A comparison of in vitro and in vivo estimates of the viability of Taenia pisiformis eggs aged under controlled conditions, and their ability to immunise against a challenge infection

Storing the eggs of T. pisiformis for periods of 0 to 9 days at a temperature of 36–38°C and relative humidity of 87–93 % revealed at least 4 stages in the ageing process. Firstly, a stage in which eggs hatched and activated in vitro and were also fully infective for rabbits. Secondly, a stage in which eggs hatched and activated in vitro but underwent only partial development in rabbits. Thirdly, a stage in which eggs hatched and activated in vitro, and presumably therefore in vivo, but no evidence of infection could be found when they were fed to rabbits. Fourthly, a stage in which eggs either did not hatch, or if they did hatch, the oncosphere was rapidly digested. In vitro techniques for assessing viability of T. pisiformis eggs were not a reliable guide to their infectivity for rabbits. ‘Senescent’ eggs, that is eggs which produced evidence of early infection in rabbits but did not complete their development to cysticerci, failed to produce immunity to challenge infection with T. pisiformis eggs.     

Effects of insect herbivory on early plant succession: comparison of an English site and an American site

We examined the survival, size, and agonistic behaviour of faster and slower developing rainbow trout ( Salmo gairdneri ) in an artificial stream channel with a simulated redd. The analysis was performed at two levels: between three full-sib families genetically marked at a hexosaminidase locus, and within families segregating for a regulatory allele Pgml-t(b) that is associated with faster developmental rate. The families differed significantly in their hatching times but showed little variation in emergence times. Fishes with the Pgml-t(b) allele hatched and emerged significantly earlier than their full-sibs without the allele. Despite the mortality of at least 50% of emerged fishes in the selection experiment, there was no significant difference in survival between either the three families or fishes with different genotypes at the Pgml-t locus. However, fishes from the faster developing family and those with the Pgml-t(b) allele had significantly higher levels of agonistic behaviour and had a tendency to be larger than slower developing individuals.     

The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island wallaby (Macropus eugenii): development and hatching of the egg and the freeliving stages

Smales L. R. The life history of Labiostrongylus eugenii, a nematode parasite of the Kangaroo Island Wallaby (Macropus eugenii): development and hatching of the egg and the free living stages. International Journal for Parasitology7: 449–456. Labiostrongylus eugenii (Trichonematidae) occurs in the stomach of the Kangaroo Island Wallaby. Egg morphology is similar to that of other strongyloids. When incubated at 25°C embryogenesis is completed in about 30 h. An incomplete moult occurs within the egg, and larvae hatch at a sheathed second-stage $\text{43}\text{1}\text{2}\text{–83}\text{1}\text{2}$ h later. Development occurred at all temperatures between 2° and 37°C with an optimum about 25°C and an upper limit near 37°C. The hatching process is very rapid, taking about 2 min. It is signalled by increased larval activity followed by a change in shell permeability. The larva hatches at that pole of the shell which has become plastic.The sheathed second-stage larva measures 659.50 ± 22.54 μm by 27.98 ± 1.22 μm. Its internal structures are concealed by a mass of opaque granules which were demonstrated as neutral lipid by oil red O staining. A second incomplete moult at 3–4 days results in a doubly sheathed infective larva from which the lipid gradually disappears. The mouth never appears patent and the larvae neither feed nor grow but rather decrease in size with age. Optimal temperatures for larvae range between 15°–25°C with 37°C about the upper limit. The significance of this developmental pattern is discussed.     

The hatching enzyme from xenopus laevis: Limited proteolysis of the fertilization envelope

Hatching in the amphibian Xenopus laevis involves release of an embryo-secreted hatching enzyme, a protease, which weakens the envelope surrounding the embryo. The envelope is not totally solubilized, which infers that only selected envelope components are hydrolyzed by the enzyme. The susceptibility of the glycoprotein components composing the envelope to hydrolysis by the hatching enzyme was investigated. Isolated envelopes in various physical states, ie, particulate and solubilized, were treated with the hatching enzyme, and the resulting envelope hydrolysis products were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The susceptibility of the envelope components to proteolysis was not a function of the state of the envelope. The envelope components most susceptible to proteolysis were the 125K and 11 8K components followed by the 60K and 71 – 77K components. These components are minor constituents of the envelope. The major constituents, 33K and 40K, were relatively resistant to hydrolysis by the hatching enzyme. From these observations, we infer that the envelope components hydrolyzed are components that link or bind together the major structural elements of the envelope, eg, the 33K and 40K components. Selective destruction of the components required for maintaining the structural integrity of the envelope, eg, the “nuts and bolts” of the structure, permits a weakening of the envelope that allows the embryo to hatch without having to destroy totally (hydrolyze) the envelope.     

