Parasitic Copepods of Mackerel - and Tuna-like Fishes (Scombridae ...

18
with inner seta finely serrate distally and patch of
spinules along outer distal edge, few spinules on outer
edge, second segment incompletely divided with triangular
patch of spinules proximal to division indicating
probable fusion of second and third segments,
uneven row of stout spinules distally near bases of
terminal seta flanked by 2 spines, seta finely serrate
distally, outer spine similar to those on exopod, inner
spine with fine serrations, outer edge of segment with
two patches of short hairs. Leg 5 (Figure 25b) basal
segment with naked, dorsal seta, patch of spinules on
outer, distal corner; free segment with patch of spinules
on inner edge and a row of stout spinules near
base of each of the following: one, terminal, naked
seta; 3 spines, one on mid-outer edge, one on each
side of terminal seta, all spines stout with broad serrations
distally and fine, terminal flagellurn. Leg 6 (see
Figure 23b) represented by 3 short setae, of about
equal length, on genital segment.
MALE.—Body form as in Figure 25c. Total length
1.78 mm, greatest width 0.78 mm; length of cephalon
0.39 mm. Genital segment (Figure 25d) slightly
wider than long (277 X 300 /mi), abdomen 2-segmented,
segments measuring (length X width) 159
X 177 /an, and 194 X 147 /on; second segment with
two ventral rows of minute spinules (see Figure 25^).
Caudal rami (Figure 25«) longer than wide (141 X
73 fixn) with no ornamentation other than 6 setae
(longest 371 pin).
First antenna similar to that of U. collateralis male.
Remaining cephalic appendages (except rnaxilliped)
similar to those of female. Maxilliped (Figure 26a)
second segment inflated with 2 naked setae and numerous
irregular rows of low, rounded spinules; terminal
segment claw-like with 2 naked setae and row of
teethlike spinules along inner edge to apex.
Legs 1-4 biramous. Leg 1 (Figure 266) basipod
with stout outer seta, patch of hairs near insertion of
rami, inner spine sclerotized at base with terminal
fringed membrane, patch of spinules near base of
spine extending midway up segment; exopod 3-segmented,
first segment with outer spine with stout
terminal flagellum, second segment with inner seta
and outer spine similar to that on first segment, third
segment with 5 setae and 2 outer spines, proximal
spine similar to previous 2, distal spine simple, not
heavily sclerotized; endopod 3-segmented, similar to
U. mycterobius male except patches of hairs on first
and second segments smaller. Leg 2 (Figure 26c)
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
similar to female except exopod setae comparatively
longer; endopod setae longer than and not as robust
as in female and second segment not as inflated. Legs
3 and 4 similar to female. Leg 5 (Figure 26d) basal
segment with dorsal naked seta; free segment ornamented
similarly to female, but segment itself not as
robust.
ETYMOLOGY.—The Latin reductus ("reduced")
alludes to the reduced number of setae on exopods
of legs 2-4 and the reduced number of segments of
the endopod of leg 4.
REMARKS.—Females of U. reductus can be distinguished
from other Unicolax by the following characters:
the ventral surface of the last abdominal segment
has' no ornamentation; the caudal rami have
only six setae each, with no ventral hairs or spinules
(other species have a ventral patch of hairs on each
ramus); leg 2 exopod third segment has 3 spines,
4 setae (other species have 4 spines, 5 setae); leg 3
exopod third segment has 4 setae (other species have
5) ; leg 4 exopod third segment has 3 setae (U. collateralis,
U. mycterobius, and U. ciliatus have 5, U.
anonymous has 4) ; leg 4 endopod is 2-segmented (in
all other species it is 3-segmented).
Males of U. reductus differ from others of the genus
by the following characters: the ventral surface of
the last abdominal segment is ornamented by only 2
distal rows of minute spinules; the caudal rami have
no ornamentation on the ventral surface (other males
have a patch of hairs on the ventral surface of each
ramus). Legs 3, 4, and 5 are strikingly similar to those
of the female, while the legs of males of others in
the genus differ in several ways from their female
conspecifics.
Unicolax reductus is the only member of the genus
found on Katsuwonus pelamis and is probably restricted
to that host species.
Because of the number and nature of its unique
characteristics, it is the most easily identified member
of the genus.
Ceratacolax Vervoort, 1965
Ceratacolax enthynni Vervoort, 1965
FIGURES 27-31, 100, 122c-/, 123-125
Ceratacolax euthynni Vervoort, 1965:26.
MATERIAL EXAMINED.—34 collections containing
94 9 and 63 S from the following hosts and localities: