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Richards MH. Social evolution and reproductive castes in trematode parasites. Proc Natl Acad Sci U S A 2024; 121:e2414228121. [PMID: 39226370 PMCID: PMC11406270 DOI: 10.1073/pnas.2414228121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024] Open
Affiliation(s)
- Miriam H Richards
- Department of Biological Sciences, Brock University, St. Catharines, ON L2S 3A1, Canada
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2
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Zhang F, Li J, Zhang S, Chen T, Zhang H. Prevalence and species identification of trematode metacercariae in Qiqihar, Northeast China. Front Microbiol 2024; 15:1464988. [PMID: 39318428 PMCID: PMC11420014 DOI: 10.3389/fmicb.2024.1464988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2024] [Accepted: 08/28/2024] [Indexed: 09/26/2024] Open
Abstract
Fishborne trematode (FBT) is an important group of parasites that are endemic worldwide to a certain extent. However, despite the epidemiological significance, the species and phylogenetic evolution characteristics of FBT metacercariae have not been well studied. In this study, a total of 600 Pseudorasbora parva (P. parva) specimens were collected from Qiqihar, 61.8% (371/600) were found to be infected with trematode metacercariae. A total of three kinds of trematodes metacercariae were obtained, and they were identified as Clonorchis sinensis (C. sinensis), Metorchis orientalis (M. orientalis), and Metorchis taiwanensis (M. taiwanensis) by morphological and phylogenetic analysis with infection rates of 47.7% (286/600), 15.5% (93/600), and 23.7% (142/600), respectively. Meanwhile, a survey of the three trematodes metacercariae showed that the infection rate of C. sinensis metacercariae was the highest in September, up to 66% (66/100), and the lowest in June at 26% (26/100). The infection rate of M. orientalis metacercariae was the highest in October at 26% (26/100) and the lowest in June at 5% (5/100). The infection rate of M. taiwanensis metacercariae was at its peak in November at 36% (36/100) and the lowest in July at 15% (15/100). The co-infection of metacercariae of C. sinensis and M. taiwanensis was the most common and reached a peak in October, and their infection rate was higher in autumn than in summer. The peak of infection intensity of metacercariae for C. sinensis, M. orientalis, and M. taiwanensis were different: C. sinensis was 24/g in September, M. orientalis was 7/g in October, and M. taiwanensis was 10/g in November. From the above results, it was confirmed that three species of trematodes metacercaria played an important role in infection of second intermediate hosts in Qiqihar region. Studying the morphological characteristics and sequencing the ITS2 gene for a phylogenetic tree of them will be useful for future molecular evolution, biology, and ecology of trematode metacercariae.
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Affiliation(s)
- Fengyu Zhang
- Department of Clinical Laboratory, Suining Central Hospital, Suining, China
- School of Medical Technology, Qiqihar Medical University, Qiqihar, China
| | - Jianke Li
- School of Medical Technology, Qiqihar Medical University, Qiqihar, China
| | - Shaocheng Zhang
- Department of Laboratory Medicine, The Second Affiliated Hospital of Chengdu Medical College (Nuclear Industry 416 Hospital), Chengdu, China
- School of Clinical Medicine, Chengdu Medical College, Chengdu, China
| | - Ting Chen
- Department of Pathology, Hospital of Chengdu Office of People’s Government of Tibetan Autonomous Region, Chengdu, China
| | - Hao Zhang
- School of Medical Technology, Qiqihar Medical University, Qiqihar, China
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3
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Metz DCG, Hechinger RF. The physical soldier caste of an invasive, human-infecting flatworm is morphologically extreme and obligately sterile. Proc Natl Acad Sci U S A 2024; 121:e2400953121. [PMID: 39042696 PMCID: PMC11295071 DOI: 10.1073/pnas.2400953121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Accepted: 06/16/2024] [Indexed: 07/25/2024] Open
Abstract
