Comparative Parasitology 68(2) 2001 - Peru State College

Comp. Parasitol.
68(2), 2001, pp. 219-227
Singhiatrema vietnamensis sp. n. (Digenea: Ommatobrephidae) and
Szidatia taiwanensis (Fischthal and Kimtz, 1975) comb. n. (Digenea:
Cyathocotylidae) from Colubrid Snakes in Vietnam
STEPHEN S. CURRAN,' ROBIN M. OVERSTREET,U DANG TAT THE,2 AND NGUYEN THI LE2
1 The University of Southern Mississippi, Gulf Coast Research Laboratory, P.O. Box 7000, Ocean Springs,
Mississippi 39566, U.S.A. (e-mail: robin.overstreet@usm.edu and stephen.curran@usm.edu) and
2 Institute of Ecology and Biological Resources, Nghia do, Cau Giay, Hanoi, Vietnam (ntminh@ncst.ac.vn)
ABSTRACT: A new digenean is described and a second species is redescribed from the colubrid rear-fanged
water snakes Enhydris chinensls (Gray) and Enhydris phunbea (Boie) captured from several regions in Vietnam
during 1996-1998. Singhiatrema vietnamensis sp. n. (Ommatobrephidae) from the small intestine of both snakes
is characterized by the extent of the ceca, the position of the vitellaria, the size of the eggs, and the host. Szidatia
taiwanensis (Fischthal and Kuntz, 1975) comb. n. (Cyathocotylidae) is redescribed from the holotype and specimens
from the gallbladder of both snakes. The species is transferred from the genus Mesostephanoides primarily
because it does not have a large cirrus that is spined; it is characterized by the shape of the seminal vesicle,
length of the ceca, body size relative to the forebody, number of testes in hindbody, egg size, size of tribocytic
organ, and the infection site in the host. Concerning the classification of Singhiatrema Simha within Echinostomatiformes,
we consider Singhiatrematinae Simha a junior synonym of Ommatobrephinae Poche. We discuss
the classification of Gogatea Lutz and Szidatia Dubois and consider Gogatinae Mehra a junior synonym of
Szidatiinae Dubois. The use of different fixation methods can produce artifacts characteristic at the generic level.
KEY WORDS: Singhiatrema vietnamensis sp. n., Ommatobrephidae, Szidatia taiwanensis comb, n., Cyathocotylidae,
fixation artifacts, Enhydris chinensis, Enhydris plumbea, Colubridae, snakes, Vietnam.
Two unrelated digeneans, a new intestinal ommatobrephid
and a gallbladder cyathocotylid,
each infecting 2 species of rear-fanged colubrid
water snakes (Enhydris chinensis (Gray, 1842)
and Enhydris plumbea (Boie, 1827)) from Vietnam,
are herein described. The life history of
neither parasite is known. The new ommatobrephid
is most similar to species of Singhiatrema
Simha, 1954, which are usually found in the intestines
of water snakes. Exceptions include
Singhiatrema najai Chattopadhyaya, 1967, from
the intestine of the Indian cobra Naja naja (Linnaeus,
1758), and Singhiatrema lali Chakrabarti,
1967, from the intestine of a freshwater emydid
turtle (Hardella thurgii (Gray, 1831)) (Chattopadhyaya,
1967). All prior known species are
reported from the Indian subcontinent only.
The gallbladder cyathocotylid that we found
in Vietnam also occurs in one of the same hosts
in Taiwan. It exhibits a relationship with Szidatia
joyeuxi (Hughes, 1929), which infects the intestine
of the colubrid water snake Matrix maura
(Linnaeus, 1758) (as Tropidonotus viperinus
(Sonnini and Latreille, 1802)) in an oasis in Tunis,
Morocco, and has a cercaria that is shed
from the freshwater snail Melanopsis sp. and de-
Corresponding author.
219
velops in the leg muscles of the frog Rana rudibunda
Pallas, 1771 (as Rana esculenta rudibunda;
see Langeron, 1924; Hughes, 1929; Dubois,
1938).
Materials and Methods
The second and third authors captured a total of 43
specimens of E. chinensis and 51 specimens of E.
plumbea in Ha Noi, Nam Ha, Thai Binh, Na Nam,
Nam Dinh, Hai Duong, and Hai Phong provinces (Red
River Delta) in Vietnam. They collected digeneans live
from the intestines and gallbladders of both snakes
from all the provinces. For the first collections, they
relaxed the specimens in distilled water, then placed
them in physiological saline, and finally fixed them in
a cold 5% formalin solution. However, specimens collected
later were used for the descriptions. These were
placed directly into saline, then fixed with near boiling
water without coverslip pressure, and finally pipetted
into 5% formalin. Additional unmeasured specimens
were fixed under pressure for examination of specific
features. Whole mounts of worms were prepared by
staining specimens with either carmine or Van
Cleave's hematoxylin with additional Ehrlich's hematoxylin.
These were dehydrated, cleared with clove oil,
and mounted on slides with Canada balsam. Measurements
are given for the holotype, followed in parentheses
by the range of measurements of each feature
derived from specimens heat-fixed without pressure.
Measurements are given in micrometers unless otherwise
stated. Specimens were deposited in the United
States National Parasite Collection (USNPC), Belts-
Copyright © 2011, The Helminthological Society of Washington