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Kate A Rawlinson - One of the best experts on this subject based on the ideXlab platform.
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evidence for transposable element control by argonautes in a parasitic Flatworm lacking the pirna pathway
bioRxiv, 2020Co-Authors: Anna V Protasio, Kate A Rawlinson, Eric A Miska, Matthew Berriman, Gabriel RinaldiAbstract:Transposable elements (TEs) are mobile parts of the genome that can jump or self-replicate, posing a threat to the stability and integrity of the host genome. TEs are prevented from causing damage to the host genome by defense mechanisms such as nuclear silencing, where TE transcripts are targeted for degradation in an RNAi-like fashion. These pathways are well characterised in model organisms but very little is known about them in other species. Parasitic Flatworms present an opportunity to investigate evolutionary novelties in TE control because they lack canonical pathways identified in model organisms (such as the piRNA pathways) but have conserved central players such as Dicer and Ago (argonaute) enzymes. Notably, parasitic Flatworm Agos are phylogenetically distinct from classical Agos, raising the question of whether they play special roles in these organisms. In this report, we investigate the role of Ago proteins in the parasitic Flatworm Schistosoma mansoni. We show that transcript abundance of two retrotransposable elements increases upon silencing of S.mansoni Ago genes. We further demonstrate that SmAgo2 protein is primarily localised in the germ line of adult worms and its sub-cellular localisation is both nuclear and cytoplasmic. These findings provide further evidence of active TE control under a yet not fully unveiled pathway.
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extraocular rod like photoreceptors in a Flatworm express xenopsin photopigment
eLife, 2019Co-Authors: Kate A Rawlinson, Francois Lapraz, Mark Terasaki, Edward R Ballister, Richard J Mcdowell, Jessica Rodgers, Johannes GirstmairAbstract:Eyes are elaborate organs that many animals use to detect light and see, but light can also be sensed in other, simpler ways and for purposes other than seeing. All animals that perceive light rely on cells called photoreceptors, which come in two main types: ciliary or rhabdomeric. Sometimes, an organism has both types of photoreceptors, but one is typically more important than the other. For example, most vertebrates see using ciliary photoreceptors, while rhabdomeric photoreceptors underpin vision in invertebrates. Flatworms are invertebrates that have long been studied due to their ability to regenerate following injuries. These worms have rhabdomeric photoreceptors in their eyes, but they also have unusual cells outside their eyes that have cilia – slender protuberances from the cell body - and could potentially be light sensitive. One obvious way to test if a cell is a photoreceptor is to see if it produces any light-sensing proteins, such as opsins. Until recently it was thought that each type of photoreceptor produced a different opsin, which were therefore classified into rhabdomeric of ciliary opsins. However, recent work has identified a new type of opsin, called xenopsin, in the ciliary photoreceptors of the larvae of some marine invertebrates. To determine whether the cells outside the Flatworm’s eye were ciliary photoreceptors, Rawlinson et al. examined the genetic code of 30 Flatworm species looking for ciliary opsin and xenopsin genes. This search revealed that all the Flatworm species studied contained the genetic sequence for xenopsin, but not for the ciliary opsin. Rawlinson et al. chose the tiger Flatworm to perform further experiments. First, they showed that, in this species, xenopsin genes are active both in the eyes of larvae and in the unusual ciliary cells found outside the eyes of the adult. Next, they put the xenopsin from the tiger Flatworm into human embryonic kidney cells, and found that when the protein is present these cells can respond to light. This demonstrates that the newly discovered xenopsin is light-sensitive, suggesting that the unusual ciliary cells found expressing this protein outside the eyes in Flatworms are likely photoreceptive cells. It is unclear why Flatworms have developed these unusual ciliary photoreceptor cells or what their purpose is outside the eye. Often, photoreceptor cells outside the eyes are used to align the ‘body clock’ with the day-night cycle. This can be a factor in healing, hinting perhaps that these newly found cells may have a role in Flatworms’ ability to regenerate.
