羊草草地生长季放牧山羊采食量和食性选择

在松嫩平原羊草草地,通过控制放牧实验对山羊的时限采食量和食性选择进行了研究。结果表明：（1）5－9月份,山羊的时限（1h）采食量平均为0.42kg干物质,其季节动态为5月份最低,随季节推移不断增大,8月份达到最大,9月份又有所减小;时限采食量基本上随放牧率减小而增大,但在最低放牧率小区有所减小。（2）山羊的食性选择随季节推移和放牧率不同而变化。（3）山羊对20－25cm高度草层的选择性最高;各高度草层的食性选择指数随季节推移和放牧率不同而变化;山羊对不同植物的高度选择性存在差异,但高度选择指数的最大值都在15－30cm范围内。     

ENVIRONMENTAL CONDITIONS, GROWTH AND PRODUCTION OF ANADARA SENILIS (LINNAEUS, 1758) IN A SENEGAL LAGOON

Two populations of Anadara senilis were sampled periodicallyin a lagoon of Senegal. Spatfall occurs in summer during therainy season. Population density decreases from about 50, 000.m^–2,two months after spatfall, down to 6, 750 one year later and750 after 28 months. The average growth, measured on the surfaceof the shell, following the umbo rim axis is 0.8 mm per month.The main reduction in growth rate occurs in winter and endsby the deposition of a growth ring. A second growth reductiontakes place during the rainy season and sometimes ends by aweak growth ring. The microgrowth increments are conspicuousand widest during spring equinox. They are not directly relatedto the tidal cycle, but it was impossible to determine if theyhave a tidal or a daily periodicity. (Received 11 February 1990; accepted 16 July 1993)     

Hypoderma actaeon: an emerging myiasis in roe deer (Capreolus capreolus)

Subcutaneous larvae of Hypoderma spp. (Diptera: Oestridae) were detected in the dorsal region in 10 roe deer, Capreolus capreolus (Artiodactyla: Cervidae), hunted in central Spain between January and March 2016. All larvae were found in the inner side of the hide during the skinning of the animals. The study of the morphological features of eight larvae of different stages collected from two animals allowed the identification of Hypoderma actaeon Brauer. The small size (4–5 mm) of some of the first instars suggests that the internal lifecycle of H. actaeon may be exclusively subcutaneous. This is the first confirmation of H. actaeon in roe deer; however, further studies to assess the spread of the parasite and to follow the evolution of this myiasis in roe deer are needed.     

具size结构种群竞争系统的最优控制

研究基于size结构的种群模型的控制问题,利用特征线法给出了系统的形式解,由Banach不动点定理和Gronwall不等式推导了系统及其共轭系统的适定性,并依靠法锥相关知识证明了最优控制问题解的存在必要条件.