Oreochromis Aureus Research Articles

Viral encephalitis of tilapia larvae: Primary characterization of a novel herpes-like virus

We report here an outbreak of an acute disease that caused high mortality rate in laboratory-reared tilapia larvae. The disease was initially observed in inbred gynogenetic line of blue tilapia larvae (Oreochromis aureus) and could be transmitted to larvae of other tilapia species. Based on the clinical manifestation (a whirling syndrome), we refer to the disease as viral encephalitis of tilapia larvae. The disease-associated DNA virus is described and accordingly designated tilapia larvae encephalitis virus (TLEV). A primary morphological, biophysical and molecular characterization of TLEV is presented. By virtue of these properties, the newly discovered virus is a herpes-like virus. Phylogenetic analysis, albeit limited, confirms this assumption and places TLEV within the family of Herpesviridae and distantly from the families Alloherpesviridae and Iridoviridae. By using PCR with virus-specific primers, diseased larvae and adult TLEV carriers were also identified in tilapia delivered from external hatcheries.

OProduction of salinity tolerant Nile tilapia, Oreochromis niloticus through traditional and modern breeding methods: 1- Application of interspecific hybridization with blue tilapia,Oreochromis aureus as traditional method

his study was conducted to produce a salinity tolerant Nile tilapia, Oreochromis niloticus through interspecific hybridization with Oreochromis aureus. Growth performance, proximate body composition, feed utilization, body amino acid profile and some reproductive characteristics of the offspring produced under different salinity levels were evaluated. The results revealed that the productive performance traits of (♀ O. niloticus x ♂ O. aureus) and (♀ O. aureus x ♂ O. niloticus) had significant superiority (P≤0.05) in most of these traits at freshwater, 16 ppt and 32 ppt compared to either O. niloticus or O. aureus. Most of the productive performance traits of O. niloticus, (♀ O. niloticus x ♂ O. aureus) and (♀ O. aureus x O. niloticus ♂) had significantly decreased (P≤0.05) with increasing salinity levels. Moreover, O. aureus showed more salinity tolerance and significant superiority (P≤0.05) of feed utilization and survival rate at salinity level of 32 ppt compared with the other genotypes of fish at the same salinity level.

Growth, mortality and reproduction of the blue tilapia Oreochromis aureus (Perciformes: Cichlidae) in the Aguamilpa Reservoir, Mexico

Tilapia production has increased in Aguamilpa Reservoir, in Nayarit, Mexico, in the last few years and represents a good economic activity for rural communities and the country. We determined growth parameters, mortality and reproductive aspects for 2413 specimens of blue tilapia Oreochromis aureus in this reservoir. Samples were taken monthly from July 2000 through June 2001, of which 1 371 were males and 1 042 were females. Standard length (SL) and total weight (TW) were measured in each organism. The SL/TW relationships through power models for sexes were determined. The growth parameters L infinity k, and t0 of the von Bertalanffy equation were estimated using frequency distribution of length through ELEFAN-I computer program. Finally the reproductive cycle and size of first maturity were established using morph chromatic maturity scale. The results suggested that the males and females had negative allometric growth (b < 3). Significant differences were found between SL/TW model for the sexes, suggesting separate models for males and females. Results indicate that there are no differences in growth rates between sexes; the proposed parameters were L infinity = 43.33 cm standard length, k = 0.36/year and t0 = -0.43 years. Natural and fishing mortality coefficients were 0.83/year and 1.10/year, respectively. The estimated exploitation rate (0.57/year) suggested that during the study period the fishery showed signs of overfishing. Blue tilapia reproduces year-round; the highest activity occurs from January through May and size of first maturity was 23 cm SL. We conclude that it is necessary to establish a minimum catch size in this reservoir based on the reproductive behavior of this species.

Molecular cloning and sexually dimorphic expression of DMRT4 gene in Oreochromis aureus

