Flatworm Species Research Articles

Helminths and Cancers From the Evolutionary Perspective.

Helminths include free-living and parasitic Platyhelminthes and Nematoda which infect millions of people worldwide. Some Platyhelminthes species of blood flukes (Schistosoma haematobium, Schistosoma japonicum, and Schistosoma mansoni) and liver flukes (Clonorchis sinensis and Opisthorchis viverrini) are known to be involved in human cancers. Other helminths are likely to be carcinogenic. Our main goals are to summarize the current knowledge of human cancers caused by Platyhelminthes, point out some helminth and human biomarkers identified so far, and highlight the potential contributions of phylogenetics and molecular evolution to cancer research. Human cancers caused by helminth infection include cholangiocarcinoma, colorectal hepatocellular carcinoma, squamous cell carcinoma, and urinary bladder cancer. Chronic inflammation is proposed as a common pathway for cancer initiation and development. Furthermore, different bacteria present in gastric, colorectal, and urogenital microbiomes might be responsible for enlarging inflammatory and fibrotic responses in cancers. Studies have suggested that different biomarkers are involved in helminth infection and human cancer development; although, the detailed mechanisms remain under debate. Different helminth proteins have been studied by different approaches. However, their evolutionary relationships remain unsolved. Here, we illustrate the strengths of homology identification and function prediction of uncharacterized proteins from genome sequencing projects based on an evolutionary framework. Together, these approaches may help identifying new biomarkers for disease diagnostics and intervention measures. This work has potential applications in the field of phylomedicine (evolutionary medicine) and may contribute to parasite and cancer research.

Microstomum (Platyhelminthes, Macrostomorpha, Microstomidae) from the Swedish west coast: two new species and a population description

Two new species of marine Platyhelminthes, Microstomum laurae sp. nov. and Microstomum edmondi sp. nov. (Macrostomida: Microstomidae) are described from the west coast of Sweden. Microstomum laurae sp. nov. is distinguished by the following combination of characters: rounded anterior and posterior ends; presence of approximately 20 adhesive papillae on the posterior rim; paired lateral red eyespots located level with the brain; preoral gut extending anterior to brain and very small sensory pits. Microstomum edmondi sp. nov. is a protandrous hermaphrodite with a single ovary, single testis and male copulatory organ with stylet. It is characterized by a conical pointed anterior end, a blunt posterior end with numerous adhesive papillae along the rim, and large ciliary pits. The stylet is shaped as a narrow funnel with a short, arched tip. In addition, the first records of fully mature specimens of Microstomum rubromaculatum von Graff, 1882 from Fiskebäckskil and a phylogenetic analysis of Microstomum Schmidt, 1848 based on the mitochondrial cytochrome oxidase I (COI) gene are presented.

The regenerative flatworm Macrostomum lignano, a model organism with high experimental potential.

Understanding the process of regeneration has been one of the longstanding scientific aims, from a fundamental biological perspective, as well as within the applied context of regenerative medicine. Because regeneration competence varies greatly between organisms, it is essential to investigate different experimental animals. The free-living marine flatworm Macrostomum lignano is a rising model organism for this type of research, and its power stems from a unique set of biological properties combined with amenability to experimental manipulation. The biological properties of interest include production of single-cell fertilized eggs, a transparent body, small size, short generation time, ease of culture, the presence of a pluripotent stem cell population, and a large regeneration competence. These features sparked the development of molecular tools and resources for this animal, including high-quality genome and transcriptome assemblies, gene knockdown, in situ hybridization, and transgenesis. Importantly, M. lignano is currently the only flatworm species for which transgenesis methods are established. This review summarizes biological features of M. lignano and recent technological advances towards experimentation with this animal. In addition, we discuss the experimental potential of this model organism for different research questions related to regeneration and stem cell biology.

Two new species of freshwater Macrostomum (Rhabditophora: Macrostomorpha) found in China.

