Clarias Macrocephalus Research Articles

The hydroponic production of lettuce (Lactuca sativa L) by using hybrid catfish (Clarias macrocephalus×C. gariepinus) pond water: Potentials and constraints

Abstract An experiment was conducted at the Asian Institute of Technology, Thailand, for 54 days to investigate on the effect of pond water filtration and aggregates (hydroponic substrates) on lettuce (Lactuca sativa L.) production, nutrient uptake and growth. A 2 × 3 factorial experiment consisting of 2 filtration regimes (unfiltered versus partially filtered pond water) and 3 aggregates (styrofoam as control, sand, and gravel). The hydroponic units were placed on a bamboo platform across the pond surface. An earthen pond (226 m2) was stocked with 8000 hybrid catfish with an average initial weight of 6.58 ± 1.72 g. The fish were fed with commercial pelleted feeds containing 30% crude protein. Twenty-one days old lettuce seedlings were transplanted on to hydroponic units after stocking catfish for 4 months in the pond. Pond water was partially filtered by using a settling tank and filtration tank, which contained netting materials to trap solids. Lettuce plots were irrigated twice daily at 0800 and 1600 h using either filtered or unfiltered pond water for 45 min. The highest head weight and yield of lettuce were observed with plants grown on the sand media followed by gravel and the control treatments. Partially filtered pond water treatments had significantly higher lettuce yield (P Although pond water is mainly constrained by the high suspended solids, and low dissolved oxygen, the study showed that filtration of catfish pond water enhanced the potential to use it for the hydroponic lettuce production.

PROTEINASES IN HYBRID CATFISH VISCERA: CHARACTERIZATION AND EFFECT OF EXTRACTION MEDIA

Proteolytic activity from viscera extract of hybrid catfish (Clarias macrocephalus × Clarias gariepinus) was investigated. Optimal pH and temperature for casein hydrolysis were 9.0 and 50C, respectively. The enzyme was stable to heat treatment up to 40C and over a pH range of 7–11 for 30–120 min. The proteolytic activity was effectively inhibited by soybean trypsin inhibitor, benzamidine, phenylmethylsulfonyl fluoride and N-p-tosyl-L-lysine chloromethyl ketone. Activities of the viscera extract continuously decreased as NaCl concentration increased, while activities increased as CaCl2 concentration increased. Based on the proteinase activity of zones separated by electrophoresis, the molecular mass of the major proteinases in hybrid catfish viscera was 23 and 20 kDa. The effect of extraction media on recovery of proteinases was also studied. Extraction of the viscera powder with 50 mM Tris-HCl, pH 7.0 containing 0.5 M NaCl and 0.2% (v/v) Brij 35 rendered a higher recovery of proteinase activity than other extractants tested (P < 0.05). The results suggested that major proteinases in hybrid catfish viscera were heat-activated alkaline proteinases, most likely trypsin-like serine proteinases. PRACTICAL APPLICATIONS Hybrid catfish viscera is an abundant and underutilized resource that can be used as a unique proteinase source. Proteinase from various sources catalyzes the hydrolysis of peptide bonds. Thus, it is expected that like other proteinases, hybrid catfish proteinase would be useful in biomedical, food and beverage application. Moreover, the presented extraction media could be adopted to recover the trypsin-like serine proteinase from hybrid catfish viscera, which is currently a solid waste of Pa-duk-ra industry.

Electrical activity of asian catfish Clarias macrocephalus (Claridae, Siluriformes) during spawning behavior

Electrical activity of asian catfish Clarias macrocephalus (Claridae, Siluriformes) during spawning behavior

The nutritional value of lipids in various tropical aquatic animals from rice–fish farming systems in northeast Thailand

Knowledge on the lipid compositions of tropical freshwater aquatic animals is limited despite their importance in the human diet and the health-related benefits of fish lipids. This study examines the lipid content and fatty acid composition from the edible muscle tissue of some common freshwater aquatic animals that inhabit rice fields in Thailand, namely snakehead ( Channa striatus), Gunther's walking catfish ( Clarias macrocephalus), climbing perch ( Anabas testudineus), blackline rasbora ( Rasbora borapetensis), swamp barb ( Puntius brevis), and freshwater prawn ( Macrobrachium nipponense). All specimens were low in muscle fat (≤1.1% of wet weight). There was considerable variation in the fatty acid composition between species. All species were good sources of the essential fatty acids, and particularly of C22:6n-3 (5.2–13.3% total FA) and C20:4n-6 (7.2–14.6% total FA), signifying their high nutritional quality for human nutrition. The findings indicate that strategies for rural development, food security, and alleviation of poverty in rural areas need to pay special attention to the management of aquatic resources to ensure the health and well-being of rural people.

