Hybridization in fishes

2.  INTRODUCTION
 TYPES OF BREEDING
 ARTIFICIAL BREEDING
 NATURAL BREEDING
 DIPLOID HYBRID
 TRIPLOID HYBRID
 INTER GENERIC
 INTER SPECIFIC
 FISH
 ADVANTAGES &DISADVANTAGES OF
HYBRIDIZATION
 CONCLUSION

3. Hybridization is the act of breeding between two species /genera
,which ordinarily are not interbreeding.
Most fish , however shed their gametes (egg and sperm) in water and
fertilization is external . It is because of that fish hybridize more
frequently than tetrapods. It is therefore not surprising that a natural
hybridization is very common among fish, particularly among closely
related families which share common habit and habitat requirements .
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 .

4. Hybridization natural or artificially induced
,results in an embryo which resembles neither
one parent nor the other parent but posses
characters which are intermediate between the
characters possessed by the two parents . This
embryo is called a hybrid . The hybrid may be
diploid or triploid .

5. Breeding behavior varies in fish from once in life
time (0ncorhynchs) to once in a year (many major
carps and most other fish) or monthly (lebistes) or
continually throughout the year (cyprinus carpio) or
once in ten to fourteen years (Anguilla).
For Indian major carps breeding is seasonal (once
in a year) coinciding with rain and flood , which
offer greatest opportunity for survival and
development of the progeny.

6. ENVIROMENT STIMULI
↓
RECEPTORS
↓
BRAIN CENTERS
( hypothalamus)
↓ regulation
Pituitary gland
↓ release pituitary extract
(Gonadotropin hormone)
or
Gonadotropin synthetic hormone /
natural substitute
Hormone ↓
↓ gonad
Gonad spawning breeding
↓
Spawning
Natural breeding

7. Cross between two different species result in
diploid hybrid . Which are viable and so fin
application in fish culture to the new
combination traits both inter specific and intra
generic hybrid have been achieved in India .
which attain maturity and are capable of
producing in generation .

8. The triploid hybrid by chromosomal maniculation
Which include the following .
1. By inter generic mating between a diploid female of another of one
species and triploid male of another species .
2. By subjecting the normally fertilized a involve in artificial in sanitation
off egg of one species by sperm of another species to head or cold .
3. By subjected the fertilized a involve in the egg one species with the
sperm of another species to action of an antibiotic colchicum with are
mitotic inhabitation . The triploid may viable but are sterile however
the triploid growth faster than either diploid parent and so find use in
fish culture in a monsoon mono sex culture system .
hybridization of two types
a. Inter specific hybridization
b. Inter generic hybridization

9. 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 :- example
Male female results
Labeo rohita Labeo calbasu rohu calbasu
Labeo calbasu Labeo rohita calbasu rohita
Labeo bata Labeo rohita bata calbasu
Labeo bata Labeo calbasu bata calbasu
Labeo calbasu Labeo genius calbasu genius

10. Extensive 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:-example
Male Female Results
Catla catla Labeo rohita Catla rohita
Catla catla Catla mrigala Catla mrigala
Laboe rohita Catla mrigala Rohu mrigala
Laboe mrigala Laboe calbasu Mrigala calbasu
Cirrihinus rewa Labeo rohita Rewa rohu

11.  A technique used to detect the presence or absence and
location of specific gene sequences
-- chromosomal deletion, amplification, translocation.
 Each fluorescently labeled probe that hybridizes to a cell
nucleus in the tissue of interest will appear as a distinct
fluorescent dot
 Diploid nuclei will have two dots
 If there is duplication in the region of interest,
the gain will result in more than two dots.
 If there is a loss in the region of interest,
one or zero dot will result
Schematic diagram for FISH technique

12.  Can be used in formalin-fixed, paraffin embedded sections
or fresh frozen tissue
 Possible correlation between FISH result and tumor
morphology with conventional light microscopy
 Allows simultaneous interrogation of multiple cytogenetic
signatures
 Can be used either in bulky tumors or tumors where the
malignant component contributes to a small proportion of
the overall cellular population

13.  FISH is a technique used to visualize specific cytogenetic
abnormalities
 It can serve as a supplementary diagnostic tool in
pigmented lesions. However, should not be used as a
stand-alone test
 Cannot replace traditional histopathologic analysis
 FISH result must correlated with clinical, pathologic and
molecular information.

14.  ADVANTAGES:-
1. We get different types of animals(fish) and
organisms.
2. Can get healthier animals(fish) and organisms
 DISADVANTAGES:-
1. Some animal(fish)can become extinct
2. Some animals(fish)could be prone to more diseases.

15. Hybridization is when two closely related fish species,
for example fishes come into contact and can mate
successfully and reproduce. Hybridization creates
problems for taxonomists ( the branch of science that
is concerned with classification). Hybridization is a
sign of continuous process of speciation or formation
of new fishes.