There is limited information about the ecology of freshwater flatworms in China, in particular, the members of the genus Macrostomum. Surveying freshwater bodies to explore the species diversity is the first step to obtain more ecological information about those flatworms. We hereby report the discovery of two new species of freshwater flatworms in Macrostomum. Macrostomum chongqingensis Lin and Wang, n. sp. was discovered from stones in the shallow water of Jialing River bed near Chongqing. Macrostomum zhaoqingensis Lin and Wang, n. sp. was discovered in the water of Xing Lake near Zhaoqing city, Guangdong province. Xing Lake is a part of an ancient river that has changed its course. For each species, we describe the morphology of the whole specimen, penis stylet, and sperm, as well as other internal anatomical features based on serial sections. We determined 18S, 28S rDNA and COI sequences from the two new species, and performed a phylogenetic analysis to confirm the status and evolutionary position of the two new species. We discuss the significance of our discoveries in terms of flatworm biodiversity studies in China and the Oriental realm.

A new species of freshwater flatworm (Platyhelminthes, Tricladida, Dendrocoelidae) inhabiting a chemoautotrophic groundwater ecosystem in Romania

We report the description of a new species of freshwater flatworm of the genus Dendrocoelum inhabiting the chemoautotrophic ecosystem of Movile Cave as well as several sulfidic wells in the nearby town of Mangalia, thus representing the first planarian species fully described from this extreme biotope. The species was also found in non-sulfidic wells localized in villages in the vicinity of the cave with a total of nine examined populations. Dendrocoelum obstinatum Stocchino & Sluys, sp. nov. represents the first triclad being able to live in both sulfidic and non-sulfidic waters. Among the fauna of the Mangalia sulfidic ecosystem it is the only species found also outside of the current boundaries of the sulfidic aquifer. One possible explanation of this peculiar distribution is that the new species is limited to the old boundaries of the sulfidic aquifer. The latter became much smaller during the hydrogeological history of the region, so that D. obstinatum may be considered to be an indicator of the extension of the sulfidic aquifer in the past of the Mangalia region. In the context of a biogeographic discussion on the distribution of the genus Dendrocoelum we provide an annotated checklist of species reported from Romania.

Long-term change of meiofaunal species composition in a sandy beach, with description of 7 new species of Platyhelminthes

Climate change and species introductions strongly changed macrobenthic community composition in the North Sea during past decades. To find out whether there was a similar change in meiofauna, I re-examined a semi-exposed sandy beach of the Island of Sylt that had been intensively studied between 1965 and 1975. These previous studies provide the baseline for temporal change. As before, the analysis of species composition focused on Platyhelminthes. Minor change in the physical properties of the beach during the past decades was compensated for by including two adjoining beaches, one slightly more sheltered and the other slightly more exposed. In due consideration of somewhat differing sample size, platyhelminth species richness barely changed over the past 50 years, and the numerical dominant species were still the same. However, roughly 10% of the 220 species found during this study were not previously recorded from the Island of Sylt. Thirteen are new to science though unpublished records indicate that half of them already occurred previously. Seven species described from elsewhere were recorded for the first time in the Sylt area. Based on their known geographical range, none of these can be unambiguously assigned an immigrant or introduced species. I conclude that (1) the platyhelminth fauna displayed high temporal stability over the past 50 years, and (2) though this beach is among the best studied in the world, a rate of 10% new species indicates our knowledge on the diverse meiofauna is still relatively poor. Seven new species of Platyhelminthes are described and three re-described: Coelogynopora multispina n. sp., Pseudostomum gracilis Westblad 1955, Nesite ptychoperoides n. gen. n. sp., Haplovejdovskya scilliensis Faubel & Warwick 2005, Haloplanella magnarhabdita n. sp., Haloplanella spiralis n. sp., Moevenbergia oculifagi n. sp., Coronhelmis inaequalis n. sp., Proxenetes inflatus den Hartog 1966, and Diascorhynchus falconis n. sp.

Updated inventory and distribution of free-living flatworms from Tunisian waters.

