Lake Erie water snakes revisited: Morph- and age-specific variation in relative crypsis

Summary Populations of water snakes (Nerodia sipedon insularum) on islands in western Lake Erie are variable in colour pattern, consisting of unbanded, intermediate, and banded morphs. In contrast, mainland populations (N. s. sipedon) consist solely of banded morphs. Previous investigators hypothesized that natural selection favoured unbanded morphs on exposed island shorelines and banded morphs in overgrown mainland habitats and that gene flow from mainland populations was responsible for the persistence of banded morphs on islands. To clarify the potential role of natural selection, I quantified relative crypsis among morphs and age classes of water snakes by comparing the size of patches making up their colour patterns with the size of patches in island and mainland backgrounds. This analysis reveals that if unbanded morphs are more cryptic than intermediate and banded morphs on islands, it is only in the young-of-the-year age class. For older snakes on islands and for all snakes on the mainland, unbanded morphs are consistently less cryptic than intermediate and banded morphs. Given these results, the net direction of selection in island populations should depend on the intensity of predation on different age classes of snakes. Overall, selection may favour unbanded morphs (e.g. if predation occurs primarily on young-of-the-year), intermediate and banded morphs (e.g. if predation occurs primarily on older snakes), or be weak or absent (e.g. certain combinations of predation on young-of-the-year and older snakes). Using estimates of relative crypsis to guide reanalysis of morph frequency data, I find support for the hypothesis that unbanded morphs are favoured by natural selection in island populations.     

Daily biphasic behaviour in keratin-feeding desert trogid beetles in relation to climate

Abstract. 1. Patterns of daily activity of two ectothermic species of the trogid genus Omorgus were studied in the Kalahari of southern Africa in summer. The relationship between time and type of activity, and environmental temperature, relative humidity and light intensity, was investigated.
2. Beetle activity was biphasic, with peaks in activity at sunset and sunrise in both species.
3. Afternoon activity coincided with high temperatures and low humidity and morning activity with minimum daily temperature and maximum humidity.
4. Afternoon activity, which peaked at about 34°C and 25% r.h., consisted predominantly of complex breeding behaviour and dispersal. High temperatures are necessary for these activities.
5. In the morning feeding predominated. At this time temperature was about 27°C and r.h. above 60%. High r.h. is important because it restricts respiratory loss of water, improves food (moist hair and skin keratin) quality and may compensate for faecal water loss.
6. No evidence of competition between the two species was found.     

Behavioral and Morphological Studies of Fetal Neural Transplants into SCN-Lesioned Rats

We have studied the effects of fetal neuronal grafts on the temporal pattern of drinking behavior of suprachiasmatic nuclei (SCN)-lesioned adult rats. Additionally, in an independent set of animals, the immunohistochemical staining for vasopressin, vasoactive intestinal polypeptide, and neuropeptide Y and the retinal connections to the hypothalamus were studied. The behavioral experiments indicate that anterior hypothalamic transplants induced reorganization of the temporal pattern of drinking behavior when placed in the third ventricle of adult hosts bearing complete SCN lesions, but not when placed in a cavity in the occipital cortex. Such rhythmicity persists only when the animals were recorded under constant darkness but not under constant light, indicating that the restored rhythmicity was generated endogenously but that the oscillator was extremely sensitive to light. Fetal occipital cortex induced reorganization of the temporal pattern of previously arrhythmic hosts, but it disappeared when the animals were recorded under constant light or constant darkness. It is clear that this rhythmicity was exogenous. In contrast to the cortical transplants, the hypothalamic transplants showed a morphological organization similar to that found in the normal hypothalamus regardless of their placement in the host brain. From these observations it is concluded that development of neocortex is more affected by environmental factors than that of the hypothalamus. Both hypothalamic and cortical transplants induced sprouting of retinal fibers into the anterior hypothalamus and the grafted tissue. It is possible that such fibers could be the neuroanatomical substrate by which rhythmicity is induced by cortical tissue.     

Glutamate dehydrogenase regulation in callus cultures of Nicotiana plumbaginifolia: effect of glucose feeding and carbon source starvation on the isoenzymatic pattern

Abstract. In callus cultures of Nicotiana plumbaginifolia , the activity of glutamate dehydrogenase was repressed by glucose, whereas, on the contrary, carbon and energy source deprivation induced a remarkable increase in specific activity. Definition of these two opposite types of response was made possible by the use of glycerol as a non-repressing carbon source: in this condition, glutamate dehydrogenase activity reached an intermediate level, which was similar to the derepressed values of activity obtainable when cultures were allowed to exhaust the glucose supply in the medium. Isoelectric focusing analysis revealed the existence of three different isoenzymatic patterns which could be correlated to the three different levels of specific activity: repressed (glucose), induced (carbon starvation) and intermediate (glycerol). Repression affected mainly the four more cathodic bands which were predominant in non-repressed conditions. The possible catabolic role of these isoenzymes is discussed.     

猫体感皮层神经元对同时刺激隐神经的A类和C类纤维的反应型式

记录了麻痹猫的体感皮层(SI)神经元的自发和隐神经的A类和C类纤维传入诱发放电(A-ED和C-ED)。用NCCVF分析神经元放电。结果表明,SI区神经元对同时刺激隐神经的A类和C类纤维的反应呈多种型式:(1)A-ED和C-ED共存,包括Ⅰ.A-ED和C-ED始终相互伴随出现;Ⅱ.在刺激之初,只出现A-ED,但是,当阻断A类纤维传入并由C类纤维传入诱发神经元放电后,再同时刺激A类和C类纤维时,A-ED和C-ED便同时出现。(2)A-ED制约C-ED,特点是,只要A-ED存在,C/ED就不出现。只有阻断A类纤维传入后,C-ED才产生。(3)单一A-ED,不管在什么刺激条件下,这类神经元都只有A-ED,而不产生C-ED 结论:根据反应型式的不同,可将SI区的神经元分为Ⅰ.A类和C类纤维传入同时驱动的神经元;Ⅱ.A-ED制约C-ED的神经元;Ⅲ.只由A类纤维传入驱动的神经元。     

γ-氨基丁酸、荷包牡丹碱和L-谷氨酸钠对猫和家兔同侧和对侧图形视觉诱发电位的影响

在猫和家兔大脑半球一侧视区17/18交界处施加γ—氨基丁酸(GABA)、荷包牡丹碱和L—谷氨酸钠,以及用氯化钾和冷冻阻遏的方法,记录对侧和同侧皮层相应处图形视觉诱发电位(PVEP)的变化。讨论了GABA、荷包牡丹碱和L—谷氨酸钠对猫和兔的对侧和同侧PVEP的影响。     

一种复合神经元网络结构的并行动力学及快速学习算法

提出两种功能互相不同的神经细胞组成的复合神经元网络(CNN)模型;导出一种特殊结构的CNN的并行动力学;而且证明了它的稳定性。在这些结果基础上,得到快速的假逆矩阵学习算法。计算机仿真试验证实学习算法与动力学稳定性的正确性,并表现出良好的容错性能与存储容量。     

缀块性和缀块动态:Ⅱ.描述与分析

在生态学中,“缀块”(patch)的概念早已在植被群落和海洋生态系统中浮游动植物空间分布研究中广泛应用。A.S.Watte早在1947年就强调缀块在植物群落结构分析中的重要性。实际上,缀块存在于地球的任何地方。森林可