Effect of saponin on hematological and immunological parameters of the giant freshwater prawn, Macrobrachium rosenbergii

Giant freshwater prawns, Macrobrachium rosenbergii (17.9 ± 2.7 g), exposed to different concentrations of saponin at 0, 0.3, 0.6, 0.9 and 1.2 mg l^− 1 for 168 h were examined for osmolality, electrolyte levels, oxyhemocyanin, protein levels, acid-base balance status, total hemocyte count (THC), phenoloxidase activity, and respiratory bursts. Hemolymph oxyhemocyanin, protein, and pO₂ were inversely related to the saponin concentration. Hemolymph oxyhemocyanin, protein, pO₂, pCO₂, and pH of prawns exposed to 1.2 mg l^− 1 saponin were significantly lower than those of prawns exposed to 0.3 mg l^− 1 and control solutions. However, no significant difference was observed in osmolality or electrolyte levels of prawns exposed to different concentrations of saponin for 168 h. The THC of prawns following 168 h of exposure to 0.9 and 1.2 mg l^− 1 saponin increased, but the phenoloxidase activity decreased suggesting that the decrease in phenoloxidase activity under saponin stress was not a consequence of the increase in THC. We concluded that saponin at as low as 0.9 mg l^− 1 decreases the respiratory protein level and acid-base balance, and modulates the immune system of M. rosenbergii.     

Effect of nitrite on larval development of giant river prawn Macrobrachium rosenbergii

The effects of ambient nitrite concentrations on larval development of giant river prawn Macrobrachium rosenbergii were evaluated. The trials were conducted in two phases: phase 1, larvae from stages I through VIII and phase 2, larvae from stage VIII until post-larvae. In both phases larvae were kept in water with nitrite (NO₂-N) concentrations of 0, 2, 4, 8 and 16 mg/L. Oxygen consumption was analyzed for larvae in stage II at nitrite concentrations of 0, 4, and 8 mg/L. Survival, weight gain, larval stage index and metamorphosis rate decreased linearly with increasing ambient nitrite concentration. However, there was no significant difference between larvae subjected to 0 and 2 mg/L NO₂-N. In phase 1, there was total mortality at 16 mg/L NO₂-N, while in phase 2 larval development stopped at stage X in this treatment. The oxygen consumption in stage II increased significantly at NO₂-N concentration from 0 to 4 mg/L, but there was no difference between 4 and 8 mg/L NO₂-N. In conclusion, increasing ambient nitrite up to 16 mg/L NO₂-N delays larval development, reduces larval growth rate and causes mortality, whereas no significant effect occurs for levels below 2 mg/L NO₂-N. However, the establishment of a general safe level of nitrite to M. rosenbergii hatchery may be difficult due to the great variability in larvae individual sensitivity.     

罗氏沼虾谷氨酰胺合成酶基因的克隆与表达

谷氨酰胺合成酶(glutamine synthetase, GS)是一种广泛分布在动植物体内的酶,并参与细胞多种代谢调控。在甲壳动物中,GS在能量代谢和渗透压调节过程中起着重要作用。实验克隆了罗氏沼虾GS基因。GS基因cDNA全长1 965 bp,开放读码框(ORF)为1 086 bp,编码361个氨基酸(aa),分子量大小为40.75 ku,等电点为5.81。进化树分析发现,罗氏沼虾GS基因与凡纳滨对虾、斑节对虾和中国明对虾GS聚为一支,氨基酸相似性达到95%。氨基酸多序列比对分析结果显示,罗氏沼虾GS属于无脊椎动物分支的GSⅡ群,有5个保守区域。实验对罗氏沼虾GS蛋白进行表达并制备了多克隆抗体。采用荧光定量PCR技术(qRT-PCR)和免疫印迹(Western blot)对罗氏沼虾蜕壳前后的不同组织GS表达进行检测。qRT-PCR结果显示,GS基因在所检测的8个组织中均有表达;蜕壳前,其相对表达量顺序为:肝胰脏肌肉胃肠鳃心脏脑血淋巴。蜕壳后和蜕壳前GS基因在组织中的差异表达比较结果显示,除了在肝胰脏表达下调外,其他7个组织都表达升高,其相对表达量的差异顺序为:脑鳃胃肠肌肉心脏血淋巴。Westernblot结果显示,蜕壳后GS蛋白在鳃和肌肉组织表达量上调,与其mRNA表达一致。此外,罗氏沼虾蜕壳后肝胰脏GS酶的活性和谷氨酰胺的含量下调,而其在鳃、肌肉和血淋巴中上调,结果与其基因表达一致。研究表明,GS基因在不同组织中表达的差异可能和罗氏沼虾的能量代谢、渗透压调节有关。     

