Conservatism of sites of tRNA loci among the linkage groups of severalDrosophila species

Summary The sites of seven tRNA genes (Arg-2, Lys-2, Ser-2b, Ser-7, Thr-3, Thr-4, Val-3b) were studied by in situ hybridization.¹²⁵I-labeled tRNA probes fromDrosophila melanogaster were hybridized to spreads of polytene chromosomes prepared from fourDrosophila species representing different evolutionary lineages (D. melanogaster, Drosophila hydei, Drosophila pseudoobscura, andDrosophila virilis). Most tRNA loci occurred on homologous chromosomal elements of all four species. In some cases the number of hybridization sites within an element varied and sites on nonhomologous elements were found. It was observed that both tRNA ₂ ^Arg and tRNA ₂ ^Lys hybridized to the same site on homologous elements in several species. These data suggest a limited amount of exchange among different linkage groups during the evolution ofDrosophila species.     

农业生态系统中新物种引进的初步探讨

在现有的农业生态系统中,引进某些新物种,往往可以使整个系统的功能发生变化。如果新物种引进得当,则可产生良好的效果,系统功能得以改善,效益提高;反之,则会造成人力、物力、财力的损失,削弱系统的功能,甚至可能遗患无穷。因此,对农业生态系统中     

Lingulid shell mediation in clay formation

Organophosphatic shells of the brachiopod Lingula squarniformis , collected from Scottish Lower Carboniferous shales and mudstones of intertidal to sublittoral provenance, have been studied to ascertain chemico-structural changes resulting from fossilization. Enough original shell has been preserved at ultrastructural and molecular levels to confirm that Carboniferous and Recent integuments are homologous with stratiform successions of apatitic to organic laminae forming rhythmic sets. One of the main organic constituents, the acidic, hydrophilic gel glycosaminoglycans (GAGs), is the dominant component towards the tops of rhythms. During fossilization of the Carboniferous shells, GAGs degraded incrementally without disturbing apatitic ultrastructures, and the spaces so created became partly filled with sheets of recrystal-lized apatite with some kaolinite or with books and plates of kaolinite. The kaolinite in the shells contrasts with the illite of the entombing sediments and suggests that degrading acidic GAGs mediated in clay formation in situ . The sediments also contain framboidal pyrite, which is virtually absent from the shells themselves but is usually even more abundant, with a greater range of trace metals, in the sedimentary fills of complete shells. This imbalance suggests mediation by another gel, the glycocalyx, secreted by the inner epithelium of the brachiopod mantle. The glycocalyx would have lined the shell interior and could have served as a sorption film for dissolved metals precipitated as compounds on decomposition of body tissue.     

Macrophytes and flood plain water dynamics in the River Danube ecotone research region (Austria)

In the ecotone research region of the Danube in Austria (Man-and-the-Biosphere (MaB)- project 5/21, Austrian Academy of Science) the macrophytes are one of the most important groups of organisms investigated. The species composition and the plant mass in hydrologically dynamic, and in predominantly stagnant sections of a system of lateral branches and sloughs were studied. This study showed that areas protected from frequent disturbance by floods had a greater number of species and higher biomass of aquatic macrophytes. Some species were shown to be evenly distributed throughout the branch system, whereas other species tended to form rare, but large singular patches. A set of new data elaboration techniques enabled us to describe the distribution pattern of the aquatic vegetation in this large branch system of the River Danube.     

加藤蝉属二新种：同翅目：蝉科

本文记述加藤蝉属２新种：太白加藤蝉Ｋａｔｏａ ｔａｉｂａｉｅｎｓｉｓ与寡刺加藤蝉Ｋ．。模式标本存于西北农业大学昆虫博物馆与神经农学院植物保护系。     

海南省库蠓二新种(双翅目:蠓科)(英文)

本文描述在海南省发现的库蠓二新种:尖峰库蠓和开裂库蠓。     

A comparative study of the glomerular peripolar cell and the renin-secreting cell in twelve mammalian species

The peripolar cell is a glomerular epithelial cell situated within Bowman's capsule at its vascular pole. It is believed to be a secretory cell which forms part of the juxtaglomerular apparatus. Scanning electron microscopy was used to perform a comparative study of the morphology and number of peripolar cells in twelve mammalian species. The number of renin-secreting cells in kidney sections stained by renin antibodies and immunocytochemistry was counted. There was a marked inter-species variation in the number, size and appearance of peripolar cells. They were largest and most abundant in sheep and goat and fewest in dog, cow and human. There was no correlation between the numbers of peripolar cells and renin-secreting cells. This does not support the view that the peripolar cell is part of the juxtaglomerular apparatus.     

Transpiration measurements on apple trees with an improved stem heat balance method

Since the late eighties a handy and user-friendly sap flow meter (Dynagage®) is on the market which can quantify 0205 the sap flow through intact plant stems, based on the stem heat balance method. The documentation about its accuracy and reliability, however, is still too limited to use it as a standard method in field experiments with apple trees. We therefore tested this commercial system on potted apple trees (Malus domestica L.; cv. Red Elstar and Jonagold; on rootstock M9 vf) with stem diameters of 1.8 to 4 cm. The measured sap flow was compared with mass loss measured by an automated balance, supposing the total mass loss of the trees was equal to the water loss by transpiration. The results revealed three major problems:

中国盲走螨属一新种和二新纪录：蜱螨亚纲：植绥螨科

本文记述我国植绥螨科盲走螨属Ｔｙｐｈｌｏｄｒｏｍｕｓ一新种和中国二新纪录：鲁盲走螨Ｔ．ｌｕｅｎｓｉｓ ｓｐ．ｎｏｖ．,甲胄盲走螨Ｔ．ｌｏｒｃａｔｕｓ,肥厚盲走螨Ｔ．ｈｉｇｏｅｎｓｉｓ。标本保存于上海复旦大学环境和资源生物系。