We show that the globally invasive, human-infectious flatworm, Haplorchis pumilio, possesses the most physically specialized soldier caste yet documented in trematodes. Soldiers occur in colonies infecting the first intermediate host, the freshwater snail Melanoides tuberculata, and are readily distinguishable from immature and mature reproductive worms. Soldiers possess a pharynx five times absolutely larger than those of immature and mature reproductives, lack a germinal mass, and have a different developmental trajectory than reproductives, indicating that H. pumilio soldiers constitute a reproductively sterile physical caste. Neither immature nor mature reproductives showed aggression in in vitro trials, but soldiers readily attacked heterospecific trematodes that coinfect their host. Ecologically, we calculate that H. pumilio caused ~94% of the competitive deaths in the guild of trematodes infecting its host snail in its invasive range in southern California. Despite being a dominant competitor, H. pumilio soldiers did not attack conspecifics from other colonies. All prior reports documenting division of labor and a trematode soldier caste have involved soldiers that may be able to metamorphose to the reproductive stage and have been from nonhuman-infectious marine species; this study provides clear evidence for an obligately sterile trematode soldier, while extending the phenomenon of a trematode soldier caste to freshwater and to an invasive species of global public health concern.
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Affiliation(s)
- Daniel C. G. Metz
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA92093
| | - Ryan F. Hechinger
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA92093
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4
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Neal AT, Stettner M, Ortega-Cotto R, Dieringer D, Reed LC. Freshwater trematodes differ from marine trematodes in patterns connected with division of labor. PeerJ 2024; 12:e17211. [PMID: 38623495 PMCID: PMC11017974 DOI: 10.7717/peerj.17211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 03/18/2024] [Indexed: 04/17/2024] Open
Abstract
Background Prior research suggests that trematode rediae, a developmental stage of trematode parasites that reproduce clonally within a snail host, show evidence of division of labor (DOL). Single-species infections often have two morphologically distinct groups: small rediae, the 'soldiers', are active, aggressive, and do not appear to reproduce; large rediae, the 'reproductives', are larger, sluggish, and full of offspring. Most data supporting DOL come from trematodes infecting marine snails, while data from freshwater trematodes are more limited and generally do not supported DOL. The shorter lifespan typical of freshwater snails may partially explain this difference: defending a short-lived host at the expense of reproduction likely provides few advantages. Here, we present data from sixty-one colonies spanning twenty species of freshwater trematode exploring morphological and behavioral patterns commonly reported from marine trematodes believed to have DOL. Methods Trematode rediae were obtained from sixty-one infected snails collected in central Vermont, USA. A portion of the COI gene was sequenced to make tentative species identifications ('COI species'). Samples of rediae were photographed, observed, and measured to look for DOL-associated patterns including a bimodal size distribution, absence of embryos in small rediae, and pronounced appendages and enlarged pharynges (mouthparts) in small rediae. Additional rediae were used to compare activity levels and likelihood to attack heterospecific trematodes in large vs. small rediae. Results Many of the tests for DOL-associated patterns showed mixed results, even among colonies of the same COI species. However, we note a few consistent patterns. First, small rediae of most colonies appeared capable of reproduction, and we saw no indication (admittedly based on a small sample size and possibly insufficient attack trial methodology) that small rediae were more active or aggressive. This differs from patterns reported from most marine trematodes. Second, the small rediae of most colonies had larger pharynges relative to their body size than large rediae, consistent with marine trematodes. We also observed that colonies of three sampled COI species appear to produce a group of large rediae that have distinctly large pharynges. Conclusions We conclude that these freshwater species likely do not have a group of specialized non-reproductive soldiers because small rediae of at least some colonies in almost every species do appear to produce embryos. We cannot rule out the possibility that small rediae act as a temporary soldier caste. We are intrigued by the presence of rediae with enlarged pharynges in some species and propose that they may serve an adaptive role, possibly similar to the defensive role of small 'soldier' rediae of marine trematodes. Large-pharynx rediae have been documented in other species previously, and we encourage future efforts to study these large-pharynx rediae.
