HYBRIDIZATION IN FISHES

BARKATULLAH UNIVERSITY BHOPAL M.P.PRESENTATION TOPIC

PRESENTED BY

ASIF KANTHM..sc IV SEM

SUBMITTED TO DEPARTMENT OF ZOOLOGY AND APPLIED AQUACULTURE

INTRODUCTIONHybridization IS THE ACT OF BREEDING between two species /genera ,which ordinarily are not interbreeding.It is well known that hybridization refers to cross-breeding between either members of different races or strains of the species (intra-specific);or between two species of the same genus (tnter-specific) and between species belonging to different genera (intergeneric ).Hybridization is usually aimed to combine positive traits of parent species in their hybrid offspring . The positive traits may include better growth , resistance to disease / changed environment , meat quality early or late maturity , better fecundity and so on.

INTERSPECIFIC HYBRIDIZATION

Interspecific reciprocal hybrids where produced among indian major carp by crossing labeo rohita with labeo calbasu these hybrid have been son some traits of interest for aquaculture i.e hybrid exhibited faster growth the hybrid the slow growing parents the calbasu.For :- exampleMale female resultsLabeo rohita laboe calbasu rohu calbasuLabeo calbasu labeo rohita calbasu rohitaLabeo bata labeo rohita bata calbasuLabeo bata labeo calbasu bata calbasuLabeo calbasu labeo genius calbasu genius

INTER-GENERIC HYBRIDIZATIONExtensive work has been carried out on tnter-generic hybridization among the species or three genera i.e catla labeo and cirrihinus as many as 30 / . inter generic have been produced and evaluated for their positive traits how ever only few of then .these found to posses some positive characteristics which are useful for aquaculture.For:-exampleMale Female ResultsCatla catla Labeo rohita Catla rohitaCatla catla catla mrigala Catla mrigalaLaboe rohita catla mrigala Rohu mrigalaLaboe mrigala Laboe calbasu Mrigala calbasuCirrihinus rewa Labeo rohita Rewa rohu

NATURAL HYBRIDIZATION IN FISHESIt confined to only inter-specific( It takes place in between the individual of the same species).Quite a number of inter-specific hybrids have been found to be viable and fertile.It is more common In freshwater fishes than in marine ones.it is believed that since the freshwater habitat provoides suitable conditions for that as compare to ocean.The reproductive isolation mechanism in fishes inhabiting freshwater have not yet been developed perfectely leading to higher frequency of hybridization in themthe frequency of natural hybridization in the fresh water fishes has increased due to various conditions

FACTORS PROMOTING NATURAL HYBRIDIZATION IN FISHES

01.BIOLOGICAL • External fertilization habit.• Behavioural isolation mechanism that prevent inter-specific breeding not

perfected in several group of fishes.02.PHYSICAL - Over-laping of spawning grounds of relatedspecies due to habitat changes by the construction of dams and canals.03.ANTHROPOGENIC- Purposeful or accidental introduction of non – native species.- unequal abundance of the males and females of a species due to fishing

pressure or other reasons.

ARTIFICIAL HYBRIDIZATION IN FISHES• IT is not restricted to inter-specific like the natural

hybridization ,Thus attempting artificial hybridization , it is important to gather knowledge on the taxonomy ,biology,karyology and the economic traits of the concerned species.• The two species chosen for the purpose of

hybridization should be taxonomically close .e.g breeding season should be overlaping, chromosome number should be same. However, species with dissimilar diploid chromosome number can also be hybridized in some cases but the the mortility rate is high in these cases.

WAYS BY WHICH ARTIFICIAL HYBRIDIZATION CAN BE CARRIED OUT•By Simple Cohabitation. (E.G Tilapia)•By Hormone Treatment And Co-habitation.(E.G

Catla,rohu And Mrigal)•By Hand Stripping.(E.G Cat Fishes

Heteropneustes,claris Etc )

OBJECTIVE

-TO BRING GENITIC MODIFICATION-TO GET DISEASE FREE HYBRID -TO ACHIVE GENOMIC CHARACTERSTICS,SURVIVAL,GROWTH,REPRODUCTIVE ABILITY AND SEX DISTRIBUTION IN THE F1 GENERATION.

CONCLUSION

•Here We Conclude That The Hybridization In Fishes Is More Benificient In Respect To Economic Traits And It Is Only The Way To Produce Desirable Traits In The Form Of Hybrids .•Moreover Hybridization Is A Detrimental Process

Since Two Incompletely Diverged Genomes Are Combined In The Hybrid,

•THANKS