南非克留格尔国家公园马羚的种群下降:一个备择假说

本研究报道了1979年以来南非克留格尔国家公园暂时性沼泽边界对马羚( Hippotragus equinus equinus)种群下降的影响。干旱和由此导致的生境退化以及随之产生的食草动物之间的采食竞争是解释马羚种群数量下降的可能假说。我们认为,确定马羚的生境斑块选择并测定影响暂时性沼泽边界变化与马羚种群下降的关联性因子,可解释马羚种群下降的备择假说。在北部平原区,边界呈斑块状分布的沼泽是马羚的高矿质采食源。实施狩猎管理工程期间,人工做成的大多数水道分布于沼泽边界及其附近,造成马羚与其它食草动物的采食竞争和天敌捕食压力的增高。旱季降雨的缺乏,加上沼泽边界区域采食竞争以及天敌捕食压力,是引发马羚在北部平原生境普遍退化之前其种群提前下降的因素[动物学报52 (2) : 406 -409 , 2006]。     

Connecting morphology, function and tooth wear in microchiropterans

A key objective in understanding the dentition of mammals is the ability to predict the function of teeth from their shape. Very few studies have used dental measurements that allow the prediction of comparative tooth effectiveness, particularly when modification in shape due to tooth wear is considered. Here, dental parameters are used in which a change in the parameter is readily interpretable in terms of change in factors such as increased force or energy required for cusps or crests to break down food. The functional parameters were measured for 3-D digital tooth reconstructions of the upper molars of the microchiropteran Chalinolobus gouldii at various stages of tooth wear. The changes in the majority of the parameters, such as decreased tip, edge and cusp sharpnesses, cusp occlusion relief, rake angle and fragment clearance, predict a deterioration in efficacy with increased wear. This conclusion has not been possible with alternative approaches; for instance, there was no significant change in crest length with wear, and so no change in function would be predicted from that measure. Some of the parameters did not change significantly with heavy wear, such as capture area of a crest, pointing to geometrical and design characteristics for the maintenance of shape with wear in the dilambdodont tooth form. Attrition and abrasion can be considered as wear on the relief and rake surfaces of tribosphenic-like crests, respectively. The differences in function of these two surfaces account for the differences in wear patterns.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 85 , 81–96.     

Colchicine-Induced Effects in the Scaly Green Alga, Mesostigma viride: Loss of Microtubules and Paracrystal Formation

The effects of colchicine treatment upon the scale-covered,disc-shaped prasinophyte, Mesostigma viride, are profound. 2–4mg ml^–1 of the alkaloid induces the loss of pit and othercytoskeletal microtubules within 6 h of treatment. Subsequently,the organism loses its distinctive shape and becomes ellipsoidal.During treatment, prominent, intracellular crystalline bandsconsisting of 25 nm hexagonal subunits form in close proximityto the former pit region. The Golgi apparatus remains intactduring colchicine application but scale ontogenesis is distinctlyaltered. All effects are reversible upon removal of colchicine.A discussion of the cytoskeletal role of parallel series ofmicrotubules in unicellular algae is presented. Key words: Mesostigma, Colchicine, Cytoskeletal