Department of Zoology Vidya Bharati Mahavidyalaya, Amravati University, Amravati, India

Article Publishing History

Introduction

Fish is widely used throughout the world, as a good source of high value protein; it is also useful in lowering of blood cholesterol level. Fish contain significant amounts of essential amino acids, especially lysine. Therefore, fish protein may be used to complement important amino acids and also to improve overall protein quality of a mixed diet (FAO, 2005). Fish products comprise an important ingredient in the human diet to upgrade their nutritional standards. Nutritional value of fish obviously depends on their biochemical composition (Prado, et al., 2009). The health benefits of fish oils in prevention of cardiovascular diseases through modifications of risk factors like hyperlipidemia, hypertension, and secondary prevention following myocardial infractions have been reviewed (Calder, 2004).

Fish eggs also have a good source for human nutrition due to their therapeutic role in reducing certain cardiovascular disorders (Stickney and Hardy, 1989). Varying egg quality is a limiting factor for successful mass production of fishes. The problem of varying egg quality, however, has received little attention. Appropriate quality of criteria has been difficult to identify because of limited knowledge (Kjorsvik et al., 1990). The biochemical composition of eggs is one of the factors determining egg quality since eggs must contain all the nutrients required for normal development during embryonic and yolk-sac larval stages. Several nutrients such as vitamins and essential fatty acids (EFA) have been suggested to be related to egg quality in both freshwater and marine fishes (Takeuchi et al., 1981; Watanabe 1985; Soliman et al., 1986 Foley et al., 2016).

More information on the relationship between egg composition and egg quality is needed for the improvement of egg quality (Watanabe et al., 1984). Apart from this the study of RNA:DNA ratio of eggs is equally important to know the nutritional status of eggs as well as physiological condition of the fish itself in particular water body. Required optimum ratio of RNA: DNA present in fish body part or in spawned eggs is indication of good productivity of water body.

Materials and Methods

The two species of genus, Pangus (Pangasius buchanani) and Hilsa (Tenualosa ilisha) respectively, were considered for study of biochemical compositions of its eggs. The eggs of fish Pangus and Hilsa were collected for study from the fish market of Amravati city. 250 grams of eggs were collected from each fish. Then the eggs were stored in deep freezer at -15oC in separate plastic bottles and out of these some were kept in 1ml tubes, which were stored in quick freezers up to -20oc. The samples were taken accordingly from sample tubes at the time of biochemical experimentation. Total protein was estimated by Lowry et al., (1951). Total carbohydrate by Bligh and Dyer (1959) and total lipid by Dubois et al., (1956). Extraction of RNA and DNA was done by the procedure of Halliburton et al., (1965) method. Estimation of RNA was done by orcinol method of Ashwell (1957) and estimation of DNA was done by diphenylamine method of Burton (1956). Values are expressed in mg/100mg for protein, carbohydrate, and lipid and μg/100mg for RNA and DNA. Estimation of minerals (Sodium and Potassium) was done with the help of flame-photometer

Results and Discussion

An egg needs all the necessary information to direct the development; it needs all the amino acids, lipids and carbohydrates, together with calcium (for bones), vitamins and metals for enzyme and other metabolic actions. These specialized materials are derived from number of maternal sources and are incorporated during the growth of the oocyte in the ovary. If an egg does not contain a particular compound, or contains an inappropriate amount of the compound, it will not be able to sustain development of a viable embryo. Hence mature egg contains these essential compounds in high amount.

Table 1: Biochemical Composition of Macromolecules
Sr. No.	Name of species	Protein mg/100mg	Carbohydrate mg/100mg	Lipid mg/100mg
1	Pangus (Eggs)	40	0.49	4.02
2	Hilsa (Eggs)	27.7	0.35	5.24

RNA-DNA ratio can be considered as a measure of the amount of protein synthetic machinery per cell, since the DNA content of an organism is an indicator of cell number. Therefore, the direct positive relationships between, RNA-DNA ratio and growth rate observed in this study is as per expectation. Positive correlations between RNA-DNA ratio and growth rate have also been observed for adult (marine fish), golden shiners (Bulow, 1970). RNA:DNA analyses may be most useful for assessing the condition of fish larvae susceptible to entrainment, evaluating whether fish larvae are likely to die from natural processes independent of entrainment, or assessing the relative condition of fish larvae which are still alive immediately following entrainment (Foley et al., 2016).

Higher RNA tissue concentrations at lower temperatures may be a compensatory mechanism for lower RNA activity, (Goolish et al., 1984). In this study it was seen that RNA/DNA ratio of fish eggs were comparatively more than 1.5. It indicates that there will be the need of large amount of proteins for the hatching of eggs and the production of healthy new young ones. These results show that there would be the good food availability for these fishes. Protein relation to RNA/DNA ratio derived from present study indicate good development. Response of the protein and RNA/DNA ratio to the feeding conditions was significantly observed (Akarte et al., 2014).

Table 2: Biochemical Composition of Micromolecules
Sr. No.	Name of species	DNA µg/100mg	RNA µg/100mg	RNA: DNA ratio	Sodium µg/100mg	Potassium µg/100mg
1	Pangus (Eggs)	0.39	0.63	1.61	0.91	0.84
2	Hilsa (Eggs)	0.41	0.66	1.6	0.98	0.91

Determinations of RNA and DNA can be used as biochemical indicators of recent growth rates of fish within each time period; RNA concentrations increased somewhat with higher feeding rate and faster growth. DNA concentration, however, increased with greater weight loss and longer periods of food deprivation. The slight decrease in DNA with increased growth and the slight increase in DNA with increased weight loss were probably due to changes in cytoplasmic volume. It was observed that food deprivation, other cellular constituents are metabolized and DNA is preserved (Leslie, 1955).

Figure 1

 

Figure 2

In the current study, the biochemical composition of fish eggs of Hilsa and Pangus were observed. The bio-molecules of these eggs which were being under consideration were proteins, carbohydrates, lipids, minerals, and nucleic acids (RNA and DNA). These bimolecular components show the status and productivity of an organism. In this study, it was shown that the concentration of protein was in the range of 27.7mg/100mg for Pangus fish and 40.0mg/100mg tissue in Hilsa fish. Amount of protein shows the availably of food through productivity of water to the organism. Finding which is at variance with a recent suggestion are free amino acids may serve as the sole substrate for aerobic energy metabolism during embryogenesis in species, (Fyhn
et al., 1986). So, higher values of protein quantity suggest good nutritional quality of fish eggs as human food.

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