Use and exchange of aquatic genetic resources for food and aquaculture: Clarias catfish

AbstractThere are 58 species of Clarias recognized in FishBase (as of January 2009), 33 in Africa and 25 in Asia. Aquaculture of clariids is important with 30 countries reporting a total production of over 300 000 t worth nearly US$400 million in 2006. Most production involves the African Clarias gariepinus (Burchell, 1822) and three Asian species, Clarias batrachus (Linnaeus, 1758), Clarias macrocephalus (Günther, 1864) and Clarias fuscus (Lacep'de, 1803). In much of Asia, hybrids of introduced C. gariepinus with native species dominate aquaculture and may pose threats to the purity and viability of wild populations. Many local strains have evolved within farms, some of which have been described and included in genetic management programs. Genetic variation among species and populations is significant, but to date little work on selective breeding of the group has been reported. Conservation efforts have so far focused on ex situ methods, primarily for farmed stocks, but these are few and expensive and farmed stocks are often of lower genetic diversity than wild stocks. In situ conservation of genetic material, both for aquaculture and for the maintenance of fitness in wild populations in light of changes occurring in the watershed, needs to be considered as a more viable long‐term strategy. The preservation of ecosystem functional integrity is thus a prerequisite for the long‐term conservation of Clarias genetic resources for food and aquaculture.

Use and exchange of aquatic genetic resources in aquaculture: information relevant to access and benefit sharing

Use and exchange of aquatic genetic resources in aquaculture: information relevant to access and benefit sharing

Chilled storage of walking catfish ( Clarias macrocephalus) semen

The aim of the present study was to determine changes in sperm quality of walking catfish ( Clarias macrocephalus) during its spawning season, and develop a simple and efficient protocol for the chilled storage of semen at 4 °C. Semen samples were evaluated monthly during April–November in 2006. Percentage of spermiating males and sperm motility peaked during the middle of the spawning season, June–September. Sperm density and seminal plasma osmolality increased significantly ( P < 0.05) throughout the spawning season, while semen pH did not change during this period. The effects of extender, dilution ratio and timing of chilled storage on successful storage period of extended semen were examined during the years 2006–2007. Fresh semen was diluted 1:1 with several sperm extenders, calcium-free Hanks' balanced salt solution (Ca–F HBSS), Hanks' balanced salt solution (HBSS), extender 7 (NaCl 5.780 g, KCl 2.558 g, CaCl 2·2H 2O 0.103 g, NaHCO 3 0.235 g, MgCl 2·6H 2O 0.220 g, pyruvate 6.0 g, citric acid 0.100 g, HEPES buffer 2.380 g in 1000 mL distilled water), extender 13 (NaCl 8.760 g in 1000 mL distilled water), and modified Cortland, in tissue culture flasks. Longest successful storage period of sperm was 10 days with Ca–F HBSS. Semen diluted with Ca–F HBSS at 1:1, 1:2 or 1:4 ratios significantly lengthened ( P < 0.05) the storage period over those at dilutions of 1:9 or 1:19. To determine the effect of season on the success of chilled storage, semen diluted with Ca–F HBSS at a ratio of 1:4 was prepared at three sampling intervals in the beginning (May), middle (August) and end (November) of spawning season in 2007. Extended semen prepared in August remained motile (20 ± 3.1%) for as long as 10 days, whereas those prepared in May or November were immotile on days 9 and 7 of storage, respectively. Extender-preserved semen was capable of fertilizing eggs as efficiently as fresh semen within two days of storage. A significant decrease in fertilization and hatching rates of extender-preserved semen compared to fresh semen on days 4 and 6 was due to low sperm motility. These results demonstrate that semen of walking catfish can be stored for short term at 4 °C without appreciably affecting motility and fertilization.

