Possible direct effect of diethylcarbamazine on the infective larvae of Brugia pahangi

The direct action of diethylcarbamazine (DEC) on the infective larvae of Brugia pahangi was studied. The larvae were cultured in RPMI 1640 supplemented with foetal bovine serum and antibiotics for 22 days. Most of the larvae remained alive for 8 days, but survival rate of larvae decreased rapidly from day 10 onwards. The larvae did not grow in the culture system. The addition of DEC did not affect the morbidity of the larvae and no difference was observed in the morphological characteristics between the larvae cultured in the presence or absence of DEC. The infective larvae were cultured in vitro for 5 days in the presence or absence of DEC, and inoculated into jirds. The animals were necropsied at intervals, and developing larvae and adult worms were recovered. When the larvae were cultured without DEC and then inoculated subcutaneously into jirds, 29.8% of the inoculum was recovered 3-15 days, and 25% 19-22 weeks, post-inoculation. However, when the larvae were exposed to DEC in vitro and inoculated into jirds, the rate of recovery was reduced to 25% 3-15 days post-inoculation and 2% after 19-22 weeks. When the control larvae cultured in vitro were inoculated intraperitoneally into jirds, 41.3% of inoculum was recovered 3-15 days, and 42.8% 19-22 weeks, post-inoculation. Again the corresponding value for larvae exposed to DEC in vitro was reduced to 19.8% 3-15 days, and 8% 19-22 weeks, post-inoculation. It was observed that the larvae exposed to DEC in vitro were retarded in their development in jirds.(ABSTRACT TRUNCATED AT 250 WORDS)     

投喂水平对长吻 仔稚鱼生长和存活的影响

以长吻(鱼危)仔鱼为实验对象, 探讨不同投喂水平对7-14日龄阶段和21-29日龄阶段的长吻(鱼危)仔稚鱼存活、生长以及鱼体组成的影响。7-14日龄阶段设计6个投喂水平, 分别为: 20、30、40、50、60和70 % IBW/d(IBW: initial body weight); 21-29日龄阶段设计6个投喂水平: 10、20、30、40、50、60 % IBW/d。实验结果表明: (1)投喂水平显著影响长吻(鱼危)仔稚鱼的存活和生长(P0.05)。7-14日龄阶段, 投喂水平为30%-60% IBW/d处理组的仔鱼存活率显著高于20%与70 % IBW/d投喂组(P0.05)。特定生长率随投喂水平的增加显著上升, 以60% IBW/d投喂组最高(P0.05)。21-29日龄期间, 10% IBW/d投喂组存活率显著低于50% IBW/d投喂组(P0.05), 特定生长率(SGR)则显著低于其他各处理组(P0.05); (2)鱼体体长体重变异系数未受投喂水平的显著影响。鱼体产出与饲料投入之比、鱼体水分含量随投喂水平升高显著下降(P0.05), 粗蛋白含量则显著上升(P0.05); 粗脂肪和粗灰分含量无显著差异; (3)分别通过存活率和投喂水平做一元二次回归、特定生长率与投喂水平做折线回归得到7-14日龄阶段的仔鱼最适投喂水平为43 % IBW/d; 通过仔鱼存活率和特定生长率与饲料投喂水平做折线回归得到21-29日龄阶段的仔鱼最适投喂水平分别为30.62% IBW/d和28.41% IBW/d。       

Fasciola hepatica and Paramphistomum daubneyi: field observations on the transport and outcome of floating metacercariae in running water

Experimental investigations in eight open drainage ditches and furrows from central France were carried out to analyse the dispersal of floating metacercariae of two digenean species by running water and to determine the outcome of larvae which settled on Nasturtium officinale (watercress). The frequencies of larvae found after their transport by water ranged from 33% to 49.7%, thus indicating that more than half of the metacercariae used in this experiment had fallen to the bottom of the water during this transport. The nature of the site (furrow, or ditch supplied by a spring) had a significant effect on the distribution of floating larvae, while the digenean species had no effect. Low percentages of metacercariae on watercress were noted in furrows (3.5-4.3% of larvae) and ditches (0.8-1.3%). When the watercress grew, most larvae that had settled on leaves and stems died but there were always several living metacercariae on this plant (0.7-1.5% of larvae for Fasciola hepatica and 0.2-0.5% for Paramphistomum daubneyi). The weak buoyancy of these floating cysts on running water limited their dispersal and, consequently, led to a real diminution of risks incurred by definitive hosts towards these metacercariae.     

