Effects of ocean acidifi cation driven by elevated CO_2 on larval shell growth and abnormal rates of the venerid clam, Mactra veneriformis

A bstract The venerid clam(M actra veneriformis Reeve 1854) is one of the main cultured bivalve species in intertidal and shallow subtidal ecosystems along the west coast of Korea. To understand the effects of ocean acidifi cation on the early life stages of Korean clams, we investigated shell growth and abnormality rates and types in the D-shaped, umbonate veliger, and pediveliger stages of the venerid clam M. veneriformis during exposure to elevated seawater pCO_2. In particular, we examined abnormal types of larval shell morphology categorized as shell deformations, shell distortions, and shell fi ssures. Specimens were incubated in seawater equilibrated with bubbled CO_2-enriched air at(400±25)×10^(-6)(ambient control),(800±25)×10^(-6)(high pCO_2), or(1 200±28)×10^(-6)(extremely high pCO_2), the atmospheric CO_2 concentrations predicted for the years 2014, 2084, and 2154(70-year intervals; two human generations), respectively, in the Representative Concentration Pathway(RCP) 8.5 scenario. The mean shell lengths of larvae were signifi cantly decreased in the high and extremely high pCO_2 groups compared with the ambient control groups. Furthermore, under high and extremely high pCO_2 conditions, the cultures exhibited signifi cantly increased abundances of abnormal larvae and increased severity of abnormalities compared with the ambient control. In the umbonate veliger stage of the experimental larvae, the most common abnormalities were shell deformations, distortions, and fi ssures; on the other hand, convex hinges and mantle protuberances were absent. These results suggest that elevated CO_2 exerts an additional burden on the health of M. veneriformis larvae by impairing early development.

Key Techniques and Applications of Adaptive Growth Method for Stiffener Layout Design of Plates and Shells

The application of the adaptive growth method is limited because several key techniques during the design process need manual intervention of designers. Key techniques of the method including the ground structure construction and seed selection are studied, so as to make it possible to improve the effectiveness and applicability of the adaptive growth method in stiffener layout design optimization of plates and shells. Three schemes of ground structures, which are comprised by different shell elements and beam elements, are proposed. It is found that the main stiffener layouts resulted from different ground structures are almost the same, but the ground structure comprised by 8-nodes shell elements and both 3-nodes and 2-nodes beam elements can result in clearest stiffener layout, and has good adaptability and low computational cost. An automatic seed selection approach is proposed, which is based on such selection rules that the seeds should be positioned on where the structural strain energy is great for the minimum compliance problem, and satisfy the dispersancy requirement. The adaptive growth method with the suggested key techniques is integrated into an ANSYS-based program, which provides a design tool for the stiffener layout design optimization of plates and shells. Typical design examples, including plate and shell structures to achieve minimum compliance and maximum bulking stability are illustrated. In addition, as a practical mechanical structural design example, the stiffener layout of an inlet structure for a large-scale electrostatic precipitator is also demonstrated. The design results show that the adaptive growth method integrated with the suggested key techniques can effectively and flexibly deal with stiffener layout design problem for plates and shells with complex geometrical shape and loading conditions to achieve various design objectives, thus it provides a new solution method for engineering structural topology design optimization.

Comparison of growth and survival of larvae among different shell color stocks of bay scallop Argopecten irradians irradians(Lamarck 1819)

In order to improve production and breed new broods of bay scallop Argopecten irradians irradians, different-colored orange, purple and white lines were established by two mating methods of self-fertilization and mass spawning at a commercial scallop hatchery in spring, 2002. And then larval growth and survival of different lines was compared to test whether there is a relationship between shell color and growth and survival at early developmental stage. Both growth and survival have no significant differences among different experimental larvae of self-fertilization or mass spawning. Results are as following in the order of orange, purple and white shell stock. For the self-fertilization, growth rates of larvae were 6.174, 6.412, and 6.599 μm/d, respectively. Survival rates of larvae at Day 3 were 74.41%, 76.86%, and 82.05%; Day 6 were 49.14%, 65.63%, and 52.79%; and Day 9 were 25.06%, 20.80%, and 26.47%, respectively. For the mass spawning, the growth rates were 7.836, 7.941, and 7.878 μm/d, respectively. Survival rates at Day 3 were 93.05%, 91.95%, and 92.50%; Day 6 were 79.17%, 78.05%, and 82.50%; and Day 9 were 34.72%, 36.67%, and 38.33%, respectively. The absence of any relationship between shell color and growth and survival at the larval stage may be resulted from their common genetic basis.

