How to become a parasite without sex chromosomes: a hypothesis for the evolution of Strongyloides spp. and related nematodes

Parasitology ◽  
2014 ◽  
Vol 141 (10) ◽  
pp. 1244-1254 ◽  
Author(s):  
ADRIAN STREIT
Keyword(s):  
Reproductive Strategies ◽  
Life History Traits ◽  
Parasitic Nematode ◽  
Environmental Cues ◽  
Chromatin Diminution ◽  
Free Living ◽  
Parasitic Lifestyle ◽  
Parasitic Worms ◽  
Dauer Larvae ◽  
Parasitic Generation

SUMMARYParasitic lifestyles evolved many times independently. Just within the phylum Nematoda animal parasitism must have arisen at least four times. Switching to a parasitic lifestyle is expected to lead to changes in various life history traits including reproductive strategies. Parasitic nematode worms of the genus Strongyloides represent an interesting example to study these processes because they are still capable of forming facultative free-living generations in between parasitic ones. The parasitic generation consists of females only, which reproduce parthenogenetically. The sex in the progeny of the parasitic worms is determined by environmental cues, which control a, presumably ancestral, XX/XO chromosomal sex determining system. In some species the X chromosome is fused with an autosome and one copy of the X-derived sequences is removed by sex-specific chromatin diminution in males. Here I propose a hypothesis for how today's Strongyloides sp. might have evolved from a sexual free-living ancestor through dauer larvae forming free-living and facultative parasitic intermediate stages.

scholarly journals Independent origins of parasitism in Animalia

2016 ◽  
Vol 12 (7) ◽  
pp. 20160324 ◽  
Author(s):  
Sara B. Weinstein ◽  
Armand M. Kuris
Keyword(s):  
Animal Species ◽  
Generalist Predators ◽  
Substantial Fraction ◽  
Free Living ◽  
The Earth ◽  
Animal Diversity ◽  
Comprehensive Survey ◽  
Parasitic Lifestyle ◽  
Trophic Strategy ◽  
Consumer Strategies

Nearly half of all animals may have a parasitic lifestyle, yet the number of transitions to parasitism and their potential for species diversification remain unresolved. Based on a comprehensive survey of the animal kingdom, we find that parasitism has independently evolved at least 223 times in just 15 phyla, with the majority of identified independent parasitic groups occurring in the Arthropoda, at or below the level of Family. Metazoan parasitology is dominated by the study of helminthes; however, only 20% of independently derived parasite taxa belong to those groups, with numerous transitions also seen in Mollusca, Rotifera, Annelida and Cnidaria. Parasitism is almost entirely absent from deuterostomes, and although worm-like morphology and host associations are widespread across Animalia, the dual symbiotic and trophic interactions required for parasitism may constrain its evolution from antecedent consumer strategies such as generalist predators and filter feeders. In general, parasitic groups do not differ from their free-living relatives in their potential for speciation. However, the 10 largest parasitic clades contain 90% of described parasitic species, or perhaps 40% of all animal species. Hence, a substantial fraction of animal diversity on the Earth arose following these few transitions to a parasitic trophic strategy.

The effect of the nematode peptides SDPNFLRFamide (PF1) and SADPNFLRFamide (PF2) on synaptic transmission in the parasitic nematode Ascaris suum

Parasitology ◽  
1995 ◽  
Vol 110 (4) ◽  
pp. 449-455 ◽  
Author(s):  
L. Holden-Dye ◽  
C. J. Franks ◽  
R. G. Williams ◽  
R. J. Walker
Keyword(s):  
Synaptic Transmission ◽  
Parasitic Nematode ◽  
Ascaris Suum ◽  
Somatic Muscle ◽  
Free Living ◽  
Panagrellus Redivivus ◽  
Site Of Action ◽  
Free Living Nematode ◽  
Excitatory Junction Potentials ◽  
Input Conductance