The DM-domain gene family has at least eight members with conserved DNA-binding DM-domain, which encodes putative transcription factors related to the sexual regulator Dsx of Drosophila and Mab-3 of C. elegans. Although some of the DM genes are involved in sexual development, the function of most of these genes remains unclear. In this study, rapid amplification cDNA ends (RACE) was used for the isolation of DMRT4 full-length cDNA from the ovary of the blue tilapia Oreochromis aureus. The full-length of DMRT4 cDNA was 1,571 bp, containing the 148 bp 5'-untranslated region, 193 bp 3'-untranslated region and 1,230 bp open reading frame. The deduced amino acid sequence of the open reading frame (ORF) encoded a protein of 409 amino acids with a theoretical pI of 8.492 and a calculated molecular weight of 44.12 kDa. One conserved functional domain, DM-domain was identified in blue tilapia DMRT4. The DMRT4 full-length gene obtained from the blood was 1,741 bp, containing a 156 bp intron. Phylogenetic analysis indicated that the amino acid sequences encoded by DMRT4 genes from different species had a high degree of sequence identity as revealed in phylogenetic tree constructed. Real-time quantitative Reverse-Transcription Polymerase Chain Reaction (RT-PCR) was used to analyze the expression patterns of DMRT4 in different developmental stages and different tissues in Oreochromis aureus. DMRT4 mRNA was detected from early gastrulae stage during embryonic development, and maintained a considerable high level until 1 day post hatching. With the increase of age, enhanced DMRT4 mRNA was observed in ovary and brain. After 15 and 30 days, fries treated with 17beta-estradiol had a significant increase in DMRT4 mRNA levels compared with the control fries (P < 0.05). DMRT4 was found to be expressed in the ovary and endbrain, thalamencephalon, pituitary, not detected in the liver, kidney, spleen, heart and muscle of adult fish. These results showed that the DMRT4 gene have potentially important roles in gonadal development and may have contributed to the functional endocrine axis. Our study provides fundamental understanding to the structure and functions of DMRT4 protein and the mechanisms of sex control in Oreochromis aureus.

Threatened fishes of the world: Moapa coriacea Hubbs and Miller, 1948 (Cyprinidae)

Common name: Moapa dace. Conservation status: Endangered (U.S. Department of the Interior 1967), Critically Endangered, IUCN (Gimenez 1996). Identification: Small embedded scales, narrow caudal peduncle and a bright black spot at the base of deeply forked tail. Pharyngeal teeth (0,5–4,0) hooked but with a grinding surface. Adults 50 to 120 mm total length. Drawing adapted from La Rivers (1962). Distribution: Endemic to the upper Muddy River system, Clark County, Nevada where the river originates from over 20 thermal springs. Prior to 1995 Moapa dace occupied 9.5 stream km including the upper Muddy River and spring-fed tributaries (U.S. Fish and Wildlife Service 1995). Distribution has contracted to 2 km (unpublished data) since the 1995 invasion of blue tilapia, Oreochromis aurea. Abundance: In 1994 the population was about 3,800, but after tilapia invasion dropped below 1,600 (Scoppettone et al. 1998) where it has remained (unpublished data). Habitat and ecology: Omnivorous but tends toward carnivory. Feed primarily on drift in areas adjacent to fast water 26–32°C. Reproduction: Occurs year round in spring-fed tributaries to the Muddy River in water temperature of 30–32°C (Scoppettone et al. 1992). Threats: Nonnative species (Scoppettone 1993; Scoppettone et al. 1998) and ground-water pumping (Mayer and Congdon 2008). Conservation actions: Moapa Valley National Wildlife Refuge was established in the upper Muddy River for the protection and perpetuation of Moapa dace. Barrier installation and chemical removal of blue tilapia downstream of refuge habitat provides 2 km of stream without tilapia. Conservation recommendations: Eliminate tilapia from the Muddy River system and control or eliminate other nonnative species. Protect spring discharge from excessive water withdrawal. Remarks: Given a high priority for recovery by the U.S. Government. Environ Biol Fish (2009) 86:339–340 DOI 10.1007/s10641-009-9524-1

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

Structural and autooxidation profiles of myoglobins from three species and one hybrid of tilapia (Cichlidae, Perciformes)

cDNAs encoding myoglobin were cloned from the slow skeletal muscles of three representative species of tilapia, namely, Nile tilapia Oreochromis niloticus, blue tilapia O. aureus, Mozambique tilapia O. mossambicus and one hybrid O. niloticus female symbol x O. aureus male symbol, and the primary structures were deduced. All cDNAs contained an open reading frame of 444 base pairs, encoding 147 amino acids. The amino acid sequences of Mb were completely conserved among these species, though species variations in the nucleotide sequences were recognized both in coding and non-coding regions. The amino acid sequence identity was around 70-80% compared to other teleostean Mbs. In comparison of each alpha-helical segment (A through H) and the intersegment regions to the counterparts of tuna myoglobin, the alpha-helical segments C and F as well as the intersegment regions F-G and G-H were identical. The identities of alpha-helical segments B and H and the intersegment region F-G were relatively low. Differences were also recognized in the hydropathy plot and the tertiary structures obtained by homology modeling. The autooxidation rates at 25 degrees C of myoglobin fraction from the slow skeletal muscle were essentially the same among the above tilapia species, as expected from the conserved amino acid sequences.