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Hechinger RF, Metz DCG. Social evolution: Diverse divisions of labor in trematode parasites. Curr Biol 2023; 33:R1238-R1240. [PMID: 38052175 DOI: 10.1016/j.cub.2023.10.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Some animal societies solve problems, like foraging or defense, by cooperatively dividing labor. A new discovery highlights that trematodes are unique in forming different societies at multiple parts of their complex life cycle with distinct divisions of labor to solve different problems.
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Affiliation(s)
- Ryan F Hechinger
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA.
| | - Daniel C G Metz
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA
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6
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Krupenko D, Miroliubov A, Kryukov E, Faure L, Minemizu R, Haag L, Lundgren M, Kameneva P, Kastriti ME, Adameyko I. Polymorphic parasitic larvae cooperate to build swimming colonies luring hosts. Curr Biol 2023; 33:4524-4531.e4. [PMID: 37741283 DOI: 10.1016/j.cub.2023.08.090] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/15/2023] [Accepted: 08/30/2023] [Indexed: 09/25/2023]
Abstract
Parasites have evolved a variety of astonishing strategies to survive within their hosts, yet the most challenging event in their personal chronicles is the passage from one host to another. It becomes even more complex when a parasite needs to pass through the external environment. Therefore, the free-living stages of parasites present a wide range of adaptations for transmission. Parasitic flatworms from the group Digenea (flukes) have free-living larvae, cercariae, which are remarkably diverse in structure and behavior.1,2 One of the cercariae transmission strategies is to attain a prey-like appearance for the host.3 This can be done through the formation of a swimming aggregate of several cercariae adjoined together by their tails.4 Through the use of live observations and light, electron, and confocal microscopy, we described such a supposedly prey-mimetic colony comprising cercariae of two distinct morphotypes. They are functionally specialized: larger morphotype (sailors) enable motility, and smaller morphotype (passengers) presumably facilitate infection. The analysis of local read alignments between the two samples reveals that both cercaria types have identical 18S, 28S, and 5.8S rRNA genes. Further phylogenetic analysis of these ribosomal sequences indicates that our specimen belongs to the digenean family Acanthocolpidae, likely genus Pleorchis. This discovery provides a unique example and a novel insight into how morphologically and functionally heterogeneous individuals of the same species cooperate to build colonial organisms for the purpose of infection. This strategy bears resemblance to the cooperating castes of the same species found among insects.5.
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Affiliation(s)
- Darya Krupenko
- Department of Invertebrate Zoology, Saint Petersburg University, Saint Petersburg 199034, Russia.
| | - Aleksei Miroliubov
- Laboratory of Parasitic Worms and Protists, Zoological Institute, Russian Academy of Science, Universitetskaya Embankment, 1, Saint Petersburg, Russia
| | - Emil Kryukov
- Department of Ophthalmology, Schepens Eye Research Institute of Massachusetts. Eye and Ear, Boston, MA 02115, USA; Department of Ophthalmology, Harvard Medical School, Boston, MA 02115, USA
| | - Louis Faure
- Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Ryo Minemizu
- Ryo Minemizu Photo Office, Shizuoka 411-0907, Japan
| | - Lars Haag
- Department of Laboratory Medicine, Karolinska Institutet, 141 57 Huddinge, Sweden
| | - Magnus Lundgren
- Department of Organismal Biology, University of Uppsala, 752 36 Uppsala, Sweden
| | - Polina Kameneva
- Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Maria Eleni Kastriti
- Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Igor Adameyko
- Department of Neuroimmunology, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria; Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Stockholm, Sweden.
