核型多角体病毒感染对棉铃虫幼虫同类相残行为的影响

在室内研究核型多角体病毒（HaSNPV）感染对棉铃虫Helicoverpa armigera（Htibner）幼虫同类相残行为的影响。结果显示：感病棉铃虫随感病程度的加重,越容易被健康棉铃虫残食,而自然死亡的感病棉铃虫、冻死的感病棉铃虫和冻死的健康棉铃虫三者被健康棉铃虫残食的百分率无显著差异。表明感病棉铃虫和病虫尸体更易于被健康棉铃虫残食,是由于棉铃虫体力减弱而失去反击能力,不是由于病毒本身的影响。以健康棉铃虫、感病棉铃虫为残食者,冻死的病虫为被残食者,相残率无显著差异,表明病毒并未改变棉铃虫残食同类的天性。残食病虫的健康棉铃虫的化蛹率和羽化率均低于正常的健康棉铃虫,残食者为相残行为付出了很高的代价。     

Effects of spatio-temporal intervals between newly-hatched larvae on larval survival and development inMonochamus alternatus (Coleoptera: Cerambycidae)

The effects of distance between hatching larvae on survival and development were investigated inMonochamus alternatus. Two newly-hatched larvae were inoculated intoPinus densiflora bolts at a distance of 2.5 cm or 10 cm, simultaneously or at an interval of 2 weeks. Some larvae were inoculated singly as a control. When larvae were inoculated simultaneously, mortality of the closely-inoculated larvae was significantly higher than that of distantly-inoculated larvae. Such high mortality was identified as due to conspecific bites. When the two larvae were inoculated asynchronously, the first-inoculated larvae killed some second-inoculated larvae but were never killed by them. Consequently, mortality was higher in second-inoculated larvae than in first-inoculated larvae. In particular, there was a significant difference in mortality between them when the larvae had been inoculated closely. The mortality of second-inoculated larvae was higher in the closely-inoculated group than in the distantly-inoculated group although there was no significant difference between them. In the case of two simultaneously-inoculated larvae, the initial distance between them had no significant effect on the development and growth in the early larval stage. When the larvae were inoculated asynchronously, the first-inoculated larvae grew more quickly than singly-inoculated control larvae.     

二化螟滞育幼虫的蛋白和核酸含量以及保护酶活性的变化

为了阐明二化螟Chilo supprressalis滞育幼虫的分子特征及滞育期间保护酶活性的变化规律, 本研究应用Trizol法、 总量DNA提取法和蛋白定量试剂盒, 测定了在长光周期16L∶8D和25℃下发育的非滞育老熟幼虫、 在短光周期12L∶12D 和25℃下诱导滞育51 d的幼虫（称为滞育0个月）、 滞育1, 2和3个月幼虫的核酸含量和总蛋白含量; 同时应用试剂盒测定了老熟幼虫、 滞育0, 1和2个月的二化螟幼虫5种保护酶（POD, CAT, SOD, LDH和ATP酶）的活性。结果表明： 滞育幼虫的总RNA含量显著低于非滞育的老熟幼虫（P<0.05）, 而滞育1, 2和3个月的幼虫之间没有显著差异（P≥0.05）。老熟幼虫的总DNA含量显著高于滞育幼虫（P<0.05）。老熟幼虫的RNA/DNA比值较低, 滞育幼虫的RNA/DNA比值较高, RNA/DNA比值随着滞育时间的推移呈现出先上升后下降的趋势。滞育期大于1个月的幼虫中蛋白含量均显著高于非滞育的老熟幼虫（P<0.05）, 而滞育1, 2和3个月的幼虫之间没有显著差异（P≥0.05）。二化螟幼虫体内5种保护酶活性随发育阶段不同而存在差异。滞育幼虫中POD, CAT和SOD的活性随滞育时间延长而逐渐增强, 滞育2个月幼虫中的活性最高, 而非滞育老熟幼虫中的活性最低; LDH和ATP酶的活性则相反, 非滞育老熟幼虫中的活性最高, 滞育2个月幼虫中的活性最低。这些结果说明, 总RNA和DNA含量降低、 RNA/DNA比值先升后降、 总蛋白含量升高以及保护酶活性的变化是二化螟幼虫滞育过程中的主要生理特征。     

