江豚背部小齿的超微结构与功能

长江江豚背部皮肤表面有一长条小齿,由1—3排组成。它是由表皮向体表突起而成。小齿区皮肤中的乳头深深伸入表皮,几达表面,它的高度在成体约占整个表皮厚度的70—80％,新生幼儿为84.6％。经研究,我们发现在小齿区皮肤中存在着大量类似于人类皮肤中的环层小体那样的被囊神经末梢和几种有鞘神经纤维束。根据这些结构,我们认为小齿是一种感觉器官,它并不能起到防止幼儿从母体背部滑落的作用。

用浮游植物的生产量估算武昌东湖鲢鳙生产潜力与鱼种放养量的探讨

本文根据浮游植物生产量求得对鲢、鳙的供饵能力,并通过浮游植物对鲢、鳙转化效率的计算,估算出武昌东湖鲢、鳙的生产潜力,进而求得武昌东湖鲢、鳙的合理投放量。作者求得东湖浮游植物全年对鲢、鳙的供饵能力是61,153吨(鲜重);由此估算出东湖鲢、鳙的生产潜力是789公斤/公顷以上,每年鱼种(四寸以上)的合理投放量,鲢是 209万尾,鳙是 110万尾。

中国粒鲇属Akysis鱼类二新种

<正> 粒鲇科Akyisidae鱼类是分布在东南亚地区的小型鱼类,包括三个属。其中大粒鲇属Achrochodomchthys Bleeker只产于苏门答腊岛、爪哇岛和加里曼丹岛。狭尾粒鲇属Breitensteinia Steindachner只产于苏门答腊岛和加里曼丹岛。粒鲇属Akysis Bleeker鱼类已记录的有下列8种:Akysis variegatus(Bleeker),1846;Akysis macronemus Bleeker,1860;Akysis pictus Gnther,1883;A

白暨豚上呼吸道的解剖和组织学的研究

白鱀豚上呼吸道具有前庭囊、鼻额囊及前颌囊三对气囊,没有副囊和连接囊。三对囊均右大于左,其中又以前庭囊最为显著。喉由甲状软骨、环状软骨、会厌软骨及一对杓状软骨组成,从喉腔壁的组织学观察发现有室皱襞(假声带)的存在。

黑龙江流域鲫鱼的种群变异和生态资料

<正> 黑龙江流域的鲫鱼,是渔获物中的主要粗成之一,约占总产量的20%。黑龙江流域的水利枢扭建成后,它将成为水库中的主要养殖对象,因此,调查研究鲫鱼的生活习性及其种群变异,对于今后的渔业利用是有很大益处的。一、种群的变异鲫鱼在黑龙江流域的分布极其广泛,各种不同的水体中都能棲息生存。在额尔古纳河,鲫鱼是捕捞的主要对象;在黑龙江,则主要是分布在干流相通的附属水体中。其它如达赖湖、镜泊湖、小兴凯湖、五大连池等湖泊里均有相当数量的鱼群。

中国淡水鱼寄生桡足类鳋科的研究

<正> 一.绪言桡足类的主要组成部分是自由生活的剑水溞(Cyclopoida)和镖水溞(Calanoida),它们都是鱼类的优良食料。另一部分就是营寄生生活的种类,其中有些对于鱼类的危害性很大。鳋科(Ergasilidae)是一群由自由生活的剑水溞演变成寄生生活的过渡类型,其幼虫及雄虫完全营自由生活,只有雌性的成虫始寄生在鱼体上。因此过去如 Gurney氏等认为它们是半寄生性的种类,是很正确的论断。

Localization and tracking of phonating finless porpoises using towed stereo acoustic data-loggers

Cetaceans produce sound signals frequently. Usually, acoustic localization of cetaceans was made by cable hydrophone arrays and multichannel recording systems. In this study, a simple and relatively inexpensive towed acoustic system consisting of two miniature stereo acoustic data-loggers is described for localization and tracking of finless porpoises in a mobile survey. Among 204 porpoises detected acoustically, 34 individuals (similar to 17%) were localized, and 4 of the 34 localized individuals were tracked. The accuracy of the localization is considered to be fairly high, as the upper bounds of relative distance errors were less than 41% within 173 m. With the location information, source levels of finless porpoise clicks were estimated to range from 180 to 209 dB re 1 mu Pa pp at 1 m with an average of 197 dB (N=34), which is over 20 dB higher than that estimated previously from animals in enclosed waters. For the four tracked porpoises, two-dimensional swimming trajectories relative to the moving survey boat, absolute swimming speed, and absolute heading direction are deduced by assuming the animal movements are straight and at constant speed in the segment between two consecutive locations.

