On a New Species of Caligus (Copepoda Parasitica) 
from the Coast of California 
SuEO M. Shiinqi 
Among the material of parasitic copepods 
which Dr. W. L. Klawe of the Inter- American 
Tropical Tuna Commission collected from 
fishes in the eastern Pacific and sent to the 
author for identification, there was an inter- 
esting specimen representing a new species of 
the genus Caligus. The specimen, consisting 
of a single female, was obtained off the coast 
of California. It has been preserved together 
with the host, Engraulis mordax, to whose 
body it was firmly clinging. The present note 
contains the description of this parasite. 
The author wishes to express his thanks to 
Dr. Klawe for providing the present material, 
and takes a great pleasure in associating the 
name of the species with the naturalist. 
Caligus klawei sp. nov. 
Figs. 1-3 
A female found on a specimen of Engraulis 
mordax 7.9 cm. long, taken off Coronado 
Hotel, San Diego, California, late in May, 
1956 . It was clinging to the side of the host 
above the pectoral fin. The anterior region of 
the body is lapped by a fleshy fold which is 
an abnormal outgrowth of host skin caused 
by the presence of the parasite. 
Body flattened, length excluding rami 
5.46 mm., carapace excluding marginal rim 
2.39 rnm. X 1.71 mm., fourth thoracic seg- 
ment 0.21 mm. X 0.61 mm., length of ex- 
posed region of same 0.07 mm., genital 
segment 2.47 mm. long on midline, 2.89 mm. 
long in lateral region, 2.25 mm. wide, abdo- 
men 0.56 mm. X 0.61 mm. Color whitish in 
formalin, without pigment. 
Carapace elongate oval, about three quar- 
ters as wide as long, somewhat more strongly 
1 Faculty of Fisheries, Prefectural University of Mie, 
Tsu-City, Japan. 
convex above than in ordinary case, with 
lateral regions turning downward. Two sides 
very widely curved and fringed by relatively 
narrow rim. Frontal plates two thirds the 
width of carapace, only slightly arched on 
margin and provided with a lunule close to 
each lateral end. Median lobe half as wide as 
the carapace at its base, and about as long as 
it is wide. It is roughly trapezoid in shape, 
with well-rounded corners, and extends con- 
siderably beyond the lateral lobes. Sinuses 
between adjoining lobes are shallow and nar- 
row, opening backward. The transverse dorsal 
rib is placed at about the center of the cara- 
pace, and arches forward to make, together 
with the incurved posterior halves of the 
longitudinal ribs, a continuous semicircle. 
Anterior halves of the latter extend diagonally 
outward, separating narrower lateral areas 
from the broader central area, in the center of 
which the eyes are located. Fourth thoracic 
segment is covered by carapace in front and 
by genital segment in the rear, showing 
merely a very short central region in dorsal 
aspect. Genital segment is a huge quadrangu- 
lar segment which is produced backward on 
either side of abdomen into a pair of oval 
lobes. Anterior end is contracted into a short 
neck, but expanded just behind this abruptly 
to form gracefully round shoulders which 
continue back to slightly arched lateral mar- 
gins. Segment as long as carapace on the mid- 
line, but one fifth longer on the lateral 
region; width across middle of segment is 
one and one third that of carapace. Abdomen 
is about a quarter of preceding segment in 
length, beyond whose lateral lobes it extends 
only a little. It is one-segmented, as long as 
wide, and has slightly undulated sides and 
V-shaped caudal margin. 
351 