Textural Properties of Gel Made from Hybrid Catfish (Clarias macrocephalus x C.gariepinus) Fillets Chilled in Ice and at Temperature of 4 ÌC

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Genetic variation and population structure of endemic yellow catfish, Horabagrus brachysoma (Bagridae) among three populations of Western Ghat region using RAPD and microsatellite markers

Random amplified polymorphic DNA (RAPD) and microsatellite markers were applied to evaluate the genetic variation in endemic and endangered yellow catfish, Horabagrus brachysoma sampled from three geographic locations of Western Ghat, South India river systems. In RAPD, of 32 10-mer RAPD primers screened initially, 10 were chosen and used in a comparative analysis of H. brachysoma collected from Meenachil, Chalakkudy and Nethravathi River systems. Of the 124 total RAPD fragments amplified, 49 (39.51%) were found to be shared by individuals of all 3 populations. The remaining 75 fragments were found to be polymorphic (60.48%). In microsatellites, six polymorphic microsatellite loci were identified by using primers developed for Pangasius hypophthalmus, Clarias macrocephalus and Clarias gariepinus. The identified loci were confirmed as microsatellite by sequencing after making a clone. The nucleotide sequences of 6 loci were published in NCBI genbank. The number of alleles across the six loci ranged from 4 to 7 and heterozygosities ranged from 0.07 to 0.93. The mean number of alleles and effective number of alleles per locus were 5.00 and 3.314, respectively. The average heterozygosity across all investigated samples was 0.72, indicating a significant deficiency of heterozygotes in this species. RAPD and microsatellite methods reported a high degree of gene diversity and genetic distances depicted by UPGMA dendrograms among the populations of H. brachysoma.

Sixteen EST‐linked microsatellite markers in Günther's walking catfish, Clarias macrocephalus

Twenty-seven new microsatellite sequences were identified by screening 2029 expressed sequence tags from Günther's walking catfish, Clarias macrocephalus. Sixteen loci were polymorphic with the number of alleles ranging from two to 16 per locus and the observed and expected heterozygosities ranging from 0.4667 to 0.9333 and from 0.427 to 0.8819 per locus, respectively. Cross-species amplifications of all 16 primer pairs were tested in four other species of catfish including Clarias gariepinus, Pangasius hypophthalmus, Pangasius larnaudii and Pangasianodon gigas. Eleven loci were found to amplify in other species, with the number of polymorphic loci ranging from one in P. larnaudii to nine in C. gariepinus.

Molecular characterization and seasonal expression of the vitellogenin gene from Günther's walking catfish Clarias macrocephalus

The complete cDNA sequence for walking catfish vitellogenin (VTG) (4192 bp) contained 51 bases of 5′-untranslated region, an open reading frame of 4050 bp encoding 1350 amino acids, 60 bases of 3′-untranslated region, and a poly(A) tail of 31 nucleotides. The deduced amino acid sequence of walking catfish VTG shared 58.9%, 56.9%, 41.7%, 32.6% and 8.1% identity with VTGs of common carp, zebrafish, rainbow trout, Xenopus and chicken, respectively. Results agreed with previous studies which indicated that among fishes, VTG is not a highly conserved protein, but shares a common general structure. Northern blot and RT-PCR revealed that VTG was specifically expressed in the liver of female fish. To establish the relationship between gonadosomatic index (GSI) and the level of hepatic VTG transcript, monthly change in the GSI of females was monitored over a 1-year period from June 2006 to May 2007. The relative copy number of VTG mRNA was determined by quantitative real-time PCR. Significant variations of mean GSI values and VTG mRNA levels (P<0.05) were observed among months. From June to August, mean GSI values ranged from 8.60±0.35% to 13.07±0.59%. Highest mean GSI value (18.27±2.51%) and maximum VTG transcript levels were observed in September. From October through March, ovarian weight steadily declined, with the lowest mean GSI value (0.77±0.38%) in January. The expression profile of the VTG gene reflected the annual changes in reproductive cycle of female walking catfish, showing high levels during the breeding period and low levels during resting periods.