Contact with Males is not Necessary for Natural Spawning of Tilapia Females, and Natural Spawns of Isolated Females Remain Viable for Controlled Artificial Reproduction.

Blue tilapia Oreochromis aureus (Steindachner) females isolated in glass tanks from visual, olfactory or behavioural contact with males spawned spontaneously, indicating that females do not require cues from males to spawn naturally. Inter-spawning interval of isolated females in contact (17.0 days) and out of contact (17.3 days) with males was shorter (P

Controlled Artificial Reproduction in Mouth Brooding Tilapia with Human Chorionic Gonadotropin:

A protocol for induced breeding in mouth brooding tilapia for genetic improvement is discussed. Human chorionic gonadotropin (HCG) was suspended in calcium free Hanks' balanced salt solution (c-f HBSS), and injected into the back muscle of blue tilapia (Oreochromis aureus) females at the dose of 0.5, 1.0 or 1.5 IU g-1 female. Males were injected with the hormone at the dose of 1.5 IU g-1 male. Control females and males were injected with c-f HBSS only. Females were isolated individually and allowed to spawn naturally, but isolated males were stripped for sperm. Sperm was diluted 0, 1, 2, 3, 4, or 5x in c-f HBSS and stored in the refrigerator at 4oC for 4 days. Naturally spawned egg batches of an isolated, hormone-injected female were fertilized daily with stored sperm of hormone-injected males and incubated at 28± 2oC. Spawning time was significantly advanced and more consistent among hormone-injected females than controls, and the response increased with an increase in hormone concentration. Apparently, the hormone enhanced predictable and synchronous spawning. The hormone also increased sperm production significantly. Sperm production in both hormone-injected and control males decreased over sampling time. The c-f HBSS extended viability of eggs removed from the mouths of isolated females for 1 h, and generally improved sperm motility and fertility (capacity to fertilize eggs) during cold storage. For all dilutions, sperm quality dropped with storage time. Hatching success of eggs fertilized with low (1-3x) sperm dilutions was better than that achieved with high (>3x) sperm dilutions and undiluted sperm. The hormone induction protocol facilitated greater control over the collection of gametes and programming of controlled artificial reproduction. Journal of the Ghana Science Association Vol. 10 (2) 2008: pp. 70-77

Development of Heat-Shocked Tilapia Eggs Following Activation by Water Immersion or Heterologous Fertilization: Implications for the Initiation of Gynogenesis

An attempt was made in this study to initiate artificial gynogenesis in tilapia eggs by water activation, as an alternative to heterologous fertilization. Blue tilapia Oreochromis aureus (Steindachner) eggs activated by water immersion and heat-shocked at 42 oC failed to develop into gynogens. However, heat shock of eggs fertilized with normal or irradiated carp sperm developed into putative gynogens. Un-shocked normal or irradiated carp-fertilized eggs died shortly after hatching due to haploid condition or hybrid inviability. Results of this study indicate that, sperm contact is necessary for successful initiation of gynogenesis. Journal of the Ghana Science Association Vol. 9 (2) 2007: pp. 32-37

Laboratory Efficacy of Amoxicillin for the Control of Streptococcus iniae Infection in Blue Tilapia

AbstractExperimental feeding trials were performed to evaluate the efficacy of amoxicillin (AMX) in controlling Streptococcus iniae infection in blue tilapia Oreochromis aureus. The doses of AMX active ingredient tested were 0, 5, 10, 30, and 80 mg/kg of fish body weight (BW) per day. Administration of medicated feed started within 22–24 h postchallenge by waterborne exposure to S. iniae (after skin scraping) and continued for 12 consecutive days, followed by a 17‐d posttreatment observation. Oral administration of AMX‐medicated feed for 12 d at a daily rate of 10, 30, and 80 mg/kg BW significantly increased the survival of S. iniae−infected tilapia from 3.8% in the challenged, nonmedicated positive control to 45, 75, and 93.8%, respectively. The survival rate was significantly higher in the 80‐mg treatment (93.75%) than the 10‐mg treatment (45%) but did not differ significantly between the 10‐mg (45%) and 30‐mg (75%) treatments. At the conclusion of the experiment, no carriers were detected in any challenged group receiving AMX‐medicated diet, whereas the bacterium was recovered from the nonmedicated, challenged survivors of the infection.

Two unlinked loci controlling the sex of blue tilapia (Oreochromis aureus).

