Numerical and functional responses of intestinal helminths in three rajid skates: evidence for competition between parasites?

Parasitology ◽  
2012 ◽  
Vol 139 (13) ◽  
pp. 1784-1793 ◽  
Author(s):  
HASEEB S. RANDHAWA

SUMMARYHost-parasite interactions generally involve communities of parasites. Within these communities, species will co-exist and/or interact with one another in a manner either benefiting the species involved or to the detriment of one or more of the species. At the level of helminth infracommunities, evidence for intra- and inter-specific competition includes numerical responses, i.e. those regulating helminth intensity of infection, and functional responses, i.e. where the presence of competitors modifies the realised niche of infrapopulations. The objectives of this study are to assess the numerical and functional responses of helminths in infracommunities from 3 rajid skates using general linear models. Despite a lack of numerical responses, functional responses to intra- and inter-specific interactions were observed. A positive correlation between the number of individuals in an infrapopulation and its niche breadth (functional response) was observed for the tapewormsPseudanthobothriumspp. andEcheneibothriumspp., in all their respective hosts, and for the nematodePseudanisakissp. in the little skate. Evidence for inter-specific competition includes niche shifts inPseudanthobothrium purtoni(exlittle skate) andPseudanisakissp. (exthorny skate) in the presence ofPseudanisakissp. and the tapewormGrillotiasp., respectively. These results are consistent with other studies in providing evidence for competition between helminths of skates.

Weed Science ◽  
2019 ◽  
Vol 67 (4) ◽  
pp. 397-411 ◽  
Author(s):  
Lua Lopez ◽  
Emily S. Bellis ◽  
Eric Wafula ◽  
Sarah J. Hearne ◽  
Loren Honaas ◽  
...  

AbstractHost-specific interactions can maintain genetic and phenotypic diversity in parasites that attack multiple host species. Host diversity, in turn, may promote parasite diversity by selection for genetic divergence or plastic responses to host type. The parasitic weed purple witchweed [Striga hermonthica (Delile) Benth.] causes devastating crop losses in sub-Saharan Africa and is capable of infesting a wide range of grass hosts. Despite some evidence for host adaptation and host-by-Striga genotype interactions, little is known about intraspecific Striga genomic diversity. Here we present a study of transcriptomic diversity in populations of S. hermonthica growing on different hosts (maize [Zea mays L.] vs. grain sorghum [Sorghum bicolor (L.) Moench]). We examined gene expression variation and differences in allelic frequency in expressed genes of aboveground tissues from populations in western Nigeria parasitizing each host. Despite low levels of host-based genome-wide differentiation, we identified a set of parasite transcripts specifically associated with each host. Parasite genes in several different functional categories implicated as important in host–parasite interactions differed in expression level and allele on different hosts, including genes involved in nutrient transport, defense and pathogenesis, and plant hormone response. Overall, we provide a set of candidate transcripts that demonstrate host-specific interactions in vegetative tissues of the emerged parasite S. hermonthica. Our study shows how signals of host-specific processes can be detected aboveground, expanding the focus of host–parasite interactions beyond the haustorial connection.


1989 ◽  
Vol 121 (9) ◽  
pp. 821-822
Author(s):  
Marek Tomalak ◽  
Harold E. Welch ◽  
Terry D. Galloway

Nematode parasites of bark beetles are taxonomically diverse, and may, in some cases, cause serious pathological and behavioural changes in their hosts (Kaya 1984). Their potential as biological control agents has long been recognized, but to date there is a shortage of elementary information on host-parasite interactions. Though the effects of superparasitism and subsequent crowding on the parasite have been studied for some mermithids (Petersen 1972) and steinernematids (Sandner and Stanuszek 1971), no such observations have been reported for bark beetle parasites. During a survey of nematode parasites of bark beetles in Manitoba, we encountered two examples where nematodes were detrimentally affected at the higher infection rates observed. It was our objective, therefore, to examine the relationship between intensity of infection, and impact on growth and reproduction of the parasites.


Parasitology ◽  
2011 ◽  
Vol 138 (8) ◽  
pp. 1022-1028 ◽  
Author(s):  
HIDEYUKI DOI ◽  
NATALIA I. YURLOVA

SUMMARYIt is suspected that host-parasite interactions are influenced by climatic oscillations such as the North Atlantic Oscillation (NAO). However, the effects of climatic oscillations on host-parasite interactions have never been investigated. A long-term (1982–1999) dataset of the host snail Lymnaea stagnalis and trematode metacercariae infection has been collected for Lake Chany in Western Siberia. Using this dataset, we estimated the impact of the NAO on the population dynamics of hosts and parasites as well as their interactions. The results of general linear models showed that the abundance of dominant parasite species and the total parasite abundance significantly increased with NAO, with the exception of Moliniella anceps. Other climatic and biological factors were relatively weak to explain the abundance. There was no significant relationship between NAO and the population density of host snails. The prevalence of infection was related to the total abundance of parasites, but not to the NAO. Thus, the responses to the NAO differed between the host and parasites, indicating mismatching in host-parasite interactions. Therefore, climatic oscillations, such as the NAO, influence common parasitism.