Salinity effects on reproduction of giant freshwater prawn Macrobrachium rosenbergii (de Man)

Understanding the role of salinity in breeding and growth has the potential to enhance production of giant freshwater prawn, Macrobrachium rosenbergii. This study investigated the reproduction of females reared in salinities of 0, 6, 12, and 18 g L^− 1. Mean weight of females decreased with increased salinity (31.40 ± 1.54, 25.14 ± 1.16, 20.80 ± 0.81, and 16.62 ± 1.04 g at 0, 6, 12, and 18 g L^− 1, respectively). Larval production was delayed by 2 months in females reared in 12 g L^− 1 compared to 6 and 0 g L^− 1 and the cumulative number of berried females decreased with increased salinity. The number of larvae produced was positively correlated to weight of female. A larval production not only differed between salinity treatments, but also that larval production per gram of female differed between treatments. Females reared in lower salinity of 0 and 6 g L^− 1 produced larger numbers of larvae (12,155 ± 480 and 6519 ± 323, respectively) compared to 12 and 18 g L^− 1 (3751 ± 256 and 0, respectively). The number of larvae produced per gram of female was inversely related to the salinity levels (Y = − 37.54X + 685.65, n = 339, r² = 0.995, p < 0.05). Survival of larvae from females reared at 0 and 6 g L^− 1 was higher than those from females reared in 12 g L^− 1. This study clearly shows that female broodstock reared in lower salinity was larger, reproduced early, and produced more offspring than at higher salinity and this could significantly impact coastal prawn culture where seasonal fluctuation of salinity in the hatchery is common.     

罗氏沼虾几丁质酶3B基因的克隆及其在蜕皮周期中的表达

罗氏沼虾的生长发育及繁殖都与蜕皮紧密相关。几丁质酶是甲壳动物在蜕皮过程中最重要的酶之一。本研究对罗氏沼虾蜕皮周期外观特征和腹肢刚毛进行了观察描述,克隆并分析了罗氏沼虾的几丁质酶Ⅲ基因(MrChi3B),制备了几丁质酶Ⅲ蛋白的多克隆抗体,研究了其在蜕皮周期中的表达。罗氏沼虾几丁质酶基因cDNA的开放阅读框为1 143 bp,编码380个氨基酸,大小为41.91 ku。通过氨基酸序列比对发现,MrChi3B与日本沼虾几丁质酶基因(Chi3B)的同源性最高,为94%。MrChi3B含有一个糖苷键水解酶家族18的催化域。实时定量PCR (qRT-PCR)和蛋白印迹法(WB)检测结果显示,MrChi3B在罗氏沼虾多个组织中均有表达,但是不同组织中的表达有差异。在蜕皮期之后,其在胃、表皮和肌肉中的表达量显著上升。在胃中其表达量在蜕皮间期达到最高;在表皮和肌肉中其表达量在蜕皮后期达到最高;肠中的表达量在蜕皮前期和蜕皮期有所上升;眼柄期的表达量在所有蜕皮期都偏低。本研究结果为进一步研究几丁质酶的功能提供参考依据。     

