With their large flattened heads, small beady eyes and slimy skins, Japanese giant salamanders are not destined to take home the prize for "best-looking". However, according to a team of scientists they may just be eligible for the most "awesome dad" award, at least amongst amphibian males who are not known for their nurturing personalities.
Measuring almost 5-feet long, the ancient animal that has inhabited earth for over 20 million years, ranks amongst the largest of all amphibians, second only to their close relatives, the Chinese giant salamanders. Found in the rivers of northern Kyushu Island and western Honshu in Japan, they spend their entire lives in freshwater.
Every year during breeding season, large males called "den-masters", create burrows or dens along the stream banks, that are accessible only to females. However, unlike many other salamander species, the females leave soon after laying a string of between 300-600 fertilized eggs. It is the males that remain behind to ensure the unborn babies are taken care of. The well-kept secret of this ancient creature was unearthed and published on November 11th in the Journal of Ethnology, by Japanese biologists Sumio Okada, Yukihiro Fukuda, and Mizuki Takahashi.
The biologists conducted their research by videotaping the dens of two male salamanders. Though both were located in Japan's streams, one was a natural nest while the other was built by conservationists. The scientists observed three interesting nurturing techniques.
The first was tail fanning. The researchers believe that this was done to ensure water circulation so that the developing eggs would have better exposure to oxygen. What was interesting was that to make up for the lower quantity of oxygen, the den master in the artificial nest fanned longer and more vigorously, than the one that was guarding the natural nest.
The dads also used their heads and bodies to agitate or stir the eggs. Okada and his colleagues believe this may be to prevent yolk adhesions so that the embryos can develop properly. It was also an effective way to protect the eggs against small predators.
While these actions were certainly heartwarming, it was the third that put these amazing dads at the top of the list - the consumption of a few eggs. While some fish fathers are known to do that when they get hungry, such was not case with these giants whose slow metabolism allows them to survive without food for weeks if necessary.
What the researchers noticed was that the salamanders only consumed eggs that had a whitish appearance, leading them to suspect that the embryos were either unfertilized, dead or infected with water mold. Okada's team believes that the protective fathers swallowed the eggs as a way to protect their young from getting infected.
The researchers suspect that it is not just the Japanese giant salamanders but also, their larger counterparts, the Chinese giant salamanders that are equally nurturing. Though the biologists did not reveal what led them to observe the parenting behavior of the amphibians, it may have to do with the conservation efforts that are currently underway, to save the animals that are disappearing rapidly due to loss and destruction of habitat, and previous hunting.
Resources: wired.com, wikipedia.org, springer.com