金纹细蛾幼虫在陇东苹果树冠层的空间分布研究

为掌握金纹细蛾幼虫在苹果树冠层不同部位的发生规律,为科学防治提供技术支持。以长富2号10年生富士苹果园为研究对象,通过对不同时期金纹细蛾幼虫发生规律、树冠分布特征和集聚性分析,研究了陇东金纹细蛾幼虫在苹果树冠上的空间分布结构。结果发现,金纹细蛾幼虫1 a发生5代。在世代重叠现象和苹果生长期药剂防控的双重影响下,第2代以后各世代之间未出现明显的高峰,在9月上旬之前幼虫数量虽有增长,但增长非常缓慢,而进入9月下旬之后越冬代数量成倍数骤增。从幼虫在树冠上的空间分布看,存在东向和北向＞南向和西向、下部 ＞ 上部、内膛 ＞ 外围的趋势,但是在统计学上却没有显著差异;幼虫在苹果树冠中的分布呈一定的聚集性分布,但聚集度比较小。在前期防控的基础上,加强9月下旬以后的防控,是减少翌年虫源的关键。药剂防控中,在保证树冠全方位防控的同时,树冠下部、内膛、南向和西向为重点防控的空间部位。     

Rearing performance of Clarias batrachus larvae: Effect of age at stocking on growth and survival during fingerling production

An experiment was conducted to evaluate the rearing performance of different larval stages for optimum growth and survival during fingerling production of Clarias batrachus with an aim to reduce the rearing time of the catfish larvae in a hatchery system. The larvae were reared for 5, 10 and 15 days before stocking them in the nursery tanks. No significant (P < 0.05) difference could be found in length increment at the end of first week of rearing. But the total length was reduced during rest three weeks in five days old larvae compared to that of other two higher age groups. In 5 days old larvae the reduced weight (P < 0.05) was observed during the entire rearing period. However, the specific growth rate (SGR) did not vary among the groups. The survival rate as well as total biomass was decreased while stocking five days old larvae for rearing, compared to that of other two age groups.     

草地螟成虫活动与幼虫发育的观察

草地螟地面种群一般在夜间活动。成虫以21:00时至午夜在蜜源植物丰富的植被环境内活动最为频繁,在多种杂草和作物上产卵,卵多产在幼虫寄主植株的中、下部。幼虫3龄前多在卵寄主植物上栖息取食。测定了20℃和30℃恒温条件下饲育的幼虫头部、胸部宽度和身体长度。提出鉴别草地螟幼虫龄期时应按幼虫的头宽再辅以体长或胸宽,田间幼虫发生调查应侧重成虫活动频繁、幼虫喜食植物较多的植被环境。     

狭胸天牛幼虫触角主感器及下颚须和下唇须感受器扫描电镜观察

利用扫描电镜观察了狭胸天牛幼虫触角主感器及其下颚须和下唇须顶端感受器的形态，种 类和分布，并讨论了其结构与功能的关系。结果表明，触角主感器受肾形成唇形，长约９８．０μｍ，宽约２４．５μｍ。下颚须顶端感受器２０个～２５个，下唇须顶端约１５个感受器，根据不同形态，大致分为３种类型；栓锥形，锥柱形和腔锥形。栓锥形和锥柱形感受器分别着生于下颚须和下唇须顶端表面，腔锥形感受器着生于它们的端节侧面。     

Culture of Eriocheir sinensis Larvae in Ponds in Greenhouse

A total of 15 pools were selected from a greenhouse, and they were randomly and evenly divided into three groups. In each group, one stocking density of Eriocheir sinensis was arranged. The results showed that after 45-d culture, the crab number per kilogram reached about 300 with survival rate of about 20%; the initial stocking density had significantly effect on the body size of E. sinensis on sel , instead on the survival rate of E. sinensis larvae. Therefore, it is feasible to conduct the culture of E. sinensis larvae in a pool in greenhouse.     

Influence of food quality and quantity on the growth and development of Crassostrea gigas larvae: a modeling approach

A biochemically based model was developed to simulate the growth, development and metamorphosis of larvae of the Pacific oyster, Crassostrea gigas. The model is unique in that it (1) defines larvae in terms of their protein, neutral lipid, polar lipid, carbohydrate and ash content; (2) tracks weight separately from length to follow larval condition index and (3) includes genetic variation in growth efficiency and egg quality to better simulate cohort population dynamics. The model includes parameterizations for larval filtration, ingestion and respiration that determine growth rate and processes controlling larval mortality and metamorphosis. Changes in tissue composition occur as the larva grows and in response to the biochemical composition of the food.