Records of free-living flatworms (turbellarians) from Tunisian waters are scattered. Based on new material and published accounts, an annotated checklist of free-living flatworm species from Tunisian waters is provided. A total of 29 species is recorded, including 18 species with new material and 11 species only from literature records. For each species, information on systematics, habitats and distribution is supplied, together with taxonomic or biological remarks. Three species, the acotylean polyclads Cestoplana rubrocinta Lang, 1884 and Comoplana agilis (Lang, 1884) as well as the marine triclad Cercyra hastata Schmidt, 1861 are recorded for the first time in Tunisia. The controversial occurrence of the leptoplanid polyclad Leptoplana tremellaris in the Mediterranean is supported with histological sections and embryological data. The proseriate Monocelis fusca Örsted, 1843 previously reported from Tunisia is considered to be a misidentification.By presenting a checklist of the recorded species, this work summarizes our current knowledge of the turbellarian fauna diversity in Tunisia, providing baseline data for future biogeographical, ecological, behavioral and evolutionary investigations.

Kalyptorhynchia (Platyhelminthes: Rhabdocoela) from KwaZulu-Natal (South Africa), with the description of six new species.

Fifteen species of kalyptorhynch flatworms, twelve of them eukalyptorhynchs and three schizorhynchs, are reported from the KwaZulu-Natal coast in South Africa. Six species are new to science, five of which belong to Eukalyptorhynchia, the remaining one to Schizorhynchia. One of the new eukalyptorhynch species, Uncinorhynchus linusi n. sp., belongs to the taxon Gnathorhynchidae Meixner, 1929 and can be distinguished from other species of Uncinorhynchus Karling, 1947 based on the detailed structure of the proboscis hooks and the hard part in the male genital system. Two other species are members of the Koinocystididae Meixner, 1924. Itaipusa sbui n. sp. is characterised by an armed cirrus with two transversal bands of lamellar spines and by the detailed structure of the female genital system. The other new koinocystidid cannot be placed in any existing taxon and therefore a new genus is erected: Bhambathorhynchus abursalis n. gen. n. sp. It is characterised by the presence of two bent hooks in the male system, each one connected to a muscular bulb, and by the absence of a copulatory bursa. The remaining two new species of Eukalyptorhynchia, Lagenopolycystis mandelai n. sp. and Phonorhynchoides gondwanae n. sp., are members of the taxon Polycystididae Graff, 1905 and can be distinguished from their respective congeners by the detailed structure of their hard parts in the male genital system. The latter species also occurs on the Indian subcontinent. The discussion on the phylogenetic position of the new species of Phonorhynchoides leads to the formal split of this non-monophyletic genus into two taxa: Phonorhynchoides Beklemischev, 1927 and Phonorhynchopsis n. gen. The sixth and last new species, Baltoplana cupressus n. sp., is a member of the taxon Cheliplanidae Schilke, 1970 (Schizorhynchia) and combines an armed cirrus with a single accessory cirrus in the copulatory organ. For two more species, Prognathorhynchus spec. and Carcharodorhynchus spec., the available material is inadequate for a formal description, but they are mentioned and illustrated to allow future recognition. Six known species, Pocillorhynchus spiroductus Schockaert, 1982, Duplacrorhynchus heyleni Artois & Schockaert, 1999, Gyratrix hermaphroditus Ehrenberg, 1831, Paulodora contortoides Artois & Tessens, 2008, P. drepanophora Artois & Tessens, 2008 and Cheliplana pileola Jouk & De Vocht, 1989 are reported from South Africa for the first time and additional remarks on their morphology are given. An additional species, Brachyrhynchoides oosterlyncki (Willems, Reygel & Artois, 2013) Willems, Reygel & Artois, 2013 was recently described from South Africa and India (see Artois et al., 2013b, 2013c), and is mentioned here for the sake of completeness.

Imaging and Management of Abdominal Echinococcosis in Children

The clinical entity of cystic echinococcosis (CE) caused by the most prevalent genus of the flatworm species, Echinococcus granulosus (EG), has a global distribution that impacts children causing significant morbidity and mortality. Childhood echinococcosis manifests distinct clinical patterns of disease that require unique management interventions despite its overlap in imaging features with that of adults. Abdominal hydatidosis in children, as in adults, demonstrates a predilection for the liver even though the lungs are the most commonly affected organ in children. Treatment is almost always surgical in children and the procedure of choice is determined by imaging findings. Clinical evaluation and serological tests are fraught with difficulties hence a reliance on radiological investigation for accurate diagnosis, cyst characterization, detection of multiplicity of disease and the early diagnosis of complications. Appropriate radiation safe imaging and up to date management regimes are addressed in this review.

