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

28 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
(Figure 536) exopod 2-segmented, first segment with
prominent spine at outer distal corner, second segment
with 3 terminal and 1 lateral spine, distalmost longest
(setae measure 177, 112, 83, 83, 124 fim distal to
proximal respectively). Leg 5 represented by 3 short
setae near posterior corner of genital segment.
MALE.—None collected.
REMARKS.—This species is apparently common on
a number of host species in the western Atlantic and
Gulf of Mexico (scombrid and non-scombrid). It
has also been reported from the Gulf of California
and Pacific coast of Mexico from a number of host
species by Causey (1960:329) and Wilson (1937:27).
We describe here a new, closely related, species of
Caligus from eastern Pacific Scomberomorus and it
seems likely that at least some of the specimens reported
by these 2 authors may have been the new
species. None of that material has been deposited in
the Smithsonian collections so we have not been able
to verify the identifications.
Examination of the type-specimens (USNM 6155)
from Woods Hole, Mass, indicate variation from our
specimens on at least 2 points. The outermost of the
4 terminal setae on the caudal rami of the type specimens
is less than half the length of the outer edge of
the ramus, whereas in our specimens that seta is
almost as long as the outer edge of the ramus. The
longest seta on the exopod of leg 4 of the type specimens
is only slightly longer than the adjacent seta
(218 and 177 /*m) whereas in our material this seta
is much longer than the adjacent seta (177 in 112
/*m). We do not consider these differences important
enough to warrant describing a new species but rather
may reflect ecological differences between the 2 groups
of material.
Caligus omissus, new species
FIGURES 53c-e, 54-56, 105
MATERIAL EXAMINED.—58 collections containing
147 9 41 S from the gills, gill arches, gill rakers, inner
operculum, and roof of the mouth from 41 specimens
(114 examined) of Scomberomorus sierra from Peru,
Colombia, Panama, Costa Rica, Pacific coast of Mexico,
and Baja California; from 7 specimens (47 examined)
of Scomberomorus concolor from off Sonora,
Mexico and Gulf of California. Holotype (USNM
172239), allotype (USNM 172240) and 40$ 3*
paratypes (USNM 172241) from the gills of S. sierra
from San Juan Lagoon, Mexico (USNM 219623).
FEMALE.—Body form as in Figure 53c. Total length
2.96 mm (2.78-308 mm) based on an average of 6
specimens from the type series. Greatest width 1.15
mm (1.12-1.19). Cephalon comprises about 40 percent
of total length. Frontal lunules prominent,
diameter of lunule (266 /*m) slightly more than
least distance (218 /*m) between lunules (interlunular
space). Genital segment (Figure 53d) slightly longer
than wide (1.16 X 1-09 mm), posterior corners
rounded, only slightly produced, comprising about 30
percent of total length. Abdomen (see Figure 53d)
1-segmented, nearly 3 times as long as wide (0.96 X
0.36 mm), usually slightly wider in posterior third
but never noticeably wider in anterior half; distal
ventral surface with patches of spinules as in Figure
53*. Caudal rami (see Figure 53e) longer than wide
(142 X 94 fixn) armed with 6 plumose setae as indicated
in figure, longest seta 307 /*m.
Oral area as in Figure 54a. First antenna (Figure
546) first segment with 27 setae, all plumose except
2 in middle anterior group; last segment with 13
naked setae. Second antenna (Figure 54rf) with
prominent hook, basal segment with conspicuous
pointed posterior process. Post antennal process (Figure
54c) a prominent recurved hook. Postoral process
(Figure 54e) with slight outward curve, extending
well beyond tip of mouth tube. Maxilliped (Figure
54/) with a strongly sclerotized, recurved claw.
Sternal furca (Figure 54g) with widely divergent
tines, each with a blunt tip.
Leg 1 (Figure 55a) basipod with a patch of
prominent spinules covering two-thirds of ventral
surface; exopod first segment with row of spinules
along inner edge and short, naked spine on outer
distal corner; exopod with 3 terminal spines (2 with
accessory spines), 1 terminal seta (plumose on outer
edge), and 3 lateral setae with stout spinules on base
of outer edge of each followed by short plumosities;
endopod reduced to a short process with 2 small distal
spines. Leg 2 (Figure 556) as in other species of the
genus except exopod spine on outer distal corner of
last segment very small; endopod first segment with
3-4 stout spinules on outer distal corner, second segment
with a double row of stout spinules along outer
edge, a patch of 4-5 short spinules on proximal outer
edge of last segment, all segments with plumose setae
as in figure. Leg 3 (Figure 55c) basipod with con-