The simulations show that genetically determined variations in growth efficiency produce significant changes in larval survival and success at metamorphosis. Larvae with low growth efficiency are successful under a much narrower range of culture conditions than larvae with high growth efficiency. The impact of low growth efficiency is primarily controlled by the ability of larvae to store lipid for metamorphosis. Culture conditions that provide increased dietary lipid counterweigh low growth efficiency. Changes in food quantity and quality had little effect on size at metamorphosis. On the other hand, larval life span and success rate at metamorphosis varied over a wide range depending upon the conditions of the simulation. Food quality and food availability both influence larval life span and, hence, larval survival. As ingestion rate decreases, larval life span increases and cohort survival declines. Increased lipid or decreased protein in the diet improves cohort survival. Changes in carbohydrate content are less influential. If cohort success is significantly affected by mortality during larval life rather than success at metamorphosis, the influence of food quality becomes more complex. The range of food compositions yielding high survival is restricted by a balance between improved success at metamorphosis obtained by increased lipid storage and the shortening of larval life span as a result of more rapid growth, a function of protein availability. These simulations illustrate the strength and utility of numerical models for evaluating and designing hatchery protocols for optimizing yield of C. gigas larvae.     

Development of wolffish eggs at different temperature regimes

Embryonic development of common wolffish (Anarhichas lupus L.) was studied at constant temperatures 5.0, 7.0, 9.0, 11.0, 13.0 and 15.0°C. Duration of development from egg activation to several morphological stages including 50% hatching was determined. At 5.0–11.0°C, the survival rate of eggs to hatching ranged from 51 to 88% with a tendency to increase at 5.0 and 7.0°C. Morphological anomalies, bacterial contamination and large mortalities were observed in eggs incubated at 13.0 and 15.0°C. The period of hatching lasted from 10 to 50 d in different egg groups. Embryo length and yolk sac volume at identical morphological stages of development showed only slight relation to temperature. At lower temperatures newly hatched larvae were longer and at more advanced stages of ontogeny. Normal numbers of fin rays in larvae (mean values 74 for dorsal fin and 46 for anal fin) were observed at 5.0 and 7.0°C and in most larvae at 9.0°C. At 11.0 and 13.0°C, many rays were absent, with mean values for dorsal fin 60 and 39 respectively and for anal fin 28 and 4 respectively. The approximate upper limit for normal development of fin rays appeared to be 9.0 °C.     

Spawning, early development and first feeding in the gobiid fish Priolepis nocturna

The reproductive behavior, embryonic development and early larvae of Priolepis nocturna are described. Three pairs of P. nocturna began spawning 41 days after acquisition and maintained a 5–10 day spawning cycle lasting beyond several months. Spawning was initiated by the female who signaled her readiness to spawn by displaying to the male. Egg clutch size averaged 1578 ± 51.23 eggs and ranged from 268 to 3121. Egg length averaged 0.82 ± 0.01 mm total length (TL) and ranged from 0.75 to 0.90 mm. Egg width averaged 0.51 ± 0.51 mm total width (TW) and ranged from 0.49 to 0.52 mm. Fertilized eggs were ovoid in shape and attached to the ceiling of provided shelters via adhesive filaments at the proximal end. Hatching rates averaged 97.3 ± 0.51% and ranged from 91.9 to 99.8%. Larvae measuring 1.89 ± 0.04 mm TL hatched 121 ± 0.5 h post fertilization and did not rotate position prior to hatching. Skeletal elements of the chondrocranium were simplistic and dominated by the hyoid, hyomandibulosymplectic cartilage, ethmoid and Meckel's cartilage in first feeding larvae. No elements were added to the cranial architecture by 5 days post hatch (DPH) when larvae measured 2.05 ± 0.04 mm TL. First feeding larvae consumed only dinoflagellates and tintinnids suggesting that feeding was constrained by a poorly developed feeding mechanism. Embryology and larval development are described to 5 DPH.     

The effect ofDendrolimus superans breakout on growth of trees

The effect ofDendrolimus superans on growth of trees was investigated after the breakout in Shibazhan forest area in 1990. Stem analysis was conducted for determining the tree increment loss. The result showed that the current annual increment for extreme heavily damaged, heavily damaged, moderately damaged and lightly damaged stands is 14%, 39.8%, 64% and 82% of that of the control forest respectively. (Responsible Editor: Chai Ruihai)     

A system for model-based biomass estimation of larvae in intensive cod larvicultures

High and unpredictable mortality rates are observed in the larval rearing of cod (Gadus morhua). As a means of addressing this problem, we present a model-based estimator system which can be used to indirectly measure the larval density through monitoring the live food dynamics and larval growth. The estimator has been evaluated in a conceptual context using a preliminary model formulation, and the observability of the process has been investigated. It was found that the two parameters, live food dynamics and larval growth, contain enough information for the larval density to be estimated under noisy conditions, given the correct model. When the system is applied practically, the estimation error will depend on the measurement and model accuracy; this is especially true with respect to the predictability of the feed intake rate of the fish.