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the life cycle of the acropora coral eating Flatworm aefw prosthiostomum acroporae the influence of temperature and management guidelines
Frontiers in Marine Science, 2019Co-Authors: Kate A Rawlinson, David G Bourne, Jonathan A Barton, Kate S Hutson, Craig Humphrey, Cat DybalaAbstract:As coral aquaculture is increasing around the world for reef restoration and trade, mitigating the impact of coral predators, pathogens and parasites is necessary for optimal growth. The Acropora coral-eating Flatworm (AEFW), Prosthiostomum acroporae (Platyhelminthes: Polycladida: Prosthiostomidae) feeds on wild and cultivated Acropora species and its inadvertent introduction into reef tanks can lead to the rapid death of coral colonies. To guide the treatment of infested corals we investigated the Flatworm’s life cycle parameters at a range of temperatures that represent those found in reef tanks, coral aquaculture facilities and seasonal fluctuations in the wild. We utilized P. acroporae from a long-term in vivo culture on Acropora species to examine the effects of temperature (3°C increments from 21-30°C) on Flatworm embryonation period, hatching success, hatchling longevity, and time to sexual maturity. Our findings show that warmer seawater shortened generation times; at 27°C it took, on average, 11 days for eggs to hatch, and 35 days for Flatworms to reach sexual maturity, giving a minimum generation time of 38 days, whereas at 24°C the generation time was 64 days. Warmer seawater (24–30°C) also increased egg hatching success compared to cooler conditions (21°C). Taken together these results indicate that warmer temperatures lead to higher population densities of P. acroporae. Temperature significantly increased the growth rate of P. acroporae, with individuals reaching a larger size at sexual maturity in warmer temperatures, but it did not influence hatchling longevity. Hatchlings, which can swim as well as crawl, can survive between 0.25 to 9 days in the absence of Acropora, and could therefore disperse between coral colonies and inter-connected aquaria. We used our data to predict embryonation duration and time to sexual maturity at 21°C-30°C, and discuss how to optimise current treatments to disrupt the Flatworm’s life cycle in captivity.
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A Transcriptomic-Phylogenomic Analysis of the Evolutionary Relationships of Flatworms
Current biology : CB, 2015Co-Authors: Bernhard Egger, Kate A Rawlinson, Francois Lapraz, Johannes Girstmair, Bartłomiej Tomiczek, Steven Müller, Christophe Dessimoz, Nives Škunca, Christopher B. Cameron, Elena BeliAbstract:The interrelationships of the Flatworms (phylum Platyhelminthes) are poorly resolved despite decades of morphological and molecular phylogenetic studies [1, 2]. The earliest-branching clades (Catenulida, Macrostomorpha, and Polycladida) share spiral cleavage and entolecithal eggs with other lophotrochozoans. Lecithoepitheliata have primitive spiral cleavage but derived ectolecithal eggs. Other orders (Rhabdocoela, Proseriata, Tricladida and relatives, and Bothrioplanida) all have derived ectolecithal eggs but have uncertain affinities to one another. The orders of parasitic Neodermata emerge from an uncertain position from within these ectolecithal classes. To tackle these problems, we have sequenced transcriptomes from 18 Flatworms and 5 other metazoan groups. The addition of published data produces an alignment of >107,000 amino acids with less than 28% missing data from 27 Flatworm taxa in 11 orders covering all major clades. Our phylogenetic analyses show that Platyhelminthes consist of the two clades Catenulida and Rhabditophora. Within Rhabditophora, we show the earliest-emerging branch is Macrostomorpha, not Polycladida. We show Lecithoepitheliata are not members of Neoophora but are sister group of Polycladida, implying independent origins of the ectolecithal eggs found in Lecithoepitheliata and Neoophora. We resolve Rhabdocoela as the most basally branching euneoophoran taxon. Tricladida, Bothrioplanida, and Neodermata constitute a group that appears to have lost both spiral cleavage and centrosomes. We identify Bothrioplanida as the long-sought closest free-living sister group of the parasitic Neodermata. Among parasitic orders, we show that Cestoda are closer to Trematoda than to Monogenea, rejecting the concept of the Cercomeromorpha. Our results have important implications for understanding the evolution of this major phylum.
Johannes Girstmair - One of the best experts on this subject based on the ideXlab platform.
