厚壳贻贝人工繁殖技术的研究

厚壳贻贝(Mytilus coruscus)是我国贻贝的主要养殖品种,其苗种主要依靠天然苗种和半人工采苗获得。2006年浙江海洋学院于嵊泗县石柱育苗厂,首次突破了厚壳贻贝规模化全人工繁殖和稚贝海区中间培育技术。研究结果表明,厚壳贻贝亲贝通过室内强化培养,经人工催产可获得成熟受精卵,受精率可达95%。在水温16℃时,受精卵在受精后25min出现第一极体,受精后39h50min发育至直线绞合幼虫期,胚胎孵化率达92%,在水温15.8～21℃的条件下,经39d室内人工培育,获平均壳长0.694mm的附着稚贝1304.7×104ind;附着稚贝经102d海区中间培育,获平均壳长13.95mm的稚贝404.46×104ind,海区保苗成活率达31%。该研究结果为今后厚壳贻贝大规模苗种生产奠定了重要理论和技术基础。     

葡萄牙牡蛎工厂化人工育苗技术

葡萄牙牡蛎工厂化人工育苗技术包括亲贝促熟、饵料培养、幼虫和稚贝培育等过程。葡萄牙牡蛎受精卵卵径约60μm,在水温25.3℃、盐度26.5及p H8.2条件下受精卵经过16h左右发育为D形幼虫;幼虫经14~21 d培育进入变态附着期,幼虫培育过程投喂饵料为金藻、小球藻、角毛藻和骨条藻,稚贝加投扁藻;采用聚丙烯塑料片作为幼虫变态附着的附苗器。同时筛选出葡萄牙牡蛎受精卵孵化及幼虫生长的适宜环境条件,并进行了不同饵料投喂效果及不同附苗器的附苗效果试验。     

长肋日月贝个体发生观察及人工育苗初步试验

首次报道了长肋日月贝( Amusium pleuronectes )的诱导产卵及幼虫、稚贝培育.用阴干-流水刺激法,成功诱导亲贝产卵、排精.对胚胎和幼虫发生进行了观察.水温23.0～25.0℃,经诱导产卵的受精卵20 h可发育至D形幼虫.水温22.0～24.0℃时,D形幼虫经11 d培育到眼点幼虫期.投放附着基后,眼点幼虫在10 d内附着完毕.水温18.0～24.0℃时,稚贝经30 d培育平均壳长达(2.0±0.18)mm.此试验共培育壳长(2.93±1.15)mm稚贝49.6万粒.     

墨西哥湾扇贝选育系早期发育与生长

在水温28~29℃、盐度24~25条件下,研究墨西哥湾扇贝(Argopecten irradians concentricus)选育系的早期发育及幼虫和稚贝的生长。受精卵经50 min发育至卵裂,经22~24 h发育至D形幼虫,经11 d发育至眼点幼虫并出现足,进入附着变态阶段。选育系的胚胎发育时间和浮游幼虫前期壳长、壳高与对照系比较差异不显著(P0.05);浮游幼虫后期及至附着变态阶段,选育系与对照系的壳长和壳高差异显著(P0.05)。选育系的附着变态率和存活率与对照系比较均差异显著(P0.05),且优势明显。本研究表明,墨西哥湾扇贝浮游幼虫发育前期缓慢,幼虫后期、稚贝期生长迅速;壳长和壳高的生长速度不同步,幼虫前期壳长生长快于壳高,后期壳高生长快于壳长,并于第28~30天时壳高超过壳长。墨西哥湾扇贝选育系在幼虫和稚贝阶段生长速度明显快于对照系,具有明显的生长优势及生长潜力。     

