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Today on Animal Fact Files we’re discussing salamanderfish. Is it a salamander or a fish? Who knows! No, seriously; taxonomically speaking, these fish aren't like any other known living fish species, so determining their closest living relative has been hotly debated. It's likely they're related to Australian mudfish, but as it stands the salamanderfish is the only member of its family and has a dubious position on the tree of life.

Just like their potential relatives, the salamanderfish lives in Australia. This species is endemic to the southwest corner of the country, where it is only known from swamps, streams, and other acidic water systems in this region. These vertebrates spend the rainy season eating and procreating, enjoying the murky, tea-colored, acidic water of their home. But this opulence doesn't last. The summer is hot and dry. Salamanderfish have a strategy to combat this though!

When summer heat evaporates all the water in its range, the salamanderfish burrows into the damp ground and takes a nap. It's called aestivation, and it's somewhat like hibernation. In this low-energy state underground, the fish breathes through its skin, retains all its urea, and survives off its fat reserves built up over the rest of the year. The salamanderfish can remain in this state for months at a time, but when rare summer rains briefly refill its home, it pops back up for a brief touch of the sun, only to burrow again when the water dries out.

Salamanderfish get their name not just for their look, but for their salamander-like movement. They “walk” on their fins across the bottom. They can also bend their neck! Salamanderfish are unable to move their eyes, so, to compensate, they simply developed the capacity to move their head separately from their body. This is essentially non-existent in other fish species, and a large part of what sets this particular species apart from all others! Unlike salamanders, however, salamanderfish have scales.

Even without their swiveling cranium, salamanderfish can be identified by their unique appearance. They have a long, cylindrical body with red eyes, a pale belly, and an olive-toned back with silver specks and dark blotches. What's more– they’re tiny! Males top out at just 2 inches, 5 centimeters, in length while females are slightly longer maxing out at just over 3 inches, 8 centimeters, long.

Even a tiny creature can have a big appetite. Salamanderfish are carnivores. They eat crustaceans, insect larvae, and other small invertebrates. On the other hand, these fish are threatened by habitat loss. Their fragile habitat is shrinking due to changes in the climate that have expedited in the past 20 years. As of this recording, the salamanderfish is listed as endangered.

When water is plentiful, salamanderfish get busy. Males use a modified, sticky anal fin for internal fertilization; this is unusual among fish. Females lay up to 400 eggs, which hatch into fast-growing larvae. Most won’t breed until their second winter, but about 25% mature in their first year. Salamanderfish usually live three years, but some can reach the age of five.

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