不同附着基质对长茎葡萄蕨藻生长及附着效果的影响

【目的】探索不同附着基质对长茎葡萄蕨藻(Caulerpalentillifera)直立枝生长及藻体附着效果的影响。【方法】对长茎葡萄蕨藻直立枝以垂直砂埋、水平砂埋、塑料网网夹、尼龙网网夹及无附着基质(对照组)五种附着方式进行实验,探究长茎葡萄蕨藻直立枝的生长、附着能力、光合特性参数及营养含量的变化。【结果】垂直砂埋处理下,藻体的新生直立枝质量、质量长度比及球状小枝的直径与其他各组相比最优(P <0.05),分别是0.313 3 g、0.086 6 g/mm和1.67 mm,是对照组的7.38、9.62、1.67倍;水平砂埋与对照组相比,藻体附着能力有显著增强(P <0.05),假根数为26,长度为30.77 mm及假根附着砂砾质量为0.566 0 g;除对照组外,各组最大光能转化效率(Fv/Fm)和实际光化学效率Y(II)值呈先下降后上升趋势,24 h后垂直沙埋藻体Fv/Fm和Y(II)最快恢复原始水平,为0.856μmol·m~(-2)·s~(-1)和0.851μmol·m~(-2)·s~(-1),显著高于其余组(P <0.05);垂直砂埋与水平砂埋处理后的藻体,其可溶性糖含量分别比对照组显著降低34.24%和33.93%(P<0.05),而网夹处理后,没有显著差异(P> 0.05)。垂直砂埋处理对藻体总蛋白含量增加有显著促进作用,是对照组的1.26倍(P <0.05)。【结论】长茎葡萄蕨藻直立枝以垂直砂埋附着方式生长最佳,以水平砂埋附着方式附着更牢固。     

不同LED光质对长茎葡萄蕨藻生长及光合色素的影响

以长茎葡萄蕨藻(Caulerpa lentillifera)为材料,以白光、红光、蓝光、蓝红光(5/1)、蓝红光(1/3)和蓝红光(1/5)为光源,研究了不同LED光质对长茎葡萄蕨藻生长和光合色素的影响。结果表明:蓝红光(5/1)处理能明显增加长茎葡萄蕨藻再生直立枝的鲜重、质量长度比以及再生球形小枝的直径,分别是对照组的1.48倍、1.19倍和1.08倍;红光促进了再生匍匐茎的生长,但显著抑制再生直立枝生长,且红光、蓝红光(1/3)和蓝红光(1/5)抑制再生球形小枝的直径增长,蓝红光(1/3)显著抑制再生匍匐茎的生长。此外,在白光和蓝红光(5/1)处理下,再生直立枝和再生匍匐茎的生长以及再生球形小枝的直径增长不存在显著性差异。光合色素分析发现,蓝光能显著提高长茎葡萄蕨藻的叶绿素a、叶绿素b、类胡萝卜素和总叶绿素的含量。蓝红光(5/1)和白光较适宜选作长茎葡萄蕨藻室内栽培光源。     

不同温度下长茎葡萄蕨藻无机碳利用

【目的】阐明长茎葡萄蕨藻对无机碳的利用方式。【方法】运用pH漂移技术,探索藻体质量、藻体部位、照度和海水体积对长茎葡萄蕨藻(Caulerpa lentillifera)的pH补偿点的影响,并研究在3种不同温度(20、25、30℃)下,乙酰唑胺(AZ)、乙氧苯丙噻唑磺胺(EZ)、4,4′-二异硫氰基芪2,2′-二磺酸(DIDS)、钒酸盐(Van)4种抑制剂对长茎葡萄蕨藻无机碳的利用影响。【结果】藻体质量、藻体部位、照度和海水体积对长茎葡萄蕨藻的pH补偿点均无显著性影响(P>0.05),在一定范围内藻体质量或照度越大,达到pH补偿点时间越短,且pH补偿点均大于9。20℃下各抑制剂的抑制作用最大,其次为30℃,25℃最小,但3种温度下各抑制剂的抑制率无显著差别(P> 0.05)。4种抑制剂中DIDS对长茎葡萄蕨藻pH补偿点和无机碳利用均无显著影响(P> 0.05),剩余3种抑制剂的抑制作用依次为EZ>AZ>Van。【结论】藻体质量、藻体部位、照度和海水体积对长茎葡萄蕨藻pH补偿点无影响。温度对长茎葡萄蕨藻吸收利用无机碳没有明显影响。长茎葡萄蕨藻能利用HCO_3^-作为无机碳源进行光合作用。     

