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)     

Chemical Defense and the Persistence of Pioneer Plant Seeds in the Soil of a Tropical Cloud Forest

We present evidence that differences in soil seedbank persistence among pioneer plants in the cloud forest of Monteverde, Costa Rica, are influenced by differences in seed chemical defense. We used extracted seed chemicals from Bocconia frutescens (Papaveraceae), Guettarda poasana (Rubiaceae) , Phytolacca rivinoides (Phytolaccaceae) , Urera elata (Urticaceae) , Cecropia polyphlebia (Cecropiaceae), and Witheringia meiantha (Solanaceae) to assess seed chemical defense in two ways: (1) a plant pathogen inhibition assay using Pythium irregulare ; and (2) a brine shrimp toxicity assay using Artemia salina . The combined performance of each species in the two assays positively correlated with seedbank persistence. In the pathogen assay, mycelium growth was reduced when Pythium was cultured on media containing seed extracts from the three species with the greatest seed longevity in the soil ( i.e., Bocconia , Guettarda, and Phytolacca ). Bocconia , the most persistent species, was the only species that contained chemicals toxic to brine shrimp , an indication of defense against arthropods. We focused on Bocconia defense by isolating the chemicals toxic to brine shrimp and identified them as dihydrosanguinarine, dihydrochelirubine, and dihydrochelerthrine. We found these alkaloids in Bocconia seeds at much higher concentrations (∼50 mg/g seed material) than in leaves. These chemicals are likely responsible for the exceptional longevity of Bocconia seeds in the soil. Phytolacca and Guettarda seeds also remain viable in the soil for long periods probably due to antipathogen chemicals detected in our analyses. In contrast, the species that do not persist ( i.e., Urera , Cecropia , and Witheringia ) lacked seed defensive chemicals in our assays.
Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp .     

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.     

Electron microscopy of cellular immunity reactions in B-cell deprived rabbits. Thymus derived antigen reactive cells, their micro-environment and progeny in the lymph node.

Three times sublethal total body X-irradiation with thymus shielding--at 14 days' intervals--established an 'isolated T-cell system'. Cellular immunity reactions in draining lymph nodes of rabbits have been analyzed at the ultrastructural level after challenge with horse spleen ferritin, the chemical sensitizer, 2-phenyl-4-ethoxymethylene-5-oxazolone and after skin allografting. A basic pattern of interdigitating cells (IDC) is described as a specific constituent of the thymus-dependent areas of peripheral lymphoid tissue. Their ultrastructural features and presumable functional relationship to the afferent loop of cellular immunity reactions are presented. The differentiation pathway of two T-cell lines is shown and discussed in relation to cellular and thymus-dependent humoral immunity reactions.