Something fishy is happening in the mangrove forests of the western Atlantic. A fish is living in the trees.
The mangrove killifish (Kryptolebias marmoratus) is a tiny fish that lives in ephemeral pools of water around the roots of mangroves. When these dry up the 100-milligram fish can survive for months in moist spots on land. Being stranded high and dry makes it hard to find a mate, but fortunately the killifish doesn't need a partner to reproduce. It is the only known hermaphrodite vertebrate that is self-fertilising.
Now biologists wading through muddy mangrove swamps in Belize and Florida have discovered another exceptional adaptation. Near dried-up pools, they found hundreds of killifish lined up end to end, like peas in a pod, inside the tracks carved out by insects in rotting logs. "They really don't meet standard behavioural criteria for fish," says Scott Taylor of the Brevard County.
Okay.