3. WHAT IS REPRODUCTION?
Reproduction is a fundamental feature of all
known life; each individual organisms exists the
result of reproduction
CLASSIFICATION OF RETRODUCTION:
Reproduction is two types -
REPRODUCTION
ASEXUAL REPRODUCTION
A new ogranism is produce by one
parent. The new organism will be
identical to the parent
SEXUAL REPRODUCTION
It requires two parents each giving 23
chromosomes to the offspring
5. Pituitary extract :
The pituitary gland produces and stores gonadotropin hormones
(GtH), which play a decisive role in ovulation and spermiation.
Injected pituitary material bypasses the brain-pituitary link, acting
directly on the ovaries and testes, providing the surge in blood GtH
levels that normally precedes spawning .
.
6. Commercial pituitary extracts :
Common carp pituitary or salmon pituitary extracts,
available commercially, are widely used for induced
spawning. These are crude acetone-dried powdered
whole pituitaries.
Therefore, carp, goldfish, Chinese carps, catfish, etc.,
are more likely to spawn successfully when injected with
pituitary extracts from carp. Salmon, trout, etc., are more
likely to spawn successfully when salmon pituitary is
used. However, both are effective on a wide variety of fish
species
7. Purified gonadotropin :
To better quantify the hormone injected, purified gonadotropin
hormones are frequently used.
Human Chorionic Gonadotropin (HCG) is the most common purified
gonadotropin hormone used for induced spawning. In fish, the
injected gonadotropin mimics the natural GtH produced by the
fish’s pituitary. Just as is the case with pituitary extracts, purified
hormones such as HCG bypass the brain-pituitary link, acting
directly on the ovaries and testes (Figure 2). HCG has been used
to spawn fish such as striped bass, white bass, red drum, catfish,
and mullet.
8. HCG + Pituitary extract :
HCG, however, is not effective on all species. HCG has been used in
combination with common carp pituitary extract; for some species, the
combination has shown to have improved potency than either
preparation used alone. The two hormones can be prepared and
injected separately, or the HCG solution can be used when mixing the
pituitary extract .
luteinizing hormonereleasing hormones :
Injections of mammalian Luteinizing Hormone-Releasing
Hormone (LHRH) have been used experimentally to mimic the
fish’s GnRH. However, a comparatively large dose and frequent
injections were required. Recently, synthetic LHRH analogs,
referred to as LHRHa or GnRHa, have been manufactured.
10. Eyestalk optic ganglia
The optic ganglia in the eyestalks of shrimp synthesize several peptide
hormones that play important roles in controlling growth and
reproduction. This hormone family includes the crustacean
hyperglycemic hormone, molt-inhibiting hormone, growth-inhibiting
hormone, vitellogenesis-inhibiting hormone, red pigment-
concentrating hormone, and distal-retinal pigment hormone. Other
neurotransmitters and neuromodulators like serotonin and
norepinephrin are also in this family.
11. Molting hormone
Shrimp molting is controlled by the eyestalk system and the Y-organ
(endocrine gland) through the production of the hormone ß-ecdysone,
the precursor of 20-hydroxyecdysone, which is responsible for molting.
Since growth in shrimp occurs through molting, there is much interest in
its potential control. Controlling molting in shrimp clearly would be of
great economic relevance, especially if soft-shelled shrimp that did not
require deshelling during processing could be produced.
Metabolic hormones
Metabolic hormones include the crustacean cardioactive peptide,
produced by the thoracic ganglion and involved in immunoreactivity, and
the crustacean hyperglycemic hormone (CCH) produced by the X organ
but released by the sinus gland. CHH regulates the release of glucose
from the hepatopancreas, and is known to undergo daily fluctuation with
a small peak in the morning and a large peak at night.
12. Androgenic hormone
Produced by the androgenic glands and present only in male shrimp,
androgenic hormone is responsible for the development of
masculine characteristics, including gonads and spermatogenesis.
Vitellogenesis-inhibiting hormone
Recently, much attention has focused on vitellogenin, the precursor
to the egg yolk protein vitellin. Vitellin, a lipo-glycocarotenoprotein
with a high molecular weight, is the major yolk protein of mature
shrimp eggs. With 28 to 35 percent lipid, vitellin is the primary
source of lipid for membrane formation and energy storage for
developing nauplii.
13. Conclusion
The control of hormone production in shrimp and other
economically important decapod crustaceans is still not well
understood. Through improved nutrition and feeding/production
techniques, the shrimp endocrine system could be controlled and
manipulated to improve reproductive and growth performance
under commercial culture conditions.
14. REFERANCES :
The work reported in this publication was supported in
part by The Southern Regional Aquaculture Center
through Grant No. 89-38500-4516 from the United States
Department of Agriculture.
ALBERT G.J. TACON, PH.D.
Aquatic Farms Ltd.
49-139 Kamehameha Highway
Kaneohe, Hawaii 96744 USA
agjtacon@aol.com
