Experimental population dynamics of Rhabdias bufonis (Nematoda) in toads (Bufo bufo): density-dependence in the primary infection

Abstract

SUMMARYDensity-dependence in worm establishment, numbers, biomass and larval production were examined in primary infections of 0, 10, 40, 80 and 160 larvae of the lung nematode, Rhabdias bufonis in the common toad, Bufo bufo. The infection procedure established 4 non-overlapping levels of infection which persisted until 6 weeks post-infection (p.i.). after which there was an overall decline up to 12 weeks p.i. Worm numbers had no direct effect on adult worm survival but temporal changes in worm weight were density-dependent. Adult worm establishment in the lungs declined significantly as the numbers of worms in the lungs increased. At the lowest exposure dose, 86 % of the larvae administered reached maturity in the lungs while at the highest, only 37 % did so. Also, the numbers of immature larvae outside the lungs increased as adult worm numbers increased. Both features provide evidence for a threshold limit to the numbers of worms maturing in the lungs. Worm numbers also affected larval output per host and per capita fecundity. A significant positive relationship between per capita fecundity and per capita worm weight suggested that density-dependence acted primarily to constrain the growth of individual worms. Finally, the constraints imposed on worm growth and fecundity were apparently relaxed when worm density decreased, providing evidence for density-dependent flexibility in per capita fecundity. Densitydependence in worm establishment and per capita fecundity are mechanisms which may potentially regulate this hostparasite interaction in the field. Both mechanisms may be functionally related to physical space limitations in the lungs, within which worms must compete for finite nutrients.

Disease and the Extended Phenotype: Parasites Control Host Performance and Survival through Induced Changes in Body Plan

“…Correspondingly, while both groups made similar numbers of attempts, malformed frogs were less successful at capturing prey and ultimately consumed 28% and 55% fewer fruit flies and crickets, respectively. These effects were as severe or greater than those reported in similar studies undertaken with other amphibian parasites [41], [43], [61]. Because of the distinctive nature of this parasite-induced change in phenotype, for which the causal relationship with Ribeiroia infection has been well established [26]–[29], we avoid problems that can arise when natural variation in subtler phenotypes influences subsequent patterns of infection [23].…”

Exposure of leopard frogs to a pesticide mixture affects life history characteristics of the lungworm Rhabdias ranae

“…Given that fecundity is directly proportional to size in Rhabdias sp. (Goater 1992) and in other parasitic nematodes (Read and Skorping 1995;Morand 1996;Marcogliese 1997), those worms that migrated faster probably did not suffer any loss of fecundity. This is the first study we are aware of that demonstrates alterations in basic parasite life history characteristics as a result of host exposure to contaminants.…”

The evolution of tissue migration by parasitic nematode larvae

“…As with many invertebrates (Blueweiss et al 1979;Sibly & Calow, 1986), there is abundant evidence that bigger nematodes are more fecund, both within species (e.g. Michael & Bundy, 1989;Szalai & Dick, 1989;Sinniah & Subramanian, 1991;Goater, 1992) and across species (Skorping et al 1991). Furthermore, larger bodied nematode species probably have longer reproductive life-spans (Skorping et al 1991).…”