Induction of fertilizable eggs by conspecific vitellogenin implantation in captive female walking catfish,Clarias batrachus (Linn.)

The synthesis of vitellogenin (Vg) is induced by conspecific Vg (Vg1 and Vg2) and estradiol‐17β (E₂) as demonstrated by the pattern of ³H‐serine incorporation in the liver and plasma proteins. The incorporation studies indicated that the label was first incorporated into the liver after which it appeared in the blood in both E₂‐ and Vg‐treated male catfish. Since Vg was capable of inducing its own synthesis, experiments were conducted in females during preparatory–prespawning period (March–May) to make them gravid by implanting Vg pellets. Two implantations of 4 mg Vg1 pellets into female catfish with an interval of 15 days, followed by laboratory maintenance for 45 days of initial implantation showed a significant increment in ovarian weight with concomitant formation of yolky oocytes through synthesis and incorporation of Vg, whereas Vg2 implantation was not effective in this regard. Histological observation of yolky oocytes in Vg1‐treated group showed the peripheral migration of germinal vesicle (eccentric germinal vesicle), which indicates the onset of maturation. On 45th day, third implantation with 2 mg Vg pellets was performed and after 15 days, fish were hormonally induced with a single injection of hCG (2,000 IU/kg fish). Six groups were considered such as initial control, BSA‐implanted control, Vg1‐implanted, Vg2‐implanted, catfish collected from the field on the last day of the experiment and catfish collected during spawning period in this experiment with 3–7 fish in each group. Each of the experimental fish was sexually mature and the body weight was between 100 and 125 g. The percentage of ovulation and fertilization in the eggs of Vg1‐implanted group was 91% and 78%, respectively, which was almost similar to that of gravid female catfish collected during breeding period (July). The breeding performance in BSA‐ and Vg2‐treated females was very poor. The fertilized eggs were hatched in the laboratory conditions. Thus, in the female catfish, Vg1 not only induces vitellogenesis but also makes the oocytes viable for fertilization.     

Purification and partial characterization of GtHs (cfLH and cfFSH) from Indian walking catfish (Clarias batrachus) (L.) and development of a homologous ELISA for cfLH

Two gonadotropins (GtH; Qa and Qb) were purified by gel filtration and ion exchange chromatography from the pituitaries of Indian walking catfish (Clarias batrachus). The presence of GtH during purification was assessed by in vitro oocyte maturation and in vivo steroidogenic activity, and their identities were determined by elution profiles, molecular weight, biological activities and yield. The molecular weights of Qa and Qb were 37 and 42 kDa, respectively, and composed of distinct subunits (Qa: 20 and 14 kDa and Qb: 26 and 18 kDa). Polyclonal antibodies raised against Qa immunostained Qa, Qb and pituitary GtH cells. A competitive Qa‐ELISA was developed whose sensitivity was 6.25 ng mL^?1 (1.25 ng well^?1) with intra‐ (3.5%) and inter‐ (12.4%) assay coefficients of variation. Displacement curves parallel to the standard were obtained with plasma and pituitary extracts of catfish, Qb and carp GtHII. The assay was validated by measuring the plasma Qa levels after LHRH treatment and in relation to ovarian growth in the female catfish during different reproductive phases. Based on the results, Qa and Qb corresponded to fish LH and FSH respectively. The findings will increase the knowledge of the mechanisms controlling fish reproduction and identification of sensitive phases in fish in captivity for hormonal manipulation.     

Dietary beta-1,3 glucan potentiates innate immunity and disease resistance of Asian catfish, Clarias batrachus (L.)

This study investigated the effects of short and prolonged administration of a yeast beta-glucan on non-specific immune parameters, growth rate and the disease resistance of Asian catfish, Clarias batrachus. Fish fed with a basal diet (control) and test diet (basal diet supplemented with 0.1% glucan) for 1, 2 and 3 weeks were assayed for superoxide production, serum myeloperoxidase (MPO) content, natural haemagglutinin level, complement and lysozyme activities. Fish were weighed at weekly intervals and specific growth rate (SGR, % increase in body weight per day) was determined. After each week, fish were challenged with Aeromonas hydrophila to measure the level of protection. Results showed that glucan administration at 0.1% in feed, significantly (P<0.05) enhanced MPO and lysozyme levels, superoxide production, haemagglutination titre and level of protection against A. hydrophila challenge, irrespective of length of exposure. The alternative complement activity and SGR were not affected by the dietary supplementation of yeast glucan. As glucan feeding at 0.1% for 1 week is able to enhance the non-specific immunity and disease resistance of catfish efficiently, short-term feeding might be used in farmed catfish diets to enhance disease resistance.     

