Effects of cytochalasin B on sperm-egg interactions

The effects of cytochalasin B (CB) on the interaction of sea urchin (Arbacia), molluscan (Spisula), and mammalian (Mus) gametes have been examined. Despite the absence of sperm incorporation and gamete membrane fusion, CB-treated Arbacia and Spisula eggs (1–10 μg/ml for 1–10 min) mixed with sperm activated. Unlike the situation observed in Arbacia and Spisula, mouse eggs treated with CB (1–50 μg/ml for 1 hr) are capable of sperm incorporation. These data are discussed with reference to possible mechanisms by which sperm may induce eggs to activate.     

Acid release following activation of surf clam (Spisula solidissima) eggs.

Acid release was observed after activation of Spisula eggs with excess KCI. This acid release begins within 20 sec after the activation and continues for 9–15 min. The amount of acid released was 6.8 μmole per milliliter of packed eggs. In Ca-free or Na-free sea water, the acid release is completely inhibited; subsequent addition of the deficient ion leads to acid release and breakdown of germinal vesicles. These results suggest that Spisula eggs release protons after activation in a manner similar to that of sea urchin eggs, and that acid release with concomitant increase in cytoplasmic pH is probably a general event on activation of marine eggs.     

Surface alterations of fertilized surf clam (Spisula solidissima) eggs induced by concanavalin A

Fertilized Spisula eggs, incubated in ConA, were examined at periodic intervals to determine the effects of lectin binding on events of fertilization and cleavage. ConA was localized to specific regions of the vitelline layer and plasma membrane by reacting lectin-treated eggs with horseradish peroxidase and diaminobenzidine. In contrast to eggs, little reaction product was associated with the plasma membrane of spermatozoa. Sperm that fused with ConA-treated eggs failed to move into the cortex of the ovum and were observed as bulbous appendages at the surface of the zygote. Reorganization of sperm nuclei was inhibited, and male pronuclei failed to develop. ConA also inhibited polar body formation and cleavage. The maternally derived chromatin underwent meiosis, and the chromosomes normally taken into the first and second polar bodies were retained within the zygote. All of the maternally derived chromatin was organized within four or more female pronuclei which subsequently entered mitosis. The effects of ConA binding on events at the surface of fertilized Spisula eggs were abrogated by α-methyl-d-mannoside; succinyl-ConA only partially inhibited fertilization-related processes. The effects of ConA are discussed in terms of possible cross-linking of surface components of fertilized Spisula eggs which may inhibit deformation of the zygote cortex.     

Regulation of Tubulin Organization During Meiosis

Meiotic spindle formation in Spisula solidissima oocytes hasbeen studied in vivo and in vitro. Measurements were made ofpolymerized tubulin content during the first meiotic division.The amount of polymer was high prior to activation of the eggs,fell to a minimum of about 5 min after activation and at 15min (metaphase) returned to approximately its initial value.The polymerized tubulin in the unactivated eggs appears to beorganized into granular spheres about 10–20 microns indiameter attached to the egg cortex. This particle containsfew microtubules but is composed primarily of a granular matrixand fibrous material. The granular matrix may be a polymorphicaggregate of tubulin and could be a storage form of tubulinor an intermediate in microtubule assembly. The polymerization and organization of microtubules has beenstudied in vitro, using crude homogenates of Spisula oocytes.Microtubules can be formed in homogenates of both activatedand unactivated eggs; however, in homogenates of eggs in whichnuclear membrane breakdown has occurred, microtubules form arounda central phase dense particle resulting in a structure whichresembles a spindle aster. The central particle appears to bea microtubule organizing center (MTOC). The MTOC can be pelleledby centrifugation and will induce aster formation when remixedwith the supernatant. Aster formation can be obtained usingsupernatants prepared from either activated or unactivated eggs,while the pellet must be obtained from activated eggs. Thus,tubulin subunits appear to be capable of spindle formation atall stages, while MTOC formation or activation does not occuruntil about the time of nuclear membrane breakdown.     

Maternal messenger RNA and histone synthesis in embryos of the surf clam Spisula solidissima.