Floral survey of the diatom genera Cymbella and Gomphonema (Cymbellales, Bacillariophyta) from the Jolmolungma mountain region of China

We report on taxa from the diatom genera Gomphonema and Cymbella (Cymbellales, Bacillariophyta) found in the Jolmolungma Mountain region of China. This region is unique for its diversity of habitats, which include rivers, springs, moist soil, snowfields, swamps and lakes. We re-examine diatom taxa found in samples first documented in 1973 (Jao et A, 1973) and incorporate recent taxonomic revisions from the literature. In the genera Gomphonema and Cymbella we report 113 species and varieties. Of these 113 taxa, 59 are new record for China; 1 new combination, Encyonema jolmolungmensis, is made. Morphometric data and habitat features are reported for each taxon. Their distribution is strongly correlated to their microhabitats.

Crustacean zooplankton size structure in aquaculture lakes: is larger size structure always associated with higher grazing pressure?

Crustacean zooplankton size structure in 27 aquaculture lakes was studied to test the hypothesis that larger size structure is associated with higher grazing pressure. Mean body length of crustaceans was positively correlated with increasing Chl a (r(2) = 0.40, P = 0.000) and TP (r(2) = 0.38, P = 0.000), contrary to the empirical studies. However, the ratio of zooplankton to phytoplankton biomass decreased significantly with increasing TP (r(2) = 0.27, P = 0.005) and mean body length (r(2) = 0.46, P = 0.000). Meanwhile, size structure showed no significant effect in explaining residual variations of phosphorus-chlorophyll relationship (P = 0.231). These results indicate that larger size structure was not always associated with higher zooplankton grazing pressure. It is likely that in aquaculture lakes crustacean zooplankton size structure was of minor importance in control of phytoplankton biomass, and it was mainly regulated by fish predation. The results showed in our study and the empirical studies might be a reflection of two different stages of lake eutrophication and fish predation intensity.

The functional divergence of two glgP homologues in Synechocystis sp PCC 6803

Glycogen phosphorylase (GlgP, EC 2.4.1.1) catalyzes the cleavage of glycogen into glucose-1-phosphate (Glc-1-P), the first step in glycogen catabolism. Two glgP homologues are found in the genome of Synechocystis sp. PCC 6803, a unicellular cyanobacterium: sll1356 and slr1367. We report on the different functions of these glgP homologues. sll1356, rather than slr1367, is essential for growth at high temperatures. On the other hand, when CO2-fixation and the supply of glucose are both limited, slr1367 is the key factor in glycogen metabolism. In cells growing autotrophically, sll1356 plays a more important role in glycogen digestion than slr1367. This functional divergence is also supported by a phylogenetic analysis of glgP homologues in cyanobacteria.

Mobilization potential of heavy metals: A comparison between river and lake sediments

Toxic metals introduced into aquatic environments by human activities accumulation in sediments. A common notion is that the association of metals with acid volatile sulfides (AVS) affords a mechanism for partitioning metals from water to solid phase, thereby reducing biological availability. However, variation in environmental conditions can mobilize the sediment-bound metal and result in adverse environmental impacts. The AVS levels and the effect of AVS on the fate of Cu, Cd, Zn, Ni in sediments in the the Changjiang River, a suboxic river with sandy bottom sediment and the Donghu Lake, a anoxic lake with muddy sediment in China, were compared through aeration, static adsorption and release experiments in laboratory. Sips isotherm equation, kinetic equation and grade ion exchange theory were used to describe the heavy metal adsorb and release process. The results showed that AVS level in the lake sediment are higher than that of the river. Heavy metals in the overlying water can transfer to sediments incessantly as long as the sediment remains undisturbed. The metal release process is mainly related to AVS oxidation in lake sediment while also related to Org-C and Fe-Mn oxyhydroxide oxidation in river sediment. The effect of sulfides on Zn and Ni is high, followed by Cd, and Cu is easy bound to Org-C. AVS plays a major role in controlling metals activity in lake sediment and its presence increase the adsorption capacity both of the lake and river sediments.

