火烧、施肥、刈割及其交互作用对草原土壤净氮矿化的影响

我国北方温带草原地处干旱半干旱区，是欧亚大陆草原生物区系的重要组成部分，也是我国重要的畜牧业生产基地。土壤氮素作为陆地植物生长和生态系统初级生产力的主要限制因子之一，了解其矿化和可利用性对各种人为干扰因素的响应，有助于我们充分认识草地退化机理，维持草场生产力并进一步促进畜牧业的可持续发展，为草地恢复、重建和维护提供理论依据。本实验在中国科学院内蒙古草原生态系统定位研究站的多年围封退化样地，分别实施了火烧、施肥、刈割及其交互作用的人为干扰处理，利用原状土野外培养的方法，在两年时间中，研究不同的人为干扰因素（火烧、施肥、刈割及其交互处理）对土壤净氮矿化作用的影响。 火烧显著影响草原的氮循环过程，季节和年际的气候变化参与调节氮循环对火烧处理的响应。多年围封后的初次人工火烧处理显著降低了第一个生长季（2006 年生长季）和其后冬季的土壤净氮矿化速率，但是，火烧处理仅在冬季对土壤无机氮含量产生显著降低作用；2007 年生长季，火烧处理对土壤净氮矿化速率和土壤无机氮含量没有显著作用，但是在个别月份，不同的火烧频率对土壤净氮矿化速率和无机氮含量的影响表现出差异。2006 年生长季，未火烧样地和火烧样地净氮矿化积累量分别为3.07±0.26 g N m-2 和2.18±0.21 g N m-2；冬季，未火烧样地和火烧样地净氮矿化积累量分别为1.18±0.25 g N m-2 和0.51±0.08 g N m-2；2007 年生长季，未火烧样地（BC）、每年火烧样地（B1）和两年一烧样地（B2）净氮矿化积累量分别为1.32±0.21 g N m-2、0.54±0.30 g N m-2 和 0.77±0.24 g N m-2。较为湿润的2006 年生长季的净氮矿化积累量显著高于较为干旱的2007 年生长季，冬季也存在相当丰富的净氮矿化积累量。我们推论，长时间围封后的单次火烧处理对土壤净氮矿化作用的影响可能是短效的，但是年际间气候变化对土壤净氮矿化作用影响显著。 施肥显著提高了土壤的无机氮含量，并且与施肥梯度呈显著正相关关系。施肥对土壤无机氮含量的影响具有累加效应，第一次施肥和第二次施肥后的首次取样，+N5.25 、+N17.5 、+N28.0 三个施肥梯度的样地土壤无机氮含量比未施肥样地分别高出56%、219%、1054%和514%、891%、1811%。施肥处理在2006 年和2007 年对土壤净氮矿化作用都没有显著影响，仅在2007 年的个别月份有一定效果。以上结果说明，无机氮肥的添加可以明显提高土壤中无机氮的含量，满足植物生长的需求，但对于土壤氮转化过程的影响可能还要受其它环境和生物因子的制约。 刈割对土壤无机氮含量和净硝化速率没有显著作用，对土壤净氮矿化速率仅在个别月份表现显著效果。2007 年生长季，未刈割样地和刈割样地净氮矿化积累量分别为1.32±0.21 g N m-2 和1.08±0.35 g N m-2，不存在显著差异。我们推论，长期围封后的单次刈割处理在短期内对生长季的土壤氮动态仅有微弱影响，并且这种效果还可能受水分因素的制约。 火烧、施肥、刈割的交互处理在2007 年生长季对土壤无机氮含量产生显著作用，但是，对土壤净氮矿化速率和净硝化速率没有显著效果，然而，在不同的取样时间，火烧、施肥、刈割的交互处理对土壤无机氮含量、净氮矿化速率和净硝化速率的影响存在显著差异，说明火烧、施肥、刈割的交互处理对土壤无机氮和净氮矿化作用的影响可能受各种环境因子的制约，尤其是在水分相对缺乏的半干旱内蒙古草原，非生物因子和生物因子可能共同影响着土壤中的氮平衡。 本研究初步分析了长期围封后火烧、施肥、刈割及其交互处理对土壤净氮矿化的影响，初步探究了人为干扰和环境气候变化对土壤可利用性氮的调节作用，为科学地进行禁牧、割草、人工养份添加等草原管理提供了数据支持。

