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Attempts to differentiate elaphostrongyline larvae (Nematoda : Protostrongylidae) using guinea pigs (Cavia porcellus) as alternate hosts
Get PDFFirst-and third-stage larvae of Parelaphostrongylus tenuis, P. andersoni
and Elaphostrongylus cervi could not be distinguished morphometrically. Third-stage
larvae of P. tenuis did develop into recognizable adults in
experimentally-infected guinea pigs, but P. andersoni and E. cervi did not. At
present, elaphostrongyline larvae found in the feces of cervids in eastern
North America are most likely to be either P. tenuis or P. andersoni-, this
study confirms that the experimental infection of guinea pigs will allow this
distinction to be made. Because E. cervi is currently believed to be restricted
to Newfoundland, its third-stage larvae are distinguished by geographic origin.
As many as 22 migrating P. tenuis larvae were recovered from outside the
central nervous system (CNS) of each of seven guinea pigs necropsied between
1 and 27 days post-infection (DPI); all resembled third-stage larvae digested
from snails and used for infections. From one to six developing P. tenuis
larvae were recovered from the CNS of each of fourteen infected guinea pigs.
These included third-stage larvae, longer than reported in published literature,
which were recovered as early as 9 DPI and as late as 20 DPI in the CNS.
Fourth-stage larvae were recovered between 18 and 47 DPI, and fifth-stage
larvae between 20 and 61 DPI; these stages were only found in the CNS. The
morphology of the buccal capsule and the tail distinguished the third-, fourth and
fifth- stage larvae. Descriptions and dimensions of third- and fourth-stage
P. tenuis larvae recovered from the CNS are provided for the first time.
Lesions found in the stomach wall, mesentery and liver of guinea pigs
infected with P. tenuis suggest that third-stage larvae migrate through the
abdominal cavity towards the CNS. Similar lesions found in guinea pigs infected with P. andersoni and E. cervi suggest that larvae of these species
follow a similar route. However, P. andersoni apparently failed to reach the
musculature of any of six experimentally-infected guinea pigs. Similarly, E.
cervi was not recovered from the CNS or musculature of any of six
experimentally-infected guinea pigs.
Administration of dexamethasone appears to have been ineffective in
suppressing the immune response of guinea pigs to infection with these
elaphostrongylines. The mean number of P. tenuis larvae recovered from the
CNS of guinea pigs given dexamethasone was not significantly different from
that recovered from guinea pigs given saline. Treatment with dexamethasone
allowed neither P. andersoni nor E. cervi larvae to establish in guinea pigs
Morphology and phylogeny of the Elaphostrongylinae : (Nematoda: Protostrongylidae)
Get PDFThe morphology of elaphostrongyline nematodes parasitizing North American
cervids was studied using light and scanning electron microscopy in order to improve
previous descriptions that were based exclusively on light microscopical studies.
Structures including the spicules, gubernaculum, bursa, cephalic region, sensory
structures, and female tails of Parelaphostrongylus tenuis, P. odocoilei, P. andersoni,
and Elaphostrongylus cervi rangiferi are described. The morphology of E. c. rangiferi
as described in this study is similar to previous light microscopical descriptions. The
spicules of all three Parelaphostrongylus spp. were alike but differed from those of E.
c. rangiferi by having a dorsal branch of the spicule shaft in the distal region that
extends to the tip. A membrane spans the area between the branch and the shaft.
The corpus of the gubernaculum of P. odocoilei is not split distally as has been
described by previous authors, but instead has a longitudinal groove in the distal
region. Ventral protuberances associated with the cloaca are present in
Parelaphostrongylus spp. but absent in E. c. rangiferi. Sensory papillae and pores
associated with the cloaca and the bursal rays are described. In dorsal view, the base
of the dorsal ray has a prominent edge of thickened cuticle in P. odocoilei and P.
andersoni, whereas in E. c. rangiferi and P. tenuis it is smooth. The female tails of
Parelaphostrongylus spp. have a papilla-like projection at their tips.