SUMMARYThe action of two peptides isolated from the nematode Panagrellus redivivus, PF1 (SDPNFLRFamide) and PF2 (SADPNFLRFamide) have been studied on synaptic transmission in the motornervous system of the parasitic nematode Ascaris suum. Intracellular recordings were made from Ascaris somatic muscle cells and excitatory junction potentials (EJPs) elicited by stimulation of the ventral nerve cord. The EJPs were cholinergic as they were blocked by the Ascaris nicotinic receptor antagonist, benzoquinonium. PF1 caused a slow hyperpolarization, similar to the action of this peptide first reported by Bowman, Geary & Thompson (1990) and further characterized by Franks et al. (1994). The hyper-polarization was accompanied by a marked decrease in the amplitude of the EJPs with an EC50 of 311 ± 30 nM (n = 5). This inhibition is unlikely to be due to a post-synaptic site of action of the peptide as the muscle cell input conductance was not significantly altered by PF1 and furthermore the response to bath-applied acetylcholine was not inhibited by PF1 at concentrations up to 10μM (n = 6). PF2 also inhibited the EJPs in a similar manner to PF1. These studies indicate that both of the peptides isolated from the free-living nematode Panagrellus redivivus have biological activity in the parasitic nematode Ascaris suum. PF1 and PF2 have inhibitory actions in contrast to the predominantly excitatory actions of the Ascaris endogenous peptides AF1 (KNEFIRFamide) and AF2 (KHEYLRFamide). The potent actions of the Panagrellus neuropeptides PF1 and PF2 in Ascaris suggest that peptides with a similar or identical sequence may also occur in Ascarisand have an inhibitory role in the motornervous system.

scholarly journals Karyotype and reproduction mode of the rodent parasite Strongyloides venezuelensis

Parasitology ◽  
2014 ◽  
Vol 141 (13) ◽  
pp. 1736-1745 ◽  
Author(s):  
AKINA HINO ◽  
TERUHISA TANAKA ◽  
MAHO TAKAISHI ◽  
YUMIKO FUJII ◽  
JUAN E. PALOMARES-RIUS ◽  
...  
Keyword(s):  
Life Cycle ◽  
Ribosomal Rna ◽  
Parasitic Nematode ◽  
Karyotype Analysis ◽  
Cytological Analysis ◽  
Parasitic Stage ◽  
Free Living ◽  
Reproduction Mode ◽  
Strongyloides Venezuelensis ◽  
Parthenogenetic Reproduction

SUMMARYStrongyloides venezuelensis is a parasitic nematode that infects rodents. Although Strongyloides species described to date are known to exhibit parthenogenetic reproduction in the parasitic stage of their life cycle and sexual reproduction in the free-living stage, we did not observe any free-living males in S. venezuelensis in our strain, suggesting that the nematode is likely to depend on parthenogenetic reproduction. We confirmed by cytological analysis that S. venezuelensis produces eggs by parthenogenesis during the parasitic stage of its life cycle. Phylogenetic analysis using nearly the full length of 18S and D3 region of 28S ribosomal RNA gene suggested that S. venezuelensis is distantly related to another rodent parasite, namely Strongyloides ratti, but more closely related to a ruminant parasite, Strongyloides papillosus. Karyotype analysis revealed S. venezuelensis reproduces with mitotic parthenogenesis, and has the same number of chromosomes as S. papillosus (2n = 4), but differs from S. ratti (2n = 6) in this regard. These results, taken together, suggest that S. venezuelensis evolved its parasitism for rodents independently from S. ratti and, therefore, is likely to have a different reproductive strategy.