Response to Selection for Body Weight of Walking Catfish, &lt;i&gt;Clarias macrocephalus&lt;/i&gt; (Giinther) after Two Generations of Bi-Directional Mass Selection

A study was conducted on divergent lines of Walking Catfish (Clarias macrocephalus) to assess the response to mass selection for body weight at Kasetsart University, Thailand. Broods of C. macrocephalus used in this experiment were seventh generation progeny of a base population originating from random mating of six natural population. Mass selection for body weight was performed at 10 month of age in the high and low line directions. Fifty pairs of F2 selected brooders from the two divergent lines were individual-mated to produce second generation offspring. Fish were reared in indoor tanks for 7 weeks and in cages for 26 weeks to determine response to bi-directional selection for body weight. Significant divergence in body weight and length of the low and high line occurred at 29 and 33 weeks of age. Response to selection for body weight, measured as the half of the divergence between low and high line, after two generations was 4.16 g (4.16%) and 3.19 g (3.4%) at 29 and 33 weeks of age, respectively. Total length difference between the high and low line was 0.35 cm (1.64%) at 33 weeks of age. Selection differential between divergent lines could have underestimated response in one direction and generated asymmetry in response between selected lines.J. Inst. Agric. Anim. Sci. 2003 24:67-74

Gene-centromere Mapping at Four Microsatellite and Five Isozyme Loci in Clarias macrocephalus Based on Meiotic Gynogenetic Offspring

Gene-centromere Mapping at Four Microsatellite and Five Isozyme Loci in Clarias macrocephalus Based on Meiotic Gynogenetic Offspring

Dietary arginine requirement of fingerling hybridClarias(Clarias gariepinus×Clarias macrocephalus)

The dietary arginine requirement of fingerling hybrid Clarias (Clarias gariepinus×Clarias macrocephalus) (4.2±0.03 cm, 0.56±0.04 g) was determined by feeding six isonitrogenous (400 g kg−1 crude protein) and isocaloric (17.9 kJ g−1) amino acid test diets containing casein, gelatin and l-crystalline amino acids with graded levels of arginine (10.0, 12.5, 15.0, 17.5, 20.0 and 22.5 g kg−1) for 4 weeks to triplicate groups. Diets were fed twice a day at 09:00 and 16:00 hours at 8% body weight day−1. Maximum weight gain (523%), best feed conversion ratio (FCR, 1.41), protein efficiency ratio (1.78) and specific growth rate (6.53%) were recorded in fish fed the diet containing arginine at 20.0gkg−1 of the diet. Second-degree polynomial regression analysis of live weight gain and FCR values indicated the dietary arginine requirement at 17.8 and 20.0 g kg−1 of dry diet respectively. Significantly higher carcass protein and protein deposition values were recorded at the requirement level (20.0 g kg−1). Higher fat and lower moisture values were obtained in carcass of fish fed the diet with 15.0g kg−1 arginine. The maximum carcass ash value was noticed in the fish fed at 20.0 g kg−1 dietary arginine. We recommend that the diet for hybrid Clarias (C. gariepinus×C. macrocephalus) should contain arginine in the range of 17.8–20.0 g kg−1 of the dry diet, corresponding to 44.5 and 50 g kg−1 of dietary protein respectively.

Chemical and biochemical changes of hybrid catfish fillet stored at 4 °C and its gel properties

Chemical and biochemical changes of aquacultured hybrid catfish fillet ( Clarias macrocephalus × Clarias gariepinus) and its gel-forming ability as affected by age and sex of fish along with storage time were investigated. Fillets were stored at 4 °C for 0, 3, 6, 9, 12 and 15 days. There was no significant effect of sex and age of fish as well as storage time on fat, moisture and ash contents ( P > 0.05). The total protein, water soluble protein, and salt soluble protein contents of the fillets significantly decreased with storage time ( P < 0.05). On the other hand, pH, total volatile base nitrogen (TVB-N) and autolytic degradation products (ADP) increased as storage time continued ( P < 0.05). Decreases in Ca 2+-ATPase activity and gel properties were observed as storage time increased. However, there was no significant effect of either sex or age of fish on textural properties of gel ( P > 0.05). Hybrid catfish fillet stored at 4 °C should be processed within 6 days.