Messenger RNA has been isolated from the postribosomal supernatant of Spisula solidissima eggs. This mRNA directs the synthesis of several proteins when added to the ascites or wheat germ cell free system. No histone except F1 is coded for by Spisula egg mRNA, in contrast to what has been reported previously for sea urchin egg mRNA. In sea urchin eggs histone mRNA is among the abundant species of maternal mRNA.Histones have been prepared from Spisula embryos at different development stages and histone synthesis followed by incubation with (¹⁴C)lysine. The analysis by electrophoresis on acrylamide gels indicates that the pattern of synthesis of histones changes during development and that a new histone F1 fraction is actively synthesized from the 32–64 cells stage. In earlier embryos a different F1 histone is synthesized and the mRNA for this protein may be the only histone mRNA present in eggs.     

Ultrastructural and Morphometric Observations of Cortical Endoplasmic Reticulum in Arbacia,Spisula and Mouse Eggs*

Results of morphometric investigations indicate that Arbacia eggs possess a network of cortical endoplasmic reticulum equal in volume and surface area to that within the subcortex. The cortical endoplasmic reticulum surrounds individual cortical granules and forms associations with the plasma membrane reminiscent of junctions shared by the sarcolemma and sarcoplasmic reticulum. Mouse eggs, which also exhibit a cortical granule reaction, possess endoplasmic reticulum that is associated with cortical granules and the plasmalemma. The same relative volume of cortical endoplasmic reticulum is present in mouse eggs as in Arbacia. Significantly less cortical endoplasmic reticulum is present in Spisula eggs which do not undergo cortical granule discharge upon activation. These observations are discussed in light of the hypothesis that the cortical endoplasmic reticulum transduces the interaction of the gametes into an intracellular calcium release which initiates the cortical granule reaction and the activation of development.     

The Development of Mitochondria in Arum Spadix

Electron micrographs of Arum spadix cells prepared at four stagesof development all showed abundant sections of mitochondriawith tubular ingrowths (microvilli). At the earliest stage (whenthe spadix cells were still dividing) there was an average of9 sections of microvilli per mitochondrion. In later stagesof development, when the cells were growing by elongation, thenumber of microvilli rose to 22. It was reported earlier that the succinoxidase activity of themitochondria of Arum spadix increased as the spadix developed,and it is now shown that the rise in enzyme activity parallelsthe increase in length of microvilli.     

Mitochondrial Placement and Function in Insect Ion-transporting Cells

The ion-transporting epithelia of insects possess some unusualmorphological adaptations which promote close juxtapositionof mitochondria and the ion-transporting plasma membranes. Aparticularly striking example of this adaptation is providedby the movement of branches of mitochondria into and out ofthe apical microvilli in the Malpighian tubules. In the hemipteranRhodmus prohxus, the microvilli in the resorptive lower tubuleare small and contain no mitochondria during the non-transportingperiod. When ion transport is stimulated,either in vivo or invitro, there is a concomitant growth in microvillar volume andsurface area. In addition, branches of mitochondria enter thesemicrovilli. It has been shown that these mitochondrial movementsare driven by an actinassociated process involving the microvillarcore microfilaments. The stimulation for this movement in vivois the insect diuretic hormone. In the lepidopteran Calpodesethhus, the rates of fluid transport which the Malpighian tubulescan sustain vary during the insect's life stages. Larvae andadults show rapid transport, while pupal Malpighian tubulesshow none. In the larvae and adults, microvilli in the Malpighiantubules are large and contain mitochondria. In the pupae, reducedtransport is associated with mitochondrial retraction and microvillarshrinkage. These ultrastructural changes appear tobe regulatedby the insect's developmental hormones. In the Malpighian tubulesof adult female mosquitoes of the genus Aedes, intracellularinfection by microfiliarial nematodes has hen shown to causemitochondrial retraction and reduced rates of fluid transport.A model is presented which serves to summarize currently proposedmechanisms of membrane and mitochondrial function in the ion-transportingepithelia of insects.     