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extraocular rod like photoreceptors in a Flatworm express xenopsin photopigment
eLife, 2019Co-Authors: Kate A Rawlinson, Francois Lapraz, Mark Terasaki, Edward R Ballister, Richard J Mcdowell, Jessica Rodgers, Johannes GirstmairAbstract:Eyes are elaborate organs that many animals use to detect light and see, but light can also be sensed in other, simpler ways and for purposes other than seeing. All animals that perceive light rely on cells called photoreceptors, which come in two main types: ciliary or rhabdomeric. Sometimes, an organism has both types of photoreceptors, but one is typically more important than the other. For example, most vertebrates see using ciliary photoreceptors, while rhabdomeric photoreceptors underpin vision in invertebrates. Flatworms are invertebrates that have long been studied due to their ability to regenerate following injuries. These worms have rhabdomeric photoreceptors in their eyes, but they also have unusual cells outside their eyes that have cilia – slender protuberances from the cell body - and could potentially be light sensitive. One obvious way to test if a cell is a photoreceptor is to see if it produces any light-sensing proteins, such as opsins. Until recently it was thought that each type of photoreceptor produced a different opsin, which were therefore classified into rhabdomeric of ciliary opsins. However, recent work has identified a new type of opsin, called xenopsin, in the ciliary photoreceptors of the larvae of some marine invertebrates. To determine whether the cells outside the Flatworm’s eye were ciliary photoreceptors, Rawlinson et al. examined the genetic code of 30 Flatworm species looking for ciliary opsin and xenopsin genes. This search revealed that all the Flatworm species studied contained the genetic sequence for xenopsin, but not for the ciliary opsin. Rawlinson et al. chose the tiger Flatworm to perform further experiments. First, they showed that, in this species, xenopsin genes are active both in the eyes of larvae and in the unusual ciliary cells found outside the eyes of the adult. Next, they put the xenopsin from the tiger Flatworm into human embryonic kidney cells, and found that when the protein is present these cells can respond to light. This demonstrates that the newly discovered xenopsin is light-sensitive, suggesting that the unusual ciliary cells found expressing this protein outside the eyes in Flatworms are likely photoreceptive cells. It is unclear why Flatworms have developed these unusual ciliary photoreceptor cells or what their purpose is outside the eye. Often, photoreceptor cells outside the eyes are used to align the ‘body clock’ with the day-night cycle. This can be a factor in healing, hinting perhaps that these newly found cells may have a role in Flatworms’ ability to regenerate.
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Reinvestigating the early embryogenesis in the Flatworm Maritigrella crozieri highlights the unique spiral cleavage program found in polyclad Flatworms
EvoDevo, 2019Co-Authors: Johannes Girstmair, Maximilian J TelfordAbstract:Background Spiral cleavage is a conserved, early developmental mode found in several phyla of Lophotrochozoans resulting in highly diverse adult body plans. While the cleavage pattern has clearly been broadly conserved, it has also undergone many modifications in various taxa. The precise mechanisms of how different adaptations have altered the ancestral spiral cleavage pattern are an important ongoing evolutionary question, and adequately answering this question requires obtaining a broad developmental knowledge of different spirally cleaving taxa. In Flatworms (Platyhelminthes), the spiral cleavage program has been lost or severely modified in most taxa. Polyclad Flatworms, however, have retained the pattern up to the 32-cell stage. Here we study early embryogenesis of the cotylean polyclad Flatworm Maritigrella crozieri to investigate how closely this species follows the canonical spiral cleavage pattern and to discover any potential deviations from it. Results Using live imaging recordings and 3D reconstructions of embryos, we give a detailed picture of the events that occur during spiral cleavage in M. crozieri . We suggest, contrary to previous observations, that the four-cell stage is a product of unequal cleavages. We show that that the formation of third and fourth micromere quartets is accompanied by strong blebbing events; blebbing also accompanies the formation of micromere 4d. We find an important deviation from the canonical pattern of cleavages with clear evidence that micromere 4d follows an atypical cleavage pattern, so far exclusively found in polyclad Flatworms. Conclusions Our findings highlight that early development in M. crozieri deviates in several important aspects from the canonical spiral cleavage pattern. We suggest that some of our observations extend to polyclad Flatworms in general as they have been described in both suborders of the Polycladida, the Cotylea and Acotylea.
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studying early embryogenesis in the Flatworm maritigrella crozieri indicates a unique modification of the spiral cleavage program in polyclad Flatworms
bioRxiv, 2019Co-Authors: Johannes Girstmair, Maximilian J TelfordAbstract:Abstract Background Spiral cleavage is a conserved early developmental mode found in several phyla of Lophotrochozoans with highly diverse adult body plans. While the cleavage pattern has clearly been broadly conserved, it has also undergone many modifications in various taxa. The precise mechanisms of how different adaptations have altered the ancestral spiral cleavage pattern is an important ongoing evolutionary question and adequately answering this question requires obtaining a broad developmental knowledge of different spirally cleaving taxa. In Flatworms (Platyhelminthes), the spiral cleavage program has been lost or severely modified in most taxa. Polyclad Flatworms, however, have retained the pattern up to the 32-cell stage. Here we study early embryogenesis of the cotylean polyclad Flatworm Maritigrella crozieri to investigate how closely this species follows the canonical spiral cleavage pattern and to discover any potential deviations from it. Results Using live imaging recordings and 3D reconstructions of embryos, we give a detailed picture of the events that occur during spiral cleavage in M. crozieri. We suggest, contrary to previous observations, that the 4-cell stage is a product of unequal cleavages. We show that that the formation of third and fourth micromere quartets are accompanied by strong blebbing events; blebbing also accompanies the formation of micromere 4d. We find an important deviation from the canonical pattern of cleavages with clear evidence that micromere 4d follows an atypical cleavage pattern, so far exclusively found in polyclad Flatworms. Conclusions Our findings highlight that early development in M. crozieri deviates in several important aspects from the canonical spiral cleavage pattern. We suggest that some of our observations extend to polyclad Flatworms in general as they have been described in both suborders of the Polycladida, the Cotylea and Acotylea.