脉红螺附着变态与食性转换的研究

为实现脉红螺苗种的规模化生产,本实验通过对脉红螺幼虫培育、采苗、稚螺培育等方面的系统研究,探索了脉红螺苗种繁育过程中幼虫附着变态率低和饵料转换难的问题。结果显示:脉红螺浮游幼虫前期(0~12 d)生长较快,壳高平均日增长21.8μm;中期(13~18 d)生长较慢,壳高平均日增长3μm;后期(19~30 d)生长加快,壳高平均日增长46.8μm。用取自沉淀池中的新鲜海水对脉红螺浮游幼虫进行附着变态诱导,诱导第1天脉红螺浮游幼虫开始出现附着变态,第4天时,附着变态活动基本结束,附着变态率为40%。为变态后的稚螺投喂刚附着的长牡蛎和魁蚶稚贝,第1~8天,稚螺壳高平均日增长65.6μm;第9天开始,稚螺生长速度加快;第9~12天,稚螺壳高平均日增长136.4μm;第13~16天,稚螺壳高平均日增长307.3μm;第17~20天,稚螺壳高平均日增长445.8μm。研究表明,用取自沉淀池中的新鲜海水诱导脉红螺浮游幼虫的附着变态效果好,刚附着的长牡蛎稚贝和魁蚶稚贝可以作为脉红螺稚螺培育阶段的适宜饵料。     

底物大小对牡蛎幼虫附着的诱导效应

为探讨底物大小对牡蛎幼虫附着的诱导效应,设计底物大小和实验环境(室内和野外)的双因子随机区组实验,检验3种规格实验底物(A:5 cm长×5 cm宽×3 cm厚、B:10 cm长×10 cm宽×3 cm厚、C:15 cm长×15 cm宽×3 cm厚,以下简称A、B、C)、实验环境以及他们之间的互作对牡蛎幼虫(室内实验:长牡蛎Crassostrea gigas;野外实验:熊本牡蛎C.sikamea)附着效果(密度和壳高)的影响。附着实验结果显示,室内实验A组附着稚贝的平均密度和平均壳高分别为1.06个·cm~(-2)和14.10 mm,B组为5.60个·cm~(-2)和8.69 mm,C组为12.01个·cm~(-2)和4.44 mm;野外实验A组附着稚贝的平均密度和壳高分别为2.41个·cm~(-2)和17.83 mm,B组为4.65个·cm~(-2)和11.61 mm,C组为6.90个·cm~(-2)和7.43 mm。单因子方差分析结果表明,室内和野外实验中底物大小均显著影响附着稚贝的密度(P<0.001),即底物越大,稚贝附着密度越高,但壳高则相反,稚贝壳高和密度之间呈显著负相关;室内和野外的实验环境对附着稚贝密度影响不显著(P>0.05),对壳高影响显著(P<0.05)。双因子方差分析结果表明,实验环境和底物大小的交互作用对附着稚贝密度影响显著(P<0.05),对壳高影响不显著(P>0.05)。研究结果表明,在牡蛎礁生态修复中,选择适合的底物大小能显著提高牡蛎附着效果。     

青蛤的育苗技术

青蛤[Cyclinasinesis（Gmelin）]，俗称黑蛤、羊蹄蛤等，是生活于潮间带的理栖型双壳贝类，为黄渤海常见种。其肉味鲜美，营养丰富，生长快，经济价值较高，是颇具发展前途的养殖贝类。为促进青蛤养殖业的发展，笔者将青蛤的育苗技术介绍如下。1半人工育苗半人工育苗是指在室外土池（或滩涂）对亲贝蓄养、育肥，育肥后期在室内进行强化培育，然后在室内进行亲贝的人工催产，人为控制条件孵化受精卵，培养浮游幼虫至出现眼点或附着变态后，再将幼虫从室内水泥地移到室外土地中进行稚贝的培育。1．1受精卵的获取这一育苗过程室内工作的关键是…     