繁殖寄主对赤眼蜂羧酸酯酶和乙酰胆碱酯酶的影响

通过测定赤眼蜂Trichogramma羧酸酯酶和乙酰胆碱酯酶的活性、对底物的亲和力以及对抑制剂的敏感度研究了繁殖寄主对松毛虫赤眼蜂T.dendrolimi和螟黄赤眼蜂T.chilonis的影响。柞蚕卵和米蛾卵繁殖的赤眼蜂羧酸酯酶对底物的亲和力有不同程度的影响,柞蚕卵繁殖的赤眼蜂羧酸酯酶对α-乙酸萘酯或β-乙酸萘酯的亲和力最高是米蛾卵的2倍以上。繁殖寄主对乙酰胆碱酯酶对底物亲和力没有明显的影响。米蛾卵繁殖的松毛虫赤眼蜂羧酸酯酶活性明显高于柞蚕卵繁殖的种群,而米蛾卵繁殖的螟黄赤眼蜂种群羧酸酯酶的活性明显低于柞蚕卵繁殖的种群。用柞蚕卵繁殖的松毛虫赤眼蜂种群对对氧磷的敏感度明显低于米蛾卵繁殖的种群,而增效磷则正好相反。繁殖寄主对松毛虫赤眼蜂吉林种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度没有明显的影响,而在松毛虫赤眼蜂广东种群和螟黄赤眼蜂中,柞蚕卵繁殖的种群乙酰胆碱酯酶对DDVP和毒扁豆碱的敏感度明显低于米蛾卵繁殖的种群。     

Cape honeybees, Apis mellifera capensis, police worker-laid eggs despite the absence of relatedness benefits

In the Cape honeybee, Apis mellifera capensis, workers lay diploid(female) eggs via thelytoky. In other A. mellifera subspecies,workers lay haploid (male) eggs via arrhenotoky. When thelytokousworker reproduction occurs, worker policing has no relatednessbenefit because workers are equally related to their sisterworkers' clonal offspring and their mother queen's female offspring.We studied worker policing in A. m. capensis and in the arrhenotokousAfrican honeybee A. m. scutellata by quantifying the removalrates of worker-laid and queen-laid eggs. Discriminator coloniesof both subspecies policed worker-laid eggs of both their ownand the other subspecies. The occurrence of worker policing,despite the lack of relatedness benefit, in A. m. capensis stronglysuggests that worker reproduction is costly to the colony andthat policing is maintained because it enhances colony efficiency.In addition, because both subspecies policed each others eggs,it is probable that the mechanism used in thelytokous A. m.capensis to discriminate between queen-laid and worker-laideggs is the same as in arrhenotokous A. m. scutellata.     

Structural characterization of glycosphingolipids from the eggs of Schistosoma mansoni and Schistosoma japonicum

The granulomatous pathology in human intestinal schistosomiasisis induced primarily by the egg antigens of schistosome, a parasitictrematode. Glycolipids and glycoproteins were extracted fromthe eggs of the two major species which infect human, Schistosomamansoni and Schistosoma japonicum, for structural characterizationbased on highly sensitive mass spectrometric analysis coupledwith chemical derivatization. Here, we demonstrate that a seriesof uniquely multifucosylated glycosphingolipids constitute themajor egg glycolipids of S.mansoni but not of S.japonicum. TheS.mansoni glycosphingolipids were found to be extended by varyingnumbers of an unusual repeating unit,     

中红侧沟茧蜂在粘虫体内的发育 及畸形细胞发生

中红侧沟茧蜂Microplitis mediator的初产卵因受雌蜂产卵器的机械挤压,在形态上有别于未产出的卵,这种机械挤压激活了蜂卵的胚胎发育。产卵后 6 h,胚带和浆膜层开始分化,20 h胚胎成形,包裹在单层细胞的浆膜层内。32～34 h,幼蜂孵化,顶部的浆膜层立即分散形成畸形细胞,尾部的浆膜层则逐渐释放细胞。1龄幼蜂具一对角质的颚,用来消灭同种竞争者。寄生后108～113 h,1龄幼蜂蜕皮进入2龄。2龄幼蜂为无头型,尾囊发达。成熟的畸形细胞(受寄生日龄6天)表面密布微绒毛,细胞内部高尔基体丰富,内质网发达,细胞核多分支。在高尔基体的两侧和细胞膜附近分布了大量的分泌小池。     

Novel surface specialization on a sea anemone egg: “Spires” of actin-filled microvilli

The ultrastructure of the “spiny” surface of Tealia crassicornis eggs is examined in detail by scanning and transmission electron microscopy in order to understand its function. Long microvilli are clustered together in spiral aggregates of 50–75 microvilli called “spires.” There are about 15,000 spires per egg. Dense bundles of microfilaments making up the cores of these microvilli are shown to be composed of actin by staining with the fluorescent dye nitrobenzoxadiazole (NBD)-phallacidin. It is postulated that the bundles of actin and the spires of microvilli are stiff and provide reinforcement to the egg surface. Such postulated properties would provide physical protection for these large eggs which, unlike the eggs of most invertebrates, appear to lack all extracellular investing coats.     