Sex determination in the blue tilapia (Oreochromis aureus) is thought to be a WZ-ZZ (female heterogametic) system controlled by a major gene. We searched for DNA markers linked to this major gene using the technique of bulked segregant analysis. We identified 11 microsatellite markers on linkage group 3 which were linked to phenotypic sex. The putative W chromosome haplotype correctly predicts the sex of 97% of male and 85% of female individuals. Our results suggest the W locus lies within a few centimorgans of markers GM354, UNH168, GM271 and UNH131. Markers on LG1 also showed a strong association with sex, and indicate the segregation of a male-determining allele in this region. Analysis of epistatic interactions among the loci suggests the action of a dominant male repressor (the W haplotype on LG 3) and a dominant male determiner (the Y haplotype on LG1). These markers have immediate utility for studying the strength of different sex chromosome alleles, and for identifying broodstock carrying copies of the W haplotype.

Application of RAPD markers in fish: Part I ? some genera (Tilapia, Sarotherodon and Oreochromis) and species (Oreochromis aureus and Oreochromis niloticus) of Tilapia

Random amplified polymorphic DNA (RAPD) analysis was applied to the four-tilapia species (three genera): redbelly tilapia (Tilapia zillii), white tilapia (Sarotherodon galilaeus), blue tilapia (Oreochromis aureus) and Nile tilapia (Oreochromis niloticus). Twenty random primers - fifteen (10-mer) and five (20-mer) - were used to assay polymorphisms among three genera and between two species. Different RAPD fragment patterns were observed for different genera species. Results showed that there are great differences among the three genera of tilapia fish. Also, data demonstrated that RAPD markers are useful for the systematic investigation at the level of tilapia species.

Diseases resistance of Nile tilapia ( Oreochromis niloticus), blue tilapia ( Oreochromis aureus) and their hybrid (female Nile tilapia×male blue tilapia) to Aeromonas sobria

The resistance to disease caused by the Aeromonas sobria in three genotypes of tilapia, Nile tilapia ( Oreochromis niloticus), blue tilapia ( Oreochromis aureus) and their hybrid (female Nile tilapia×male blue tilapia) was studied . Based on comparison of median lethal dose (LD 50), functions of nonspecific immunity, including total amount of complements, bactericidal reaction by alternative pathway of complement (C 3 shunt), percentage of erythrocyte C 3b receptor aggregates, leukocyte phagocytic function, as well as erythrocyte active rosette of T lymphocyte, it is indicated that the hybrid has the highest resistance to the disease caused by A. sobria, while blue tilapia has the lowest resistance.

Distribution of mercury in the tissues of five species of freshwater fish from Lake Mead, USA.

Total mercury (Hg) concentrations were determined in seven tissues (skeletal muscle, liver, blood, gonad, brain, gill, and heart) of 59 striped bass and four tissues (muscle, liver, blood, and gonad) of 69 largemouth bass, 76 channel catfish, 12 bluegill, and 22 blue tilapia collected from Lake Mead, USA. Mercury levels generally increased according to trophic level and fish length. For striped bass, mean Hg levels (ng g(-1), wet mass) were highest in the liver (531), followed by muscle (309), heart (186), gonad (136), brain (77), gill (52), and blood (36). Similarly, Hg levels in the catfish and tilapia were liver > muscle > gonad > blood. In contrast, largemouth bass and bluegill had the highest levels in muscle, followed by liver, gonad, and blood. Generally, Hg levels were strongly correlated among the tissues, especially for blood/muscle and blood/liver. As the body burden of Hg increased, the concentration in blood and organs increased relative to the concentration in muscle. The trend was most pronounced for the liver. These relationships could form the basis of a predictive model and suggest that blood and muscle (plugs) could be useful for a non-lethal measure of Hg concentration and exposure in fish. For the striped bass, elevated Hg levels in the tissues were also correlated with degree of emaciation. Liver-to-muscle ratios were similar to literature values, except for tilapia with an average ratio of approximately 1.7, which is higher than generally reported for non-piscivores. Finally, this study demonstrates the usefulness of a solid sampling approach in trace element monitoring, especially as pertaining to in vivo analysis, analysis of a large number of samples and reduction of contamination risk.

