Extreme tolerance to environmental stress of sexual and parthenogenetic resting eggs of Eucypris virens (Crustacea,Ostracoda)

1. The freshwater ostracod (Ostracoda), Eucypris virens, is commonly found in European temporary pools, where its long‐term persistence completely relies on the build‐up of resting egg banks. Extreme tolerance of dormant eggs and seeds is widely assumed, but freshwater ostracod eggs are relatively poorly studied. The study of ostracod resting eggs is of particular relevance as it may yield the key to understanding the distribution of the sexes in many species capable of both sexual and asexual reproduction. 2. We assessed the tolerance of dried resting eggs produced by females originating from three populations with males and three all‐female E. virens populations. Hatching time and success was compared between control eggs and eggs exposed to one of seven ecologically relevant stressors: digestive enzymes, high salinity, deep freezing, hydration, UV‐B radiation, hypoxia and insecticide treatment. 3. None of the stressors reduced significantly the viability of either sexual or asexual eggs. When compared with the reproductive mode–specific controls, exposure to UV‐B radiation had a mild impact on the survival of sexual and asexual eggs (?16.8 and ?22.4%, respectively), but this was only significant for asexual eggs. These results point to an extreme tolerance of E. virens resting eggs and have important implications for the ecology and evolution of the species. 4. The timing of hatching was not affected by the stress treatment, except for UV‐B radiation. A marginally significant delay in hatching response was observed for UV‐B‐radiated eggs when compared to the overall mean, but this treatment effect was absent when compared with the reproductive mode–specific controls. 5. The populations with males produced eggs that hatched on average earlier (?1.5 days at 17 °C) and were more successful (+26%) than asexual eggs. Due to the limited number of populations and the population‐specific origin and age of the eggs, the possibility due to the differences in age and origin of the resting eggs, or to variations in local conditions, cannot be ruled out.     

Projected marine climate change: effects on copepod oxidative status and reproduction

Zooplankton are an important link between primary producers and fish. Therefore, it is crucial to address their responses when predicting effects of climate change on pelagic ecosystems. For realistic community‐level predictions, several biotic and abiotic climate‐related variables should be examined in combination. We studied the combined effects of ocean acidification and global warming predicted for year 2100 with toxic cyanobacteria on the calanoid copepod, Acartia bifilosa. Acidification together with higher temperature reduced copepod antioxidant capacity. Higher temperature also decreased egg viability, nauplii development, and oxidative status. Exposure to cyanobacteria and its toxin had a negative effect on egg production but, a positive effect on oxidative status and egg viability, giving no net effects on viable egg production. Additionally, nauplii development was enhanced by the presence of cyanobacteria, which partially alleviated the otherwise negative effects of increased temperature and decreased pH on the copepod recruitment. The interactive effects of temperature, acidification, and cyanobacteria on copepods highlight the importance of testing combined effects of climate‐related factors when predicting biological responses.     

Low breeding success of the little egret (Egretta garzetta) near residential areas and in colonies exposed to gales: a comparison of colony in Sichuan,Southwest China,with literature

The breeding biology of the little egret (Egretta garzetta) was studied in 20 nests within the mixed-species breeding colonies at Nanchong, Sichuan, Southwest China, in 2006. By measuring a set of physical characteristics of vegetation at the nests and at a set of 20 randomly chosen sites we showed that birds preferentially used taller trees in areas with fewer shrubs of higher species diversity. Nests at lower locations in trees had marginally lower hatching success due to their destruction by humans; this destruction contributed marginally significantly to lowering of the total nesting success in all studied nests. Although gale winds also had a negative effect on breeding success, the anthropogenic influences were a greater factor in reproductive failure. We found similar effects in our review of literature on breeding success of the little egret from various geographical areas. Our results may be of use by conservation organizations in their actions to protect colonies of the little egret.     

An egg‐laying device to estimate the induction of sterility in Ceratitis capitata (Diptera: Tephritidae) sterile insect technique programmes

Area‐wide environmentally friendly pest control methods such as the sterile insect technique (SIT) are being developed and improved to contribute in managing agricultural, environmental and public health problems. A key aspect to evaluate performance of sterile males is to directly measure sterility induction in the field. Sterility induction has been estimated for tephritid fruit flies by recovering egg from host fruit in the field, the method is, however, impractical, and past efforts to develop artificial egg‐laying devices have not prospered. Here, we evaluated response of wild gravid Ceratitis capitata (Medfly) females to long‐distance fruit‐based chemical attractants, visual and tactile stimuli to develop an artificial egg‐laying device. The device combining the most attractive features was further tested under two deployment schemes. Finally, devices and deployment tactics were used to compare fertility levels between feral Medfly females under conventional management and under SIT. Agar spheres wrapped in plastic film, baited with pressed peach juice and visually enhanced with yellow discs received more egg than other combinations of attractive features. Such devices also received more eggs when deployed on fruitless trees and when placed on the orchard perimeter. The egg hatch in an orchard under conventional management was estimated at 86%, whilst egg hatch in an area under SIT was reduced to 31%. The egg‐laying devices are therefore useful to measure sterility induction and can be further improved by refining long‐distance attraction and deployment schemes.     

