Specific intra-tissue responses to manganese in the floating lamina of Trapa natans L

Plant tolerance to heavy metals requires morpho-physiological mechanisms that are still poorly understood, especially in hydrophytes. This study focuses on the young floating lamina of the rhyzophyte Trapa natans exposed for 10 d to 130 microM Mn. The lamina has the ability to bioaccumulate Mn (> 3000 microg g(-1)). X-ray microanalysis of Mn cellular distribution revealed accumulation in the upper epidermis, in the first palisade layer, and in the idioblasts of the spongy tissue, which were shown with electron microscopy to contain osmiophilic vacuolar deposits, also observed to a minor extent in the control leaves. On the basis of biochemical and histochemical tests, these deposits were attributed to phenolic compounds that were probably able to chelate Mn. Net photosynthesis, photosynthetic pigments, room temperature microspectrofluorimetric analyses, and ultrastructural studies of plastids were performed to evaluate the status of the photosynthetic apparatus. A greater development of thylakoid membranes was observed in plastids of the second palisade and spongy tissue, which, however, did not accumulate Mn. Only the spongy tissue experienced inadequate assembly of PS II, but this did not significantly influence the photosynthetic yield of the whole lamina. It was concluded that T. natans can optimise productivity in the presence of Mn by means of specific intra-tissue responses within the framework of the floating lamina.     

Population density and module demography in Trapa natans (Trapaceae), an annual,clonal aquatic macrophyte

The effects of population density on module demography were studied in Trapa natans L., an annual aquatic macrophyte capable of extensive clonal propagation. At low density, the floating plants produced ten times as many ramets (clonal offshoots) as those at high density. Module mortality occurred at three levels: leaf, ramet (shoot), and genet (genetic individual). There was 100-fold variation in the size of nuts containing germinable seeds. In early summer there was a highly significant linear relationship between dry mass of nuts and the total mass of ramets that each had produced. In early summer most (73–83%) of the variation in total plant biomass was attributable to variation in initial nut size. However the significance of initial nut size was diminished later in the season. The great success of the exotic weed T. natans at colonizing and monopolizing an aquatic habitat is a function of its highly productive clonal growth response to low-density conditions, combined with greater proportional allocation of biomass to reproductive structures, resulting in greatly increased nut production at low initial density. The species appears able to develop and maintain a population at extremely high density: plant buoyancy and the production of large, well-protected nuts allow rapid early growth from the sediment each year and early pre-emption of the water surface.     

Predation of frog eggs by the water strider Gerris latiabdominis Miyamoto (Hemiptera: Gerridae)

Water striders (Hemiptera: Gerridae) are predators found on the water surface that prey mainly on arthropods. The feeding on other organisms (dead vertebrates, fishes and tadpoles) is a rare event. To our knowledge, predation of frog eggs by water striders has not yet been reported. We observed that adult water striders, Gerris latiabdominis Miyamoto, 1958 (Hemiptera: Gerridae), preyed on the eggs of three frog species, Pelophylax nigromaculata Hallowell, 1861 (Anura: Ranidae), Rana japonica Boulenger, 1879 (Anura: Ranidae), and Rhacophorus schlegelii Günther, 1858 (Anura: Rhacophoridae). We found predation by the water striders affects the survival rate of frog eggs floating on the water surface. We suggest that this hunting event would occur in water bodies in which water striders and frogs coexist, especially the region where their phenology overlaps.     

Effects of oxygen level on metabolism and development of seedlings of Trapa natans and two ecologically related species

Seeds of the water plant Trapa natans L. (water chestnut) can germinate in strict anoxia. The seedlings show seminal roots growing upwards while shoot buds remain quiescent until O₂ becomes available. Trapa seedlings are highly tolerant to anoxia. The rate of ethanol fermentation was 21.2 μmol (g FW)⁻¹ h⁻¹, while production of lactate was negligible and lower than that of succinate. The seminal root of Trapa compares better to the rice coleoptile rather than to the rice root, both functionally and as to the metabolic response to anoxia. The anaerobic germination of Nuphar luteum L. and Scirpus mucronatus L. was also characterized by a limited developmental program.     