Effect of decapsulation on viability and hatching performance of Artemia cysts at different salinity levels

Artemia cysts were produced from the traditional solar salt works of Bangladesh through different fertilization treatments were tested for viability and hatching performance in different forms, such as processed and preserved, processed and decapsulated and unprocessed and undecapsulated. Decapsulated cysts performed maximum hatching (86.0%) in 20ppt salinity during 48 hours of incubation. The hatching percentage by the unprocessed and undecapsulated cysts were very low (12.0- 18.7%) in all the tested salinity grades.

Effects of culture treatments on HUFA levels in Artemia cysts

Artemia cysts (of GSL, Utah, USA origin) were produced from the modified traditional solar salt works of Bangladesh during winter months through different feeding/fertilization treatments (T1, T2, T3, T4 ) were analyzed to understand the effects of treatments on their fatty acid profile. Palmitic, Linolenic, Eicosapantaenonic and Docohexaenoic acids (mg/g. DW) were found highest for the cysts in T1 (16.0% ±1 .36), T2 (14.7% ±0.47), T3 (4.7% ±0.40) and T4 (0.7% ±0.06) treatments, respectively. High amount of 18:3(n-3) acids in the cysts of all sources proves to be freshwater type of the cysts. The presence of marine type essential fatty acids in the cysts of all sources were found low for 20:5n-3 (3.7-4.7%) and very low for 22:6n-3 (0.09-0.7%). No significant variation was observed for 16:0 acids within the treatments, but for 18:3(n-3) acid, the variation was found highly significant (P= 0.0052) between T2 and T4 treatments. For 20:5(n-3), only variation between T2 and T4 was found insignificant (P=0.1161), but between other treatments, significant variation was observed between T2 and T4 (P=0.0241), T2 and T4 (P=0.0022) and T1 andT4 (P=0.0161). No significant variation was found in other treatments.

Manipulation of chromosomes in fish: review of various techniques and their implications in aquaculture

Human ingenuity has made it possible to advent the chromosome manipulation techniques to produce individuals with differing genomic status in a number of fish using various causal agents such as physical shocks (temperature or hydrostatic pressure), chemical (endomitotics) and anesthetic treatments either to suppress the second meiotic division shortly after fertilization of eggs or to prevent the first mitotic division shortly prior to mitotic cleavage formation. This results in the induction of polyploidy (triploidy and tetraploidy), gynogenesis (both meiotic and mitotic leading to clonal lines) and androgenesis in fish population. The rationale for the induction of such ploidy in fish has been its potential for generating sterile individuals, rapidly inbred lines and masculinized fish, which could be of benefit to fish farming and aquaculture. In this paper, these are critically reviewed and the implication of recently developed chromosome manipulation techniques to various fin fishes is discussed.

Effects of artificial feeds on production of fishes in polyculture

A study on the effects of artificial feeds on the growth and production of fishes in polyculture in 6 ponds along with some limnological conditions was conducted. Species of Indian and Chinese major carps (Labeo rohita, Catla catla, Cirrhinus mrigala, Hypophthalmicthys molitrix) and catfishes (Clarias batrachus, Clarias gariepinus) were stocked in 6 ponds. Stocking rate in both cases were 32044 fingerlings per hectare. Ratio of species of Rui:Catla:Mrigal:Silver carp:African Magur:Local Magur=25%:25%:5%:25%:14%:6%. Fertilization and artificial feeds were given in 3 ponds (treatment I) and only fertilization was done in other 3 ponds (treatment II). Average yield/ha/yr was 7.903 m.ton in case of fertilization and artificial feeding application and 3.374 m.ton in case of only fertilization application. Urea, TSP and cow dung were applied fortnightly at the rates of 400 kg/ha/yr, 2000 kg/ha/yr and 4000 kg/ha/yr respectively. Wheat bran, rice bran and mustard oil cake were given daily as an artificial feed in treatment I. Whereas treatment II was conducted without any artificial feed. Ratio of artificial feed was wheat bran:rice bran:oil cake=2:2:1 (by wt). Absence of artificial feed in 3 ponds under treatment II seriously affected the growth and production of fish.