Larval competition for food between wild and hatchery-reared ayu, Plecoglossm altivelis Temminck et Schlegel, in culture ponds

To examine the larval competition between wild and hatchery ayu in the culture ponds, mixed rearing of 580 000 wild and 520 000 hatchery larvae was carried out in two 25-m³ ponds for 3 months, in contrast to the control in which 860 000 wild larvae were reared in another pond.
The number of wild larvae in the mixed-rearing treatments decreased rapidly 20 days after the start of mixed rearing, in contrast to hatchery larvae. Mortality of wild larvae was almost 100% at the end of the experiment (3 months), while the hatchery larvae showed the usual survival rate of 15–16%. In the control pond, however, 16% of the wild larvae survived. The wild larvae grew much slower (0.10mmday ^-1) than the hatchery larvae (0·26 mm day ^-1) in the mixed-rearing ponds, whereas the wild larvae in the control pond showed almost the same growth rate (0·24 mm day ^-1) as hatchery larvae. On day 6 the gut fullness of wild larvae was only 30% of that of the hatchery larvae in the mixed-rearing experiments. On day 46 the wild larvae occurred deeper in the mixed-rearing ponds than the hatchery larvae. This depth difference in vertical distribution appeared to cause a disadvantage for the wild larvae in the competition with hatchery larvae, since the food was supplied at the surface. Thus, the wild larvae starved and died.     

Dispersal of first-instar gypsy moth larvae in relation to population quality

Summary Field studies of dispersal by first instar gypsy moth larvae indicate that almost all larvae undergo an initial dispersal episode. However, in laboratory studies large larvae (from large eggs) disperse more frequently than small larvae (from small eggs) in the presence of favored food. Large larvae may be better adapted for dispersal. When larvae encounter unacceptable food or are denied food, larvae disperse more frequently and dispersal by small larvae is nearly as frequent as dispersal by large larvae. Factors affecting egg size may contribute to shifts in dispersal patterns of gypsy moth larvae and distribution of populations.Paper No. 2041, Massachusetts Agricultural Experiment Station, University of Massachusetts at Amherst. This research supported (in part) from Experiment Station Project No. 355     

草地螟滞育幼虫的蛋白和核酸含量变化

为了阐明草地螟Loxostege sticticalis 滞育的分子调控基础, 本研究应用Trizol法、 DNA和蛋白质定量试剂盒、 SDS-PAGE电泳技术分别对进入滞育1, 2, 3和4个月、 解除滞育以及非滞育草地螟老熟幼虫中的核酸含量、 总蛋白含量和组分的变化进行了测定。结果表明： 滞育不同月份幼虫的总RNA含量显著低于非滞育幼虫的总RNA含量（P＜0.05）; 解除滞育幼虫的总RNA含量显著高于滞育2, 3和4个月的幼虫, 但仍显著低于非滞育的对照组。滞育不同月份、 非滞育以及解除滞育幼虫的总DNA含量没有显著差异（P＞0.05）。RNA/DNA比值随滞育的开始而显著下降, 随着滞育的结束而显著上升。滞育不同月份的幼虫总蛋白含量显著高于非滞育幼虫的总蛋白含量（P<0.05）, 但解除滞育与非滞育幼虫的总蛋白含量无显著差异。利用SDS-PAGE电泳分析发现滞育幼虫体内存在滞育关联蛋白, 蛋白条带在24 kDa左右, 但非滞育和已经解除滞育的幼虫则没有该蛋白条带。这些结果表明, 总RNA含量的降低、 RNA/DNA比值下降、 总蛋白含量的升高, 以及24 kDa蛋白的存在是草地螟幼虫滞育的主要生理特征。     