Parasitology ◽  
2020 ◽  
Vol 147 (12) ◽  
pp. 1375-1380 ◽  
Author(s):  
Joshua I. Brian ◽  
David C. Aldridge

AbstractParasitic castration of bivalves by trematodes is common, and may significantly reduce the reproductive capacity of ecologically important species. Understanding the intensity of infection is desirable, as it can indicate the time that has passed since infection, and influence the host's physiological and reproductive response. In addition, it is useful to know the developmental stage of the trematode, to understand trematode population trends and reproductive success. However, most existing methods (e.g. visually estimating the degree of infection) to assess intensity are approximate only and not reproducible. Here, we present a method to accurately quantify the percentage of bivalve gonad filled with digenean trematode tissue, based on small squashes of gonad tissue rapidly photographed under light microscopy. A maximum of 15 photographs is required to determine the percentage of the whole gonad occupied by trematodes with a minimum of 90% confidence, with smaller mussels requiring fewer. In addition, the stage of trematode infection can be assessed because full sporocysts, spent sporocysts and free cercariae are clearly distinguishable. Although variation exists in the distribution of trematodes in gonad tissue, and thus in the estimate of percentage of the gonad filled with trematodes, this method represents a marked improvement on current coarse assessments of infection which typically focus on binary presence/absence measures. This technique can be used to facilitate a more sophisticated understanding of host–parasite interactions in bivalves, and can inform the conservation and reproductive biology of environmentally crucial species.


2011 ◽  
Vol 41 (9) ◽  
pp. 925-933 ◽  
Author(s):  
James A. Cotton ◽  
Jennifer K. Beatty ◽  
Andre G. Buret

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Lenka Ulrychová ◽  
Pavel Ostašov ◽  
Marta Chanová ◽  
Michael Mareš ◽  
Martin Horn ◽  
...  

Abstract Background The blood flukes of genus Schistosoma are the causative agent of schistosomiasis, a parasitic disease that infects more than 200 million people worldwide. Proteases of schistosomes are involved in critical steps of host–parasite interactions and are promising therapeutic targets. We recently identified and characterized a group of S1 family Schistosoma mansoni serine proteases, including SmSP1 to SmSP5. Expression levels of some SmSPs in S. mansoni are low, and by standard genome sequencing technologies they are marginally detectable at the method threshold levels. Here, we report their spatial gene expression patterns in adult S. mansoni by the high-sensitivity localization assay. Methodology Highly sensitive fluorescence in situ RNA hybridization (FISH) was modified and used for the localization of mRNAs encoding individual SmSP proteases (including low-expressed SmSPs) in tissues of adult worms. High sensitivity was obtained due to specifically prepared tissue and probes in combination with the employment of a signal amplification approach. The assay method was validated by detecting the expression patterns of a set of relevant reference genes including SmCB1, SmPOP, SmTSP-2, and Sm29 with localization formerly determined by other techniques. Results FISH analysis revealed interesting expression patterns of SmSPs distributed in multiple tissues of S. mansoni adults. The expression patterns of individual SmSPs were distinct but in part overlapping and were consistent with existing transcriptome sequencing data. The exception were genes with significantly low expression, which were also localized in tissues where they had not previously been detected by RNA sequencing methods. In general, SmSPs were found in various tissues including reproductive organs, parenchymal cells, esophagus, and the tegumental surface. Conclusions The FISH-based assay provided spatial information about the expression of five SmSPs in adult S. mansoni females and males. This highly sensitive method allowed visualization of low-abundantly expressed genes that are below the detection limits of standard in situ hybridization or by RNA sequencing. Thus, this technical approach turned out to be suitable for sensitive localization studies and may also be applicable for other trematodes. The results suggest that SmSPs may play roles in diverse processes of the parasite. Certain SmSPs expressed at the surface may be involved in host–parasite interactions. Graphic abstract


2021 ◽  
Vol 10 (2) ◽  
pp. 205
Author(s):  
Lúcio Lara Santos ◽  
Júlio Santos ◽  
Maria João Gouveia ◽  
Carina Bernardo ◽  
Carlos Lopes ◽  
...  

Schistosomiasis is the most important helminthiasis worldwide in terms of morbidity and mortality. Most of the infections occurs in Africa, which about two thirds are caused by Schistosoma haematobium. The infection with S. haematobium is considered carcinogenic leading to squamous cell carcinoma (SCC) and urothelial carcinoma of the urinary bladder. Additionally, it is responsible for female genital schistosomiasis leading to infertility and higher risk of human immunodeficiency virus (HIV) transmission. Remarkably, a recent outbreak in Corsica (France) drew attention to its potential re-mergence in Southern Europe. Thus far, little is known related to host-parasite interactions that trigger carcinogenesis. However, recent studies have opened new avenues to understand mechanisms on how the parasite infection can lead cancer and other associated pathologies. Here, we present a historical perspective of schistosomiasis, and review the infection-associated pathologies and studies on host–parasite interactions that unveil tentative mechanisms underlying schistosomiasis-associated carcinogenesis.


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