Fe~(2+)和Fe~(3+)对长茎葡萄蕨藻生长、铁含量和生理特性的影响

【目的】探索两种无机铁对长茎葡萄蕨藻(Caulerpa lentillifera)的生长、铁含量及生理特性的影响。【方法】分别以三氯化铁(FeCl_3)和硫酸亚铁(FeSO_4)作为铁源,采用单因素实验方法,研究在不同浓度Fe~(2+)、Fe~(3+)条件下,长茎葡萄蕨藻的生长、光合色素含量、铁含量、两种过氧化酶(CAT、T-SOD)活性,以及总蛋白、维生素C和可溶性糖含量。【结果】在水体中无论是添加Fe~(2+)还是Fe~(3+),藻体的特定生长率(SGR)、光合色素含量、铁含量、过氧化物酶活性和维生素C含量均显著高于对照组(P <0.05)。藻体的铁含量随着培养液中铁离子浓度的升高而增加,以Fe~(2+)和Fe~(3+)处理后,藻体铁最高值分别可达到1 522.54μg/g和1 373.93μg/g,增幅为1 369.34%和1 225.92%;藻体维生素C最高质量分数分别可达15.41μg/mg和12.89μg/mg,增幅为107.56%和73.58%。Fe~(2+)实验组对藻体的可溶性糖含量有显著影响(P <0.05)。实验藻体的总蛋白含量显著低于对照组(P <0.05)。【结论】藻体在3 mg/L Fe~(2+)或者6 mg/L Fe~(3+)的条件下,长茎葡萄蕨藻生长最佳,其营养品质可得以改善。     

Comparative Analysis of Nutrient Composition of Caulerpa lentillifera from Different Regions

This study investigated the difference of nutrient composition in Caulerpa lentillifera collected from different regions.The nutrient compositions of C.lentillifera from China's Hainan and Shandong provinces were determined and compared with those from Semporna(Malaysia),Sabah(Malaysia),Petchburi(Thailand),and two other species of seaweeds(Malaysia).The results showed that the polysaccharide and protein contents of C.lentillifera from Hainan(44.82%±0.98%and 12.5%±0.70%),Shandong(43.22%±1.42%and 14.7%±0.72%),Petchburi(59.27%±2.31%and 12.49%±0.30%),and Sabah(44.02%±2.01%and 19.38%±1.48%)were higher than those of Eucheuma cottonii(26.49%±3.01%and 9.76%±1.33%)and Sargassum polycystum(33.49%±1.70%and 5.40%±0.07%),respectively.The polyunsaturated fatty acid contents in C.lentillifera from Hainan(29.98%)and Shandong(22.11%)were higher than that in Semporna(16.76%±0.27%),Sabah(9.49%),and S.polycystum(20.34%±0.43%),but lower than that in E.cottonii(51.55%±0.57%).In Caulerpa lentillifera of Hainan and Shandong provinces,the essential amino acid(EAA)/total amino acid(TAA)ratios were 35.22%and 38.78%,respectively;and the EAA/ETAA ratios were 54.36%and 63.35%,respectively.The EAA composition of C.lentillifera was close to the ideal model of Food and Agriculture Organization/World Health Organization.C.lentillifera was rich in mineral elements,including calcium((3315.85±127.55)mg(100 g)^-1 and(3728.35±92.38)mg(100 g)^-1),magnesium((6715.74±82.58)mg(100 g)^-1 and(8128.59±242.72)mg(100 g)^-1),and trace elements,including iron((510.65±5.47)mg(100 g)^-1 and(1972.97±183.35)mg(100 g)^-1),selenium((1.04±0.08)mg(100 g)^-1 and(0.83±0.15)mg(100 g)^-1),and zinc((33.90±0.13)mg(100 g)^-1 and(11.75±2.05)mg(100 g)^-1).These results showed that C.lentillifera was more nutritious than S.polycystum or E.cottonii in terms of polysaccharide,protein,and fatty acid contents.Furthermore,both C.lentillifera species collected from Hainan and Shandong provinces show more basic nutrients.Therefore,C.lentillifera has important development and application prospects.     