近江牡蛎受精过程、胚胎及早期幼虫发育特征

为了解近江牡蛎(Crassostrea ariakensis)从受精到早期幼虫发育阶段的发育特性，在水温22～24℃、盐度20～22的实验室环境中对采自山东东营丁字湾海域的近江牡蛎进行人工授精，利用普通光学显微镜和荧光显微镜对近江牡蛎受精、早期胚胎和幼虫发育过程中的形态和核行为变化进行观察，并对这一过程中牡蛎的壳长变化进行了统计分析。结果表明，近江牡蛎成熟的未受精卵呈梨形，卵径为50μm左右，核相处于第一次成熟分裂中期。受精卵在受精后15～20 min、25～30 min,先后排出第一、第二极体，完成第一次和第二次成熟分裂，在受精后30 min左右先后形成雄原核和雌原核；雌、雄原核各自形成染色体组，在卵子中央发生联合，染色体排列于赤道板上，形成第一次有丝分裂的中期分裂相；受精后45 min左右，受精卵进行第一次卵裂，形成2个体积不等的卵裂球；受精75 min后，受精卵开始第二次卵裂，90 min后形成4个卵裂球，进入4细胞时期；6 h后受精卵发育至桑葚期，8～10 h进入囊胚期，12～15 h后发育至担轮幼虫，27～30 h左右发育成D形幼虫，5 d左右进入壳顶幼虫时期，17 d后幼虫...     

中国蛤蜊生产性人工育苗试验

2016～2017年,对中国蛤蜊(Mactra chinensis)生产性人工育苗技术进行了试验研究,2016年培育出平均壳长3.5mm幼贝0.46亿粒;2017年培育出平均壳长3.8mm幼贝0.14亿粒。试验发现,中国蛤蜊在丹东近海自然海区繁殖盛期在5月中旬～6月中旬,雌雄性比约1∶1;壳长5cm左右的亲贝产卵量50万～75万粒/个,受精卵为沉性卵,卵径55μm;在水温23～24℃,盐度26‰、pH值8.0的条件下,受精卵经18h发育为D型幼虫,壳长75μm;幼虫经13～14d培育,壳长280～300μm时开始附着变态为稚贝,日生长量15.9～16.5μm;稚贝经30d培育,平均壳长可达35～38mm,平均日生长107～117μm。     

大竹蛏人工繁育与中间育成技术

2015~2017年连续3年进行大竹蛏人工繁育试验与生产,累计培育出平均壳长3~6.1 mm蛏苗1.62亿粒,对大竹蛏(Solen grandis)繁殖习性及人工繁育技术进行了研究。结果显示,大竹蛏卵子分批成熟,多次产卵。在水温18~25℃条件下,受精卵约经22~35h发育为D型幼虫,D型幼虫经6~10d培育变态为稚贝,日生长量14~25μm,成活率66.9%~73.3%。以细沙为附着基进行稚贝培育和中间育成,成活率可达53.5%~77.3%,日生长量150~166μm。     

Association between the interannual variation in the oceanic environment and catch rates of bigeye tuna (Thunnus obesus) in the Atlantic Ocean

The environmental processes associated with variability in the catch rates of bigeye tuna in the Atlantic Ocean are largely unexplored. This study used generalized additive models (GAMs) fitted to Taiwanese longline fishery data from 1990 to 2009 and investigated the association between environmental variables and catch rates to identify the processes influencing bigeye tuna distribution in the Atlantic Ocean. The present findings reveal that the year (temporal factor), latitude and longitude (spatial factors), and major regular longline target species of albacore catches are significant for the standardization of bigeye tuna catch rates in the Atlantic Ocean. The standardized catch rates and distribution of bigeye tuna were found to be related to environmental and climatic variation. The model selection processes showed that the selected GAMs explained 70% of the cumulative deviance in the entire Atlantic Ocean. Regarding environmental factors, the depth of the 20 degree isotherm (D20) substantially contributed to the explained deviance; other important factors were sea surface temperature (SST) and sea surface height deviation (SSHD). The potential fishing grounds were observed with SSTs of 22–28°C, a D20 shallower than 150 m and negative SSHDs in the Atlantic Ocean. The higher predicted catch rates were increased in the positive northern tropical Atlantic and negative North Atlantic Oscillation events with a higher SST and shallow D20, suggesting that climatic oscillations affect the population abundance and distribution of bigeye tuna.     

