The adaptive significance of electrophoretic mobility in phosphoglucose isomerase (PGI)

Sexual dimorphism in size and plumage was investigated in the lek-breeding Jackson's widowbird Euplectes jacksoni. Size dimorphism was evident from the sexual difference in tarsus length, reflecting skeletal body size. The long tail and the wide collar of breeding plumaged males were obvious secondary sex traits, but the wing was also longer than in subadults and might likewise be sexually selected (i.e. not merely a byproduct of body size). Possibly, the increased wingspan functions to save energy during the jump display. To reveal intrasexual selection, courtholders were compared with floaters (nuptial males captured off the leks), and were found to be larger in body size, wing length, collar and tail. The roles of inter-and intrasexual selection are discussed with reference to previously demonstrated female choice, and new results indicating competition for access to leks: quick reoccupation of deserted display courts, frequent observations of intruders and a finding that central males were more aggressive than peripherals. Observations imply that the collar is an agonistic signal that is neutral with respect to female choice. Possible contributions of natural selection to the sexual dimorphism are also considered.     

HOMOGENEITY OF THE GENETIC VARIANCE-COVARIANCE MATRIX FOR ANTIPREDATOR TRAITS IN TWO NATURAL POPULATIONS OF THE GARTER SNAKE THAMNOPHIS ORDINOIDES

Quantitative genetic models of evolution rely on the genetic variance-covariance matrix to predict the phenotypic response to selection. Both prospective and retrospective studies of phenotypic evolution across generations rely on assumptions about the constancy of patterns of genetic covariance through time. In the absence of robust theoretical predictions about the stability of genetic covariances, this assumption must be tested with empirical comparisons of genetic parameters among populations and species. Genetic variance-covariance matrices were estimated for a suite of antipredator traits in two populations of the northwestern garter snake, Thamnophis ordinoides. The characters studied include color pattern and antipredator behaviors that interact to facilitate escape from predators. Significant heritabilities for all traits were detected in both populations. Genetic correlations and covariances were found among behaviors in both populations and between color pattern and behavior in one of the populations. Phenotypic means differed among populations, but pairwise comparisons revealed no heterogeneity of genetic parameters between the populations. The structure of the genetic variance-covariance matrix has apparently not changed significantly during the divergence of these two populations.     

Targeting of oleosins to the oil bodies of oilseed rape (Brassica napus L.)

Oleosins of Brassica napus L. (oilseed rape) synthesized by in-vitro translation were found to be very efficiently targeted to microsomal membranes but only poorly translocated to oil bodies or emulsified oil. The use of other bilayer membranes as controls showed that this interaction was specific. The rate of oleosin synthesis in the presence of microsomes was enhanced about threefold, indicative of the involvement of the signal-recognition particle in the targeting process. There is no evidence for the cleavage of the protein during targeting and the protein sequence reveals no consensus cleavage site for the signal peptide. Protection experiments using Proteinase K revealed that about 6 kDa of the protein is exposed on the cytoplasmic side of the ER but the remainder is protected. Carbonate (pH 11) washing of microsomal membranes after in-vitro translation confirmed that oleosins have a domain which remains inserted in the ER rather than the protein being transported completely into the lumen of the ER. These results indicate that oleosins are transported via the ER prior to their accumulation on oil bodies.     

Localization of cholecystokinin-like and calcitonin-like peptides in infant carotid bodies: a light- and electron-microscopic immunohistochemical study

Previous immunohistochemical studies have identified several regulatory peptides in the carotid body chief cells in both humans and animals. These peptides, together with amines, may be important in the modulation of the chemoreflex by the carotid body. We report the localization and distribution of calcitonin and cholecystokinin-like (CCK) immunoreactivity in chief cells of human infant carotid body by light- and electron-microscopic immunohistochemical techniques. Consecutive sections immunostained with calcitonin and/or CCK antibodies revealed positively stained chief cells, both alone and in clusters, scattered throughout the carotid body lobule. Generally more chief cells were positive for calcitonin than for CCK. This was confirmed by quantiative analysis showing that the ratio of calcitonin to CCK immunoreactive cells was consistently >2:1 in all cases studied. There was no apparent correlation between the immunoreactivity for the two peptides and the age, sex, or postmortem interval. Calcitonin-like and CCK-like immunoreactivities were localized electron-microscopically over the dense core granules of the chief cells. Calcitonin and CCK-like peptides in carotid body chief cells may act as neutransmitters or neuromodulators involved in chemoreception.     

Fluctuating asymmetry and lifetime mating success are correlated in males of the damselfly Coenagrion puella (Odonata: Coenagrionidae)

Abstract.

• 1 The influence of fluctuating asymmetry on lifetime mating success of males of the damselfly Coenagrion puella (Odonata: Coenagrionidae) was investigated. Fluctuating asymmetry was measured as the difference in length of left and right fore and hind wings.
• 2 Males with more symmetrical wings enjoyed higher lifetime mating success.
• 3 Larger males, in contrast to a previous study of this species, also had higher mating success. This may be attributed to differences in the weather conditions prevailing at the time of the studies.