不同生境源的稻飞虱卵寄生蜂对寄主的选择和寄生特眭

稻飞虱重要卵寄生蜂缨小蜂Anagrus flaveolus、A optabilis和寡索赤眼蜂Oligosita aesopi、O.Naias均能在稻田和稻田周围的非稻田生境中生存。而.Ftaveolus为优势种。不同生境来源的卵寄生蜂有着不同的寄生和选择特性。缨小蜂A.Flaveolus能在飞虱科内转换寄主,但需1～2代的适应期。寄主卵对寡索赤眼蜂O.Aesopi的寄生有较大的影响,用褐飞虱和黑尾叶蝉诱集的O.Aesopi呼;不能交叉寄生。稻田内诱集的寄生蜂选择稻飞虱,而杂草地中诱集的缨小蜂则对飞虱T.Pusanus有一定的选择性。非稻田生境对保护稻飞虱卵寄生蜂有很大的作用,但对其寄生特性有较大的影响。     

Egg rejection behavior in a population exposed to parasitism: Village Weavers on Hispaniola

In contrast to African Village Weavers (Ploceus cucullatus)that are parasitized by Diederik Cuckoos (Chrysococcyx caprius),introduced weavers on Hispaniola existed without parasitismfor at least 2 centuries until the arrival of the Shiny Cowbird(Molothrus bonariensis) in the 1970s. Cruz and Wiley (1989)found that Hispaniolan weavers had a lower rejection rate offoreign eggs than African populations. Subsequently, Robertand Sorci (1999) and Lahti (2005, 2006) found that acceptanceof dissimilar eggs is not characteristic of the species throughoutits Hispaniolan range. In 1999–2002, we studied egg rejectionin Hispaniolan weavers on a broad regional scale. Rejectionincreased as experimental eggs became increasingly differentfrom the host eggs. Rejection rates for mimetic eggs, differentcolor eggs, different-spotting eggs, and cowbird eggs was 23.2%,33.3%, 61.5%, and 85.3%, respectively, with higher rejectionof cowbird eggs in areas where cowbirds were observed. Althoughrejection is likely to have a genetic component, the differencescould be due to phenotypic plasticity. Plasticity in egg rejectionmay be expected, given the potential cost of rejection and thespatiotemporal distribution of cowbirds. Thus, egg rejectionhas not necessarily decreased in Hispaniolan weavers, but itmay act in a plastic manner, increasing where cowbirds are present.     

ADAPTATIONS FOR COLD WATER SPAWNING IN LOLIGINID SQUID: LOLIGO GAHI IN FALKLAND WATERS

Inshore spawning sites of the cold water squid Loligo gahiwere found in the waters of East Falkland (Southwest Atlantic),where there is a major fishery based on this species. Egg massesoccurred in algal beds, often at the outer (seaward) edge, with ambientwater temperatures of 6.5-90C and salinity 33.75- 33.58. They wereattached to the stipes of the kelp algae Lessonia spp. and Macrocystispyrifera from 0.5 m to 2.5 m off the bottom at 8-20 m depths.The overall density of egg masses was low. The egg mass is abundle of elongated gelatinous translucent capsules with eachcapsule firmly attached to the kelp stipe at its basal end.The capsules are mainly 50-60 mm in length and contain an averageof 70 fertilized eggs. Sampled egg masses consisted of 4-161 capsulesand from 138 to 11,487 eggs. Large egg masses (. 50 capsules) wereapparently formed by several females at different times, as embryosin different capsules were at various stages of development.Eggs laid in winter are significantly larger than those laidin summer. In comparison with tropical and temperate Loligo spp.L. gahi have short egg capsules containing a small number of eggs,but the eggs (2.2-2.5 mm diameter) and hatchlings (3.1-3.4 mm mantlelength) are large. These are probable adaptations for cold waterspawning and development. (Received 30 March 2000; accepted 5 June 2000)     

Clutch detachment in a copepod after capture by a predator

When the egg-carrying copepod, Eudiaptomus gracilis, is capturedby larvae of predatory Chaoborus species (C.obscuripes or C.flavicans)in laboratory experiments, the external egg clutch detachesin 16-29% of caw, thereby allowing the eggs to escape from ingestion.Clutch detachment may be due to active removal by the femalebefore she is eaten or the result of accidental loss by thepredator during handling. Detached clutches were significantlylarger than thase that were ingested along with the female.Clutch detachment is advantageous to the female since ingestedeggs are lost, whereas detached eggs hatch normally and maypotentially propagate the genotype. Chaoborus predation maytherefore influence the evolution of clutch size and the degreeof iteroparity in Eudiaptomus.     

