Ontogenetic variation and craniometric sexual dimorphism in the social giant mole-rat,Fukomys mechowii (Rodentia: Bathyergidae), from Zambia

The degree of maxillary molar tooth-row eruption and wear were used to assign samples of the social giant mole-rat, Fukomys mechowii, from Zambia, into nine relative age classes in order to assess ontogenetic (age) variation and craniometric sexual dimorphism, with reference to body mass. Univariate and multivariate statistical analyses showed craniometric differences between age classes 1–3 and age classes 5–9, with age class 4 being intermediate between these two age class groupings. This suggests that age class 4 lies at a point on a hypothetical growth curve where growth begins to stabilize. The intermediate placement of age class 4 in multivariate space broadly coincided with body mass categorizations into juveniles (age classes 1–3; <100 g), subadults (age class 4; c. 100–150 g), and adults (age classes 5–9; >150 g). The analyses also revealed the absence of sexual dimorphism in the relatively younger age classes 1–4 but its presence in the relatively older age classes 5–9, and these results are supported by data on body mass. These results may have implications in our understanding of the population and social structures, and reproductive strategies in this little-studied giant mole-rat.     

Food and feeding habits of Oreochromis mossambicus (Peters) in hypertrophic Hartbeespoort Dam,South Africa

The diet of 745 Oreochromis mossambicus (Peters) of less than 0,5 up to 2000 g wet mass, in Hartbeespoort Dam, was determined from stomach content analysis. Samples of fish were selected to cover a whole annual cycle. Small fish fed initially on zoobenthos and zooplankton, but fish with a mass of over 4 g fed increasingly on Microcystis aeruginosa Kutzing and detritus until these food items formed the dominant food source in O. mossambicus over 8 g. Some cannibalism was encountered in fish up to 64 g in the summer months. The ratio of intestinal length to total length of fish ranged from 0,58 in the smaller fish to 11,02 in larger fish and this indicated that there was an ontogenetic adaptation from a carnivorous to a phytoplanktivorous/detritivorous diet. Feeding in juvenile fish studied over 24 h was found to be most intense in the early morning and late afternoon but remained high throughout daylight hours decreasing considerably at night. The daily ingestion rate of food in O. mossambicus in Hartbeespoort Dam was estimated at 453 mg/g of fish. This comprised 45% M. aeruginosa and 55% detritus. It was apparent that of this matter ingested only a small percentage would be assimilated. Oreochromis mossambicus shows feeding and breeding preadaptations which enable it to successfully exploit a lacustrine environment. These adaptations enable it to maintain a large population in Hartbeespoort Dam despite frequent winter mortalities caused by water temperatures below their tolerance limits.     

虎皮鹦鹉发声行为学比较研究

为了解虎皮鹦鹉发声行为的性别差异,采用计算机鸣声分析技术对虎皮鹦鹉的鸣叫行为做了研究,结果表明,雄性虎皮鹦鹉的叫声明显比雌鸟的复杂多变,但是鸣声幅度比雌鸟的小;随着虎皮鹦鹉的成长,雌雄鸟的叫声越来越复杂,幅度越来越高。说明虎皮鹦鹉的叫声具有明显的性双态性,并且叫声随着年龄的增大越来越成熟,30日龄虎皮鹦鹉的鸣声复杂程度已接近成鸟水平。     

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.     

白带锯蛱蝶雌蝶利用视觉和嗅觉信息识别两性

[目的]探究视觉和嗅觉信息在白带锯蛱蝶雌蝶识别异性中扮演的作用,从而加深对性二型蝶类两性交流机制的认识。[方法]在网室内分别悬挂白带锯蛱蝶雄蝶和雌蝶的真实翅模型、打印的翅模型和活蝴蝶模型,记录雌蝶对以上模型的访问次数。[结果]表明:仅有视觉或嗅觉信号存在时,雌蝶对雄蝶模型访问次数均大于雌模型。雌蝶对雌雄翅和纸模型访问平均次数均有显著差异,说明雌蝶仅靠视觉信息能够辨别雌雄。雌蝶对雌雄嗅觉模型访问平均次数有显著差异,说明雌蝶仅靠嗅觉信息能够辨别雌雄。视觉和嗅觉信息均存在时,雌蝶对正常雄蝶访问平均次数多于雄蝶视觉和嗅觉模型,且对3种雄蝶的平均访问次数有显著差异,说明雌蝶识别雄蝶时偏好2种信息的综合作用。[结论]白带锯蛱蝶雌蝶利用视觉或嗅觉信息均能识别雌雄两性,雌蝶在识别两性时较偏爱同时有视觉和嗅觉信息的雄蝶。     

多疣狭口蛙的两性异形

测量和比较采自昆明东北郊的131只成年多疣狭口蛙K a lou la verrucosa标本(72♂59♀),同时野外观察雌雄蛙的伏卧姿势、运动方式和繁殖行为.成年雌雄蛙的体长、吻长、鼓膜直径、内突长、前臂宽、后肢全长和足长7个形态特征差异显著.对与体长相关的前臂宽、后肢全长和足长进一步回归分析表明,雄蛙前臂宽随体长的增长速率显著大于雌蛙,雌蛙后肢全长和足长随体长的增长速率显著大于雄蛙.雄蛙的前臂宽、后肢全长和足长均大于相同体长雌蛙的前臂宽、后肢全长和足长.繁殖期雄蛙前肢内侧及胸腹部布满分泌物,雌蛙无.雄蛙为2/3蹼,雌蛙约为1/3蹼.雄蛙具单咽外声囊,雌蛙无.雄蛙肛部疣粒大而光滑,雌蛙肛部疣粒细长而尖.     