高效液相色谱法检测菜蛾绒茧蜂幼虫体内多杀菌素残留

应用高效液相色谱法检测施用于寄主幼虫的多杀菌素可否传递到在其体内发育的寄生蜂幼虫。以对多杀菌素高抗的小菜蛾Plutella xylostella幼虫作为菜蛾绒茧蜂Cotesia plutellae的寄主,待绒茧蜂发育到1龄幼虫时,将浓度为50 mg/L的多杀菌素点滴到寄主幼虫背板上,随后让寄主幼虫取食经50 mg/L多杀菌素处理过的甘蓝叶片,寄主幼虫和其体内的蜂幼虫再发育3天后,将寄主幼虫解剖取出蜂幼虫,用高效液相色谱法对经多杀菌素处理的小菜蛾幼虫体液以及绒茧蜂幼虫匀浆液进行检测,结果多杀菌素的2个活性成分spinosyn A和spinosyn D均被检测到,两者的多杀菌素残留浓度分别是2.79 mg/L和0.94 mg/L。这表明,通过寄主幼虫体壁接触和取食进入其体内的多杀菌素,可通过寄生蜂幼虫体壁浸透、蜂幼虫对寄主血淋巴的取食,或这两种途经一起进入蜂幼虫的体内,对蜂幼虫产生作用。     

Cocoon-spinning larvae of Oriental fruit moth and Indianmeal moth do not produce aggregation pheromone

1 Mature larvae of the Oriental fruit moth (OFM) Grapholita molesta (Lepidoptera: Tortricidae) and the Indianmeal moth (IMM) Plodia interpunctella (Lepidoptera: Pyralidae) leave their food source in search of suitable pupation sites in which to spin cocoons. These sites are typically well-concealed cracks and crevices within the environment. Such cocooning behaviour is also observed in larvae of the codling moth (CM) Cydia pomonella (Lepidoptera: Tortricidae), which aggregate prior to pupation in response to a pheromone blend produced by cocoon-spinning conspecific larvae.
2 In laboratory experiments, we tested whether cocoon-spinning OFM and IMM larvae produce aggregation pheromones and whether CM larvae are cross-attracted to closely-related OFM larvae.
3 Fifth-instar OFM and IMM larvae were not attracted to, or arrested by, cocoon-spinning conspecifics. Moreover, fifth-instar CM larvae were not cross-attracted to either cocoon-spinning OFM or IMM larvae.
4 Analyses of volatiles released from cocoon-spinning OFM and IMM larvae revealed that both OFM and IMM lack components that are present in the aggregation pheromone of CM larvae. This information may help explain why CM larvae are not cross-attracted to cocooning OFM or IMM larvae.     

Larviposition in the ovoviviparous blowfly Calliphora dubia

This study examined larviposition in Calliphora dubia Macquart (Diptera: Calliphoridae), an ovoviviparous blowfly of considerable forensic importance in Australia. Females in the field carried 22–83 live larvae, exhibiting a strong linear relationship between female size and the number of live larvae carried. Females took just over 1 min (mean 67.7 ± 7.7 s, n = 54) to larviposit live larvae on or near fresh liver in the laboratory. Females laid larvae at a mean rate of 1.2 ± 0.1 larvae/s, with the fastest rate being 3.4 larvae/s. Most females (70%) laid live larvae only, but 14% laid larvae and eggs at the same time and 16% laid eggs only (none of the eggs laid were viable). Females laying only live larvae laid a mean of 53.7 ± 2.3 larvae, whereas those laying only eggs laid a mean of 48.6 ± 2.8 eggs on each occasion. None of the eggs laid were viable. Most females (86%) laid all their larvae in a single spot, even if they engaged in several bouts of laying live larvae. Nearly one‐third of females did not lay all the live larvae in their ovisacs, but retained half of their complement of developed larvae. Females may be opting to spread their larvae across several carcasses in order to increase their survival and not to overcrowd small, ephemeral carcasses. The fact that a blowfly can lay either eggs or live larvae has enormous implications for the accurate determination of the post‐mortem interval (PMI) as the presence of larvae derived from eggs laid on the body add 6–18 h to the PMI. This paper represents the first report of the ability of female calliphorids to resorb some of their own live larvae.     

The possible contribution of pituitary hormones to the heterochronic development of gonads and external morphology in overwintered larvae of Hynobius retardatus.