饲料中n-3 PUFA/n-6 PUFA比值对罗氏沼虾幼虾生长性能和抗氧化能力的影响

为探讨饲料多不饱和脂肪酸n-3 PUFA/n-6 PUFA比值对罗氏沼虾幼虾生长性能、虾体肌肉组成、抗氧化能力、血清生理指标以及消化能力的影响,实验设计了n-3 PUFA/n-6 PUFA比值分别为0.37 (D1)、0.59 (D2)、0.93 (D3)、1.51 (D4)和4.38 (D5)的5种等氮等脂饲料饲喂罗氏沼虾幼虾8周,每组设4重复,每个重复40尾虾 。结果显示,饲料n-3 PUFA/n-6 PUFA比值对罗氏沼虾幼虾存活率 (SR)无显著影响;实验虾终末体重 (FW)、增重率 (WGR)和特定生长率 (SGR)随饲料n-3 PUFA/n-6 PUFA比值增加先升后降,均在D3组最高;且D3组虾有最大的肝胰腺蛋白酶活性及脂肪酸合成酶活性。虾体肌肉粗蛋白质、水分和灰分含量不受饲料n-3 PUFA/n-6 PUFA比值影响,但总脂肪含量在D3组显著高于其他组;各组虾体肌肉的n-3 PUFA/n-6 PUFA比值的变化趋势与饲料的n-3 PUFA/n-6 PUFA比值变化趋势呈正相关。随饲料n-3 PUFA/n-6 PUFA比值增加,实验虾血清和肝胰腺中超氧化物歧化酶 (SOD)活性、总抗氧化能力 (T-AOC)和血清铜蓝蛋白 (CP)含量均呈现先升后降趋势,并在n-3 PUFA/n-6 PUFA比值为0.93~1.51时达到最大,但丙二醛 (MDA)含量持续上升;D1组血清总胆固醇 (T-CHO)和甘油三酯 (TG)含量显著高于其他组;血清谷草转氨酶 (AST)和谷丙转氨酶 (ALT)活性先降后升,且D3组最低。研究表明,饲料适宜的n-3 PUFA/n-6 PUFA可显著提升罗氏沼虾生长性能和抗氧化能力,对增重率和特定生长率进行折线回归,建议罗氏沼虾幼虾饲料中最适n-3 PUFA/n-6 PUFA比值为0.86~0.94。     

The isosmotic concept in relation to the aquaculture of the giant prawn, Macrobrachium rosenbergii

Several workers have suggested that maximal growth of an organism should occur in isosmotic media, since the animals would not be expending energy in doing osmotic work. Growth and osmoregulatory studies, however, show that this is not true in the giant prawn, Macrobrachium rosenbergii. This paper attempts to explain the phenomenon.     

Distribution of a fish pathogen Listonella anguillarum in the Japanese flounder Paralichthys olivaceus hatchery

The present study was undertaken to investigate the distribution of Listonella anguillarum in a Japanese flounder (Paralichthys olivaceus) hatchery. A total of 2704 isolates were obtained from the developing fish, live diets and artificial feeds of Japanese flounder and their rearing water, 439 of which were identified as L. anguillarum by the combining incubation on thiosulfate-citrate-bile salt-sucrose (TCBS) agar at 35 °C overnight with polymerase chain reaction (PCR) detection for the VAH1 hemolysin gene. L. anguillarum was detected in all seven rotifer samples, with densities of 2.5 × 10³ to 4.6 × 10⁶ colony forming units (CFU) g^− 1. Both the analyzed samples of Nannochloropsis oculata contained this bacterium at densities of 1.6 × 10⁴ to 1.4 × 10⁵ CFU g^− 1. L. anguillarum was detected in only one of four samples of Artemia nauplii with a density of 4.8 × 10⁵ CFU g^− 1 (35%) and it was not detected in the two analyzed artificial feed samples. L. anguillarum was detected in 11 of 18 specimens of larval and juvenile Japanese flounder at densities of 5.0 × 10¹ to 7.4 × 10⁵ CFU g^− 1, while it was not detected in the two analyzed egg specimens of Japanese flounder. These results indicate that L. anguillarum associated with the developing Japanese flounder is likely derived from rearing water and live diets such as rotifers. Further, it is strongly suggested that L. anguillarum is a transient bacterium of the intestinal microflora for the Japanese flounder but is a permanently indigenous one for the Japanese flounder hatcheries.     

A comparative study on larviculture techniques for the giant freshwater prawn, Macrobrachium rosenbergii (de Man)

Comparative studies of larviculture of Macrobrachium rosenbergii (de Man) were made for three systems: (1) the static water system with partial changes of water, (2) the closed recirculating water system with a separate subsand filter unit, and (3) the closed recirculating water system with a subsand filter inside the rearing tank. The mean production of juveniles per unit volume of water of these three systems was comparable (3.2, 1.9, and 2.9, respectively). Production fluctuated more in the static system than in the closed recirculating system. A significant asymptotic relationship between the stocking density and the survival of prawn larvae was observed in the first type of the closed recirculating system; higher stocking density resulted in lower survival. A stocking density of 20 larvae/l in the closed recirculating system was considered to be good for growth and survival. The intermittent high nitrite level was a problem encountered in the static system but not in the closed recirculating system. The operational costs of these three systems were discussed.     