Induced spawning of maturing Indian catfish, Clarias batrachus (L.), using low doses of steroid hormones and salmon gonadotropin

Abstract. Effects of low doses of salmon gonadotropin (SG-G100) and three steroids — 17α,20β-dihydroxyprogesterone (17α,20β-diOHprog), deoxycorticosterone (DOC) and progesterone — individually, or combinations of steroid with SG-G100, on ovulation and hatching in Clarias batrachus (L.) were investigated. None of the steroids at any of the three different dose levels (1μg, 1·5μg/g and 2μg/g BW) could induce ovulation when injected alone. SG-G100 at a dose level of 10 μg/g BW was not effective but at the dose level of 15 μg/g BW it could induce ovulation. All the three steroids at their lowest doses (1μg/g BW) when injected in combination with SG-G100 (10μg/g BW) were significantly effective in inducing ovulation. When hatching percentage was taken into account, 17α,20β-diOHprog in combination with SG-G100 was found to be the most effective combination in comparison with other treatments.     

Ontogeny and development of the gastrointestinal system in Indian walking catfish (Clarias magur) during its early development

Fish Physiology and Biochemistry - Ontogeny of the digestive tract and its accessory organs and their further development in the Indian walking catfish (Clarias magur) were examined in larvae,...     

Identification and characterization of maturation-promoting factor from catfish,Clarias batrachus

Maturation-promoting factor (MPF) extracted from maturing oocytes of catfishes (Clarias batrachus andHeteropneustes fossilis) and carp (Labeo rohita) induces 100% germinal vesicle breakdown (GVBD) when microinjected intoClarias immature unstimulated oocytes. The presence of a similar MPF activity has also been demonstrated in the active fractions collected after superose 12. SDS-PAGE analyses of cytosolic extracts (CE) prepared from immature and mature oocytes revealed the presence of 34- and 46 kDa proteins apart from a few others. Antibody against the PSTAIR sequence of p34^cdc2 recognized 32- and 34 kDa proteins of immature as well as mature oocytes while, 46 kDa protein of mature oocytes was recognized by anti-cyclin B1 antibody. Moreover, labelling of [³⁵S]methionine was observed mainly in the region of 46 kDa protein band indicatingde novo synthesis of this particular protein. Anti-cyclin A antibody did not recognize any proteins of immature or mature oocytes. Cyclin B1 was absent in immature oocytes and ovulated eggs. These findings indicate the presence of p34^cdc2 homologs and cyclin B in the MPF of the catfishes and carp oocytes.     

Quantifying the dietary biotin requirement of the catfish,Clarias batrachus

Asian catfish, Clarias batrachus, were fed semi-purified basaldiets containing 0, 0.1, 0.5, 1, 3 and 5 mg biotin kg^–1diet for 60 days. Fish fed the control diet (no biotin) showed(P < 0.05) higher mortality, lower weight gain, specificgrowth rate (SGR), feed efficiency ratio (FER) and protein efficiencyratio (PER) than in fish fed diets supplemented with biotin. The highestweight gain, SGR, FER and PER were noticed in fish fed 1 mg biotinkg^–1, followed by 0.5, 5, 3 and 0.1 mg biotinkg^–1, except for PER (followed by 0.5, 5, 0.1 and 3 mgbiotin kg^–1). Quadratic analysis showed that the optimumdietary biotin requirements for maximal weight gain, PER and PER were2.49, 2.54 and 2.52 mg kg^–1, respectively. Liver biotinconcentrations were influenced by levels of biotin in the diet.Concentration of liver biotin increased as level of dietarysupplementation increased and no biotin was detected in the liver of thecontrol fish. Liver pyruvate carboxylase and acetyl CoA carboxylaseactivities were higher in fish fed biotin-supplemented diets than incontrols. Biotin concentrations, pyruvate carboxylase and acetyl CoAcarboxylase activities in liver associated with normal growth rangedfrom 10.59 to 10.66 g g^–1, 147.97 to 148.18 units mgprotein^–1 and 12.76 to 12.78 units mg protein^–1, respectively. Biotin deficiency symptoms such as anorexia, darkskin colour and convulsions were observed in fish fed the control diet.The optimum dietary biotin requirement for maximal growth of C.batrachus is about 2.49 mg kg^–1 diet.     

