Probing recalcitrant problems in polyclad evolution and systematics with novel mitochondrial genome resources.

For their apparent morphological simplicity, the Platyhelminthes or "flatworms" are a diverse clade found in a broad range of habitats. Their body plans have however made them difficult to robustly classify. Molecular evidence is only beginning to uncover the true evolutionary history of this clade. Here we present nine novel mitochondrial genomes from the still undersampled orders Polycladida and Rhabdocoela, assembled from short Illumina reads. In particular we present for the first time in the literature the mitochondrial sequence of a Rhabdocoel, Bothromesostoma personatum (Typhloplanidae, Mesostominae). The novel mitochondrial genomes examined generally contained the 36 genes expected in the Platyhelminthes, with all possessing 12 of the 13 protein-coding genes normally found in metazoan mitochondrial genomes (ATP8 being absent from all Platyhelminth mtDNA sequenced to date), along with two ribosomal RNA genes. The majority presented possess 22 transfer RNA genes, and a single tRNA gene was absent from two of the nine assembled genomes. By comparison of mitochondrial gene order and phylogenetic analysis of the protein coding and ribosomal RNA genes contained within these sequences with those of previously sequenced species we are able to gain a firm molecular phylogeny for the inter-relationships within this clade. Our phylogenetic reconstructions, using both nucleotide and amino acid sequences under several models and both Bayesian and Maximum Likelihood methods, strongly support the monophyly of Polycladida, and the monophyly of Acotylea and Cotylea within that clade. They also allow us to speculate on the early emergence of Macrostomida, the monophyly of a "Turbellarian-like" clade, the placement of Rhabditophora, and that of Platyhelminthes relative to the Lophotrochozoa (=Spiralia). The data presented here therefore represent a significant advance in our understanding of platyhelminth phylogeny, and will form the basis of a range of future research in the still-disputed classifications within this taxon.

State of knowledge of the Acotylea (Polycladida, Platyhelminthes) from the Mediterranean coasts of Spain: new records and new species.

Along the Mediterranean coast of the Iberian Peninsula, great species diversity is thought to exist, but our knowledge of Iberian polyclads is, in fact, very limited. This study contributes to the Polycladida (Platyhelminthes) of the Iberian Peninsula, in particular those of the Mediterranean coast. Nine species, mainly new species or new records, are described. Imogine stellae sp. nov. from Mar Menor (Murcia, Spain) is described, while I. mediterranea Galleni, 1976 is recorded for the first time in Spain. The genus Planocera Blainville, 1828 within the Mediterranean basin is reviewed: Planocera graffi Lang, 1879 is redescribed, and its synonymisation with Planocera pellucida (Mertens, 1833) considered. Also, the genus Notoplanella Bock, 1931 is represented by two species in Spain, N. inarmata Bock, 1931 type species, from Formentera Island and N. estelae sp. nov., from Mar Menor. Trigonoporus cephalophtalmus Lang, 1884 is rediscovered after the description of Lang (1884). Stylochus neapolitanus (Delle Chiaje, 1841-1844) Lang, 1884 is recorded and S. pilidium (Goette, 1881) is also redescribed, and Leptoplana mediterranea (Bock, 1913) is newly recorded for the Iberian Peninsula.

A New Polyclad Flatworm, Idiostylochus tortuosus gen. nov., sp. nov. (Platyhelminthes, Polycladida) from France. Can this Foreign Flatworm be Responsible for the Deterioration of Oyster and Mussel Farms?

A new species of polyclad flatworm, Idiostylochus tortuosus gen. nov., sp. nov. (Polycladida, Idioplanidae), from Arcachon Bay (France) is described. This description is based on a morphological analysis and a molecular analysis using partial sequences of the 28S and cytochrome Oxidase I (COI) genes. After the molecular analysis Idiostylochus gen. nov. appears to be the second genus of the Family Idioplanidae and closely related to the family Latocestidae as well as the genera Leptostylochus and Mirostylochus. The molecular data revealed that the new species may belong to an Indonesian or Indo-Pacific family, closely related to genera with origins in South Pacific Ocean waters. This species was found feeding on the oysters and mussels of the Arcachon farms.

