scholarly journals Density-dependent regulation of fecundity in Syngamus trachea infrapopulations in semi-naturally occurring ring-necked pheasants (Phasianus colchicus) and wild Carrion Crows (Corvus corone)

Parasitology ◽  
2016 ◽  
Vol 143 (6) ◽  
pp. 716-722 ◽  
Author(s):  
O. J. GETHINGS ◽  
R. B. SAGE ◽  
S. R. LEATHER
Keyword(s):  
Worm Burden ◽  
Wild Population ◽  
Phasianus Colchicus ◽  
Density Dependent ◽  
Naturally Occurring ◽  
Corvus Corone ◽  
Age Dependent ◽  
Communal Areas ◽  
Dependent Processes ◽  
Syngamus Trachea

SUMMARYPrevious work has highlighted increased opportunities for the transmission of Syngamus trachea within pheasant release pens, due in part to high levels of environmental contamination around communal areas. Despite this, the distribution of adult worms within their definitive hosts is not significantly different from predicted distributions under Taylor's power law. Therefore, density-dependent processes are probably acting to regulate S. trachea population dynamics. Patterns of nematode fecundity were investigated in a semi-naturally occurring population of ring-necked pheasants (Phasianus colchicus) and a wild population of carrion crows (Corvus carone). Worm length was a reliable indicator of nematode fecundity, and a negative association between mean worm length and mean worm burden was identified within both the species. The stunting of worms at greater parasite densities was present in both immunologically naïve and previously exposed pheasants, so is unlikely to be a function of age-dependent acquired immunity. Interestingly, the effect of parasite crowding in the crow population explained more of the variation in mean worm length, apparently driven by a greater mean worm burden when compared with pheasants. The findings of the present study suggest that fecundity is a function of parasite density, i.e. parasite-mediated competition and not host-mediated heterogeneities in immunocompetence.

Density-dependent regulation of the growth of the hookworms Necator americanus and Ancylostoma ceylanicum

Parasitology ◽  
1994 ◽  
Vol 109 (1) ◽  
pp. 119-128 ◽  
Author(s):  
S. M. B. Norozian-Amiri ◽  
J. M. Behnke
Keyword(s):  
Worm Burden ◽  
Infection Intensity ◽  
Dry Weight ◽  
Ancylostoma Ceylanicum ◽  
Density Dependent ◽  
Necator Americanus ◽  
Infective Larvae ◽  
Length Width ◽  
Negative Relationships ◽  
Dependent Processes

SUMMARYLaboratory bred DSN hamsters were exposed to varying doses of infective larvae of Ancylostoma ceylanicum (orally) or Necator americanus (percutaneously) and were autopsied at times which corresponded to a period immediately before cessation of growth of worms or soon afterwards. A total of 829 (404 male and 425 female) A. ceylanicum and 1582 (781 male and 801 female) N. americanus were measured. At worm burdens of fewer than 100, the length of A. ceylanicum appeared to increase with infection intensity and no evidence was found that growth was retarded under crowded conditions. In an experiment comparing directly low (mean worm burden = 22) and heavy infections (mean worm burden = 180) significant negative associations between both weight and width, and worm burden were detected, but length again increased with worm burden. In contrast, 5 experiments with N. americanus indicated negative relationships between measures of worm size (length, width, wet and dry weight) and worm burden. It was concluded that N. americanus is subject to regulation by density-dependent processes within the host while A. ceylanicum is not sensitive to the same degree.

The regulation ofOstertagia ostertagipopulations in calves: density-dependent control of fecundity

Parasitology ◽  
1987 ◽  
Vol 95 (2) ◽  
pp. 373-388 ◽  
Author(s):  
G. Smith ◽  
B. T. Grenfell ◽  
R. M. Anderson
Keyword(s):  
Worm Burden ◽  
Egg Production ◽  
Inverse Function ◽  
Single Infection ◽  
Intensity Of Infection ◽  
Density Dependent ◽  
Helminth Infections ◽  
Model Predictions ◽  
Initial Peak ◽  
Infection Experiments

SUMMARYThe decline in faecal egg counts, characteristic of calves which have been experimentally infected withOstertagia ostertagi, is analysed using a mathematical model in which parasite fecundity is assumed to be an inverse function of both the duration and intensity of infection. The model incorporates a description of the frequency distribution of mature parasites between hosts (which is less over-dispersed than is usual for many other helminth infections). The model provides a good overall description of the decline in faecal egg production observed during trickle and single infection experiments. The main discrepancy between a comparison of the model predictions and the results of the most detailed available series of trickle infection experiments occurs at the initial peak of egg production. The magnitude of this difference appears to be related to the worm burden at the peak of egg production. The possible mechanisms underlying density-dependent regulation of the fecundity ofO. ostertagiaare discussed.

Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population

2018 ◽  
Vol 88 (1) ◽  
pp. 164-177 ◽  
Author(s):  
Hugo Cayuela ◽  
Benedikt R. Schmidt ◽  
Avril Weinbach ◽  
Aurélien Besnard ◽  
Pierre Joly
Keyword(s):  
Amphibian Population ◽  
Density Dependent ◽  
Dependent Processes

The effect of an indirect anthelmintic treatment on parasites and breeding success of free-living pheasantsPhasianus colchicus

2006 ◽  
Vol 80 (4) ◽  
pp. 409-415 ◽  
Author(s):  
R.A.H. Draycott ◽  
M.I.A. Woodburn ◽  
D.E. Ling ◽  
R.B. Sage
Keyword(s):  
Breeding Success ◽  
Large Scale ◽  
Parasite Burden ◽  
Anthelmintic Treatment ◽  
Phasianus Colchicus ◽  
Free Living ◽  
Parasitic Worm ◽  
Large Scale Field ◽  
Syngamus Trachea

AbstractIn Great Britain free-living common pheasantsPhasianus colchicusare often managed at high densities owing to their popularity as a quarry species. They are prone to infection by a range of parasite species includingHeterakis gallinarum,Capillariaspp. andSyngamus trachea. In 1995 the efficacy of an indirect anthelmintic technique for controlling parasitic worm burdens of pheasants was determined in a pilot study on a shooting estate in the south of England. Between 2000 and 2003 a large-scale field experiment was conducted on nine estates in eastern England to determine the effect of the technique on parasite burden and pheasant breeding success. In the absence of anthelmintic treatment worm burdens increased rapidly through March and April, whereas birds given anthelmintic-treated grain had lower worm burdens during the same period. The breeding success of pheasants was significantly higher on plots provided with anthelmintic treatment, although no long-term increases in population densities were observed. The burdens of the most common parasiteH. gallinarumwere significantly lower in pheasants from treatment plots six weeks after the anthelmintic treatment had ceased, but spring treatment did not influence parasite burden in the following winter.

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