Overfishing is good news for tongue eating parasites!

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New research into a sinister tongue eating parasite, Cerathotoa italica has found how overfishing is helping its population grow.

A team from the University of Salford, University College Dublin and the University of East Anglia inspected stocks of Striped sea bream (Lithognathus mormyrus) in two areas of the Mediterranean, one a marine protected zone, the other open to heavy commercial fishing.

They recorded numbers of the gruesome freeloaders, as well as the general size and condition of the luckless host fish.

The results were startling. In the protected zone 30% of the fish studied were hosts to the tongue chomping isopod, but in the overfished area this leapt to 47%.

The combination of overfishing and an abundance of the parasites also meant that fish from the unprotected zone were smaller and in worse physical condition that those caught in the protected zone, even when these fish also had the parasite.

This appears to back up the theory that human activity can create environmental differences which influence the fitness and life history of host fish populations, meaning fish in overfished areas need to mature more rapidly and at smaller sizes to reproduce than they would otherwise, and as a result are becoming less able to defend themselves against parasites.

The parasite Cerathotoa italica comes from the Cymothoidae family of isopods, which includes several tongue eating species. Host fish species are targeted by the isopods which swim into their mouths via the gills. Once inside they eat the luckless victims tongue, before sitting in the space left behind, feeding vampire like on the fishes blood.

For more information see the paper; SALA-BOZANO, M., VAN OOSTERHOUT, C. and MARIANI, S. (2012), Impact of a mouth parasite in a marine fish differs between geographical areas. Biological Journal of the Linnean Society, 105: 842ñ852. doi: 10.1111/j.1095-8312.2011.01838.x

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