Growth performance,digestive enzyme activity and immune response of Japanese sea bass,Lateolabrax japonicus fed with fructooligosaccharide

In this experiment, a feeding trial was performed to determine the effects of fructooligosaccharide (FOS) on growth performance, digestive enzyme activity and immune response of Japanese sea bass, Lateolabrax japonicus juveniles (initial weight 38.3 ± 0.5 g), and the fish were examined following feeding with six levels of FOS (0, 0.5, 1, 2, 4 and 6 g/kg) for 28 days. Significant enhancement of weight gain (WG) and specific growth rate (SGR) was found in fish fed 1 g/kg FOS incorporated diets (p < .05), while the feed conversion ratio (FCR) in the 1, 2 g/kg FOS groups reduced significantly compared with the control (p < .05). Besides, the crude lipid in the 4, 6 g/kg FOS groups increased significantly compared with the control (p < .05). On the other hand, the erepsin and lipase activities significantly elevated in intestine of fish fed 2 g/kg FOS (p < .05) and the lysozyme activity in serum of fish fed 2 g/kg FOS were significantly higher than that in the control (p < .05). Moreover, the alkaline phosphatase activities in serum of fish fed 0.5, 1, 2 g/kg FOS were significantly higher than in control (p < .05). Regression analysis showed that the relationships between dietary FOS levels and either SGR, FCR, erepsin or lysozyme activities were best expressed by regression equations, and the optimal inclusion levels are 1.37, 1.80, 3.06, 3.11, 1.93 and 1.80 g/kg for SGR, FCR, erepsin, lipase, lysozyme and total superoxide dismutase activities, respectively. Overall, this study revealed that FOS incorporated diets could beneficial for L. japonicus culture in terms of increasing the growth, digestion and immune activities. Under the present experimental condition, the optimal supplementary level of FOS in the diet of L. japonicus is 1–3 g/kg.     

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17 (E₂), testosterone (T), 17,20-dihydroxy-4-pregnen-3-one (DHP) and 17,20,21-tri-hydroxy-4-pregnen-3-one (20-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E₂ and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E₂ and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20-S and oocyte GVBD by white perch follices. DHP and 20-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20-S in the control of FOM in white perch and white bass.     

Cardiac,ventilatory and metabolic responses of two ecologically dissimilar species of fish to waterborne cyanide

Changes in heart rate, ventilatory activity and oxygen consumption were determined in trout (Salmo gairdneri) and brown bullhead catfish (Ictalurus nebulosus) during exposure to a steadily increasing concentration of waterborne cyanide selected to produce death in 8–9 hours for each species. The lethal cyanide concentration for the bullheads was an order of magnitude higher than for trout. Trout developed an immediate and gradually increasing bradycardia throughout the exposure period. Cyanide produced tachycardia in the bullhead followed by a gradual onset of bradycardia as the concentration of cyanide was raised. Pericardial injection of atropine (a muscarinic cholinergic antagonist) indicated that bradycardia in the trout was due initially to increased vagal tone but later due to the direct effect of cyanide on the heart. Hyperventilation in the trout persisted throughout the exposure period, although the rate and amplitude fluctuated and was variable between individual fish. During the last hour of exposure (highest cyanide concentration), ventilation was characterized by rapid, shallow breaths followed by a sudden respiratory arrest. The bullheads exhibited hyperventilation during the first 3 hours of exposure followed by a gradual, linear drop in ventilation rate and amplitude until death occurred. Cardiac and ventilatory responses in both species were attributed to stimulation of central and peripheral chemoreceptors by cyanide. Evidence is presented which suggests the initial response in the bullheads was due, at least in part, to gustatory stimulation by the cyanide. Oxygen consumption of the trout remained above pre-exposure levels for the majority of the test period. Oxygen consumption in the bullhead paralleled the changes in heart and ventilatory rates. Whole-body lactate levels of fingerlings of both species during cyanide exposure were measured to estimate the extent of anaerobiosis. Whole-body lactate levels were much greater in the bullheads than the trout, indicating a higher capacity for anaerobiosis, possibly due to a greater fuel supply. Overall, the trout responded to cyanide in a manner similar to that produced by environmental hypoxia whereas the bullheads experienced a gustatory stimulus which masked the hypoxia-like response.     

