ICT and My Specialization

Information and Communication Technology (ICT) is the study of the technology used to handle information and aid communication (FOLDOC, 2009). The phrase was coined by Dennis Stevenson in his 1997 report to the UK government and promoted by the new National Curriculum documents for the UK in 2000. ICT originally was another way to say Information Technology (IT).  Now that definition has expanded to include unified communication technologies (UC) and more.   ICT refers to the integration of telecommunications, computers, middleware and the data systems that support, store and transmit UC communications between systems (Murray, 2011).

ICT plays a vital role in research and development of any field. For instance, in the field of Fisheries particularly in Aquaculture, recent generated information published in the internet helps the local scientists to formulate new innovative ideas for the development and improvement of many aquatic species. In the technology “sex reversal”, scientists used many previous researches in order to determine the most appropriate concentration of hormone that will produce 100% or near 100% monosex population. The result of this technology was also published to contribute to the development of science in a wider scope. Furthermore, communication between countries became easier because of ICT. When a country needs some resources of another country (i.e Malaysia strain of tilapia was used in the development of the local tilapia strains in the Philippines), communication is possible through email which is very convenient and reliable.

Ideally, a fish species used in aquaculture must not reproduce in the culture environment before reaching market size because reproduction consumes a lot of energy which is supposedly be used in growing and early sexual maturity in tilapia culture is a well-recognized problem (Cagauan, et al., undated). One of the basic factors of tilapia aquaculture is that male fish grow bigger and faster than the females. There are several methods used to skew sex ratios and to increase the percentage of males in a population, one of these is sex reversal.

Sex reversal uses hormones to change females to males (masculinization) and males to females (feminization). As stated above, all male culture of tilapia is preferred because of their faster growth. Male tilapia on the other hand, are sex reversed to become female because feminization of genetically male tilapia offers the possibility of all male tilapia through a YY breeding program (Guerrero III & Guerrero, 1975). So basically, sex reversal is done to achieve one goal – to have an all-male culture of tilapia for better production.

Masculinization

A number of types of chemicals have been used to control sexual development in tilapia. Steroids are a group of lipids with several unique properties affecting growth and development. Steroids are called androgens if they are able to induce male characteristics and estrogens if they induce female characteristics. Testosterone is the widely used masculinizing agent in tilapia.

Sex reversal by oral administration of feed incorporated with methyl testosterone (MT) is probably the most effective and practical method for the production of all male tilapia. This is the most common method of sex reversal in the Philippines. However, the technique has some limitations such as the uniform age of fish that should be used at the first feeding stage to ensure high reversal rate; and less control of reversal efficiency especially when done in the natural environment where natural food is present. Moreover, widespread use of large quantities of sex reversal hormone in hatcheries may pose a health risk to workers and there is little information on the fate of the hormone in the effluent and ground water.

Aside from feeding feeds with hormones, sex reversal can also be done by immersion technique. Nile tilapia eggs immersed in 800 μg/l 17-alpha methyl testosterone solution for about 96 hours can yield up to 91% masculinization (Cagauan, et al., undated).  This technique may lessen the duration of treatment and lowers the cost of hormone used relative to the traditional technique of sex reversal by oral administration. The mechanism of action of the immersion technique is that the hormone is absorbed through passive diffusion across the lipid membrane of the eggs. Aside from eggs, Nile tilapia fry can also be sex reversed by exposing them in a hormone solution. A successful study by Gale, et al., (1995) showed that 3-hr exposure of O. niloticus fry at 10 and 13 days post fertilization in mestanolone at 500 mg/l produced greater than 93% male.

Feminization

Estrogens are those agents which induce feminization. Estrone and 17 beta-estradiol are 2 natural steroidal estrogens found in the ovary of tilapia. Synthetic estrogens, such as ethynylestradiol and diethylstibestrol, are more potent than natural estrogens when given orally. This greater activity is due to their stability in the digestive tract and the liver (White, et al., 1973).

Feminization has almost the same procedure as masculinization. It is also done by oral administration by feeding feeds with hormones. Young fish are fed with estrogen. This results in a population of all female fish. The morphological female but genetic male fish are then reared to maturity and then mated to normal male fish. The resulting fry have a male father and a male mother and thus will all be male. These young have never been treated with any hormone. Of course this technique requires several years to develop the stocks and extensive progeny testing to determine which fish produce the all-male young (Fitzsimmons, undated).

As aquaculture continues to supply an increasing portion of the world’s fisheries products, tilapia culture will play a more important role. Sex reversal will remain the industry standard for reproduction control in tilapia.