SOUND PROPAGATION IN SHALLOW WATER: IMPLICATIONS FOR ACOUSTIC COMMUNICATION BY AQUATIC ANIMALS

ABSTRACT

Measurements of sound propagation were made in a shallow, sloping bottomed freshwater pond. The frequency responses of the pond had a highpass characteristic with a sharp cutoff frequency. Cut-off frequency of the response was inversely related to the depth of water at the shallowest transducer (either projector or receiver) and was the same whether propagating downslope or upslope (reciprocity). The relationship between cut-off frequency and depth was significantly different from that expected for propagation in a channel with either a rigid or pressure release (gas) bottom. The highpass characteristic is due to modal propagation in the ‘waveguide’, and the effect of this environmental filtering is 30–60 dB between frequencies that propagate and those that do not. Thus, the physical constraints of this shallow-water environment on acoustic communication by aquatic animals are much greater than those measured in terrestrial environments. These constraints are discussed relative to selection for behavioural adaptations of acoustically signalling aquatic animals and are compared to similar adaptations found in terrestrial systems.     

NEAR-VESSELLESSNESS IN EPHEDRA AND ITS SIGNIFICANCE

Wood of two specimens of Ephedra from high alpine localities is nearly vesselless: E. gerardiana from 4,750 m in Tibet, and E. rupestris from 4,300 m in Argentina. Ephedra gerardiana from lower elevations in the Himalayas has more vessels, although even there they are not abundant. Instances in other species of Ephedra in which extensive areas of latewood or even entire growth rings are vesselless are cited; these tend to occur in high deserts with climates somewhat less extreme than those of the alpine localities. Near-vessellessness is interpreted as an adaptive condition in which the proportion of tracheids, conductively safer than vessel elements, reaches a maximum. Near-vessellessness in Ephedra wood is probably reversible within limits, and should be likened to production of latewood to the exclusion of earlywood. Comparisons are offered to dicotyledons in which abundance of vessels is lowered with respect to ecological extremes.     

NON-SHIVERING THERMOGENESIS AND ITS THERMOREGULATORY SIGNIFICANCE

1. Non-shivering thermogenesis (NST) is a heat-production mechanism participating in the chemical thermoregulation of mammals. 2. NST is additional to shivering and takes place at temperatures close to the thermoneutral zone. 3. NST occurs in newborn mammals and in those that hibernate. In some adult mammals it can be induced by adaptation to cold. 4. In small mammals NST produces approximately the same amount of heat as shivering. It becomes less important with increasing body weight of the animals. 5. NST is regulated by the hypothalamus and it is based predominantly on the calorigenic action of noradrenaline released from sympathetic nerve-endings. Participation of other calorigenic substances and of the specific dynamic action of food cannot be excluded. 6. NST is localized mainly in skeletal muscles and in brown adipose tissue. Small amounts of NST may come from liver, intestine, heart and brain. 7. The biochemical basis of the calorigenic action of noradrenaline has not yet been fully elucidated.     

白蚁翅面的微刻点及其意义

本文首次描述了在扫描电镜下观察到的22种主要采自浙江省的白蚁(隶属4科11属)的翅面微刻点,然后讨论了白蚁翅面微刻点的进化学,分类学,生物学和生态学意义．     

岩梧桐属的花粉形态及其分类学意义

本文通过光学显微镜和扫描电镜对岩梧桐属Wightia Wall.花粉进行了深入的观察,并与紫葳科和玄参科部分属种作了详尽的比较。结果认为,从花粉的大小等级、萌发孔特征、外壁内外层比例等看,岩梧桐属花粉与玄参科的花粉更类似,而与紫葳科的相距较大。孢粉学支持把岩梧桐属置于玄参科。该属的国产种,根据花粉的大小和外壁纹饰特征的差异划分为两个种较为合理和自然,不该合并为一个种。     

山茶科花粉超微结构及其系统学意义

借助光学显微镜,扫描电镜及透射电镜对分布于亚洲,北美洲及中南美洲山茶科１７属约５０种植物的花粉进行了系统的观察研究。本科花粉为３孔沟或３孔沟,近扁球至近球形,少数近长球形。大小从１３￣５０μｍ×５５．３μｍ。表面纹饰可分为皱波状,颗粒状,疣状,钝刺状,网状,穴网状及近乎光滑等类型。在皱波状纹饰中,其皱脊的组成分子可分为颗粒,念珠状结构。外臂为具复盖－柱状层结构,复盖层－穿孔或不穿孔。其复盖层、柱状     

THE PHOSPHORYLATION OF NUCLEAR PROTEINS IN THE REGENERATING AND PREMALIGNANT RAT LIVER AND ITS SIGNIFICANCE FOR CELL PROLIFERATION

In liver regeneration or neoplastic transformation, phosphorylation of nuclear proteins is stimulated. In the regenerating liver all main histone fractions are involved in this process. The type of histone phosphorylated seems to be dependent on the position of the partially synchronized cells within the generation cycle. At a time when most cells are exhibiting maximum HnRNA-synthesis, histone F2a2 belongs to those fractions with highly stimulated phosphate incorporation. Phosphorylation of this fraction alone is stimulated by cyclic AMP in parallel to a stimulation of HnRNA-synthesis. The preneoplastic liver is characterized by oscillating phosphorylation and dephosphorylation reactions of nearly all histone fractions during the first days of N-nitroso-diethylamine administration. After 2 months of carcinogen feeding a 50–150% stimulation of the phosphorylation of Fl subfractions is observed. The phosphate content of the other histones, however, has returned to the original level. A series of further proteins, isolated together with the histones, show very similar phosphorylation characteristics. These proteins are mostly of non-histone origin. It is suggested that some of them are responsible for the transport of RNA with messenger properties within the cell.