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

distal edge, second segment similar to first but with
two inner setae, third segment with 3 inner to terminal
setae, short row of spinules at base of 2 outer spines,
inner spine about twice as long as outer, outer edges
of endopod spines heavily haired. Leg 3 (Figure 5a)
similar to leg 2 except endopod third segment with
2 rather than 3 setae. Leg 4 (Figure 56) coxopod
and basipod similar to leg 3; exopod similar to leg 3
with the following exceptions: spines more slender;
second segment with no spinules at base of outer spine;
third segment with 4 rather than 5 setae; endopod
2-segmented, first segment similar to leg 3, second
segment elongate with stout spinules distally and near
outer distal edge, 2 spines flanking naked, terminal
seta, spines spinulose along edges, lacking terminal
flagella, inner spine slightly longer than outer. Leg 5
(Figure 5c) basal segment with dorsal seta and small
patch of spinules at outer distal corner; free segment
with patch of elongate spinules covering inner half of
lower two-thirds of segment, terminally with inner
spinulose spine and outer seta.
ETYMOLOGY.—The Latin divaricatus ("spreading
asunder at wide angle") refers to the characteristic
appearance of the caudal rami of the female.
REMARKS.—Females of this species can be distinguished
from all previously described members of the
genus by the nature of the exopod spines of leg 3 (see
Discussion) ; they can be separated from the females of
the two following species by the ornamentation of the
ventral surface of the caudal rami and last abdominal
segment. Holobomolochus divaricatus females have
two large patches of stout spinules on the last abdominal
segment, their caudal rami have no surface ornamentation;
H. nudiusculus females have relatively
small patches of minute hairs on the last abdominal
segment; H. asperatus females have 2 large patches
of hairs on the last abdominal segment and a patch
of hairs on the ventral surface of each caudal ramus.
In addition the distal spine of the third exopod segment
of leg 3 is only as long as, or shorter than, the
adjacent spine; in H. nudiusculus and H. asperatus
this spine is longer than the adjacent spine and more
outwardly curved than other spines of the ramus (see
Figures 3a, 6c, 8c).
This copepod is a common parasite on Scomberomorus
brasiliensis, S. maculatus, and S. regalis in the
Western Atlantic from Cape Cod to southern Brazil.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY
Holobomolochus nudiusculus, new species
FIGURES 5d-e, 6, la-b, 96
MATERIAL EXAMINED. — Holotype 9 (USNM
172247), allotype $ (USNM 172248), paratypes
33 5 IS (USNM 172249) from the nasal sinuses of
Scomberomorus sierra from Buenaventura, Colombia
(USNM 218565). In addition 13 collections containing
30 9 1