Growth of Perca fluviatilis larvae fed with Artemia spp. nauplii and the effects of initial starvation

Experiments were performed to test the growth and survival of perch larvae fed with Artemia spp. nauplii and to determine the most advantageous time of first feeding. During a first experiment, perch larvae were divided into groups according to their hatching dates. Daily ingestion of Artemia spp. nauplii began significantly 2 days after mass larvae hatching. By day 7, the daily prey acceptance was over 75% among the separate larvae groups. During a second 14-day feeding experiment, larvae fed after a 2- or a 3-day delay showed the best growths: 12.5 mm and 13.7 mg. There was no significant difference (P > 0.05) among survival rates (85.3%) of perch larvae fed after a 1-, 2- or 3-day delay.     

Cryopreservation of first-stage and infective third-stage larvae of Strongyloides stercoralis

Infective third-stage larvae of Strongyloides stercoralis were frozen over liquid nitrogen and remained infective to dogs when thawed. Successful cryopreservation depended on a 30-60-min incubation in a cryoprotectant (10% DMSO and 10% dextran) before freezing and thawing the frozen larvae into RPMI. First-stage larvae could also be frozen by this method. Thawed first-stage larvae remained viable and continued their development to third-stage larvae, which were shown to be infective to dogs.     

Acquired immunity in rats against Angiostrongylus cantonensis infection

Acquired immunity against Angiostrongylus cantonensis was induced by immunizing rats with somatic antigens from fifth-stage larvae and adult worms and live third-stage larvae. Rats immunized twice had significantly fewer worms than rats immunized three times. Fewer worms were recovered from rats immunized with 200 live third-stage larvae than from any other groups. Rats immunized with somatic antigens had higher enzyme-linked immunosorbent assay (ELISA) antibody levels than rats immunized with live larvae. Rats immunized with live third-stage larvae of Angiostrongylus cantonensis were more strongly protected against challenge infections (62-92%) than rats immunized with antigens extracted from fifth-stage larvae (0-30%) and adult worms (11-24%).     

Phenology and laboratory rearing procedures of an Asian longicorn beetle, Glenea cantor (Coleoptera: Cerambycidae: Lamiinae)

Clenea cantor (F.) (Coleoptera: Cerambycidae: Lamiinae) is an Asian longicorn beetle whose larvae bore under the bark of living trees of at least seven plant families and enter the wood for pupation. Here, we determined the phenology of this beetle on its natural host, kapok [Bombax ceiba L. = Cossampinus malabaricus (DC.) Merr], in an uncontrolled insectary at ambient environmental conditions, and we compared the efficiency of four larval rearing procedures at 25 +/- 2 degrees C, 75 +/- 5% RH, and a photoperiod of 14:10 (L:D) h in the laboratory. It had five generations, including an overwintering generation, a year in southern China, with overlaps between generations and no diapause. Adults were present in early March-early December; eggs in early April-early December; larvae almost year-round, and pupae in mid-February-mid-April as well as mid-May-late November. All larvae of the overwintering generation and the larvae of the fourth generation that hatched in and after mid-November overwintered. The longevity of females and males was 71.94 +/- 1.21 d and 46.87 +/- 1.11 d, respectively, and mean fecundity was 106.65 +/- 3.61 eggs. Four larval rearing procedures using kapok twigs were tested: (1) 10 neonate larvae were left in the original host twig, (2) 10 neonate larvae were removed from the original bark and transferred to a new host twig, 3) 10 neonate larvae embedded in the original bark were transferred to a new host twig, and 4) a single neonate larva embedded in the original bark was transferred to a new host twig. We observed the survival of 300 neonate larvae for each rearing procedure. Approximately 81-85% of neonate larvae successfully developed to adult stage when neonate larvae were transferred together with the original bark to new host twigs; when neonate larvae were transferred without the original bark, only approximately 38% of the inoculants became adults, and when larvae were left in original twigs, approximately 52% of them reached adult stage. Resulting adults from different rearing methods and collected from the field had similar body weight and sex ratio. In terms of time, labor, and the number of resulting adults, procedure 3 is the most effective method for maintaining a laboratory colony.     

