Longest worm eel

Worm eels belong to the taxonomic family Colocongridae, and are also known as short-tailed eels. The longest species currently known from adult specimens (some are known only from their larval, leptocephalus stage) is Cadenat's worm eel Coloconger cadenati, in which adult males can attain a total length of up to 90 cm. Other species rarely exceed 60 cm. It is a deepwater species native to the east Atlantic off West Africa.

The most mystifying worm eel is provisionally known as Leptocephalus giganteus, because its only recorded specimens are leptocephali, but of remarkably large size – the biggest, captured off South Africa in January 1930, measured almost 1.9 m long! Based on this, estimates of how big its still-unknown adult form might be, taking into account the rate of increase normally exhibited by true eels, have yielded incredible lengths of up to 55 m! However, some ichthyologists believe that these unusually big leptocephali are actually larval spiny eels (notacanthids), which are actually smaller as adults or stay the same size, rather than increasing. Similarly, worm eels do not greatly increase in size during metamorphosis either.