Grainger Lab X.
tropicalis Tadpole Husbandry Protocol
Updated June 1, 2001
We are currently using a tadpole husbandry system created
in collaboration with Will Brown, formerly of the National Aquarium in Baltimore.
The purpose of this system is to raise tadpoles from a few days of age through
metamorphosis with a minimum of "hands-on" effort and a maximal
rate of survival.
The apparatus described herein are all easy to assemble and inexpensive –
perfect if your lab is just getting started with trops or even if you already
have a sizeable colony and are looking to expand.
Here we describe three setups: one for the care of
large groups of tadpoles (the Gigaswamp), a simple and inexpensive one for
taking care of medium sized groups (Dual-tank Biofilter) and a third for the
care of small groups of precious, usually transgenic or mutant, animals (the
Port-a-swamp).
1. The Gigaswamp
Transferring Tadpoles
Transferring tadpoles from tank to tank is perhaps
the most perilous part of X. tropicalis
husbandry. Tadpoles are particularly
susceptible to shock from apparently minor changes in temperature, salinity,
or pH, and these can kill large numbers of tadpoles in a matter of minutes.
When transferring tadpoles from one environment to another it is always best
to introduce them slowly. Allow the temperatures of the old and new container
to equalize, and then transfer a small amount of water from the new container
into the old. Repeat this process of adding water for several hours until
the volume in the tadpoles' current container has almost doubled. Then pour
the water containing the tads into the new container.
There are four
critical factors to consider when raising young tadpoles: housing, density,
cleaning and feeding.
Housing
The Gigaswamp consists of:
1. Two large, polypropylene tanks each of approximately
90-gallon capacity. One of these is the TADPOLE tank containing the animals
and one is the SUPPLY tank holding water only.
2. The SUPPLY tank is filled 24 hours in advance to
age the water. This ageing step is
crucial to remove volatile contaminants from the water. Although we use
non-chlorinated well water, we find that unaged well water is harmful to tadpoles.
This may be due to dissolved CO2 in the water lowering the pH (incoming
well water is about pH 5.8, well water aged one day in the SUPPLY tank is
about pH 7). The water is recirculated using a heavy-duty aquarium pump (no
carbon or ammonia filters are used with this unit) and is heated to 27°C by a 150W aquarium heater. Both the pump and
heater can be purchased at a local pet store. The SUPPLY tank also contains
several large rocks taken from a local stream and several sprigs of Pothos,
or Devil's Ivy, that have taken root in the water. Before adding the Pothos
to your setup, wash it thoroughly!
Light is provided to both tanks by a standard 4-foot double fluorescent fixture,
available at most home-improvement stores.
3. The TADPOLE tank contains some Pothos placed on
floating styrofoam "islands" and a fluorescent light (as pictured
above). The TADPOLE tank also contains a thick mat of green algae on the sides
and floor of the tank (visible as a greenish tint to the water). We believe
that this algae mat is a big reason behind the success of the gigaswamp. It
not only provides an additional level of biological filtration, it also provides
a more natural environment for the tadpoles. The water of the gigaswamp is
teeming with microorganisms and algae and they love it.
4. Tadpoles can be raised through metamorphosis and
even into early froglet stages in the Gigaswamp.
Cleaning
We do not normally clean the TADPOLE tank for the first week after new
tadples have been added. They seem to condition the water and don't do well
if it is changed frequently. After the first week, change half the volume
of the Gigaswamp every week. To do so, we use a submersible aquarium pump
that is housed inside a large polypropylene bottle. The bottle has several
large holes cut in the sides that are covered with Nitex mesh (Fisher) glued
in place with non-toxic aquarium glue. The mesh prevents tadpoles from being
sucked into the pump. The output tube from the pump passes through a hole
in the lid of the bottle and out of the tank to a floor drain. After emptying
half the water, refill the TADPOLE tank from the SUPPLY tank. Finally, refill
the SUPPLY tank from the tap.
Density
We start tadpoles in the Gigaswamp at a density of
about 5 tadpoles/liter. This corresponds to about 1000 - 1250 tadpoles in
70 gallons (about 260 liters). At these densities, 75% of the tadpoles should
begin metamorphosis (determined by the appearance of forelimb buds) at about
4.5 weeks of age and should become froglets by 6 weeks. Even faster times
to metamorphosis have been obtained by lowering the density even further.
Feeding
For the first two weeks, we feed the tadpoles 4 or
5 times daily with SERA Micron (Sera North America, 1-800-755-7372). Start
feeding with a small amount of food - just enough to cover the surface of
the water with a thin, greenish film. Slowly increase the feeding frequency
and amount as the tadpoles grow. A good rule of thumb is to allow the water
to clear between feedings. After two weeks we use a mixture of SERA Micron
and flake food (Aquatic Ecosystems, 1-877-347-4788 or 1-877-FISH-STUF) that
we refer to as "Advanced Tadpole Diet". It is made up by combining
2 liters volume of "finely ground fish flakes" (Aquatic Ecosystems
catalog #FOC), 1 liter volume of "45% protein fish food powder"
(Aquatic Ecosystems catalog # F1A) and 34g Sera Micron (2, 17g jars). This
mixture is high in protein and can be fed to older tadpoles or even froglets.
