Papers by Michael Sukhdeo
The behavioural ecology of parasites
Parasitology
This book is dedicated to my Ph.D. advisor, Neil Croll (1941–1981), whose seminal text “The Behav... more This book is dedicated to my Ph.D. advisor, Neil Croll (1941–1981), whose seminal text “The Behaviour of Nematodes” launched the field in 1970. The current effort is a thick, heavy tome when compared to Croll's slim and elegant little book, directly reflecting the explosion of interest in the topic, due in no small part to a single nematode Caenorhabiditis elegans. However, C. elegans is not the star of this book. The present effort is meant to be broad in its taxonomic scope, attempting to consolidate disparate nematode behaviours into a comprehensive up-to-date volume. Indeed, this is a formidable task in a world in which 4 out of every 5 metazoans is a nematode, and the end result is a bit uneven. To cover the taxonomic breadth, several chapters focused on simply describing proximate behaviours. Thus, Chapter 1 – Ecological and behavioural adaptations; Chapter 3 – Orientation; Chapter 4 – Feeding; Chapter 7 – Osmoregulation; and Chapter 8 – Physiological and biochemical basis...
The Journal of parasitology, 2017
This study surveyed gregarine parasites that infect the amphipod, Gammarus fasciatus , to investi... more This study surveyed gregarine parasites that infect the amphipod, Gammarus fasciatus , to investigate temporal dynamics in infracommunity structure. We sampled a population of hosts for 2 yr from the north branch of the Raritan River in New Jersey. These hosts were infected with 2 direct life cycle gregarine parasites, Rotundula gammari and Heliospora longissima. Infections were separated temporally, with the prevalence of R. gammari peaking within the amphipod population in the fall (prevalence = 78% year 1 and 97% year 2) and H. longissima peaking in early spring (prevalence = 41% year 1 and 52% year 2). Increases in host population density did not significantly correlate with the abundance of these 2 parasites. However, H. longissima abundance was positively correlated with host body weight while R. gammari showed no significant relationship. The mean body mass of amphipods infected with H. longissima was 20.7 ± 1. 2 mg, and with R. gammari 8.1 ± 0.2 mg, which suggests a sized-ba...
International Journal For Parasitology, May 31, 1996
Habitat selection may be the basis of some of the most exciting questions in behavioural ecology ... more Habitat selection may be the basis of some of the most exciting questions in behavioural ecology today, but parasites are being excluded from this debate. Parasites are not aberrant; they form a large proportion of the diversity of life on earth, and one estimate suggests that parasitism is more common than all other feeding strategies combined. We still do not understand the adaptive value of habitat selection behaviours in these organisms, even though the literature is full of examples of parasites migrating and navigating through hosts to their specific habitats. Parasites must make the same decisions that every animal has to make regarding food acquisition, shelter and reproduction. However, we cannot even make reasonable guesses on the habitat selection strategies and critical resources that influence their decision-making. The purpose of this review is to provide examples of experiments and methods of incorporating critical resources into the ecological analyses of habitat selection by gastrointestinal parasites. Information on parasite resources is simply not available for most parasites, and these ideas might stimulate and guide future research. In addition, parasites are ideal models to test theoretical assumptions of habitat selection. Experimental manipulations of parasites are ideal models to test theoretical assumptions of habitat selection. Experimental manipulations of parasite populations are simple, and habitats of endoparasites can be precisely altered by surgical methods. Few tests of habitat selection theory have been attempted in free-living environments because of the difficulty of assessing the correlations between environmental variations and organismal success in real-world situations, but this is not a problem with parasites because their habitats are replicated exactly in each host.
International Journal For Parasitology, May 1, 2008
Changes to host behaviour as a consequence of infection are common in many parasite-host associat... more Changes to host behaviour as a consequence of infection are common in many parasite-host associations, but their effects on the functional role hosts play within ecosystems are rarely quantified. This study reports that helminth parasites significantly decrease consumption of detritus by their isopod hosts in laboratory experiments. Natural host and parasite densities across eight contiguous seasons were used to estimate effects on the amount of stream detritus-energy processed. Extrapolations using mass-specific processing rates from laboratory results to field patterns suggest that the effects of the parasites occur year round but the greatest impact on the amount of detritus processed by isopods occurs in the autumn when the bulk of leaf detritus enters the stream, and when parasite prevalence in the isopod population is high. Parasites have a lesser impact on the amount of detritus processed in spring and summer when isopods are most abundant, when parasite prevalence is not high, and when fish predation on isopods is high. These results support the idea that parasites can affect the availability of resources critical to other species by altering behaviours related to the functional role hosts play in ecosystems, and suggest that seasonality may be an important factor to consider in the dynamics of these parasite-host interactions.