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A Transcriptomic-Phylogenomic Analysis of the Evolutionary Relationships of Flatworms
Current biology : CB, 2015Co-Authors: Bernhard Egger, Kate A Rawlinson, Francois Lapraz, Johannes Girstmair, Bartłomiej Tomiczek, Steven Müller, Christophe Dessimoz, Nives Škunca, Christopher B. Cameron, Elena BeliAbstract:The interrelationships of the Flatworms (phylum Platyhelminthes) are poorly resolved despite decades of morphological and molecular phylogenetic studies [1, 2]. The earliest-branching clades (Catenulida, Macrostomorpha, and Polycladida) share spiral cleavage and entolecithal eggs with other lophotrochozoans. Lecithoepitheliata have primitive spiral cleavage but derived ectolecithal eggs. Other orders (Rhabdocoela, Proseriata, Tricladida and relatives, and Bothrioplanida) all have derived ectolecithal eggs but have uncertain affinities to one another. The orders of parasitic Neodermata emerge from an uncertain position from within these ectolecithal classes. To tackle these problems, we have sequenced transcriptomes from 18 Flatworms and 5 other metazoan groups. The addition of published data produces an alignment of >107,000 amino acids with less than 28% missing data from 27 Flatworm taxa in 11 orders covering all major clades. Our phylogenetic analyses show that Platyhelminthes consist of the two clades Catenulida and Rhabditophora. Within Rhabditophora, we show the earliest-emerging branch is Macrostomorpha, not Polycladida. We show Lecithoepitheliata are not members of Neoophora but are sister group of Polycladida, implying independent origins of the ectolecithal eggs found in Lecithoepitheliata and Neoophora. We resolve Rhabdocoela as the most basally branching euneoophoran taxon. Tricladida, Bothrioplanida, and Neodermata constitute a group that appears to have lost both spiral cleavage and centrosomes. We identify Bothrioplanida as the long-sought closest free-living sister group of the parasitic Neodermata. Among parasitic orders, we show that Cestoda are closer to Trematoda than to Monogenea, rejecting the concept of the Cercomeromorpha. Our results have important implications for understanding the evolution of this major phylum.
Bernhard Egger - One of the best experts on this subject based on the ideXlab platform.
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Regeneration of the Flatworm Prosthiostomum siphunculus (Polycladida, Platyhelminthes)
Cell and Tissue Research, 2020Co-Authors: Tamara Schadt, Veronika Prantl, Alexandra L Grosbusch, Philip Bertemes, Bernhard EggerAbstract:Fueled by the discovery of head regeneration in triclads (planarians) two and a half centuries ago, Flatworms have been the focus of regeneration research. But not all Flatworms can regenerate equally well and to obtain a better picture of the characteristics and evolution of regeneration in Flatworms other than planarians, the regeneration capacity and stem cell dynamics during regeneration in the Flatworm order Polycladida are studied. Here, we show that as long as the brain remained at least partially intact, the polyclad Prosthiostomum siphunculus was able to regenerate submarginal eyes, cerebral eyes, pharynx, intestine and sucker. In the complete absence of the brain only wound closure was observed but no regeneration of missing organs. Amputated parts of the brain could not be regenerated. The overall regeneration capacity of P. siphunculus is a good fit for category III after a recently established system, in which most polyclads are currently classified. Intact animals showed proliferating cells in front of the brain which is an exception compared with most of the other free-living Flatworms that have been observed so far. Proliferating cells could be found within the regeneration blastema, similar to all other Flatworm taxa except triclads. No proliferation was observed in epidermis and pharynx. In pulse-chase experiments, the chased cells were found in all regenerated tissues and thereby shown to differentiate and migrate to replace the structures lost upon amputation.