Influence of <i>Ocimum gratissium</i>Leaves Supplement on Growth Indices and Blood Constituents of Goats Fed Sweet Potato Peels with Cashew Nut Shell

The study was carried out to determine the influence of sweet potato peels and cashew nut shell supplemented with Ocimum gratissium leaves, using growth indices and blood constituents by goats. Eighteen goats with an average weight of 8.11 kg and aged between 8 and 9 months old were allotted to three dietary treatments with six animals per treatment in a complete randomized design. The compared diets which comprised combination of sweet potato peels and cashew nut shell with concentrate respectively were in different ratios which included diet I (30:25:45), diet II (25:30:45) and diet III (20:35:45). Each goat also received 8 grams of Ocimum gratissium leaves as supplement in the diet. The results showed that average feed intake (6.42 kg) and fed conversion ratio (2.15) were highest in diet I and significantly different from other diets. Diet II had the highest significant (P 3/L), lymphocytes (56.01%), monocytes (1.06%), total protein (7.65 g/dl), albumin (3.58 g/dl), globulin (4.07 g/dl) and triglyceride (2.29 mmol/L). White blood cell (7.01 × 103/L), neutrophils (49.82%), cholesterol (42.34 mmol/L), creatnine (1.59 mg/dl) and urea (18.29 mg/dl) were (P < 0.05) best in diet III, whereas initial bodyweight, average daily weight gain, eosinophils and basophils were not significantly different (P < 0.05). It is concluded that diet II has the potential to enhance growth rate and blood constituents of goats.

Comparative Effects of Organic Cocoa Shell-Based and Inorganic NPK Fertilization on the Growth and Yield of Four Cassava Varieties

Looking of finding an alternative to the use of chemical fertilizers to increase yields of cassava (Manihot esculenta), trials were carried out in the Lamto zone in central Côte d’Ivoire. Thus, the effects of compost and ash from cocoa shell and NPK were tested on the agronomic parameters of cassava. The trial was conducted for two years with four varieties of cassava: Yacé, Alleda agba, Six mois and Bonoua, grown on elementary plots treated with one of these fertilizers. The experimental design was complete randomized blocks with three replicates. Analysis of the results showed that the Six mois variety gave the longest stems (131, 67 cm) with the cocoa shell compost. The Bonoua variety, on the other hand, gave the largest diameter of the stem base (21.56 mm), a higher number of leaves (77.30) and a large wingspan (136.89 cm) with cocoa shell compost. The leaves developed by the plants of this variety were wider (19.30 cm) and longer (17.96 cm) with cocoa shell compost. Also, this Bonoua variety treated with shell compost yielded a high number of tuberized roots (5.11), high average weight per plant (5.83 kg/plant) and higher yield (58.29 t/ha). This compost of cocoa shell has also allowed a better conservation of the cultivated soils quality.

Effects of Dietary Soy Protein Concentrate on Growth, Digestive Enzymes Activities and Target of Rapamycin Signaling Pathway Regulation in Juvenile Soft-Shelled Turtle, <i>Pelodiscus sinensis</i>

Soft-shelled turtle, Pelodiscus sinensis is important aquatic species in China, and searching for alternatives protein resources to fish meal (FM)-based feeds in feed has become urgent and important for its sustainability development. The present study was conducted to assess the effects of dietary soy protein concentrate (SPC) on growth, digestive enzymes and target of rapamycin (TOR) signaling pathway of juvenile P. sinensis (4.56 ± 0.09 g). SPC was applied to replace FM protein at 0%, 15%, 30% and 60% (designated as T0, T15, T30 and T60, respectively), and each diet was fed to triplicate groups. The results showed that there was no significant difference in growth performance and feed utilization except of the turtles fed with T60 diet, of which showed poorer daily weight gain and feed conversion rate. The pepsin/trypsin and Na+-K+ ATP-ase activities decreased dramatically when SPC level increased, and lipase activities in liver and intestinal tract also showed decline tendency. However, amylase activities were unaffected. No significant differences were observed in TOR, S6K1 and 4E-BP1 genes mRNA expression level of TOR signaling pathway among the treatments. However, the relative phosphorylated level of these proteins decreased significantly when SPC level increased. The present study indicated that high SPC substitution level would suppress digestive enzymes and TOR signaling pathway proteins phosphorylated level and eventually result in growth reduction of P. sinensis.