Biochemical and molecular indicators in aquatic ecosystems: Current status and further applications in Malaysia

Malaysia's aquatic ecosystems contribute 1.6% of her gross domestic product and provide employment to about 100,000 people. They are sources of a significant proportion of the nation's food supply, mainly by marine capture fisheries; but aquaculture, both marine and freshwater is becoming increasingly important. Hence, characterization of the species diversity of Malaysian biological resources (bioresources) is of paramount importance. One of the key components in any biodiversity investigation is elucidation of the population genetic structure of the species being studied, as it is an indication of the status of the species within the ecosystem. It is here that biochemical protein level and molecular DNA level indicators play crucial roles. Thus far, the studies that had been done in Malaysia using such biochemical and molecular markers were mainly on freshwater aquatic species that are important to aquaculture such as the catfish, Mystus nemurus and Clarias macrocephalus, and tilapia, Oreochromis niloticus and O. mossambicus, and the prawns Penaeus monodon and P. merguiensis. Random Amplified Polymorphic DNA (RAPD) and microsatellite markers had been used to study two species of marine turtles that nest on Malaysia's pristine beaches, the hawk's bill turtle, Eretmochelys imbricata and the green turtle, Chelonia mydas. However, none of the top ten marine fish species endemic in this country had been studied yet. A start had been made to study the genetic structure of the green-lipped mussel, Perna viridis, with a view to using it as a biomonitoring agent of environmental pollution. An association was found between increased heterozygosity level for allozyme loci and heavy metal pollution index in this species. This paper discusses these findings and makes suggestions for the use of biochemical and molecular markers as potential biomonitoring agents of pollution levels in future ecotoxicological studies of Malaysia's aquatic ecosystems.

Bioaccumulation of cadmium in an experimental aquatic food chain involving phytoplankton ( Chlorella vulgaris), zooplankton ( Moina macrocopa), and the predatory catfish Clarias macrocephalus × C. gariepinus

The accumulation of cadmium (Cd) was studied in an experimental aquatic food chain involving the phytoplankton Chlorella vulgaris as the primary producer, the zooplankton Moina macrocopa as the primary consumer, and the catfish Clarias macrocephalus × Clarias gariepinus as the secondary consumer. C. vulgaris was first exposed to Cd solutions at 0.00, 0.35, and 3.50 mg l −1, referred to as control group and experimental groups 1 and 2, respectively. Subsequently, each group was fed to three corresponding groups of M. macrocopa. Finally, three groups of catfish were fed these corresponding groups of M. macrocopa. After C. vulgaris was exposed to 3.50 mg l −1 Cd (experimental group 2), the residual Cd in solution was only 4.01 μg l −1, lower than the maximum allowable limit of Cd in natural water sources (5 μg l −1). Cd concentrations in C. vulgaris were 0.01 ± 0.00 μg g −1 (dry wt) in the control group, 194 ± 1.80 μg g −1 (dry wt) in experimental group 1, and 1140 ± 20.06 μg g −1 (dry wt) in experimental group 2. The Cd concentrations in M. macrocopa were 0.01 ± 0.00 μg g −1 (dry wt) in the control group, 16.48 ± 2.23 μg g −1 (dry wt) in experimental group 1, and 56.6 ± 3.23 μg g −1 (dry wt) in experimental group 2. The Cd concentrations in catfish muscle increased with increasing Cd concentrations in the food. After 60 days of fish culture, the mean concentrations of Cd in fish muscle were 0.01 ± 0.00 μg g −1 (dry wt) in the control group, 0.61 ± 0.02 μg g −1 (dry wt) in experimental group 1 and 1.04 ± 0.06 μg g −1 (dry wt) in experimental group 2. Cd concentration in fish muscle of experimental group 2 was equal to the permissible limit. Cd accumulation affected fish growth: at the end of the study, the mean fresh weight (12.81 g) of catfish in the control group, was significantly higher than those experimental group 1 (10.43 g) and experimental group 2 (10.00 g). The results showed that the measurement of Cd concentration in water does not necessarily give a measure of the safety of aquatic organisms as human food. Hence, heavy metal contamination is a matter for concern when organisms are harvested, for fish and human consumption, from natural water sources.

Comparison of some live organisms and artificial diet as feed for Asian catfish Clarias macrocephalus (Gunther) larvae