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Atp8 is in the ground pattern of Flatworm mitochondrial genomes
BMC Genomics, 2017Co-Authors: Bernhard Egger, Lutz Bachmann, Bastian FrommAbstract:Background To date, mitochondrial genomes of more than one hundred Flatworms (Platyhelminthes) have been sequenced. They show a high degree of similarity and a strong taxonomic bias towards parasitic lineages. The mitochondrial gene atp8 has not been confidently annotated in any Flatworm sequenced to date. However, sampling of free-living Flatworm lineages is incomplete. We addressed this by sequencing the mitochondrial genomes of the two small-bodied (about 1 mm in length) free-living Flatworms Stenostomum sthenum and Macrostomum lignano as the first representatives of the earliest branching Flatworm taxa Catenulida and Macrostomorpha respectively. Results We have used high-throughput DNA and RNA sequence data and PCR to establish the mitochondrial genome sequences and gene orders of S. sthenum and M. lignano . The mitochondrial genome of S. sthenum is 16,944 bp long and includes a 1,884 bp long inverted repeat region containing the complete sequences of nad3 , rrnS, and nine tRNA genes. The model Flatworm M. lignano has the smallest known mitochondrial genome among free-living Flatworms, with a length of 14,193 bp. The mitochondrial genome of M. lignano lacks duplicated genes, however, tandem repeats were detected in a non-coding region. Mitochondrial gene order is poorly conserved in Flatworms, only a single pair of adjacent ribosomal or protein-coding genes – nad4l-nad4 – was found in S. sthenum and M. lignano that also occurs in other published Flatworm mitochondrial genomes. Unexpectedly, we unambiguously identified the full metazoan mitochondrial protein-coding gene complement including atp8 in S. sthenum and M. lignano . A subsequent search detected atp8 in all mitochondrial genomes of polyclad Flatworms published to date, although the gene wasn’t previously annotated in these species. Conclusions Manual, but not automated genome annotation revealed the presence of atp8 in basally branching free-living Flatworms, signifying both the importance of manual data curation and of diverse taxon sampling. We conclude that the loss of atp8 within Flatworms is restricted to the parasitic taxon Neodermata.
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A Transcriptomic-Phylogenomic Analysis of the Evolutionary Relationships of Flatworms
Current biology : CB, 2015Co-Authors: Bernhard Egger, Kate A Rawlinson, Francois Lapraz, Johannes Girstmair, Bartłomiej Tomiczek, Steven Müller, Christophe Dessimoz, Nives Škunca, Christopher B. Cameron, Elena BeliAbstract:The interrelationships of the Flatworms (phylum Platyhelminthes) are poorly resolved despite decades of morphological and molecular phylogenetic studies [1, 2]. The earliest-branching clades (Catenulida, Macrostomorpha, and Polycladida) share spiral cleavage and entolecithal eggs with other lophotrochozoans. Lecithoepitheliata have primitive spiral cleavage but derived ectolecithal eggs. Other orders (Rhabdocoela, Proseriata, Tricladida and relatives, and Bothrioplanida) all have derived ectolecithal eggs but have uncertain affinities to one another. The orders of parasitic Neodermata emerge from an uncertain position from within these ectolecithal classes. To tackle these problems, we have sequenced transcriptomes from 18 Flatworms and 5 other metazoan groups. The addition of published data produces an alignment of >107,000 amino acids with less than 28% missing data from 27 Flatworm taxa in 11 orders covering all major clades. Our phylogenetic analyses show that Platyhelminthes consist of the two clades Catenulida and Rhabditophora. Within Rhabditophora, we show the earliest-emerging branch is Macrostomorpha, not Polycladida. We show Lecithoepitheliata are not members of Neoophora but are sister group of Polycladida, implying independent origins of the ectolecithal eggs found in Lecithoepitheliata and Neoophora. We resolve Rhabdocoela as the most basally branching euneoophoran taxon. Tricladida, Bothrioplanida, and Neodermata constitute a group that appears to have lost both spiral cleavage and centrosomes. We identify Bothrioplanida as the long-sought closest free-living sister group of the parasitic Neodermata. Among parasitic orders, we show that Cestoda are closer to Trematoda than to Monogenea, rejecting the concept of the Cercomeromorpha. Our results have important implications for understanding the evolution of this major phylum.