In Hynobius retardatus, most larvae in regions of low elevation metamorphose by autumn of the same year. However, larvae of some populations found in cold, mountainous ponds cannot metamorphose within the year and become aged, overwintered larvae. Gonadal development in larvae under the age of 1 year (larvae developed from eggs spawned in the same year) and in aged, overwintered larvae (spawned and hatched in previous years) was examined at the same developmental stage (stage 63, full-grown larval stage). The number of germ cells and the cross-sectional areas of the gonads were much larger in 2-season-overwintered (third year) larvae than in larvae under the age of 1 year.To obtain reliable probes for investigating the possible contribution of TSH, FSH and LH to metamorphosis and gonadal development, cDNAs for Hynobius TSHbeta, FSHbeta and LHbeta genes were cloned. Their expressions were analyzed by means of semi-quantitative RT-PCR in larvae under the age of 1 year and in 2-season-overwintered larvae. No differences were observed in expression levels of either TSHbeta or LHbeta between larvae under the age of 1 year and the overwintered larvae. In contrast, expression of FSHbeta was much higher in the overwintered larvae than in larvae under the age of 1 year. These results suggest that gonadal development proceeds gradually with age even in the overwintered larvae, but that metamorphosis is retarded, probably due to the larvae's cold habitat. Heterochronic development of gonads and external morphology has been demonstrated in H. retardatus, suggesting a potency for neotenic reproduction in this species.     

Ontogenetic- and condition-related effects of starvation on responsiveness in herring larvae (Clupea harengus L.) during repeated attacks by a model predator

The escape behaviour of fed and food-deprived herring larvae (20-30 mm SL) was studied during repeated attacks with a glass probe in order to investigate the causal mechanisms of starvation-induced changes in reaction to predators. Two experiments were set up: one where the fed and starved larvae were of the same age but of different sizes and one with groups of similar size but different ages. Biochemical and morphological condition measures described the condition of individual larvae. Starved larvae showed a lower responsiveness than fed larger larvae of the same age, and the responsiveness in this experiment decreased with decreasing nutritional status of the larvae. However, starved larvae that were of the same size but older than fed larvae showed a higher responsiveness, which could be explained by differences in development of sensory systems. A combination of condition and developmental factors thus explained the differences between starved and fed larvae. Both starved and fed larvae showed decreasing responsiveness over time with repeated attacks with no difference between starved and fed larvae in the relative change over time. The results emphasise the importance of taking into account individual age and/or development when the nutritional condition of wild-caught larvae is incorporated in survival models.     

Direct and indirect effects of predatory wasps (Polistes sp.: Vespidae) on gregarious caterpillars (Hemileuca lucina: Saturniidae)

Summary We examined how predation by vespid wasps,Polistes dominulus andP. fuscatus, affected the behavior, growth rate and survivorship of aggregated caterpillars ofHemileuca lucina (Saturniidae). Although these larvae can exhibit a variety of defense and escape behaviors, in general larvae reacted to wasp attacks by clinging to the hostplant. Neighboring larvae in the aggregation responded by leaving the feeding site and moving to the interior or base of the plant. To determine wheter wasp attack affected the behavior and growth of the caterpillars that escaped, a field experiment was conducted with treatments of: 1) larvae exposed to wasps, 2) larvae protected from wasps, and 3) larvae protected from wasps but with the attack of wasps simulated (=harassment). Over just one instar, protected larvae gained significantly more weight than the harassed larvae, which in turn weighed significantly more than the larvae that escaped the wasps. The behavior of attacked and harassed larvae differed from that of the protected larvae; the disturbed larvae often fed in smaller groups and in shaded portions of the plant where only mature leaves were available. A laboratory experiment showed that at 35° C (daytime temperature) larvae had significantly higher relative growth rates and significantly shorter instar duration than larvae reared at 25° C. Our results suggest that wasps, in addition to killing caterpillars, indirectly affect larval fitness by slowing larval growth, at least in part by forcing larvae into cooler microhabitats where leaves are of lower quality.     

Attraction to and learning from social cues in fruitfly larvae

We examined the use of social information in fruitfly larvae, which represent an ideal model system owing to their robust learning abilities, small number of neurons and well-studied neurogenetics. Focal larvae showed attraction to the distinct odour emanating from food occupied by other larvae. In controlled learning experiments, focal larvae preferred novel odours previously paired with food occupied by other larvae over novel odours previously paired with unoccupied food. When we gave groups of larvae a choice between food patches differing in quality, more larvae aggregated on the higher-quality food, suggesting that attraction to and learning about cues associated with other larvae can be beneficial. Furthermore, larvae were more likely to find the best available food patch in trials when that food patch was occupied by other larvae than in trials when that food patch was unoccupied. Our data suggest, however, that the benefits from joining others may be at least partially offset by the fitness costs of increased competition, because larvae reared in isolation did as well as or better than larvae reared in groups on three key fitness parameters: developmental rate, survival rate and adult dry body mass. Our work establishes fruitfly larvae as a highly tractable model species for further research on the mechanisms that modulate behaviour and learning in a social context.     