Water quality management on the enhancement of shrimp (Penaeus monodon Fab.) production in the traditional and improved-traditional ghers of Bangladesh

On-farm research on enhancement of P. monodon production through water quality management was carried out in five ghers of Paikgacha, Khulna. Based on the prevailing condition of the ghers, lime in the form of CaCO(sub 3), urea and TSP were used as the major inputs to minimize the soil-water acidity and to ensure the availability of natural food particles in the water bodies. Exchange of water at required level also practiced for the qualitative improvement of culture water. Ghers of varying sizes showed that water quality management and fertilization have a positive impact on production performance of P. monodon (61.59% increment) that yielded an average production of 385.43 kg/ha/crop against the present traditional rate of 238.50 kg/ha/year.

Studies on the performance of Ovatide on breeding of Indian major carps

The paper deals with the experimental studies on breeding of Indian Major Carps - Catla catla (Valenciennes), Labeo rohita (Hamilton), Cirrhinus mrigala (Hamilton), & Labeo calbasu (Hamilton) with the help of 'Ovatide' which is being used as an alternative inducing agent for commercial seed production. This study has been conducted for six consecutive months (April - September, 2000) in a stone-pitched breeding channels of a farm located at Midnapore District, West Bengal. The doses of 'Ovatide' (0.5 ml/kg of fish weight) remained same for each female species during the entire study period and males were released without any dose. The physicochemical parameters of water during different months were estimated. The latency period and fertilization percentage varied in different months and species. The results confirmed that 'Ovatide' can be used successfully in a much more cost-effective way for induced breeding of carps, even in rural fish farms with morrum-pitched breeding channels.

Proteomic Analysis of Proteins Involved in Spermiogenesis in Mouse

Spermiogenesis is a unique process in mammals during which haploid round spermatids mature into spermatozoa in the testis. Its successful completion is necessary for fertilization and its malfunction is an important cause of male infertility. Here, we report the high-confidence identification of 2116 proteins in mouse haploid germ cells undergoing spermiogenesis: 299 of these were testis-specific and 155 were novel. Analysis of these proteins showed many proteins possibly functioning in unique processes of spermiogenesis. Of the 84 proteins annotated to be involved in vesicle-related events, VAMP4 was shown to be important for acrosome biogenesis by in vivo knockdown experiments. Knockdown of VAMP4 caused defects of acrosomal vesicle fusion and significantly increased head abnormalities in spermatids from testis and sperm from the cauda epididymis. Analysis of chromosomal distribution of the haploid genes showed underrepresentation on the X chromosome and overrepresentation on chromosome 11, which were due to meiotic sex chromosome inactivation and expansion of testis-expressed gene families, respectively. Comparison with transcriptional data showed translational regulation during spermiogenesis. This characterization of proteins involved in spermiogenesis provides an inventory of proteins useful for understanding the mechanisms of male infertility and may provide candidates for drug targets for male contraception and male infertility.

Cryopreservation of sperm of common carp, Cyprinus carpio and silver barb, Barbonymus gonionotus for genetically improved seed production