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Biological adhesion of the Flatworm Macrostomum lignano relies on a duo-gland system and is mediated by a cell type-specific intermediate filament protein
Frontiers in Zoology, 2014Co-Authors: Birgit Lengerer, Lukas Schärer, Julia Wunderer, Robert Pjeta, Marcelo Rodrigues, Roberto Arbore, Eugene Berezikov, Michael W Hess, Kristian Pfaller, Bernhard EggerAbstract:Background Free-living Flatworms, in both marine and freshwater environments, are able to adhere to and release from a substrate several times within a second. This reversible adhesion relies on adhesive organs comprised of three cell types: an adhesive gland cell, a releasing gland cell, and an anchor cell, which is a modified epidermal cell responsible for structural support. However, nothing is currently known about the molecules that are involved in this adhesion process. Results In this study we present the detailed morphology of the adhesive organs of the free-living marine Flatworm Macrostomum lignano . About 130 adhesive organs are located in a horse-shoe-shaped arc along the ventral side of the tail plate. Each organ consists of exactly three cells, an adhesive gland cell, a releasing gland cell, and an anchor cell. The necks of the two gland cells penetrate the anchor cell through a common pore. Modified microvilli of the anchor cell form a collar surrounding the necks of the adhesive- and releasing glands, jointly forming the papilla, the outer visible part of the adhesive organs. Next, we identified an intermediate filament (IF) gene, macif1 , which is expressed in the anchor cells. RNA interference mediated knock-down resulted in the first experimentally induced non-adhesion phenotype in any marine animal. Specifically, the absence of intermediate filaments in the anchor cells led to papillae with open tips, a reduction of the cytoskeleton network, a decline in hemidesmosomal connections, and to shortened microvilli containing less actin. Conclusion Our findings reveal an elaborate biological adhesion system in a free-living Flatworm, which permits impressively rapid temporary adhesion-release performance in the marine environment. We demonstrate that the structural integrity of the supportive cell, the anchor cell, is essential for this adhesion process: the knock-down of the anchor cell-specific intermediate filament gene resulted in the inability of the animals to adhere. The RNAi mediated changes of the anchor cell morphology are comparable to situations observed in human gut epithelia. Therefore, our current findings and future investigations using this powerful Flatworm model system might contribute to a better understanding of the function of intermediate filaments and their associated human diseases.
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Developmental diversity in free-living Flatworms
EvoDevo, 2012Co-Authors: José María Martín-durán, Bernhard EggerAbstract:Flatworm embryology has attracted attention since the early beginnings of comparative evolutionary biology. Considered for a long time the most basal bilaterians, the Platyhelminthes (excluding Acoelomorpha) are now robustly placed within the Spiralia. Despite having lost their relevance to explain the transition from radially to bilaterally symmetrical animals, the study of Flatworm embryology is still of great importance to understand the diversification of bilaterians and of developmental mechanisms. Flatworms are acoelomate organisms generally with a simple centralized nervous system, a blind gut, and lacking a circulatory organ, a skeleton and a respiratory system other than the epidermis. Regeneration and asexual reproduction, based on a totipotent neoblast stem cell system, are broadly present among different groups of Flatworms. While some more basally branching groups - such as polyclad Flatworms - retain the ancestral quartet spiral cleavage pattern, most Flatworms have significantly diverged from this pattern and exhibit unique strategies to specify the common adult body plan. Most free-living Flatworms (i.e. Platyhelminthes excluding the parasitic Neodermata) are directly developing, whereas in polyclads, also indirect developers with an intermediate free-living larval stage and subsequent metamorphosis are found. A comparative study of developmental diversity may help understanding major questions in evolutionary biology, such as the evolution of cleavage patterns, gastrulation and axial specification, the evolution of larval types, and the diversification and specialization of organ systems. In this review, we present a thorough overview of the embryonic development of the different groups of free-living (turbellarian) platyhelminths, including the Catenulida, Macrostomorpha, Polycladida, Lecithoepitheliata, Proseriata, Bothrioplanida, Rhabdocoela, Fecampiida, Prolecithophora and Tricladida, and discuss their main features under a consensus phylogeny of the phylum.
Maximilian J Telford - One of the best experts on this subject based on the ideXlab platform.
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Reinvestigating the early embryogenesis in the Flatworm Maritigrella crozieri highlights the unique spiral cleavage program found in polyclad Flatworms
EvoDevo, 2019Co-Authors: Johannes Girstmair, Maximilian J TelfordAbstract:Background Spiral cleavage is a conserved, early developmental mode found in several phyla of Lophotrochozoans resulting in highly diverse adult body plans. While the cleavage pattern has clearly been broadly conserved, it has also undergone many modifications in various taxa. The precise mechanisms of how different adaptations have altered the ancestral spiral cleavage pattern are an important ongoing evolutionary question, and adequately answering this question requires obtaining a broad developmental knowledge of different spirally cleaving taxa. In Flatworms (Platyhelminthes), the spiral cleavage program has been lost or severely modified in most taxa. Polyclad Flatworms, however, have retained the pattern up to the 32-cell stage. Here we study early embryogenesis of the cotylean polyclad Flatworm Maritigrella crozieri to investigate how closely this species follows the canonical spiral cleavage pattern and to discover any potential deviations from it. Results Using live imaging recordings and 3D reconstructions of embryos, we give a detailed picture of the events that occur during spiral cleavage in M. crozieri . We suggest, contrary to previous observations, that the four-cell stage is a product of unequal cleavages. We show that that the formation of third and fourth micromere quartets is accompanied by strong blebbing events; blebbing also accompanies the formation of micromere 4d. We find an important deviation from the canonical pattern of cleavages with clear evidence that micromere 4d follows an atypical cleavage pattern, so far exclusively found in polyclad Flatworms. Conclusions Our findings highlight that early development in M. crozieri deviates in several important aspects from the canonical spiral cleavage pattern. We suggest that some of our observations extend to polyclad Flatworms in general as they have been described in both suborders of the Polycladida, the Cotylea and Acotylea.