罗氏沼虾养殖群体表型性状间的相关性及类群差异分析

为研究罗氏沼虾(Macrobrachium rosenbergii)养殖群体表型性状间的相互关系及不同类群间的性状差异,本研究对人工养殖的罗氏沼虾雌、雄及“老头虾”3个类群共490个个体的体重、体长、全长等12个表型性状进行了相关分析、形态性状对体重影响的通径分析等。结果表明, 3个类群除上、下额刺数2个可数性状外,其他9个可量形态性状与体重都呈极显著的正相关(P<0.01);影响体重的关键形态性状在3个类群中各不相同,但体长、头胸甲长、第二步足长在3个类群中均是影响体重的关键指标;分别建立了各类群体重与关键形态性状的多元回归方程。聚类分析和主成分分析结果表明,雌、雄2个类群表型上更为相似,“老头虾”与雌性个体的差异最大。腹部轮廓特征(包括腹长、腹宽、腹高)、全长、体长及第二步足长对3个类群的差异贡献较大。雌性个体腹部发达,“老头虾”则第二步足尤为发达。本研究结果可为罗氏沼虾的选择育种、基础生物学及行业标准的制定提供数据资料。     

Serotonin induces ovarian maturation in giant freshwater prawn broodstock, Macrobrachium rosenbergii de Man

This study investigated the effects of serotonin (5-hydroxytryptamine or 5HT) on ovarian development in Macrobrachium rosenbergii de Man. Adult female prawns at the ovarian stage I (spent) were injected with 5HT at 1, 5, 10, 20 and 50 μg g^− 1 body weight (BW) intramuscularly on days 0, 5 and 10, and sacrificed on day 15. The doses as related to the effect could be categorized into three levels: low (1 and 5 μg g^− 1 BW of 5HT), medium (10 and 20 μg g^− 1 BW of 5HT) and high (50 μg g^− 1 BW of 5HT). The low-dose, especially at 1 μg g^− 1 BW, caused prawns to exhibit a significant increase in ovarian index (ovarian weight/body weight × 100) (5.79 ± 0.09%) as compared to the control (1.49%). The ovaries of most of these prawns could develop to stage IV (mature) and contained synchronously mature oocytes while most of the control ovaries remained at stage I and II (proliferative), and contained only oogonia to previtellogenic (Oc1, Oc2) and early vitellogenic oocytes (Oc3). The medium- and high-dose treated prawns exhibited ovaries that could reach stages III and IV and contained various types of oocytes of different maturity. Pretreatment with 5HT receptor antagonist, cyproheptadine (CYP), at 10 μg g^− 1 BW before 5HT injection significantly suppressed the effect of 5HT. Intramuscular injection of the 5HT-primed thoracic ganglion culture medium into CYP-pretreated prawns resulted in the increase of ovarian index about 5–6 times more than in the control, and in the groups injected with 5HT-primed media from muscle strip, eyestalk and brain. The ovaries of most prawn could develop up to stage IV and contained synchronously developed vitellogenic (Oc4) and mature oocytes (Oc5). These findings suggest that 5HT indirectly induces ovarian development and oocytes maturation in M. rosenbergii, probably via a putative ovarian stimulating factor released from the thoracic ganglia.     

Morphological characterization of larval stages and first juvenile of the freshwater prawn Cryphiops caementarius (Molina, 1782) (Decapoda: Palaemonidae) under laboratory conditions

Research has been in progress for several years on various aspects of the biology and ecology of the freshwater prawn Cryphiops caementarius, an inhabitant of rivers in northern Chile. The commercial value of this prawn fomented the accomplishment of studies on its reproduction and development with the aim of producing juveniles under controlled conditions, to be followed by growout to commercial size in managed culture systems. The present study describes larval culture of this species from eggs of gravid females obtained in the field, from the first developmental stage (Zoea I) through the first juvenile stage. The larvae were cultured at 25 °C in UV sterilized water at variable salinities based on the requirements of the developmental stages. Larvae were fed with Nannochloris, Isochrysis and Artemia nauplii as required. This report describes in detail the 18 larval stages of this prawn, as well as its first juvenile form.     