2. The Dual-tank
Biofilter
This setup can be repeated as many times as desired
to house any number of X. tropicalis.
It is inexpensive, easy to set up, and self-contained. We use this system
to raise tadpoles, froglets, and even adult frogs.
Transferring Tadpoles
Transferring tadpoles from tank to tank is perhaps
the most perilous part of X. tropicalis
husbandry. Tadpoles are particularly
susceptible to shock from apparently minor changes in temperature, salinity,
or pH, and these can kill large numbers of tadpoles in a matter of minutes.
When transferring tadpoles from one environment to another it is always best
to introduce them slowly. Allow the temperatures of the old and new container
to equalize, and then transfer a small amount of water from the new container
into the old. Repeat this process of adding water for several hours until
the volume in the tadpoles' current container has almost doubled. Then pour
the water containing the tads into the new container.
There are four
critical factors to consider when raising young tadpoles: housing, density,
cleaning and feeding.
Materials
NB: Many of these items can be purchased at your local
pet store. Some items, such as glass tanks, are difficult to get by mail-order
and usually HAVE to be bought locally. We purchased other items from either
Aquatic Ecosystems (1-877-FISH-STUF) or from Pet Warehouse (1-800-443-1160).
2 glass aquaria, one (TADPOLE) ten gallon and one (BIOFILTER)
five gallon capacity (bought locally)
1 submersible aquarium water pump and tubing (Aquatic
Ecosystems catalog #PU14 for pump, tubing comes with Biowheel filter unit)
1 Marineland Biowheel filter unit (Aquatic Ecosystems
catalog # BP3)
1 aquarium air pump, airstone and tubing (bought locally,
airstone brand is Lee's Discard-a-Stone)
1 submersible aquarium heater (50W or 100W) with an
internal thermostat (bought locally)
1 mesh bag containing shredded PVC for biofilter (Aquatic
Ecosystems catalog # BF165 for mesh bag and #BF250 for PVC)
1 mesh fry tank to house pump (Pet Warehouse catalog
#120766)
1 U-tube and plastic strainer for return siphon (Pet
Warehouse catalog #439634 for U-tube, Aquatic Ecosystems catalog # PA1241
for plastic strainer)
A source of high-quality, dechlorinated water
Housing
1. Place the BIOFILTER and TADPOLE tanks side by
side. You can place several setups on one shelf of a sturdy metal rack
(we use Metro racks: http://www.metro.com/ or 1-800-441-2714).
2. Place immerson heater (set for 25°C but
not plugged in) in the BIOFILTER
tank. Add mesh bag with shredded PVC and fry tank mounted on the side. Put
aquarium pump in fry tank and connect to the Biowheel mounted on the side
of the TADPOLE tank. The mesh fry tank housing keeps the pump mechanism from
getting clogged with gunk from the water. Remove the fry tank periodically
and rinse it off with distilled water.
3. Fill the BIOFILTER tank until it is almost full,
then fill the TADPOLE tank to the same level. Place the plastic strainer on
the end of the U-tube (some of the plastic may need to be trimmed away with
a razor blade). Fill the U-tube with water and connect the two tanks, taking
care not to break the column of water. Make sure the plastic strainer is in
the TADPOLE tank to keep tadpoles from being sucked into the BIOFILTER tank.
4. Connect the airstone and tubing to the air pump
and place one airstone in the BIOFILTER tank, being careful not to put it
under the end of the U-tube (the bubbles of air will break the siphon and
cause the tank to overflow). Place another airstone in the TADPOLE tank just
at the surface of the water (we use Lee's Discard-a-Stone for this because
it floats). Now turn on the heater, air pump and water pump. The water will
be sucked from the TADPOLE tank by the siphon, passed through the BIOFILTER
tank and returned via the aquarium pump.
Density
We start young tadpoles fairly dense, between 5 and
20 tadpoles/liter depending on the percent fertilization of the eggs. This
translates to between 200 and 800 tadpoles per 10-gallon tank. They seem to
do well at higher densities while young, between fertilization and about two
weeks of age. After that, when the tadpoles are clearly growing, we split
large groups into two or more tanks.
