EFFECT OF ALBINO GENE ON INTRASPECIFIC HYBRIDIZATION OF NORMAL AND ALBINO AFRICAN CATFISH (CLARIAS GARIEPINUS)

CHAPTER ONE

1. INTRODUCTION

1.1 BACKGROUND OF THE STUDY

The demand for high quality protein especially from aquatic resources is rising, Clarias gariepinus is the most common and have received much attention because of its economic importance and high rate of success in rearing them (Adewolu et al. 2009). Albinism in catfish is the best known potentially valuable qualitative traits and inherited as a single homozygous recessive trait (Bondari, 1981). The term albino catfish can refer both to an albino specimen of any catfish species or to a particular species of catfish the Albino Clarias gariepinus Catfish (Westerman and Birge, 1978). Albino specimens of all catfish species including the Albino Clarias dramatically, increased agricultural production is clearly needed to meet this demand in the future, because capture fisheries is showing precipitous disclose due to over fishing habitat, destruction and increasing population and increased in capture fisheries are not anti-coopted under the current global condition (Dunham et al. 2001) the most current advance in aquatic production have been achieved through the application of genetic principles which includes selective breeding, hybridization, chromosome manipulation, sex reversal and gene transfer (Aliah and Taniguchi 1999). Framed sources are economically important food fish which have gained much prominence species of Claria sand Heterobranchus are widely cultured (Huisman and Richter, 1987). They are characterized by hardiness, resistance to diseases, high yield potentials and ability to grow on a wide of nature and low cost ratification food and can withstand low oxygen and wide pH levels (Fagbenro and Sydenham, 1991). Genetic techniques have been applied to other animal to improve their qualify but that of fish is not yet fully exploited. Failure to pay attention to the genetic aspect of fish husbandry may result to decline in productive as inbreeding or other genetic consequences of mis-management may result in slower growth, decreased viability and disease susceptibility as well as decreased egg production (Bartly et al. 1990). Hybridization has been found to be a breeding programme that tries to find mating combination between different population of fish which produce hybrid vigor (tave, 1993). Hybridization has been used to increase growth rate, manipulate sex ratio, produce sterile animals, improve flesh quality, increase resistance and to tolerant to environmental extremes as well improve a variety of other    traits that make other aquatic animals production more profitable (Dunham et al. 2001). Intraspecific hybrids are produced when useful traits in parent fishes are transferred to the offspring, this is because for back cross hybrid produce from the fertile hybrid could not be easily differentiated from the pure parents (Aluko, 1996). The hybrid cross between Heterbranchus and Clarias Species is receiving attention in Africa particularly Nigeria this hybrid had been repeated to show that Heterobranchus species usually grow larger than the Clarias species,therefore shows better percentage survival (Madu 1995). This calls for the need to carry out more details investigation on hybridization among the Clarias spcies in order to assess the aquaculture potentials of their hybrid s in terms of growth performance and survival compared to the putative parents at the fry, fingerlings and adult stage (Onyia, 2010). Clarias gariepinus is an economically important fresh water species of the Clariidae family that contribute immensely to the annual fresh water fish production in Nigeria. They are also readily acceptable among Nigerians fish farmers and consumers, hence command high commercial value (Adebayo et al. 2001). They are commonly referred to as mud fishes or African catfish in various parts of Nigeria and are important source of animal’s protein. Among the freshwater species for culture in Nigeria gariepinus is a natural occurring phenomena and that there has always been albino Clarias gariepinus even if only a few survived to become adults. An albino specimen of any of the larger catfish species can be a truly magnificent sight, such as large albino catfish (Groblan et al. 1992). The inheritance of albinism has been analyzed in many aquarium fish and several aquaculture species-Rainbow trout, channel catfish and Grass carp (Delgado et al., 2009). In all the traits of the regular clarias gariepinus plate i and ii. They have the same well testing meat, and they grow up to the same size (Britton and Davie, 2006). However, the albino form of this catfish has some additional values. The Albino from of the catfish is an appreciated aquarim fish and can be sold in large quantities to aquarium stores (Galib et al., 2012). Albino catfish are also preferred by some to stock fishing lakes with, since the albino catfish are more easily spotted and allows the fishermen to see that there are fish in the lake even if they are unsuccessful in catching any (Clark, 2002). There is no doubt that commercial breeding of catfish in captivity has increased the amount of Albino catfish available both in the aquarium trade and in the wild as a result of different restocking efforts (Piorski, 2010). Albinism is passed genetically from parents to offspring (Dobosz et al. 1999). Each cell contains numerous pairs of genes, one from each parent. These genes transmit traits through generations. An albino offspring results from a specific combination of genes (Rothbard and Wohlfarth 1993). Albinos are not in frequent because the genes for that trait are recessive, while the genes for normal pigmentation are dominant (Rothbard and Wohlfarth, 1993). If both are present, normal pigmentation occurs. If only recessive genes occur, albinism may result. Only a small percentage of animals carry the recessive gene, so the chance of the pairing of recessive genes in an individual animal is slight. In natural environment, there are several reports of total or partial albinism in freshwater fishes and marine fishes (Piorski, 2010). Some cases of total or partial albinism in siluriformes have been reported, e.g., Ictalurus punctatus (Westerman and Birge, 1978), Schizolecis guntheri (Brito and Camaraschi, 2005). Intraspecific hybrids are produced when useful traits in parent fishes of the same genus are mated. Intergeneric hybrids on the other hand are generated when parents from two genera are crossed. All of the genetic information in an individual fish is contained in molecules of deoxyribonucleic acid. Molecules of DNA are composed of sub units called nucleotide. Each nucleotide contains a compound called a nucleotide. The bases are four kinds of nucleotides in DNA because there are four different bases (adenine, guanine, thymine and cytosine). DNA molecules consist of a long ladder of paired nucleotides. The helix in the ladder gives the DNA molecule a double helix structure. Nucleotides form base pair in the double helix in a specific manner where thymine is found in one strand of the helix, only adenine will be found in the same position of the opposite strand. Similarly, where guanine is found in one of the chrosome strands, only cytosine will be found in the same position of the opposite strand. The two strands of the helix are said to be complementary because of the way nucleotides form base pairs (Westerman and Birge, 1978). Whenever a cell divides, the DNA must be replicated in order to provide each daughter cell with a complete set of genes. An advantage of complementary base pairing is evident during replication of the DNA molecule. During replication, the two strands of the DNA helix are separated by enzymes so that each strand is available to serve as a template for a new molecule. Individual nucleotides are affixed to each template. Two complete and identical DNA molecules resulted, the complementary pairing of bases ensures that the replication of DNA is essentially error free. Microsatellitesrepresent another type of repetitive DNA (Westerman and Birge, 1978).