Comparative study on the effect of dietary lipid level on growth and feed utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Gunther)

An 8-week growth trial investigated the effect of dietary lipid level on growth performance of a carnivorous fish, Chinese longsnout catfish (Leiocassis longirostris Gunther) and an omnivorous fish, gibel carp (Carassius auratus gibelio). For each species, seven isonitrogenous semi-purified diets (455 g kg(-1) crude protein for Chinese longsnout catfish and 385 g kg(-1) crude protein for gibel carp) were formulated to contain 30, 60, 90, 120, 150, 180 or 210 g kg(-1) lipid. For Chinese longsnout catfish, feed intake (FI) decreased with increasing dietary lipid and there was no significant difference in feed intake from 90 to 210 g kg(-1) lipid. Specific growth rate (SGR) increased with dietary lipid level (P < 0.05) and the 150 and 180 g kg(-1) groups were the best. Feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) were higher at 180 g kg(-1) lipid. For gibel carp, FI decreased with increased dietary lipid and 180 and 210 g kg(-1) lipid groups showed lower values. SGR increased with dietary lipid level and the 150 and 180 g kg(-1) were the best. FCE was higher at 180 g kg(-1) lipid level. PRE increased with dietary lipid level and there was no significant difference in groups from 120 to 210 g kg(-1) dietary lipid. ERE increased with increasing dietary lipid level, and groups fed 120, 150 and 180 g kg(-1) lipid showed the highest values. In Chinese longsnout catfish, increase in dietary lipid level, resulted in increased carcass dry matter, crude protein, crude lipid and gross energy. In gibel carp, dry matter, crude protein, and crude lipid increased with dietary lipid level. Based on regression between SGR and dietary lipid, dietary lipid requirements for Chinese longsnout catfish and gibel carp were 142.6 and 140.5 g kg(-1), respectively.

STUDIES ON THE PURIFICATION AND RECLAMATION OF WASTE-WATER FROM A MEDIUM-SIZED CITY BY AN INTEGRATED BIOLOGICAL POND SYSTEM

The feasibility of an inexpensive wastewater treatment system is evaluated in this study. An integrated biological pond system was operated for more than 3 years to purify the wastewater from a medium-sized city, Central China. The experiment was conducted in 3 phases with different treatment combinations for testing their purification efficiencies. The pond system was divided into 3 functional regions: influent purification, effluent upgrading and multi-utilization. These regions were further divided into several zones and subzones. Various kinds of aquatic organisms, including macrophytes, algae, microorganisms and zooplankton, were effectively cooperating in the wastewater treatment in this system. The system attained high reductions of BOD5, COD, TSS, TN, TP and other pollutants. The purification efficiencies of this system were higher than those of most traditional oxidation ponds or ordinary macrophyte ponds. The mutagenic effect and numbers of bacteria and viruses declined significantly during the process of purification. After the wastewater flowed through the upgrading zone, the concentrations of pollutants and algae evidently decreased. Plant harvesting did not yield dramatic effects on reductions of the main pollutants, though it did significantly affect the biomass productivity of the macrophytes. The effluent from this system could be utilized in irrigation and aquaculture. Some aquatic products were harvested from this system and some biomass was utilized for food, fertilizer, fodder and some other uses. The wastewater was reclaimed for various purposes.

Structural evolution of mechanically alloyed nanocrystalline FeAl intermetallics

Nanostructured FeAl intermetallics were prepared directly by mechanical alloying (MA) in a high-energy planetary ball-mill. The phase transformations and structural changes occurring in the studied material during mechanical alloying were investigated by X-ray diffraction (XRD). Transmission electron microscopy (TEM) was employed to examine the morphology of the powders. Thermal behavior of the milled powders was examined by differential scanning calorimetry (DSC). Disordered Fe(Al) solid solution was formed at the early stage. After 30 h of milling, Fe(Al) solid solution transformed into an ordered FeAl phase. The average crystallite size reduction down to about 12 nm was accompanied by the introduction of the average lattice strain up to 1.7%. The TEM picture showed that the size of milled powders was less than 30 nm. (c) 2007 Elsevier B.V. All rights reserved.

The structure, morphology and Raman scattering study on Mn-implanted nonpolar a-plane GaN films

Dilute magnetic nonpolar GaN films with a Curie temperature above room temperature have been fabricated by implanting Mn ions into unintentionally doped nonpolar a-plane (1 1 (2) over bar 0) GaN films and a subsequent rapid thermal annealing (RTA) process. The impact of the implantation and RTA on the structure and morphology of the nonpolar GaN films is studied in this paper. The scanning electron microscopy analysis shows that the RTA process can effectively recover the implantation-indUced damage to the surface morphology of the sample. The X-ray diffraction and micro-Raman scattering spectroscopy analyses show that the RTA process can just partially recover the implantation-induced crystal deterioration. Therefore, the quality of the Mn-implanted nonpolar GaN films should be improved further for the application in spintronic devices. (C) 2009 Elsevier B.V. All rights reserved.