Shaharudin Abdul Razak

Growth Performance and Gonadal Development of Growth Enhanced Transgenic Tilapia Oreochromis niloticus (L.) Following Heat-Shock-Induced Triploidy.

Abstract: Triploid induction offers a way of considerably reducing fertility in fish, and could therefore be employed to help ensure that any adverse environmental impact of transgenic fish was markedly less. In order to produce sterile growth-enhanced transgenic fish, we have induced triploidy in two lines of transgenic tilapia. Growth performance and gonadal development were analyzed following triploidization by heat shock. Ploidy status was confirmed by nuclear size measurement of erythrocytes. Erythrocytes of triploids were found to be 1.5 times larger than diploids. Observations of growth enhancement and gonadal development were made on diploids and triploids from both transgenic and nontransgenic full sibling batches. In both lines, transgenic diploids were superior in growth performance, followed by transgenic triploids, nontransgenic diploids, and nontransgenic triploids. Although the testes of transgenic triploids were significantly smaller than those of nontransgenic triploids and nontransgenic diploids, histologically they did not show signs of gross deformation. There were also some spermatozoa present in the testes of some triploids, which could be indicative of reproductive functionality. However, the ovaries were devoid of oocytes, underdeveloped, and deformed in all triploids and were completely nonfunctional. Although the best growth performance was shown by the fertile diploid transgenics, the triploid transgenic females could offer a good option for aquaculture purposes because they showed superior growth performance over the normal wild-type tilapias with the advantage of sterility to ensure nonhybridization and noncontamination with the local gene pool. However, careful monitoring of potential gene flow would be required prior to commercial use.

Isolation and characterisation of tilapia β-actin promoter and comparison of its activity with carp β-actin promoter

The regulatory sequence including proximal promoter, untranslated exon 1 and intron 1 of the β-actin gene from tilapia (Oreochromis niloticus) has been isolated and spliced to a β-galactosidase reporter gene to test its activity. Comparisons of promoter activity have been carried out with three different constructs: (1) 1.6 kb tilapia β-actin regulatory sequence, (2) 1.5 kb carp β-actin regulatory sequence, and (3) 4.7 kb carp β-actin regulatory sequence. Although the 1.6 kb tilapia β-actin regulatory sequence gave slightly different expression patterns in tilapia embryos assayed by in situ X-gal staining, no difference was observed in expression level when the tilapia sequence was compared with the 4.7 kb carp β-actin regulatory sequence by quantitative assay. In comparison with the 1.5 kb carp β-actin regulatory sequence, the 1.6 kb tilapia β-actin regulatory sequence gave higher expression levels in tilapia embryos, while a reverse result was observed in zebrafish embryos. In cell transfection experiments, the 1.6 kb tilapia β-actin regulatory sequence showed three to four times better activity in blue gill cells than either the 4.7 kb carp β-actin or the 1.5 kb carp β-actin regulatory sequences. The 1.6 kb tilapia β-actin regulatory sequence also drove higher reporter gene activity in somatic cells of tilapia than did the 4.7 kb carp β-actin regulatory sequence following direct injection of constructs into muscle. Therefore, taken together, the data demonstrate that the tilapia β-actin promoter can be used as an efficient regulatory sequence to produce autotransgenic tilapia.

Copy number related transgene expression and mosaic somatic expression in hemizygous and homozygous transgenic tilapia (Oreochromis niloticus).

Three lines of transgenic tilapia (Oreochromisniloticus) fish were generated with a constructcontaining a lacZ reporter gene spliced to a 4.7 kb 5′ regulatory region of a carp beta actin gene. All these three lines contain different copy numbers oftransgenes and the levels of lacZ expressionwere found to be related to transgene copy number.Mosaic patterns of somatic lacZ expression wereobserved in these three lines which differed between linesbut were consistent within a line. We also observedthat expression of the reporter gene in homozygoustransgenic fish was approximately two-fold greater thanin the hemizygous transgenics. Analysis of expressionof the reporter gene on a tissue-to-tissue basisdemonstrated that lacZ expression of thereporter gene in stably transformed fish occured withvariable intensity in different organs and tissues andwas also sometimes variable in different cells of thesame tissue in G1and G2 generations of the transgenic lines.

Fishmeal replacement with Spirulina Platensis and Chlorella vulgaris in African catfish ( Clarias gariepinus ) diet: Effect on antioxidant enzyme activities and haematological parameters

This study explored fishmeal replacement with two freshwater microalgae: Spirulina Platensis and Chlorella vulgaris in African catfish (Clarias gariepinus) diet. The effect of inclusion of the two microalgae on biomarkers of oxidative stress, haematological parameters, enzyme activities and growth performance were investigated. The juvenile fish were given 3 distinct treatments with isonitrogenous (35.01-36.57%) and isoenergetic (417.24-422.27 Kcal 100 g-1) diets containing 50% S. platensis (50SP), 75% S. platensis (75SP), 50% C. vulgaris (50CL), 75% C. vulgaris (75CL) and 100% fishmeal (100% FM) was used as the control diet. The result shows that all the diets substituted with both S. platensis, and C. vulgaris boosted the growth performance based on specific growth rate (SGR) and body weight gain (BDWG) when compared with the control diet. The feed conversion ratio (FCR) and protein efficiency ratio (PER) was significantly influenced by all the supplementations. The haematological analysis of the fish shows a significant increase in the value of red and white blood cells upon supplementation with 50SP and 50CL but decrease slightly when increased to 75SP and 75CL. Furthermore, the value of haematocrit and haemoglobin also increased upon supplementation with 50SP and 50CL but decrease slightly when increased to 75SP and 75CL. The white blood cell (WBC), red blood cell (RBC) increased, while total cholesterol (TCL), and Plasma glucose levels decreased significantly upon supplementation of algae. This is a clear indication that S. platensis and C. vulgaris are a promising replacement for fishmeal, which is a source protein in the C. gariepinus diet.

Potential of field crickets meal (Gryllus bimaculatus) in the diet of African catfish (Clarias gariepinus)

ABSTRACT This study was conducted to evaluate the effect of dietary replacement of fishmeal (FM) by using field crickets (CM) and on growth performance and feed utilization of African catfish fingerlings. Five isonitrogenous diets (28% crude protein) were used containing 0% (control), 25%, 50%, 75% or 100% of FM substituted by CM. Triplicate group of fish (n = 15) were fed with their respective diets with initial mean body weight (BW) of 4.00 ± 0.8 g (mean ± SE) for 56 days. Fish fed with 100% CM exhibited significantly lower food conversion ratio than the lower inclusion level. Values of specific growth rate and protein efficiency ratio increased gradually with increasing amount of CM inclusion level from 50% to 100%. All compounds of essential amino acids were present in experimental diets although methionine, lysine and tryptophan were comparatively less than the required amount of amino acid for African catfish. Whole-body crude protein composition was significantly higher in fish fed with diet 50% to 100% CM compared to initial fish. These results indicated that CM is capable of serving as an alternative protein replacement for FM in the diet of farmed African catfish up to 100% without affecting body composition and feed utilization.