温度、照度和氮磷营养盐对长茎葡萄蕨藻富硒的影响

【目的】探索富硒长茎葡萄蕨藻(Caulerpalentillifera)的培养条件。【方法】以亚硒酸钠(Na_2SeO_3)为硒源,采用单因素实验,研究不同硒浓度对长茎葡萄蕨藻的生长、光合色素和硒富集量的影响,通过正交实验,找出适宜长茎葡萄蕨藻富硒的最佳温度、照度和氮磷比组合条件。【结果】在亚硒酸钠0、0.5、1.0、2.0、4.0、8.0mg/L条件下,随亚硒酸钠添加量增加,藻体硒质量分数(干基)从1.70μg/g增加至50.10μg/g,且各组间差异均有统计学意义(P<0.05);亚硒酸钠添加量2.0 mg/L时,藻体硒质量分数达到11.7μg/g;添加量大于2.0 mg/L时,显著抑制藻体的生长(P<0.05),藻体叶绿素a和叶绿素b含量显著性降低(P<0.05);添加量低于2.0 mg/L时,藻体的生长、叶绿素a和叶绿素b含量均无显著性差异;类胡萝卜素含量各组间无明显变化。在培养液亚硒酸钠质量浓度为2.0 mg/L的条件下,藻体最适的生长条件组合是温度28℃、照度2 000 lx、氮磷比10∶1,藻体的最优富硒条件是温度24℃、照度2 000 lx、氮磷比8∶1。【结论】长茎葡萄蕨藻在开发含硒安全性功能海藻食品方面有较大应用潜力。     

盐度对半叶马尾藻幼苗生长及光合色素合成的影响

在温度22±0.5℃、光照强度100μmol·m-2·s-1的光照培养箱中,以8组不同盐度培养半叶马尾藻(Sargassum hemiphyllum)幼苗(2~3 g/株),研究不同盐度对其生长发育和光合色素合成的影响。结果表明:半叶马尾藻幼苗适合存活和生长的盐度为24.84~35.28,在该盐度范围内幼苗均可正常存活和生长;幼苗最适生长盐度为30.06,质量增长率达到最大,光合色素含量达到最高;24.84~35.28中,幼苗更适合于在高盐端生长。     

盐度对珠母贝幼虫和稚贝存活和生长的影响

为了解珠母贝早期发育阶段最适存活和生长条件,于2013年5—6月在珍珠贝养殖场进行不同海水盐度对珠母贝直线铰合期幼虫、壳顶期幼虫和稚贝生长及存活的影响实验。结果表明：珠母贝直线铰合期幼虫存活适宜盐度为2285—3886,最适盐度为2719—3502,壳长增长的适宜盐度为2043—4123,最适盐度为3110;壳顶期幼虫存活适宜盐度为2310-3914,最适盐度为2719—3502,壳长增长的适宜盐度为2029—4009,最适盐度为3110·3502;稚贝存活适宜盐度为2064—3910,最适盐度为2719—3502,壳长增长的适宜盐度为1938—4130,最适盐度为2719—3110。     

Effects of salinity on embryonic development,survival, and growth of Crassostrea hongkongensis