Dietary levamisole modulates the immune response and disease resistance of Asian catfish Clarias batrachus (Linnaeus)

In order to determine the immunomodulatory effect of dietary levamisole in Asian catfish (Clarias batrachus), fish were fed four different diets for 10 days: a formulated diet as control and the same diet supplemented with 50, 150 or 450 mg levamisole kg^?1 feed. The serum bacterial agglutination titre against Aeromonas hydrophila as a measure of specific immunity, serum haemagglutination titre, natural haemolytic complement activity (ACH₅₀), myeloperoxidase and lysozyme activities, total protein level and oxidative radical production by neutrophils as a measure of non‐specific immunity as well as disease resistance against A. hydrophila challenge to separate vaccinated and non‐vaccinated groups were evaluated at 0, 1, 2 and 3 weeks after last administration of levamisole. Levamisole supplement at the lowest level (50 mg kg^?1) significantly enhanced oxidative radical production and serum myeloperoxidase (MPO) content immediately after 10 days of feeding, which reached peak values after 3 and 2 weeks of feeding respectively. Haemolytic complement and haemagglutination titre were significantly enhanced after 3 and 1 weeks respectively. Haemolytic complement activity and MPO activities were significantly raised to 150 mg kg^?1 after 3 and 2 weeks, respectively. At the highest level of levamisole feeding (450 mg kg^?1) significant decreases in superoxide production and complement activity were measured immediately after levamisole feeding, which returned to the normal level after 1 week post‐ feeding. Fish were challenged with a virulent strain of A. hydrophila at 0, 1, 2 and 3 weeks after levamisole feeding, and the cumulative per cent survival was recorded over 10 days. Feeding levamisole at 50, 150 or 450 mg kg^?1 increased per cent survival in vaccinated fish immediately after levamisole feeding, and survival was significantly higher at 450 mg kg^?1. There was no difference in mortality patterns in non‐vaccinated fish. The results support the use of levamisole at 50 mg kg^?1 feed for 10 days as an immunostimulant in Asian catfish farming.     

Optimum feeding rate, and energy and protein maintenance requirements of young Clarias batrachus (L.), a cultivable catfish species

Abstract. Protein and energy maintenance and optimum feed requirements are reported in the catfish, Clarias batrachus (L.), fed a purified diet (40% CP; 1487·1kJ/100g) at 0 to 8% (BW/day) ration levels. Linear (r = 0·985) increase was observed in daily average growth increment up to a ration level of 4% (BW/day), corresponding to 6·03g protein/(kg^0·8BW/day) and 224·26 kJ energy/(kg^0·8 BW/day). Maintenance requirements, obtained by regressing daily average growth increment to zero, were 0·942 g/(kg^0·8 BW/day) for protein and 36·02 kJ/(kg^0·8BW/day) for energy. Net gains in muscle protein and energy also depicted linear increase (r = 0·975) with feeding levels up to 6·03g protein/(kg^0·8 BW/day) and 224·26kJ energy/(kg^0·8 BW/day). On fitting the above data to regression equations, giving the amount of dietary protein and energy required to maintain a constant amount of body protein and energy, values of 1·005g/(kg^0·8 BW/day) and 42·11 kJ/(kg^0·8BW/day) were obtained for protein and energy respectively. The optimum feeding rate for this species, as evident from specific growth rate and conversion efficiencies, appears to be 3% (BW/day) at 30 ± 2°C. Moisture and lipid contents in muscle were found to be significantly ( P < 0·05) affected by the ration levels.     

Purification and development of ELISAs for two forms of vitellogenin in Indian walking catfish, <Emphasis Type="Italic">Clarias batrachus</Emphasis> (L.)

Two forms of vitellogenin (Vg: Vg1 and Vg2) were purified from the plasma of estradiol-17β (E₂)-treated Indian walking catfish, Clarias batrachus, by gel filtration and adsorption chromatography. Native Vg1 and Vg2 had apparent molecular masses of 375 and 450 kDa, respectively, and both Vgs resolved into two similar major bands (95 and 67 kDa) in SDS-PAGE under reducing condition. Polyclonal antisera raised against each form of Vg were absorbed with a combination of hypophysectomized male catfish serum proteins and alternate Vg to ensure specificity. Immunological analyses verified the presence of Vg1 and Vg2 in the plasma of female catfish. Homologous ELISAs were developed for Vg1 and Vg2 using their respective harvested antisera, which exhibited the detection limit of 100 ng ml^?1 for Vg1 and 40 ng ml^?1 for Vg2, and low level of cross-reactivity (not parallel to the standard) was found with alternate Vg in each assay. Treatment of male catfish with E₂ induced both Vgs showing a proportionate ratio of Vg1 to Vg2 at 5.6:1. Plasma concentrations of both Vgs measured by ELISAs at different reproductive phases of field collected female catfish increased in accordance with the ovarian development, keeping the proportionate ratio of Vg1 to Vg2 at about 2:1 in fish undergoing vitellogenesis during prespawning period and 1:20 during spawning period, suggesting that Vg1 may be the major Vg to contribute in yolk formation, whereas Vg2, besides its role in yolk formation, may facilitate other physiological functions. The present study, thus, demonstrates the occurrence of two unequally synthesized Vgs in the catfish.     

