Carbonic anhydrase and Na/K-ATPase activities during the molt cycle of low salinity-reared white shrimp <Emphasis Type="Italic">Litopenaeus vannamei</Emphasis>

Changes in hemolymph osmolality, ion concentrations, and enzymatic activities of carbonic anhydrase (CA) in the gills and epidermal tissue, and Na/K-ATPase in the gills during the molt cycle were investigated in the white shrimp Litopenaeus vannamei. Hemolymph osmolality was high in the intermolt and early premolt stages, but started to decrease prior to ecdysis through to postmolt stages A and B. Changes in Na⁺ and Cl⁻ ion concentrations paralleled those in hemolymph osmolality. CA activity levels in the anterior and posterior gills were low at intermolt stage C₀ and premolt stage D₀, and maximum at premolt stage D₃. In the epidermal tissue, activity was relatively high at intermolt stage C₀ and premolt stage D₀, but fluctuated towards premolt stage D₃ and postmolt stage A. On the other hand, Na/K-ATPase activity in the gills decreased between intermolt stage C₀ and premolt stage D₂, but increased at premolt stage D₃ and postmolt stage A. The changes in patterns of CA activity during the molt cycle suggest that CA may be involved in supplying counter-ions for Na⁺ and Cl⁻ uptake during molting. Branchial Na/K-ATPase appears to be involved in producing local osmotic gradients in order to support water influx across the epithelium.     

Practical Molt Staging of Penaeus setiferus and Penaeus stylirostris

Molt staging has many applications in penaeid aquaculture as a routine procedure. Using criteria developed for various crustaceans, a method of rapid molt staging was applied to Penaeus stylirostris and Penaeus setiferus adults. The most useful characters were the degree of epidermal retraction from the setal bases and epidermal retraction from the cuticle coupled with the development of new setae. The duration of the molt cycle of P. stylirostris was 11.5 ± 1.0 days ( N = 5) at 27–29 C. The early postmolt, late postmolt, intermolt, early premolt and late premolt stages were readily determined. For P. stylirostris , the duration of postmolt was 27% of the cycle; intermolt, 17%; and premolt, 56%. The length of the molt cycle of P. setiferus at 27–29 C was 13.6 ± 1.0 days ( N = 21) with postmolt occupying 22% of the cycle; intermolt, 19%; and premolt, 59%. Unilaterally eyestalk enucleated P. setiferus had a significantly shorter molt cycle than intact P. setiferus (11.7 ± 1.21 days vs. 13.6 ± 1.02 days, P < 0.05). There were no differences in molt cycle duration between the sexes, whether enucleated or intact ( P > 0.05). A series of illustrations identifies the key characteristics for determining stage of molt in these penaeids.     

Carbonic anhydrase and Na/K-ATPase activities at different molting stages of the giant freshwater prawn <Emphasis Type="Italic">Macrobrachium rosenbergii</Emphasis>

ABSTRACT:   In the present study, the role of carbonic anhydrase (CA) and Na/K-ATPase in the gill and epidermal tissues in the giant freshwater prawn Macrobrachium rosenbergii was examined as a function of molting stage. CA activity levels in the front and back gills were low at the intermolt stage C₀, but increased significantly at premolt stage D₃, and then decreased after molting. In the epidermal tissue, activity levels decreased gradually towards premolt to a minimum level at stage D₃, but became elevated at postmolt stages A and B. Na/K-ATPase levels in the front and back gills did not change significantly during the molt cycle. CA in the gill is possibly involved in supplying counter-ions for ion uptake, while CA in the epidermal tissue may play a role in mineralizing the exoskeleton after ecdysis. Na/K-ATPase in the gills may function in ion uptake from the ambient medium; however, since its activity was not influenced by the molt cycle, it probably does not have a major role in osmoregulation in the freshwater environment.     

