Dwarf Clawed Frogs – Commonly Seen, Uncommonly Bred by Ken Zeedyk

African dwarf clawed frogs are a staple of most pet stores, and a group of them can be purchased at a reasonable price. However it seems that most people add them to their aquariums as more of a “novelty”, or as an animal their kids really wanted to have. Seldom have I come across aquarists who have kept these little frogs with the intention to breed them, so I figured I’d give them a shot.

The genus name is Hymenochirus, and the species most often encountered is likely Hymenochirus boettgeri. I have also seen lighter colored dwarf frogs identified as “Blondies” that appear to be a different species rather than a color morph of H. boettgeri, but I have not been able to find a definitive answer to this. I have seen those referred to online as H. boettgeri “gold” as well Hymenochirus curtipes. Regardless of the species, these little frogs are native to the equatorial forest zone of Central Africa and are completely aquatic. As an interesting side note they also lack tongues and teeth, like all members of the Family Pipidae.

One word of caution: Don’t confuse the dwarf clawed frogs with their much larger Xenopus laevis cousins! Xenopus frogs get much larger, and are voracious predators on fish.  Easy ways to tell them apart (besides size) is to look at the front feet, eye position, and snout. The front feet of dwarf frogs are webbed, while the larger clawed frogs are not and have “fingers”. Dwarf frogs have eyes that are more on the sides of the head, while Xenopus have eyes on the top of the head. The dwarf frog also has a pointed snout, while the larger clawed frogs will have a flatter rounded snout.

I have found that the dwarf frogs do best in a species tank, where they don’t have to compete with fish for food. They can also be picked on by fish, but will in turn consume small fish and fry, as well as shrimp, if given the opportunity. They are predatory sight and smell feeders so a variety of live, frozen and pelleted food may be consumed. Live black worms are a favorite of my colony. A constant temperature around 77 degrees Fahrenheit works for them in a mature, well planted tank with a pH around 7.2 to 7.6. Gentle filtration such as a sponge filter is recommended. A power filter would be ill advised with these little guys since there is a chance they could be sucked onto the intake and not be able to escape. The dwarf frogs also like plants in the water column, such as Najas grass, that they can rest in. Hiding place are also appreciated and may be utilized by males as a singing location.

Telling boys from girls can be difficult, especially on younger frogs, but there are visible differences. Mature females will be rounder bodied and have a small “tail” stub. Males will be slimmer and develop a white gland behind the front legs, which looks like a pimple. Males will also sing underwater, and can sound like a broken airline or a soft humming sound.

Spawning can take place at any time, however the most activity has occurred in my colony after large water changes and heavy feedings with live food. Temperature changes in conjunction with water changes may also trigger egg laying. Spawning occurs during amplexus, where the male will clasp the female and basically ride around with her. Amplexus can last for a few hours, or even days. Spawning occurs at the surface of the water, where the very small black eggs are laid singly, but often in large quantities. Removal of the eggs to a separate hatching and rearing container is advised, since the adults will consume eggs and tadpoles. Scooping the eggs out with a small cup works, although you will need to rinse the eggs off the surface since they like to stick to things. I’ve hatched eggs successfully with and without a fungicide, and have even had many eggs hatch right in the adult’s tank. Getting them to spawn and subsequently hatching the eggs is the easy part. Raising the tadpoles can be very challenging.

Eggs will hatch in three to four days, with the larvae becoming free swimming after four to five days. It is best to raise them in their own container or small aquarium, using water from the adult’s tank and a small, low volume sponge filter that does not produce a lot of current. Like the adults the tadpoles are predatory suction feeders, but they feed on very small food items. Live food cultures will be necessary, such as infusoria and baby brine shrimp. A light above the tank will help to concentrate the food items at the surface, which is within the narrow feeding range of the tadpoles. I’ve tried various dry powders, but with limited success. The dwarf tadpoles don’t seem to actively ingest it like the filter feeding Xenopus tadpoles do. I’m still experimenting with different sizes of Golden Pearls, so hopefully I will find a prepared food that will work throughout their tadpole stage. As long as the bug eyed tadpoles are kept in clean water and have been feeding regularly metamorphosis into little froglets should occur within 8 weeks. The froglets can be housed and treated like the adults, but in a separate tank until they put on some size. As with most frogs little ones can be viewed as a snack.

If you are looking for a different type of breeding project that can be challenging and rewarding, I’d suggest giving these little frogs a try. They don’t take up a whole lot of space, and if you are successful in raising the tadpoles the little froglets should be easy to re-home.

Newly Hatched Larvae (top) Egg close to hatching (bottom)

Feeder Fish: Slow Death for a Quick Meal by Charles Bradfield

When the question of feeder fish arises, the debate usually centers around the ethics of using live fish to feed predatory aquarium fish. While this debate is one that should be discussed, it seems to shift focus away from answering a more important question: Is feeding live fish what is best for our predatory pets?