Preparation of monoclonal antibody against Macrobrachium rosenbergii Nodavirus and application of TAS-ELISA for virus diagnosis in post-larvae hatcheries in east China during 2000-2004

“Whitish muscle disease” of Macrobrachium rosenbergii, also called “whitish disease” or “white tail disease”, is a new serious epizootic disease that has occurred in recent years in giant freshwater prawn culture regions, mainly in southern China. This disease occurred in post-larvae 3-5 days to 3 weeks after desalting. Clinical signs include the development of white spot in muscles or milky muscles throughout the body, causing serious loss in few days, with a mortality rate of 40-90%. A 26-27 nm icosahedral non-enveloped virus, identified as M. rosenbergii Nodavirus (MrNV), was confirmed as the aetiological agent. Twelve hybridomas strongly secreting monoclonal antibodies (Mabs) against MrNV were shown to be specific for MrNV and reacted with MrNV 42 kDa coat protein by Western blot. A triple antibody enzyme-linked immunosorbent assay (TAS-ELISA) was developed and shown to be a useful diagnostic tool for MrNV infection.     

Observations on the breeding and growth of the giant freshwater prawn Macrobrachium rosenbergii (de Man) in the laboratory

Three male and 20 female prawns, Macrobrachium rosenbergii (de Man), were observed for 390 days. They were maintained in brackish water (5%. salinity) at 28°C which was recycled continuously through a percolating biological filter. Illumination was artificial and did not exceed 10 lm/ft² (approx. 0.1 m²) at the water surface. Mating readily occurred in the experimental tanks (48 × 28 × 25 cm deep). Eggs were incubated for 20 days; the mean number of larvae per brood was 24 000 (range 50–98 100). Over 750 000 larvae were hatched during the experiment. Larger females had proportionately larger broods and larvae from seven broods were cultured to the post-larval stage at intervals throughout the experimental period, which demonstrated their viability.The increase in length of the adults at each moult was constant (arithmetic growth) and did not alter when ova were maturing in the ovary.Prawns achieved larger mean length increments after the environmental conditions were improved. The moulting frequency was very variable and, with one exception, did not change proportionately with length or age of the prawns.Females grew from 115 to 205 mm and males from 145 to 230 mm total length.Three females spawned more than four times in successive intermoult periods, and one produced viable larvae five times in succession.Two of the males sired viable larvae four and seven times respectively during one intermoult period.     

Evaluation of vitamin C-enriched Artemia nauplii for larvae of the giant freshwater prawn

The effect of high levels of ascorbic acid (AA) delivered through enriched live food has been verified through the successful culture of larval giant freshwater prawn, Macrobrachium rosenbergii. Two successive feeding trials were set up using a control (550 g AA g^–1 DW) and two different AA-enrichment levels in Artemia (1300 and 2750 g AA g^–1 DW). Under standard culture conditions, no differences in growth nor survival could be observed demonstrating that the nutritional requirements are below 550 g AA g^–1 DW, which is the normal level occurring in freshly-hatched Artemia. However, a significantly positive effect could be demonstrated on the physiological condition of the postlarvae, measured by means of a salinity stress test, when vitamin C-boosted live food was administered. Since the AA levels in the predator larvae are linked with the enrichment levels in the live prey, it may be assumed that a positive influence on stress resistance was caused by feeding vitamin C-enriched Artemia. It is expected that under suboptimal conditions, supplementation of high vitamin C levels might also enhance production characteristics.     