利用CRISPR/Cas9双元转基因体系探究家蚕配子生成素结合蛋白基因Bmggnbp2的功能

[目的]配子生成素结合蛋白2(gametogenetin binding protein 2,ggnbp2)在哺乳动物配子发生等生殖相关过程中发挥重要作用.本研究以家蚕Bombyx mori为模型,探究驯化基因ggnbp2的生物学功能,为鳞翅目昆虫中该基因的深入研究提供线索.[方法]在NCBI GenBank数据库通过...     

Unpredictable offspring survivorship in the damselfly, Megaloprepus coerulatus, shapes parental behavior, constrains sexual selection, and challenges traditional fitness estimates

Evolutionary biologists typically assume that the number of eggs fertilized or developing embryos produced is correlated with an individual's fitness. Using microsatellite markers, we document for the first time estimates of realized fitness quantified as the number of offspring surviving to adulthood in an insect under field conditions. In a territorial damselfly whose males defend tree hole oviposition sites, patterns of offspring survivorship could not be anticipated by adults. Fewer than half of the parents contributing eggs to a larval habitat realized any reproductive success from their investment. The best fitness correlate was the span over which eggs in a clutch hatched. Among parents, female fecundity and male fertilization success were poor predictors of realized fitness. Although body size was correlated with female clutch size and male mating success, larger parents did not realize greater fitness than smaller ones. The uncoupling of traditional fitness surrogates from realized fitness provides strong empirical evidence that selection at the larval stage constrains selection on mated adults.     

Fetal development of mouse oocytes and zygotes cryopreserved in a nonconventional freezing medium

This study (1) analyzed fetal development of mouse embryos after oocyte cryopreservation in CJ2, a choline-based medium, (2) examined the effect of culture duration in vitro on subsequent fetal development, and (3) compared survival and fetal development of zygotes frozen in embryo transfer freeze medium (ETFM; sodium-based medium) or CJ2. Unfertilized oocytes and zygotes were cryopreserved using a slow-cooling protocol. After thawing, oocytes were inseminated after drilling a hole in their zona, cultured in vitro either to the two-cell or blastocyst stage, and transferred to the oviducts or uterine horns of recipient mice. In parallel experiments, frozen-thawed zygotes were similarly cultured and transferred. Implantation rates for transferred embryos were high (range 66-88%), regardless of whether they had been frozen as oocytes or zygotes and whether they had been transferred to the oviduct or uterus. However, fetal development was significantly higher when two-cell embryos were transferred. With blastocyst transfer, control embryos implanted and produced a greater proportion of fetuses than did oocytes frozen in CJ2, whereas transfer at the two-cell stage resulted in similar proportions of implantation sites and fetuses. Blastocyst transfer of zygotes cryopreserved in ETFM or CJ2 produced similar fetal development rates (23.6% vs 20.0%), but when frozen-thawed zygotes were transferred at the two-cell stage the fetal development rates were higher in the ETFM group (53.3%) than in the CJ2 group (32.0%). A high proportion (46.7%) of oocytes frozen in CJ2 in a nonprogrammable freezer and plunged at -20 degrees C developed into live offspring. This study shows that in the mouse (1) oocytes frozen in CJ2 can develop into viable fetuses, (2) prolonging culture in vitro has a detrimental effect on embryo transfer outcome, and (3) CJ2 offers no advantage for zygote cryopreservation.     

Embryonic hatching enzyme strypsin/ISP1 is expressed with ISP2 in endometrial glands during implantation

Embryo hatching and outgrowth are the first critical steps on the way to a successful pregnancy. It is generally held that serine proteases are responsible for this process, although the exact mechanisms of action are not clearly understood. Recently, we described two novel implantation serine proteinase (ISP) genes that are expressed during the implantation period. The ISP1 gene encodes the embryo-derived enzyme strypsin, which is necessary for blastocyst hatching in vitro and the initiation of invasion. The ISP2 gene, which encodes a related tryptase, is expressed in endometrial glands and is regulated by progesterone during the peri-implantation period. Based on similarities between ISP2 gene expression and that of a progesterone-regulated lumenal serine proteinase activity associated with lysis of the zona pellucida, we have suggested that the strypsin related protein, ISP2, may encode a zona lysin proteinase. As tryptases naturally assemble to form tetrameric structures, we have hypothesized that ISP1 and ISP2 tetramerize to form strypsin and lysin, respectively. In this study, we demonstrate that like ISP2, the ISP1 gene is also expressed in endometrial glands and is positively regulated by progesterone during implantation. Using in situ hybridization of adjacent tissue sections, we show that the ISP1 and ISP2 genes are co-expressed within the endometrial gland. Following evidence that ISP1 and 2 can efficiently form homotetramers and heterotetramers in silico, we suggest that ISP heterotetramers may be also be secreted into the uterine lumen during the implantation period. That the embryonic hatching enzyme, may also be secreted into the uterine lumen from uterus, may provide insight into the mechanisms of hatching and implantation initiation.