Regional environments, life-history patterns, and habitat use of spirostreptid millipedes in arid regions

Among diplopods with desert populations, only three species of Spirostreptida have been studied in an ecological context. The present review compares regional environments, life-history patterns, and uses of habitat by Orlhoporus ornatus (Girard) from southwestern North America, Archispirostreptus tumuliporus judaicus (Attems) from the eastern Mediterranean seaboard, and Harpagophora nigra (Attems) from southwestern Africa. Published and unpublished studies are used to explore evidence for convergence among these species, as opposed to traits adapting them to physical aspects of given regions or habitats. Unlike A. t. judaicus, O. ornatus and H. nigra are relatively restricted to arid habitats, although populations of all three species experience a variety of rainfall regimes and regional topographies. Where studied, O. ornatus and H. nigra hibernate during the long, often cool or cold dry season; they forage following warm-season rains. A. t. judaicus , in contrast, forages during its long, warm dry season and hibernates in the cool, wet winter. Populations from the Judaean and Negev deserts differ from those inhabiting a mesic habitat (Megiddo) closer to the coast in regard to rates of development, seasonal activity and seasonal water balance. Convergence in the form of well-developed desiccation resistance characterizes the two strictly desert species. All three species, together with other subtropical millipedes exposed to long dry seasons, are convergent with respect to patterns of diel surface activity and use of shelter. However species- and habitat-specific life-history features such as the seasonal timing of dormancy and emergence tend to mask convergence at the habitat level. Hence, the independent evolution of the three species with desert populations has resulted in life histories and habitat use that combine a moderate amount of convergence with considerable opportunistic adaptation to regional and local conditions.     

中华稻蝗长沙种群的生活史及其卵滞育的进化意义

中华稻蝗Oxya chinensis为重要的水稻害虫,在我国除青海、西藏、新疆、内蒙古等未见报道外,南起海南北至东北均有分布,在许多的分布区域1年发生1代。为探索中华稻蝗长沙种群的生活史及其季节适应特征,通过野外和实验室的研究,调查了其发生代数、孵化率和卵滞育率的季节变化及越冬卵的存活率。结果显示,中华稻蝗长沙种群为1年2代和1年1代混合发生:第1代卵产卵后大部分孵化为若虫而1年完成2代,但亦有19.4% -4.1%的卵不孵化而1年只能完成1世代。第1代成虫于6月上旬至8月上旬羽化,6月下旬至8月中旬产卵;第2代若虫于7月初开始孵化,9-10月羽化为成虫,10月上旬至11月下旬产卵。在室外自然条件下,中华稻蝗长沙种群6-8月(第1代)和10-11月(第2代)所产卵块均为部分滞育,滞育率为30%左右,皆无显著差异。然而,其卵滞育率在12月以后显著降低,仅为6.6%或以下,卵滞育快速地得以解除。因此,包括非滞育卵和滞育解除卵,中华稻蝗长沙种群的越冬卵皆以非滞育状态度过其后的寒冷季节。即使是遭遇长江流域2007年末至 2008年初异常寒冷的冬季,在长沙地区越冬后其卵的存活率亦在98%以上。非滞育状态的中华稻蝗长沙种群越冬卵完全能安全地越冬,其滞育的发生并非是为了提高其耐寒性而安全度过不适环境。并探讨了中华稻蝗长沙种群卵滞育的进化意义。     

The importance of clutch characteristics and learning for antiparasite adaptations in hosts of avian brood parasites

