What is monosex culture.Why?

Mono Sex Culture:Mono-sex culture is based on the culture of fish by producing all males or all females depending upon

the sex which have better food conversion ratio and growth rate. Sex of fish genetically is determined

by the sex chromosomes (X, Y, Z, or W). The male determining gene M is present on any of the three X,

Y and W. in XY mechanism, the females are XX and males are XO. Some species have ZZ female and ZW

male. In platy fish there are 3 sex chromosomes – X, Y and W; XX, WX and WY are some combinations.

what is monosex-techcolumnist

Mono-sex culture,Monosex Culture and Sex Reversal in Fishes,WAYS TO PRODUCE MONOSEX CULTURE,Techniques of producing monosex or sterile population of fish.tech science,biology

However for all male or female productions the flowing procedures are maintained –

The sex of fish is identified before maturity and male and females are separated. The process is

laborious. Desired quantity of male or females are not produced by that process.

Experimental hybridization in Tilapia can produce monosex stock. Inter specific and intra specific

mating yields monosex male stocks as follows

♂ T, macrohir × ♀ T. nilotica

♂ T. hornorum × ♀ T. mossambica

♂ T. mossambica × ♀ T. nilotica

♂ T. mossambica (African) × ♀ T. mossambica (Malaysian)

Treatment with sex hormones: It is another easiest way, when male sex hormone methyl testosterone

is administered through feeding in early developmental stages of female fish. The genotype female

(XX) then transferred to phenotype male (XX). If such sex reversed male are crossed with normal

female, the progeny will be 100% female. The gonads of fish (teleost) are undifferentiated at early

stages of maturity and it can be triggered to produce male or female gonads by that process.

Sex reversed male (XX) × Normal female (XX)

↓

Female (XX) ……. F1

The hormone treated sex reversed male are generally not fit for human consumption. But F1 progeny is

normal female and suitable for human consumption. But sometimes the culturist does not produce F1

progeny to produce only male population. In case of Tilapia the little amount of methyl testosterone

(15-60mg/kg of food) is administered. The drug is given for 30-50 days of life, during which gonadal

differentiation takes place. The uses of estrogenic steroids are not successful. However the production

of all females has been attempted in salmon and trout. Oral administration of 17-ß estradiol at

20mg/kg of food is given to the juvenile trout & salmon up to 60 days resulted sex reversal of males to

females. In pacific salmon (Onchorhynchus spp.), the immersion of young fish in drug as well as feeding

appears to be necessary for sex reversal.

Necessity of Monosex Culture:

Some time one sex of certain species has better growth rate and food conversion efficiency. To culture

that sex (male/female) monosex culture is essential. For example we can say that the male Tilapia

grows faster than female, then the culture of male is beneficial in case Tilapia.

When the fecundity of certain species is very much high and if they can breed in captivity without any

inducing agent, there is the possibility of overcrowding of fish, which leads to stunted growth (due to

the prolific reproduction e.g. Tilapia).

The production of monosex fish is easier than the production of sterile fish, so in commercial purpose

generally monosex cultured is mostly prefer.

Example of Monosex Production in Nature:

According to recent report, the flat fish population in the estuary of British River Tyne, a heavily

polluted river, was found more than 50% of males possessing abnormal testes. The tendency of their

sex change from male to female was probably due to the female hormones. But the actual reason and

mechanism of the action is not known.