Comparative Parasitology 68(2) 2001 - Peru State College

220 COMPARATIVE PARASITOLOGY, 68(2), JULY 2001
ville, Maryland, U.S.A., and the Harold W. Manter
Laboratory (HWML) of the University of Nebraska
State Museum, Lincoln, Nebraska, U.S.A.
Description
Results
Ommatobrephidae Poche, 1926
Singhiatrema vietnamensis sp. n.
(Figs. 1 and 2)
Based on 5 specimens: Ommatobrephinae
Poche, 1926. Body pyriform, elongate, 2.56 mm
(2.41-2.61 mm) long, 0.76 mm (0.76-0.91 mm)
wide at maximum width near posterior end of
body, lacking tegumental spines but possessing
minute interrupted longitudinal striae. Oral sucker
with subterminal mouth, 170 (170—207) long,
189 (189-217) wide. Head crown having single
row of 22—23 spines 31—56 long, arranged 11—
12 per side; row interrupted dorsally and ventrally.
Prepharynx short, less than % length of
pharynx; pharynx oval, 95 (95-106) long, 78
(78-106) wide. Esophagus 640 (547-640) long,
89 (80—105) wide. Ceca extending beyond posterior
extent of testes. Acetabulum 290 (285-
329) long, 379 (363-407) wide, lying between
anterior % and anterior J/2 of body. Ratio of
widths of oral sucker to acetabulum 1:1.8-2.0.
Testes 2, weakly (incompletely) lobed, lying
opposite, located near terminal end of body, with
anterior margins diverging from each other; left
testis 292 (285-340) long, 217 (200=234) wide;
right testis 279 (251-335) long, 234 (195-234)
wide. Cirrus sac oval, 179 (179-227) long, 102
(102—110) wide, medial, lying between cecal bifurcation
and acetabulum, containing large bipartite
seminal vesicle, short pars prostatica, and
short muscular ejaculatory duct; pars prostatica
a short duct surrounded by prostatic cells at anterior
of sac; external seminal vesicle lacking.
Ovary pretesticular, spherical, 73 (73-95) in
diameter, slightly dextral in 4 of 5 specimens,
slightly sinistral in 1 specimen. Oviduct communicating
with Laurer's canal, then forming
ootype; Laurer's canal straight, directed dorsally
from region of ootype, opening on dorsal surface
at level of ovary; ootype surrounded by
Mehlis' gland; Mehlis' gland compact, usually
larger than ovary, consisting of relatively small
cells; ootype receiving relatively long common
vitelline duct from vitelline reservoir, communicating
with uterus; uterus intercecal, postacetabular,
with proximal portion a uterine seminal
Copyright © 2011, The Helminthological Society of Washington
receptacle and with distal portion a metraterm;
metraterm thick walled, approximately length of
cirrus sac, sinistral to cirrus sac, entering genital
atrium anteriorly; genital atrium relatively small,
ventral to anterior portion of cirrus sac in heatkilled
specimens (directed anteriorly in coldkilled
specimens when fixed under pressure with
cirrus sac displaced anteriorly); genital pore
opening medially or submedially near anterior
region of cirrus sac in heat-killed specimens
(near anterior acetabular margin in contracted
specimens). Vitellarium consisting of 2 lateral
bands of irregularly shaped follicles; bands lying
ventral to ceca between posterior level of acetabulum
and middle of testes, communicating to
vitelline reservoir by left and right transverse
main collecting channel; left channel about 195
long, right channel about 223-280 long; vitelline
reservoir approximately 45—56 long, 111-195
wide. Eggs 95-117 long, 61-75 wide, with
thickened knob at posterior end, with eyespots
visible in miracidia of some specimens; eyespots
2, lightly pigmented in developing miracidia,
darkly pigmented and fused in developed miracidia.
Excretory vesicle Y-shaped, with triangular
posterior bladder; main stem slender, medial,
concealed by overlapping lobes of testes, extending
anteriorly from bladder and bifurcating
at anterior margins of testes; arms reaching anteriorly
to approximate level just posterior to
pharynx; excretory pore subterminal, opening
on dorsal surface.
Taxonomic summary
TYPE HOST: Enhydris chinensis (Gray,
1842), rear-fanged water snake or Chinese water
snake (Colubridae). Other host: Enhydris plumbea
(Boie, 1827), rear-fanged water snake, rice
paddy snake, or plumbeous water snake (Colubridae).
TYPE LOCALITY: Ha Noi Province, Vietnam.
Other localities: throughout Red River Delta, Vietnam,
in Nam Ha, Thai Binh, Nam Ha, Nam
Dinh, Hai Duong, and Hai Phong provinces.
INFECTION SITE: Small intestine.
PREVALENCE AND INTENSITY OF INFECTION: Ten
of 43 specimens of E. chinensis (23%) each
hosted 1-5 individual worms; 9 of 51 specimens
of E. plumbea (18%) each hosted 1—3 worms.
SPECIMENS DEPOSITED: Holotype USNPC No.
90037; paratypes USNPC No. 90038, HWML
Nos. 15388 (E. chinensis), 15389 (E. plumbea).