings of this study into a firm evolutionary context is the general lack of information about the ecology, social organization and behaviour of the taxa.