Lymphocystivirus cause mass mortality events like megalocytiviruses and ranaviruses, fish with lymphocystis exhibit grossly visible papilloma-like skin lesions which substantially reduce their commercial value. No vaccines are currently available for lymphocystis viruses. Group: dsDNA The genus "Lymphocystivirus" has only one species: "Lymphocystis disease virus 1" (LCDV-1), but Lymphocystis disease virus 2 (LCD-2) is another virus that has been proposed as a second member. LCDV-1 infects European flounder "Platichthys flesus" and European plaice ("Pleuronectes platessa"). LCDV-2 infects the common dab ("Limanda limanda"). A third species Lymphocystis disease virus C has also been proposed based on the relative lack of sequence similarity of
Flatfish as an early relative of the flatfish and transitional fossil. In a typical modern flatfish, the head is asymmetric, with both eyes on one side of the head. In "Amphistium", the transition from the typical symmetric head of a vertebrate is incomplete, with one eye placed near the top of the head. The researchers concluded, "the change happened gradually, in a way consistent with evolution via natural selection—not suddenly, as researchers once had little choice but to believe." Flatfishes have been cited as dramatic examples of evolutionary adaptation. Richard Dawkins, in "The Blind Watchmaker", explains the flatfishes' evolutionary history thus: