Comparative Parasitology 67(2) 2000 - Peru State College

vae from Temazcal and 3 from Culiacan were washed
in distilled water and stored in a refrigerator until the
worms relaxed completely. They were then fixed in
10% formalin for 7 days. The larvae then were washed
overnight in running tap water to remove the fixative
and were transferred to distilled water. The specimens
were rinsed twice in Millonig's phosphate buffer and
postfixed overnight in 0.5% OsO4 in the same buffer.
All specimens were then carefully and gradually dehydrated
in an ascending series of ethanol, since such
specimens often shrink or have surface wrinkles because
of rapid dehydration. They were transferred into
amyl acetate and CO2 critical-point dried with a Hitachi
HCP-2 dryer (Tokyo, Japan). The specimens
were sputter-coated with gold and examined with a
JEOL JSM-U3 SEM (Tokyo, Japan) operated at 15 kV.
Results
As many as 570 larvae were obtained from
the 3 pelicans in Temazcal. Only 3 larvae were
found in 5 egrets in Culiacan. The mean body
length (10 larvae) was 4.67 mm, measured in a
relaxed state after natural death in cold distilled
water. The heads had 4 transverse rows of hooklets
(Fig. 1), and the mean number in each row
was 40, 44, 47, and 50 booklets. The typical
hooks on the head bulb had sharp tapering points
composed of hard keratin that emerged from an
oblong chitinous base (Fig. 2). The bodies were
wholly covered with minute cuticular spines
along their transverse striations. The mean number
of striations varied from 227 to 275. A pair
of cervical papillae was laterally situated between
the 13th and 17th transverse striations
(Fig. 3). In most specimens, the papillae were
located between the 14th and 15th striations. A
ventral excretory pore was located between the
24th and 28th transverse striations (Fig. 4). A
wide terminal anal opening was visible on the
ventral surface, and the transverse striations on
the body were limited to the extent of this opening
(Fig. 5). Both ends of the larva had a pair
of lateral phasmidial pores (Fig. 6).
The intestinal cells had multiple nuclei in the
larvae from Temazcal (Fig. 7). The larvae from
Sinaloa had 2 to 7 nuclei in each intestinal cell
(Fig. 8).
Discussion
Lamothe-Argumedo et al. (1989) determined
their larval gnathostome specimens obtained
from Temazcal to be Gnathostoma sp. However,
based on our observations, their specimens
seemed to be the same as those reported by Almeyda-Artigas
(1991); both specimens of larvae
were from both fish and waterfowl in the same
KOGA ET AL.—SURFACE ULTRASTRUCTURE OF GNATHOSTOMA 245
endemic area of human gnathostomiasis, and the
descriptions of the larval morphology were quite
similar. We attributed this specimen as G. binucleatum.
Lamothe-Argumedo et al. (1989)
had previously observed larvae in Oaxaca, Temazcal,
Mexico. We think that their SEM observations
were insufficient, especially regarding
the location of excretory pores and numbers of
the transverse striations on the larval bodies. We
reexamined the Temazcal specimens using SEM
and made some new observations. We also examined
the surface structures of the specimens
from Sinaloa, Culiacan. Previously, 5 specimens
from Sinaloa were examined by Camacho et al.
(1998) using SEM. They mentioned the numbers
of booklets of 4 rows on the head bulb as 39,
42, 44, and 49. Furthermore, they recognized 1
pair of cervical papillae located between the
13th and 15th striations of the cuticular spines
on a single larva. The number of transverse striations
on the body was more than 200. There
were no descriptions regarding the location of
the excretory pore. The locations of the cervical
papillae, the excretory pore, and the number of
transverse striations are very important for the
identification of species of gnathostome larvae.
As shown in Table 1, the number of transverse
striations is more than 200 in G. spinigerum.
However, the number is less than 200 in most
specimens of G. doloresi. On the other hand, the
cervical papillae and excretory pores of G. hispidum
were situated more anteriorly than those
of the other 2 species.
In the present study, we compared the larvae
from 2 districts in Mexico, Temazcal and Culiacan,
and found no differences between them in
the larval morphology (Table 1). In particular,
the surface ultramorphologies were very similar.
However, when our findings were compared
with those of G. spinigerum in Thailand (Table
1), they were the same, including the shape of
the larval hooks, which had oblong chitinous bases
and are known to be one of the characteristic
structures of G. spinigerum (Miyazaki, 1960).
Akahane et al. (1994) also compared the number
of booklets in each row on the head bulb of the
Temazcal larvae and the larvae of G. spinigerum
in Thailand by light microscopy and concluded
that the numbers of booklets in Temazcal larvae
were slightly less than those of G. spinigerum.
The intestinal epithelium of Temazcal specimens
consisted of a single layer of intestinal
cells, and each columnar cell had 2 to 5 nuclei
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