The importance of hormone reservoirs in mature teleost eggs is
unknown. To elucidate the effects of hormones on embryonic development,
steelhead trout eggs, Oncorhynchus mykiss, were immersed in either cortisol,
testosterone, or thyroxine at two different stages of development. Elevated
concentrations of cortisol were detectable in the trout eggs or embryos after
immersion. Eggs exposed to cortisol during water hardening hatched faster
than eggs exposed at the eyed stage. Eggs that hatched faster had elevated
cortisol and cortisol glucuronide concentrations at hatch compared to groups
immersed at eyed or control groups. The dedine of these elevated
concentrations of cortisol and cortisol glucuronide during embryonic
development suggest conversion, clearance or both. Eggs exposed to cortisol
at the earlier developmental stage did not appear to clear or convert cortisol
as efficiently as those exposed at a later stage. Testosterone did not
accelerate hatching in steelhead trout. Thyroxine accelerated hatching in
eggs immersed at the eyed stages but had no effect when given at water
hardening. These eggs that hatched faster were more synchronous in
hatching time compared to other groups. Prior to exogenous feeding (50
days post fertilization, dpf), animals immersed in cortisol when eye pigments
had higher mean condition factor (Kn) than other experimental or control
groups, but this effect was gone by 83 dpf. However, at 130 dpf, cortisol
groups that were immersed at the eyed stage were again heavier, longer, and
more robust than other groups. At 50 dpf, animals immersed in thyroxine at
water hardening were significantly longer and less robust (smaller condition
factor, Kn). These effects disappeared by 83 dpf. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/36163 |
| Date | 12 April 1993 |
| Creators | Yeoh, Choo-Guan |
| Contributors | Schreck, Carl B. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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