Association between ecological factors and the presence of Rhipicephalus (Boophilus) microplus larvae in Puerto Rico

A prevalence study was conducted to survey tick larvae populations in Puerto Rico (PR), compare the number of infested sites with Rhipicephalus (Boophilus) microplus larvae between the wet and dry season, and assess the associations of ecologic factors on the presence of R. microplus larvae. Ninety-six sites were selected using a GIS-based sampling method. Each site was sampled twice; the first sampling was performed during the dry season (March 4-18, 2007) and the second sampling during the wet season (August 13-26, 2007). Sites were sampled using a tick drag with a 1-m(2) white flannel cloth along a 50-m straight course. Only 2 tick species were identified. In the dry season, 15 sites (0.16, 95?% CI?=?0.09-0.24) were identified with R. microplus larvae (n?=?606) and 9 sites (0.09, 95?% CI?=?0.04-0.17) with Dermacentor (Anocentor) nitens larvae (n?=?779), whereas in the wet season 5 sites (0.05, 95?% CI?=?0.02-0.12) were identified with R. microplus (n?=?94), and 5 sites (0.05?%, 95?% CI = 0.02-0.12) with D. nitens (n?=?275). Difference in the number of infested sites with R. microplus was significant (P =?0.031) between the 2 seasons. Factors associated with the presence of R. microplus larvae in PR were wind speed of >4.0?km/h (OR?=?0.07, 95?% CI?=?0.01-0.63), more than 25?% bushes and shrubs on the site (OR?=?11, 95?% CI?=?1.6-71), and presence of cattle on the site (OR?=?26, 95?% CI?=?3.4-188).     

Acquisition of freezing tolerance in early autumn and seasonal changes in gall water content influence inoculative freezing of gall fly larvae,Eurosta solidaginis (Diptera,Tephritidae)

We examined seasonal changes in freeze tolerance and the susceptibility of larvae of the gall fly, Eurosta solidaginis to inoculative freezing within the goldenrod gall (Solidago sp.). In late September, when the water content of the galls was high (approximately 55%), more than half of the larvae froze within their galls when held at -2.5 degrees C for 24 h, and nearly all larvae froze at -4 or -6 degrees C. At this time, most larvae survived freezing at > or = -4 degrees C. By October plants had senesced, and their water content had decreased to 33%. Correspondingly, the number of larvae that froze by inoculation at -4 and -6 degrees C also decreased, however the proportion of larvae that survived freezing increased markedly. Gall water content reached its lowest value (10%) in November, when few larvae froze during exposure to subzero temperatures > or = -6 degrees C. In winter, rain and melting snow transiently increased gall water content to values as high as 64% causing many larvae to freeze when exposed to temperatures as high as -4 degrees C. However, in the absence of precipitation, gall tissues dried and, as before, larvae were not likely to freeze by inoculation. Consequently, in nature larvae freeze earlier in the autumn and/or at higher temperatures than would be predicted based on the temperature of crystallization (T(c)) of isolated larvae. However, even in early September when environmental temperatures are relatively high, larvae exhibited limited levels of freezing tolerance sufficient to protect them if they did freeze.     

Susceptibility of early larval stages of Pseudaletia unipuncta and Spodoptera exigua (Lepidoptera: Noctuidae) to the entomogenous nematode Steinernema feltiae (Rhabditida: Steinernematidae)

Early stages (neonate to 7- or 8-day-old larvae) of Spodoptera exigua and Pseudaletia unipuncta were exposed to the entomogenous nematode, Steinernema feltiae, at concentrations of 0, 10, 25, 60, 100, or 200 nematodes per larva. Larvae of both species were susceptible to nematode infections. However, neonate larvae of S. exigua were significantly less susceptible to nematode infection than 3- or 8-day-old larvae at or above 50 nematodes per larva. Mortalities of neonate larvae exposed to 50 or more nematodes ranged from 68 to 74% while mortalities of 3- and 8-day-old larvae ranged from 91 to 100%. The results with P. unipuncta showed similar trends as described for S. exigua, albeit at a lower mortality level and usually with no statistical differences. Mortalities of neonate larvae exposed to 50 or more nematodes ranged from 34 to 44% while mortalities of 7-day-old larvae ranged from 32 to 91%.     

