[Zbrafish] Easy Answer? z-fish technical questions

Christian Lawrence via zbrafish%40net.bio.net (by clawrence from rics.bwh.harvard.edu)
Thu Feb 22 16:53:04 EST 2007


Dwane -
See answers in CAPS inserted into text of your message below

On 20 Feb 2007 20:52:28 -0800, ddecker9 from hvc.rr.com <ddecker9 from hvc.rr.com> wrote:
> I have a few simple questions about zebra fish...
>
> 1) When do they normally throw eggs if they are on an appropriate
> light cycle? i.e. what time during the cycle. I'm  assuming when
> lights come on.
NORMALLY THEY SPAWN AT "DAWN" WITHIN THE FIRST HOUR OR SO AFTER THE
LIGHTS IN A FACILITY COME ON.  HOWEVER, DEPENDING ON THE FISH, AND THE
ENVIRONMENTAL CONDITIONS, THEY MAY SPAWN ALL MORNING AND INTO EARLY
AFTERNOON.  MANY FISH ALSO SPAWN IN THE EVENING, TOWARDS "DUSK"
(WITHIN A FEW HOURS OF WHEN THE LIGHTS GO OFF). IN THE WILD, THEY ALSO
ARE KNOWN TO SPAWN AT VARIABLE TIMES OF THE DAY, INCLUDING DURING
RAINSTORMS, ALTHOUGH THEY SEEM TO BE PREDOMINANTLY CUED BY THE ONSET
OF DAYLIGHT.
> 2) How long does it take for them to adjust to a new light cycle?

NO HARD DATA ON THIS, BUT USUALLY A FEW WEEKS.   THE MORE DRASTIC THE
CHANGE, THE LONGER THIS WILL TAKE.  IN MOST CASES, THEY WILL BE
COMPLETELY SHIFTED IN A MONTH.
>
> 3) I've noticed a huge range of sizes when the fish are young. What
> accounts for the large size difference among fish of the same hatch.
> Also, I've noticed a few very tiny dark colored fish. Why is this?
THERE ARE SEVERAL POTENTIAL REASONS WHY YOU MIGHT SEE HIGH VARIABILITY
IN GROWTH RATES IN A CLUTCH.  LOW FOOD AVAILABILITY (OR  AVAILABLE
USABLE FOOD) IS PROBABLY THE MOST LIKELY.  IMPROPERLY DELIVERED/AND OR
FORMULATED DIETS WILL RESULT IN LOWER AMOUNTS OF USABLE PREY ITEMS PER
FISH.  COMPETITION FOR THESE RESOURCES (AND BETTER OR WORSE
COMPETITIVE ABILITIES) THEN MANIFESTS IN DIFFERENTIAL RATES OF GROWTH.
 POOR WATER QUALITY MAY ALSO ACT IN A SIMILAR FASHION, ALTHOUGH THIS
USUALLY (BUT NOT ALWAYS) AFFECTS WHOLE CLUTCH.

GENETIC BACKGROUND MAY ALSO BE PLAYING A ROLE.  INBRED LINES CARRYING
ELEVATED MUTATIONAL LOADS WILL ALSO TYPICALLY SHOW A WIDE VARIATION IN
GROWTH RATES AMONG INDIVIDUALS IN THE SAME CLUTCH, EVEN UNDER GOOD
CONDITIONS.  THIS CAN WORK IN SYNERGYSTIC FASHION WITH DIET AND/OR
ENVIRONMENTAL CONDITIONS (GETS WORSE IN BAD SITUATIONS).

THE SMALL DARK FISH YOU SEE MAY BE MUTANTS.  IN  LINES THAT ARE NOT
CAREFULLY PROPAGATED (MORE INBRED) IT IS NOT UNCOMMON TO SEE THESE
SORTS OF "METABOLIC" MUTANTS THAT HAVE A GENETIC DEFECT THAT GENERALLY
RESULTS IN LOW GROWTH, ARRESTED SEXUAL DEVELOPMENT, HYPERPIGMENTATION,
ETC.
>
> Please let me know who might be able to answer these questions or
> where on zfin I might find them.
>
> Thank you for your time.
> Dwane
>
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-- 
Christian Lawrence
Brigham and Women's Hospital
Karp Family Research Laboratories, 06-004B
One Blackfan Circle
Boston, MA 02115
Tel: 617.355.9041
Fax: 617.355.9064



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