An overview of stress physiology of fish transport: changes in water quality as a function of transport duration

This study brings an integrated analysis about the relationship between water deterioration and its physiological consequences in live fish transport. The analysis was focused on the transport water and its deterioration, and physiological challenges imposed on the fish. Usual commercial handling procedures employed to mitigate fish stress during transport were discussed. Future topics of research for the establishment of safer fish transport protocols were proposed. Transport was classified into short (≤8 h) or long transport (>8 h). The main issue in short transports should be the prevention of water pH reduction, while in long transports it is the increase in ammonia. Plasma cortisol is the most employed marker for stress and is acutely elevated upon short episodes of transport, but remains elevated even in long‐transport events. Plasma glucose is perhaps a better marker for handling stress. Plasma lactate, pH, osmolality CO₂ and ions should be more often evaluated. Plasma Na⁺ and Cl^‐ are very useful markers of acidosis, due to their respective exchange for H⁺ and , for acid–base regulation. The establishment of species‐specific transport protocols should be preceded by such combined analyses of water and physiological parameters.     

Are hatchery‐reared abalone naïve of predators? Comparing the behaviours of wild and hatchery‐reared northern abalone,Haliotis kamtschatkana (Jonas, 1845)

Abalone populations have declined worldwide, generating interest in enhancement using hatchery‐reared individuals. In many cases, such restoration efforts have met with limited success due to high predator‐induced mortality rates. Furthermore, the mortality rates of outplanted hatchery abalone are often considerably higher than for wild individuals. This study uses northern abalone (Haliotis kamtschatkana) as a case study to determine whether hatchery‐reared abalone behave differently than their wild counterparts. In the field, outplanted hatchery‐reared abalone were significantly less responsive than wild abalone, in terms of number of abalone responding and intensity of response, to nearby movement and to physical contact with an inert probe. Also, when encountering a cue to which all abalone responded (a seastar predator), hatchery‐reared individuals remained subdued. Anti‐predator behavioural deficits in hatchery‐reared abalone were more pronounced in 4‐year‐old individuals than in 1‐year‐old individuals, suggesting an influence of either age or amount of time spent in the hatchery environment. These behavioural differences are expected to increase the vulnerability of hatchery‐reared abalone to predators, and are likely a major cause of their elevated predator‐induced mortality when outplanted.     

Effects of cadmium on the kinetics of calcium uptake in developing tilapia larvae, Oreochromis mossambicus

The toxic effects of Cd²⁺ on Ca²⁺ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l^-1 of Cd²⁺ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca²⁺ uptake within 4h resulting in a great increase in K_m values for Ca²⁺ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca²⁺ influx of larvae in solutions of 0.2 mM Ca²⁺ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd²⁺ than 0 day-old larvae. Although the Ca²⁺ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l^-1 Cd²⁺ solution, total body Ca²⁺ content was significantly reduced in 3 day-old larvae. Increased Ca²⁺ uptake efficiency ensures sufficient Ca²⁺ for normal growth. However, rapid increase in Ca²⁺ influx after hatching also leads to higher Cd²⁺ uptake. Exposure to Cd²⁺ will lead to a drop in body Ca²⁺ content resulting in retardation of larval growth. Therefore, we conclude that if Ca²⁺ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca²⁺ and will show signs of Cd²⁺ poisoning.     

