1. KASHMEERA.N.A
III SEM MSc ZOOLOGY
ROLL NO:37
CHRIST COLLEGE

3. Selection
Goals
Prerequisites
Methods

4. Successive choosing of the best varieties from the available
lot by nature or man.
The aim of a breeder - to get maximum profit possible
the genetic worth of the stock by selection.
Based on a single desirable trait or combination of traits.

5. growth rate, by better utilization of food
natural food in ponds ; food mixtures
resistance to deviations from the normal environmental
conditions - oxygen deficiency,
high or low temperature,
higher salinity etc
resistance to infectious diseases
to infestation with parasites
the nutritive properties of fish.

6. 1. Specifically define - the breeding goal i.e. the trait under selection
2. The entire life cycle of the animal should be under control.
3. It should be possible to hold and individually evaluate a number of
generations in identical rearing systems.
4. Establish relative economic value of the traits that are to be selected
5. For the selected traits, the phenotypic (VP) and
genetic variances (VG),
heritabilities etc should be known.
VP = VG + VE

7. Mass selection
Genotypic selection
Family selection
Sib – selection
Selection by progeny testing
Combined selection

9. • Character/ Individual selection
• Individuals selected from mixed population
on the basis of phenotype.
• Genotype may be unknown.

10. Response (R) = i x σ x h2 = S x h2
• i = intensity of selection
•  = degree of variation in the trait
• h2 = heritability
• S = Selective differential
• Response α heritability
• h2 = R/S

11. METHODS TO RESPONSE
• i / σ / h2
• ↑ intensity of selection(i)
↑
no. of individuals grown → ↑ severity of
selection
• Variability (σ ) ↑
only genetic variation important
envtal - useless - ↓ heritability

12. Heritability ( h ) 2
• Outbreeding – cross non related
individuals → ↑degree of heterozygosity
i.e. ↑ in genetic variation
• Inbreeding ↑ homozygosity

13. ADVANTAGES OF MASS SELECTION
• Simplest & common method
• Characteristic to be improved easy to
measure
• Can be used efficiently in selection
for growth rate
for age at maturity

15. • To overcome disadvantages of mass
selection
• include – family selection
progeny testing

17. • For selection of characteristics of low
heritability - survival,
meat quality,
age at maturation
• Families grown in identical conditions
↓
Compare & select best

18. Response eq. ~ mass selection
~
• Rf = if x f x h2f
• i < mass selection – not possible to grow large
no. of families.
• reduction in  - denotes variation in family
not individual variation
• h2 much higher

20. • If individuals from best family sacrificed for examination
– use brothers & sisters for breeding
• Use full & half siblings
• Advantage – generation interval not ↑ like mass selection
• Disadvantage – each family - separate tank - marking
difficult - envtal & tank effects on characters b/n families.

22. • Enables assessment of breeding qualities
of separate spawners/pairs of spawners &
selection of best
• 3 methods
I.Testing pairs (not separately)
II. ,, spawners of one sex
III. ,, both ♀♀ & ♂♂

23. Advantage of PT
• permit evaluation of separate spawners &
selection of best

25. • Mass selection more efficient
• Genotypic selecton advantageous for
certain characters – fat content
• For characters like weight – combined
selection
• CS sum up efficiencies of mass &
genotypic selection in short time.

26. CS consist of:
• Performing mass selection amoung fingerlings
• Progeny testing of males
• Family selection with simultaneous breeding of
5-10 families
• Repeated performance of mass selection in the
best families

28. It is the technique of breeding of fishes of two species or genera which
ordinarily do not breed.
Fish - external fertilisation - Fish hybridizes more frequently than
tetrapodes
Naturally hybridized fishes - Cyprinidae , Salmonidae etc
Hybridization - ↑ hybrid vigour / heterosis
Hybrids – fertile/sterile – must be verified before introducing to natural
envt.
Indiscriminate hybridization → contamination of genepool.
Interspecific & intergeneric hybridizations

29. INTER SPECIFIC HYBRIDIZATION
female Labeo calbasu Labeo rohita
produced by mating between two different species in same genus.
In India mating female kalbasu and Labeo rohita was highly successful.
Over 94% fertilisation was obtained.
The growth rates of hybrids are superior to the parent Kalbasu.
It attains maturity in two years.

30. INTER GENERIC HYBRIDIZATION
• male and female are selected from different genera
• Catla catla Labeo rohita
• Inter generic hybrids between Catla and Rohu attains full maturity in
3yrs
.

31. Intergeneric hybridization
Labeo rohita Cirrhinus mrigala
Crossing between Rohu and Mrigal is more successful
and 90% fertilisation is done and
hybrids attain full maturity in 2yrs and
showed intermediate character

32. Intergeneric hybridization
Cirrhinus mrigala Labeo calbasu
Mrigal-Kalbasu hybrids attain full maturity within 2-3yrs.
These hybrids are also capable to produce new ones.