Inheritance of sex in two ZZ pseudofemale lines of tilapia Oreochromis aureus

This paper reports a study on the sex determination system of the blue tilapia, Oreochromis aureus. Investigations were carried out using a pseudofemale line in two populations of O. aureus, known as Egyptian Population (EP) and Israel Population (IP). In O. aureus, males are the homogametic sex (ZZ/ZW), and sex reversal of fry with estradiol results in the production of some functional sex-reversed fish with a female phenotype and ZZ male genotype, known as pseudofemales or Δ-females. Crosses between ZZ pseudofemales and ZZ males theoretically should provide monosex ZZ male progeny only. We have studied the sex ratios of progeny from 43 IP (F 2 to F 3 generations) and 51 EP (F 1 to F 5 generations), pair-matings between normal males and pseudofemales. In IP, the male percentage in progenies ranged between 83% to 100% in F 2 and 66% to 100% in F 3. In EP, male percentage was more constant, varying from 88% to 100% in F 1, from 96% to 100% in F 3 and from 97% to 100% in F 5. In EP, F 2 and F 4 pseudofemales produced only monosex male progeny. This apparent difference in sex ratio frequency distributions between the two O. aureus pseudofemale lines could be due to the selection of males. EP pseudofemales were mated with their siblings for F 2 and F 3 pseudofemales or with closely related males for F 4 and F 5 pseudofemales. Conversely, IP pseudofemales were crossed with nonrelated males originating from research center broodstock, resulting in a higher proportion of females in sex ratio of progenies from successive generations of pseudofemales. The role of inbreeding is discussed in the context of predominantly monofactorial sex chromosome determination system operating in this species, influenced by other factors (genetic and environmental). The present study also shows that it is possible to fix the male sex determining factors (Z sex chromosome and genetic factors) in a line of pseudofemales, producing a high percentage of male progeny in five successive generations.

The acute toxicity of copper to blue tilapia in dilutions of settled pond water

Blue tilapia fingerlings ( Oreochromis aureus) were exposed to copper (Cu) in a series of static toxicity tests. The water used in this study was composed of settled pond water or settled pond water diluted with deionized water. Estimates of mean 96-h LC50 values (median lethal concentration) were 43.06, 6.61, 0.69 and 0.18 mg/l Cu as copper sulfate) in waters having total alkalinities of 225, 112, 57 and 16 mg/l CaCO 3, respectively. These data demonstrate the typical acute toxicity response of Cu, in which toxicity to tilapia increases as pH, total alkalinity and total hardness decrease. The results indicate that blue tilapia are relatively tolerant to Cu when compared to other species and that copper sulfate treatments in low-alkalinity waters may be detrimental to the health of blue tilapia.

Ontogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia

Ontogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia

Mercury concentrations in fish from Lake Mead, USA, related to fish size, condition, trophic level, location, and consumption risk.

Total mercury (Hg) concentrations were determined in the skeletal muscle of 339 fish collected during the fall of 1998 and spring of 1999 from Lake Mead, USA, the nation's largest human-made reservoir. Five species of fish representing a range of trophic levels and the lake's principal game fishes were studied. Hg generally increased with trophic level and fish size. Median Hg concentrations (ng/g wet mass) were 277 in striped bass, 168 in channel catfish, 160 in largemouth bass, 75 in bluegill, and 8 in blue tilapia. Overall, fish from Las Vegas Bay and Boulder Basin had the lowest Hg concentrations, possibly a result of biodilution in this biologically productive area. In general, fish-mercury advisories might include a warning about consuming fillet from emaciated fish, based on the finding that Hg concentrations in 59 striped bass (captured during a scarce-food season) correlated inversely ( r = -0.89, p < 0.001) with a fish nutritional-status factor. This is consistent with starvation-concentration, whereby Hg in fish muscle is lost at a slower rate than the muscle mass. The median concentration found for 139 striped bass corresponds to a recommended risk-based consumption limit of three 8-oz. (227-g) meals per month for a 70-kg adult. Finally, this paper serves as a useful archive for future research and long-term studies of Hg in Lake Mead fish.

Ontogenetic variations of thermal optimum for growth, and its implication on thermolabile sex determination in blue tilapia

Knowledge of how the optimum temperature for growth (T° opt ) varies during ontogeny, and how close it is to the temperatures that induce phenotypic masculinization is fundamental to the understanding of the evolution of thermolabile sex determinism (TSD) in fishes. In blue tilapia Oreochromis aureus, T° opt is 32.6° C at the start of exogenous feeding (10 mg fish) and it decreases by c. 1° C each time that the fish body mass increases by an order of magnitude. Temperatures <35° C are not sufficient to induce complete phenotypic masculinization. Based on a multiple-regression model (r 2 =0.938) plotting growth against body mass and water temperature, genotypically female tilapia living at high temperatures during the thermosensitive period (21-28 days) and being reversed into phenotypic males would incur an initial growth disadvantage over fish living at T° opt , but not over those living at slightly colder temperatures (27-29° C). This initial disadvantage would be later compensated for by faster growth because of between-sex growth dimorphism to the detriment of phenotypic females. These arguments suggest that there is no definite pressure against the selection of TSD in blue tilapia and probably other Oreochromis spp.