Autotomy-induced life history plasticity in band-legged ground cricket Dianemobius nigrofasciatus

Crickets can autotomize their limbs when attacked by predators. This enables them to escape death, but imposes a short-term cost on their escape speed and a long-term cost on their future mating ability. Therefore, adaptive response compensated for the cost of autotomy might be advantageous for autotomized individuals. In the present study, we examined whether autotomy induced life history plasticities compensating for the future cost in the band-legged ground cricket Dianemobius nigrofasciatus . Life history traits of D. nigrofasciatus were compared between autotomized and intact individuals. The developmental time and head width of the individuals that were autotomized as fourth instar nymphs were significantly shorter and smaller, respectively, than those of intact individuals. However, the adult longevity, number of eggs laid and oviposition schedule did not vary between autotomized and intact individuals. In addition, there was no difference between individuals autotomized at the fourth instar and adult stages in these three traits. Early maturation in the autotomized individuals might be advantageous through reducing the risk of predation owing to the shorter period in nymphal stages. The cost of small body size in the autotomized females might not be so great because of no significant difference in fecundity between autotomized and intact individuals. However, the cost of small body size was unclear in the autotomized males because in general larger males were preferred by females. These results indicated autotomy-induced life history that might reduce the cost of autotomy.     

Water potential, turgor and cell wall properties in elongating tissues of the hydrotropically bending roots of pea (Pisum sativum L.)

The hydrotropic bending of roots of an ageotropic pea mutant, ageotropum, was studied in humid air in a chamber with a steady humidity gradient. We examined the effects of atmospheric humidity around the root on the water status of root tissues, as well as the wall growth and the hydraulic properties of the elongating tissues. Atmospheric humidity at the surface of the root was clearly lower on the side orientated towards the air with lower humidity than on the side orientated towards the air with higher humidity. However, there were no differences in water potential and osmotic potential between the tissues that faced air with higher and lower humidities in the elongating and mature regions. Plastic extensibility was higher in the tissues that faced the air with lower humidity than in the tissues that faced the air with higher humidity. No differences in turgor pressure and yield threshold were observed between the tissues that faced air with higher and lower humidities. Therefore, the extensibility of the cell wall appeared to be responsible for the different growth rates of tissues in root hydrotropism. A further probable cause of the hydrotropical bending of roots is changes in the hydraulic conductance in the elongating tissues. Since the hydrotropic bending of roots occurred only when a root tip was exposed to a humidity gradient, hydrotropism might occur after perception of a difference in humidity by the root tip, with accompanying changes in cell wall extensibility and hydraulic conductance.     

A bimodal germination response to temperature in cocklebur seeds. I. Cyanide-sensitive and cyanide-resistant respirations

Abstract. Pre-imbibed cocklebur ( Xanthium penn-sylvanicum Wallr.) seeds displayed bimodal germination-temperature responses with two optima at 8 and 33° C. Such germination responses occurred subsequent to bimodal respiration-temperature upsurges at lower and higher temperature regions. At lower temperatures, cocklebur seeds respired predominantly through a cyanide-sensitive cytochrome pathway. A rise in temperature resulted in a marked increase in flux via an alternative pathway, a propyl gallate- (PG) or benzohydroxamic-acid- (BHAM) sensitive pathway, thus resulting in an increase in the ratio of this pathway relative to the cytochrome pathway. Both an increased capacity for the alternative pathway and an increase in the ratio of this pathway to the cytochrome pathway were obtained when pre-imbibed seeds were exposed to either 8 or 33°C for a short period. The effects of low temperature were reduced as the exposure time was prolonged beyond 3d, resulting in a reduction in germination. Neither PG nor BHAM had an inhibitory effect on the chilling-induced germination, but the germination-stimulating effect of high temperatures was less pronounced in the presence of PG or BHAM. At high temperatures, on the other hand, KCN and NaN₃ were ineffective or, rather, slightly inhibited germination. It was thus concluded that low and high temperatures exert their germination-stimulating effects by an essentially similar manner which increases fluxes both via the cytochrome pathway and, especially, via the alternative pathway and, as a result, raises the ratio of the latter to the former.     