Spread of hatch and delayed feed access affect post hatch performance of female broiler chicks up to day 5

It is not rare that newly hatched chicks remain without feed for about 24 to 48 h before they are placed on farms due to a series of logistic operations. Furthermore, the spread in hatching time can also mount up to 30 to 48 h for late v. early hatchers. In other words, the practice is a complex combination of spread of hatch and delayed feed access. The present study was aimed to investigate the combined effects of hatching time with a delay in feed access of 48 h, starting from their hatch-time (biological age). When chicks had access to feed immediately after hatch, late hatchers had a higher feed intake and relative growth rate up to day 5 compared with their early hatched counterparts. Feed deprivation during the first 48 h resulted in retarded early growth rate, which was further aggravated by an impaired feed intake after refeeding. In addition, the differential effects of hatching time on relative growth rate and feed intake observed in immediately fed chicks were eliminated by the 48 h feed delay. The yolk utilization after hatch was faster for the late hatchers up to biological day 2 regardless of the feeding treatments. Hatching muscle glycogen content was higher in the late hatchers compared with that of their early counterparts at hatch and at biological day 2 independent of feeding treatment. Moreover, the liver glycogen content of the late hatchers was also higher at hatch. For the immediately fed chicks, the proportional breast muscle weight of the late hatchers was higher at biological day 2 and 5. For the starved chicks, on the other hand, this effect was only observed after they had access to feed (biological day 5). The different plasma T₃ levels at hatch may have contributed to the different post hatch performance. It is concluded that the spread of hatch influenced post hatch performance, especially appetite and growth at least until day 5. Moreover, the delay in feed access interacted with the hatching time and caused adverse effects on the post hatch performance.     

Ephippia of Daphnia magna straus — A technique for their mass production and quick revival

A new rearing technique ideally suitable for promoting either the parthenogenetic or the gametogenetic (ephippia) type of reproduction ofDaphnia magna in the laboratory is described. Airdrying and rehydration induces rapid hatching. Using this technique it is possible to measure the toxicity of chemicals to ephippia in an 8 day test procedure.     

自然干燥对冬虫夏草寄主蝠蛾卵孵化的影响

研究在室内自然空气湿度下放置的时间长短对冬虫夏草(Cordyceps)寄主昆虫贡嘎蝠蛾Hepialus gonggaensis Fu et Huang卵孵化率的影响。卵早期的研究结果为:第1批、第2批和第3批卵于室内自然空气湿度下保存的时间达26,11和16h后再保湿都可以正常孵化并且孵化率与对照无显著性差异,所孵化幼虫在饲养初期的成活率分别达62.0%,41.4%和43.4%,与对照无显著性差异。卵中期干燥放置36h的孵化率为66.7%,所孵化幼虫在饲养初期的成活率为50.0%,孵化率和成活率都与对照无显著性差异。卵晚期干燥放置24h的孵化率为70.0%,所孵化幼虫在饲养初期的成活率为49.0%,孵化率和成活率都与对照无显著性差异。以上结果表明,经历一定时间的干燥不会对卵的正常孵化有影响。     

大凉螈繁殖生态

大凉螈是我国特有的珍稀有尾两栖动物,其种群数量目前呈现明显下降趋势,然而涉及该物种保护的繁殖生态学研究仍十分匮乏。通过融合围栏陷阱及标志重捕的样方调查法,对大凉螈石棉栗子坪种群繁殖个体和变态登陆幼体的迁徙、繁殖群体种群大小、繁殖场内雌雄有效性比变化等进行了研究。运用Jolly-Seber法估测了繁殖种群大小,运用单因素方差分析或Kruskal-Wallis秩和检验比较了不同时期进入繁殖场的雄性大凉螈头体长及体重,运用t检验或者Wilcoxon秩和检验比较了雌雄性间形态上的差异,运用t检验、t′检验或Wilcoxon秩和检验比较了野外抱对雄性与非抱对雄性间的体征差别,运用Pearson相关分析探讨了雌性产卵量与其身体形态的关系,同时观察了卵的孵化情况。研究结果表明:大凉螈的繁殖季为每年的4月下旬到7月下旬,幼体最早于8月上旬变态登陆。估测调查地繁殖场内雄性大凉螈繁殖种群大小约为391尾,雄螈较雌螈更早进入繁殖场且在场内停留时间更长,体重较轻的雄螈较晚迁入繁殖场。有效性比明显偏雄(雌/雄:0.03—0.10)。雌雄间具明显性二型性,雌性个体的头体长、体重及肥满度均大于雄性,而雄性的尾高和尾长占全长的比例则大于雌性。对比自然抱对雄性和非抱对雄性个体发现,抱对个体在头体长、体重和尾高等体征方面显著大于非抱对个体,暗示这些形态特征可能在雄性竞争配偶的过程中起到关键作用。雌螈在室内条件下平均产卵数为176枚,产卵历时2—4 d,产卵量与雌性肥满度正相关,卵的平均孵化期为15.7 d,孵出幼体平均全长为9.74 mm。