A new higher classification of planarian flatworms (Platyhelminthes, Tricladida)

Ultrastructural analysis and 3D reconstruction of the frontal sensory-glandular complex and its neural projections in the platyhelminth Macrostomum lignano

The marine microturbellarian Macrostomum lignano (Platyhelminthes, Rhabditophora) is an emerging laboratory model used by a growing community of researchers because it is easy to cultivate, has a fully sequenced genome, and offers multiple molecular tools for its study. M. lignano has a compartmentalized brain that receives sensory information from receptors integrated in the epidermis. Receptors of the head, as well as accompanying glands and specialized epidermal cells, form a compound sensory structure called the frontal glandular complex. In this study, we used semi-serial transmission electron microscopy (TEM) to document the types, ultrastructure, and three-dimensional architecture of the cells of the frontal glandular complex. We distinguish a ventral compartment formed by clusters of type 1 (multiciliated) sensory receptors from a central domain where type 2 (collar) sensory receptors predominate. Six different types of glands (rhammite glands, mucoid glands, glands with aster-like and perimaculate granula, vacuolated glands, and buckle glands) are closely associated with type 1 sensory receptors. Endings of a seventh type of gland (rhabdite gland) define a dorsal domain of the frontal glandular complex. A pair of ciliary photoreceptors is closely associated with the base of the frontal glandular complex. Bundles of dendrites, connecting the receptor endings with their cell bodies which are located in the brain, form the (frontal) peripheral nerves. Nerve fibers show a varicose structure, with thick segments alternating with thin segments, and are devoid of a glial layer. This distinguishes platyhelminths from larger and/or more complex invertebrates whose nerves are embedded in prominent glial sheaths.

The invasive land flatworm Arthurdendyus triangulatus has repeated sequences in the mitogenome, extra-long cox2 gene and paralogous nuclear rRNA clusters

Using a combination of short- and long-reads sequencing, we were able to sequence the complete mitochondrial genome of the invasive 'New Zealand flatworm' Arthurdendyus triangulatus (Geoplanidae, Rhynchodeminae, Caenoplanini) and its two complete paralogous nuclear rRNA gene clusters. The mitogenome has a total length of 20,309 bp and contains repetitions that includes two types of tandem-repeats that could not be solved by short-reads sequencing. We also sequenced for the first time the mitogenomes of four species of Caenoplana (Caenoplanini). A maximum likelihood phylogeny associated A. triangulatus with the other Caenoplanini but Parakontikia ventrolineata and Australopacifica atrata were rejected from the Caenoplanini and associated instead with the Rhynchodemini, with Platydemus manokwari. It was found that the mitogenomes of all species of the subfamily Rhynchodeminae share several unusual structural features, including a very long cox2 gene. This is the first time that the complete paralogous rRNA clusters, which differ in length, sequence and seemingly number of copies, were obtained for a Geoplanidae.

Molecular phylogenetics facilitates the first historical biogeographic analysis of the hammerhead worms (Platyhelminthes: Tricladida: Bipaliinae), with the description of twelve new species and two new genera

The hammerhead worms constitute a land planarian subfamily (Platyhelminthes: Tricladida: Bipaliinae) that is popular among natural historians as well as citizen scientists due to their characteristic semi-lunar-shaped head, the striking colours of many species, and the worldwide presence of introduced species, which has raised much concern about their putative impact on the receiving ecosystems. Despite such current awareness, the majority of Bipaliinae species was described before the second half of the 20th century. Over the past few decades, description of new species has been rather scarce. In the present paper, we describe twelve new species and two new genera from Madagascar, Borneo, and Japan, mainly using specimens that form part of the collections of Naturalis Biodiversity Center, Leiden. Species identification has been based on morphology, inner anatomy, and, when available, molecular information. Our molecular phylogenetic tree suggests that either Malagasy or Bornean representatives form the sister-group to the rest of Bipaliinae. The phylogeny suggests also that the Bipaliinae comprises several new and, as yet, undescribed genera. Although the geographical origin of the subfamily is uncertain and may involve either Madagascar or the Bornean region, a molecular time-calibration of the phylogenetic tree indicated that the origin of the Bipaliinae may date back to about 253 Mya, placing its origin near the Permian-Triassic transition and, thus, on Pangea.

