Sea
Lice Life Cycles
The
sea lice life cycle consists of 10 different stages (plus the egg stage),
with a moult between each one. The entire life cycle for Lepeophtheirus
salmonis is about 7-8 weeks at 10oC, and for Calimus
elongatus, it is about 6 weeks.
The life
cycle for L. salmonis includes nauplii, copepodid,
calimus,
preadult and adult stages.
The life
cycle for C. Elongatus includes nauplii, copepodid,
calimus,
and adult stages.
The first stages in
the life of a sea louse after it has hatched out of its egg is the Nauplius
I & II stages. At this point, it is free swimming, and has very
noticeable appendages.
The next stage is the
Copepodid stage. This is another free swimming stage, but the organism
takes on a more rice like shape, with less noticeable appendages.
After the Copepodid
stage comes the first parasitic stages - the Chalimus I-IV stages.
At this stage, the louse develops a structure called a frontal filament
which allows the louse to attach to the fish. Chalimus are often
seen hanging off the edge of gills and fins.
Chalimus larvae then
moult into preadults (in L. salmonis). The preadult stage is usually
not attached to the fish by a frontal filament, however it often buries
under scales to keep very close to the host.
Once they reach the
adult stage, the sea lice are easily seen with the naked eye. The male
is smaller, and the female has wider "hips". Females that have eggs
keep them in long strands that trail behind them.