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7
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Scott ME. Helminth-host-environment interactions: Looking down from the tip of the iceberg. J Helminthol 2023; 97:e59. [PMID: 37486085 DOI: 10.1017/s0022149x23000433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
In 1978, the theory behind helminth parasites having the potential to regulate the abundance of their host populations was formalized based on the understanding that those helminth macroparasites that reduce survival or fecundity of the infected host population would be among the forces limiting unregulated host population growth. Now, 45 years later, a phenomenal breadth of factors that directly or indirectly affect the host-helminth interaction has emerged. Based largely on publications from the past 5 years, this review explores the host-helminth interaction from three lenses: the perspective of the helminth, the host, and the environment. What biotic and abiotic as well as social and intrinsic host factors affect helminths? What are the negative, and positive, implications for host populations and communities? What are the larger-scale implications of the host-helminth dynamic on the environment, and what evidence do we have that human-induced environmental change will modify this dynamic? The overwhelming message is that context is everything. Our understanding of second-, third-, and fourth-level interactions is extremely limited, and we are far from drawing generalizations about the myriad of microbe-helminth-host interactions.Yet the intricate, co-evolved balance and complexity of these interactions may provide a level of resilience in the face of global environmental change. Hopefully, this albeit limited compilation of recent research will spark new interdisciplinary studies, and application of the One Health approach to all helminth systems will generate new and testable conceptual frameworks that encompass our understanding of the host-helminth-environment triad.
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Affiliation(s)
- M E Scott
- Institute of Parasitology, McGill University (Macdonald Campus), 21,111 Lakeshore Road, Ste-Anne de Bellevue, QuebecH9X 3V9, Canada
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8
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Lucius R. Dicrocoelium dendriticum. Trends Parasitol 2022; 38:1089-1090. [PMID: 36192304 DOI: 10.1016/j.pt.2022.09.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 09/08/2022] [Accepted: 09/12/2022] [Indexed: 01/13/2023]
Affiliation(s)
- Richard Lucius
- Department of Molecular Parasitology, Humboldt-Universität zu Berlin, 10115 Berlin, Germany.
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9
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Criscione CD, Hulke JM, Goater CP. Trematode Clone Abundance Distributions: An Eco-Evolutionary Link between Parasite Transmission and Parasite Mating Systems. J Parasitol 2022; 108:565-576. [DOI: 10.1645/22-68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Affiliation(s)
- Charles D. Criscione
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, Texas 77843
| | - Jenna M. Hulke
- Department of Biology, Texas A&M University, 3258 TAMU, College Station, Texas 77843
| | - Cameron P. Goater
- Department of Biological Sciences, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada
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Jorge F, Dheilly NM, Froissard C, Poulin R. Association between parasite microbiomes and caste development and colony structure in a social trematode. Mol Ecol 2022; 31:5608-5617. [PMID: 36004565 PMCID: PMC9826137 DOI: 10.1111/mec.16671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 08/17/2022] [Accepted: 08/19/2022] [Indexed: 01/11/2023]
Abstract
Division of labour through the formation of morphologically and functionally distinct castes is a recurring theme in the evolution of animal sociality. The mechanisms driving the differentiation of individuals into distinct castes remain poorly understood, especially for animals forming clonal colonies. We test the association between microbiomes and caste formation within the social trematode Philophthalmus attenuatus, using a metabarcoding approach targeting the bacterial 16S SSU rRNA gene. Clonal colonies of this trematode within snail hosts comprise large reproductive individuals which produce dispersal stages, and small, non-reproducing soldiers which defend the colony against invaders. In colonies extracted directly from field-collected snails, reproductives harboured more diverse bacterial communities than soldiers, and reproductives and soldiers harboured distinct bacterial communities, at all taxonomic levels considered. No single bacterial taxon showed high enough prevalence in either soldiers or reproductives to be singled out as a key driver, indicating that the whole microbial community contributes to these differences. Other colonies were experimentally exposed to antibiotics to alter their bacterial communities, and sampled shortly after treatment and weeks later after allowing for turnover of colony members. At those time points, bacterial communities of the two castes still differed across all antibiotic treatments; however, the caste ratio within colonies changed: after antibiotic disruption and turnover of individuals, new individuals were more likely to become reproductives than in undisturbed control colonies. Our results reveal that each caste has a distinct microbiome; whether the social context affects the microbiota, or whether microbes contribute to modulating the phenotype of individuals, remains to be determined.