An annotated checklist of terrestrial flatworms (Platyhelminthes: Tricladida: Geoplanidae) from Mexico, with new records of invasive species from a citizen science platform and a new nomen dubium

A checklist of species of terrestrial flatworms (Platyhelminthes: Tricladida: Geoplanidae) recorded for Mexico is compiled, listing 11 species. Five are directly referenced in the literature: Bipalium kewense Moseley, 1878, Bipalium vagum Jones & Sterrer, 2005, Diporodemus yucatani Hyman, 1938, Geoplana multipunctata Fuhrmann, 1914, and Pseudogeoplana nigrofusca (Darwin, 1844); and one species had been indirectly mentioned for the country: Parakontikia ventrolineata (Dendy, 1892), which was described from material intercepted in the USA in a shipment of ornamental plants from Mexico. Mexican records from the citizen science platform iNaturalist were reviewed, revealing the presence of five widely distributed invasive species: Caenoplana coerulea Moseley, 1877, recorded in Ciudad de Mexico; Endeavouria septemlineata (Hyman, 1939), recorded in Ciudad de Mexico, Estado de Mexico, Hidalgo, Jalisco, Morelos, and Oaxaca; Dolichoplana carvalhoi Corrêa, 1947, recorded in Jalisco; Dolichoplana striata Moseley, 1877, recorded in Morelos, Nuevo Leon, Quintana Roo, Tamaulipas, and Veracruz; and Rhynchodemus sylvaticus (Leidy, 1851), recorded in Jalisco. The presence of Parakontikia ventrolineata is confirmed for the country, being recorded in Ciudad de Mexico, Estado de Mexico, Hidalgo, Jalisco, Michoacan, Puebla, Queretaro, and Veracruz. The original description of Pseudogeoplana nigrofusca was revisited and compared to subsequent descriptions and keys, noting that the specimens are not conspecific and that the original description is too vague to accurately identify the species, therefore, this taxon is hereby relegated as a nomen dubium. A key for the higher taxa (subfamilies and tribes) of the North American terrestrial flatworms is proposed.

The discovery of new Chilean taxa revolutionizes the systematics of Geoplaninae Neotropical land planarians (Platyhelminthes: Tricladida)

Two subfamilies of land planarians (Geoplanidae) are endemic to the Neotropical region, namely Geoplaninae (with 29 genera and 346 nominal species, most of which are from Brazil) and its sister-group Timyminae, with only two Chilean species. The systematics of these groups through morphology and molecular data (COI and 28S rDNA genes), including nine new Chilean species, is re-assessed in this study. The great morphological diversity of the Chilean species is congruent with the molecular trees and, accordingly, five new genera (Adinoplana, Harana, Myoplana, Sarcoplana and Transandiplana) are proposed, each characterized by putative synapomorphies. Seven new tribes are also erected (Adinoplanini, Gusanini, Haranini, Inakayaliini, Myoplanini, Polycladini and Sarcoplanini), each one monogeneric, except Geoplanini (which includes all genera under the current concept of Geoplaninae plus the Chilean Transandiplana) and Sarcoplanini (with Sarcoplana and the already known Mapuplana, Pichidamas and Wallamapuplana). Re-diagnoses of Geoplaninae, Timymini, Gusana, Inakayalia, Polycladus and Pichidamas are proposed and biogeographic remarks on Transandiplana are provided

Current state of knowledge on freshwater planarians (Platyhelminthes, Tricladida, Dugesiidae) from Chile

The unique geography of Chile encompasses a wide diversity of ecosystems and a rich biodiversity. However, the platyhelminth fauna has been poorly studied. The aim of this work is to compile the historical record of freshwater planarians described for this country. We accessed worldwide databases and published articles to provide a comprehensive review of their discovery history, morphological characteristics and their localities. Freshwater planarians have been collected mainly in central and southern Chile, while in the northern region a single species has been described. The discovery of new species of freshwater triclads has the potential to reveal novel animal models to study regeneration and/or biological adaptations, as some species are suitable for culture in the laboratory. We discuss the many reasons why further research is needed for this animal group, which should include genomic and molecular genetic studies.