Experiments were conducted to develop and standardize the protocols for cryopreservation of sperm of common carp, Cyprinus carpio and also for using the cryopreserved sperm for fertilization of eggs. Nine extender solutions as Alsever's solution, kurokura-1, kurokura-2, urea egg-yolk, egg-yolk citrate, 0.6% glucose, 0.9% NaCl, Ma and Mb, and five cryoprotectants namely ethanol, methanol, dimethylsulfoxide (DMSO), dimethylamine (DMA) and glycerol were tested. The cryoprotectants were mixed at 10% concentration of the extenders (v/v) to make the cryodiluents. Milt and cryodiluents were mixed at a ratio of 1:9 for Alsever's solution, kurokura-1, kurokura-2, 0.6% glucose and 0.9% NaCl, 1:4 for urea egg-yolk, egg-yolk citrate, Ma and Mb. Among the cryodiluents Alsever's solution mixed with either ethanol or methanol was found to be suitable and it produced more than 90% and 80% spermatozoan motility at equilibrium and post-thaw periods, respectively. Kurokura-1 and kurokura-2 when mixed with the same cryoprotectants showed good spermatozoan motility at equilibrium period (80-90%) but the motility was reduced (30-55%) at post-thaw state. Other extenders did not produce acceptable sperm-motility and in some cases the frozen milt became clotted. Different dilution ratios (1:1, 1:2, 1:4, 1:5, 1:7, 1:9, 1:12, 1:15, 1:20) were formulated for obtaining a suitable milt dilution, the dilution ratio of 1: 9 (milt : cryodiluent) demonstrated the highest post-thaw spermatozoan motility (80%) in Alserver's solution. The optimum concentration of cryoprotectants in the cryodiluents was determined, 10% concentration level was found to be effective to produce the highest number of spermatozoan motility in comparison to the other concentrations (5%, 15%, 20% 30%). Sperm preserved with the cryodiluent Alsever's solution along with either methanol or ethanol was found to be effective to fertilize eggs and produce hatchlings. The hatching rates ranged between 1.48% and 14.76%, compare to control. The fish produced through use of cryopreserved sperm and normal sperm were found to grow well and no significant (P<0.05) growth difference was observed between them. In case of silver barb, Barbonymus gonionotus, sperm tested against six extenders such as egg-yolk citrate, urea-egg-yolk, kurokura-1, kurokura-2, 0.9% NaCl and modified fish ringer (MFR) solution. Cryoprotectants used were the same as those of C. carpio. Milt was diluted with the cryodiluent at a ratio of 1:4 for egg-yolk citrate and urea-egg-yolk, 1:5 for kurokura-1 and 1:9 for 0.9% NaCl, MFR and kurokura-2. The cryoprotectant concentration was maintained at 10% of the extender (v/v) in all the cases. Among the extenders, egg-yolk citrate and urea-egg-yolk mixed with 10% DMSO, methanol and ethanol produced 50% post-thaw spermatozoan motility, whereas DMA and glycerol provided only 10% motility. Trials on milt dilution ratio and cryoprotectant concentration are being conducted. Fertilization trials are also underway.

Comparison of two hormone preparations on the reproductive performance of air breathing catfish Clarias batrachus (Lin.)

Two hormone preparations viz. Human Chorionic Gonadotropin (HCG) and pituitary gland (PG) suspension were compared for their comparative efficacy on the breeding performance of a air breathing catfish Clarias batrachus. It was found that HCG induced fish gave better ovulation response than PG. Both fertilization and hatching of eggs were significantly (p

Early developmental stages of Nandus nandus (Ham.)

In order to study the early developmental stages of Nandus nandus an experiment was conducted, where eggs and milt were obtained from the laboratory reared N nandus by stripping after 15 hours of 150 mg/kg body weight of carp PG extract injection. Then the eggs were fertilized in the laboratory and subsequent developmental stages were studied. First cleavage (two cell), four cell, eight cell, sixteen cell and multi cell stages were found 30, 50, 70, 105 and 160 minutes after fertilization respectively. Morula, early gastrula, middle gastrula, late gastrula and yolk plug stages were found 5, 8, 9, 11 and 13 hours after fertilization respectively. Hatching occurred within 20±2 hours after fertilization, and larvae were measured 1.60 mm in diameter. After one hour of hatching two melanophore bands were found at the caudal region of the body of the larvae. Eyes were first observed in l 0 hours, pectoral and pelvic fin buds appeared in 22 hours and well developed in 38 hours old larvae. Mouth cleft and brain lobes were visible when the larvae were 34 and 38 hours old respectively. Myomeres partially appeared in 16 hours, which were clearly visible in 74 hours old larvae. Larvae started wandering and searching for food after 56 hours of hatching. The yolk sac was completely absorbed when larvae became 62 hours old.