长牡蛎壳橙性状遗传参数评估及与生长性状的关联性

长牡蛎壳橙快速生长品系是结合群体选育与种内群体间杂交方法,以壳色性状和生长性状为选育指标,经过连续3代选育获得的新品系。本研究以第1代长牡蛎壳橙快速生长品系(G1)为亲本,采用巢式设计建立了48个混养家系,共获得863个个体。利用微卫星标记对混养家系进行了系谱分析,并基于REML法评估了长牡蛎壳橙快速生长品系壳色性状的遗传参数及与生长性状的相关性。结果显示,863个个体中,有851个个体被准确鉴定其所属家系;长牡蛎壳橙快速生长品系壳色性状颜色参数指标a*(红绿轴色品指数)、b*(黄蓝轴色品指数)和ΔE(色差)等均具中高等遗传力,大小依次为0.47±0.23、0.42±0.21和0.56±0.29。4个颜色参数指标间的遗传相关和表型相关范围分别为−0.79~0.86和−0.45~0.48。壳色性状与各生长性状的遗传相关和表型相关较低,分别为−0.33~0.17和−0.04~0.11。研究表明,在长牡蛎壳橙快速生长品系育种过程中,对壳色性状进行选育可以得到预期的改良效果。此外,壳橙性状与生长性状应分别作为目标性状进行协同选择,以实现同时改良两个性状的目的。本研究可为长牡蛎壳橙快速生长品系选育提供基础资料。

Analytical study of seashell using laser-induced breakdown spectroscopy

Seashell has been applied as an indicator for ocean research and element analysis of the seashell is used to track biological or environmental evolution. In this work, laser-induced breakdown spectroscopy （LIBS） was applied for elementary analysis of an ezo scallop-shell, and a graphite enrichment method was used as the assistance. It was found that LIBS signal intensity of Ca fluctuated less than 5%, in spite of the sampling positions, and Sr/Ca was related to the shell growth. A similar variation was also found when using a direct LIBS analysis on the shell surface, and it might be more practicable to track shell growth by investigating Sr/Ca ratio with Sr ionic line at 421.6 nm. The obtained results prove that calcium （Ca） is qualified as an internal reference for shell analysis, and LIBS is a potential analytical method for seashell study.

坝上长尾鸡和绿壳蛋鸡早期生长发育与开产性能分析

为了研究坝上长尾鸡与绿壳蛋鸡早期体质量、胫长与开产性能之间的关系,建立基于体质量、胫长指标与开产性能的最优回归方程。随机选取1日龄坝上长尾鸡和绿壳蛋鸡各200只,测定5周龄体质量(X_(1))、6周龄体质量(X_(2))、7周龄体质量(X_(3))、5周龄胫长(X_(4))、6周龄胫长(X_(5))、7周龄胫长(X_(6))、开产日龄(Y_(1))、开产蛋重(Y_(2))、开产体质量(Y_(3)),并进行相关与回归分析。结果表明:绿壳蛋鸡开产日龄极显著早于坝上长尾鸡(p<0.01),坝上长尾鸡开产体质量、开产蛋重极显著高于绿壳蛋鸡(p<0.01);坝上长尾鸡与绿壳蛋鸡5~7周龄体质量、胫长与开产蛋重、开产体质量均呈极显著正相关(p<0.01),与开产日龄呈不显著负相关(p>0.05)并得出坝上长尾鸡和绿壳蛋鸡最优回归方程。说明可以通过坝上长尾鸡和绿壳蛋鸡生长性状指标预测评估开产性能。