Physiological changes leading to anhydrobiosis improve radiation tolerance in Polypedilum vanderplanki larvae

High tolerance against various extreme environments exhibited by some anhydrobionts might be due to being almost completely desiccated, a state where little or no chemical reactions occur. We have shown that anhydrobiotic larvae of Polypedilum vanderplanki have higher tolerance against both high- and low-linear energy transfer (LET) radiation than hydrated larvae. It is of great interest to know how the desiccating larvae gain radiation tolerance. We therefore examined effects of high-LET radiation on four kinds of larvae: (1) normal hydrated (intact) larva, (2) intermediates between the anhydrobiotic and normal hydrated state, (3) almost completely dehydrated (anhydrobiotic) larvae, and (4) immediately rehydrated larvae that are assumed to have a similar molecular profile to anhydrobiotic larvae. The intermediates and immediately rehydrated larvae survived longer after high-LET radiation than intact larvae, indicating that radiation tolerance could be enhanced even in hydrated larvae. Physiological changes toward anhydrobiosis, e.g. accumulation of protectants or increasing damage repair capacity, correlate with improved radiation tolerance in hydrated larvae. In addition, almost complete desiccation further enhanced radiation tolerance, possibly in a different way from the hydrated larvae.     

Host immunity against newborn Trichinella spiralis larvae of different ages

The infectivity of newborn Trichinella spiralis larvae of different ages was studied in normal rats. Newborn larvae collected after incubation of adult worms in vitro for 2, 12, or 24 hr were injected intravenously (i.v.) into normal AO rats in 3 separate recipient groups. All recipient rats developed strikingly similar numbers of muscle larvae 20 days later. The susceptibility to immunity by newborn larvae of different ages was also studied. No difference was found when degree of protection was compared by assessing muscle larvae burden or peritoneal anti-newborn larvae effects after injection of newborn larvae of different ages either i.v. or intraperitoneally into immunized recipient rats. We conclude that newborn larvae of any age up to 24 hr have similar infectivity in normal rats and are equally susceptible to anti-newborn larvae immunity in vivo.     

Queens of the Paper Wasp Polistes fuscatus (Hymenoptera: Vespidae) Discriminate among Larvae on the Basis of Relatedness

The ability of queens of the paper wasp Polistes fuscatus to recognize larvae on the basis of colony origin was investigated in the laboratory. In a blind, binary choice paradigm, queens discriminated between larvae from their own colony and unrelated larvae, and between larvae from a sister colony and unrelated larvae. However, queens failed to discriminate between larvae from their own colony and larvae from a sister colony, indicating that queens of multiple-foundress colonies may lack the ability to make intracolonial brood discriminations on the basis of relatedness. These results demonstrate that recognition of larvae is mediated by larval-borne, genetically specified odors. Gas chromatograph/mass spectral analysis revealed that adults and larvae have similar cuticular hydrocarbon profiles, suggesting that the cues mediating larval and adult recognition may be the same.     

Differentiation of Paenibacillus larvae subsp. larvae,the cause of American foulbrood of honeybees,by using PCR and restriction fragment analysis of genes encoding 16S rRNA

A rapid procedure for the identification of Paenibacillus larvae subsp. larvae, the causal agent of American foulbrood (AFB) disease of honeybees (Apis mellifera L.), based on PCR and restriction fragment analysis of the 16S rRNA genes (rDNA) is described. Eighty-six bacterial strains belonging to 39 species of the genera Paenibacillus, Bacillus, Brevibacillus, and Virgibacillus were characterized. Amplified rDNA was digested with seven restriction endonucleases. The combined data from restriction analysis enabled us to distinguish 35 profiles. Cluster analysis revealed that P. larvae subsp. larvae and Paenibacillus larvae subsp. pulvifaciens formed a group with about 90% similarity; however, the P. larvae subsp. larvae restriction fragment length polymorphism pattern produced by endonuclease HaeIII was found to be unique and distinguishable among other closely related bacteria. This pattern was associated with DNA extracted directly from honeybee brood samples showing positive AFB clinical signs that yielded the restriction profile characteristic of P. larvae subsp. larvae, while no amplification product was obtained from healthy larvae. The method described here is particularly useful because of the short time required to carry it out and because it allows the differentiation of P. larvae subsp. larvae-infected larvae from all other species found in apiarian sources.     