Cleaning
TADPOLE tanks are not cleaned, nor are they attached to the BIOFILTER tanks, until the tads are about
10 days old. Up until that time the tadpoles are too small to be retained
by the strainer at the bottom of the U-tube and will be sucked into the BIOFILTER
tank. However, make sure the airstone in the TADPOLE tank is working during
that time – it's action helps to circulate the water when the pump isn't
running. After 10 days, turn on the pump and start the siphon. At this point,
cleaning is usually done once a week. To clean these setups, turn off the
pump and disconnect the siphon. Drain the BIOFILTER tank and refill with clean
water (we use the "aged" well water from the Gigaswamp SUPPLY tank).
The reconnect the siphon and turn on the pump.
Feeding
Feed the tadpoles 4 or 5 times daily with SERA Micron.
Start feeding with a very small amount of food - just enough to cover about
half of the surface of the water with a thin, greenish film. Slowly increase
the feeding frequency and amount as the tadpoles grow. A good rule of thumb
is to allow the water to clear between feedings. The accumulation of a small
amount of green algae on the walls and floor of the tank is normal and healthy,
but avoid the formation of large carpets of green slime, as this is a sign
of overfeeding. For tadpoles older than two weeks or so we supplement with
"Advanced Tadpole Diet" (see above for the recipe).
3. The Port-a-Swamp
The port-a-swamp was developed largely by Lyle Zimmerman
as a way to raise small numbers of precious animals on the bench-top (i.e.
in plain sight where they can be watched carefully rather than downstairs
in the animal room).
The key to the success of the port-a-swamp is observation. The tadpoles should be watched carefully, sick ones isolated
quickly, and dead ones removed promptly. Care and monitoring should be done
as often as possible, even on evenings and weekends.
Transferring
Tadpoles
Tadpoles are
particularly susceptible to shock from apparently minor changes in temperature,
salinity, or pH, and these can kill large numbers of tadpoles in a matter
of minutes.
When transferring tadpoles from one environment to another it is always best
to introduce them slowly. Allow the temperatures of the old and new container
to equalize, and then transfer a small amount of water from the new container
into the old. Repeat this process of adding water for several hours until
the volume in the tadpoles' current container has almost doubled. Then pour
the water containing the tads into the new container.
There are four
critical factors to consider when raising young tadpoles: housing, density,
cleaning and feeding.
Housing
The port-a-swamp consists of:
1. A SUPPLY tank (at the right in the photo above),
usually a 10 or 20 gal. glass aquarium. See the above caveat about thoroughly
cleaning all containers before use. This contains a standard-size aquarium
pump for recirculating the water (no carbon or ammonia filters are used with
this unit), a 50W aquarium heater to keep the water at 25°C, and some plant material - we use a couple
of sprigs of Pothos, or devil's ivy. Again, before adding the Pothos to your
setup, wash it thoroughly!
2. One or two large, flat plastic containers (we use
two, 20 liter capacity sweater boxes from Wal-Mart seen at the left in the
photo above) filled about 1/4 full with water and containing one 50W heater
and an air bubbler to provide some circulation. These containers serve to
maintain the temperature in the smaller, individual tanks placed inside them.
3. Small tanks, ranging in size from 0.05 to 1.5 liters.
This assortment of tank sizes accomodates tadpoles of various ages at several
different densities. We use 50ml. plastic fly vials (Carolina Biological Supply,
2700 York Road, Burlington, NC 27215, USA, 1- 800-334-5551) for single tadpoles. For several tadpoles,
we use clear, plastic food service-type containers of about 300ml. capacity.
It is important to purchase food-grade containers, since they should contain
no harmful organic residues. We use ice-cube trays, which hold about 2 liters,
for larger numbers of tadpoles. These are purchased at a local Wal-Mart. We
put sprigs of Pothos in some tanks (be sure to wash it thoroughly), and aerate tanks
holding 1 liter or more.
Density
Density ranges from 1 to 10 tadpoles/liter. In cases
where only one or two tads are being raised in a single tank, we often add
some water from a tank with other tadpoles (tadpole conditioned media or TCM).
This seems to help with survival of single tadpoles, possibly by adding beneficial
bacteria or some other necessary factor.
Cleaning
Tanks should be cleaned once per week if they contain
young tadpoles. Cleaning frequency and amount of water changed should slowly
increase as the tadpoles grow. Generally, if the tadpoles are two weeks old
or older, replace half the water once per day with water from the SUPPLY tank.
Use a pipette to suck out bits of detritus, dead tadpoles, or large pieces
of green slime.
Feeding
Feed the tadpoles 4 or 5 times daily with SERA Micron.
Start feeding with a very small amount of food - just enough to cover the
surface of the water with a thin, greenish film. Slowly increase the feeding
frequency and amount as the tadpoles grow. Observe carefully and adjust the amount of food on a tank-by-tank
basis. A good rule of thumb is to allow the water to clear between feedings.
The accumulation of a small amount of green algae on the walls and floor of
the tank is normal and healthy, but avoid the formation of large carpets of
green slime, as this is a sign of overfeeding.