There is considerable variation in rejection rates of parasitic eggs among hosts of avian brood parasites. In this article, we develop a model that can be used to predict host egg rejection behavior in brood parasite-host systems in general, by considering both intra- and interclutch variation in host egg appearance; clutch characteristics that may be important in calculating the fitness of individuals adopting rejecter or acceptor strategies. In addition, we consider the importance of learning the appearance of own eggs during the first breeding attempt and host probability of survival between breeding seasons on evolution of rejection behavior. Based on this model we can predict at which level of parasitism fitness of rejecter individuals is higher than that of acceptor individuals and vice versa. The model analyses show that variation in egg appearance can be a key factor for the evolution of host defense against parasitism. In more detail, analyses show that we should expect to find a prolonged learning period only in hosts that have a high intraclutch variation in egg appearance, because such hosts may potentially experience high costs in terms of recognition errors. Furthermore, learning is in general more adaptive in parasite-host systems in which hosts do have some reproductive success even when parasitized, and when parasitism rates are moderate. By including variables that have not been considered in previous models, our model represents a useful tool in investigations of host rejection behavior in various host-parasite systems.     

Degree-day Models for Predicting Egg Hatch and Population Increase of Criconemella xenoplax

A degree-day model was derived to predict egg hatch for Criconemella xenoplax. Eggs collected from gravid females were incubated in distilled water at constant temperatures of 10-35 C. Sixty-six percent of all eggs hatched between 13 and 32 C, and 42% hatched at 10 C. All eggs aborted above 32.5 C. Between 25 and 32 C, 8.5 ± 0.5 days were required for egg hatch. Degree-day requirement for egg hatch at 10-30 C was estimated to be 154 ± 5 with a base of 9.03 ± 0.04 C. This base of 9 C was adopted in studies of the relationship between degree-days and nematode population increase on Prunus seedlings grown 9-11 weeks in a greenhouse. Degree-day accumulations were based upon daily averages from maximum and minimum air temperatures. Ratios of final to initial population densities exhibited an exponential pattern in relation to degree-day accumulations with proportionate doubling increment of 0.100 ± 0.049 every 139 ± 8 degree-days. These results provide a means of predicting nematode population increase under greenhouse conditions and a basis for choosing sampling intervals when evaluating nematode multiplication.     

Remote monitoring of parental incubation conditions in the greater sandhill crane

To monitor incubation conditions in nests of greater sandhill cranes, a radiotrans-mitting egg was built using six temperature sensors, a position sensor, and a light sensor. Sensor readings were received, along with time of observations, and stored in a computer. The egg was used to monitor incubation in nests of six pairs of cranes during 1987 and 1988. Ambient temperature was also measured. Analysis of covariance (ANCOVA) was used to relate highest egg temperature, core egg temperature, and lowest egg temperature to ambient temperature, time since the egg was last turned, and time since the beginning of incubation. Ambient temperature had the greatest effect on egg temperature (P < 0.0001), followed by the time since the beginning of incubation and time since the egg was last turned. Pair effect, the class variable in the ANCOVA, was also very significant (P < 0.0001). A nine-term Fourier series was used to estimate the average core egg temperature versus time of day and was found to fit the data well (r² = 0.94). The Fourier series will be used to run a mechanical incubator to simulate natural incubation conditions for cranes. © 1995 Wiley-Liss, Inc.     

Effect of Some Pesticides on Reproduction of Rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> Müller

Pesticides have been major contributors to environmental pollution and they are now widely distributed in aquatic environments. Zooplankters are frequently used as test animals to detect aquatic contaminants because of their sensitivity and ecological importance. We investigated the effect of a 7-day exposure to four commonly used pesticides (diazinon, fenitrothion, methoprene and isoprothiolane) on reproduction of the rotifer Brachionus plicatilis. Pesticide concentrations of 3–7 times lower than the 24-h 50% lethal concentration (24-h LC₅₀) were tested to determine the ‚no observed effect’ concentration (NOEC), ‚lowest observed effect’ concentration (LOEC), and the ‚50% effective’ concentration (EC₅₀) on specific growth rate (r), sexual reproduction, fertilization, resting egg production, and hatchability of resting eggs. Results showed that the lowest EC₅₀ value of r, mixis, fertilization, and resting egg production of 1.4 μM for diazinon was 63 times lower than its 24-h LC₅₀ of 88.4 μM, while for fenitrothion it was 66 times (3.5 and 229.8 μM, respectively). For isoprothiolane, the lowest EC₅₀ value of r, mixis, fertilization, and resting egg production of 8.9 μM was 25 times lower than its 24-h LC₅₀ of 220.7 μM, while for methoprene was 37 times (2.7 and 100.8 μM, respectively). In all pesticides, hatching rate of resting eggs consistently gave the lowest EC₅₀ values which is about 2–40 times lower than the lowest EC₅₀ of r, mixis, fertilization, and resting egg production. Hatchability of resting eggs therefore is the most sensitive parameter in detecting effects of pesticides exposure in rotifer B. plicatilis.     