Spatial structure-mediated indirect effects of an aquatic plant, Trapa japonica, on interaction between a leaf beetle, Galerucella nipponensis, and a water strider, Gerris nepalensis

The spatial structure-mediated indirect effects of an aquatic host plant, Trapa japonica (Trapaceae), on survival of a leaf beetle, Galerucella nipponensis (Coleoptera: Chrysomelidae), with regard to predation by a water strider, Gerris nepalensis (Hemiptera: Gerridae), were investigated in an irrigation pond and under indoor conditions. Beetle density, particularly in the first-instar stage of the larvae, became extremely low in the second generation in the pond, even though food resources were abundant. The biological check method, which excludes natural enemies by caging, suggested that a causal factor of the low density was predation by Gerris nepalensis in midsummer and thereafter. Normally growing rosettes extend their leaves horizontally on the water surface. However, some rosettes of T. japonica grew leaves vertically in the later seasons, and such overgrown rosettes were distributed patchily in the ponds. Beetle density was higher on the latter rosettes than on the former ones. The indoor experiment showed that the water strider can feed on the eggs of beetles on normally grown rosettes but not on the overgrown rosettes. Furthermore, female adults of Galerucella nipponensis preferred the overgrown rosettes over the normally grown rosettes for oviposition when water striders were present. These facts suggest that the spatial structure-mediated indirect effects of the host plant modify the interaction between herbivore and predator. Received: November 22, 2001 / Accepted: February 26, 2002     

长期弱光对苦草幼苗生长发育的影响

用遮光法研究弱光(5%、1%、0.5%、0.1%全光照)对苦草幼苗生长发育的影响,统计了苦草的生物学参数,测定了叶片叶绿素荧光参数。结果表明:1)0.1%组无新株萌发,随着实验时间的延长其余组新株萌发逐渐被抑制。2)随着实验时间增加和光照强度降低,老株叶片形成受到的抑制程度呈增大趋势;前20d时新株叶片形成未被抑制,但随着实验时间延长显著被抑制。3)老株、新株的叶宽均受到显著抑制。4)老株叶片的伸长显著被抑制,且随着光强降低叶片伸长的幅度呈显著降低趋势;前20天时新株叶长被促进,随着实验时间延长叶片伸长显著被抑制。5)随实验天数的增加,老株叶片光化学最大量子产量(Fv/Fm)呈显著降低趋势,第80天时相对电子传递速率(rETR)和非光化学淬灭(NPQ)显著降低。6)新、老植株根、茎、叶的鲜重均显著低于对照,且随着光照强度降低老株的茎重/株重和根重/株重呈增加趋势,而叶重/株重呈显著的降低趋势。第80天时苦草植株仍具有一定的光合能力,地下茎的生物量比例较高,因此,≤1%全光照下苦草植株具有较强的耐受能力。     

幼虫密度对甜菜夜蛾生长发育与繁殖的影响

为了研究甜菜夜蛾Spodoptera exigua(Hübner)幼虫的密度对其发育及繁殖的影响,本实验观察了5种幼虫密度下（1,5,10,20,30头/瓶）,幼虫发育和成虫繁殖情况。结果表明：幼虫和蛹历期、存活率和蛹重均差异显著。幼虫和蛹历期均以20头/瓶的最短,1头/瓶的最长,其余随幼虫密度增加而延长;幼虫至蛹存活率以10头/瓶的最高,其余随幼虫密度增加而降低;1头/瓶的蛹最重,显著高于其他密度的,其余随幼虫密度增加而下降。尽管密度间成虫羽化率和产卵前期均无显著差异,但成虫产卵量、寿命和畸形率差异显著。1头/瓶的产卵量最多,其次为10头/瓶的,其余随幼虫密度增加而减少,30头/瓶的产卵量显著少于其他密度的; 密度在1～20头/瓶范围内,雌蛾寿命均较短,显著短于30头/瓶的,而雄蛾寿命以5头/瓶的最短,显著短于其他密度的（10头/瓶除外）,10头/瓶的次之,其余密度间差异不显著;不同幼虫密度下羽化的成虫畸形率差异显著,10头/瓶的最低,其余随幼虫密度增加而升高; 生命表结果表明甜菜夜蛾在10头/瓶下世代存活率和种群增长指数均最高,幼虫密度过低或过高均不利于种群增长;世代存活率（S）和种群增长指数（I）与幼虫密度之间的关系均呈抛物线关系：S =－0.2087x²+2.5694x+211.52 (R²=0.88),I=－0.0552x²+0.9166x+54.168 (R²=0.95)。结果提示幼虫密度影响甜菜夜蛾种群动态的重要生态因子之一。     