Microsatellites, also called Simple Sequence Repeats (SSRs), are composed of tenderly repeated 2-6-base units (motifs)., the allelic variability of microsatellites is based on the difference in the length of fragments caused by the different number of repeated units. The isolation of microsatellite loci from a genomic library for a new species or group of species is the first step for the investigation of microsatellite polymorphism (Calcagnotto et al. 2001). The sequence information for the flanking DNA is needed to allow the synthesis of specific PCR primers. Following primer design, products can be amplified and separated through capillary electrophosatellites are locus-specific and co dominant markers (Calcagnotto et al. 2001).

Microsatellites are also highly variable, and the number of alleles for one locus may be more than 30. Heterozygote for microsatellite loci has two bands on a gel which represent two alleles while homozygote has one band (one allele). Microsatellite alleles are designated by numbers which indicate the size of corresponding PCR product in base pairs (Taniguchi et al. 1999) the first studies on application of microsatellites as genetic markers in fish were published in the beginning of the 1990s. From this time, microsatellites were identified and analyzed in many important fisheries and aquaculture species (Sirol and Britto, 2006). Funkenstein et al. (1990) documented that very high variability, discrete character of inheritance, co dominance, and established standard techniques for their analysis, microsatellites are regarded now as the most popular and powerful type of DNA markers in fish genetics.

1.    Statement for the Research Problem

In Nigeria and other developing country, there is little information on the effect of hybridization of Albino and Normal catfish Clarias gariepiunus the hybrids have been reported to show heteroses (Salami, et al. 1993, Aluko, 1999) but their suitability for aquaculture has not been thoroughly evaluated. There is also little information in literature on the growth and viability, hatchability, latency period, fecundity, fertility, fertilization, morphometric and meristic characters and colour ratio of the mating combination as well their gene characterization of the intraspecifichybridization of normal and albino Clarias gariepinus, The work of Onyia et al. (2016) documented the growth and survival of Normal and Albino Clarias gariepinus that the normal Clarias gariepinus grow faster than the Albino C. gariepinus, hence there is need to assess the viability, latency period, fertility, fecundity, morphometric and meristic character, color and sex ratio as well their genetic characterization of the intraspecific hybrids of normal and Albino Clarias gariepinus in F1 and F2 which were lacking in their reports.

1.3       Justification for the Study

Production and culture of species of the catfish belonging to the Claridae family is fast growing globally according to (Adewolu et al. 2008). This study will be useful in assessing viability, growth performance, latency period, fertility, fecundity, fertilization, colour and sex ratio of the various intraspecific mating combination of Albino and normal Clarias both in F1and F2.

This study was initiated to provide detailed phenotypic appearance (morphometric and meristic character) description of the intraspecific combination of Albino and normal Clarias gariepinusin order to know the distinguish features for identification of their hybrids and their putative parent.

This study on intraspecific hybridization of Clarias gariepinus Albino and normal and their reciprocal hybrids is of great importance in ensuring a proper understanding of their gene characterization in both parent and F1 (Betiku and Omitogun, 2006) to create a good foundation for producing a genetically improved hybrid fish.

1.4   The Aims of the Study

The Aim of this study was to determine the effect of albino gene on intraspecific hybridization of normaland albino african catfish (Clarias gariepinus).

 1.5    The Objectives of the Study

i.        to determine the latency period of the female parent stocks of normal pigmented, albino

Clarias  gariepinus and the female of hybrids in (F1) generation of their crosses.

ii.      to evaluate the fecundity, fertility, and hatchability of eggs of different mating combination

 in (F1 and F2) generation of Clarias gariepinus.

iii.        to determine the percentage survival of F1 and F2 generation of Clarias gariepinus.

iv.        to determine the growth performance and feed utilization of F1 and F2 generation of the

 hybrids.

v.         to determine the morphometric and meristic characters of the F1 and F2 generation of

            Clarias gariepinus.

vi.        to access the genetic characterization of the parent stocks and F1generation

1.6       Research Hypotheses

i.          There is no significant differences (P>0.05) between the latency period and fecundity, of the parent stock and F1 of normal and albino C. gareipinus.

ii.         There is no significant differences (P>0.05) between the percentage fertility, fertilization, hatchability and survival of normal and albino Clarias gareipinus in F1 and F2.

iii.        There was no significant differences among the percentage survival of the offspring in F1 and F2.

iv.        The growth performance and feed utilization of normal and albino Clarias gareipinus in F1 and F2 doesnot differ.

iv.        The morphometric, meristic and genetic characterization of the parent stock and their hybridofnormal and albino Clarias gariepinus doesnot differ.

vi.        The phenotypic and genotypic appearance of hybrid of normal and albino Clarias gariepinus do not differ.

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