The phylogeny of the Elaphostrongylinae was reconstructed using cladistic
techniques. Morphological characters described in this study provide strong evidence for the monophyly of Parelaphostrongylus. The genus is made up of two clades, one
containing P. odocoilei and P. andersoni, the other being P. tenuis. The biogeography
of the Cervidae of North America in relation to the phylogeny of the
Elaphostrongylinae is discussed. The genus Parelaphostrongylus probably coevolved
with the genus Odocoileus in the Nearctic, while Elaphostrongylus spp. most likely had
a Palearctic origin
Over-winter survivorship of parelaphostrongylus tenuis first-stage larvae / by Sean Geritt Forrester
Get PDFEcology of terrestrial gastropods and their response to conifer release treatments in northwestern Ontario
Get PDFThe primary objective of this study was to document any changes in terrestrial
gastropod species richness and density associated with alternative methods of managing
competing vegetation on regenerating conifer plantations. Pre-treatment data were
collected in 1993 and post-treatment data in 1994, following application of four conifer
release treatments including, two chemical herbicides (Vision® and Release®), removal of
vegetation by mechanical means (Silvana Selective/Ford Versatile), and manual cutting
with brushsaws. Gastropod densities were estimated using cardboard sheets. A total of
47,595 gastropods was collected over the two years, comprising 21 species. No change
in gastropod richness or density was detected between the four conifer release areas and
the control in 1994, despite changes in vegetation cover following treatments. This was
attributed to rapid re-establishment of the herbaceous layer following treatments which
probably continued to provide favourable conditions for snails and slugs.
Species richness and density of gastropods in a 9-year-old regenerating conifer
plantation and an adjacent 70-year-old mixedwood forest were compared. Gastropod
density was higher on the regenerating plantation (15.5±1.3 m-2) than in the mature forest
(9.4±0.6 m-2) and species richness was also slightly greater (20 spp. vs. 18 spp.,
respectively). These differences were attributed to the more abundant near-ground
vegetation and the greater amount of deciduous litter characterizing the regenerating
plantation.
Near ground temperature was measured on the four conifer release areas and the control using thermocouples. Temperature was measured 2 cm above cardboard sheets,
directly beneath the sheets, and 2 cm deep in the humus layer. Results suggest that
temperatures were not affected by the release treatments. Temperatures above and
beneath the sheets were similar and greater than those in the humus layer throughout the
early part of the summer. In August, temperature above and beneath the sheets cooled
to below that in the humus layer. Gastropod collections were greatest when the
temperature beneath the cardboard sheets was approximately 15°C.
Possible limitations associated with the cardboard sheet sampling method were
investigated. Gastropod collections from sheets enclosed with a barrier were compared
to unenclosed sheets to determine the extent of horizontal movement. The mean density
recovered beneath enclosed sheets (2.1±0.2 m-2) was less than that from unenclosed sheets
(3.1db0.4 m-2) suggesting horizontal movement to the sheets does occur. However,
whether gastropods are actually attracted to the sheets remains unknown. Gastropod
collections from weathered sheets were contrasted with those from new sheets. Overall,
total mean densities of gastropods from weathered sheets (27.3±4.1 m-2) and new sheets
(16.2±2.6 m-2) did not differ, but four species were collected in greater numbers on the
weathered sheets suggesting differential use of cardboard sheets by particular species
Infrapopulation dynamics of Parelaphostrongylus tenuis in white-tailed deer
Get PDFWhite-tailed deer (Odocoileus virginianus), of known age, collected in
northeastern Minnesota (n=379) from November 1991 to May 1993 were
examined for Parelaphostrongylus tenuis. Prevalence and intensity estimates were
based on adult worms in the cranium and first-stage larvae in the feces of the
same individuals. Prevalence of worms in the cranium was higher (82%) than
prevalence of larvae in the feces (53%). The difference between these two
measures was largely (78%) due to unisexual, occult infections. The spinal column
does not seem to be an important site for adult P. tenuis since only one of 26
animals had a worm (immature) located there.
In fawns, the prevalence of larvae (35%) and adult worms (68%) was lower
than in all older age classes (63%, 89%, respectively). The mean number of adult
worms was lower in fawns (2.7) and yearlings (3.0) than in deer 7-15 yr (4.1).
Conversely, the mean number of larvae in feces was higher in fawns (102
larvae/g) than in adults 2-6 (36 1/g) and 7-15 yr (36 1/g).
More larvae were passed in spring (mean of 77 1/g) than in fall (11 1/g) or
winter (38 1/g). Mean fecundity was greater in fawns (52 larvae/g/female worm)
than in adults 2-6 yr (15 1/g/f) and 7-15 yr (12 1/g/f). The sex ratio of worms did
not change with increasing age of deer, nor did the ratio of worms in the sinuses
to subdural space. The number of larvae in feces was not correlated with the
number of female P. tenuis in the cranium, but was correlated with the ratio of A smaller sample of white-tailed deer (n = 34) from an area where density
reached 30 deer/km2 was compared with animals from the study area where
summer density was 3.7 deer/km2. The mean number of adult worms in deer of
all ages was similar in both areas (3.2 and 3.5, respectively), but animals in the
high density area passed more larvae (94 and 57 1/g, respectively).
