- Specimens of the starry flounder, Platichthys stellatus
(Pallas, 1811) Girard, 1854, were collected in
Yaquina Bay near Newport, Oregon, from July, 1970, to August,
1971. Fish infected with Lepeophtheirus hospitalis
Fraser, 1920, were transported to Corvallis, Oregon, and
maintained in a sea water system at 15°C. Isolated copepods
were studied in finger bowls in non-aerated sea water.
which was changed several times daily.
The morphology and behavior of the ten life history
stages of the parasitic copepod L. hospitalis have been
described. Measurements and figures for all stages were
Adults are motile ectoparasites on the ventral surface
of the starry flounder. They adhere with prehensile second
antennae, maxillipeds, and a suction cup action produced
by the arched cephalothorax. The primary food was slime,
but if an abrasion or cut was present, blood was sometimes
ingested. Seasonal abundance of the parasite in Yaquina
Bay seemed to be correlated with the amount of fresh water
flowing through the bay.
Ovulation and egg string formation occurred simultaneously
at night. At 20°C, 64 hours elapsed between ovulation
and hatching. The major features of ovulation, egg
string formation, embryology, and hatching have been
The two unsegmented naupliar stages were free-swimxning,
positively phototropic, and possessed three pairs of
appendages: first antennae, second antennae, and mandibles
all of which were used in swimming. The duration of the
first naupliar stage at 20°C was seven and a half hours
and at 15°C about 24 hours. For the second nauplius these
times were 11 and 40 hours respectively. Mortality on the
molts following each of these two stages was less than five
percent and five to ten percent.
The segmented body of the copepodite possessed those
appendages present on the naupliar stages, and added the
post oral processes, maxillae, maxillipeds, the first two
pairs of thoracic legs, and the caudal rami. This stage
was free-swimming, but died in three to eight days, at
20°c, if a host was not located. Copepodites held onto the
flounder with their prehensile second antennae for four to
six days, at 15°c, at which time they formed attaching
filaments. This process began with a series of rapid jabs
to the host substrate by the anterior cephalothorax. A
droplet of frontal organ secretion appeared between copepodite
and host and was pulled out into a filament which
hardened immediately. At 15°C the molt to the first
chalimus stage took place 36 to 48 hours after filament
formation. Laboratory mortality from copepodite to first
chalimus was over 95 percent.
The six chalimus stages at 20°C lasted 6½, 5, 4½, 2½,
2, and 1 days respectively. The first four stages were
attached by a frontal filament, the fifth was usually
unattached, and the sixth was always unattached. Sexual
differentiation became evident in the fifth chalimus:
males possessed a sixth pair of legs, females did not.
Sixth chalimus males were usually found coupled to adult
females or mobile chalimus stages of either sex. The
third and fourth pairs of legs appeared in the first chalimus
stage. The post antennal processes and fifth pair of
legs were new structures in the third chalimus, and the
sternal furca was new to the fourth chalimus.
The above mentioned times, changes, and behavior were
compared to that of other caligids. Possible functions
for all appendages and processes previously proposed were
given and it was herein suggested that the post oral process
serves to protect the mouth cone.