Proponents will claim that they are a cheap and easy way to provide a nutritious meal for their fish. That cheap price tag can only be achieved by culturing feeder fish intensively in crowded systems. The effects of maintaining fish this way have been extensively studied in Atlantic salmon (Salmo salar) raised in sea pens. Fish raised in these conditions display a higher parasite load and are more prone to outbreaks of disease than their wild counterparts. In fact, these sea pens are so susceptible to parasite infestations, that wild fish who live in proximity to these farms display a parasite load higher than fish living in regions without salmon farms (Morton et al, 2008). The risk of transmitting an infection presents a clear threat to the health of our aquatic pets.
Even without the threat of an infection, there is another flaw in the species of fish being sold as feeder fish that is potentially fatal. Goldfish (Carassius auratus), rosy minnows (Pimephales promelas), and white clouds (Tanichthys albonubes) are all members of the family Cyprinidae.  Cyprinid fish are known for being fatty and rich in an enzyme called thiaminase. This enzyme catalyzes the breakdown of thiamine, which is more commonly known as Vitamin B1 (Gordon, 2012). A thiaminase-rich diet can result in thiamine deficiency syndrome (TDS), a medical condition characterized by nervous system deterioration (Dreyfus and Victor, 1961).  This can result in a myriad of symptoms, but the ones most easily observed are probably: stunted growth, convulsions, and a sudden loss of appetite. If left untreated TDS will result in the death of your fish (Fisher et al, 1995).
Goldfish are so rich in thiaminase that they are a preferred source for isolating thiaminase for use in laboratory studies (Gordon, 2012). Wild predatory fish often eat fish containing less severe quantities of thiaminase, but most wild fish would never eat something as thiaminase-rich as a goldfish. Minor doses are easier to counter a potential deficiency by eating a varied diet. Prey options for a wild fish can be surprisingly diverse, with prey options, like thiamine-rich fish species, insects, shrimps, molluscs, etc.

I have heard people claim “success” by keeping an oscar (Astronotus ocellatus) alive for three or four years on a feeder fish heavy diet, but this sounds less like a success when you learn that oscars are capable of living for at least twelve years (Paiva and Nepomuceno, 1989). A poor diet reduces the lifespan of any animal, making it beneficial to replicate the wild diet of your predatory pets. For example, Water Colors Aquarium Gallery maintains a mixed-species group of bamboo sharks (Chiloscyllium spp.) that are fed a diet of frozen krill, frozen silversides, fresh ocean perch fillets, and frozen squid. These dietary decisions are based on studies of the diet of wild bamboo sharks, which is comprised of crustaceans, fish, and cephalopods (Nur-Farhana et al, 2013). 

We all keep fish because we love it, but this means we have to accept the responsibility of taking care of another living creature. Each species of fish has spent millions of years adapting to their environment and we should respect that. Google Scholar, a search engine for scientific literature, makes it easier than ever to find reliable sources on the wild diet of any fish you are keeping. The modern aquarium hobbyist has a plethora of frozen foods, fresh seafood, and commercial pellet-foods readily available to them. The benefits of replicating this diet should be obvious, whether you are a seasoned breeder or a novice fishkeeper. When you factor all of that in, it becomes abundantly clear that it is time for everyone to accept the fact that feeder fish have no place in the diet of our aquarium fish. 

Literature Cited

Dreyfus, P. and M. Victor. 1961 Effects of thiamine deficiency on the central nervous system. The American Journal of Clinical Nutrition, Vol. 9(4):414–425

Fisher, J., J. M. Spitsbergen, T. Iamonte, E. E. Little, and A. Delonay. 1995. Pathological and behavioral manifestations of the “Cayuga syndrome,” a thiamine deficiency in larval landlocked Atlantic salmon. Journal of Aquatic Animal Health, Vol. 7(4): 269-273.

Gordon, E. 2012. Investigations of the source, distribution, expression and physiological function of thiaminase I (Honors Thesis). Cornell University.

Morton, A., R. Routledge, and M. Krkošek. 2008. Sea louse infestation in wild juvenile salmon and Pacific herring associated with fish farms off the east-central coast of Vancouver Island, British Columbia. North American Journal of Fisheries Management, Vol. 28:523-532.

Nur-Farhana, A., A. Samat, Z. C. Cob, M. A. Ghaffar. 2013. Stomach content and trophic level position of two bamboo shark species Chiloscyllium indicum and C. Hasseltii (hemiscylliidae) from south eastern waters of peninsular Malaysia. Journal of Sustainability Science and Management, Vol. 8(1): 113-120.

Paiva, M. P. and F. H. Nepomuceno. 1989. On the reproduction in captivity of the oscar, Astronotus ocellatus (Cuvier), according to the mating methods (Pisces - Cichlidae). Amazoniana, Vol. 10(4): 361-377