中华绒螯蟹蜕皮周期中肝胰腺细胞组成的变化

取一年生未成熟中华绒螯蟹 (Eriocheir sinensis)幼蟹, 甲壳宽度在15~40 mm, 暂养在75 cm×50 cm×45 cm的玻璃缸内, 24 h充气, 自然光照, 每天换水1/3, 每次换水后投喂土豆、杂鱼等食物, 动物适应实验室条件1周后进行实验。为得到蜕皮后的样本, 将处于蜕皮前晚期的个体在相同条件下单独饲养。根据已报道方法, 将中华绒螯蟹的蜕皮周期分为蜕皮间期C期、蜕皮前D₀、D₁和D_3–4期、蜕皮后A-B期等5个时期。采用细胞学和组织学方法观察中华绒螯蟹蜕皮过程中肝胰腺细胞组成的变化, 结果显示, R细胞数量在蜕皮间期和蜕皮前期都占绝对优势, 虽然在蜕皮前早期D₀期数量显著下降(P<0.05), 但从D₁期开始上升, 于蜕皮前晚期D_3–4期达到最高(62.06 ± 3.92)%, 而在蜕皮后A-B期又显著降低(P<0.05)。F细胞的数量除在D₁期显著增加外(P<0.05), 其余时期的变化无统计学差异(P>0.05)。B细胞数量在蜕皮前早期D₀期显著增高(P<0.05), 随后开始下降, 直到蜕皮前晚期D_3–4期恢复到间期水平, 而蜕皮后A-B期数量又显著增高(P<0.05)。E细胞数量除在蜕皮前早期D₀期稍微上升外, 其余时期基本稳定(P>0.05)。饥饿对处于不同蜕皮时期的中华绒螯蟹肝胰腺细胞组成的影响不同, 饥饿48 h后, 处于D₀时期的中华绒螯蟹与正常组相比, 肝胰腺R细胞数量无显著变化, B细胞和E细胞数量显著下降, F细胞数量上升。处于D₁时期的中华绒螯蟹与正常组相比, 肝胰腺R细胞、B细胞、F细胞和E细胞数量均无显著变化。说明中华绒螯蟹蜕皮过程中肝胰腺细胞组成的变化和蜕皮周期密切相关。本研究通过探讨中华绒螯蟹蜕皮过程中肝胰腺组织结构及细胞组成变化, 了解甲壳动物蜕皮过程的基础生物学现象, 并为其健康养殖提供理论基础。

     

The molt stages and the hepatopancreas contents of lipids,glycogen and selected inorganic elements during the molt cycle of the Chinese mitten crab <Emphasis Type="Italic">Eriocheir sinensis</Emphasis>

A rapid molt-staging technique was developed for the Chinese mitten crab Eriocheir sinensis, with the aim of investigating selected molt-linked biochemical and inorganic factors in these animals. The results allow the identification of four distinct molting periods (postmolt, intermolt, premolt and ecdysis) and the further classification of the premolt period into three substages (D₀, D₁ and D_3-4). These findings are consistent with the classical scheme elaborated by Drach and Tchernigovtzeff (Vie Milieu 18:595–610, 1967). The contents of lipids, glycogen and several inorganic elements (Ca, Mg, Cu and Zn) in the hepatopancreas fluctuated and agreed well with their functions and with the molting stages during the molt cycle.     

中华绒螯蟹Y-器官在蜕皮周期中的超微结构

以光镜和电镜观察处于蜕皮周期不同阶段的中华绒螯蟹(Eriocheirsinensis),结果显示,中华绒螯蟹具Y-器官(YO)1对,卵圆形,直径1 5～2 0mm,苍黄色,位于头胸部鳃腔前端,大颚外侧内收肌腹缘,邻近头胸甲内侧上皮。YO细胞排列成索状,细胞索之间为血窦,YO的细胞索由一种细胞构成,细胞核质比高。YO细胞具有类似脊椎动物合成类固醇激素的典型超微结构特征,蜕皮前期YO细胞的光面内质网、管嵴状线粒体和游离核糖体丰富;蜕皮后期和蜕皮间期的内质网、线粒体和游离核糖体明显减少;青春蜕皮后的YO出现大面积细胞凋亡,YO趋向退化。     