虾壳源多肽酶解条件的优化及其抗冻活性和作用机制的探究

目的优化从虾壳中提取多肽的酶解条件,并探究虾壳多肽的抗冻活性及作用机制。方法以小龙虾虾壳为原料,使用复合酶酶解提取多肽。在单因素实验的基础上,通过正交实验得到虾壳最佳酶解条件。以面包酵母菌为抗冻测试对象测试其抗冻能力。采用液相色谱-串联质谱法(liquid chromatography-mass spectrometry,LC-MS/MS)对虾壳多肽的组成进行鉴定,基于多肽的理化性质和序列,结合抗冻预测平台筛选抗冻肽(antifreeze peptides,AFPs)。使用分子动力学模拟探究了AFPs的作用机制。结果在酶解温度40℃,底物质量浓度20mg/mL,加酶量12000U,酶比0.33的最佳酶解条件下,多肽提取率达到了70%以上。虾壳多肽中含有1004种肽段,能明显提升酵母菌存活率。从具有抗冻活性且置信度靠前的20条多肽中进一步筛选出了潜在的抗冻肽AFP1、AFP2。AFP2和冰面之间形成的氢键数量为14,部分水分子同时与2个氨基酸残基形成氢键,充当水桥稳定多肽的构象,AFP2与冰之间的结合能为-105.08 kcal/mol,冰结合模拟效果理想。结论AFPs与冰结合并抑制冰晶生长可能归因于带电荷的亲水性氨基酸残基与水分子形成的氢键、范德华力等分子间作用力,可开发为有益的冷冻保护剂,用于冷冻食品加工,具备良好的应用前景。

“葵花壳+玉米秸秆”加工粉尘对合作猪生长性能、血清生化和免疫指标、抗氧化能力及经济效益的影响

为探究日粮中添加“葵花壳+玉米秸秆”加工粉尘对合作猪生长性能、血清生化和免疫指标、抗氧化能力及经济效益的影响,试验选择50头健康状况良好、体重相近的90日龄合作猪,进行7 d预饲,饲喂基础日粮,结束后选择体重相近的40头合作猪,随机分为4组,对照组饲喂基础日粮,试验Ⅰ、Ⅱ、Ⅲ组分别在基础日粮中添加5%、10%和15%的“30%葵花壳+70%玉米秸秆”加工粉尘,正试期90 d,测定合作猪生长性能和血清生化指标、免疫指标、抗氧化能力,并测算经济效益。结果显示:(1)与对照组相比,试验Ⅰ、Ⅱ组平均日采食量分别增加6.77%、3.39%(P>0.05),试验Ⅲ组降低5.08%(P>0.05),试验Ⅰ、Ⅱ组的平均日增重分别增加10.00%(P<0.05)、6.66%(P>0.05)。(2)与对照组相比,试验Ⅱ组的白蛋白增加20.02%(P<0.05),试验Ⅲ组的总胆固醇降低14.33%(P<0.05),试验Ⅰ、Ⅱ、Ⅲ组的三酰甘油和尿素含量极显著降低(P<0.01)。(3)与对照组相比,试验Ⅰ、Ⅱ、Ⅲ组的免疫球蛋白M极显著降低34.29%、24.00%和20.57%(P<0.01),肿瘤坏死因子-α分别增加6.98%(P>0.05)、18.58%和19.67%(P<0.05)。(4)与对照组相比,试验Ⅲ组的超氧化物歧化酶活性显著降低19.67%(P<0.05),试验Ⅱ组的丙二醛含量极显著降低44.90%(P<0.01)。(5)与对照组相比,试验Ⅰ、Ⅱ、Ⅲ组经济效益均有提高,试验Ⅰ组最高,为62.59元/头。综上所述,饲粮中添加10%的“葵花壳+玉米秸秆”加工粉尘更利于机体脂质代谢,添加5%加强了机体代谢,显著提高了日增重,增加了经济效益。因此,推荐在饲粮中添加5%的“葵花壳+玉米秸秆”加工粉尘。