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Affiliation(s)
- Fátima Jorge
- Otago Micro and Nano Imaging, Electron Microscopy UnitUniversity of OtagoDunedinNew Zealand
| | - Nolwenn M. Dheilly
- School of Marine and Atmospheric SciencesStony Brook UniversityStony BrookNew YorkUSA,Unité Génétique Virale de Biosécurité, Agence Nationale de Sécurité Sanitaire de l'Alimentation, de l'Environnement et du Travail ‐ Laboratoire de Ploufragan‐PlouzanéANSESPloufraganFrance
| | | | - Robert Poulin
- Department of ZoologyUniversity of OtagoDunedinNew Zealand
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When being flexible matters: Ecological underpinnings for the evolution of collective flexibility and task allocation. Proc Natl Acad Sci U S A 2022; 119:e2116066119. [PMID: 35486699 PMCID: PMC9170069 DOI: 10.1073/pnas.2116066119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
A central problem in evolutionary biology is explaining variation in the organization of task allocation across collective systems. Why do human cells irreversibly adopt a task during development (e.g., kidney vs. liver cell), while sponge cells switch between different cell types? And why have only some ant species evolved specialized castes of workers for particular tasks? Although it seems reasonable to suppose that such differences reflect, at least partially, the different ecological pressures that systems face, there is no general understanding of how a system’s dynamic environment shapes its task allocation. To this end, we develop a general mathematical framework that reveals how simple ecological considerations could potentially explain cross-system variation in task allocation—including in flexibility, specialization, and (in)activity. Task allocation is a central feature of collective organization. Living collective systems, such as multicellular organisms or social insect colonies, have evolved diverse ways to allocate individuals to different tasks, ranging from rigid, inflexible task allocation that is not adjusted to changing circumstances to more fluid, flexible task allocation that is rapidly adjusted to the external environment. While the mechanisms underlying task allocation have been intensely studied, it remains poorly understood whether differences in the flexibility of task allocation can be viewed as adaptive responses to different ecological contexts—for example, different degrees of temporal variability. Motivated by this question, we develop an analytically tractable mathematical framework to explore the evolution of task allocation in dynamic environments. We find that collective flexibility is not necessarily always adaptive, and fails to evolve in environments that change too slowly (relative to how long tasks can be left unattended) or too quickly (relative to how rapidly task allocation can be adjusted). We further employ the framework to investigate how environmental variability impacts the internal organization of task allocation, which allows us to propose adaptive explanations for some puzzling empirical observations, such as seemingly unnecessary task switching under constant environmental conditions, apparent task specialization without efficiency benefits, and high levels of individual inactivity. Altogether, this work provides a general framework for probing the evolved diversity of task allocation strategies in nature and reinforces the idea that considering a system’s ecology is crucial to explaining its collective organization.
