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Re: [Killietalk] K. marmoratus habitats, etc./2
To answer Pablo's quesions as best I can:
1. We breed kmar in glass "fingerbowls" about 10 cm wide and about 5 cm high.
These bowls are stackable, and we keep them in stacks up to 12 - 14 bowls high.
A single "herm" is placed in each bowl. I haven't checked on a commercial
source for these bowls in quite some time (since I own literally hundreds), but
I believe we purchased them from Carolina Biological Supply Co. Aquarists,
including killifish specialists, who see this arrangement are usually appalled
and sometimes speechless; it is designed for efficiency, not for optimal
viewing of the fish.
The "false bottom" is a disk of rigid plastic screen with holes about 3 - 4
in diameter. The screen fits the inside diameter of the glass bowl rather
snugly, so that the herm cannot get below the screen into the bottom chamber.
The screen is set off the bottom by spacers. Originally, these were glass
"marbles" fixed to the bottom of the bowl by gluing with silicone cement.
Subsequently, I switched to using the top (straight) halves of 1.5 ml
disposable plastic microcentrifuge tubes. Some of my colleagues use a glass
ring instead. Obviously, many different types of spacers can be used. When in
as a "false bottom," the screen, sitting on its spacers, establishes a bottom
chamber about 1 cm high. The eggs are collected from this chamber by removing
the herm and the screen once a week, and then picking out the eggs with a
plastic eye dropper. It is at this time that the water is changed, completely.
The design has the obvious disadvantage of allowing uneaten food and feces
to pass through the screen also, and often the eggs are mixed with these in the
bottom chamber. Its advantages are that the eggs, once spawned, quickly fall
beyond the reach of the herm, who will otherwise eat them. The eggs aren't
very adhesive (which is one of the reasons why mops don't work very well).
When housed in setups like this, herms usually spawn one egg at a time.
Sometimes, a herm will express a mass of up to 70 - 80 eggs (though usually
around 10), seemingly simultaneously. When these masses are expressed, many of
the eggs cling to the vent area of the herm, rather like medaka eggs. They are
off. If housed in groups, other herms will go after the attached eggs much as a
thirsty man might attack a large bowl of grapes!
BTW, when spawning eggs, some herms seem to twist their bodies as if they
were in a spawning embrace with a male, while others just pop them out, willy
nilly, with no obvious preliminaries. Also when viewing stacks of bowls, each
containing a herm, very often one doesn't actually see fish, particularly in
the mornings. This is because the fish are resting, out of the water, on the
underside of the bowl stacked above them. A smart smack on the top of the
stack usually results in all the fish dropping off their ceilings into the
I expect that most aquarists will not want to use the bowls, but the false
bottom idea can be adapted to almost any type of spawning chamber or tank that
one likes. It is designed for herms living alone and is less effective if
multiple herms are housed together (for obvious reasons).
2. We incubate the eggs in sea water in 7 cm diameter plastic petri dishes.
Some labs use only glass petri dishes. Usually, we use just enough sea water to
cover the eggs, leaving a "head" of a mm or so. We incubate them in the dark at
about 24 C (the ambient temperature of the fish room). Infertile eggs are
obvious within a day or two, and are
removed. Subsequent mortality of embryos under most conditions is about 15 to
25$%, but 50% has been noted in some cases. Diapause at the end of development
is sometimes a problem, particularly if the incubation temperature is too low
(20 C or less). In my lab, problems with diapause are episodic, and we can go
long periods without it bothering us too much. When it does become an issue, we
have used several methods to break it, including the usual ones like adding dry
food or microworms to the water, moving the embryos to half sea water, adding
peat extract, etc. The most
effective method I've found is to seal the petri dish with scotch tape and have
someone take it for a ride on a motorcycle for about half a mile or so. A car
with bad shock absorbers probably would work almost as well. In recent years,
I have used manual dechorionation on stubborn embryos, but it takes practice
and a steady hand, and I doubt that many aquarists will want to try it.
3. The fry are very easy to raise. We keep newly hatched fry together for
about a week, and then usually move them to individual plastic containers for
further rearing. They are very cannibalistic, and the slightest size
difference usually mean that the larger fry makes a meal out of the smaller
ones. We feed Artemia nauplii almost exclusively, even to adult fish (I know
this is killifish "heresy," but there it is.) The advantage of Artemia is an
obvious one: they stay alive in sea water until they are eaten (which isn't
usually a very long period---these are not fish with delicate appetites). Even
so, water needs to be changed frequently in the small containers we
use---generally about once a week.
Our lab has had, at some peak periods, as many as 1400 fish, most housed
individually. We have had up to about 400 herms as breeders in individual
bowls. Obviously,this entails having technicians available to feed, monitor
eggs, change water, etc. At the moment, we have fewer than 400 fish, and I'm
phasing out the live fish colony as preparation for closing down the fishroom.
I will retire in less than 4 years, and I want to have ample time to give our
fish to colleagues, etc. before I do so. I expect that the fish room will be
closed down by June 08.
The setup that Pablo is using will probably work well for two herms, in the
sense that they will have enough room to avoid one another a bit. I would
increase the tank size to 20 or even 40 l. When I house multiple herms in the
same tank, I put 10 - 15 7 - 8 cm long pieces of 1/2 inch pvc pipe on the
bottom to provide hiding places. When they become aggressive, the herms will
literally chase one another through the pipes. Above all, SEAL THE TANK. Like
other "Rivulus," kmar herms and males can find the smallest crack by which to
escape. Remember that leaving the water is one of the things they do best, and
that they can live, packed in moist leaves, for at least 60 days. If you find
a kmar shriveled on the floor, do not presume that it is dead. Put it in sea
water---often you will have a "miracle."
Please note that many of these culture methods were developed by my colleague,
W.P. Davis. While at the Univ. of Guelph, my colleague David Noakes
independently developed very similar methods. Also, most of the field
observations mentioned in my last post were initially made by Scott Taylor
and/or W.P. Davis. Most often, I was just "along for the ride," generally with
my mouth agape in astonishment.
Bruce J. Turner
Dept. Biol. Sci.
Blacksburg, VA 24061
"...We are Hokies. We will prevail..."
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