Classification of differentiating oocytes during ovarian cycle in the giant freshwater prawn, Macrobrachium rosenbergii de man

Based on the light microscopic observations of cells' sizes, chromatin patterns, amount of lipid droplets and yolk granules, the female germ cells could be classified into four different phases, which include 1) oogonia (Oog), 2) primary oocytes (pOc), 3) secondary oocytes (sOc), and 4) mature oocyte (mOc). Oog are small oval-shaped cells with irregular-shaped nuclei sizing 4–6 μm in diameter. They rest on the connective tissue germinal cord at the tip of each ovarian pouch (lobule). Oogonia increase their number through mitotic division, and the daughter cells move into ovarian pouch where they undergo first meiotic division to become primary oocytes, which have various steps of 1st meiotic prophase accumulating at the innermost zone of the ovarian pouch. The primary oocytes are small oval-shaped cells (8.5–10 μm in diameter) with large nuclei containing chromatin in various states of condensation that finally transform into chromatids. Their nuclei are surrounded by thin rim of faint blue-stained cytoplasm. The secondary oocytes derived from 2nd meiosis and comprise five steps: Oc1 and Oc2, classified as previtellogenic oocytes, Oc3 and Oc4, classified as vitellogenic oocytes, and mature oocyte (mOc) The zones of ovarian pouch are defined based on the accumulation of various steps of developing oocytes, namely, oogenic, previtellogenic, vitellogenic and mature zones, respectively. The ovarian cycle is divided into five stages based on the number and types of oocytes present in each stage. Stage 0 and I are spawn and spent stages. Stage II and III are proliferative and premature stages, while stage IV is mature stage. During ovarian stage I, each ovarian pouch contains primarily oogonia, primary oocytes, Oc1 and a few Oc2. In stage II, the pouch contains mainly Oc2 and Oc3, while in stage III the predominant cells are Oc4. Mature oocytes appear synchronously, in stage IV. The ovulating mature oocytes pass through the thin disrupted wall of ovarian pouch into subcapsular space, that leads into the oviduct situated on the ventro-lateral side of the ovarian lobe. At spawning, the ovarian pouches break down and only connective sheaths and hemolymph sinuses remain. The germinal cords and islets of oogonia remain in the central area of stage 0 ovary. The ovarian capsule, including the muscular layer, becomes attenuated as the ovary progresses from stage 0 to IV. The hemolymph vessels become highly convoluted in the central area of the ovary, and they branch radially into smaller hemolymph sinuses around each oogenic pouch.     

Usage of electrolytic water system in the giant freshwater prawn,Macrobrachium rosenbergii (de Man) larval hatchery system

The purpose of this study was to use an electrolytic oxidizing (EO) water system in a prawn hatchery. The results of the EO water generation efficiency showed that available chlorine in the EO water increased as the salinity and electric power increased, but was reduced as the water flow rate increased. A bactericidal activity assay showed that the growth of six aquatic pathogens was well inhibited by incubation with EO water containing 1 mg L^?1 of available chlorine. The removal of NH₃‐N and NO₂‐N by electrolysis at 15‰ and 5 W had significant effects, and the removal rate of NO₂‐N was much faster than that of NH₃‐N. Prawn zoea (Z) reared in EO water with different levels of available chlorine at 0 (control), 0.2, 0.3 and 0.4 mg L^?1 had mortalities of 0%, 12%, 27% and 42%, respectively, after 72 h. However, Z were able to well survive in activated carbon‐treated EO water for 1 week. For the on‐farm use of the EO water system in a prawn hatchery, larvae in the EO water group had faster development and higher survival than those in the activated carbon group. From these results, we believe that the EO water group had excellent water quality and lower bacterial counts resulting in increased larval development and survival.     

Prey ingestion and live food selectivity of marble goby (Oxyeleotris marmorata) using rice field prawn (Macrobrachium lanchesteri) as prey

Marble goby (Oxyeleotris marmorata), a carnivorous fish native to freshwater in Asia-Pacific region, is a high-valued species in many Asian countries. The present study consisting of three experiments was conducted to determine the appropriate density, size and ingestion time of marble goby fingerlings on rice field prawn (Macrobrachium lanchesteri) as prey. Results showed that the ingestion rate of marble goby fingerlings (0.26-1.43 g size) on prawns (9-12 mm in length) had an asymptotic pattern peaked at a predator to prey ratio of 1:20. Marble goby fingerlings did catch prawns during both daytime (07:00-17:00 h) and nighttime (17:00-07:00 h), but the ingestion peaked during nighttime period. The hourly ingestion rate during nighttime was significantly higher than that during daytime for the smaller-size marble goby fingerlings of 0.26-0.87 g, while there was no significant difference in the hourly ingestion between nighttime and daytime for the larger-size marble goby fingerlings of 1.43 g. The daily ingestion of marble goby fingerlings on prawns (mg consumed prawns/goby/day) increased significantly with increasing average weights (g) of marble goby fingerlings (Y = 27.6 + 47.8X, n = 30, r² = 0.86, p < 0.05). Results also showed that the preferred prawn size of marble goby fingerlings of average weights of 0.26-4.18 g was small (9-12 mm) with positive electivity index of 0.19-0.33, and the shift from small- to medium-size (12-14 mm) prawns was slow. The present study has demonstrated the feasibility of using rice field prawns as live foods to nurse marble goby fingerlings.     

