Comparative Parasitology 68(2) 2001 - Peru State College

270 COMPARATIVE PARASITOLOGY, 68(2), JULY 2001
The green frog Rana clamitans Rafmesque,
1820, occurs from Newfoundland, where the
population was introduced (Conant and Collins,
1991), to western Ontario, Canada, in the northern
extent of its range and from North Carolina
to eastern Oklahoma, U.S.A. in the south (Vogt,
1981). Although reports of green frog parasites
are numerous, only 3 studies have been conducted
in Wisconsin, U.S.A. (Williams and Taft,
1980; Coggins and Sajdak, 1982; Bolek, 1998).
A total of 26 green frogs were collected by hand
between 13 August and 3 September 1999 from 2
temporary ponds at the University of Wisconsin-
Milwaukee Field Station, Ozaukee County, Wisconsin
(43°23'N; 88°2'W). Frogs were transported
to the laboratory and euthanized in MS-222 (ethyl
m-aminobenzoate sulfonic acid). Body surface,
mouth, eustachian tubes, celom, lungs, stomach,
small intestine, colon, urinary bladder, liver, kidneys,
and leg musculature in individual containers
were examined with a dissecting microscope for
the presence of helminth parasites. Nematodes
were preserved in 70% ethanol and mounted in
glycerin for identification. Larval and adult platyhelminths
were fixed in alcohol-formalin-acetic
acid, stained with acetic carmine, and mounted in
Canada balsam. Voucher specimens were deposited
at the H. W. Manter Helminth Collection, University
of Nebraska, Lincoln, Nebraska (Table 1).
Use of ecological terms follows the suggestions of
Bush et al. (1997).
All host individuals were infected with 1 or
more helminths (prevalence = 100%). The component
community of green frogs consisted of 11
helminth species: 7 trematodes, 2 cestodes, and 2
nematodes (Table 1). Overall mean abundance of
helminths was 65.5 ± 79.7 worms per frog (range
= 1—330). Haematoloechus varioplexus occurred
with highest mean abundance, mean intensity, and
prevalence of infection (Table 1). Nematodes occurred
in low numbers and in few hosts (Table 1).
Adult green frogs breed in a variety of permanent
bodies of water (May-July in Wisconsin) and
inhabit the periphery of these aquatic habitats
throughout the summer (Vogt, 1981). During this
time, adult frogs feed upon a variety of animals,
including several species of insects with aquatic
life histories (Jenssen and Klimstra, 1966). Whereas
green frogs are known to migrate prior to hibernation,
they are thought to seek out aquatic
habitats that are well oxygenated and do not freeze
entirely in winter (Lamoureux and Madison,
1999). The ponds sampled in the present study are
Copyright © 2011, The Helminthological Society of Washington
ephemeral. Even in years when some water remains
over winter, these ponds freeze solid. The
green frogs that we collected seem to have moved
into these ponds as a place to feed prior to hibernating
in other areas.
The species composition and numbers of helminths
in green frog infracommunities at this location
were similar to those reported previously
(Rankin, 1945; Bouchard, 1951; Najarian, 1955;
Campbell, 1968; Williams and Taft, 1980; Coggins
and Sajdak, 1982; Muzzall, 1991; McAlpine,
1997; Bolek, 1998; McAlpine and Burt, 1998).
The aquatic habitat and diet of green frogs correspond
with helminth communities consisting mostly
of platyhelminths with indirect life cycles and
relatively few direct life cycle nematodes. In the
present study, H. varioplexus occurred with the
highest values of prevalence, mean intensity, and
mean abundance. These values are also high compared
with those reported in previous studies.
Muzzall (1991) reported 57% of 120 green frogs
infected with H. parviplexus, synonymous with H.
varioplexus (Kennedy, 1981), with a mean intensity
of 29. Najarian (1955) reported 48% of 40
green frogs infected with H. parviplexus and 42%
prevalence for H. breviplexus but did not provide
values for intensity or abundance of infection. Bolek
(1998) reported a prevalence of 44% for H.
varioplexus from 75 green frogs with a mean intensity
of 5.3. Others have reported prevalence values
of 25% or less for Haematoloechus spp. from
R. clamitans (Rankin, 1945; Bouchard, 1951;
Campbell, 1968; Williams and Taft, 1980; Mc-
Alpine and Burt, 1998). Haematoloechus varioplexus
has been reported previously from wood
frogs (Rana sylvatica Le Conte, 1825) and spring
peepers (Pseudacris crucifer Wied, 1839) from the
same ponds sampled in the current study (Yoder
and Coggins, 1996). It is therefore likely that infected
intermediate hosts are present in these
ponds. Additionally, large numbers of immature H.
varioplexus were recovered from green frogs, indicating
that hosts are being infected while feeding
at these locations. Odonates serve as second intermediate
hosts for species of Haematoloechus.
Muzzall (1991) reported that the absence of fish
predators may have increased the number of adult
odonates emerging from Turkey Marsh, Michigan,
U.S.A., resulting in richer helminth communities
than those occurring in habitats where both frogs
and fish occur. The absence of fish from these
ephemeral ponds may have had a similar result in
terms of high values of parasitism by H. vario-