MORPHOLOGICAL DIVERGENCE AND EVIDENCE FOR REPRODUCTIVE ISOLATION IN LITTORINA SAXATILIS(OLIVI) IN NORTHEAST ENGLAND

Current work at Old Peak (Ravenscar) on the northeast coastof England indicates that boulder-dwelling Lutonna saxatilis(Olvi) comprise at least two distinct forms, inhabiting high-and mid-shore boulders Using multivariate morphometrics we showthat these forms are significantly different in shape. Rareintermediates between these two distinct forms were occasionallyfound, usually with the low shore animals The two forms showdifferent reproductive strategies. High shore females (L. saxatilisH) mature at a smaller size and produce a smaller number oflarge eggs giving rise to large crawlaways The mid-shore form(L. saxatilis M) matures at a larger size and produces a largenumber of small eggs which give rise to small crawlaways. Anovel observation is that intermediate females (L. saxatilisI) contain eggs of both sizes, giving rise to a bimodal distributionof egg sizes within the brood pouch. The usual incidence ofabortion (observed in H and M forms) is Very low (<1%) However,in the intermediates the large eggs showed a high incidenceof abortion (about 60%) and the incidence of abortion in thesmall eggs was also increased (about 30%) Thus there appearsto be a partial reproductive barrier between the two forms,presumably resulting in reduced fitness due in the intermediatesto reproductive dysfunction. These findings extend to othershores in the region, over total distance of about 66 km. Thefacts are suggestive of a hitherto unrecognised reproductivebarrier with L. saxatilis, the nature and strength of whichis under investigation ^*Present address: University College Scarborough. Filey Road.Scarborough Yo11 3AZ. (Received 12 June 1995; accepted 15 September 1995)     

Extra‐mitochondrial localization and likely reproductive function of a female‐transmitted cytochrome c oxidase subunit II protein

Our previous study documented a reproductive function for the male‐transmitted mitochondrial DNA (mtDNA)‐encoded cytochrome c oxidase subunit II (MCOX2) protein in a unionoid bivalve. Here, immunoblotting, immunohistochemistry and immunoelectron microscopy analyses demonstrate that the female‐transmitted protein (FCOX2) is: (i) expressed in both male and female gonads; (ii) maximally expressed in ovaries just prior to the time of the annual fertilization event; (iii) displayed in the cytoplasm and more strongly in the plasma membrane (microvilli), vitelline matrix and vitelline envelope of mature ovarian eggs; and (iv) strongly localized to the vitelline matrix of some eggs just prior to fertilization. These findings represent evidence for the extra‐mitochondrial localization of an mtDNA‐encoded gene product and are consistent with multifunctionality for FCOX2 in eggs.     

Diapause in the calanoid freshwater copepod Eudiaptomus graciloides

The seasonal appearance and the intensity of diapausing-eggproduction in Eudiaptomus graciloides in five lakes of differentsize and trophic level were studied. In all lakes, diapausingeggs were produced in autumn. In the large mesotrophic lakeSelenter See, the population’s shift to the productionof diapausing eggs was more complete than in other lakes. Weexamined day length, temperature and food as proximate factorsfor the production of diapausing eggs with laboratory experiments.Eudiaptomus graciloides produced diapausing eggs in all treatments,but a significantly higher percentage of diapausing eggs wasfound under short day conditions except when algal food wasabundant and temperature was high. To investigate the adaptivesignificance of diapause in E. graciloides, we compared thesurvival of adult and juvenile at different temperatures forE. graciloides with Eudiaptomus gracilis, a sympatric speciesthat does not exhibit diapause. At 8°C, adult E. graciloidessurvived better than adult E. gracilis and exhibited reducedgut contents and accumulation of storage lipids, traits characteristicof adult diapause. Eudiaptomus graciloides nauplii did not reachthe copepodid stage at 6°C, but E. gracilis nauplii exhibitedhigh mortality and developed very slowly. We hypothesize thatadult diapause and production of diapausing eggs facilitatethe survival of E. graciloides during cold periods and enhancecoexistence with its congener, E. gracilis, in temperate zones.