中华绒螯蟹蜕皮周期及蜕皮过程中肝胰腺消化酶活性的变化

采用Darch蜕皮周期分期方法,对中华绒螯蟹(Eriocheir sinensis)的蜕皮周期进行了划分,并初步探讨了中华绒螯蟹蜕皮过程中肝胰腺消化酶活性变化。根据第三颚足末端刚毛和表皮的形态学特征,可将中华绒螯蟹的蜕皮周期分为蜕皮后期(A-B期)、蜕皮间期(C期)、蜕皮前期(D期)和蜕皮期(E期),其中D期可进一步分为D0、D1、D3-43个亚期。在蜕皮过程中,肝胰腺淀粉酶和胰蛋白酶活性在蜕皮后A-B期开始升高,于蜕皮前早期D0阶段达最大(P<0.05),随后又逐渐降低,至蜕皮前晚期D3-4阶段降至最低(P<0.05);胃蛋白酶活力在蜕皮周期中于蜕皮前晚期D3-4阶段显著降低(P<0.05),其他阶段变化不明显(P>0.05)。结论认为,中华绒螯蟹蜕皮过程可分为C、D0、D1、D3-4、A-B 5个时期,蜕皮过程中肝胰腺淀粉酶、胰蛋白酶和胃蛋白酶活性发生周期性变化。     

日本沼虾蜕皮过程中头胸甲外骨骼超微结构的改变

采用HE染色及石蜡切片的扫描电镜观察方法,描述了日本沼虾(Macrobrachium nipponense)蜕皮间期(C期,intermolt stage)及新旧表皮更替变化剧烈的蜕皮前晚期(D4期,late premolt stage)和蜕皮后期(postmolt stage)A-B期头胸甲外骨骼的形态结构变化特点。结果显示,日本沼虾外骨骼分为上表皮、外表皮、内表皮三层,D4期出现新的上表皮和外表皮,B期出现新内表皮,外表皮强嗜碱性而内表皮弱嗜酸性。扫描电镜观察发现,C期头胸甲内、外表皮均为几丁质-蛋白质纤维构成的平行板层结构且板层内有发达的孔道系统(pore canals,pc),但内外表皮板层间排列紧密程度不同,外表皮板层切面边缘较整齐,结构致密,板层内pc大小均一、近似圆形,内表皮板层切面边缘粗糙,结构较疏松,板层内pc大小不等、多为梭形。在蜕皮前后,新外表皮结构变化显著,与C期相比,D4期新外表皮超微结构与旧内表皮结构相似,而在A期,外表皮超微结构由疏松变为致密,这可能与蜕皮后表皮的钙化相关。本研究旨为阐明沼虾的蜕皮机制提供基础资料。     

Setal development and molt prediction in the larvae and adults of the crayfish,Astacus leptodactylus (Nordmann, 1842)

The criteria for determination, given by Drach (1939), have been adapted to divide the molt cycle into different stages for larvae and adults of the crayfish Astacus leptodactylus. The setal formation in the transparent appendages can be used for the definition of stages and substages in the premolt period. In order to evaluate the post-and intermolt stages in more detail, one can combine this method with changes occurring in the cuticle.     

蜕壳周期内中华绒螯蟹钙含量、组织结构及相关基因表达变化

运用生化分析、组织切片和分子生物学等技术,测定蜕壳期(蜕下旧壳后0.5 h内)和蜕壳后期(蜕下旧壳0.5 h后至新壳未完全硬化之前)平均体质量(5.63±2.35)g中华绒螯蟹肝胰腺和鳃中的钙含量,观察肝胰腺和鳃组织结构变化,用荧光定量PCR技术分析肝胰腺和鳃中的钙网蛋白(CRT)基因的表达情况.试验结果表明,蜕壳后期...     

KK-42对日本沼虾表皮蛋白基因MnCP-1表达的上调效应

为探讨KK-42显著缩短日本沼虾(Macrobrachium nipponense)蜕皮周期的可能机制,本研究采用RACE技术首次从头胸甲中获得了一个含几丁质结合-4(chitin_bind_4)结构域的表皮蛋白(cuticle proteins,CPs)c DNA基因全长,命名为Mn CP-1。该序列全长604 bp,可编码122个氨基酸。氨基酸序列比对显示,Mn CP-1与普通黄道蟹(Cancer pagurus,P81576.1)相似性最高(61%)。系统进化分析发现,Mn CP-1与地中海实蝇(Ceratitis capitata)聚类为一支。Real-time PCR结果显示,头胸甲中Mn CP-1在蜕皮前期晚期(D3-4期)和蜕皮后期(A期)的表达量较高,而在蜕皮间期(C期)和蜕皮前期早期(D0-2期)的表达量较低。KK-42处理能显著上调C期和D0-2期Mn CP-1的表达,在处理后6、24和48 h,其mRNA表达水平较对照组高3倍以上。结果表明,头胸甲上皮细胞Mn CP-1的表达与蜕皮周期有关,KK-42可显著上调C期和D0-2期Mn CP-1的表达。     

