That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  As a child, I constantly combed the pet stores of the Bronx and Manhattan in search of the odd catfishes, lungfishes and eels I so favored.  I distinctly recall first coming upon some creatures labeled as “rubber eels”, and realizing that I was looking at something special – I just didn’t know exactly what!  The blue-gray “fish” were indeed quite rubbery in texture and did look like eels, yet something was “off”.  In time, I learned that these odd beasts were amphibians, specifically aquatic or River Cauca Caecilians, Tylphlonectes natans.

Natural History

Today, so many years later, you can still find these caecilians being sold as rubber eels.  The River Cauca caecilian is one of the few aquatic members of this little studied amphibian order (the Gymnophiona), and, even now, is the only one to regularly appear in the trade, or even in zoos.  They are found only within the drainages of 2 rivers systems in northern Columbia and northwestern Venezuela, and little is known of their lives in the wild.

Aquatic Caecilians in the Aquarium

River Cauca Caecilians are quite hardy when given proper care, and may even surprise you with young, which are born alive and have external gills.  I’ve bred them in a well-filtered (undergravel) 20 gallon aquarium at a pH of 7 and temperature of 76 F, but one experienced keeper advises that they fare better in acidic water, and recommends sphagnum moss as a substrate.  They may reach 24 inches in length, but most top out at 12-16 inches.

Caecilians are quite shy at first, and must be provided with subdued lighting and artificial caves, PVC pipes, live plants and the like as shelter.  Those I’ve kept have become quite bold after a time, leaving their hideouts by day when scenting the earthworms, blackworms and prawn that are their favorite foods.  A few individuals learned to take frozen foods and shrimp pellets, but live food is definitely preferable.

Fish keeping experience will serve you well in caring for these fascinating amphibians…with so much still unknown about them, I hope that more aquarists take up the challenge!

Further Reading

You can read more about this and other caecilians here.

Please write in with your questions and comments. 

Thanks, until next time,

Frank Indiviglio

Tylphlonectes natans image referenced from wikipedia and originally posted by Christophe cagé

I’d like to welcome Frank Indiviglio back to That Fish Blog for another interesting post. Although they’re amphibians, we’ve seen so much of the African Clawed Frog in the aquarium trade, I thought this was appropriate here. Enjoy!

I’ve always been interested in the process by which a species becomes established as a pet. Interesting stories abound, none more so, perhaps, than that of the African clawed frog, Xenopus laevis. Hailing from southern Africa, female clawed frogs were (somehow!) found to possess an unusual trait – exposure to a pregnant woman’s urine causes the immediate release of the frog’s eggs! Dwelling in a harsh habitat, females must be ready to breed on short notice, and nearly always have eggs ready to be fertilized. This, combined with the ease of maintaining them in the lab, soon led to their widespread use in the Hogben Pregnancy Test.

Millions of these frogs were imported to the US in the 1940’s, with many finding their way into the pet trade. Unfortunately, they also made it into local waterways, and today are well established in several states, including Texas, California and Arizona. Ravenous predators, clawed frogs have been implicated in the declines of a number of invertebrate, amphibian and fish species. Recent research also indicates that this species may responsible for starting the worldwide Chitridiomycosis fungal epidemic that is threatening scores of amphibian species.

Feral populations of African clawed frogs are also to be found in Mexico, Chile, France, Italy, Java, Japan, Indonesia, Great Britain, the Ascension Islands and elsewhere. Despite the species’ origins in warm fresh water, one population has adjusted to life in the underground wells of a castle in England, where the water rarely tops 50F, while another group thrives in brackish ponds (they tolerate 40% seawater) in Orange County, California.

These tongue-less, claw-bearing, aquatic frogs make fascinating pets (they are, however, illegal to own in some states). One kept by my frog-enthusiast mother attained 21 years of age, and the published longevity record is 30 years. Unlike most frogs, they will accept non-living food, and thrive upon Reptomin food sticks and frozen fish foods. I’ll discuss the care of clawed frogs and their relatives, African dwarf frogs, Hymenochirus spp. and Surinam toads, Pipa spp., in a future article. Until then, please write in with your questions and observations. Thank you. Until next time, Frank.

You can learn more about this frog’s spread into non-native waters at:
http://www.issg.org/database/species/search.asp?sts=sss&st=sss&fr=1&sn=xenopus&rn=&hci=-1&ei=-1&x=25&y=3

Thanks again for the great article Frank! If you’re interested in reptiles or birds, Frank also contributes to That Reptile Blog and That Avian Blog.

Until Next Time,

Dave