Amphibioplanidae: a new branch and family on the phylogenetic tree of the triclad flatworms (Platyhelminthes: Tricladida), represented by a species from Sardinian caves with a remarkable lifestyle

In this study we document the phylogenetic position and the anatomical and ecological characteristics of a new taxon of cave-dwelling triclad flatworms. This species from the Mediterranean island of Sardinia (Italy) forms a separate branch on the phylogenetic tree of the planarians for which we proposed a new genus and placed it in a new family. Molecular analysis reveals a sister-group relationship between this new family, Amphibioplanidae, and the family Dimarcusidae of the suborder Cavernicola, together constituting the sister-group of the suborder Maricola. The new species Amphibioplana onnisi Stocchino & Sluys, sp. nov. is slender and furnished with an epidermis that is abundantly and uniformly provided with cilia and rhabdites. The pharynx presents an oesophageal projection pointing into the pharynx lumen. Ovaries are located far behind the brain. A relatively long common oviduct opens into the diverticulum of the bursal canal. The probursal copulatory bursa is lined with a highly vacuolated, syncytial epithelium. The habitat of this species is formed by groundwater in microcrevices of the epikarst and temporary cave pools, but the animals can survive in a basically terrestrial environment, thus exhibiting an amphibious lifestyle. Some tentative scenarios are discussed for the evolution of the new taxon and for the presence of the new species in three separate caves in Sardinia.

Planarians, a Neglected Component of Biodiversity in Groundwaters

Underground waters are still one of the most important sources of drinking water for the planet. Moreover, the fauna that inhabits these waters is still little known, even if it could be used as an effective bioindicator. Among cave invertebrates, planarians are strongly suited to be used as a study model to understand adaptations and trophic web features. Here, we show a systematic literature review that aims to investigate the studies done so far on groundwater-dwelling planarians. The research was done using Google Scholar and Web of Science databases. Using the key words “Planarian cave” and “Flatworm Cave” we found 2273 papers that our selection reduced to only 48, providing 113 usable observations on 107 different species of planarians from both groundwaters and springs. Among the most interesting results, it emerged that planarians are at the top of the food chain in two thirds of the reported caves, and in both groundwaters and springs they show a high variability of morphological adaptations to subterranean environments. This is a first attempt to review the phylogeny of the groundwater-dwelling planarias, focusing on the online literature. The paucity of information underlines that scarce attention has been dedicated to these animals. Further revisions, including old papers and books, not available online will be necessary.

Seeing the true colours: three new species of Obama (Platyhelminthes:Continenticola) from remnants of Atlantic forest in southern Brazil based on an integrative approach

The genus Obama Carbayo, Álvarez-Presas, Olivares, Marques, Froehlich & Riutort, 2013 currently comprises 41 species, most of them from Brazilian rainforests. This study describes three new species, viz. Obama autumna sp. nov., Obama leticiae sp. nov. and Obama aureolineata sp. nov., from remnants of Mixed Ombrophilous Forest in southern Brazil, based on an integrative approach and analyses their relationships within the genus. Obama autumna and O. aureolineata show distinctive colour patterns, contrasting yellow and black, which is unusual in species of the genus. The three species can be easily distinguished from their congeners by their external features and a combination of anatomical characteristics, such as the pharyngeal shape, shape and arrangement of the prostatic vesicle and anatomy of the penis papilla. The morphological hypotheses are corroborated by three species delimitation methods (ABGD, PTP and GMYC) and by phylogenetic analysis of the cytochrome c oxidase subunit I gene using maximum likelihood estimation and Bayesian inference. Furthermore, our phylogenetic analyses point out that Obama may be subdivided into three main clades, containing a variable number of well supported groups, the relationships of which remain unresolved. Obama autumna belongs to a distinct clade in relation to O. aureolineata and O. leticiae. Obama aureolineata belongs to one of the well supported groups, having a close relationship with O. apeva. Obama autumna may be more closely related to O. anthropophila and O. decidualis and O. leticiae to O. braunsi. However, the low nodal support does not allow the phylogenetic relationships of these species to be clearly established. We discuss morphological knowledge gaps in Obama, as well as issues regarding analyses based on molecular markers, which should be addressed to clarify relationships within the genus. urn:lsid:zoobank.org:pub:9EE7316D-F0BE-49EC-BBFD-5687952D6592