Oxytetracycline (OTC) accumulation and elimination in hemolymph, muscle and hepatopancreas of white shrimp Litopenaeus vannamei following an OTC-feed therapeutic treatment

The white shrimp, Litopenaeus vannamei, has become a very important species for the development of shrimp aquaculture in Northwest Mexico. However, viral and bacterial diseases are considered a major threat to the development of this industry. In the present study a trial was conducted to evaluate the tissue distribution, maximum concentration, and elimination of the widely used antibiotic oxytetracycline (OTC) in L. vannamei using indoor tanks under laboratory-controlled conditions. OTC was given to shrimp simulating a therapeutic treatment through medicated feed for 14 days followed by a period of feeding without antibiotic for another 14 days to evaluate the elimination pattern. Samples of hemolymph, muscle, and hepatopancreas were taken from medicated animals every two days for 28 days. All tissues were removed and frozen immediately in liquid nitrogen. OTC levels were analyzed by High Performance Liquid Chromatography (HPLC). Results showed an important OTC increase during consumption of medicated feed in all examined tissues. OTC maximum concentrations were 33.54 ± 11.19, 194.37 ± 16.11, and 18.79 ± 5.87 µg g^− 1 for muscle, hepatopancreas and hemolymph, respectively. Although the highest OTC level was found in the hepatopancreas, it required only two days after the start of dosing to reach this value, whereas the maximum OTC for muscle and hemolymph was detected after eight days of dosing. Ten days after the cessation of medicated feeding, the drug content in the shrimp tail muscle was under the detectable limit for the method (0.01 µg g^− 1 of OTC).     

First feeding of Octopus vulgaris Cuvier, 1797 paralarvae using Artemia: Effect of prey size, prey density and feeding frequency

Different assays related to the first feeding of Octopus vulgaris Cuvier, 1797 are compiled in this paper. They include: age at initial feeding age, prey size selection and optimal density, attack timing after feeding, and effect of dose number on the number of captures. Prey capture and ingestion processes were also analysed. Food supplied was cultured Artemia sp. Each assay lasted 15 min.Although paralarvae already start to feed on the hatching day (day 0), it is during day 2 when a greater number of attacks is recorded (81.7 ± 14.7% paralarvae attack). They mainly prefer (significance level α = 0.05) large Artemia, 1.4 ± 0.4 mm (77.0 ± 5.6% of the total attacks) than small Artemia, 0.8 ± 0.1 mm (23.0 ± 5.6%). There is also a slight predilection for the lowest Artemia concentration (33.3 ±12.6% paralarvae attack in a 0.1 Artemia ml^− 1 density, opposite 16.7 ± 7.6 and 18.3 ± 7.6% in densities of 0.5 and 1 Artemia ml^− 1 respectively). The greatest predatory activity is recorded during the first 5 min after food is supplied (72.2 ± 25.5%). An increase in the predatory activity was also observed when food was distributed in several doses instead of a single dose (75.0 ± 10.0% and 46.7 ± 17.6% respectively). It was proved for the first time that paralarvae completely ingest their preys (including their exoskeletons), in this case Artemia. Time needed for their total ingestion ranges between 4 and 10 min.     

Activity of digestive enzymes along the gut of juvenile red abalone, Haliotis rufescens, fed natural and balanced diets