     

The ant Lasius niger shows no relationship between task efficiency and body size variation among workers

In ants, workers of different sizes may perform various tasks, even in so-called monomorphic species with relatively low body size variation. However, it is unclear if the body size diversity of monomorphic workers correlates with task efficiency, especially in stressful contingencies. Here we tested if the body size variation of workers corresponds with its efficiency in transferring pupae. Transferring brood is a pre-set behavioral response to stress, e.g. suboptimal temperature. Here we applied a laboratory experiment simulating nest damage. The study was performed on the common garden ant (Lasius niger (Linnaeus, 1758)) – a species with no distinct worker subcastes. The efficiency of workers was measured as the latency of transferring pupae from a lit part of the experimental colony to a darkened part, while the body size diversity was expressed as the within-colony coefficient of variation in head width. We did not find any significant correlation between efficiency and body size variation. Summarizing the existing studies and the present results, we propose the hypothesis that the body size diversity of L. niger may have implications for workers’ division of labor but not for their task efficiency in a stressful contingency.     

Relationships of reproductive traits and body size with attainment of sexual maturity and age in Blanding's turtles (Emydoidea blandingi)

To place associations among body size, age at maturity, age, and reproductive traits of a long-lived organism in the context of current life history models based on the concept of norms of reaction, we examined data from a mark-recapture study of Blanding's turtles (Emydoidea blandingi) in southeastern Michigan during 24 of the years between 1953 and 1988. Females matured between 14 and 20 years of age. Both the smallest and largest adult females in the population were reproducing for the first time in their lives. This result suggests that a combination of differences in juvenile growth rates and ages at maturity, and not indeterminate growth, are the primary cause of variation in body size among adults. Body size variation among individuals was not related to age at sexual maturity. Females that had slower growth rates as juveniles matured later at similar mean body size compared to those with more rapid growth that matured at an earlier age. As a result, a linear model of age at sexual maturity with growth rates of primiparous females between hatching and maturity was significant and negative (R² = 0.76). Frequency of reproduction of the largest and smallest females was not significantly different. Clutch size did not vary significantly with age among either primiparous or multiparous females. Clutch sizes of primiparous females and multiparous females were not significantly different. However, older females (>55 years minimum age) reproduced more frequently than did younger females (minimum age <36 y).     

Extra-pair paternity and sexual dimorphism in birds

Differences in the strength of sexual selection between males and females can lead to sexual dimorphism. Extra-pair paternity (EPP) can increase the variance in male reproductive success and hence the opportunity for sexual selection. Previous research on birds suggests that EPP drives the evolution of dimorphism in plumage colour and in body size. Because EPP increases the intensity of sexual selection in males, it should lead to increased dimorphism in species with larger or more colourful males, but decreased dimorphism in species with larger or more colourful females. We explored the covariation between EPP and sexual dimorphism in wing length and plumage colouration in 401 bird species, while controlling for other, potentially confounding variables. Wing length dimorphism was associated positively with the frequency of EPP, but also with social polygamy, sex bias in parental behaviour and body size and negatively with migration distance. The frequency of EPP was the only predictor of plumage colour dimorphism. In support of our prediction, high EPP levels were associated with sexual dichromatism, positively in species in which males are more colourful and negatively in those in which females are more colourful. Contrary to our prediction, high EPP rates were associated with increased wing length dimorphism in species with both male- and female-biased dimorphism. The results support a role for EPP in the evolution of both size and plumage colour dimorphism. The two forms of dimorphism were weakly correlated and predicted by different reproductive, social and life-history traits, suggesting an independent evolution.     

鲤鱼鳞被和体色在人工诱导雌核发育中的遗传变异

于1986—1988年,先后人工诱导2尾红镜鲤和4尾荷包红鲤抗寒品系雌核发育,获得雌核发育2倍体当年鱼种2133尾,其中红镜鲤685尾,荷包红鲤1448尾。通过对这些后代鳞被和体色两个质量性状的分析,发现荷包红鲤抗寒品系雌核发育2倍体(1987)中有约三分之一个体表现散鳞型鳞被和桔红色(出现由深到浅一系列变化)及少量桔黄色、肉红色个体。红镜鲤散鳞型鳞被出现体表全部覆盖不规则大型鳞片、2/3、1/2覆盖不规则的大型鳞片和散鳞型个体。体色出现桔红色、桔黄色,上述二色都出现由深到浅一系列变化和肉红色。这两个质量性状在雌核发育代中表现出数量性状的特征。     

北部湾鱼类碳、氮、磷生态化学计量特征

为探究北部湾鱼类生态化学计量特征,于2021年3月—4月采集分析了北部湾沿岸9个渔港的79种鱼类(382尾)碳(C)、氮(N)、磷(P)含量特征。结果表明北部湾鱼类C、N、P元素含量变化范围分别为33.87%—58.34%、6.31%—14.92%和0.77%—4.67%;C∶N、C∶P、N∶P的变化范围分别为3.43—9.72、19.15—173.06和5.04—33.68,其中P元素含量变化最大,导致C∶P和N∶P的变化。不同物种在科间的差异较大,科内的差异较小。不同体型和食性鱼类之间的C、N、P含量及比值具有显著差异(P<0.05)。鱼类的C∶P和N∶P与P含量呈显著负相关(R²=0.966,P<0.01;R²=0.877,P<0.01),P含量和Ca含量呈显著正相关(R²=0.919,P<0.01),P含量的变化可能与鱼类骨骼和鳞片的形成有关。总之,北部湾鱼类未保持严格的生态化学计量平衡,鱼类生态化学计量特征存在显著的种间差异,主要因鱼类不同的体型和食性差异所致。