Obligate planktotrophy in the Götte’s larva of Stylochus ellipticus (Platyhelminthes)

Polyclad flatworms are a diverse and emerging model system for developmental biologists, yet development remains poorly understood for many species. One limitation of polyclads as a model system has been the lack of reliable methods for culturing planktotrophic polyclad larvae to metamorphosis. There are conflicting statements in the literature about which types of polyclad larvae require food to complete development. We developed simple methods for rearing planktotrophic flatworms to metamorphosis and tested the effects of food type and concentration on their development. The flatworm Stylochus ellipticus develops from small (~65 μm) eggs into an obligately planktotrophic Götte’s larva. In this species, development to metamorphosis requires high concentrations (50,000 cells/ml) of the unicellular alga Rhodomonas lens as a food source. High concentrations of two other algal species (Dunaliella tertiolecta and Isochrysis galbana) were successfully ingested by larvae but failed to result in development to metamorphosis. We provide estimates of larval development times and initial descriptions of late larval and early juvenile forms in S. ellipticus. These data provide an important contrast between larval development in obligate planktotrophs and development in non-feeding species. Other indirect developing flatworm species may also be reared using these methods, allowing broader examination of polyclad developmental patterns than previously possible.

Land flatworms (Platyhelminthes, Geoplanidae) of São Tomé:a first account on their diversity, with the description of five new species.

The present contribution provides the first faunistic and taxonomic account of six species of land flatworm from the island of São Tomé, including five new species of the genus Othelosoma Gray, 1869 and the introduced Bipalium kewense Moseley, 1878. One of the new species represents the first African land flatworm that has specks on its dorsal body surface, instead of stripes or a more or less uniform colouration. At least two of the new species were observed to prey on snails. The study details the fourth record of a sclerotic spermatophore in a species of land flatworm, and discusses the definition and homology of double female genital canals in African and Indian species of the genus Othelosoma.

Three new species of Cratera Carbayo et al., 2013 from Araucaria forests with a key to species of the genus (Platyhelminthes, Continenticola)

Areas of Araucaria moist forest have been considered to constitute hotspots of land flatworm diversity, harbouring a high number of undescribed species. Herein we describe three new species of land flatworms of Cratera Carbayo et al., 2013 occurring in such type of forest in south Brazil. The three species are differentiated from their congeners mainly by their colour pattern, anatomy of the pharynx and prostatic vesicle, and details of the penis papilla and male atrium. An identification key to species of the genus in the Neotropical region is provided.

WormBase ParaSite − a comprehensive resource for helminth genomics

The number of publicly available parasitic worm genome sequences has increased dramatically in the past three years, and research interest in helminth functional genomics is now quickly gathering pace in response to the foundation that has been laid by these collective efforts. A systematic approach to the organisation, curation, analysis and presentation of these data is clearly vital for maximising the utility of these data to researchers. We have developed a portal called WormBase ParaSite (http://parasite.wormbase.org) for interrogating helminth genomes on a large scale. Data from over 100 nematode and platyhelminth species are integrated, adding value by way of systematic and consistent functional annotation (e.g. protein domains and Gene Ontology terms), gene expression analysis (e.g. alignment of life-stage specific transcriptome data sets), and comparative analysis (e.g. orthologues and paralogues). We provide several ways of exploring the data, including genome browsers, genome and gene summary pages, text search, sequence search, a query wizard, bulk downloads, and programmatic interfaces. In this review, we provide an overview of the back-end infrastructure and analysis behind WormBase ParaSite, and the displays and tools available to users for interrogating helminth genomic data.

SmedOB1 is Required for Planarian Homeostasis and Regeneration.