Effects of different dietary levels of vitamin E on the breeding performance of Heteropneustes fossilis (Bloch)

Experiments on the study of different dietary levels of vitamin E on the growth and breeding performance of Heteropneustes fossilis brood fish were carried out in two phases. The first phase consisted of studying its ovarian development and the second phase on breeding performance. Sixty female fishes were stocked in twelve experimental chambers of a raceway. The effects of four dietary vitamin E levels viz. 0 (served as control), 50, 100 and 200 mg/kg feed, on the somatic growth, ovarian development of brood fish and on their breeding performance were studied. Each treatment had three replications. It was observed that body growth in terms of length and weight was best with 0 mg vitamin E/kg feed and 200 mg vitamin E/kg of feed gave poorest result. The gonado-somatic index and fecundity, however, was highest in the fish fed with 100 mg vitamin E/kg of feed. In case of breeding performance such as ovulation rate, fertilization rate, hatching rate and survival rate, the best result was obtained with 200 mg vitamin E/kg of feed. The overall result of this experiment indicates that 200 mg vitamin E/kg of feed is the best vitamin E dose for H fossilis brood and vitamin E content has a positive impact on ovarian development.

Production of triploid African catfish, Clarias gariepinus (Burchell), using chromosome manipulation techniques

An experiment was conducted to induce triploidy in African catfish, Clarias gariepinus, using heat shock and cold shock techniques. Cold shock at a temperature of 0± 1°C and 5±1°C for a duration of 15, 30, 45 and 60 min and heat shock at a temperature of 40±0.5°C and 41 ±OS C for a duration of 1, 2 and 3 min was given to induce triploidy 5 min after fertilization. Maximum percentage of triploids (91.4%) were obtained in the heat shock at a temperature of 40±0SC for a duration of 1 min whereas cold shock at 0± 1 C for a duration of 60 min yielded 90% of triploids. Chromosome analysis revealed that diploids have 54 chromosomes and triploids have 81 chromosomes. The erythrocyte measurements of the minor axis and major axis were 1.17 times larger in treated fish than in controls. The growth studies showed that the growth rate was not significantly affected in triploids.

Comparison of effectiveness of heat and cold shocks applied in the induction of gynogenesis in Clarias gariepinus (Burchell)

An experiment was conducted to optimize the procedure of gynogenesis in African catfish, Clarias gariepinus by suppressing meiotic and mitotic cell divisions in fertilized eggs. Gynogensis was conducted by fertilizing normal eggs with UV-irradiated sperm followed by either heat or cold shocking Irradiation of spermatozoa was given for a duration of 1 min and the eggs were fertilized in vitro. Cold shock at a temperature of 3± 1°C for a duration of 30 and 60 min and heat shock at a temperature of 39± 1°C for a duration of 1 and 2 min was applied to induce diploidy. Higher percentage of hatching (68.66) was observed for meiotic gynogens at a shock temperature of 39± 1°C for a duration of 1 min, 5 min after fertilization (af). Higher percentage of mitotic gynogenetic induction (15.33) was observed at a temperature shock of 39± 1°C for a duration of 1 min, 30 min af.

Breeding biology and monosex male seed production of Genetically Improved Farmed Tilapia (GIFT) strain of Oreochromis niloticus L. in Bangladesh

A study on the breeding biology of the GIFT strain of Nile tilapia, Oreochromis niloticus, was conducted for a period of five months. The sex ratio of the parent individuals was optimized for performance in spawn production, where the best results were obtained with a sex ratio of female to male of 4:1 compared to those of 3:1 and 2:1. The diameter of eggs obtained from the GIFT stock had major and minor axes of 2.19±0.09 and 1.72±0.07 mm, respectively, with no significant differences between the treatments. The average number of eggs produced was 392±22 per female, with fertilization and hatching rates ranging between 94-96% and 85-88%, respectively. No significant variation was observed between the treatments. Breeding frequencies per female in the three treatment groups ranged between 10-40 days and the highest value was obtained at a female to male sex ratio of 4: l. In an other experiment, l7 aMethyltestosterone (MT) was applied orally to the fry at their first feeding stage with treatments- 1, 2, 3 and 4 at the dosage of 100, 80, 60 and 40 mg/kg feed respectively, for the period of 28 days. The mean percentage of males obtained in treatments, 1, 2, 3 and 4 were 98, 97, 95 and 68, respectively. Treatments-1, 2 and 3 did not differ significantly (P>0.05) from each other but treatment 4 showed significant variation (P<0.05) from other treatments. The results showed that MT-100, 80 and 60 mg/kg feed administered for 28 days produced close to cent percent male population of the GIFT strains in aquaria.