Boophilus microplus: rejection of larvae from British breed cattle

Larvae of Boophilus microplus were labelled with [32P] and used to study the rejection of larvae from British breed cattle with different levels of resistance. On animals of high resistance the loss of larvae due to grooming ranged from 9-54% during the first 24 h of infestation, and more time was spent grooming by these animals. Most of the grooming activity could be attributed to the presence of tick larvae and the presence of older tick stages did not increase the percentage of larvae lost. Grooming was directed to attached larvae and these could be removed. Animals of low resistance did not lose a significant number of larvae as a result of grooming, but all previously infested hosts lost a proportion of the larvae (18-39%) which could not be accounted for by grooming. This loss was greater than the total loss of larvae (11%) on animals not previously exposed to B. microplus.     

Larval migration of Toxocara canis in piglets and transfer of larvae from infected porcine tissue to mice

Visceral larva migrans (VLM), caused by Toxocara canis larvae in humans, animals and birds, is now well documented throughout the world. Seven piglets were infected orally with 5 x 104 embryonated eggs and the migration and distribution of T. canis larvae in the tissues were evaluated. After artificial gastric juice digestion, larval yields at necropsy from different organs and muscles on days 1, 3, 7, 15 and 30 post-infection (DPI) revealed 3.05, 0.97, 0.21, 0.13, 0.05, 0.14% recovery from liver, lungs, heart, kidneys, skeletal muscles and brain tissues respectively, with a total of 2486 (4.97%) recovery from all tissues together. The highest number of larvae 1527 (3.05%) was recovered from the liver throughout the period (1-30 DPI), indicating a special affinity of larvae for the liver. Subsequently five mice were each infected orally with 5 g of infected pig liver and, after necropsy on 10 DPI, 20 +/- 3.62, 17 +/- 5.10, 3 +/- 1.26, 12 +/- 3.92 and 30 +/- 5.69 larvae were recovered from liver, lungs, heart, brain and muscles, respectively. Thus, primarily, the migratory potential and adaptation of T. canis larvae in porcine tissue was examined and, subsequently, their establishment in the second paratenic host, the mouse, has been successful. No influence of host sex on the migratory potential of T. canis larvae was observed. The related pathology caused by migratory larvae and its zoonotic significance through the consumption of raw or undercooked pork has been emphasized.     

Interactions between desiccation resistance,host-plant contact and the thermal biology of a leaf-dwelling sub-antarctic caterpillar,Embryonopsis halticella (Lepidoptera: Yponomeutidae)

During May 1997 thermal tolerance, supercooling point (SCP), low and high temperature survival, and desiccation resistance were examined in field-fresh Embryonopsis halticella Eaton larvae from Marion Island. SCPs were also examined in acclimated larvae, larvae starved for seven days, larvae within their leaf mines, and in larvae exposed to ice crystals. Field-fresh larvae had a critical minimum temperature (CT(Min)) and critical maximum temperature (CT(Max)) of 0 degrees C and 39.7 degrees C, respectively. Mean SCP of field-fresh caterpillars was -20.5 degrees C and this did not change with starvation. Field-fresh larvae did not survive freezing and their lower lethal temperatures (70% mortality below -21 degrees C) and survival of exposure to constant low temperatures (100% mortality after 12hrs at -19 degrees C) indicated that they are moderately chill tolerant. SCP frequency distributions were unimodal for field-fresh larvae, but became bimodal at higher acclimation temperatures. Contact with ice-crystals caused an increase in SCP (-6.5 degrees C), but contact with the host plant had less of an effect at higher subzero temperatures. It appears that the remarkable desiccation resistance of the larvae is selected for by the absence of a boundary layer surrounding their host plant, caused by constant high winds. This suggests that the low SCPs of E. halticella larvae may have evolved as a consequence of pronounced desiccation resistance.     