Two carbohydrases (cellulase, lysozyme), three proteases (trypsin, aminopeptidase and non-specific protease), a non-specific lipase, and semiquantitative tests of 19 digestive enzymes were assayed in different gut sections of juvenile red abalone, Haliotis rufescens, in order to identify the regions where digestion takes place and investigate the extent to which diet composition can modify the digestive capacity of abalone. The abalone were fed either fresh kelp (K) or balanced diets containing 25 or 38% crude protein for 6 months. Enzyme assays were carried out on different sections of the abalone's gut at the end of this period. On a weight-specific basis, the digestive gland was the site containing most of the enzymes. On a protein-specific basis, two main digestion regions were identified: the digestive gland-stomach region that is characterized by high activities of cellulase and lysozyme, chymotrypsin and protease, and the mouth-intestine region with a typically high activity of lipase and amino peptidase. Significant dietary effects were observed on the activity of enzymes, especially in the digestive gland. Abalone fed with 25 and 38% crude protein diets exhibited higher cellulase (39.8 ± 4.6 and 14.2 ± 0.8 mU mg^− 1 protein, respectively) and lysozyme activities (88.0 ± 20.4 and 56.6 ± 15.7 U, respectively) than those fed with fresh kelp (5.5 ± 0.7 mU mg^− 1 protein and 17.1 ± 1.8 U). In contrast, higher protease activity was found in kelp-fed organisms (234.1 ± 20.4 μg product/mg protein) than those fed the 25 and 38% crude protein diets (109.5 ± 20.7 and 119.5 ± 20.5 μg product/mg protein, respectively). Semiquantitative API ZYM assays resulted in no clear food-specific effects on the activity of carbohydrases, proteases, ester hydrolases or phosphohydrolases, yet organ-specific differences were conspicuous in various cases, and generally agreed with quantitative results. It is suggested that the increased carbohydrase activity exhibited by organisms fed the balanced diets resulted from a combination of an increased number of resident bacteria in the abalone's gut and facilitated contact between dietary substrates and digestive cells. The present results indicate that H. rufescens can adjust their enzyme levels in order to maximize the acquisition of dietary protein and carbohydrates. This characteristic can be advantageously used to search for suitable diets in abalone aquaculture.     

Influence of dietary soybean meal levels on growth, feed utilization and gut histology of Egyptian sole (Solea aegyptiaca) juveniles

The present study was undertaken in order to determine the effect of a dietary incorporation of soybean meal (SBM) on growth performance, nutrient utilization and gut histology of Egyptian sole Solea aegyptiaca. This species, which is genetically and morphologically close to Solea solea, is currently present in the Mediterranean Sea and reared in some Italian farms, using the same techniques for S. solea production and it could represent a promising new species for Mediterranean aquaculture.Three isoproteic and isolipidic extruded diets (crude protein, 47%, crude fat, 20%) were formulated containing 0 (diet 1), 18 (diet 2) and 30% SBM (diet 3). 540 juveniles (initial body weight of 6.9 ± 0.2 g) were equally distributed into nine 150 l squared tanks (bottom surface: 520 cm²) connected with a recirculation system (temperature 20 ± 1 °C and dissolved oxygen above 6 ppm). Animals have been hand-fed twice a day (at 9.00 a.m. and 5.00 p.m.) at a daily ratio of 1.5% body weight^− 1. Diets were tested in triplicate for 87 days. The fish were weighed at days 28, 57 and 87, and they were sampled at days 0, 57 and 87 for nutrient retention determination. One-way ANOVA with Newman-Keuls' post-test were used to analyze data (P ≤ 0.05).No differences in terms of palatability were observed and any diet has been consumed completely all throughout the experiment. At day 87, fish fed diet 1, 2 and 3 reached weights of 25.8 ± 0.8 g, 27.5 ± 0.9 g and 26.1 ± 1.5 g, respectively and no differences in performances or nutrient retention were found.Histopathological gut examinations have revealed no noticeable differences in the appearances of the intestines between any of diet groups. Intestinal mucosal cells presented well vacuolated upper, with well defined microvillar brush borders. On the basis of the results of this trial, SBM seems to be a good protein source for Egyptian sole and can be added in the diet up to 30% without any reduction in growth rate and no adverse effect on gut histology.     

The effects of supplemental dietary cholesterol on growth, development and survival of mud crab, Scylla serrata, megalopa fed semi-purified diets

