Aquaculture CRSP
Research Projects
Reproduction Control Research
Subcontract No. RD010A-02
Staff
University of Oklahoma, Norman, Oklahoma
| William Shelton | US Principal Investigator |
| William Baker | Graduate Student (USA; through August 2000; CRSP funded) |
Background
Limited knowledge of the reproductive physiology
and breeding of culture species was identified as one of the
key constraints to aquaculture in the Continuation Plan
1996. Specifically, effective and practical control of reproduction
is the major constraint in tilapia culture. Inter- and
intraspecific breeding programs can result in populations with
highly skewed sex ratios but often give inconsistent
results. Interspecific crosses have not proven to be practical due
to difficulties in maintaining the parent species integrity.
Intraspecific breeding programs have been developed
to exploit the sex inheritance mechanism in Nile
tilapia, Oreochromis niloticus. The androgenetic approach to
developing YY males simplifies the identification of YY males, as
all males produced should be of the YY genotype. Ninth
Work Plan research sought a phenotypic marker to
further simplify identification of YY males and continues efforts
to develop androgenesis techniques for Nile tilapia of
the Egyptian and Ghanaian strains.
Work Plan Research
The following Ninth Work Plan investigation continued
into the current reporting period:
- Monosex tilapia production through
androgenesis/9RCR7. The report submitted for this investigation
was a final report.
Note: 9RCR7 was terminated. The decision to
terminate 9RCR7 is documented in the Addendum to the Ninth
Work Plan.
Conference
PD/A CRSP Annual Meeting at Orlando, Florida, 26
January 2001. (Shelton)
Monosex Tilapia Production through Androgenesis
Ninth Work Plan, Reproduction Control Research 7 (9RCR7)
Final Report
William L. Shelton
University of Oklahoma
Norman, Oklahoma, USA
Abstract
Control of reproduction is vital to aquaculture and
includes artificial propagation as well as management of
unwanted recruitment. Developments in manipulation of the
reproductive system provide options to enhance production.
Nile tilapia, Oreochromis niloticus, spawning was managed
by photoperiod and temperature manipulation. A
controlled light cycle of 20L:4D and water temperature of 26 ±
2°C directed spawning to a predictable time frame. A
developmental rate (t0) relationship was described and applied
to chromosome manipulation. Blond Nile tilapia are
homozygous recessive for a color mutation that was used as
a phenotypic marker in the development of protocol
for androgenetic induction, while the color pigmentation for
red Nile tilapia is dominant over the wild type color
pattern. Androgenotes were produced by neutralizing the
female genome of normal color Nile tilapia or that of Red
tilapia (600 J m-2 UV dose), eggs were activated with sperm
from blond males or Ghana males, respectively, and then the
eggs were diploidized with cold shock (11 ± 0.5°C for 60
min) applied at various times after incubation at 28 ± 0.2°C.
Shock applied at 69 min post-activation produced greater
numbers of androgenotes than shocks applied at 59 or 79 min
post-activation; the shock application time of 69 min was used
for induction with red tilapia stocks. Production of
viable diploid androgenotes for crosses involving either red
or blond and Ghana stocks was very low, and no
progeny survived to maturity. Thus, neither verification of
sex determination in androgenotes nor testing of
monosex breeding was accomplished.
PD/A CRSP