Diel abundance, migration and feeding of fish larvae (Eleotridae) in a floodplain billabong

Eleotrid larvae (2.1–16 mm) were collected from surface waters of a billabong in south-eastern Australia. Estimates of larval density in plankton net samples at night averaged 148.3 larvae per m³ and 16.6 larvae per m³ during the day. In contrast, pump samples provided density estimates of 8.3 larvae per m³ at night and 0.9 larvae per m³ during the day. Larval densities did not differ between open water, snag (fallen tree) and Typha habitats, but Typha habitats yielded larger larvae than other habitats. 32.9% of larvae in pump samples were damaged and unmeasurable, creating a bias favouring larger larvae. The modal length of larvae in net samples at night was 5–6 mm, compared with 3–4 mm during the day, reflecting both greater net avoidance by larger larvae during the daytime and dispersal of smaller larvae from the surface at night. Dispersion patterns of larvae suggest that classes of larvae smaller than, and larger than 5.0 mm exhibit reciprocal diel vertical migration behaviour linked to ontogenetic changes in diet. Larvae less than 5 mm fed only during the day and preyed exclusively on rotifers, whereas larger larvae continued to feed at night and consumed mostly planktonic crustaceans.     

Nutritional condition of larval milkfish,Chanos chanos,occurring in the surf zone

In order to clarify the nutritional conditions of larval milkfish in the surf zone, the following parameters were examined: 1) DNA and RNA content and RNA/DNA ratio of fed and unfed larvae collected from the surf zone and reared in the laboratory; 2) survival rate of the unfed larvae; and 3) total length, otolith increment counts and RNA/DNA ratio of wild larvae collected daily from the surf zone. The DNA and RNA content of the unfed larvae decreased, but increased in fed larvae. The RNA/DNA ratio decreased in unfed larvae, whereas in the fed larvae it decreased for the first three days after capture and increased thereafter. These results indicated that the values of DNA and RNA content and RNA/DNA ratio could be used as an indicator of nutritional condition of milkfish larvae after 6 days of starvation. Although total length of the wild-larvae did not show serial changes, their otolith increment counts showed continuous increases, indicating that the larvae sojourned in the surf zone for several days. In the same period, RNA/DNA ratios of the wild larvae decreased continuously, the ratios of larvae with fewer otolith increment counts being relatively higher than those of larvae with greater increment counts. Based on these results, the milkfish larvae remaining in the surf zone were concluded as being under insufficient nutritional conditions.     

Alterations in the longevity and fecundity of adult Trichinella pseudospiralis related to method of isolation of infective larvae

The infectivity of Trichinella pseudospiralis infective larvae was reduced significantly following exposure to low pH or a combination of 1% pepsin at low pH compared to that for larvae isolated in phosphate-buffered saline (PBS) at pH 7.0. Reduction of host gastric pH by administration to mice of sodium bicarbonate solution in PBS was accompanied by an increase in the infectivity of larvae isolated in 1% pepsin/HCl (P/HCl) compared to that for worms inoculated into hosts given PBS alone. Fewer adult worms developing from larvae isolated in P/HCl became established in the host small bowel than was seen with larvae isolated in PBS; moreover, the fecundity in vitro of adult worms developing from P/HCl-isolated larvae was reduced below that for adults developing from larvae isolated from host muscle in PBS. More adult worms were recovered following infection of immune hosts with PBS-isolated larvae than were recovered from immune mice challenged with larvae isolated in P/HCl. Similar findings were observed in mice immunized by infection with Trichinella spiralis and challenged with T. pseudospiralis larvae isolated in either P/HCl or PBS. Immunization of mice with T. pseudospiralis larvae isolated by either method and challenged with larvae of T. spiralis resulted in recovery of similar percentages of the challenge inoculum.