The planarian flatworm is an emerging model that is useful for studying homeostasis and regeneration due to its unique adult stem cells (ASCs). Previously, planaria were found to share mammalian TTAGGG chromosome ends and telomerases; however, their telomere protection proteins have not yet been identified. In Schmidtea mediterranea, we identified a homologue of the human protection of telomeres 1 (POT1) with an OB-fold (SmedOB1). SmedOB1 is evolutionarily conserved among species and is ubiquitously expressed throughout the whole body. Feeding with SmedOB1 double-stranded RNAs (dsRNAs) led to homeostasis abnormalities in the head and pharynx. Furthermore, several ASC progeny markers were downregulated, and regeneration was impaired. Here we found that SmedOB1 is required for telomeric DNA-protein complex formation and it associates with the telomere TTAGGG sequence in vitro. Moreover, DNA damage and apoptosis signals in planarian were significantly affected by SmedOB1 RNAi. We also confirmed these phenotypes in Dugesia japonica, another flatworm species. Our work identified a novel telomere-associated protein SmedOB1 in planarian, which is required for planarian homeostasis and regeneration. The phylogenetic and functional conservations of SmedOB1 provide one mechanism by which planarians maintain telomere and genome stability to ensure their immortality and shed light on the regeneration medicine of humans.

Effects of flatworm predators on sediment communities and ecosystem functions: a microcosm approach

Predators affect prey and non-prey communities through consumptive effects (CE) and non-consumptive effects (NCE), with consequences for ecosystem functions. Aquatic sediments are entanglements of particles that house diverse communities of microbes and invertebrates involved in ecosystem functions. In this study, we used experimental sediment cores as microcosms to explore the effects of two predatory flatworm species: Polycelis tenuis and Planaria torva. Flatworms secrete mucus for locomotion. Their motility results in particle displacement, which in turn increases the local availability of labile compounds. In this study we asked: (1) How do predators affect biomass allocation in a comprehensive community? (2) What is the impact of these effects on ecosystem functions? Our results showed that flatworms increased the sediment reworking rate and affected the packaging of biomass in prey (e.g., oligochaetes) and non-prey (e.g., protozoa) organisms through both CE and NCE. Causal links between community structure and ecosystem functions suggested different pathways of predator control: Polycelis indirectly influenced P availability, which increased the biomass of bacteria and protozoa, whereas Planaria elicited a trophic cascade and had a wider ranging diet than Polycelis. Our results support the use of flatworms as models to link the functions of organisms with those of ecosystems.

Non‐destructive imaging to describe a new species of Obama land planarian (Platyhelminthes, Tricladida)

The land planarians in the genus Obama include the largest species of the Neotropical Geoplaninae. Morphological discrimination of Obama species can be difficult, as many species are morphologically similar and some present asymmetric – difficult to interpret – copulatory organs. New techniques are thus welcomed to provide faster species description and identification. Here, we study several specimens of Obama by means of mainly 2D and 3D μCT‐based images obtained through X‐ray microcomputed tomography (μCT) of a paratype, and, complementarily, histological sections of the holotype and a second paratype, which were digitized into virtual slides. Comparison of these images with traditional histological sections and descriptions of the known species of the genus allows us to conclude that our specimens constitute a new species, which we describe here. We further evaluate the phylogenetic placement of the new species using gene fragments from the mitochondrial cytochrome c oxidase subunit I and the nuclear elongation factor‐1α. Raw and derivative μCT data and virtual histological sections were deposited in an open repository (GigaDB) and are freely available. This work leads us to conclude that μCT constitutes a relatively fast, inexpensive non‐destructive method that produces results comparable to those of traditional histology, and is thus amenable for describing flatworm species.

Chromosome numbers in three species groups of freshwater flatworms increase with increasing latitude.