First study of the Polycladida (Rhabditophora, Platyhelminthes) from the Pacific Coast of Costa Rica.

In the present work was carried out in the intertidal zone of Las Baulas de Guanacaste National Marine Park (PNMB) located on the Pacific coast of Costa Rica.                The main objective was to contribute to knowledge about the invertebrate diversity of the park, one of the richest bioregions on the planet, about which little is known. This study assesses the Order Polycladida Lang, 1884, a cornerstone of this ecosystem and one of the most cosmopolitan and plastic invertebrate taxa in the animal kingdom.                In total, 57 individuals were collected in the rocky intertidal zone of Carbón and Langosta beaches. Nine different species were identified, of which four are new for Costa Rica: Semonia bauliensis n. sp.; Cryptostylochus sesei n. sp.; Paraplanocera angeli n. sp., Prostheceraeus fitae n. sp.; and five new records: Paraplanocera oligoglena (Schmarda, 1859); Marcusia ernesti Hyman, 1953; Enchiridium magec Cuadrado, Moro Noreña, 2017; Pseudobiceros bajae (Hyman, 1953); and the genus Boninia spp.

Description of the snail-eating flatworm in marine aquaria, Pericelis tectivorum sp. nov. (Polycladida, Platyhelminthes).

We describe a new marine snail-eating flatworm, Pericelis tectivorum sp. nov., found in coral-bearing marine aquaria. Pericelis tectivorum sp. nov. is characterised by several differential characters of the external and internal morphology like 1) a long line of frontal eyes extending anteriorly; 2) the length of the penis papilla; 3) the spherical seminal vesicle; 4) the lack of the enlargements of the ejaculatory duct; 5) the uterine vesicles, which start posterior of the female genital at the level of the sucker and 6) the distinct sucker. The combination of these characters in one species is unique and therefore the studied specimens are recognised by us as a new species. We additionally present a phylogenetic reconstruction using partial 28S rDNA sequences including three congeners. Our analysis demonstrates that P. tectivorum sp. nov. differs also genetically from other Pericelis species included in this analysis.

New Dalyelliidae (Platyhelminthes, Rhabditophora) from Buenos Aires Province, Argentina, and their stylet ultrastructure.

Two new species of Dalyellidae, Dalyellia callvucurai n. sp. and Gieysztoria namuncurai n. sp., are described from temporary freshwater environments in central Buenos Aires Province, Argentina. The ultrastructure of the stylets of both species is also described. The new species of the genus Dalyellia is the second species of the genus found in the neotropics and the first whose stylet has been studied with scanning electron microscopy. Gieysztoria namuncurai n. sp. joins the seven species of the genus known in Argentina. The ultrastructural characteristics of the stylet place it in the Inaequales group, with complex stylets.

Characterization of the complete mitochondrial genomes from Polycladida (Platyhelminthes) using next-generation sequencing.

The complete mitochondrial genomes of three polycladids, the acotylean Hoploplana elisabelloi and the cotyleans Enchiridium sp. and Prosthiostomum siphunculus have been assembled with high coverage from Illumina sequencing data. The mt genomes contain 36 genes including 12 of the 13 protein-coding genes characteristic for metazoan mitochondrial genomes, two ribosomal RNA genes, and 22 transfer RNA genes. Gene annotation, gene order, genetic code, start and stop codons and codon bias have been identified. In comparison with the well investigated parasitic Neodermata, our analysis reveals a great diversity of gene orders within Polycladida and Platyhelminthes in general. By analyzing representative genomes of the main groups of Platyhelminthes we explored the phylogenetic relationships of this group. The phylogenetic analyses strongly supported the monophyly of Polycladida, and based on a small taxon sampling suggest the monophyly of Acotylea and Cotylea.