Complete mitogenome of the invasive land flatworm Parakontikia ventrolineata, the second Geoplanidae (Platyhelminthes) to display an unusually long cox2 gene

We sequenced the complete mitogenome of the invasive flatworm Parakontikia ventrolineata (Platyhelminthes, order Tricladida, family Geoplanidae). The genome is 17,210 bp long, and displays common unusual characteristics shared with Platydemus manokwari, such as its colinearity, an overlap between ND4L and ND4 genes and an unusually long cox2 genes. Both Parakontikia and Platydemus are members of the subfamily Rhynchodeminae and their close relationships are supported by the maximum likelihood phylogeny inferred from the protein-coding genes.

Phylogeny and biogeography of the Cavernicola (Platyhelminthes: Tricladida): Relicts of an epigean group sheltering in caves?

The planarian suborder Cavernicola Sluys, 1990 was originally created to house five species of triclad flatworms with special morphological features and a surprisingly discontinuous and broad geographic distribution. These five species could not be accommodated with any degree of certainty in any of the three taxonomic groups existing at that moment, viz., Paludicola Hallez, 1892, Terricola Hallez, 1892, and Maricola Hallez, 1892. The scarce representation of the group and the peculiarities of the morphological features of the species, including several described more recently, have complicated new tests of the monophyly of the Cavernicola, the assessment of its taxonomic status, as well as the resolution of its internal relationships. Here we present the first molecular study including all genera currently known for the group, excepting one. We analysed newly generated 18S and 28S rDNA data for these species, together with a broad representation of other triclad flatworms. The resulting phylogenetic trees supported the monophyly of the Cavernicola, as well as its sister-group relationship to the Maricola. The sister-group relationship to the Maricola and affinities within the Cavernicola falsify the morphology-based phylogeny of the latter that was proposed previously. The relatively high diversity of some cavernicolan genera suggests that the presumed rarity of the group actually may in part be due to a collecting artefact. Ancestral state reconstruction analyses suggest that the ancestral habitat of the group concerned epigean freshwater conditions. Our results point to an evolutionary scenario in which the Cavernicola (a) originated in a freshwater habitat, (b) as the sister clade of the marine triclads, and (c) subsequently radiated and colonized both epigean and hypogean environments. Competition with other planarians, notably members of the Continenticola, or changes in epigean habitat conditions are two possible explanations -still to be tested- for the loss of most epigean diversity of the Cavernicola, which is currently reflected in their highly disjunct distributions.

The evolutionary terrestrialization of planarian flatworms (Platyhelminthes, Tricladida, Geoplanidae): a review and research programme

The terrestrialization of animal life from aquatic ancestors is a key transition during the history of life. Planarian flatworms form an ideal group of model organisms to study this colonization of the land because they have freshwater, marine, and terrestrial representatives. The widespread occurrence of terrestrial flatworms is a testament to their remarkable success occupying a new niche on land. This lineage of terrestrial worms provides a unique glimpse of an evolutionary pathway by which a group of early divergent aquatic, invertebrate metazoans has moved onto land. Land flatworms are among the first groups of animals to have evolved terrestrial adaptations and to have extensively radiated. Study of this terrestrialization process and the anatomical key innovations facilitating their colonization of the land will contribute greatly to our understanding of this important step in Metazoan history. The context and scientific background are reviewed regarding the evolutionary terrestrialization of land flatworms. Furthermore, a framework of a research programme is sketched, which has as its main objective to test hypotheses on the evolution of land planarians, specifically whether particular anatomical and physiological key innovations have contributed to their evolutionary successful terrestrial colonization and radiation. In this context special attention is paid to the respiration in aquatic and terrestrial planarians. The research programme depends on a comprehensive phylogenetic analysis of all major taxa of the land flatworms on the basis of both molecular and anatomical data. The data sets should be analyzed phylogenetically with a suite of phylogenetic inference methods. Building on such robust reconstructions, it will be possible to study associations between key innovations and the evolutionary terrestrialization process.