The Journal of Parasitology, 1995
Grooming behavior may play a part in the transmission of the gastrointestinal nematode, Heligomos... more Grooming behavior may play a part in the transmission of the gastrointestinal nematode, Heligomosomoides polygyrus in the mouse host. After infective larvae are placed on individually housed mice, significantly higher numbers of adult worms were recovered from the small intestine of mice that were allowed to self-groom when compared to infection levels in mice that had been fitted with Elizabethan collars to prevent self-grooming. Larvae placed on a single mouse housed with 3 other untreated mice resulted in all mice in the group becoming infected, suggesting that allogrooming may also be important in parasite transmission. A significantly higher percentage of larvae nictate on rough surfaces such as damp peat moss substrate when compared to smooth surfaces such as 0.5% agarose. Mice exposed to larvae placed on peat moss substrate have significantly higher infection levels when compared to mice exposed to larvae on a 0.5% agarose substratum, suggesting that natural transmission of infective L3 larvae in mice may be dependent on a substratum type that allows nictation behavior. A significantly higher percentage of worms were attracted to mouse urine and mouse and rat epidermal lipids when compared to deionized water controls in an in vitro preference assay, suggesting an attraction to host-specific signals. These results support the hypothesis that transmission of this parasite is an active process involving movement of the infective larvae of H.polygyrus into the host's active space where they are ingested during grooming behavior.
Http Dx Doi Org 10 1645 Ge 2254 1, Jun 11, 2010
This review examines the historical origins of food web theory and explores the reasons why paras... more This review examines the historical origins of food web theory and explores the reasons why parasites have traditionally been left out of food web studies. Current paradigms may still be an impediment because, despite several attempts, it remains virtually impossible to retrofit parasites into food web theory in any satisfactory manner. It seems clear that parasitologists must return to first principles to solve how best to incorporate parasites into ecological food webs, and a first step in changing paradigms will be to include parasites in the classic ecological patterns that inform food web theory. The limitations of current food web models are discussed with respect to their logistic exclusion of parasites, and the traditional matrix approach in food web studies is critically examined. The well-known energetic perspective on ecosystem organization is presented as a viable alternative to the matrix approach because it provides an intellectually powerful theoretical paradigm for generating testable hypotheses on true food web structure. This review proposes that to make significant contributions to the food web debate, parasitologists must work from the standpoint of natural history to elucidate patterns of biomass, species abundance, and interaction strengths in real food webs, and these will provide the basis for more realistic models that incorporate parasite dynamics into the overall functional dynamics of the whole web. A general conclusion is that only by quantifying the effects of parasites in terms of energy flows (or biomass) will we be able to correctly place parasites into food webs.
Experimental Parasitology, May 31, 1992
Hymenolepis diminuta propels itself with unidirectional peristaltic-like waveforms. When intact a... more Hymenolepis diminuta propels itself with unidirectional peristaltic-like waveforms. When intact adult H. diminuta are placed in a thermal gradient, with the anterior proglottids hot relative to the posterior proglottids, the worms migrate up the gradient toward the hot side. When the anterior is cold, relative to the posterior, the worms moved slightly or little. These behaviors in a thermal gradient represent true thermokinetic responses for an organism with undirectional locomotion. Removal of the scolex, containing the worm's cerebral ganglia, did not significantly alter these thermal responses. These data suggest that the peripheral nervous system is capable of integrating sensory input over the length of the strobila and coordinating locomotory behavior, in the absence of the central nervous system.
The way that parasites fit into food webs remains unclear. We argue that coherent energetic patte... more The way that parasites fit into food webs remains unclear. We argue that coherent energetic patterns (biomass pyramids) occur in food webs that include parasites. These patterns typically evolve in stable associations when considered from the perspective of the parasite, and empirical evidence is provided of biomass patterns in a natural fresh water food web.
J Parasitol, 2001
... I believe we met at an American Society of Parasitologists meeting in Philadelphia; I was pla... more ... I believe we met at an American Society of Parasitologists meeting in Philadelphia; I was playing La Bamba on the guitar, and Dave was doing a ... was able to indulge in his passion for fish and science, but he never forgot his training from the Esch lab, and the Big Lush himself. ...