革胡子鲶出血性败血症病原菌的分离鉴定

从暴发性死亡的革胡子鲶(Clarias gariepinus)中分离出可疑病原菌株2010111403(简称1403),分别采用细菌全细胞脂肪酸鉴定系统、Biolog微生物自动鉴定系统及细菌16 S rDNA序列分析三种方法对其鉴定,结果表明菌株1403为嗜水气单胞菌(Aeromonas hydrophila)。分离菌株对健康革胡子鲶致病性测试表明其对革胡子鲶的半数致死剂量(LD50)为6.32×106菌落形成单位(CFU);实验感染革胡子鲶出现与自然发病相似症状,表明菌株1403是引起革胡子鲶发生暴发性死亡的主要致病病原。药敏试验表明,庆大霉素、四环素、阿奇霉素、氟哌酸、先锋霉素等9种抗生素对分离菌株有较强的抑制作用,但分离菌株对复方新诺明、克林霉素、罗红霉素等4种药物表现出耐药性。     

Stimulation of ureogenesis in the perfused liver of an Indian air-breathing catfish, Clarias batrachus, infused with different concentrations of ammonium chloride

The pattern of changes of activity of the urea cycle enzymes and the rate of urea-N excretion were studied in the perfused liver of an Indian air-breathing ureogenic walking catfish, Clarias batrachus. The liver was perfused with different concentrations of NH₄Cl for a period of 60 min to determine the role of ammonia for stimulation of hepatic ureogenesis and the threshold level of ammonia loading needed to cause such stimulation. Both the urea-N excretion and the ammonia uptake by the perfused liver were found to be a saturable process. Ammonia accumulated significantly in the liver infused with 1.25 moles g liver ^–1 min^–1 of NH₄Cl, followed by a maximum accumulation of about 28.5 moles g wet wt^–1 with the infusion of 5.08 moles g liver^–1 min^–1. The Vmax of the urea-N excretion (0.47 mol g liver^–1 min^–1) was obtained with the addition of 5.08 moles g liver^–1 min^–1 of NH₄Cl. Both the tissue and the specific activity of the urea cycle enzymes, except ornithine transcarbamylase and arginase, were stimulated significantly with the infusion of either 1.25 or 5.08 moles g liver^–1 min^–1 of NH₄Cl. Maximum stimulation of tissue activity of carbamoyl phosphate synthetase (about 120%) was seen with the infusion of 5.08 mol g liver^–1 min^–1, and for argininosuccinate synthetase (about 135%), and argininosuccinate lyase (about 50%) with the infusion of 10.81 mol g liver^–1 min^–1 of NH₄Cl. Higher accumulation of ammonia of about 10–15 mol g wet wt^–1 from the physiological level in the perfused liver while infusing with NH₄Cl was suggested to be one of the major causes of stimulation of ureogenesis. The presence of such physiological adaptive strategy is probably necessary in this unique group of air-breathing walking catfish to survive under hyper-ammonia stress in their normal habitat or while living outside water or while burrowing inside mud.     

Dietary available phosphorus requirement of juvenile walking catfish,Clarias leather

A feeding trial was conducted to evaluate the optimum requirement of dietary available phosphorus (AP) for juvenile walking catfish, Clarias leather. Six practical diets were formulated to contain graded levels (2.2, 3.9, 5.5, 7.1, 8.8 and 10.4 g kg^?1) of AP from dietary ingredients and monocalcium phosphate. Each diet was randomly fed to triplicate groups of fish with initial mean weight of 7.94 ± 0.08 g in floating cages (1.5 × 1.5 × 2.0 m) suspended in an earthen pond, and each cage was stocked initially with 60 fish. Fish were fed thrice daily (07:30, 13:00 and 17:30) to apparent satiation for 10 weeks. Both specific growth rate (SGR) and protein efficiency ratio significantly increased with increasing AP from 2.2 to 5.5 g kg^?1 (P < 0.05) and then levelled off. Dietary AP levels significantly influenced whole‐body protein, lipid and ash contents as well as condition factor and hepatosomatic index (P < 0.05). Whole‐body and vertebrae phosphorus contents showed similar patterns as SGR in response to dietary AP content. Broken‐line analyses based on SGR, phosphorus contents in the vertebrae and whole‐body indicated the AP requirements were 5.8, 7.2 and 7.5 g kg^?1, respectively.     

