Interacting effects of increased tannin levels on leaf-mining insects

Tannin-rich extracts were painted on leaves of Q. emoryi (Fagaceae) that contained first instar larvae of a leaf miner, Cameraria sp. (Lepidoptera: Gracillariidae, Agrifoliella group), to test the role of tannins in increasing parasitism, while controlling for changes in protein content and physical damage. Miners from leaves that were treated with tannins had higher rates of parasitism by hymenopterans, but decreased mortality from other causes. The negative and positive effects of tannins balanced since overall larval survivorship was equivalent for leaf miners on tannin-enriched and control leaves. The tannin-rich extract also affected larval development because pupal weight was decreased for leaf miners in treated leaves. Tannins can have both adverse and beneficial effects on these phytophagous insects.

---

Résumé Des extraits riches en tanins ont été étalés sur des feuilles de Quercus emoryi contenant des chenilles de ler stade de Cameraria sp., pour contrôler l'influence du tanin dans l'accroissement du parasitisme sans modifier la teneur en protéines ni provoquer de dommages physiques. Les mineuses de feuilles traitées avaient des taux plus élevés de parasitisme par les hyménoptères, mais une diminution des autres causes de mortalité. Les effets négatifs et positifs des tanins se sont équilibrés, puisque la survie des mineuses était la même pour les feuilles traitées que pour les témoins. Les extraits riches en tanin ont agi sur le développement larvaire puisque le poids des chrysalides des mineuses de feuilles traitées était plus faible. Les tanins peuvent ainsi avoir des effets nuisibles et bénéfiques sur ces insectes phytophages.

     

Respiration Rate of Steinernema feltiae Infective Juveniles at Several Constant Temperatures

Respiration was measured in dauer stages of the insect-parasitic nematode Steinernema feltiae (= Neoaplectana carpocapsae) at 7, 17, and 27 C. Respiration, Q₁₀, and nematode viability were temperature dependent. Mean O₂ consumption for 5 × 10⁵ nematodes the first 24 hours was 0.27 ml at 7 C, 0.83 ml at 17 C, and 2.68 ml at 27 C. The Q₁₀ was 3.10 for 7-17 C and 3.24 for 17-27 C. Some nematodes died during 2, 14, and 21 days at 27, 17, and 7 C, respectively. The respiratory quotient was below 1 at all temperatures tested. A standard asymptotic model is expressed as oxygen consumed = 2.77 * {1 - exponent[-time * exponent(-B + C * temperature)]}; where 2.77 is the maximum response at 27 C. This model estimates nematode O₂ consumption and viability at storage temperatures between 7 and 27 C. The nematodes died when the O₂ concentration reached 0.5 ml/5 × 10⁵ nematodes. This model may be used to predict O₂ requirements of S. feltiae infective juveniles when stored as a waterless concentrate.     

人体急性缺氧性意识障碍

实验分为低压组(低压舱7,000米)与常压组(吸入7.6％低氧混合气),每组受试者各为12名,有7名参加了两组实验。每组各有4名平均经15分23秒发生了意识模糊或丧失(通称意识障碍)。障碍者的肺泡氧分压为29.9±0.8mmHg。障碍发生前,呈现严重无力,觉醒度降低,反应迟钝,脑波特征是高幅6波(100-300μV)占优势。障碍发生时,高幅δ波丧失节律,幅度衰减,波型不规则,额枕失同步;呼吸循环代偿功能增强程度明显高于障碍前。本工作对于预测和评价人体急性缺氧引起的意识障碍有意义。     

Differential winter mortality and seasonal selection in the polymorphic ladybird Adalia bipunctata (L) in the Netherlands

Seasonal selection acting on the melanic polymorphism in the two-spot ladybird Adalia bipunctata was investigated in The Netherlands. An increase in melanic frequency over the spring-summer reproductive period was quantified. The selective advantage gained by melanics averaged 9%, but significant heterogeneity occurred between populations. Adult hibernation behaviour is described. The beetles when outdoors show a highly clumped distribution both between and within trees. The distribution of the morph classes between aggregations is random. Survivorship in a hibernating cohort (initial n= 1898) on a grid of 70 lime trees near Utrecht was monitored by making three counts over the winter of 1981–1982. Intense selection favouring each melanic morph occurred during December and January. The relative fitness of non-melanics was 0.55 (melanics =1). The discovery of dead beetles in late January (about 5% of total losses) and the absence of spatially density-dependent mortality were consistent with a climatic stress rather than selective predation. The period of selection was associated with very cold temperatures averaging up to 4°C below normal and an overall mortality of nearly 75%. There was no change in morph frequency, near normal temperatures and a lower mortality from February to early April. Examination of groups of nearby trees in late January strongly suggested that similar differential mortality had occurred except on some willows. This difference was probably due to the more protected hibernation sites available on these trees. Samples of hibernating cohorts at three other sites showed no evidence of differential mortality. Laboratory experiments with hibernating beetles found no difference in survivorship or rate of weight loss between starved non-melanics and melanics in temperature regimes with and without periods of adult activity. It is concluded that the intense winter selection on the study limes is probably exceptional. Examination of changes in morph frequency through the annual cycle suggests that at some sites the selection favouring melanics during reproduction is counterbalanced by selection against melanics in late summer or early autumn. The results are discussed in relation to mathematical models of cyclical selection and to other field studies including that of Timoféeff-Ressovsky (1940), who found large decreases in melanic frequency during hibernation in Berlin.     

Dose dependent responses of cattle to Theileria parva stabilate

Dolan T. T., Young A.S., Losos G.J., McMillan I., Minder Ch.E. and Soulsby K. 1984. Dose dependent responses of Theileria parva stabilate. International Journal for Parasitology14: 89–95. A tick derived stabilate of Theileria parva (Maguga) was titrated in a large group of Boran (Bos indicus) cattle of the same age, sex and origin. The infectivity data was analysed using the independent action model. The cattle were identified as heterogeneous in their response to infection with 75% showing one ID₅₀ (0.0014) and 25% showing another (0.01). The disease responses of the cattle given different dose levels were compared for a variety of parameters. The results obtained showed these parameters to be dose dependent including the time to onset of piroplasm parasitaemia. The stabilate is of large volume and can be used for controlled challenge in immunity studies and for comparison of susceptibility between cattle of different breeds and from different epidemiological backgrounds.     

Life-history characteristics of a wild population of vervets (Cercopithecus aethiops sabaeus) in Barbados,West Indies

Life history data are presented for a population of vervets, Cercopithecusaethiops sabaeus, in Barbados, West Indies. The data were obtained from two habituated troops and from vervets captured during a large-scale trapping program. Individuals of known age from one troop were weighed periodically, and separate growth curves generated for males and females. The mean weight of captured adult females was 3.3 kg; that of adult males, 5.3 kg. The average age at sexual maturity is estimated at 34 months for females and 60 months for males. Vervets give birth throughout the year, but most infants are born between April and July. The average interbirth interval following a surviving infant is 11.8 months. The mortality of juveniles is heaviest between birth and 2 years of age and decreases thereafter. Males emigrate from their natal troops at sexual maturity and one incident of a juvenile female emigrating is reported.     

Dependent competing risks: a stochastic process model

Analyses of human mortality data classified according to cause of death frequently are based on competing risk theory. In particular, the times to death for different causes often are assumed to be independent. In this paper, a competing risk model with a weaker assumption of conditional independence of the times to death, given an assumed stochastic covariate process, is developed and applied to cause specific mortality data from the Framingham Heart Study. The results generated under this conditional independence model are compared with analogous results under the standard marginal independence model. Under the assumption that this conditional independence model is valid, the comparison suggests that the standard model overestimates by 4% the effect on life expectancy at age 30 due to the hypothetical elimination of cancer and by 7% the effect for cardiovascular/cerebrovascular disease. By age 80 the overestimates were 11% for cancer and 16% for heart disease. These results suggest the importance of avoiding the marginal independence assumption when appropriate data are available — especially when focusing on mortality at advanced ages.     