Female-biased sex ratio in a wild bruchid seed-predator, Kytorhinus sharpianus. I. Larval competition and other factors

Abstract.

• 1 A wild bruchid seed-predator, Kytorhinus sharpianus, has a complex life cycle consisting of bi- and trivoltinism on a wild leguminous plant, Sophola flavescens. Observations of adults showed significant female-biased sex ratios (from 1:2 to 1:6) for nine generations over 4 years.
• 2 To investigate the potential effects of larval competition on the sex ratio, we altered the number of hatched eggs per seed and counted emergent males and females under laboratory conditions. Although only one adult could emerge per seed, the ratio of the females that emerged increased with the number of hatched eggs per seed. However, the sex ratio was not significantly different from 1:1 in the case of one hatched egg per seed.
• 3 We dissected seeds bearing two hatched eggs at regular intervals, and classified the surviving and the dead larvae according to their developmental stage. Over time, one larva within each seed always survived, while the other larva died from the second to fourth instar before the seed resource became exhausted.
• 4 In order to study the effects of the difference in the stages of two larvae in a seed on the emergence sex ratio, we manipulated intervals between the first and second ovipositions in the laboratory. As the difference in developmental stages of the two larvae increased, the closer to 1:1 the emergence sex ratio became.
• 5 Field observations, however, showed that about 60% of infested seeds were bored by only one K.sharpianus larva. This suggests that female dominance in larval competition within a seed may be relatively unimportant in causing the female-biased sex ratio in the field.

     

INDUCTION OF THE ACROSOME REACTION ON THE EGG SURFACE OF DE-JELLIED SEA URCHIN EGGS BEFORE AND AFTER FERTILIZATION*

The capacity of the surface of sea urchin eggs to induce the acrosome reaction was assayed by estimating the rate of acrosome reaction of supernumerary spermatozoa in the presence of variously treated eggs before and after fertilization. DTT-disruption of the vitelline coat did not eliminate the acrosome reaction-inducing capacity. This capacity was retained after fertilization in eggs of both H. pulcherrimus and A. crassispina. The acrosome reaction-inducing capacity of the eggs was markedly decreased by treatment with trypsin. The low capacity of the trypsin-treated eggs was maintained after fertilization in H. pulcherrimus, but in A. crassispina the capacity returned to the pre-trypsin treatment level after fertilization. Fertilized eggs from which the fertilization membrane was mechanically removed retained the inducing capacity to a considerable extent, independent of the presence or absence of the hyaline layer, but the capacity diminished rapidly as cleavage proceeded. It was concluded from these data that the acrosome reaction of spermatozoa actually occurred at the surface of de-jellied eggs and that the inducing substance resides in the plasma membrane in addition to the fertilization membrane. A chemical difference between the inducing substance of egg surface and jelly substance is discussed.     

用hu-RBC-SCID小鼠分离鉴定献血者巴贝斯样原虫

目的用人红细胞(RBC)替代SCID小鼠自身血循环红细胞而建立的人化小鼠模型,即hu-RBC-SCID模式小鼠,分离并鉴定献血者中隐性人巴贝斯虫病原的感染,确定输血患者的感染来源.方法去除NOD/shi-scid小鼠自身血循环红细胞,辅以肌肉注射兔抗小鼠血红蛋白生成素血清和大鼠抗小鼠RBC单克隆抗体,用人O型红细胞注入NOD/shi-scid小鼠血循环中,建成hu-RBC-SCID模式小鼠,接种献血者的RBC.结果接种献血者的RBC的hu-RBC-SCID模式小鼠的RBC中,出现巴贝斯原虫,并大量增殖,最高达到40%,经形态学、PCR等方法鉴定病原为 Babesia microti 样原虫,与患者的一致.结论 hu-RBC-SCID模式小鼠证实,患者确因输血感染;hu-RBC-SCID模式小鼠是人巴贝斯原虫研究理想的动物模型.