Dendrobatids, more commonly known as dart frogs, reproduce by laying eggs. These develop into a free-swimming larvae called tadpoles before coming out of the water as miniature versions of the adults. Care of the eggs and larvae are very different than caring for the frogs in their final form–this blog entry will help ensure the young animals get the proper care they need.
Depending on the species of dart frogs, eggs may be deposited on leaves, in film canisters, on petri dishes under coco huts, or even on the glass wall of the vivarium itself. Egg clutches can vary greatly in size–some only lay 2-3 eggs at a time (Ranitomeya sp.), while some are capable of laying several dozen in one clutch (Phyllobates sp.).
Once found, the eggs can be removed from the vivaria for artificial rearing. If they are attached to a leaf or laid on the glass, they can be removed with a variety of objects (I primarily use a large spoon or razor). If they are laid on a petri dish or in a film canister, the entire object can be removed from the vivarium. I use a Slurpee straw to remove eggs from the film canister and place them on a petri dish. The same is done with eggs laid on leaves or the glass.
Now that the eggs are on a petri dish, they need to be kept moist. I use reverse osmosis water with a bit of boiled peat added to mist the eggs, until there is a small pool of water just touching the eggs. The petri dish is placed in an 8 oz. container (or similar; I used to use Ziploc sandwich containers) that contains a small amount of water on the bottom (usually just enough to cover the bottom of the container). The container is labeled with the species name and date laid, and kept at a temperature in the 70s °F.
Keep eggs moist by placing them in a sealed container with water.
Observe the eggs as development progresses. Bad (unfertilized) eggs will generally turn white and mold over–these eggs should be carefully removed and discarded. Fertilized eggs will slowly develop a line across the sphere of the egg – this is the tadpole's body forming. The tadpole will continue to grow as the sphere (yolk) shrinks in size, until a fully developed tadpole is visible in the egg.
From left to right: Dendrobates tinctorius 'Cobalt' egg at 1, 4, 10, and 15 days.
Depending on species, the eggs will hatch in approximately 14-21 days after they were laid, assuming they were fertilized. It can be difficult to see if a tadpole is out of the clear egg gel. The tadpole will assume a curled position as it grows in the egg. Once it assumes a straightened position, it has hatched. Initially, the tadpole will remain stationary as it absorbs the remains of the yolk, and may not respond to stimuli.
Left: Unhatched egg, on the verge of hatching. Right: A newly hatched Dendrobatid tadpole.
Once the tadpole has absorbed it's yolk (typically within 24-36 hours of hatching), it is carefully removed with a turkey baster or Marina Betta Waste Remover and placed in a labeled 32 oz. plastic cup with approximately 8 oz. of the same reverse osmosis/boiled peat mixture as used on the eggs. Additionally, a piece of Indian almond leaf and a bit of java moss are placed in the water. The Indian almond leaf releases tannins into the water, which function as a natural anti-fungal and anti-bacteria agent, as well as providing shelter for the tadpole, and an increased surface area to graze on. The java moss produces oxygen, and serves as a source of filtration and nitrogen uptake. The water is kept shallow initially to facilitate the tadpole's ability to swim to the surface and gulp air.
Tadpoles are kept in 32 oz., cups. Make sure to label your tadpoles carefully if you are working with multiple species!
After a few days, the tadpole cup is topped off with reverse osmosis water, and is fed for the first time. There are a wide array of foods available for tadpoles–we feed primarily Josh's Frogs Dart Frog Tadpole Food, as well as Sera Micron, and have had much success with these products. When selecting a food, it is important to choose one that does not readily foul the water, and contains a significant percentage of protein and vital minerals and vitamins. The tadpoles are fed 1-2 bits of food 2-3 times a week, and kept at temperatures in the low to mid 70s °F.
Over the next several weeks, the tadpole will continue to grow. As the water evaporates, it is topped off with reverse osmosis water. After approximately 6-8 weeks (this depends greatly on species and the temperature at which the tadpole is raised, with high temperatures resulting in faster metamorphosis and smaller froglets), the tadpole will develop visible back legs. After another month, the front legs will become visible. The front legs actually develop at the same time as the back legs in frogs, but do not emerge until much later. Once all four legs are visible, it is time to prepare your tadpole for morphing.
Amphibian literally means two-sided life–the origin of this term is very apparent in the life cycle of the dart frog. Care of the eggs and aquatic larvae differ greatly from that of the adult animal, but is by no means difficult.
Next blog, we will look at the care of morphing tadpoles and young froglets.