The effect of non-immune stresses on the development of Strongyloides ratti

Parasitology ◽  
2005 ◽  
Vol 131 (3) ◽  
pp. 383-392 ◽  
Author(s):  
M. CROOK ◽  
M. E. VINEY
Keyword(s):  
Immune Response ◽  
Parasitic Nematode ◽  
Host Immune Response ◽  
Natural Host ◽  
Adult Males ◽  
Free Living ◽  
Developmental Effects ◽  
Adult Females ◽  
Males And Females ◽  
Living Adult

Strongyloides ratti is a parasitic nematode of rats. The host immune response against S. ratti affects the development of its free-living generation, favouring the development of free-living adult males and females at the expense of directly developing, infective 3rd-stage larvae. However, how the host immune response brings about these developmental effects is not clear. To begin to investigate this, we have determined the effect of non-immune stresses on the development of S. ratti. These non-immune stresses were subcurative doses of the anthelmintic drugs Ivermectin, Dithiazanine iodide and Thiabendazole, and infection of a non-natural host, the mouse. These treatments produced the opposite developmental outcome to that of the host immune response. Thus, in infections treated with subcurative doses of Ivermectin, Dithiazanine iodide and in infections of a non-natural host, the sex ratio of developing larvae became more female-biased and the proportion of female larvae that developed into free-living adult females decreased. This suggests that the mechanism by which the host immune response and these non-immune stresses affect S. ratti development differs.

The use of Caenorhabditis elegans in parasitic nematode research

Parasitology ◽  
2004 ◽  
Vol 128 (S1) ◽  
pp. S49-S70 ◽  
Author(s):  
J. S. GILLEARD
Keyword(s):  
Caenorhabditis Elegans ◽  
Parasitic Nematode ◽  
Expression System ◽  
Nematode Species ◽  
Current Status ◽  
Evolutionary Development ◽  
Parasitic Nematodes ◽  
Free Living ◽  
C Elegans ◽  
Free Living Nematode

There is increasing interest in the use of the free-living nematode Caenorhabditis elegans as a tool for parasitic nematode research and there are now a number of compelling examples of its successful application. C. elegans has the potential to become a standard tool for molecular helminthology researchers, just as yeast is routinely used by molecular biologists to study vertebrate biology. However, in order to exploit C. elegans in a meaningful manner, we need a detailed understanding of the extent to which different aspects of C. elegans biology have been conserved with particular groups of parasitic nematodes. This review first considers the current state of knowledge regarding the conservation of genome organisation across the nematode phylum and then discusses some recent evolutionary development studies in free-living nematodes. The aim is to provide some important concepts that are relevant to the extrapolation of information from C. elegans to parasitic nematodes and also to the interpretation of experiments that use C. elegans as a surrogate expression system. In general, examples have been specifically chosen because they highlight the importance of careful experimentation and interpretation of data. Consequently, the focus is on the differences that have been found between nematode species rather than the similarities. Finally, there is a detailed discussion of the current status of C. elegans as a heterologous expression system to study parasite gene function and regulation using successful examples from the literature.

THE MORPHOLOGY AND DEVELOPMENT OF THE SHEEP NEMATODE, STRONGYLOIDES PAPILLOSUS (WEDL, 1856)

1950 ◽  
Vol 28d (3) ◽  
pp. 173-196 ◽  
Author(s):  
M. A. Basir
Keyword(s):  
The Body ◽  
The Other ◽  
Free Living ◽  
Experimental Animals ◽  
Infective Larvae ◽  
Time Required ◽  
Parasitic Generation

In studying the morphology and development of Strongyloides papillosus it has been shown that four molts occur during the development of the free-living sexual adults, two molts in the formation of the infective larvae, and two molts in the development of the parasitic adults from the infective larvae. The last two occur in the body of the host, one in the lungs and the other in the intestine. The time required by the eggs to hatch and the larvae to develop to either the infective larvae or the free-living adults varies with temperature; at 27 °C. it is 6 hr. and 28 hr., respectively. The so-called "spears" in the oesophagus of the free-living adults were found to be the cuticularized tubular endings of the rays of the oesophageal lumen. The head in the free-living adults bears two well developed lips and four papillae, while in parasitic adults it has four lips and four papillae. The tail of the free-living male bears two pairs of preanal and two pairs of postanal papillae. No males were found in the parasitic generation, while parasitic females were found only in the intestine of experimental animals.

scholarly journals Experimental temperature manipulations alter songbird autumnal nocturnal migratory restlessness

