高黎贡山鼠兔一新种

1985年10月,云南省流行病防治研究所调查队在云南西北部高黎贡山北段的贡山地区相继采到3只体色特殊的鼠兔,经与该属各已知种比较均不同,鉴定为一新种,描述如下:     

Statistics for disinterested scientists.

This paper presents a brief introduction to some basic statistical tools and techniques with examples applied to biological data. Perhaps after becoming more familiar with statistics and more appreciative of their power in extracting information from data the previously fearful and skeptical researcher may be more inclined to make them an integral part of his research technique and also include them in his publications. For problems of greater difficulty, consultation at the early stages, preferably before undertaking the project, with a good biostatistician is suggested.     

The late Pleistocene desiccation of Lake Victoria and the origin of its endemic biota

A brief review is provided in some advances in understanding the ecology of pike Esox lucius Linnaeus over the last 10 years. Based on long-term studies and manipulative, often short-term experiments (laboratory, field and mesocosms) several established theories have been supported, as well as new concepts developed. Despite their wide distribution pike show low levels of polymorphism and divergence indicative of a recent common ancestral population. Recent genetic studies, however, indicate a single refugium in North America compared to several refugia in Europe. Pike are found in rivers, lakes and weakly saline waters. Variables such as growth and mortality are mainly affected by factors such as temperature, water transparency, productivity, availability of prey and density of pike and other predators. In choice of habitat pike have been shown to support the ideal free-distribution theory. The importance of macrophyte habitat in the life history of pike has been reconfirmed and pike have been shown to be flexible in response to water clarity. Pike are extremely ‘plastic’ in choice of prey types, prey size and in response to prey behaviour (e.g. they are unaffected by shoal size). Predation by pike not only affects abundance and biomass of prey (including younger and smaller pike through cannibalism which plays a major role in population dynamics, other fishes and invertebrates) but also evolution and adaptation of their morphology (in particular body shape) and behaviours. There appears to be no relationship between stock and recruitment. Recruitment is influenced by several abiotic factors in lakes and rivers. Pike play a major role in structuring freshwater communities and have been used in stocking programmes to improve water quality (biomanipulation). Many new concepts have been developed in pike behaviour in maximizing these stocking programmes both in biomanipulation and fisheries management. Despite many recent advances in understanding the ecology of pike, particularly at the individual level, developments in quantifying and modelling the role of pike as a top predator in large ecosystems have been limited, probably due to the difficulties of sampling natural populations. Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species     

5′-Nucleotidase activity in the pineal organ of the pike

Summary To date, it is still unknown whether the metabolism of purine nucleotides and nucleosides plays an important role in the pineal organ of lower vertebrates. We have therefore investigated the sites of 5-nucleotidase activity in the pineal organ of the pike (Esox lucius L.). Various ultracytochemical procedures were used. An intense ecto-5-nucleotidase activity was characteristic of the entire plasma membrane of the phototransducers (cone-like and modified photoreceptor elements) and the interstitial cells, with exception of the portions facing the basal lamina of the pericapillary spaces. Additionally, intracellular sites of activity were also visualized in the inner segment and the pedicle of the phototransducers. Most of the intracellular deposits were apparently cytosolic and only few seemed to be associated with the membrane of the clear synaptic vesicles of the pedicle. Phagocytotic cells in the pineal lumen also showed a strong enzymatic activity on the outer surface of their plasmalemma (in ectoposition). This was apparently not the case for the cell types of the tissues surrounding the pineal vesicle. The present study emphasizes the importance of the occurrence and metabolism of purine nucleotides and nucleosides in a photoreceptive pineal organ.     

Feeding and Refuge Use by Small Fish in the Presence of Cyanobacteria Blooms

We studied the effect of cyanobacteria on foraging and refuge use in small fish. We measured pike larval feeding in the presence of cyanobacteria by counting leftover prey. Our results showed that feeding by pike larvae on zooplankton prey decreased significantly in the presence of non-toxic cyanobacteria. The behaviour can be due to lowered vision caused by turbidity or clogging of the gills. Further, we tested whether the three-spined stickleback use toxic cyanobacteria as a refuge against predators in a choice experiment. The choice experiment was performed in a Y-maze fluviarum, where the fish could select between two different environments. Our results support the refuge use hypothesis because the three-spined stickleback clearly preferred toxic cyanobacteria to the chemical predator signal. To conclude, cyanobacteria decrease feeding rates in fish larvae, but may function as important refuge for e.g. sticklebacks, during predation pressure in pelagic algal blooms.     

