Two apolipoproteins in salmon louse (), apolipoprotein 1 knock down reduces reproductive capacity.

The salmon louse, is an ectoparasite of salmonid fish in the Northern Hemisphere, causing large economical losses in the aquaculture industry and represent a threat to wild populations of salmonids. Like other oviparous animals, it is likely that female lice use lipoproteins for lipid transport to maturing oocytes and other organs of the body. As an important component of lipoproteins, apolipoproteins play a vital role in the transport of lipids through biosynthesis of lipoproteins. Apolipoproteins have been studied in detail in different organisms, but no studies have been done in salmon lice. Two apolipoprotein encoding genes ( and ) were identified in the salmon lice genome. Transcriptional analysis revealed both genes to be expressed at all stages from larvae to adult with some variation, generally higher than and both at their highest levels in adult stages of the louse. In adult female louse, the and transcripts were found in the sub-epidermal tissue and the intestine. RNA interference-mediated knockdown of and in female lice resulted in reduced expression of both transcripts. knockdown female lice produced significantly less offspring than control lice, while knockdown of in female lice caused no reduction in the number of offspring. These results suggest that has an important role in reproduction in female salmon lice.