Summary Experiments were conducted to evaluate the efficacy of five live organisms (Artemia, Brachionus calyciflorus, Chironomus plumosus, Moina macrocopa and Tubifex sp.) and an artificial diet (40% protein) in the larval rearing of Asian catfish Clarias macrocephalus. The larvae were fed three times daily starting at the onset of exogenous feeding. Results showed that the catfish larvae utilized the live organisms more efficiently than the artificial diet. The Tubifex-fed larvae consistently showed the highest growth rate. In trial 1, length increment (64.9 mm), weight gain (3192 mg) and specific growth rate (13.1%) after 8 weeks of feeding were significantly higher (P < 0.05) in catfish larvae given Tubifex than those in all other treatments. In trial 2, length increment after 4 weeks of feeding was highest in larvae fed Tubifex (22.9 mm) although it did not significantly differ from that of larvae given Moina (21.0 mm). However, weight gain of larvae fed Tubifex (253.0 mg) was significantly higher than that of larvae fed Moina (171.6 mg). The specific growth rate was highest for larvae fed Tubifex (15.0%) followed by larvae fed Artemia (14.5%), Moina (14.4%) and Chironomus (12.0%). Survival rates of the catfish larvae ranged from 9 to 39% after 8 weeks in trial 1 and from 26 to 83% after 4 weeks in trial 2. The present results suggest that Tubifex is an excellent food and a potential substitute for Artemia in the rearing of catfish larvae.

Genetic diversity of walking catfish, Clarias macrocephalus, in Thailand and evidence of genetic introgression from introduced farmed C. gariepinus

The Thai walking catfish, Clarias macrocephalus Günther, 1864, is economically important to Thailand. It occupies marshes and swamps that are severely endangered due to population expansion and natural populations are thought to be suffering from massive back-crossing with the C. macrocephalus× C. gariepinus hybrids. Therefore, a study on genetic diversity of this species is required to enable efficient conservation and management plans. In this study, 25 natural populations were collected throughout the country, 12 populations from provinces locate in the Chaophraya river basin in the center of the country, 5 from the Mekong river basin, 1 from the east and 7 from the south. One population of hatchery origin was obtained from the Department of Aquaculture, Kasetsart University in Bangkok. Twelve isozymes and one protein system were analyzed. Among 18 loci resolved, 8 were polymorphic. The number of alleles per locus, average polymorphism and individual polymorphism were significantly higher in collections from the Chaophraya river basin than from the Mekong, east and south. The hatchery population also had relative high genetic variation. Six out of twenty-six populations differed significantly from Hardy-Weinberg equilibrium after Bonferroni correction. None of loci pairs showed significant linkage disequilibrium after Bonferroni correction. The F st value across loci was highly significant from zero. A neighbor-joining tree reveals that populations from the south were genetically distinct from the remaining populations. Alleles peculiar to the African catfish [ C. gariepinus (Burchell, 1822)] genome were observed in 12 of the natural populations and the hatchery population. This is evidence of genetic introgression which has probably persisted for several generations, since there was no significant genotype disequilibrium between the macrocephalus and gariepinus alleles at three diagnostic loci.

Allotriploidy increases sterility in the hybrid between Clarias macrocephalus and Clarias gariepinus

Hybrids between female Thai walking catfish ( Clarias macrocephalus) and male African catfish ( Clarias gariepinus) are capable of reproducing, and this has led to introgression of genes from the paternal species into natural populations of the native C. macrocephalus. Therefore this study was conducted aiming at producing sterile triploid hybrids by means of cold shock. Eggs from C. macrocephalus were fertilized with sperm from C. gariepinus and were subsequently immersed in cold water (7°C) starting 4.5 min after water activation of the eggs, and lasting for 14 min. The cold shock induced 72%, 74% and 88% triploid fish with 44–49% hatching success compared to the control value of 69–78%. At 28 weeks old body weight of the triploid fish was smaller than the diploid counterparts. The frequencies of retarded gonads and ovotestes were smaller in diploid as compared to the triploid hybrids. The average gonado-somatic index (GSI) of female diploid F 1 hybrids was significantly higher than those of the triploids whereas male GSI of the two groups were not statistically different. Fifty percents of the diploid testes produced a few spermatozoa while only 15.8% of the triploid testes did. Likewise larger percentage of the female diploid hybrids (64.3%) had well-developed ovaries marked with vitellogenic oocytes as compared to the triploids (21%). At 44-week-old, although the triploid and diploid females showed similar response to hormone injection, the triploids produced significantly less eggs than the diploids. Both diploid and triploid eggs were capable to fertilize sperm of C. macrocephalus. However, all fry from the triploid F 1 hybrids died at yolk absorption, whereas approximately 80% of the fry from diploid F 1 hybrids survived. No survived fry at yolk absorption were obtained from fertilization between C. macrocephalus eggs and sperm obtained from both triploid and diploid F 1 hybrids.