2种丽细蛾触角感受器超微结构特征

茶丽细蛾和黑丽细蛾分别是山茶科和槭树科部分植物的潜叶害虫。旨在通过观察掌握2种丽细蛾触角感受器的类型、数量、分布及形态特征,探讨触角感受器特征在种内和种间的差异性。用扫描电镜观察触角感受器的类型及形态特征并测量特征值。2种丽细蛾的触角感受器共11种类型16种亚型,分别是毛形感受器（2种亚型）、刺形感受器（2种亚型）、腔锥形感受器（2种亚型）、栓锥形感受器（3种亚型）、耳形感受器（3种亚型）、锥形感受器、鳞形感受器（2种亚型）、节间感受器（2种亚型）、Böhm氏鬃毛、乳突感受器和片刺形感受器。茶丽细蛾雌性有11种（11种亚型）感受器,雄性有10种（13种亚型）。黑丽细蛾雌性和雄性均有10种感受器,13种亚型。雌性茶丽细蛾鞭节第1亚节有半融合现象。2种丽细蛾的触角感受器均有性二型现象,在种间也具有一定的差异性。节间感受器、乳突感受器和片刺形感受器在鳞翅目昆虫中首次报道。研究结果丰富了细蛾科乃至鳞翅目昆虫触角感受器的类型,可为深入研究细蛾科昆虫系统发育关系、行为特征、害虫防治等提供基本依据。     

Effects of Estradiol and Testosterone on the Expression of Growth‐related Genes in Female and Male Nile Tilapia,Oreochromis niloticus

Nile tilapia exhibits strong sexual growth dimorphism. The potential role of sex steroid hormones in sexual growth dimorphism is not fully understood. We investigated the effects of estradiol (E₂) and testosterone (T) on growth rate, plasma sex hormones, and expression of growth hormone (GH)‐insulin‐like growth factor (IGF) axis genes and muscle regulatory factor (MRF) genes in female and male Nile tilapia. The results revealed that serum concentrations of E₂ and T were significantly higher after correlative injection (P < 0.05). Compared to male fish, female fish had lower growth rates. E₂ increased growth performance in females with no significant effects on males, whereas T significantly increased growth performance in males, with no significant effects on females. In females, E₂ significantly increased expression of ghr1, ghr2, igf1, and igf2, while T decreased igf2 and increased ghr1 and ghr2 expression. In males, T increased expression of igf1, igf2, ghr1, and ghr2, and E₂ decreased expression of igf1, ghr1, and ghr2. Additionally, E₂ and T enhanced the expression of MRF genes (myod1, myod2, myog, and myf5) in female and male fish, respectively. The results suggest that sex steroid hormones play a role in sexual growth dimorphism by regulating the expression of GH‐IGF axis and MRF genes.     

瓯江鲫鱼胸鳍的波动性不对称、两性异形和生育

研究浙江瓯江鲫鱼胸鳍的波动性不对称、两性异形和生育力。雌雄两性的鳍长、鳍条数的不对称均属波动性不对称。雌雄两性的胸鳍长和鳍条数的不对称指数之间相关关系不显著。雌性个体显著大于雄性个体,特定体长的雄性胸鳍长显著大于雌性,雄性的鳍条数显著大于雌性。鳍长和鳍条数的不对称指数雌雄两性差异不显著,雌雄两性鳍条数对称个体的比例差异不显著。以体长和时间为控制变量,怀卵数量与鳍长和鳍条数的不对称指数具有显著的负相关,与鳍长和鳍条数的相关不显著。以体长和发育时间为控制变量,平均卵重与鳍条数的不对称指数具有显著的正相关,与其他变量的相关不显著。分析表明,雄性较大的胸鳍可能与雄性的性选择有关,胸鳍的波动性不对称可能提供了一种发育历程的指示,间接影响雌性生育力。     

Sex‐dependent responses of perch to changes in water clarity and temperature

Rising temperatures and decreasing water transparency of lakes have strong wide ranging effects on fish. Fish responses to various changes in the environment are usually species‐dependent, but responses may also vary within species. In general, large individuals are considered to be more sensitive to environmental variation due to higher energy demand, than smaller individuals. Similarly, large individuals require more food to maintain bodily functions and are thus more sensitive to resource and food scarcity. These size‐specific responses to environmental gradients are also sex‐dependent in species that exhibit sexual size dimorphism (SSD). We studied in enclosures with short‐term experiments how rising temperatures and decreasing water transparency regulate the feeding rates of female and male European perch (Perca fluviatilis L.). To explore experimental results, we calculated perch SSD in nine lakes with varying environmental conditions using previously collected field data. The results of the experiments revealed that the combined effect of water transparency and temperature on the feeding rate of fish is gender‐dependent: feeding rate of females decreased more than that of males. The experimental results were also supported by field data that revealed a negative relation between water transparency and the magnitude of SSD in perch. Our results suggest that rising temperatures and decreasing water transparency may potentially decrease fish size in a sex‐dependent manner. As female size is one of the main demographic traits determining the reproductive success of a fish population, changing environments may have unexpected and far‐reaching consequences on fish population dynamics.