Conflict between sexes in the water strider, Gerris lacustris: a test of two hypotheses for male guarding behavior

We studied the effect of operational sex ratio on female reluctanceand male persistence to mate as well as on the length of copulationand postcopulatory guarding in Gerris lacustris by adding fivesurplus males or females to the basin with a pair in tandem.In the control treatment, a pair alone was tested. Accordingto the copulatory guarding hypothesis (CGH), males should prolongmating and guard females in the presence of surplus males. Accordingto the convenience polyandry hypothesis (CPH), females shouldshow lower levels of resistance to prolonged mating in the presenceof surplus males because the mating male protects the femaleagainst harassment from other males. As expected on the basisof both the CGH and CPH, mating (copulation + guarding) averagedlonger in the male-biased treatment. The behavior of males andfemales during mating suggested that both hypotheses hold true:females showed less resistance to prolonged mating (as predictedfrom CPH), and male behavior suggested stronger efforts to stayon the female when surplus males were present (as predictedfrom CGH). Comparisons of the treatment with surplus femaleswith the results from the mating pair without surplus individualssuggested that the capabilities of water striders in tandemto assess the sex of nearby nonmating striders are limited.     

四种食料植物对八字地老虎生长发育和繁殖的影响

研究了油菜、甜菜、白菜和莴苣 4种食料植物对八字地老虎Agrotisc nigrumLinnaeus幼虫发育历期、蛹期、蛹重、成虫寿命和产卵量的影响。幼虫取食油菜时发育历期最短 (1 5 4d) ,蛹最重 (2 0 3 5mg) ,产卵量最多 (3 89 5粒 ) ,甜菜次之。幼虫取食莴苣时发育历期最长 ,蛹最轻 (1 3 6 1mg) ,产卵量最少(1 44 7粒 )。 4种食料植物对寄主的蛹期和成虫的寿命没有显著的影响     

温度对小菜蛾生长发育和繁殖影响的研究进展

小菜蛾是典型的世界性害虫。本文综述了国内外有关温度对小菜蛾生长发育、存活、繁殖和种群增长等生物学特性影响的研究概况,提出了开展变温条件下小菜蛾生物学特性研究的重要性,这将有助于进一步弄清小菜蛾种群在田间自然条件下种群消长规律的内在机理,为利用当地的气象资料推测小菜蛾在某一时间段内的发生动态,确定防治适期,科学有效地指导防治提供理论依据。     

Effects of the availability of food and water on reproduction in the African army worm, Spodoptera exempta

ABSTRACT. Female Spodoptera exempta (Walker) (Lepidoptera: Noctuidae) moths require access to water to achieve hydration and maturation of their oocytes if they are to achieve their potential fecundity. For moths provided with water, the main factor limiting fecundity is moth weight. There is some evidence that sucrose in the adult diet can increase fecundity, particularly in lighter moths from a suboptimal larval feeding regime. Moths fed sucrose live longer, but complete oviposition at about the same age as moths provided only with water. Dietary protein and amino acids have no effect on fecundity or longevity. Although- multiple matings are frequent in the laboratory, female S.exempta only need to mate once to complete oviposition. Differences are apparent in the relative contribution of larval and adult feeding to reproduction in Noctuidae. Some species, like S.exempta , require only water to achieve their reproductive potential, while others (e.g. Heliothis spp.) are dependent on sugars in the adult diet. Female S.exempta denied access to water or food until night 3 after eclosion and then provided with water or sucrose, commence oviposition on night 4 and have fecundities comparable with those moths fed from emergence.     

Early development of the digestive tract of cod larvae, Gadus morhua L., during start-feeding and starvation

Cod larvae, Gadus morhua L., were reared in the laboratory and released to a large marine enclosure 4 to 5 days after hatching (6–8° C). The development of the digestive system was studied until day 24 after hatching. Morphological investigations of the jaw apparatus and the digestive tract showed that the larvae are able to absorb ingested food well before exhaustion of the yolk sac. The foregut, and especially the midgut, were particularly active in lipid absorption, and the hindgut was characterized by pinocytotic activity. Duhng the first days of feeding, no distinct prey organisms were observed in the gut, and signs of food absorption in the epithelial cells of the gut were sparse.A distinct red fluorescence, restricted to the hindgut, was observed from day 11 to day 19. On the basis of changes in absorptive pattern in the gut we suggest that changes in digestive and absorptive abilities, as well as in nutritional needs, take place around days 15–17 after hatching.
In starved larvae, signs of degeneration of the gut tissue were first visible in the foregut. By day 9 after hatching, microvilli was degenerated to such an extent that the ability to absorb food must have been severely restricted. If larvae are starved longer than this, they will probably not survive.     