Effects of macroalgal exudates and oxygen deficiency on survival and behaviour of fish larvae

Filamentous algae may create anoxic, i.e. oxygen free, conditions during night and fish larvae that commonly spend their first months in the littoral may therefore be subject to anoxia. We conducted two different experiments; firstly, we measured behaviour of pike larvae (Esox lucius L.), such as frequency of prey attacks and time in vegetation, in the presence of a chemical predator cue and oxygen deficiency. In the second experimental set-up, pike larval survival was monitored in water with added macro-algal exudates (excreted from Pilayella littoralis) and a low oxygen level (3 mg l^− 1). Our results showed that oxygen concentration and the chemical predator signal, caused by three-spined sticklebacks, had strong significant effects on the larval prey attacks. The prey attacks were strongly reduced at 3 mg oxygen l^− 1. However, survival of the larvae was not affected by low oxygen and macro-algal exudates. Pike larvae are very tolerant to hypoxia and exudates excreted by the littoral vegetation, whereas prey attacks are strongly decreased in hypoxia when a predator is around. This may have negative consequences for pike larval growth and recruitment in eutrophicated environments.     

钠、钾、钙和葡萄糖对白斑狗鱼精子活力的影响

观察了白斑狗鱼精子在0～679．6kPa NaCl、KCl、葡萄糖溶液和0～339．8kPa CaCl2溶液中的活动情况。在NaCl、KCl、葡萄糖溶液中,白斑狗鱼精子快速运动时间和寿命的变化规律基本一致,精子活动最适渗透压介于339．8～453．0kPa。K^ 有延长精子寿命的作用。外源性葡萄糖可被精子利用,增强精子活力．延长精子寿命。56．7kPa CaCl2对精子活动有抑制作用,并引起精子聚集,该效应随着Ca^2 浓度升高而增强。     

Natural cytotoxic autoantibody against thymocytes in spontaneously hypertensive rats

A strain of SHR rats, which spontaneously develops hypertension and periarteritis nodosa, had a decreasing number of rosette-forming T cells in their thymuses and a progressive decline in cellular immune functions by aging. They were found to produce natural thymocytotoxic autoantibody (NTA) detected by a complement-dependent cytotoxicity test. This autoantibody occurred from 1 month of age and throughout life; the incidence was more than 60% of SHR rats at any age. Thymocytes from all six rat strains tested showed similarly high sensitivity to NTA but none of the strains tested produced NTA except the SHR strain. Rosette-forming thymocytes of WKA rats, which were separated by Ficoll gradient, showed much higher cytotoxic sensitivity to NTA than did whole thymocytes and nonrosetting thymocytes. The cytotoxicity of NTA was weak or negative for spleen cells, lymph node cells, bone marrow cells, and blood lymphocytes of WKA rats. However, the cytotoxic activity of NTA was completely absorbed with the thymus, spleen, lymph node cells, and brain homogenates and was partially absorbed with bone marrow cells, but not with liver and kidney homogenates. NTA in SHR rats was an IgM-globulin as determined by sensitivity to 2-ME treatment and by Sephadex G-200 column chromatography. These results suggest that NTA is responsible for the selective suppression of T-cell functions in SHR rats.     

Is it possible to modify serotonin receptor sensitivity?

It is possible to induce sub- and super-sensitivity of β-adrenergic receptors by long-term treatment with drugs acting on catecholamine systems. In contrast, analogous treatment with drugs acting on serotoninergic systems does not modify serotonin receptor sensitivity as measured by serotonin binding. Firstly, chronic 1-5HTP, the precursor amino acid, increases serotonin turnover but does not decrease serotonin binding. Secondly, chronic clomipramine, a predominantly serotonin uptake inhibitor also has no effect on serotonin binding. Thirdly, chronic metergoline, a selective serotonin antagonist in the cortex, does not induce supersensitivity.This apparent intractability of the serotonin receptor to changes after long-term treatment indicates a different post-synaptic regulatory mechanism than that found in catecholaminergic neurones. Furthermore, modification of serotonin receptor sensitivity is probably not relevant to the mode of action of antidepressant drugs. Rather, the response of pineal melatonin stimulation found after chronic clomipramine in these experiments implicates induction of β-receptor subsensitivity.