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Soldánová M, Kundid P, Scholz T, Kristoffersen R, Knudsen R. Somatic Dimorphism in Cercariae of a Bird Schistosome. Pathogens 2022; 11:pathogens11030290. [PMID: 35335614 PMCID: PMC8953619 DOI: 10.3390/pathogens11030290] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/20/2022] [Accepted: 02/22/2022] [Indexed: 11/16/2022] Open
Abstract
Phenotypic polymorphism is a commonly observed phenomenon in nature, but extremely rare in free-living stages of parasites. We describe a unique case of somatic polymorphism in conspecific cercariae of the bird schistosome Trichobilharzia sp. “peregra”, in which two morphs, conspicuously different in their size, were released from a single Radix balthica snail. A detailed morphometric analysis that included multiple morphological parameters taken from 105 live and formalin-fixed cercariae isolated from several naturally infected snails provided reliable evidence for a division of all cercariae into two size groups that contained either large or small individuals. Large morph (total body length of 1368 and 1339 μm for live and formalin-fixed samples, respectively) differed significantly nearly in all morphological characteristics compared to small cercariae (total body length of 976 and 898 μm for live and formalin samples, respectively), regardless of the fixation method. Furthermore, we observed that small individuals represent the normal/commonly occurring phenotype in snail populations. The probable causes and consequences of generating an alternative, much larger phenotype in the parasite infrapopulation are discussed in the context of transmission ecology as possible benefits and disadvantages facilitating or preventing the successful completion of the life cycle.
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Affiliation(s)
- Miroslava Soldánová
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic; (P.K.); (T.S.)
- Correspondence:
| | - Petra Kundid
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic; (P.K.); (T.S.)
- Department of Parasitology, Faculty of Science, University of South Bohemia in České Budějovice, 370 05 České Budějovice, Czech Republic
| | - Tomáš Scholz
- Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, 370 05 České Budějovice, Czech Republic; (P.K.); (T.S.)
- Department of Parasitology, Faculty of Science, University of South Bohemia in České Budějovice, 370 05 České Budějovice, Czech Republic
| | - Roar Kristoffersen
- Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, N9037 Tromsø, Norway; (R.K.); (R.K.)
| | - Rune Knudsen
- Department of Arctic and Marine Biology, Faculty of Biosciences, Fisheries and Economics, UiT The Arctic University of Norway, N9037 Tromsø, Norway; (R.K.); (R.K.)
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13
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Cribb TH, Cutmore SC, Bray RA. The biodiversity of marine trematodes: then, now and in the future. Int J Parasitol 2021; 51:1085-1097. [PMID: 34757087 DOI: 10.1016/j.ijpara.2021.09.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/10/2021] [Accepted: 09/16/2021] [Indexed: 10/19/2022]
Abstract
Trematodes are the richest class of platyhelminths in the marine environment, infecting all classes of marine vertebrates as sexual adults and many phyla of marine invertebrates as part of their life cycles. Despite the cryptic nature of their existence (almost all marine trematodes are internal parasites), they have been the focus of study for almost 250 years, with the first species described in 1774. Here we review progress in the study of the "biodiversity" of these parasites, contrasting the progress made in the last 50 years (post-1971) to that in the almost 200 years before it (pre-1972). We consider an understanding of biodiversity to require knowledge of the species present in the system, an understanding of their evolutionary relationships (which informs higher classification), and, specifically for trematodes, an understanding of their complex life cycles. The fauna is now large, comprising well over 5,000 species. Although species description continues, we see evidence of a slow-down in all aspects of discovery. There has been only one completely new family identified since 1984 and the proposal of new genera is in decline as is the description of new species, especially for those of tetrapods. However, the extent to which this slow-down reflects an approach to the richness asymptote is made uncertain by changes in the field; reduced effort and difficulty of study may be important components of the effect. Regardless of how close we are to a complete description of the fauna, we infer that the outline is well-understood although the details are not. Adoption of molecular methodologies over the last 40 years have complemented morphometric analyses to facilitate objective recognition of species; however, despite these objective data, there is still inconsistency between authors on species delimitation. Molecular methodologies have also completely revolutionised inference of relationships at all levels, from within genera to between orders, and underpinned elucidation of novel life cycles. We expect the next 50 years to produce further dividends from technological innovations. The backdrop to the field will be global environmental concerns and the growing problem of funding for basic biodiversity studies.
