A fascinating article in Livescience reveals the answer to a century-old zoological mystery: what do y-larvae grow up to become? Discovered in 1899, y-larvae are clearly young crustaceans but their adult stage could not be determined. While this in itself was perplexing, the newly discovered answer is even more startling: y-larvae metamorphosize into “simple, pulsing, slug-like masses of cells… far simpler than their larval stage.” In a sense, the creatures revert backwards to forms more commonly seen further down the evolutionary ladder as they mature.
Watch the process
This awesome video shows the transformation from promising young crustacean to parasitic adult slug monster. Would make a great anti-drug commercial.
As Y-larvae do not seem to be in any rush to grow into their adult form naturally (and who can blame them) the researchers used powerful hormones to induce rapid growth. The scientists theorized that adult y-larvae, or ypsigons (rolls right off the tongue…), are parasitic as they have no digestive tract or nervous system. This means that they would need to absorb nutrients from their surroundings. Some species of parasitic barnacles exhibit similar physiological changes during development.