Growth, feed utilization and carcass composition of catfish Clarias batrachus (Linn.) fingerlings fed on dried fish and chicken viscera incorporated diets

A 30‐day feeding trial was conducted to evaluate dried fish and chicken viscera, and a combination of oil cakes as complete substitutes for fish meal in the diet of catfsh Clarias batrachus (Linn.) fingerlings. Triplicate groups of fingerlings with a mean initial body weight of 2.0 g were each fed four isonitrogenous diets at 4% of wet body weight. Performance of the diets was judged on the basis of feed acceptability, body weight gain, feed conversion ratio and protein efficiency ratio. A significant increase (P < 0.05) in body weight gain, protein efficiency ratio and a decreased feed conversion ratio (P < 0.05) was observed in fish fed on fish meal, followed by fish viscera, chicken viscera and only plant protein incorporated diets. Although inferior to fish meal and dried fish viscera, growth and feed utilization responses of fingerlings fed on dried chicken viscera and plant protein diets were similar. The fish accumulated a significantly greater (P < 0.05) amount of fat (18.3%) in the body carcass when fish viscera was incorporated in the diet. The study revealed that satisfactory growth and feed utilization responses could be achieved through replacement of fish meal by dried fish and chicken viscera in the diet of catfish fingerlings.     

Controlled propagation of the African catfish,Clarias lazera (C. & V.): II. Artificial reproduction

To optimize the artificial reproduction of C. lazera for aquaculture, experiments were carried out on short-term sperm conservation as well as hypophysation and stripping of the females.When the sperms were stored at 5°C for 24 h, their fertilizing capability was reduced by 4% compared with freshly obtained sperm. However, dilution in a 0.9% naCl solution (up to 10^?3) gave an average 9% increase of hatching success. This finding enables the use of one competent male to fertilize the eggs of many females. An alternative application of the finding enables homoplastic hypophysation, using the fresh pituitary of the male to induce ripening of the female, while the sperms are stored for later use.Correct timing of stripping of the females in relation to hypophysation proved to be critical for obtaining good hatching results. This was increasingly so when temperatures were high. The best results in these experiments were obtained when stripping took place 21, 11 or 7 h after hypophysation at 20, 25 and 30°C, respectively.At this time the eggs were flat, with the cytoplasm concentrated at the animal pole as a reddish-brown spherical cap. The incubation period of the eggs decreased with increasing temperature. In all instances a large proportion of deformed fry occurred wiich was inversely related to the hatching percentage. Incubation without a regular water exchange gave 4% more hatching, 6% less deformation and a shorter incubation period than incubation with water exchange.Hypophysation was repeated four times with 1-, 2- or 3-week intervals and resulted in successful stripping, fertilization and hatching of the eggs after each hypophysation.     

Glucagon-like peptide-1 (GLP-1) immunoreactivity in the forebrain and pituitary of the teleost, Clarias batrachus (Linn.)

Glucagon-like peptide-1-immunoreactivity (GLP-ir) was seen in several olfactory receptor neurons in the olfactory epithelium and in the olfactory nerve fascicles that extend caudally to the bulb and innervate the glomerular layer. Thick GLP-ir fascicles were seen in the medial olfactory tracts (MOT); these probably represent the extrabulbar olfactory projections. GLP-ir fibers in the MOT penetrate into the telencephalon, swing dorsocaudally into the area ventralis telencephali/pars supracommissuralis (Vs) just above the anterior commissure. The immunoreactive fascicles continue caudally in the dorsal hypothalamus and are traceable as far as the lateral recesses. Scattered GLP-ir fibers were seen in the ventral telencephalon and preoptic area. While several immunoreactive cells were seen in the pars intermedia of the pituitary gland, few were encountered in the rostral pars distalis and proximal pars distalis. Role for the peptide in the processing of olfactory information and in the regulation of pituitary gland may be suggested.