This study examined the effects of salinity on embryonic development, survival, and growth of the Hong Kong oyster Crassostrea hongkongensis. The embryos, larvae, and juveniles of C. hongkongensis were held in artificial seawater at three different salinities (low, 15; medium, 23; and high, 30) to determine the optimum hatchery and nursery conditions for mass production of the seeds. Results showed that the percentage production of straight-hinged larvae from fertilized eggs was significantly lower at the high salinity than at the low- and medium-salinities (P < 0.05). The survival rates of larvae and juveniles differed significantly among the three salinity trials, with the highest survival rate observed at the low salinity (P < 0.05). The shell height of larvae was significantly larger at the low salinity than at the high and medium salinities from days 9 to 15 (P < 0.05), whereas that of juveniles was significantly larger at the low salinity than at the high and medium salinities on day 70 (P < 0.05). These results indicate that the larvae and juveniles of C. hongkongensis are tolerant to a wide range of salinities (15 to 30), but show better growth and survival at relatively low salinities. Thus, it is recommended to use relatively low salinities in hatchery and nursery systems for improved yields of C. hongkongensis.     

Effects of nutrients and light intensity on the growth and biochemical composition of a marine microalga Odontella aurita

Algal biotechnology has advanced greatly in the past three decades. Many microalgae are now cultivated to produce bioactive substances. Odontella aurita is a marine diatom industrially cultured in outdoor open ponds and used for human nutrition. For the first time, we have systematically investigated the effects of culture conditions in cylindrical glass columns and fiat-plate photobioreactors, including nutrients （nitrogen, phosphorus, silicon, and sulfur）, light intensity and light path, on O. aurita cell growth and biochemical composition （protein, carbohydrate, β-1,3-glucan, lipids, and ash）. The optimal medium for photoautotrophic cultivation of O. aurita contained 17.65 mmol/L nitrogen, 1.09 mmol/L phosphorus, 0.42 mmol/L silicon, and 24.51 mmol/L sulfur, yielding a maximum biomass production of 6.1-6.8 g/L and 6.7-7.8 g/L under low and high light, respectively. Scale-up experiments were conducted with fiat-plate photobioreactors using different light-paths, indicating that a short light path was more suitable for biomass production of O. aurita. Analyses of biochemical composition showed that protein content decreased while carbohydrate （mainly composed of 15-1,3-glucan） increased remarkably to about 50% of dry weight during the entire culture period. The highest lipid content （19.7% of dry weight） was obtained under 0.11 mmol/L silicon and high light conditions at harvest time. Fatty acid profiles revealed that 80% were Cx4, C~6, and C20, while arachidonic acid and eicosapentaenoic acid （EPA） accounted for 1.6%-5.6% and 9%-20% of total fatty acids, respectively. High biomass production and characteristic biochemical composition profiles make O. aurita a promising microalga for the production ofbioactive components, such as EPA and D-1,3-glucan.     

A 2011 drought event affecting distribution of nutrients and chlorophyll in the Zhujiang River estuary

During the summer of 2011,a severe drought event occurred throughout the Zhujiang(Pearl)River Basin of South China.This decreased runoff into the river,resulting in increased salinity and reduced suspended substance.To examine the effects of this extreme drought on the distribution of nutrients and chlorophyll,we compared two surveys from 2006 and 2011.Results show that dissolved inorganic nitrogen concentration did not change from 2006 to 2011,whereas the proportions of NO 2 – and NH 4 + to DIN in 2011 increased.PO 4 3-concentration was lower in 2011 than in 2006,whereas there was no difference in SiO 3 2-concentration between these years.Correlation coeffi cients of salinity with levels of NO 3 –,NO 2 –,NH 4 +,PO 4 3-and SiO 3 2-in 2011 were all much higher than those in 2006,suggesting greater conservation of dissolved nutrients during the extreme drought event.Furthermore,calculated amounts of regenerated nitrate and phosphorus and their proportions to observed nutrients in 2011 were much lower than in 2006,indicating that nutrient regeneration decreased during the extreme drought period.Mean concentration of chlorophyll a(Chl-a)was considerably higher in 2011 than in 2006,and a harmful algal bloom of Cochlodinium geminatum was observed in the estuary,owing to water stagnancy and lower turbidity as a consequence of drought.Therefore,the extreme drought event in 2011 changed the composition ratio of nutrients,enhanced nutrient conservative behavior,and reduced nutrient regeneration.This affected some key ecological processes in the estuary.     

