Matteo Dal Zotto

Phylogeny of Thaumastodermatidae (Gastrotricha: Macrodasyida) Inferred from Nuclear and Mitochondrial Sequence Data

Background Phylogenetic relationships within Gastrotricha are poorly known. Attempts to shed light on this subject using morphological traits have led to hypotheses lacking satisfactory statistical support; it seemed therefore that a different approach was needed. Methodology/Principal Findings In this paper we attempt to elucidate the relationships within the taxonomically vast family Thaumastodermatidae (Macrodasyida) using molecular sequence data. The study includes representatives of all the extant genera of the family and for the first time uses a multi-gene approach to infer evolutionary liaisons within Gastrotricha. The final data set comprises sequences of three genes (18S, 28S rDNA and COI mtDNA) from 41 species, including 29 thaumastodermatids, 11 non-thaumastodermatid macrodasyidans and a single chaetonotidan. Molecular data was analyzed as a combined set of 3 genes and as individual genes, using Bayesian and maximum likelihood approaches. Two different outgroups were used: Xenotrichula intermedia (Chaetonotida) and members of the putative basal Dactylopodola (Macrodasyida). Thaumastodermatidae and all other sampled macrodasyidan families were found monophyletic except for Cephalodasyidae. Within Thaumastodermatidae Diplodasyinae and Thaumastodermatinae are monophyletic and so are most genera. Oregodasys turns out to be the most basal group within Thaumastodermatinae in analyses of the concatenated data set as well as in analyses of the nuclear genes. Thaumastoderma appears as the sister taxon to the remaining species. Surprisingly, Tetranchyroderma is non-monophyletic in our analyses as one group of species clusters with Ptychostomella while another appears as the sister group of Pseudostomella. Conclusions/Significance Results in general agree with the current classification; however, a revision of the more derived thaumastodermatid taxa seems necessary. We also found that the ostensible COI sequences from several species do not conform to the general invertebrate or any other published mitochondrial genetic code; they may be mitochondrially derived nuclear genes (numts), or one or more modifications of the mitochondrial genetic code within Gastrotricha.

Gastrotricha: A Marine Sister for a Freshwater Puzzle

Background Within an evolutionary framework of Gastrotricha Marinellina flagellata and Redudasys fornerise bear special interest, as they are the only Macrodasyida that inhabit freshwater ecosystems. Notwithstanding, these rare animals are poorly known; found only once (Austria and Brazil), they are currently systematised as incertae sedis. Here we report on the rediscovery of Redudasys fornerise, provide an account on morphological novelties and present a hypothesis on its phylogenetic relationship based on molecular data. Methodology/Principal Findings Specimens were surveyed using DIC microscopy and SEM, and used to obtain the 18 S rRNA gene sequence; molecular data was analyzed cladistically in conjunction with data from 42 additional species belonging to the near complete Macrodasyida taxonomic spectrum. Morphological analysis, while providing new information on taxonomically relevant traits (adhesive tubes, protonephridia and sensorial bristles), failed to detect elements of the male system, thus stressing the parthenogenetic nature of the Brazilian species. Phylogenetic analysis, carried out with ML, MP and Bayesian approaches, yielded topologies with strong nodal support and highly congruent with each other. Among the supported groups is the previously undocumented clade showing the alliance between Redudasys fornerise and Dactylopodola agadasys; other strongly sustained clades include the densely sampled families Thaumastodermatidae and Turbanellidae and most genera. Conclusions/Significance A reconsideration of the morphological traits of Dactylopodola agadasys in light of the new information on Redudasys fornerise makes the alliance between these two taxa very likely. As a result, we create Anandrodasys gen. nov. to contain members of the previously described D. agadasys and erect Redudasyidae fam. nov. to reflect this novel relationship between Anandrodasys and Redudasys. From an ecological perspective, the derived position of Redudasys, which is deeply nested within the Macrodasyida clade, unequivocally demonstrates that invasion of freshwater by gastrotrichs has taken place at least twice, in contrast with the single event hypothesis recently put forward.