The effects of varying levels of dietary cholesterol on growth, development time and survival of mud crab, Scylla serrata megalopa were investigated using semi-purified microbound diets (MBD). Five iso-energetic diets containing different level of cholesterol ranging from 0.14% to 1% of dry weight of the diet were tested. Fifteen megalopa were reared individually for each dietary treatment, and development time and survival were recorded on a daily basis. More than 25% of megalopa from all treatments were able to metamorphose into the first crab stage, suggesting that the endogenous level of cholesterol in the basal diet (0.14%) was sufficient to support development of the megalopa stage of this species. Widest mean carapace width (3.53 ± 0.08 mm) and highest mean dry weight (2.11 ± 0.22 mg) were recorded for juveniles that molted from megalopa fed live Artemia, whereas no megalopa in the unfed control treatment metamorphosed into crabs. The average development time from megalopa to the juvenile crab stage varied between the treatments, where megalopa fed live Artemia or MBD containing 0.2%, 0.4% or 0.8% total cholesterol showed the most synchronized molting (between 8.0 and 9.9 days). Longest development time was recorded for the megalopa fed diets containing 0.14% or 1% total cholesterol (both 11 days). Highest survival (74.3%) was recorded for the megalopa fed a diet containing 0.8% cholesterol. The results of this study are valuable in research to develop formulated diets for mud crab larvae as a replacement for live food in hatchery culture.     

Suspension of annual gametogenesis in North American green sea urchins (Strongylocentrotus droebachiensis) experiencing invariant photoperiod—Applications for land-based aquaculture

Sea urchin fisheries are valuable commercial resources in the United States with processed gonads sold in Japanese and American markets and maximum US sales of $150M US dollars in 1996. Wild populations of sea urchins on all coasts of the US have been dramatically over-fished. Aquaculture of sea urchins in land-based facilities can help restore commercial populations and preserve this ecologically important herbivore. In this study, we used invariant summer photoperiod to prevent gametogenesis in the North American green sea urchin (Strongylocentrotus droebachiensis) maintained in a land-based aquaculture system and provided a commercially available formulated feed that promotes maximum growth of intra-gonadal somatic nutrient storage cells called nutritive phagocytes. Results were compared with individuals fed the same formulated feed under ambient photoperiod in cages in the ocean. Monthly samples of gonads from both treatments were evaluated for gonad index, volume fractions of cellular constituents of the germinal epithelium, oocyte diameters and taste. Over the 5 months of this study, gonad indices increased significantly (p < 0.001) in both treatments from 4.8% ± 0.9 (all values ± SE) initially to 20.5% ± 2.1 under invariant and 23.2% ± 1.4 under ambient photoperiod with no significant difference between treatments (p = 0.55). Volume fractions of nutritive phagocytes increased to 80.3% ± 5.9 (initial 37.9% ± 7.1) in males and 71.0% ± 6.7 (initial 10.3% ± 4.0) in females (p < 0.001) only under invariant photoperiod. Nutritive phagocyte lengths increased under both photoperiod treatments, but the volume fraction containing nutrients was higher under invariant photoperiod. Volume fractions of gonial/gametogenic cells increased significantly (p < 0.001) only under ambient photoperiod from 20.4% ± 5.5 to 37.8% ± 1.8 in males and 0% to 22.6% ± 3.6 in females. The volume fraction of residual oocytes from last year's oogenesis increased under invariant photoperiod while that of both residual and new oocytes increased under ambient photoperiod. Residual oocyte diameters increased from 56.2 μm ± 2.2 initially to 93.5 μm ± 3.7 under invariant and those of residual and new oocytes to 126.0 μm ± 7.3 under ambient photoperiod. Invariant photoperiod yields gonads in both sexes of S. droebachiensis that do not initiate fall gametogenesis but attain large size as their nutritive phagocytes grow substantially in size. A Canadian study of wild-collected S. droebachiensis indicated that gonads taste best when they contain pre-dominantly nutritive phagocytes and not copious gametes, however gonad taste in our study was unsatisfactory suggesting that the only commercially available sea urchin diet requires modification to support commercial development of land-based aquaculture.     

Performance of different types of diets on experimental larval rearing of endangered Chitala chitala (Hamilton) in recirculatory system