Even worms matter: cave habitat restoration for a planarian species increased environmental suitability but not abundance

Invertebrates living in underground environments often have unusual and sometimes unique adaptations and occupy narrow ranges, but there is a lack of knowledge about most micro-endemic cave-dwelling invertebrate species. An illustrative case is that of the flatworm Dendrocoelum italicum, the first survey of which was performed 79 years after its description. The survey revealed that the underground stream supplying water to the pool from which the species was first described had been diverted into a pipe for human use, thus severely reducing the available habitat for the species. Here we describe the results of what we believe is the first habitat restoration action performed in a cave habitat for the conservation of a flatworm. The water-diverting structure was removed, with the involvement of local protected area administrators, citizens and volunteers from local organizations. The intervention resulted in the restoration of a large, stable pool inside the cave, thus creating an optimal habitat for this threatened planarian, with increased availability of prey and a stable population. This report of habitat restoration for a neglected invertebrate offers insights for the protection of other micro-endemic species.

New molecular sequences for two genera of marine planarians facilitate determination of their position in the phylogenetic tree, with new records for two species (Platyhelminthes, Tricladida, Maricola)

For the first time, molecular sequences of the 18S ribosomal DNA were generated for representatives of the genera Obrimoposthia Sluys & Ball, 1989 and Paucumara Sluys, 1989 of the suborder of the marine triclads, or Maricola, by analyzing the species Obrimoposthiawandeli (Hallez, 1906) and Paucumaratrigonocephala (Ijima & Kaburaki, 1916). On the basis of this molecular data the phylogenetic position of these two genera in the phylogenetic tree of the Maricola was determined and compared with their position in the phylogeny based on the analysis of anatomical features. New records for these two species are documented and their taxonomic status is determined on the basis of histological studies.

New molecular sequences for two genera of marine planarians facilitate determination of their position in the phylogenetic tree, with new records for two species (Platyhelminthes, Tricladida, Maricola)

For the first time, molecular sequences of the 18S ribosomal DNA were generated for representatives of the genera Obrimoposthia Sluys & Ball, 1989 and Paucumara Sluys, 1989 of the suborder of the marine triclads, or Maricola, by analyzing the species Obrimoposthiawandeli (Hallez, 1906) and Paucumaratrigonocephala (Ijima & Kaburaki, 1916). On the basis of this molecular data the phylogenetic position of these two genera in the phylogenetic tree of the Maricola was determined and compared with their position in the phylogeny based on the analysis of anatomical features. New records for these two species are documented and their taxonomic status is determined on the basis of histological studies.

An integrative taxonomic approach reveals the first marine triclad (Platyhelminthes) trapped in a cave from a semiarid Neotropical environment

A new genus and species of the suborder Maricola, representing the first marine triclad living in freshwater within a cave, is described. These flatworms show specialised features, such as a lack of pigmentation and eyes, indicating their troglobitic condition. Until now, cave-dwelling triclads have only been found as representatives of the other two triclad lineages. The phylogenetic trees based on 18S rRNA and 28S rRNA genes showed their sequences to form a clade situated in a rather derived position within the Maricola. Combining maximum likelihood and Bayesian analyses along with morphological studies, we undertake the first integrative description of a marine triclad. The new genus is characterised by a secondary copulatory bursa and ovaries located behind the root of the pharynx. Nevertheless, its assignment to a family of Maricola was a difficult task especially due to the paucity of unique defining morphological features of their families. The new species is found in a semiarid environment that suffered marine transgressions and regressions during the Cretaceous, which may explain the presence of this originally marine species in a freshwater cave. The restricted distribution of the new species and recent environmental conditions detected at its type locality raise major concern for its conservation.

Planarian Diversity and Phylogeny

Hundreds of planarian species exist worldwide, representing a rich phenotypic diversity. This chapter presents an overview of the morphology and anatomy of various taxonomic groups of planarian flatworms, focusing on features enabling recognition and identification of the animals. The most recent view on the phylogenetic relationships of the planarians is presented, together with geographic distribution patterns of major groups of triclads. The chapter concludes with a brief methodological section outlining species identification on basis of anatomical features. In conjunction with the established laboratory model species, the phenotypic diversity of planarians provides rich opportunities for comparative studies, which this chapter aims to inspire.

