Gyrodactylus salaris

Gyrodactylus salaris, commonly known as salmon fluke, salmon killer, or the Norwegian salmon killer is a tiny <a href="/facts/Monogenea/NtF6bKsp">monogenean</a> <a href="/facts/Ectoparasite/HWPcgky7">ectoparasite</a> which lives on the body surface of freshwater fish. This leech-like parasite has been implicated in the reduction of <a href="/facts/Atlantic_salmon/Pkyou5kA">Atlantic salmon</a> populations in the <a href="/facts/Norwegian_fjords/WowjK4qf">Norwegian fjords</a>. It also parasitises other species, including <a href="/facts/Rainbow_trout/QLSWuo7G">rainbow trout</a>. G. salaris requires <a href="/facts/Fresh_water/xMP2TxwI">fresh water</a>, but can survive in <a href="/facts/Brackish_water/f6z3UXCa">brackish water</a> for up to 18 hours.
The parasite is 0.5 mm (0.02 in) long, and cannot be seen with the naked eye, but it can be seen with a <a href="/facts/Magnifying_glass/3fLtnXwp">magnifying glass</a>. On its <a href="/facts/Posterior_(anatomy)/IpJ1fq2f">posterior</a> end is a <a href="/facts/Haptor/5GQqQTRb">haptor</a>, a specialized organ for attaching to the host fish, which has sixteen hooks around its edge. The parasite is <a href="/facts/Viviparity/EEMn4rVx">viviparous</a>, that is, it produces live offspring. 
The parasites give birth to live young nearly as big as themselves and at this time, a further generation is already growing inside the neonates.

Gyrodactylus salaris open-in-new

Gyrodactylus salaris