EFFECTS OF DCMU ON CHLOROPHYLL FLUORESCENCE RATIO F685/F735 IN MARINE RED,BROWN AND GREEN ALGAE

The chorophyll fluorescence ratio F685/F735 in vivo can be a useful indicator for stress detection inhigher plants and seaweed. DCMU [3 - (3, 4 - dichlorophenyl ) - 1, 1 - dimethylurea] treatment influencesthis ratio. Th effects of DCMU on F685/F735 of marine red, brown and green algae under excitationlight of different wavelengths were investigted. In the brown algae, Laminaria japonica and Undariapinnatifida,DCMU did not increase this ratio under blue light excitation but increased the ratio slightlyunder excitation by green light. For the red algea, Halymenia sinensis, DCMU increased the ratiomarkedly under both blue and green ligh excitation. The percentage increase could reach 50% (undergreen light excitation) and was due to unequal enhancement at the two emission maxima by DCMU. Afraction of chlorophyll which contributed to fluorescence in the 735 nm region was less sensitive toDCMU and was likely from photosystem I of red algae. In the green alga, Ulva pertusa, DCMU causeda slight increase in F685     

Effects of salinity, light and temperature on growth rates of two species of Gracilaria （Rhodophyta）

Effects of temperature, salinity and light intensity on growth rates of Gracilaria lichenoides and G. tenuistipitata var. liui Zhang et Xia were tested. Eight to ten levels of each factor were first tested separately. The best growth rate was obtained under the conditions of 32°C, 30 and 240 μmol/(m²·s) for G. lichenoides, and 24°C, 20 and 200 μmol/(m²·s) for G. tenuistipitata, respectively. Then a uniform design was used to evaluate the optimal combinations of the three factors. The best conditions for the highest daily specific growth rates (% increase in wet weight) are determined to be 31.30°C, 32.10, and 287.23 μmol/(m²·s) for G. lichenoides (16.26%/d), and 25.38°C, 21.10, and 229.07 μmol/(m²·s) for G. tenuistipitata (14.83%/d), respectively. Supported by the 908 Special Program (908-02-04-07), the National Basic Research Program of China (973 Program, No. 2006CB400608), and K. C. Wong Magna Fund in Ningbo University     

Effects of salinity, light and temperature on growth rates of two species of Gracilaria (Rhodophyta)

Effects of temperature, salinity and light intensity on growth rates of Gracilaria lichenoides and G tenuistipitata var. liui Zhang et Xia were tested. Eight to ten levels of each factor were first tested separately. The best growth rate was obtained under the conditions of 32～C, 30 and 240 μmol/(m2·s) for G. lichenoides, and 24℃, 20 and 200 μmol/(m2.s) for G. tenuistipitata, respectively. Then a uniform design was used to evaluate the optimal combinations of the three factors. The best conditions for the highest daily specific growth rates (% increase in wet weight) are determined to be 31.30℃, 32.10, and 287.23 μmol/(m2·s) for G. lichenoides (16.26%/d), and 25.38℃, 21.10, and 229.07 μmol/(m2·s) for G. tenuistipitata (14.83%/d), respectively.     

Effects of temperature and salinity on the development of the amphipod crustacean Eogammarus sinensis

The amphipod crustacean Eogammarus sinensis has useful features that make it suitable for use in the aquaculture of fish and large decapod crustaceans.In this study,we investigated the effects of temperature and salinity on the development,fecundity,survival,and growth rate of E.sinensis.The results show that temperature significantly affected E.sinensis development,but salinity.As temperature increased,the duration of E.sinensis embryonic development decreased.Fecundity was affected significantly by temperature and the combination of temperature and salinity,but by salinity alone.In addition,high temperatures accelerated E.sinensis juvenile growth rates,whereas high salinity reduced it.Therefore,our data suggest that E.sinensis tolerates a wide range of salinities and that temperature has more significant effects than salinity on the embryonic development,fecundity,and growth of E.sinensis.Our results shall be useful for mass production of this species for use in aquaculture.     

Effects of temperature and salinity on the asexual reproduction of Aurelia coerulea polyps

Aurelia coerulea polyp is an important stage in the outbreaks of this species. To test the combined ef fects of salinity and temperature on the survival and asexual reproduction of polyps, we maintained 864 polyps at various salinities(15, 25, 33, and 40) and temperatures(9, 12, 15, 18, 21, and 24℃). Polyps could mostly survive in all treatment combinations except in salinity 15 treatments with low temperatures(9–15℃). Budding occurred at all temperatures(9–24℃), while strobilation only occurred at the low temperatures(9–15℃). The range of 12–15℃ was suitable for strobilation and ephyrae release. The optimal range of salinity for asexual reproduction was 25–33. Low(15) or high(40) salinity could signi?cantly reduce the numbers of new buds or ephyrae, and low salinity of 15 retarded and even prevented strobilation at low temperatures. The optimal treatment for budding and strobilation was 21℃-salinity 25 and 12℃-salinity 33, respectively. Salinity had less of an impact than temperature on asexual reproduction, except for the polyps in high or low osmotic pressure conditions.     

Effects of temperature and salinity on survival,growth and DNA methylation of juvenile Pacific abalone,Haliotis discus hannai Ino

Temperature and salinity are two of the most potent abiotic factors infl uencing marine mollusks.In this study,we investigated the individual and combined ef fects of temperature and salinity on the survival and growth of juvenile Pacifi c abalone,Haliotis discus hannai Ino,and also examined the DNA methylation alteration that may underpin the phenotypic variation of abalone exposed to dif ferent rearing conditions.The single-factor data showed that the suitable ranges of temperature and salinity were 16–28°C at a constant salinity of 32,and 24–40 at a constant temperature of 20°C,respectively.The two-factor data indicated that both survival and growth were signifi cantly af fected by temperature,salinity and their interaction.The optimal temperature-salinity combination for juveniles was 23–25°C and 30–36.To explore environment-induced DNA methylation alteration,the methylation-sensitive amplifi ed polymorphism(MSAP)technique was used to analyze the genomic methylation profi les of abalone reared in optimal and adverse conditions.Neither temperature nor salinity induced evident changes in the global methylation level,but 67 and 63 dif ferentially methylated loci were identifi ed in temperature and salinity treatments,respectively.The between-group eigen analysis also showed that both temperature and salinity could induce epigenetic dif ferentiation in H.discus hannai Ino.The results of our study provide optimal rearing conditions for juvenile H.discus hannai Ino,and represent the fi rst step toward revealing the epigenetic regulatory mechanism of abalone in response to thermal and salt stresses.     

Effects of salinity on survival,feeding behavior and growth of the juvenile swimming crab,Portunus trituberculatus (Miers, 1876)

Effect of salinity on survival,feeding behavior and growth of juvenile swimming crab P ortunus trituberculatus was investigated under 5 salinity levels of 5,10,20,30 and 40. The results show that the crab juveniles fed 2 or 3 times at the salinity 20 and 30,each lasted for about 25 minutes,for a total feeding time of 73.2±22.65 minutes per day. At these salinities,there were significantly higher in the frequency of feeding and in total feeding time than those at lower salinities of 5 and 10. All crab juveniles moulted when reared at a salinity of 20 during the 5 days duration of the experiment,which is significantly higher than those at other salinities. All juveniles survived at salinity 20,and the survivorship was not significantly different from that at 30,but was signif icantly higher than those at other salinities. The crab juveniles reared at a salinity of 20 had the highest value of food ration of 0.190 8±0.011 3 g/g BW,average body weight gain of 0.796±0.128 g,gain rate of 87%–96%,and food conversion ratio of 1.20±0.09. There was no significant difference in the values found between 20 and 30 but these values were significantly lower than that at the other salinities( P 0.05). Highest activities of digestive enzymes(Amylase,Protease,Lipase) and lowest activities of protective enzymes(SOD,PO,CAT) were also obtained on crab juveniles reared at salinity of 20.     