Putrescine independent wound response phenotype is produced by ODC-like RNAi in planarians

Despite increasing evidence indicates polyamines as a convergence point for signaling pathways, including cell growth and differentiation, a unifying concept to interpret their role is still missing. The activity of ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is tightly regulated by a complex molecular machinery, and the demonstration of the existence of multiple ODC paralogs, lacking decarboxylation activity, suggests additional layers of complexity to the intricate ODC regulatory pathway. Because of their extraordinary regenerative abilities and abundance of stem cells, planarians have potential to contribute to our understanding of polyamine function in an in vivo context. We undertook a study on ODC function in planarians and we found six planarian ODCs (ODC1-6). Five out of six ODC homologs carry substitutions of key aminoacids for enzymatic activity, which makes them theoretically unable to decarboxylate ornithine. Silencing of ODC5 and 6 produced a complex phenotype, by prompting animals to an aberrant response, following chronic injury without tissue removal. Phenotype is neither rescued by putrescine, nor mimicked by difluoromethylornithine treatment. Moreover, the co-silencing of other genes of the ODC regulatory pathway did not modulate phenotype outcome or severity, thus suggesting that the function/s of these ODC-like proteins might be unrelated to decarboxylase activity and putrescine production.

Girardia dorotocephala transcriptome sequence, assembly, and validation through characterization of piwi homologs and stem cell progeny markers

Planarian flatworms are popular models for the study of regeneration and stem cell biology in vivo. Technical advances and increased availability of genetic information have fueled the discovery of molecules responsible for stem cell pluripotency and regeneration in flatworms. Unfortunately, most of the planarian research performed worldwide utilizes species that are not natural habitants of North America, which limits their availability to newcomer laboratories and impedes their distribution for educational activities. In order to circumvent these limitations and increase the genetic information available for comparative studies, we sequenced the transcriptome of Girardia dorotocephala, a planarian species pandemic and commercially available in North America. A total of 254,802,670 paired sequence reads were obtained from RNA extracted from intact individuals, regenerating fragments, as well as freshly excised auricles of a clonal line of G. dorotocephala (MA-C2), and used for de novo assembly of its transcriptome. The resulting transcriptome draft was validated through functional analysis of genetic markers of stem cells and their progeny in G. dorotocephala. Akin to orthologs in other planarian species, G. dorotocephala Piwi1 (GdPiwi1) was found to be a robust marker of the planarian stem cell population and GdPiwi2 an essential component for stem cell-driven regeneration. Identification of G. dorotocephala homologs of the early stem cell descendent marker PROG-1 revealed a family of lysine-rich proteins expressed during epithelial cell differentiation. Sequences from the MA-C2 transcriptome were found to be 98-99% identical to nucleotide sequences from G. dorotocephala populations with different chromosomal number, demonstrating strong conservation regardless of karyotype evolution. Altogether, this work establishes G. dorotocephala as a viable and accessible option for analysis of gene function in North America.

Application of Computational Methods in Planaria Research: A Current Update

Planaria is a member of the Phylum Platyhelminthes including flatworms. Planarians possess the unique ability of regeneration from adult stem cells or neoblasts and finds importance as a model organism for regeneration and developmental studies. Although research is being actively carried out globally through conventional methods to understand the process of regeneration from neoblasts, biology of development, neurobiology and immunology of Planaria, there are many thought provoking questions related to stem cell plasticity, and uniqueness of regenerative potential in Planarians amongst other members of Phylum Platyhelminthes. The complexity of receptors and signalling mechanisms, immune system network, biology of repair, responses to injury are yet to be understood in Planaria. Genomic and transcriptomic studies have generated a vast repository of data, but their availability and analysis is a challenging task. Data mining, computational approaches of gene curation, bioinformatics tools for analysis of transcriptomic data, designing of databases, application of algorithms in deciphering changes of morphology by RNA interference (RNAi) approaches, understanding regeneration experiments is a new venture in Planaria research that is helping researchers across the globe in understanding the biology. We highlight the applications of Hidden Markov models (HMMs) in designing of computational tools and their applications in Planaria decoding their complex biology.

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 CrateraCarbayo 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.

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.

