One of the reasons why these studies were initiated was that the salmon louse appeared to have an unusually large number of larval stages compared to related animals. Originally, salmon louse was described to have nine larval stages, but this new study shows that in fact, it only has seven.
-The two stages that have “disappeared” are chalimus stages, where the louse is attached to the host fish by a filament. These stages are difficult to follow since they are small and sitting on the fish. This is one of the reasons why the number of stages was determined wrongly. Also, this new study has revealed that chalimus larvae grow in size between the molt events. Normally, animal with an exoskeleton need to molt to expand in size, the researchers involved in the study says. According to them, it has now been established that the salmon louse chalimus larvae also expand in size between molts.
The new results are important both for researchers and for the aquaculture industry.
- As a researcher it is obviously important to have as much knowledge as possible about the animal that we study, says the researchers. For the industry information understanding the lifecycle and the number of molts, is interesting because some of the compounds that can be used against salmon lice infestation are inhibitors of the molting process.
The results are published in the scientific journal PlosONE. The article "The Salmon Louse Lepeophtheirus salmonis (Copepoda: Caligidae) Life Cycle Has Only Two Chalimus Stages" has been written by researchers from Institute of Marine Research, University of Bergen (Sea Lice Research Centre), Bergen, Norway, University of Sterling and Natural History Museum in London, both in the UK.