Toxicity, feeding deterrence, and effect of activity of 1,8-cineole from Artemisia annua on progeny production of Tribolium castanaeum (Coleoptera: Tenebrionidae)

1,8-Cineole isolated from Artemisia annua was tested against Tribolium castaneum (Herbst) for contact toxicity, fumigant toxicity, and antifeedant activity. The adults of T. castaneum were more susceptible than larvae to both contact and fumigant toxicity of 1,8-cineole, and LD50 and LC50 values of 108.4 microg/mg body weight of adult insect and 1.52 mg/liter air were found, respectively. Furthermore, 14-d-old T. castaneum larvae were more tolerant than 16- and 18-d-old larvae and adults to the contact toxicity of 1,8-cineole, but the 16- and 18-d-old larvae have similar susceptibility. In contrast, all the larvae (14-18 d old) of T. castaneum were much more tolerant than the adults to the fumigant action, but larvae of different ages had similar susceptibility. The compound 1,8-ciineole applied to filter paper at a concentration of 3.22-16.10 mg/cm2 significantly (P < 0.05) reduced the hatching of T. castaneum eggs and the subsequent survival rate of the larvae. Adult emergence was also reduced by 1,8-cineole. Feeding deterrence of 81.9% was achieved in T. castateum adults by using a concentration of 121.9 mg/g food, whereas larvae showed 68.8% at the same concentration.     

Coral larvae conservation: physiology and reproduction

Coral species throughout the world's oceans are facing severe environmental pressures. We are interested in conserving coral larvae by means of cryopreservation, but little is known about their cellular physiology or cryobiology. These experiments examined cryoprotectant toxicity, dry weight, water and cryoprotectant permeability using cold and radiolabeled glycerol, spontaneous ice nucleation temperatures, chilling sensitivity, and settlement of coral larvae. Our two test species of coral larvae, Pocillopora damicornis (lace coral), and Fungia scutaria (mushroom coral) demonstrated a wide tolerance to cryoprotectants. Computer-aided morphometry determined that F. scutaria larvae were smaller than P. damicornis larvae. The average dry weight for P. damicornis was 24.5%, while that for F. scutaria was 17%, yielding osmotically inactive volumes (V(b)) of 0.22 and 0.15, respectively. The larvae from both species demonstrated radiolabeled glycerol uptake over time, suggesting they were permeable to the glycerol. Parameter fitting of the F. scutaria larvae data yielded a water permeability 2 microm/min/atm and a cryoprotectant permeability = 2.3 x 10(-4) cm/min while modeling indicated that glycerol reached 90% of final concentration in the larvae within 25 min. The spontaneous ice nucleation temperature for F. scutaria larvae in filtered seawater was -37.8+/-1.4 degrees C. However, when F. scutaria larvae were chilled from room temperature to -11 degrees C at various rates, they exhibited 100% mortality. When instantly cooled from room temperature to test temperatures, they showed damage below 10 degrees C. These data suggest that they are sensitive to both the rate of chilling and the absolute temperature, and indicate that vitrification may be the only means to successfully cryopreserve these organisms. Without prior cryopreservation, both species of coral settled under laboratory conditions.     

Assessment of the nutritional status of field-caught larval Pacific bluefin tuna by RNA/DNA ratio based on a starvation experiment of hatchery-reared fish

RNA/DNA ratio is a useful and reliable indicator of the nutritional status of fish larvae and juveniles. In order to assess the nutritional status of field-caught larval Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel), starvation experiments of hatchery-reared larvae were conducted and changes in the RNA/DNA ratio of fed and starved larvae were analyzed. Starvation experiments were conducted every 3 days after first feeding. The survival rate of Pacific bluefin tuna larvae ranged 10-50% after 1 day of starved conditions and growth retardation was observed immediately. These results suggest that Pacific bluefin tuna larvae have a very low tolerance to starvation. The RNA/DNA ratios of fed larvae were approximately 2.0-4.0. On the other hand, the value of starved larvae significantly decreased to 1.0-3.0. The nutritional status of 3 cohorts of field-caught tuna larvae collected in the northwestern Pacific Ocean was examined based on the value of the RNA/DNA ratio of the 1 day starved larvae. 4.35-25.77% of the cohorts were regarded as the “starving condition”, which was negatively correlated to the ambient prey densities. These findings suggest that the nutritional condition of larval Pacific bluefin tuna was influenced by the ambient prey density, and starvation itself and starvation-induced predation could greatly contribute to mortality in the larval period of Pacific bluefin tuna.     