COMBINED EFFECTS OF TEMPERATURE, IRRADIANCE AND SALINITY ON GROWTH OF DIATOM SKELETONEMA COSTATUM

3-factor experiment was used to study the combined effects of temperature, irradiance and salinity on the growth of an HAB species diatomSkeletonema costatum (Grev.) Cleve. The results showed that temperature (12, 19, 25, 32 °C), irradiance (0.02, 0.08, 0.3, 1.6)×10¹⁶ quanta/(s·cm²)) and salinity (10, 18, 25, 30, 35) significantly influenced the growth of this species. There were interactive effects between any two of and among all three physical factors on the growth. In the experiment, the most optimal growth condition forS. costatum was temperature of 25°C, salinity of 18–35 and irradiance of 1.6×10¹⁶ quanta/(s·cm²). The results indicatedS. costatum could divide at higher rate and were more likely to bloom under high temperature and high illumination from spring to fall. It was able to distribute widely in ocean and estuary due to its adaptation to a wide range of salinities. This study was supported by the PREPP and National Key Basic Research Project (2001CB4097) NNSFC No. 39950001, 20177023, 49576301, 49906007 and KZCX2-206.     

Effects of salinity fluctuation frequency on the growth, molting rate and hemolymph 20-hydroxyecdysone concentration in Juvenile Chinese shrimp, Fenneropenaeus chinensis

This experiment was conducted to examine the effects of salinity fluctuation frequency on the growth, molting rate and hemolymph 20-hydroxyecdysone (20-HE) concentration for juvenile Fenneropenaeus chinensis with an initial wet body weight of 1.115 g±0.012 g. The salinity of the control treatment (represented by D0) was 28 throughout the experiment, whereas treatments D2, D4, D6 and D8 were subjected to different salinity fluctuation frequencies of 2, 4, 6 and 8 d, respectively. The range of salinity fluctuation was 4. The salinity in treatments D2, D4, D6 and D8 was kept at 28 for 2, 4, 6 and 8 d, respectively; each original salinity was decreased abruptly to salinity 24, which first lasted for another 2 d and was then raised to its initial value 28. This constituted a salinity fluctuation cycle and afterwards the cycle repeated. It was found that: 1) The weight gain of shrimp in treatment D4 was 202.9% and significantly higher than that in treatment D0 (P<0.05). The molting rate in treatment D2 was the lowest, while that in treatment D6 was the highest and significantly higher than those in treatments D0 and D2 (P<0.05). 2) The hemolymph 20-HE concentration of shrimps in all treatments was at low levels and increased first gradually during the inter-molt period and then increased sharply. It reached a peak value during the pre-molt stage, and then decreased abruptly during the post-molt stage when the lowest level occurred. 3) During the post-molt stage, the hemolymph 20-HE concentration in treatment D2 was 7.47 pg μL⁻¹ and significantly higher than that in treatment D0 (P<0.05). There were, however, no significant differences in hemolymph 20-HE concentration among all five treatments during the inter-molt stage (P>0.05). During the pre-molt stage, the hemolymph 20-HE concentration in treatment D6 was significantly higher than that in treatment D0 (P<0.05), whereas the hemolymph 20-HE concentration in treatment D2 was significantly lower than that in other treatments (P<0.05). Adequate salinity fluctuation promoted the molting rate through increasing hemolymph 20-HE concentration at the pre-molt stage.