Results suggest that P. tenuis is long-lived and that deer infected in their
first or second summer of life acquire few, if any, additional worms thereafter. A
threshold number of adult worms in each deer limits infrapopulation larval
production as deer density increases. Infrapopulation larval production, however,
is highest in young animals and in the spring. Suprapopulation larval production
will be affected by deer density, the proportion of young naive deer in a
population and the ability of deer to produce an effective immune response to the
parasite
Migration and development of Cystidicola spp. (Habronematoidea) in their definitive hosts and the population biology of C. cristivomeri White, 1941 in Salvelinus spp.
Get PDFThe development of Cystidicola cristivomeri in lake
trout, Salvelinus namaycush, and C, farionis in rainbow trout,
Salmo gairdneri, is described. The population biology of
C. cristivomeri was investigated in lake trout in three lakes
in northwestern Ontario and in arctic char, S. alpinus,
Gaviafaeces Lake, Northwest Territories.
Young lake trout fed selectively on large Mysis
relicta which were more frequently infected with C. cristivomeri
(up to 5.1%) than small mysids. Pontoiporeia affinis was not
a suitable intermediate host in nature and there was no
evidence that fish paratenic hosts were important in transmitting
this nematode to lake trout.
Third-stage larvae given to lake trout migrated
directly via the pneumatic duct to the swimbladder. In
experimentally infected fishes, at 4-10°C, C. cristivomeri were
mature after 67 (males) and 210 days (females); C. farionis were
mature after 112 (males) and 235 days (females). There was no
measurable mortality of C. cristivomeri after 600 days in
experimentally infected lake trout.
Field studies indicated that most C, cristivomeri
live at least 10 years and some probably live longer. The
development of female worms to sexual maturity was retarded
and they grew more slowly when large numbers of C, cristivomeri
were present in the swimbladder. Short female worms produced eggs at a slower rate than longer females. This density
dependent regulation of C, cristivomeri at the infrapopulation
level may result in long-term stability of
the nematode suprapopulation in a lake.
The number of ulcerative lesions on the inner
surface of the swimbladder of lake trout was directly
dependent upon the number of mature C. cristivomeri
present in a fish
Effects of alternative conifer release treatments on terrestrial gastropods of regenerating spruce plantation
Get PDFThis study examined changes in terrestrial gastropod densities and species
richness associated with alternative methods of managing competing vegetation on
regenerating spruce plantations. Data were collected monthly from June to September in
1995 and 1996, the second and third years following use of four conifer release
treatments (herbicides. Vision® and Release®; manual clearing, brushsaw and mechanical
clearing, Silvana Selective/Ford Versatile) on each of four replicate blocks. A total of
15,083 terrestrial gastropods, comprising 21 species, was collected from litter surface
sampling sites (beneath cardboard sheets) over the two years. In 1995, recorded
gastropod densities were low (4.2 ± 0.2m-2)(Mean ± S.E.) during an unusually dry
summer and were similar among all treated and control areas. With wetter conditions in
1996, these numbers increased on all areas (6.9 ± 0.3 m-2, but were significantly lower on
areas treated with herbicides (see document). This may
be attributable to variability in near ground temperature and relativity humidity. As well,
the decreased accumulation of broadleaf litter in these sites may have provided
inadequate habitat conditions during dry periods. Despite this difference in surface active
gastropods suggested by cardboard sheet collections, no difference in numbers was
apparent in a limited number of soil core samples taken from untreated and Vision®
treated sites (258 ± 145 and 377 ±221 m-2, respectively).
Overall gastropod densities were highest where soil moisture, pH and calcium
concentration were highest. Gastropod densities measured by surface sampling cardboard sheets were greater on a regenerating plantation than on an unharvested forest and on a
complete removal plot (CRV), where vegetation was removed annually using Vision®
(9.4 ± 0.5,6.7 ± 0.4 and 6.4 ± 0.5 m-2, respectively). These differences may be
attributable to the more abundant near ground vegetation and larger broadleaf component
of the litter layer in the regenerating plantation. Species richness was similar among these
sites, but several species were not collected on all CRV plots
Biology of Cystidicola farionis Fischer, 1798 (Nematoda : Cystidicolidae) in salmonid fishes
Get PDFMorphological studies, experimental cross-infections and host specificity data suggest that the species of swimbladder nematode which matures in Coregonus clupeaformis, from inland lakes is not distinct from Cystidicola farionis which matures in Coregonus artedii and other salmonids from Lakes Superior and Nipigon. Adult worms in Coregonus clupeaformis are morphologically indistinguishable from those in other hosts. However, eggs of worms in Coregonus clupeaformis have
predominantly lateral filaments, while those in other hosts have predominantly polar filaments. Larvae which accumulate but do not mature in the swimbladder of
Coregonus clupeaformis from Lake Nipigon, grew and developed toward maturity in hatchery-reared Coregonus clupeaformis of Lake Simcoe origin. One, mature, male worm was found 77 days after experimental infection. Only female worms containing unshelled eggs were found after 120 days. This suggests that the development of C. farionis may depend on host strain. Uncertainty remains as to whether variations in egg morphology are host-induced or due to genetic differences
of the worms involved.