A new genus and species for the first recorded cave-dwelling Cavernicola (Platyhelminthes) from South America

Species diversity of Brazilian cave fauna has been seriously underestimated. A karst area located in Felipe Guerra, northeastern Brazil, which is a hotspot of subterranean diversity in Brazil, has revealed more than 20 troglobitic species, most of them still undescribed. Based on recent samplings in this karst area, we document the occurrence of the suborder Cavernicola (Platyhelminthes) in South American hypogean environments for the first time and describe a new genus and species for this suborder. Hausera Leal-Zanchet & Souza, gen. n. has features concordant with those defined for the family Dimarcusidae. The new genus is characterized by two unique features, viz. an intestine extending dorsally to the brain and ovovitelline ducts located dorsally to the nerve cords, which is complemented by a combination of other characters. The type-specimens of Hauserahauseri Leal-Zanchet & Souza, sp. n. are typical stygobionts, unpigmented and eyeless, and they may constitute an oceanic relict as is the case of other stygobiotic invertebrates found in this karst area in northeastern Brazil.

Diversity of introduced terrestrial flatworms in the Iberian Peninsula: a cautionary tale

Many tropical terrestrial planarians (Platyhelminthes, Geoplanidae) have been introduced around the globe. One of these species is known to cause significant decline in earthworm populations, resulting in a reduction of ecological functions that earthworms provide. Flatworms, additionally, are a potential risk to other species that have the same dietary needs. Hence, the planarian invasion might cause significant economic losses in agriculture and damage to the ecosystem. In the Iberian Peninsula only Bipalium kewense Moseley, 1878 had been cited till 2007. From that year on, four more species have been cited, and several reports of the presence of these animals in particular gardens have been received. In the present study we have: (1) analyzed the animals sent by non-specialists and also the presence of terrestrial planarians in plant nurseries and garden centers; (2) identified their species through morphological and phylogenetic molecular analyses, including representatives of their areas of origin; (3) revised their dietary sources and (4) used Species Distribution Modeling (SDM) for one species to evaluate the risk of its introduction to natural areas. The results have shown the presence of at least ten species of alien terrestrial planarians, from all its phylogenetic range. International plant trade is the source of these animals, and many garden centers are acting as reservoirs. Also, landscape restoration to reintroduce autochthonous plants has facilitated their introduction close to natural forests and agricultural fields. In conclusion, there is a need to take measures on plant trade and to have special care in the treatment of restored habitats.

Phylogenetic relationships within the flatworm genus Choeradoplana Graff (Platyhelminthes : Tricladida) inferred from molecular data with the description of two new sympatric species from Araucaria moist forests

The genus Choeradoplana encompasses 11 species, nine of which have a restricted distribution and are only known from their type localities. Herein we describe two new species of Choeradoplana from Araucaria moist forests, C. minima, sp. nov. Lemos & Leal-Zanchet and C. benyai, sp. nov. Lemos & Leal-Zanchet, based on morphological and molecular data, and use two molecular markers to investigate their phylogenetic relationships with other species in the genus, including its type species. Both morphological and molecular analyses clearly distinguish C. minima, sp. nov., C. benyai, sp. nov. and C. iheringi. The analyses of the ITS-1, COI and sequence divergence data also indicated that C. benyai, sp. nov. is more closely related to the type species of the genus, C. iheringi, than to C. minima, sp. nov. The three species are sympatric in Araucaria moist forest areas of the São Francisco de Paula National Forest; C. minima, sp. nov. and C. benyai, sp. nov. seem to be endemic to their type localities. Regarding external morphology, C. benyai, sp. nov. and C. iheringi could be considered cryptic species, only distinguishable on the basis of the copulatory apparatus. However, immature specimens of C. benyai, sp. nov. and C. iheringi could only be identified based on molecular data. Our results demonstrate that COI should be used with caution for reconstructing phylogenies, and other slower-evolving nuclear genes are a feasible alternative for resolving some of the phylogenetic relationships.

First report of the exotic blue land planarian, Caenoplana coerulea (Platyhelminthes, Geoplanidae), on Menorca (Balearic Islands, Spain)

In April 2009 two specimens of a terrestrial flatworm were collected from under a rock in an orchard at Ciutadella de Menorca on the easternmost Balearic island of Menorca (Spain). Their external morphology suggested that both specimens belonged to the invasive blue planarian Caenoplana coerulea, a species which is native to eastern Australia. Sequence data of a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) and of the entire 18S ribosomal RNA confirm its identification. This is one of the first records of the species in Europe where it has only been found in one locality in the United Kingdom, France and NE Spain.