This is the first report on the successful larval rearing of captive bred population of Chitala chitala (Hamilton). C. chitala is one of the endangered fresh water fish species in India for which the development of controlled larval rearing procedures are needed for stock enhancement. Fifteen days old post-hatchlings were stocked for 28 d in a 30 L recirculatory tanks using eight different diets i.e. live feed (tubifex worms, chironomous larvae, zooplanktons,), dry feed (dry tubifex, spirulina, daphnia) and other non-conventional feed (fish eggs and boiled egg-yolk). Fishes accepted all types of diets. The study revealed that specific growth rate (SGR) was higher in post-hatchlings fed on live tubifex worms (2.40 ± 0.72) followed by fish eggs (2.15 ± 0.71), dry tubifex (2.12 ± 0.40), chironomous larvae (1.91 ± 0.44), spirulina (1.79 ± 0.38), daphnia (1.42 ± 0.79) and planktons (1.37 ± 0.77) whereas minimum SGR was recorded with boiled egg-yolk (0.63 ± 0.5). A highly significant difference (p < 0.01) in SGR was observed in fish fed on live feed (tubifex worms, chironomous larvae, planktons, spirulina), dry tubifex and fish eggs whereas for daphnia and boiled egg-yolk it was only significant (p < 0.05). The final mean weight and weight gain showed highly significant difference (p < 0.01) in live tubifex, zooplanktons, spirulina, chironomous larvae, dry tubifex and fish eggs, whereas daphnia and boiled egg-yolk fed larvae showed significant difference (p < 0.05). Highest mean survival rate on day 28 was observed in live tubifex worms (94%) and chironomous larvae (92%). The post-hatchlings reared with spirulina and daphnia showed same survival rate of 88% whereas the lowest mean survival of 66% was recorded in boiled egg-yolk. The experiments showed that captive bred post-hatchlings of C.chitala could be reared in experimental recirculatory system for attaining higher growth and survival during early life stages. However, methods to improve the larval rearing have to be improved further for commercial farming of the species.     

The effects of fish hydrolysate (CPSP) level on Octopus maya (Voss and Solis) diet: Digestive enzyme activity, blood metabolites, and energy balance

As has been demonstrated in previous studies, Octopus maya can be fed on artificial diets. In the present study six different diets were assayed. Five diets were designed to test the effect of percentage of inclusion of fish protein concentrate (CPSP: 0, 5, 10, 15, and 20%) and were offered to octopuses as a specifically designed artificial diet. The sixth diet consisted of frozen crab (Callinectes spp) and was used as control diet. Blood metabolites and energy budget of octopuses were evaluated to determine how CPSP levels modulate the digestive capacity and allow retaining energy for growth. Wild animals (316.4 ± 9.8 g) were used in the study. Results showed that CPSP produced a positive specific growth rate (SGR, % day^− 1) with high value in octopuses fed 15% CPSP level. A maximum growth rate of 0.86% day^− 1 was recorded in these animals, a value that is extremely low when compared with the SGR obtained when animals were fed fresh crab (3.7% day^− 1). In general, blood metabolites were affected by diet composition, indicating that some metabolites could reflect the nutritional and/or physiological status of octopus. Preliminary reference values for O. maya fed crab were found for glucose (0.09 ±0.02 mg/ml), lactate (0.004 ± 0.002 mg/ml), cholesterol (0.16 ± 0.02 mg/ml), acylglycerol (0.14 ± 0.01 mg/ml), protein (0.37 ± 0.04 mg/ml), hemocyanin (1.85 ± 0.04 mmol/l), and digestive gland glycogen (1.86 ± 0.3 mg/g). Total energy content can be used as an indicator of tissue metabolic reserves. In the present study, higher energy content in the digestive gland and muscle was observed in octopuses fed crab, followed by animals fed 15% CPSP. Results from the digestive gland indicated that the retained energy derived from glycogen, suggesting that lipids and protein were the main sources of variation linked with energy content. In general, digestive gland proteases activity and trypsin were induced in octopuses fed 15% CPSP. The capacity of O. maya juveniles to adjust their digestive enzymes to different types of food was evidenced. Essential amino acid content (EAA) of the diet was not a limiting factor. When dietary EAA profiles were compared with O. maya EAA profiles, all dietary EAA resulted in a higher concentration than whole body octopus composition. In the present study, all experimental groups ingested between 3300 and 4106 kJ wk^− 1 kg^− 1 without statistical differences among treatments, indicating that experimental diets were as attractive as crab. Differences were recorded in the proportion of absorbed energy (Ab, %) between CPSP-based and crab meat diets, suggesting digestion limitations associated with artificial diets. The present results indicate that the 15% CPSP diet had characteristics that stimulate digestive enzymes and reduce energetic costs associated with its digestion (HiE or SDA), channeling more biomass production than the other experimental diets.