Adaptive significance of wing dimorphism in the absence of dispersal: a comparative study of wing morphs in the waterstrider, Gerris remigis

ABSTRACT.

• 1 Gerris remigis Say (Hemiptera; Gerridae) is primarily apterous, but populations with up to 33% macropters have been reported. The macropters seldom fly, and field studies have revealed no detectable differences between wing morphs in movement or survival at any time of year.
• 2 In this paper, life history traits of macropterous and apterous G. remigis are compared in an attempt to determine the mechanisms responsible for the maintenance of macroptery in this species in spite of the very low flight capacity and infrequent flight of macropters.
• 3 Development time, proportion breeding without diapause, and overwinter survival do not differ between morphs. However, pre-diapause macropterous females have a significantly shorter pre-oviposition period than apterous females. In contrast, post-diapause macropters begin reproducing later than apters, and have a lower cumulative fecundity.
• 4 These results suggest that macropters may be at a selective advantage in warm habitats which favour pre-diapause reproduction, but that apters should be favoured in the preferred, cool, lotic habitats.
• 5 However, crossing and rearing experiments indicate that wing morphology is primarily environmentally controlled in this species, and that the heritability of wing morphology is low, at best. In light of this, the relative impacts of purely phenotypic (environmental) variation, random effects, and the observed fitness differences on the maintenance of macroptery in this species are discussed.

     

六种昆虫生长调节剂对葱蝇生长发育和繁殖力的影响

用灭蝇胺、氟铃脲等6种昆虫生长调节剂和对比药剂辛硫磷LC_40-50浓度处理葱蝇1龄和3龄幼虫,观察对其生长发育和繁殖的影响;并且研究了葱蝇成虫取食药剂对其繁殖力的控制效应。结果表明：6种药剂中除虫酰肼外,其余都对葱蝇幼虫发育历期、化蛹率、成虫产卵前期、成虫寿命、产卵量有很大影响,对其生长发育和繁殖表现出显著不利性。其中灭蝇胺和氟铃脲处理1龄幼虫后,存活幼虫的历期和成虫产卵前期各延长3天,化蛹率降低26.7%～30.0％,成虫寿命缩短22.3～24.3天,产卵量降低35.5％～49.9％;处理3龄幼虫主要导致产生畸形蛹,且正常羽化的成虫寿命降低18.0～20.67天,产卵量降低45.7%～57.8％。成虫连续取食用牛奶稀释的２ 000倍的药液,能导致产卵前期延长、产卵量减少、卵孵化率降低,幼虫死亡率极高,达95%以上。结果提示,利用成虫补充营养的特性,将灭蝇胺和氟铃脲等混入牛奶或糖水中诱集成虫取食,可有效降低成虫的繁殖力,有助于实现对葱蝇的无公害治理。     

Aspects of the reproductive biology of the bass, Dicentrarchus labrax L. II. Fecundity and pattern of oocyte development

The European bass, Dicentrarchus labrax L., in common with most temperate marine teleosts, exhibits a distinct seasonal reproductive cycle. Its reproductive strategy is characterized by a high absolute fecundity (2-25 × 10⁵), both absolute and relative fecundity increasing with size and age. The cyclic pattern of oocyte development has been determined by histology and from oocyte size frequency analysis. Results show that the bass exhibits group-synchronous oocyte development and is a 'fractional spawner', i.e. it spawns a number (3–4) of discrete clutches in quick succession, successive clutches containing fewer oocytes. All oocytes which are recruited into the secondary growth phase (> 110 μrn) are either spawned that season or become atretic, i.e. no secondary oocytes are held over for the subsequent reproductive season.     