New species of Gieysztoria (Platyhelminthes, Rhabdocoela) from Peruvian Amazon floodplain with description of their stylet ultrastructure.

The free-living Platyhelminthes of the Amazon basin are poorly known. Presently only four turbellarian species have been mentioned from the Amazon river, a fact that confirms the lack of information on this kind of faunas in this huge basin. Three new species of Gieysztoria from Amazonian floodplain in Peru are described herein: G. chiqchi n. sp., G. kasasapa n. sp. and G. sasa n. sp. The samples were taken in the Pacaya-Samiria National Reserve (Peru) during September 2002. Besides the usual description of the stylet based on whole mounted specimens, we provide a complementary description using SEM, which allowed differentiation of the new species within the currently yet imperfect picture of the Amazonian turbellarian fauna. Although further research is desired, current findings are suggestive of high diversity of free-living Turbellaria in the surveyed region.

New records of Cotylea (Polycladida, Platyhelminthes) from Lizard Island, Great Barrier Reef, Australia, with remarks on the distribution of the Pseudoceros Lang, 1884 and Pseudobiceros Faubel, 1984 species of the Indo-Pacific Marine Region.

In the present work eleven polyclad species of Lizard Island are studied. Seven of them are new records for this locality of the Australian coral reef and one is new to science, Lurymare clavocapitata n. sp. (Family Prosthiostomidae). The remaining recorded species belong to the genera Pseudoceros (P. bimarginatus, P. jebborum, P. stimpsoni, P. zebra, P. paralaticlavus and P. prudhoei) and Pseudobiceros (Pb. hancockanus, Pb. hymanae, Pb. flowersi and Pb. uniarborensis). Regardless of the different distribution patterns, all pseudocerotid species show brilliant colours, but similar internal morphology. Furthermore, differences in the form and size of the stylet are characteristic, because it is a sclerotic structure that is not affected during fixation. In Pseudoceros, the distance between the sucker and the female pore also differs among species. These features do not vary enough to be considered as diagnostic, but they provide information that can help to disentangle similarly coloured species complexes. A key of the genera Pseudoceros and Pseudobiceros of the Indo-Pacific region is provided, in order to facilitate the identification of species from this area.

New Acotylea (Polycladida, Platyhelminthes) from the east coast of the North Atlantic Ocean with special mention of the Iberian littoral.

Polyclad species diversity, although generally well known for European North Atlantic waters, is nearly unknown for the Iberian Peninsula. The "Ría de Arousa", located on the Atlantic coast of Galicia (Spain), is a place where many positive biological factors for species biodiversity converge. Therefore, it is an ideal location to study polyclad diversity. This research, which describes new records and new species, contributes to the knowledge of the distribution of Polycladida (Platyhelminthes), particularly of the suborder Acotylea, in the Atlantic waters of the Iberian Peninsula. The new records include the re-descriptions of Cryptocelis compacta Lang, 1884, Stylochus neapolitanus (Delle Chiaje, 1841-1844) and Discocelis tigrina (Blanchard, 1847), while the two newly described species are Hoploplana elisabelloi n. sp. and Armatoplana celta n. sp.

A transcriptomic-phylogenomic analysis of the evolutionary relationships of flatworms.

The interrelationships of the flatworms (phylum Platyhelminthes) are poorly resolved despite decades of morphological and molecular phylogenetic studies. 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.

First records of Cotylea (Polycladida, Platyhelminthes) for the Atlantic coast of the Iberian Peninsula.

A study of polyclad fauna of the Atlantic coast of the Iberian Peninsula was carried out from 2010 to 2013. The paper reports nine new records belonging to three Cotylean families: the family Euryleptidae Lang, 1884, Pseudocerotidae Lang, 1884 and the family Prosthiostomidae Lang, 1884, and describes one new species, Euryleptodes galikias sp. n.