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Affiliation(s)
- Thomas H Cribb
- The University of Queensland, School of Biological Sciences, St Lucia, Queensland 4072, Australia.
| | - Scott C Cutmore
- The University of Queensland, School of Biological Sciences, St Lucia, Queensland 4072, Australia
| | - Rodney A Bray
- Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK
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14
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Abstract
Some parasitoid wasps possess soldier castes during their parasitic larval stage, but are often neglected from our evolutionary theories explaining caste systems in animal societies. This is primarily due to the polyembryonic origin of their societies. However, recent discoveries of polyembryonic trematodes (i.e. flatworms) possessing soldier castes require us to reconsider this reasoning. I argue we can benefit from including these polyembryonic parasites in eusocial discussions, for polyembryony and parasitism are taxonomically vast and influence the evolution of social behaviours and caste systems in various circumstances. Despite their polyembryony, their social evolution can be explained by theories of eusociality designed for parent–offspring groups, which are the subjects of most social evolution research. Including polyembryonic parasites in these theories follows the trend of major evolutionary transitions theory expanding social evolution research into all levels of biological organization. In addition, these continued discoveries of caste systems in parasites suggest social evolution may be more relevant to parasitology than currently acknowledged.
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Affiliation(s)
- Brian A Whyte
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA, USA
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15
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Size variation does not act as insurance in bumble bees; instead, workers add weight in an unpredictable environment. Anim Behav 2020. [DOI: 10.1016/j.anbehav.2020.10.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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16
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Cost of interspecific competition between trematode colonies. J Helminthol 2020; 94:e139. [PMID: 32238196 DOI: 10.1017/s0022149x20000243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In a range of trematode species, specific members of the parthenitae colony infecting the molluscan first intermediate host appear specialized for defence against co-infecting species. The evolution of such division of labour requires that co-infection entails fitness costs. Yet, this premise has very rarely been tested in species showing division of labour. Using Himasthla elongata (Himasthlidae) and Renicola roscovita (Renicolidae) infecting periwinkles Littorina littorea as study system, we show that the size of emerged cercariae is markedly reduced in both parasite species when competing over host resources. Cercarial longevity, on the other hand, is negatively influenced by competition only in R. roscovita. Season, which may impact the nutritional state of the host, also affects cercarial size, but only in H. elongata. Hence, our study underlines that cercarial quality is, indeed, compromised by competition, not only in the inferior R. roscovita (no division of labour) but also in the competitively superior H. elongata (division of labour).
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Clonemate cotransmission supports a role for kin selection in a puppeteer parasite. Proc Natl Acad Sci U S A 2020; 117:5970-5976. [PMID: 32123093 DOI: 10.1073/pnas.1922272117] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Host manipulation by parasites is a fascinating evolutionary outcome, but adaptive scenarios that often accompany even iconic examples in this popular field of study are speculative. Kin selection has been invoked as a means of explaining the evolution of an altruistic-based, host-manipulating behavior caused by larvae of the lancet fluke Dicrocoelium dendriticum in ants. Specifically, cotransmission of larval clonemates from a snail first host to an ant second host is presumed to lead to a puppeteer parasite in the ant's brain that has clonemates in the ant abdomen. Clonal relatedness between the actor (brain fluke) and recipients (abdomen flukes) enables kin selection of the parasite's host-manipulating trait, which facilitates transmission of the recipients to the final host. However, the hypothesis that asexual reproduction in the snail leads to a high abundance of clonemates in the same ant is untested. Clonal relationships between the manipulator in the brain and the nonmanipulators in the abdomen are also untested. We provide empirical data on the lancet fluke's clonal diversity within its ant host. In stark contrast to other trematodes, which do not exhibit the same host-manipulating behavioral trait, the lancet fluke has a high abundance of clonemates. Moreover, our data support existing theory that indicates that the altruistic behavior can evolve even in the presence of multiple clones within the same ant host. Importantly, our analyses conclusively show clonemate cotransmission into ants, and, as such, we find support for kin selection to drive the evolution and maintenance of this iconic host manipulation.
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