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studying early embryogenesis in the Flatworm maritigrella crozieri indicates a unique modification of the spiral cleavage program in polyclad Flatworms
bioRxiv, 2019Co-Authors: Johannes Girstmair, Maximilian J TelfordAbstract:Abstract Background Spiral cleavage is a conserved early developmental mode found in several phyla of Lophotrochozoans with highly diverse adult body plans. While the cleavage pattern has clearly been broadly conserved, it has also undergone many modifications in various taxa. The precise mechanisms of how different adaptations have altered the ancestral spiral cleavage pattern is an important ongoing evolutionary question and adequately answering this question requires obtaining a broad developmental knowledge of different spirally cleaving taxa. In Flatworms (Platyhelminthes), the spiral cleavage program has been lost or severely modified in most taxa. Polyclad Flatworms, however, have retained the pattern up to the 32-cell stage. Here we study early embryogenesis of the cotylean polyclad Flatworm Maritigrella crozieri to investigate how closely this species follows the canonical spiral cleavage pattern and to discover any potential deviations from it. Results Using live imaging recordings and 3D reconstructions of embryos, we give a detailed picture of the events that occur during spiral cleavage in M. crozieri. We suggest, contrary to previous observations, that the 4-cell stage is a product of unequal cleavages. We show that that the formation of third and fourth micromere quartets are accompanied by strong blebbing events; blebbing also accompanies the formation of micromere 4d. We find an important deviation from the canonical pattern of cleavages with clear evidence that micromere 4d follows an atypical cleavage pattern, so far exclusively found in polyclad Flatworms. Conclusions Our findings highlight that early development in M. crozieri deviates in several important aspects from the canonical spiral cleavage pattern. We suggest that some of our observations extend to polyclad Flatworms in general as they have been described in both suborders of the Polycladida, the Cotylea and Acotylea.
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combined large and small subunit ribosomal rna phylogenies support a basal position of the acoelomorph Flatworms
Proceedings of The Royal Society B: Biological Sciences, 2003Co-Authors: Maximilian J Telford, Anne E Lockyer, C Cartwrightfinch, D T J LittlewoodAbstract:The phylogenetic position of the phylum Platyhelminthes has been re-evaluated in the past decade by analysis of diverse molecular datasets. The consensus is that the Rhabditophora + Catenulida, which includes most of the Flatworm taxa, are not primitively simple basal bilaterians but are related to coelomate phyla such as molluscs. The status of two other groups of acoelomate worms, Acoela and Nemertodermatida, is less clear. Although many characteristics unite these two groups, initial molecular phylogenetic studies placed the Nemertodermatida within the Rhabditophora, but placed the Acoela at the base of the Bilateria, distant from other Flatworms. This contradiction resulted in scepticism about the basal position of acoels and led to calls for further data. We have sequenced large subunit ribosomal RNA genes from 13 rhabditophorans + catenulids, three acoels and one nemertodermatid, tripling the available data. Our analyses strongly support a basal position of both acoels and nemertodermatids. Alternative hypotheses are significantly less well supported by the data. We conclude that the Nemertodermatida and Acoela are basal bilaterians and, owing to their unique body plan and embryogenesis, should be recognized as a separate phylum, the Acoelomorpha.
D T J Littlewood - One of the best experts on this subject based on the ideXlab platform.
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A common origin of complex life cycles in parasitic Flatworms: evidence from the complete mitochondrial genome of Microcotyle sebastis (Monogenea: Platyhelminthes)
BMC Evolutionary Biology, 2007Co-Authors: Joong-ki Park, Kyu-heon Kim, Seokha Kang, Won Kim, Keeseon S Eom, D T J LittlewoodAbstract:Background The parasitic Platyhelminthes (Neodermata) contains three parasitic groups of Flatworms, each having a unique morphology, and life style: Monogenea (primarily ectoparasitic), Trematoda (endoparasitic flukes), and Cestoda (endoparasitic tapeworms). The evolutionary origin of complex life cyles (multiple obligate hosts, as found in Trematoda and Cestoda) and of endo-/ecto-parasitism in these groups is still under debate and these questions can be resolved, only if the phylogenetic position of the Monogenea within the Neodermata clade is correctly estimated. Results To test the interrelationships of the major parasitic Flatworm groups, we estimated the phylogeny of the Neodermata using complete available mitochondrial genome sequences and a newly characterized sequence of a polyopisthocotylean monogenean Microcotyle sebastis . Comparisons of inferred amino acid sequences and gene arrangement patterns with other published Flatworm mtDNAs indicate Monogenea are sister group to a clade of Trematoda+Cestoda. Conclusion Results confirm that vertebrates were the first host for stem group neodermatans and that the addition of a second, invertebrate, host was a single event occurring in the Trematoda+Cestoda lineage. In other words, the move from direct life cycles with one host to complex life cycles with multiple hosts was a single evolutionary event. In association with the evolution of life cycle patterns, our result supports the hypothesis that the most recent common ancestor of the Neodermata giving rise to the Monogenea adopted vertebrate ectoparasitism as its initial life cycle pattern and that the intermediate hosts of the Trematoda (molluscs) and Cestoda (crustaceans) were subsequently added into the endoparasitic life cycles of the Trematoda+Cestoda clade after the common ancestor of these branched off from the monogenean lineage. Complex life cycles, involving one or more intermediate hosts, arose through the addition of intermediate hosts and not the addition of a vertebrate definitive host. Additional evidence is required from monopisthocotylean monogeneans in order to confirm the monophyly of the group.