Growth and morphological development of chub, Leuciscus cephalus (L.), during the first year of life

The growth and the morphological development of larvae and juveniles of chub, Leuciscus cephalus (L.), from a small stream of western Greece is described, based on field samples and laboratory-raised fish. In the laboratory, size hierarchy was developed and morphological differentiation occurred at a younger age in the fastest growing larvae. Growth was faster in the field and differentiation of fins and scales began at a larger size, but apparently at a younger age, than in the laboratory.     

Predator‐mediated phenotypic plasticity in tadpoles of the striped marsh frog,Limnodynastes peronii

Abstract We tested the phenotypic responses of larval striped marsh frogs (Limnodynastes peronii) to the odonate nymph predator, Aeshna brevistyla. When reared in the presence of dragonfly nymphs feeding upon conspecifics of L. peronii larvae the tadpoles showed a strong change in morphology. Morphological changes included an increase in total tail height, but also an unexpected marked change in head‐body shape. In addition, we examined how tadpole development, as well as mass and length at metamorphosis, was affected by exposure to dragonfly nymphs. Larval development of L. peronii was strongly influenced by exposure to the predatory behaviour of dragonfly nymphs. Predator‐induced tadpoles had significantly slower developmental rates than control larvae. Although metamorphs of non‐exposed L. peronii were approximately 33% lighter than predator‐exposed metamorphs and possessed lower jump distances, after adjusting for mass there was no difference in jump distance. The newly described morphological response may assist in more accurately relating morphological plasticity to fitness.     

Settlement and growth of the green mussel Perna viridis (L.) in coastal waters: influence of water velocity

Green mussels Perna viridis were observed to be a major foulant in the seawater intake tunnel of a coastal power station. Field experiments were carried out to ascertain what factors were responsible for the successful colonisation by mussels. Two adjacent stations (25 m apart) were selected, one representing the coastal waters and the other representing the intake screens (with higher water velocity). Gonadal activity, larval abundance, spat settlement and growth rate of the mussels were monitored at monthly intervals for a total period of two years. The results showed that the breeding activity of the mussels at the study area is influenced largely by temporal distribution of seawater temperature. However, ensuing larval availability in the coastal waters is more dependent on food availability. On the other hand, spat settlement and growth rate are predominantly influenced by water flow, probably as a result of increased propagule and food flux rate at higher water velocities. Higher water velocity at the intake screens also contributed to mussel dominance by preventing settlement of many potential competitors.     

The life-history traits of widespread freshwater fish species: the case of Roach Rutilus rutilus (Linnaeus, 1758) (Pisces: Teleostei) in water bodies at the southern limits of distribution

The Roach Rutilus rutilus (Linnaeus, 1758) (Pisces: Teleostei) is a widespread Eurasian cyprinid freshwater fish. Although numerous studies have investigated the species’ life history traits across its main native range of distribution, little is known from water bodies located beyond the southern limits of the latter, especially where the species has been introduced. Between July 2010 and April 2011, a total of 949 R. rutilus specimens was collected from Porsuk Reservoir (NW Turkey), and life-history traits of age, growth, fecundity and egg size were studied and compared to six other R. rutilus populations (including Caspian Roach R. r. caspicus) from the southern limits of distribution. The Porsuk population was characterised by relatively shorter lifespan, slower growth and lower fecundity. These findings support previous studies emphasising the importance of local environmental factors in shaping the life-history traits of widespread fish species. These must be taken into consideration especially in view of the potential value of R. rutilus as an economic resource for in-land fisheries.     

Multiple matings increase the fecundity of the yellow swallowtail butterfly,Papilio xuthus L., in summer generations

Females of the yellow swallowtail butterfly, Papilio xuthus,were reared in the laboratory. They were divided into four groups held under different mating conditions: nonmating (virgin) and mated once, twice, and three times. The number of eggs in the ovaries was counted by dissection. Virgin females produced increasing numbers of mature eggs, up to about 30, in the week following emergence. When the female had mated once, the number of mature eggs was significantly higher than that of virgin females by the second day after emergence. However, the double- and triplemated females did not increase the number of eggs in each state further than the singlemated females. The double-mated females deposited significantly more eggs than the singlemated females in the laboratory. The triplemated females also deposited more eggs on the day after the third mating than the doublemated females. Thus, multiple matings increased the number of eggs deposited. The change in the hatchability and the morphology of the spermatophore in the bursa copulatrix suggested that the sperm from the last mating had precedence.