Filaments on the eggs of C. farionis readily adhere to the setose areas on the
appendages of amphipod intermediate hosts. Presumably, this increases the
probability of the intermediate host ingesting eggs. Eggs stored in water or saline for periods of two weeks or more do not hatch in the gut of amphipods. Only eggs recently released from female worms hatch and develop.
Mature swimbladder nematodes were found in Coregonus clupeaformis from all
of seven inland lakes examined in northwestern Ontario. Coregonus artedii was present in three of these lakes but was not infected, perhaps due to the lack of amphipod intermediate hosts in its diet. Cystidicola farionis matures in Salvelinus namaycush from Pettit Lake, Ontario and has eggs resembling those from worms in
Coregonus clupeaformis from the same lake. Prosopium coulteri from Lake Superior are infected with C. farionis (new host record) but are not considered to be a
suitable host for the worm as no mature worms were found. Infections in
Coregonus clupeaformis from Pettit Lake and in Salmo gairdneri from Lake Superior
exhibited similar seasonal periodicity with largest worm numbers occurring in the
spring.
The cephalic structures of C. farionis and its close relative, C. stigmatura,
were studied using a scanning electron microscope and are compared with those of other cystidicolids
Biology and histopathology of Proteocephalus ambloplitis Liedy, 1887, infecting walleye (Stizostedion vitreum vitreum) and yellow perch (Perea flavescens) in Lake of the Woods, Ontario
Get PDFWalleye (Stizostedion vitreum vitreum ) and yellow
perch (Perea flavescens ) from Lake of the Woods were
examined for parenteral Proteocephalus ambloplitis from
May to November, 1982 and 1983. One hundred percent of the
age 1 and older walleye and 74% of the age 1 and older
yellow perch harboured plerocercoids. In corresponding age
classes, walleye were generally 10 times more heavily
infected than yellow perch. Mean intensity of live
plerocercoids increased with age of walleye until age class
5 then declined significantly in older fish. Intensity increased from a mean of 23 (in age class 0) to a maximum of
171 in age class 5 and was only 58 in the 7+ age class. Mean
intensity of plerocercoids increased continuously with the
age of yellow perch from 2 (age class 0) to a maximum of 20
in the 5+ age class.
All age classes of walleye (0 to 7+) became infected by
preying on yellow perch, particularly the young-of-the-year
(YOY). Small yellow perch became infected by eating copepods
but older perch obtained plerocercoids by cannibalism. The
transmission of plerocercoids to walleye and yellow perch
was greatest during late summer. Young-of-the-year walleye
and YOY yellow perch first harboured plerocercoids in early August.
The liver was the first organ of walleye and yellow
perch to be invaded by migrating plerocercoids. However, in walleye, the mesenteries ultimately contained the greatest
proportion of p1erocercoids in age 1 and older fish. The
liver remained a relatively Important site for plerocercoids
in all age classes of yellow perch. Relatively few
plerocercoids were found in the gonads of walleye or yellow
perch. Walleye fecundity was not correlated with
plerocercoid intensity.
Ninespine sticklebacks ( Fungitius pungitius ) and
logperch (Percina caprodes ) were found to harbour P.
ambloplitis p1erocercoids . These are new host records.
Migrating plerocercoids caused the greatest
pathological change in the liver of walleye and yellow
perch. Zones of compressed and necrotic hepatocytes were
evident adjacent to live, unencapsulated plierocercoids . The
mesenteries of walleye were often fibrosed in response to
large numbers of invading plerocercoids. The
gastro-intestinal tract, posterior gonads and associated mesenteries were often compacted with fibrous tissue.
Obstruction of the passage of gametes is possible.
Constriction of the oviduct may result from the fibrous
reaction. Also, encapsulated plerocercoids were found in the
lumen of the oviduct creating a physical barrier. The wall
of capsules encompassing plerocercoids in walleye was
relatively thin (maximum of 90 microns) while in yellow
perch, it was up to 290 microns thick
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