Migratory dynamics of stream-spawning longnose gar (Lepisosteus osseus)

Abstract– Literature evidence suggests that lake-dwelling longnose gar (Lepisosteus osseus) enter tributary streams to spawn, Until the present study, the dynamics of this breeding migration had never been investigated quantitatively. During the summers of 1991 and 1992, longnose gar were captured as they entered Weaubleau Creek, Missouri, a tributary of Harry S. Truman Reservoir. The in-stream spawning migration began in early April and ended in late May, and was positively correlated with stream flow and water level, and negatively correlated with water temperature. In-stream residence times ranged from 15 to 94 days, with males exhibiting longer residence times than females. Once in-stream, longnose gar travelled as far as 10 km upstream and occupied certain pools at greater relative frequencies. Although the reason for this preferential utilization is not completely understood, it may relate to pool depth and riffle proximity. Longnose gar disperse from the spawning stream great distances, with gar captured in Weaubleau Creek being recaptured up to 48 km away. This information should provide fisheries biologists the means to consider the reproductive ecology of this species in their conservation and management decisions.     

Nutritional regulation of hepatocyte fatty acid desaturation and polyunsaturated fatty acid composition in zebrafish (Danio rerio) and tilapia (Oreochromis niloticus)

The desaturation and elongation of [1-¹⁴C]18:3n-3 was investigated in hepatocytes of the tropical warm freshwater species, zebrafish (Danio rerio) and Nile tilapia (Oreochromis niloticus). The hepatocyte fatty acid desaturation/elongation pathway was assayed before and after the fish were fed two experimental diets, a control diet containing fish oil (FO) and a diet containing vegetable oil (VO; a blend of olive, linseed and high oleic acid sunflower oils) for 10 weeks. The VO diet was formulated to provide 1% each of 18:2n-6 and 18:3n-3, and so satisfy the possible EFA requirements of zebrafish and tilapia. At the end of the dietary trial, the lipid and fatty acid composition was determined in whole zebrafish, and liver, white muscle and brain of tilapia. Both zebrafish and tilapia expressed a hepatocyte fatty acid desaturation/elongation pattern consistent with them being freshwater and planktonivorous fish. The data also showed that hepatic fatty acid desaturation/elongation was nutritionally regulated with the activities being higher in fish fed the VO diet compared to fish fed the FO diet. In zebrafish, the main effect of the VO diet was increased fatty acid Δ6 desaturase activity resulting in the production of significantly more 18:4n-3 compared to fish fed the FO diet. In tilapia, all activities in the pathway were greater in fish fed the VO diet resulting in increased amounts of all fatty acids in the pathway, but primarily eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3). However, the fatty acid compositional data indicated that despite increased activity, desaturation of 18:3n-3 was insufficient to maintain tissue proportions of EPA and DHA in fish fed the VO diet at the same level as in fish fed the FO diet. Practically, these results indicate that manipulation of tilapia diets in commercial culture in response to the declining global fish oil market would have important consequences for fish fatty acid composition and the health of consumers. Scientifically, zebrafish and tilapia, both the subject of active genome mapping projects, could be useful models for studies of lipid and fatty acid metabolism at a molecular biological and genetic level. This revised version was published online in August 2006 with corrections to the Cover Date.     

Protein and amino acid composition from the mantle of juvenile O ctopus vulgaris exposed to prolonged starvation

Protein and amino acid composition of the mantle of juvenile O ctopus vulgaris (Cuvier, 1797) during fasting for 27 days were determined. Average protein content of octopus mantle was of 711.19 ± 46.80 g kg^?1 DW, and it decreased with increasing fasting days. The non‐essential amino acids content was higher (486.18 ± 11.08 g kg^?1 protein) than essential amino acids (425.82 ± 9.15 g kg^?1 protein) at the start of the experiment (unstarved animals). The results suggest that the amino acid profile of the mantle where the most abundant amino acids are Arg, His, Lys, Gly, Leu and Pro could indicate a prolonged fasting condition (>20 days) or poor nutrition of O . vulgaris. This study supports the idea of using mantle for metabolic needs of starved O . vulgaris suggesting that the degradation pathway of amino acids to pyruvate and tricarboxylic acid cycle intermediates was favoured contrary to the degradation pathway of ketogenic amino acids. Special considerations should be taken concerning Thr, Ile, Ser, Ala, Asx (Asp, Asn), Glx (Glu, Gln) (because of their fast intake) and Lys and His (due to their stable contents) during a prolonged period of fasting.