|Limnoria with eggs|
The term gribble was originally used for the wood-boring species, especially the first species described from Norway by Rathke in 1799, Limnoria lignorum. The Limnoriidae have species which bore into seaweed and sea grass, as well as wood borers.
There are three genera, Paralimnoria, Limnoria and Lynseia. Limnoria has species in most seas. Those gribbles able to bore into living marine plants are thought to have evolved from a wood (dead plant) boring species.
Gribbles bore into wood and plant material for food. The cellulose of wood is digested. The most destructive species are Limnoria lignorum, L. tripunctata and L. quadripunctata. According to an expert, they are the only animals able to make a cellulase to dissolve plant cell walls. Other animals that eat plant fibres make use of bacteria in their gut to produce the enzyme. Gribbles do not. This has led some biologists to think of biofuels.