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a common origin of complex life cycles in parasitic Flatworms evidence from the complete mitochondrial genome of microcotyle sebastis monogenea platyhelminthes
BMC Evolutionary Biology, 2007Co-Authors: Joong-ki Park, Kyu-heon Kim, Seokha Kang, Won Kim, Keeseon S Eom, D T J LittlewoodAbstract:The parasitic Platyhelminthes (Neodermata) contains three parasitic groups of Flatworms, each having a unique morphology, and life style: Monogenea (primarily ectoparasitic), Trematoda (endoparasitic flukes), and Cestoda (endoparasitic tapeworms). The evolutionary origin of complex life cyles (multiple obligate hosts, as found in Trematoda and Cestoda) and of endo-/ecto-parasitism in these groups is still under debate and these questions can be resolved, only if the phylogenetic position of the Monogenea within the Neodermata clade is correctly estimated. To test the interrelationships of the major parasitic Flatworm groups, we estimated the phylogeny of the Neodermata using complete available mitochondrial genome sequences and a newly characterized sequence of a polyopisthocotylean monogenean Microcotyle sebastis. Comparisons of inferred amino acid sequences and gene arrangement patterns with other published Flatworm mtDNAs indicate Monogenea are sister group to a clade of Trematoda+Cestoda. Results confirm that vertebrates were the first host for stem group neodermatans and that the addition of a second, invertebrate, host was a single event occurring in the Trematoda+Cestoda lineage. In other words, the move from direct life cycles with one host to complex life cycles with multiple hosts was a single evolutionary event. In association with the evolution of life cycle patterns, our result supports the hypothesis that the most recent common ancestor of the Neodermata giving rise to the Monogenea adopted vertebrate ectoparasitism as its initial life cycle pattern and that the intermediate hosts of the Trematoda (molluscs) and Cestoda (crustaceans) were subsequently added into the endoparasitic life cycles of the Trematoda+Cestoda clade after the common ancestor of these branched off from the monogenean lineage. Complex life cycles, involving one or more intermediate hosts, arose through the addition of intermediate hosts and not the addition of a vertebrate definitive host. Additional evidence is required from monopisthocotylean monogeneans in order to confirm the monophyly of the group.
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combined large and small subunit ribosomal rna phylogenies support a basal position of the acoelomorph Flatworms
Proceedings of The Royal Society B: Biological Sciences, 2003Co-Authors: Maximilian J Telford, Anne E Lockyer, C Cartwrightfinch, D T J LittlewoodAbstract:The phylogenetic position of the phylum Platyhelminthes has been re-evaluated in the past decade by analysis of diverse molecular datasets. The consensus is that the Rhabditophora + Catenulida, which includes most of the Flatworm taxa, are not primitively simple basal bilaterians but are related to coelomate phyla such as molluscs. The status of two other groups of acoelomate worms, Acoela and Nemertodermatida, is less clear. Although many characteristics unite these two groups, initial molecular phylogenetic studies placed the Nemertodermatida within the Rhabditophora, but placed the Acoela at the base of the Bilateria, distant from other Flatworms. This contradiction resulted in scepticism about the basal position of acoels and led to calls for further data. We have sequenced large subunit ribosomal RNA genes from 13 rhabditophorans + catenulids, three acoels and one nemertodermatid, tripling the available data. Our analyses strongly support a basal position of both acoels and nemertodermatids. Alternative hypotheses are significantly less well supported by the data. We conclude that the Nemertodermatida and Acoela are basal bilaterians and, owing to their unique body plan and embryogenesis, should be recognized as a separate phylum, the Acoelomorpha.