Polyploidy in combination with parthenogenesis offers advantages for plasticity and the evolution of a broad ecological tolerance of species. Therefore, a positive correlation between the level of ploidy and increasing latitude as a surrogate for environmental harshness has been suggested. Such a positive correlation is well documented for plants, but examples for animals are still rare. Species of flatworms (Platyhelminthes) are widely distributed, show a remarkably wide range of chromosome numbers, and offer therefore good model systems to study the geographical distribution of chromosome numbers. We analyzed published data on counts of chromosome numbers and geographical information of three flatworm "species" (Phagocata vitta, Polycelis felina and Crenobia alpina) sampled across Europe (220 populations). We used the mean chromosome number across individuals of a population as a proxy for the level of ploidy within populations, and we tested for relationships of this variable with latitude, mode of reproduction (sexual, asexual or both) and environmental variables (annual mean temperature, mean diurnal temperature range, mean precipitation and net primary production). The mean chromosome numbers of all three species increased with latitude and decreased with mean annual temperature. For two species, chromosome number also decreased with mean precipitation and net primary production. Furthermore, high chromosome numbers within species were accompanied with a loss of sexual reproduction. The variation of chromosome numbers within individuals of two of the three species increased with latitude. Our results support the hypothesis that polyploid lineages are able to cope with harsh climatic conditions at high latitudes. Furthermore, we propose that asexual reproduction in populations with high levels of polyploidization stabilizes hybridization events. Chromosomal irregularities within individuals tend to become more frequent at the extreme environments of high latitudes, presumably because of mitotic errors and downsizing of the genome.

First records of polyclads (Platyhelminthes, Polycladida) associated with Nodipecten nodosus (Linnaeus 1758) aquaculture

Free-living marine Platyhelminthes of the order Polycladida are known to interact with molluscs, especially bivalves. The impact and damage of polyclads that feed on farmed oysters can be so significant that they are known as oyster leeches. The present contribution identifies three species of polyclads associated with scallop aquaculture at Ilha Grande, southeastern Brazil: one cotylean, Lurymare matarazzoi, and two acotyleans, Imogine tica and Imogine refertus. This is the first time these species are illustrated with photographs of live specimens and histological sections after their original description. This is also the first record of an association of polyclads with a pectinid mollusc. The ecological role of polyclads is still little known, and experiments are lacking. However, it shows that native flatworm species are interacting with Nodipecten nodosus in experimental aquaculture, feeding either on the molluscs or on the associated fauna.

Current State of Knowledge on Invasive and Alien Fauna of Nepal

This study produced a comprehensive list of introduced fauna of Nepal. Of the sixty four species of alien fauna reported, there were seven species of mammals with forty improved breeds of cow, buffalo, goat, sheep and pig, six species of birds with eight breeds of chicken and duck, nineteen species of fish, twenty two species of arthropods including one species of freshwater prawn and twenty one species of insects, nine species of molluscs and one species of platyhelminths. Among reported alien species Achatina fulica, Capra hircus, Clarius batrachus, Cyprinus carpio, Gambusia affinis, Oncorynchus mykiss, Oreochromis mossambicus, Oryctolagus cuniculus, Platydemus manokwari, and Sus scrofa are considered the worst species of the world and listed in ‘100 of the World’s Worst Invasive Alien Species’. The impacts of all these serious animals in Nepal are still to be studied but some problematic species of agricultural pests, freshwater habitat as well as livestock breeds are discussed in this paper.Journal of Institute of Science and Technology, 2015, 20(1): 68-81

Scrunching: a novel escape gait in planarians

The ability to escape a predator or other life-threatening situations is central to animal survival. Different species have evolved unique strategies under anatomical and environmental constraints. In this study, we describe a novel musculature-driven escape gait in planarians, ‘scrunching’, which is quantitatively different from other planarian gaits, such as gliding and peristalsis. We show that scrunching is a conserved gait among different flatworm species, underlying its importance as an escape mechanism. We further demonstrate that it can be induced by a variety of physical stimuli, including amputation, high temperature, electric shock and low pH. We discuss the functional basis for scrunching as the preferential gait when gliding is impaired due to a disruption of mucus production. Finally, we show that the key mechanical features of scrunching are adequately captured by a simple biomechanical model that is solely based on experimental data from traction force microscopy and tissue rheology without fit parameters. Together, our results form a complete description of this novel form of planarian locomotion. Because scrunching has distinct dynamics, this gait can serve as a robust behavioral readout for studies of motor neuron and muscular functions in planarians and in particular the restoration of these functions during regeneration.