INCIDENTAL MORTALITY OF NORTHERN SEA LIONS IN SHELIKOF STRAIT, ALASKA

The incidental catch of northern sea lions ( Eumetopias jubatus ) in the walleye pollock ( Theragra chalcogramma ) joint-venture fishery in Shelikof Strait, Alaska, was studied during 1982–1984 to assess the nature and magnitude of the catch. Data were obtained by placing U.S. observers on foreign processing vessels. Dead sea lions recovered from trawl nets were counted, sexed and measured, teeth were removed for age determination by dental laminae; and stomach contents were analyzed. Although the fishery has continued to expand both in number of boats and estimated total catch (74,136 metric tons [t] in 1982 to 171,539 t in 1984), the estimated incidental catch of northern sea lions has declined (ranging from 958 to 1,436 in 1982, 216 to 324 in 1983 and 237 to 355 in 1984). Of the sea lions processed, 73 percent were caught between 2000 and 0500 h, probably during net retrieval. Most caught sea lions were females ranging in age from 1–25 yr with a mean age of 6.43 yr; 79 percent of the females were sexually mature and probably part of the reproducing population. Males had a mean age of 4.8 yr and only 12 percent were old enough to obtain and defend territories. Analysis of stomach contents showed that the sea lions consumed pollock the same size as that taken by the commercial fishery. The impact of the incidental catch on the Gulf of Alaska sea lion population is unknown.     

Bionomics ofTrioxys indicus [Hym.: Aphidiidae], a parasitoid ofAphis craccivora [Hem.: Aphididae]: 31. Effect of host haemolymph on the numerical response of the parasitoid

The influence of kairomones on the numerical response of the parasitoidTrioxys indicus against its hostAphis craccivora at its varying density was studied. The kairomones (applied as aqueous extract of the host) significantly enhanced the rate of parasitisation and multiplication and the area of discovery of the parasitoid and also the K-values of mortality of the host at all parasitoid densities introduced (1, 2, 4, 8, 12 and 16 parasitoids) into troughs having about 200 hosts. The sex-ratio of F₁ offspring decreased at lower parasitoid densities and remained more or less unchanged at higher parasitoid densities after the application of kairomones. The present findings indicate that if kairomones are applied properly, the number of hosts destroyed by a stimulated parasitoid will be about 200, twice the number reported earlier, thus fewer parasitoids will be needed to regulate an estimated population of the hosts.      

Reproductive ecology of three ocypodid crabs II. Incubation sites and egg mortality

Mortality of eggs during incubation was estimated for three ocypodid crabs,Scopimera globosa, Ilyoplax pusillus andMacrophthalmus japonicus, and the influence of incubation sites was discussed. These crabs all lived in isolated burrows and fed on sediments during day time low tide.S. globosa andI. pusillus inhabited the upper intertidal sandflats, whereasM. japonicus inhabited the lower intertidal mudflats. Females of bothS. globosa andI. pusillus remained in their plugged burrows without feeding throughout incubation and the mortality of eggs was low despite large broods relative to body size. On the other hand, females ofM. japonicus fed actively on surface mud during incubation and the mortality of eggs was high despiite small broods relative to body size. InS. globosa andI. pusillus, the ovaries of ovigerous females were small until egg-hatching, whereas inM. japonicus, the ovaries grew rapidly during incubation and females were able to produce consecutive broods. I conclude that incubation of eggs in burrows may be advantageous in species which inhabit the upper interidal sandflats, even though the crabs cannot forage during incubation, since otherwise their eggs would be exposed to strong heat stress and desication during the summer. Furthermore, such species may produce few large broods because of less frequent interruption of feeding than that associated with production of many small broods.