油茶壳堆肥用量对土壤肥力及苦麦菜生长与品质的影响

【目的】探明腐熟油菜壳有机肥不同施用量对土壤理化性质及苦麦菜生长与品质的影响,为油茶壳资源化利用及有机肥的合理施用提供依据。【方法】以苦麦菜为试验材料,设置不同油茶壳有机肥用量水平,采用田间小区试验(CK1:不施底肥;T1:常规施肥,复合肥450 kg/hm^(2);T2:油茶壳有机肥7500 kg/hm^(2);T3:油茶壳有机肥15000 kg/hm^(2);T4:油茶壳有机肥22500 kg/hm^(2);T5:复合肥360 kg/hm^(2)+油茶壳有机肥15000 kg/hm^(2))和盆栽试验(CK2:不施肥;P1:常规施肥,复合肥225 kg/hm^(2);P2:油茶壳有机肥3750 kg/hm^(2);P3:油茶壳有机肥7500 kg/hm^(2);P4:油茶壳有机肥11250 kg/hm^(2);P5:复合肥180 kg/hm^(2)+油茶壳有机肥7500 kg/hm^(2)),共12个处理,研究腐熟油茶壳有机肥不同施用量对土壤理化性质及苦麦菜生长与品质的影响。【结果】田间和盆栽试验下,施用油茶壳有机肥总体上能提升土壤养分。各处理土壤pH为5.92~6.89,施用油茶壳有机肥和复合肥减量配施处理的土壤有机质、有效磷、速效钾含量较未施肥处理总体增加,水解性氮含量与常规施肥处理间无显著差异,其中,田间试验有机质、有效磷和速效钾含量分别为33.13~43.94 g/kg、43.39~162.61 mg/kg和247.00~667.69 mg/kg,盆栽试验分别为12.44~38.32 g/kg、1.17~344.79 mg/kg和41.79~1889.03 mg/kg。田间试验施用油茶壳有机肥22500 kg/hm^(2)和盆栽试验施用油茶壳有机肥7500 kg/hm^(2)时,苦麦菜株高和地上部鲜重分别为43.42 cm、116.25 g和40.25 cm、73.76 g,显著高于未施肥和常规施肥处理。田间试验苦麦菜可溶性糖、维生素C、叶绿素和蛋白质含量分别为0.34~0.67 g/100g、13.52~19.23 mg/100g、1.06~1.52 mg/g和0.91~1.29 g/100g,盆栽试验分别为0.65~1.64 g/100g、13.75~29.44 mg/100g、0.99~1.36 mg/g和1.25~2.51 g/100g。施用适量油茶壳有机肥或复合肥减量配施的苦麦菜可溶性糖、维生素C和叶片叶绿素含量高于常规施肥处理,未施肥处理苦麦菜的蛋白质含量显著高于其余处理。【结论】综合苦麦菜的生长和品质性状,油茶壳有机肥以田间施肥量22500 kg/hm^(2)和盆施肥量7500 kg/hm^(2)为宜。

核桃壳木醋液植物生长促进剂响应面法配方优化

为优化以核桃壳木醋液为主的植物生长促进剂配方,在单因素试验的基础上,以核桃的叶面积为响应值,采用响应面法检测不同混合物比例对核桃的促生效果。结果表明,在木醋液体积分数0.5%(200倍液)、KH 2 PO 4质量浓度0.2%、过磷酸钙质量浓度1%、硼酸质量浓度0.2%、尿素质量浓度0.3%时,1年生核桃叶面积最大,达到82.77 cm^(2),与预测值(85.23 cm^(2))无显著差异,表明促生条件最佳。在回归方程中核桃壳木醋液对叶面积的影响最显著,可用于进一步制备核桃壳木醋液生长促进剂。