The Journal of Parasitology, May 1, 2001
Journal of Parasitology, 2015
Can J Zool, 1980
Isolates of Trichinella from Alaska, Canada, and Kenya were compared during the intestinal and mu... more Isolates of Trichinella from Alaska, Canada, and Kenya were compared during the intestinal and muscle phases of infection in the A/J mouse. It was found that, whereas the adults of the three isolates occupied similar sites along the intestine, the durations of their sojourns in the intestine differed from each other. Histological examination of the small intestine during this period revealed that the inflammatory response of the A/J mouse to infection by the three isolates was similar in times of onset. Histological examination of the diaphragm muscle 30 day s after infection revealed that the most severe inflammatory response was found around cysts of the Canadian isolate whereas the inflammation surrounding the cysts of the other isolates was mild.These results suggest that the differences in infectivity determined from previous studies on these isolates are not related to the host inflammatory response to either intestinal or muscle phase. It is postulated that isolate infectivity is a function of the duration of the sojourn by the adult worms in the small intestine or of the fecundity of the adult worms.
Parasitology
SUMMARYThe effects of the direction of gut flow, of injections of glucose and saline into differe... more SUMMARYThe effects of the direction of gut flow, of injections of glucose and saline into different regions of the small intestine and of surgical re-routing or ligature of gastric, biliary and pancreatic secretions into the small intestine have been correlated with changes in the migratory response of the rat tapeworm Hymenolepis diminuta. Reversing the normal anterior to distal flow of luminal contents in the small intestine did not affect worm migration following feeding. Injections of a glucose-saline solution into the duodenum did not initiate a migratory response; similar injections into the mid- and posterior regions of the small intestine resulted in migrational responses similar to those following intragastric glucose feeding. Re-routing gastric secretions to the distal duodenum inhibited anterior migration of the worms beyond the new point of entry of gastric juices. Results following re-routing and ligation of the biliary and pancreatic secretions suggest that there is a potent cue to anteriad migration in the pancreatic secretions. Biliary secretions also appear to contain an additional migratory cue to worm migration. In order of importance the factors stimulating/inhibiting worm migration are pancreatic > gastric > biliary…
Background/Question/Methods The establishment and persistence of complex life cycle parasites are... more Background/Question/Methods The establishment and persistence of complex life cycle parasites are generally thought to be regulated by free-living host diversity, and the stability of ecological interactions. In this study, we test the prediction that stable host communities are a requirement for complex multi-host parasite life cycles to establish. Using salt marsh sites representing a gradient in host species diversity, and time since major ecological restoration, we document the colonization of naïve killifish, Fundulus heteroclitus, by parasites with complex or direct (one host) life cycles. Results/Conclusions We demonstrate that the diversity of the parasite community, and the rate at which species accumulated, were similar for the unrestored, and the 10- and 20- year restored marsh sites whereas, the parasite community in the newly restored marsh (0 year) supported only directly-transmitted parasite species. To explain the paradox of a low diversity, highly invaded salt marsh...
The Journal of parasitology, 1997
The behavioural ecology of parasites, 2002
This chapter reviews the host-seeking strategies of entomopathogenic nematodes at the infective j... more This chapter reviews the host-seeking strategies of entomopathogenic nematodes at the infective juvenile stage. Topics include conceptual models of foraging strategies; associations between nematodes and insect hosts; biology, foraging behaviour, host habitat selection, host-seeking response to host volatiles, and host selection by entomopathogenic nematodes; and evolution of foraging strategy.
The behavioural ecology of parasites, 2002
PLoS ONE, 2011
Background: Parasites significantly alter topological metrics describing food web structure, yet ... more Background: Parasites significantly alter topological metrics describing food web structure, yet few studies have explored the relationship between food web topology and parasite diversity. Methods/Principal Findings: This study uses quantitative metrics describing network structure to investigate the relationship between the topology of the host food web and parasite diversity. Food webs were constructed for four restored brackish marshes that vary in species diversity, time post restoration and levels of parasitism. Our results show that the topology of the food web in each brackish marsh is highly nested, with clusters of generalists forming a distinct modular structure. The most consistent predictors of parasite diversity within a host were: trophic generality, and eigenvector centrality. These metrics indicate that parasites preferentially colonise host species that are highly connected, and within modules of tightly interacting species in the food web network. Conclusions/Significance: These results suggest that highly connected free-living species within the food web may represent stable trophic relationships that allow for the persistence of complex parasite life cycles. Our data demonstrate that the structure of host food webs can have a significant effect on the establishment of parasites, and on the potential for evolution of complex parasite life cycles.
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Papers by Michael Sukhdeo