Whalefishes, bignoses and tapetails – these three groups of deep-sea fishes couldn’t look more different. The whalefishes (Cetomimidae) have whale-shaped bodies with disproportionately large mouths, tiny eyes, no scales and furrowed lateral lines – narrow organs on a fish’s flanks that allow it to sense water pressure.
The tapetails (Mirapinnidae) are very different – they also lack scales but they have no lateral lines. They have sharply angled mouths that give them a comical overbite and long tail streamers that extend to nine times the length of their bodies.
The bignoses (Megalommycteridae) are very different still – unlike the other two groups, they have scales, their mouths are small and their noses (as their name suggests) are very large.
Based on these distinct bodies, scientists have classified these fishes into three distinct families. Now, it seems they are wrong. Amazingly enough, the three groups are all just onesingle family – the tapetails are the larvae, the bignoses are the males and the whalefishes are the females. The entire classification scheme for these fishes needs to be reworked, as many distinct “species” are actually different sexes or life-stages of the same animal.
The transformation from caterpillar to butterfly or moth is one of the most beguiling in the animal world. Both larva and adult are just stages in the life of a single animal, but are nonetheless completely separated in appearance, habitat and behaviour. The imagery associated with such change is inescapably beautiful, and as entrancing to a poet as it is to a biologist.
According to popular belief, within the pupa, the caterpillar’s body is completely overhauled, broken down into a form of soup and rebuilt into a winged adult. Richard Buckmister Fuller once said that “there is nothing in a caterpillar that tells you it’s going to be a butterfly.” Indeed, as the butterfly or moth quite literally flies off into a new world, it is tempting to think that there is no connection between its new life and its old existence as an eating machine.
But not so. A new study has provided strong evidence that the larval and adult stages are not as disparate as they might seem. Adult tobacco hookworms – a species of moth – can remember things that it learned as a caterpillar, which means that despite the dramatic nature of metamorphosis, some elements of the young insect’s nervous system remain intact through the process.