Age-dependent use of local and global landmarks during escape: experiments using Columbian ground squirrels

How animals utilize their space often changes during ontogeny, perhaps resulting from alternative use of orientation mechanisms. This study investigated whether landmark-based navigation mechanisms were age-dependent in Columbian ground squirrels (Spermophilus columbianus). In field tests, young (1-2 years old) and adult (3-6 years old) animals had to find an escape burrow when either local, global, or both types of landmarks were obstructed. The comparison of escape times between age groups revealed that adult squirrels found escape burrow faster than young animals if global landmarks were available. However, if only local landmarks were present, young squirrels outperformed older animals. The comparison of escape time within each age group showed that obstruction of global or local landmarks lengthened escape time of adult squirrels. In contrast, young animals had longer escapes only when local landmarks were obstructed. The results suggested that the use of different types of landmarks was age specific.     

鄱阳湖小天鹅越冬种群数量与行为学特征

2012年10月-2013年3月,采用直接计数法对鄱阳湖小天鹅Cygnus columbianus种群数量分布进行了5次调查。结果显示,各调查点小天鹅的种群数量均不稳定,可能与食物丰富度、水位等相关。各次调查中以第2次调查观测到的小天鹅数量最多,合计10756 只;调查区域中以鄱阳县白沙洲自然保护区调查到的小天鹅数量最多。5次调查中鄱阳县的小天鹅数量均占每次调查总数的56%以上,平均2239.80 只。小天鹅在各保护区不同湖泊的数量分布存在时间差异,但分布仅局限在几个湖泊中。调查显示,小天鹅的幼体比例为29.04%(n=1150)。采用瞬时扫描法对小天鹅越冬期的行为进行了研究,其用于静止(43.12%)和取食(27.44%)行为的时间较多,用于运动(16.82%)和梳理(11.48%)行为的时间较少,用于社会行为(1.14%)的时间最少。在小天鹅的日间行为节律中,静止行为高峰出现在07:00-08:00和17:00-18:00时段,取食行为高峰出现在16:00-17:00。下午取食强度的增加与冬季夜间长和气温低有关,鸟类必须获得足够的能量以维持其夜间的能量消耗。对小天鹅成幼体行为分配进行检验,发现除社会行为差异显著(Z=-2.310,P=0.021)外,其余行为差异均不显著。但成幼体的行为节律有较大差异,主要体现在静止和取食行为上。     

Ca-ATPase activity and protein composition of sarcoplasmic reticulum membranes isolated from skeletal muscles of typical hibernator,the ground squirrel Spermophilus undulatus

Ca-ATPase activity in sarcoplasmic reticulum (SR) membranes isolated from skeletal muscles of the typical hibernator, the ground squirrel Spermophilus undulatus, is about 2-fold lower than that in SR membranes of rats and rabbits and is further decreased 2-fold during hibernation. The use of carbocyanine anionic dye Stains-All has revealed that Ca-binding proteins of SR membranes, histidine-rich Ca-binding protein and sarcalumenin, in ground squirrel, rat, and rabbit SR have different electrophoretic mobility corresponding to apparent molecular masses 165, 155, and 170 kDa and 130, 145, and 160 kDa, respectively; the electrophoretic mobility of calsequestrin (63 kDa) is the same in all preparations. The content of these Ca-binding proteins in SR membranes of the ground squirrels is decreased 3–4 fold and the content of 55, 30, and 22 kDa proteins is significantly increased during hibernation.     

Structure and development of the style base in Abildgaardia, Bulbostylis, and Fimbristylis (Cyperaceae,Cyperoideae, Abildgaardieae)

The Abildgaardieae tribe within the family Cyperaceae comprises six or seven genera, among which Abildgaardia, Bulbostylis and Fimbristylis pose a challenge regarding their morphological delimitation. Molecular phylogenetic analyses including species of Abildgaardieae are rare, but in most of those studies, Abildgaardia and Fimbristylis appear as more closely related to each other than to the Bulbostylis genus. Duration of the style base has been one of the most widely used characters for delimiting these three genera. The style base is a persistent structure in most species of Bulbostylis and deciduous in Abildgaardia and Fimbristylis. The reasons why the style base may persist or fall off have been scarcely discussed. The assumption that abscission layers are present in the style base of all three genera and the fact that tracheids have been observed in the style base of Bulbostylis suggest that this structure might have histological complexity. In view of this, a complete ontogenetic and anatomical study of the gynoecium has been carried out for all these three genera. It turned out that the style base is histologically simple in Abildgaardia, Bulbostylis and Fimbristylis and shows similar structure and development in all three genera. The fact that the style base has a shorter duration in Abildgaardia and Fimbristylis than in Bulbostylis might be related to the lower number of sclerotised cells that make up such structures in the mature fruit of the former two genera. Abscission of the style and style base may be the result of much simpler reasons than the differentiation of an abscission layer, resulting merely from mechanical shear force effects. Differences among genera have been observed in the shape of the style base and the development of the style. The histological simplicity of the style base is consistent with the homoplastic appearance of this structure in genera that are not closely related (e.g. Rhynchospora). Because of this, while the presence of the thickened style base seems to be a synapomorphy in species of Abildgaardieae, its persistence on or detachment from the fruit might have emerged repeatedly during this clade evolution and might not be a suitable character for genera delimitation.