南瓜籽壳对不同生长阶段西杂肉牛生长性能、血清生化和免疫指标及激素水平的影响

[目的]研究日粮中添加南瓜籽壳对不同生长阶段西杂肉牛生长性能、血清生化和免疫指标及激素水平的影响。[方法]选取体况良好的西门塔尔杂交公牛共40头,按照体重分为5组,分别为试验1组(300 kg左右)、试验2组(400 kg左右)、试验3组(500 kg左右)、试验4组(600 kg左右)和试验5组(700 kg左右),每组8头,分栏饲养,基础日粮中均添加10%的南瓜籽壳。试验期为90 d,预试期20 d,正试期70 d。记录各组肉牛试验期间体重及采食情况,计算平均日增重、平均日采食量和平均料重比;试验结束时采集血液样本制备血清,测定血清生化指标、免疫指标及激素水平。[结果]随着肉牛体重的增加,日采食量逐渐增加,试验4组和5组平均日采食量显著(P<0.05)高于其他组;试验1组平均料重比最低,显著(P<0.05)低于其他组。试验4组血清总蛋白(TP)、尿素氮(BUN)含量显著(P<0.05)高于试验1组、3组。试验2组血清免疫球蛋白M(IgM)含量显著(P<0.05)高于其他组。试验1组血清皮质醇(COR)水平显著(P<0.05)高于试验3组、4组、5组,试验5组血清降钙素(CT)水平显著(P<0.05)高于其他各组,试验4组、5组C反应蛋白水平显著(P<0.05)高于试验1组。[结论]西杂肉牛日粮中添加南瓜籽壳,可增加采食量,提高机体蛋白质利用率,对增强动物免疫力具有一定作用,可作为一种粗饲料资源进行开发利用。

Effect of <i>Carya cathayensis Sarg</i>Shell Substrate on Yield and Nutrient Amount of <i>Pleurotus geesteranus</i>

Using cottonseed hull as the control substrate, different proportions of the untreated and treated Carya cathayensis Sarg shells were added to cultivation of Pleurotus geesteranus. The mycelial growth rate, yield, nutritional composition and contents of heavy metals of the Pleurotus geesteranus cultivated on these substrates were determined. The results suggest that added to treated Carya cathayensis Sarg shell promoted the mycelial growth and increased the yield, biological efficiency and the contents of crude fiber, ash, amino acids and essential amino acids of Pleurotus geesteranus. In addition, the fat content and soluble sugar contents of Pleurotus geesteranus were decreased with the increase of the Carya cathayensis Sarg shell content in substrate, but their contents of heavy metals including mercury (Hg), arsenic (As), cadmium (Cd) and lead (Pb) were higher than that obtained on control substrate.

神丹6号绿壳蛋鸡生长曲线拟合及分析

研究用Logistic、Gompertz和Von Bertalanffy 3个模型对0~60周龄的神丹6号绿壳蛋鸡生长曲线进行拟合,探索其从出雏至产蛋后期的生长发育规律。结果显示:三种模型对应的模型拟合度(R2)分别为0.991、0.996和0.996,Von Bertalanffy模型拟合的生长曲线与实际情况更为接近,对应的拐点体重、拐点周龄和最大周增重分别为449.50 g、7.30周和80.91 g。研究表明,Von Bertalanffy模型可较好拟合神丹6号绿壳蛋鸡的生长曲线。

Fatigue reliability analysis of kiln welded shell

这份报纸在裂缝生长期间为焊接的壳论述一个概率的可靠性方法。与一张失败评价图(一度时髦的风尚) 合并的裂缝生长模型，罐头提供批评裂缝长度的一个更好的评价，被开发描述疲劳失败。为壳的特别焊接关节的所有变量被学习。在他们之中，压力变量由使用有限元素(FE ) 基于计算压力代码 ANSYS。焊接的壳的疲劳可靠性分析被使用蒙特卡罗模拟方法执行。例子火炉的失败概率曲线是显著地有用的决定壳裂缝的修理时间表。

Growth performance of the clam, Meretrix meretrix, breeding-selection populations cultured in different conditions

A breeding-selection program for the clam, Meretrix meretrix, was conducted since 2004. Two of the selec- tion populations were generated with the shell color pattern as an additional selection criterion and named as SP （purple stripes） population and SB （black dots） population. The third-generation SP and SB popula- tions （08G3SP and 08G3SB, respectively） were cultured at two commercial clam farms and a nursery pond and their shell lengths were compared. 08G3SB clams had significantly larger sizes than 08G3SP clams at commercial clam farms （p 〈 0.05）, yet 08G3SB individuals were significantly smaller than 08G3SP individ- uals at the nursery pond （p 〈 0.05）. Then, we examined the growth of the fourth-generation SP and SB populations （10G4SP and 10G4SB, respectively） at a commercial farm, and found that the shell lengths of the 10G4SB clams increased at a significantly higher growth rate than the 10G4SP clams （p 〈 0.05） from May to September, when the water temperature was between 24.2-27.5℃, while 10G4SB lost the growth advantage in the other months. These results indicated that SP and SB populations responded differently to environmental factors, so it is beneficial for the clam farmers to select a suitable population according to the culture environment. Furthermore, a diallel mating of the SB and SP populations was designed to investigate whether their hybrid population would show heterosis. However, the heterosis was not shown in this study, which might result from the slight genetic divergence between SB and SP populations.