34. • In fish farming, if proper care is not taken the fishes can breed with
their close relatives or same parental generation – INBREEDING
• cause early mortality of fish, poor growth rates and other genetical
abnormalities – INBREEDING DEPRESSION
• Inbreeding →reduction of desirable traits and fertility.
• If a farm based on limited number of population of brood stocks the
progeny over long periods can face inbreeding problems.

35. The advantage of inbreeding:
• Production of inbreed lines are useful in improvement of
stock
• To produce pure lines of fish
Pure lines of strains are used for perfect hybridization of
fish to obtain favourable heterosis, monosex.
· Pure lines help in gene mapping
· To determine
1. Phenotypical variations
2. Extent of inbreeding depression
3. chromosomal makeup to the fish

36. Crossbreeding is the solution of inbreeding depression,
the fishes are allowed to breed with different breed varieties, strains or
genotypes of farmed species
the aims of cross breeding
to achieve
· Better growth rate
· Better desired qualities
· Increase the survival rate
• lower the early stage mortality

37. · By chromosomal manipulation –
Gynogenesis or Androgenesis
· Hormonal manipulation – Feminisation or
Masculisation
· By genetic engineering – trangenesis or
mutation

38. Gynogenesis
• process to produce individuals from maternal chromosomes only eventually
to obtain homozygosity.
• Parthenogenetic devpt of eggs after activation with genetically inert sperm
• Gynogenesis in fish farming is used to form inbred lines to achieve proper
hybridization and selective breeding.
Methods:
Sperm nucleus is inactivated prior to fertilization by use of X-Rays,
chemicals – dimethyl sulphate.
• eggs are exposed to sub lethal temperature shocks before or after
fertilization - suppress the meiotic divisions of eggs i.e. ensuring the non
reduction of nuclear components.
• Upon fertilisation the resulting diploid individuals retain the second polar
body nucleus (maternal) besides the egg nucleus,

39. gynogenesis- preventing the extrusion of second polar body
Activation – irradiated sperm
Egg
Shock treatment and retention
n
of 2nd polar body n 2nd polar body
Homozygous diploid 2n
Gynogenetic progeny
•In India Gynogenesis are tried on Indigenous as well as Exotic carps.
•Eggs of rohu are fertilised with irradiated sperms of Catla and then
exposed to cold 12°C and heat 39°C shocks to obtain gynogenetic rohu.

40. ANDROGENESIS
• Development of an organism with only
paternal genes
• androgenesis is development of an
embryo from a fertilised egg from which
the nucleus has been removed.
• The embryo therefore contains only
paternal genes.

41. The method of dispermic androgenesis, developed
androgenesis
for sturgeon fishes, includes genetic inactivation of
eggs, their insemination with concentrated sperm (to
cause polyspermy), and heat shock to facilitate the
fusion of male pronuclei.
The restoration of the diploid state of androgenotes
by fusion of two sperm nuclei allows androgenetic
progeny to have a heterozygosity level similar to that
in a regular crossing.
endangered sturgeon fishes may be recovered by
means of dispermic androgenesis if the sperm alone
of a given species is available.

42. Mono Sex Culture

43. 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.
Experimental hybridization in Tilapia can produce
monosex stock
Treatment with sex hormones : sex reversal

44. 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 - male Tilapia grows faster than female
-culture of male is beneficial in case Tilapia.

46. Transgenic Fish
• A transgenic fish is one which carries one
or more than one foreign genes.
• The foreign genes are selectively
incorporated by micro injection into the
egg → transgenic fish.

47. • Fish transgenies are difficult because of tough egg-chorion which
impedes microinjection.
• A prior puncture or use of micro pile (an opening in the egg surface
for sperm entry during fertilisation) has to be made for
microinjection.
• The micropile is made by or by using trypsin digestion.
• The gene can be transferred by electroporation (exposing the egg
chorion in an electric shock for a fraction of second) or by retroviral
injection.
• The foreign gene then transferred into the nucleoplasm or the
cytoplasm.
• In case of retroviral injection, the genes are first incorporated into
the viral genome, and then through the virus the gene are
transferred into the host by injection.

48. • · The fish of superior quality or desired
traits are produced by this process.
• Giant sized fish or super fish can be
produced.
• This can be achieved by incorporating the
growth promoting genes – bovine growth
hormone gene or human growth hormone
gene

50. GM Zebra fish

51. GENETICALLY MODIFIED ROHU
Centre for Cellular and Molecular Biology (CCMB)
CCMB fish are auto-transgenic, meaning the genes inserted into a
fish’s genome are a mashed-up cocktail of its own genome.
not importing genes from an alien species, not using DNA from even a
related species.
There are no foreign genes involved. Therefore, it’s unlikely that mere
genetic modification could produce a toxic protein,
the synthesized gene stimulates production of a growth hormone that
makes the fish bigger and grow faster,