马缨丹总岩茨烯对小菜蛾和斜纹夜蛾幼虫的拒食作用

从马缨丹叶片中提取总岩茨烯,测定总岩茨烯对小菜蛾2龄幼虫和斜纹夜蛾1、2龄幼虫的拒食作用.结果表明,在非选择性试验中,1.6 mg·ml^-1的总岩茨烯对小菜蛾2龄幼虫和斜纹夜蛾1龄幼虫有拒食作用,8 h的拒食率分别为62.%和31.1%;在选择性试验中,0.4 mg·ml^-1的总岩茨烯即对小菜蛾2龄幼虫有拒食作用,0.4、0.8和1.6 mg·ml^-1浓度处理下的拒食率分别为52.7%、55.5%和78.9%;总岩茨烯只有在高浓度(1.6 mg·ml^-1)时,才对斜纹夜蛾1龄幼虫有拒食作用,拒食率仅为33.0%.在选择性和非选择性试验中,总岩茨烯对斜纹夜蛾2龄幼虫均无拒食作用.     

Developmental changes in the response of larval Manduca sexta fat body glycogen phosphorylase to starvation, stress and octopamine

Fasting or starvation of 1(st)- and 2(nd)-day fifth instar Manduca sexta larvae leads to rapid activation of fat body glycogen phosphorylase. Under feeding conditions, 21-29% of the phosphorylase was found in the active form. However, after only one hour of starvation, the active form increased to 55-65%. In larvae on the 3(rd)-day there was a slower increase in the activation, requiring three hours of starvation to reach a maximum of 60-65%. No activation was observed in 4(th)-day larvae after three hours of starvation. When 1(st)- or 2(nd)-day larvae were decapitated, the time-course of activation of glycogen phosphorylase was very similar to that observed in intact insects. However, activation of glycogen phosphorylase following decapitation was only observed in 1(st)- and 2(nd)-day larvae. In 2(nd)-day larvae, octopamine promoted activation of glycogen phosphorylase and 100-pmol of octopamine promoted maximum activation. Higher amounts of injected octopamine caused a decrease in activation. The injection of 100 pmol of octopamine caused a 50-55% activation of phosphorylase within 30 minutes. The simultaneous injection of the alpha-adrenergic receptor antagonist phentolamine with octopamine blocked the octopamine effect in 1(st)- and 2(nd)-day feeding larvae. However, the activation of glycogen phosphorylase observed in ligated/decapitated larvae on the 1(st)- and 2(nd)-day was not abolished by injection of phentolamine. All of these data suggest that factors other than adipokinetic hormone and octopamine may be involved in the activation of glycogen phosphorylase during fasting or starvation in the early part of the fifth larval stage of M. sexta.     

The bionomics of the free-living larvae and the transmission of Dictyocaulus filaria between lambs in North-East England.

The bionomics of the free-living larvae of Dictyocaulus filaria on pasture, and the transmission of infection between lambs, were studied during different seasons of the year in North-East England. The rate of development of first-stage larvae to the third stage took 4-9 days in late spring and summer, 1 1/2-4 weeks in autumn and 5 1/2-7 weeks in winter. The proportion of first-stage larvae developing to the third stage ranged from 10-28% in autumn and winter, and 2-25% in spring and summer. The rate of mortality of the third-stage larvae was approximately logarithmic in nature, although the survival time was shorter in spring and summer than in autumn and winter. Third stage larvae were able to survive from autumn until the spring of the following year in sufficient numbers to perpetuate transmission but not to cause clinical disease. In a transmission study, the survival of the infective larvae on the experimental plot was poor in summer, but the larval population increased in the autumn and then declined slowly throughout the winter. Infection in the susceptible lambs was related to the level of infection on the herbage increasing in severity from early summer to late autumn. However, those lambs infected in the summer were resistant to the heavy autumn challenge of larvae on pasture.