A case of chronic cerebral paragonimiasis westermani

We report a chronic cerebral paragonimiasis from a 41-year-old Korean man who complains a headache and weakness of left motor neuron components. Magnetic resonance images of the brain revealed conglomerates of multiple ring-like enhancements in temporo-occipital and frontal lobes of the right hemisphere. An intradermal test for paragonimiasis westermani was positive. The patient was born near an endemic area of paragonimiasis and used to eat boiled or grilled freshwater crayfish in his childhood. Nodules in the brain were resected through craniotomies. The eggs of P. westermani were identified pathologically and parasitologically in the calcified necrotic lesions. Examinations on sputum and fecal specimens for the eggs of P. westermani were shown to be negative and a chest radiograph was normal. It is presumed that the brain lesions were formed by P. westermani approximately 30 years ago.     

水浸对越北腹露蝗卵的影响

越北腹露蝗Fruhstorferiola tonkinensis Will.是广东北江流域河滩蝗虫的优势种。以不浸水的蝗卵为对照,研究滞育期蝗卵浸水5～95d和胚胎发育期蝗卵浸水1～30d对卵孵化率和历期的影响。结果表明,随浸水时间的增加,孵化率下降,卵发育延迟;滞育期蝗卵经受95d的浸水仍有8.01%存活,而胚胎发育期蝗卵浸水30d后全部死亡,滞育期蝗卵比胚胎发育期蝗卵具有更强的耐浸水能力。说明越北腹露蝗以卵滞育的形式发展了对水浸胁迫的适应。     

Large Hawk‐Cuckoo Hierococcyx sparverioides parasitism on the Chinese Babax Babax lanceolatus may be an evolutionarily recent host–parasite system

We documented brood parasitism by the poorly studied Large Hawk‐Cuckoo on a previously unknown host species, the Chinese Babax. Furthermore, we describe a new egg colour for the Large Hawk‐Cuckoo. The parasitism rate of Chinese Babax nests over 4 years was 6.9% (11 of 159 nests), with significant temporal variation. The Large Hawk‐Cuckoo laid immaculate white eggs that appeared non‐mimetic to the blue Babax eggs, an impression that was confirmed by avian visual modelling. Nevertheless, most Cuckoo eggs were accepted by the host, suggesting that this host–parasite system may be evolutionarily recent.     

Cell-cycle dependency of radiosensitivity and mutagenesis in fertilized egg cells of rice,Oryza sativa L.

Summary In order to examine changes in survival and mutation rates during a cell cycle in higher plant, fertilized egg cells of rice were irradiated with X-rays at 2 h intervals for the first 36 h after pollination, i.e., at different phases of the first and second cell cycles. The most sensitive phase in lethality was late G₁ to early S, followed by late G₂ to M, which were more sensitive than the other phases. In both M₁ and M₂ generations, sterile plants appeared most frequently when fertilized egg cells were irradiated at G₂ and M phases. Different kinds of mutated characters gave rise to the respective maximum mutation rates at different phases of a cell cycle: namely, albino and viridis were efficiently induced at early G₁, xantha at early S, short-culm mutant at mid G₂, heading-date mutant at M to early G₁. The present study suggests the possibility that the differential mutation spectrums concerning agronomic traits are obtained by selecting the time of irradiation after pollination.