Effect of Calcium Source in Supplemental Diets on the Growth Performance and Carcass Characteristics of the Giant African Land Snails (Archachatina marginata) in the Western Highlands of Cameroon

To contribute to the diversification of protein sources, the conservation and preservation of the Giant African Land Snails (Archachatina marginata), a study was carried out between March and July 2019 at the Helvy Farms-WVED Cameroon located at Station Bamenda to investigate the effect of three calcium sources on their growth performance and carcass characteristics. 180 juvenile snails aged 4 months initially weighing between 24.2 and 28.5 g, shell length ranging between 40.25 - 48.35 mm, and shell diameter of between 14.08 - 18.44 mm were randomly allotted to 3 treatments containing each a different calcium source (crushed snail shell, eggshell and agricultural limestone) and a control treatment constituted of natural plant feeding materials of the snail. There were 45 snails per treatment, constituted of three replicates with 15 snails per replicate. Each replicate was housed in well-constructed surface trench pens equipped with drinking and feeding troughs. The basal diet made up of feedstuffs like pawpaw leaves and watermelons was provided ad libitum. The initial weights of the snails were recorded at the start of the experiment followed by weekly weight measurements, while the snail length and width were measured with a digital caliper of 0.05 mm accuracy. The snails were monitored for a period of 21 weeks and data was collected for 20 weeks after a 1 week adaptation period. The results showed that the weight gain (g) of snails for diets containing calcium sources in the supplemental diets were all significantly higher (P < 0.05) than the corresponding values recorded for the control diet with natural plant material. It was observed that the shell length (0.34 ± 0.02), shell width (0.16 ± 0.02), weight gain (13.13 ± 0.03) and feed conversion efficiency (1.977 ± 0.11) were highest in snails fed snail shell diet as calcium source compared with snails from other treatments. These values were however not significantly higher than corresponding values for the other two supplemental diets containing eggshell or agricultural limestone. It can be deduced that the snail shell is an important calcium source for growing snails and can be adopted and used in the diets of snails. This will amount to some good methods of recycling in snail production.

Preparation of Core-shell Structured Particles and Their Nucleation in Polyester:I. Preparation of Monodisperse SiO_2/PS Core-shell Composite Particles

To enhance the nucleation and crystallization properties of polyester (e.g., polyethylene terephthalate, PET), core-shell structured particles are used to improve these properties by controlling the inorganic dispersion properties in the polymers. In the paper, monodisperse particles of silica/polystyrene (PS) are prepared with both dispersion and emulsion polymerization techniques. The monodisperse silicon dioxide particles are first prepared with the seed growth method and modified by the coupling agents. Silica is properly modified with KH-570, and its size deviation is 3.0% or so. The modified silica then reacts with the mixture of ethanol, water medium, and monomer of styrene under dispersion polymerization. Results show that the dispersion polymerization technique is more suitable for monodisperse core-shell SiO2/PS particles than that of the emulsion. The morphology and molecular structure of the core-shell particles are investigated with the transmission electron microscope (TEM), and fourier transform infra-red spectroscopy (FTIR). The results show that the modified silica particles are successfully encapsulated with polystyrene. The average number of silica particles encapsulated into each polystyrene sphere decreases when the size of silica particles increases from 50 nm to 600 nm, and will approach one when the silica is greater than 380nm in size. The mass ratio for silica/PS particles in emulsion polymerization is 4.7/1, lower than that of 6.8/1 for dispersion polymerization, which is the first reported optimized data for preparing the similar monodisperse composite particles. Thus, the PS shell in the former is thinner than that in the latter.