大豆抗原蛋白对罗氏沼虾生理生化及免疫的影响

为探讨大豆抗原蛋白与豆粕饲用效果的关系,本研究配制4种等氮等能的实验饲料,以含有21.5%鱼粉、15.45%豆粕和15%发酵豆粕的实用饲料为基础饲料(T15组),用发酵豆粕完全替代T15组中的豆粕(TF组),比较发酵豆粕对豆粕的替代效果;再以鱼粉、酪蛋白和大豆分离蛋白为主要蛋白源分别配制与T15、TF组相近抗原蛋白含量的半纯化饲料AP5、AP0(抗原蛋白含量分别为5%和0%)组,探究抗原蛋白的生物学效应。选用初始体重为(0.17±0.02) g的罗氏沼虾(Macrobrachium rosenbergii)在室内水泥池网箱中进行为期64 d的养殖实验。结果显示:两种系列饲料中,大豆抗原蛋白含量的降低对罗氏沼虾生长、血清生化指标及免疫相关基因表达有不同的影响。在实用饲料组中,随着大豆抗原蛋白的降低,罗氏沼虾的增重率、肝胰腺蛋白酶活力、血清白蛋白、总蛋白、鳃Toll受体mRNA、NF-κB mRNA和肝胰腺HSP70 mRNA相对表达量都显著降低(P0.05),而血清超氧化物歧化酶活力显著升高(P0.05);在纯化饲料组中,随着大豆抗原蛋白的降低,罗氏沼虾的增重率、血清超氧化物歧化酶活力和丙二醛含量、肝胰腺HSP70mRNA相对表达量没有显著性差异(P0.05),肝胰腺淀粉酶活力、蛋白酶活力、血清白蛋白、总蛋白都显著降低(P0.05),而肌肉粗灰分、血清谷草转氨酶活力、鳃Toll受体mRNA、NF-κBmRNA相对表达量显著升高(P0.05)。比较实用饲料组与半纯化饲料组的结果可知,罗氏沼虾对实用饲料中5%的大豆抗原蛋白有一定的耐受性,并且有利于其生长和健康,推测大豆抗原蛋白与豆粕中的其他抗营养因子间存在有益的联合效应,显著降低其中的大豆抗原蛋白含量则不利于蛋白合成代谢和肝胰腺健康,导致生长性能下降。建议在实际生产中发酵豆粕和豆粕按一定比例混合使用。     

壬基酚(NP)对罗氏沼虾幼虾生长和性别分化的影响

采用外部形态观察和性腺组织学连续切片方法,确定罗氏沼虾幼虾的性别分化时期,并探讨壬基酚(NP)对罗氏沼虾幼虾(体长约1.5 cm)生长和性别分化的影响。结果表明,罗氏沼虾仔虾后15 d出现生殖原基;仔虾后24 d,部分仔虾第四至第五步足基部明显凹陷,腹甲出现皱折和突起,并出现生殖管;仔虾后45 d,部分仔虾第二游泳足内侧出现雄性附肢,性腺明显区分为精巢和卵巢。处理时间短于15 d,NP对罗氏沼虾幼虾生长无显著影响;但处理超过20 d,NP以明显的剂量依存关系显著抑制罗氏沼虾体长和体重(P<0.05)。实验结束时(30 d),对照组个体均已完成性别分化,精巢和卵巢内分别出现大量精原细胞和卵原细胞,但NP处理组无法鉴定性别的幼虾比例随NP剂量增加而增加。研究表明,罗氏沼虾幼虾外部性征出现略早于内部性征的分化,早期性别分化发生在仔虾变态后21～45 d;此外,NP可能通过干扰蜕皮及卵黄蛋白原合成从而抑制罗氏沼虾幼虾生长和精巢发育。