Freda Kreier in Nature:
An egg-laying amphibian found in Brazil nourishes its newly hatched young with a fatty, milk-like substance, according to a study published today in Science1.
Lactation is considered a key characteristic of mammals. But a handful of other animals — including birds, fish, insects and even spiders — can produce nutrient-rich liquid for their offspring.
That list also includes caecilians, a group of around 200 limbless, worm-like amphibian species found in tropical regions, most of which live underground and are functionally blind. Around 20 species are known to feed unborn offspring — hatched inside the reproductive system — a type of milk. But the Science study is the first time scientists have described an egg-laying amphibian doing this for offspring hatched outside its body.
The liquid is “functionally similar” to mammalian milk, says study co-author Carlos Jared, a naturalist at the Butantan Institute in São Paulo, Brazil.
More here.