2017 ◽  
Vol 4 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Adrienne Berchtold ◽  
Ira Nightingale ◽  
Caitlin Vandermeer ◽  
Scott A. MacDougall-Shackleton
Keyword(s):  
Environmental Cues ◽  
Migratory Restlessness ◽  
Zonotrichia Albicollis ◽  
Free Living ◽  
Related Factors ◽  
Time Migration ◽  
Current Location ◽  
Infra Red ◽  
The Many ◽  
Migrating Birds

AbstractMigrating birds may respond to a variety of environmental cues in order to time migration. During the migration season nocturnally migrating songbirds may migrate or stop-over at their current location, and when migrating they may vary the rate or distance of migration on any given night. It has long been known that a variety of weather-related factors including wind speed and direction, and temperature, are correlated with migration in free-living birds, however these variables are often correlated with each other. In this study we experimentally manipulated temperature to determine if it would directly modulate nocturnal migratory restlessness in songbirds. We experimentally manipulated temperature between 4, 14, and 24°C and monitored nocturnal migratory restlessness during autumn in white-throated sparrows (Zonotrichia albicollis). White-throated sparrows are relatively shortdistance migrants with a prolonged autumnal migration, and we thus predicted they might be sensitive to weatherrelated cues when deciding whether to migrate or stopover. At warm temperatures (24°C) none of the birds exhibited migratory restlessness. The probability of exhibiting migratory restlessness, and the intensity of this restlessness (number of infra-red beam breaks) increased at cooler (14°C, 4°C) temperatures. These data support the hypothesis that one of the many factors that birds use when making behavioural decisions during migration is temperature, and that birds can respond to temperature directly independently of other weather-related cues.

scholarly journals Rhabditophanes diutinus a parthenogenetic clade IV nematode with dauer larvae

2020 ◽  
Vol 16 (12) ◽  
pp. e1009113
Author(s):  
Alex Dulovic ◽  
Tess Renahan ◽  
Waltraud Röseler ◽  
Christian Rödelsperger ◽  
Ann M. Rose ◽  
...  
Keyword(s):  
Life Cycle ◽  
Expression Patterns ◽  
Parasitic Nematodes ◽  
Comparative Genomic ◽  
Phylogenetic Distance ◽  
Life Stages ◽  
Model Species ◽  
Free Living ◽  
Infective Larvae ◽  
Dauer Larvae

Comparative studies using non-parasitic model species such as Caenorhabditis elegans, have been very helpful in investigating the basic biology and evolution of parasitic nematodes. However, as phylogenetic distance increases, these comparisons become more difficult, particularly when outside of the nematode clade to which C. elegans belongs (V). One of the reasons C. elegans has nevertheless been used for these comparisons, is that closely related well characterized free-living species that can serve as models for parasites of interest are frequently not available. The Clade IV parasitic nematodes Strongyloides are of great research interest due to their life cycle and other unique biological features, as well as their medical and veterinary importance. Rhabditophanes, a closely related free-living genus, forms part of the Strongyloidoidea nematode superfamily. Rhabditophanes diutinus (= R. sp. KR3021) was included in the recent comparative genomic analysis of the Strongyloididae, providing some insight into the genomic nature of parasitism. However, very little is known about this species, limiting its usefulness as a research model. Here we provide a species description, name the species as R. diutinus and investigate its life cycle and subsequently gene expression in multiple life stages. We identified two previously unreported starvation induced life stages: dauer larvae and arrested J2 (J2A) larvae. The dauer larvae are morphologically similar to and are the same developmental stage as dauers in C. elegans and infective larvae in Strongyloides. As in C. elegans and Strongyloides, dauer formation is inhibited by treatment with dafachronic acid, indicating some genetic control mechanisms are conserved. Similarly, the expression patterns of putative dauer/infective larva control genes resemble each other, in particular between R. diutinus and Strongyloides spp. These findings illustrate and increase the usefulness of R. diutinus as a non-parasitic, easy to work with model species for the Strongyloididae for studying the evolution of parasitism as well as many aspects of the biology of Strongyloides spp, in particular the formation of infective larvae.

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