Phylogeny of Kinorhyncha Based on Morphology and Two Molecular Loci

The phylogeny of Kinorhyncha was analyzed using morphology and the molecular loci 18S rRNA and 28S rRNA. The different datasets were analyzed separately and in combination, using maximum likelihood and Bayesian Inference. Bayesian inference of molecular sequence data in combination with morphology supported the division of Kinorhyncha into two major clades: Cyclorhagida comb. nov. and Allomalorhagida nom. nov. The latter clade represents a new kinorhynch class, and accommodates Dracoderes, Franciscideres, a yet undescribed genus which is closely related with Franciscideres, and the traditional homalorhagid genera. Homalorhagid monophyly was not supported by any analyses with molecular sequence data included. Analysis of the combined molecular and morphological data furthermore supported a cyclorhagid clade which included all traditional cyclorhagid taxa, except Dracoderes that no longer should be considered a cyclorhagid genus. Accordingly, Cyclorhagida is divided into three main lineages: Echinoderidae, Campyloderidae, and a large clade, ‘Kentrorhagata’, which except for species of Campyloderes, includes all species with a midterminal spine present in adult individuals. Maximum likelihood analysis of the combined datasets produced a rather unresolved tree that was not regarded in the following discussion. Results of the analyses with only molecular sequence data included were incongruent at different points. However, common for all analyses was the support of several major clades, i.e., Campyloderidae, Kentrorhagata, Echinoderidae, Dracoderidae, Pycnophyidae, and a clade with Paracentrophyes + New Genus and Franciscideres (in those analyses where the latter was included). All molecular analyses including 18S rRNA sequence data furthermore supported monophyly of Allomalorhagida. Cyclorhagid monophyly was only supported in analyses of combined 18S rRNA and 28S rRNA (both ML and BI), and only in a restricted dataset where taxa with incomplete information from 28S rRNA had been omitted. Analysis of the morphological data produced results that were similar with those from the combined molecular and morphological analysis. E.g., the morphological data also supported exclusion of Dracoderes from Cyclorhagida. The main differences between the morphological analysis and analyses based on the combined datasets include: 1) Homalorhagida appears as monophyletic in the morphological tree only, 2) the morphological analyses position Franciscideres and the new genus within Cyclorhagida near Zelinkaderidae and Cateriidae, whereas analyses including molecular data place the two genera inside Allomalorhagida, and 3) species of Campyloderes appear in a basal trichotomy within Kentrorhagata in the morphological tree, whereas analysis of the combined datasets places species of Campyloderes as a sister clade to Echinoderidae and Kentrorhagata.

Franciscideres gen. nov. – a new, highly aberrant kinorhynch genus from Brazil, with an analysis of its phylogenetic position

A new genus and species of Kinorhyncha, Franciscideres kalenesos gen. et sp. nov., is described from tidal and subtidal sandy habitats in Brazil. The new genus and species is characterized by an extremely flexible trunk without pachycycli that appears perfectly circular in cross-section, segments 1, 2 and 11 consisting of closed rings and 3 to 10 of single, bent plates with midventral articulations, a neck without placids that resembles an additional segment, densely packed scale-like, cuticular hairs, and a terminal segment with a middorsal spine and two sets of lateral terminal spines, but no midterminal spine. Phylogenetic analyses of 18S rRNA of Franciscideres kalenesos gen. et sp. nov. and 47 other kinorhynch ingroup taxa suggest that the new genus is a basal homalorhagid, whereas comparison of morphological characters indicates affinities between the new genus and the peculiar cyclorhagid Cateria. http://zoobank.org/urn:lsid:zoobank.org:pub:64E29D97-DE1D-4511-8683-C969DD2EED43

An Integrated Morphological and Molecular Approach to the Description and Systematisation of a Novel Genus and Species of Macrodasyida (Gastrotricha).

Background Gastrotricha systematics is in a state of flux mainly due to the conflicts between cladistic studies base on molecular markers and the classical systematisation based on morphological traits. In sandy samples from Thailand, we found numerous macrodasyidan gastrotrichs belonging to an undescribed species of difficult taxonomic affiliation. The abundance and original nature of the specimens prompted us to undertake a deep survey of both morphological and molecular traits aiming at a reliable systematisation of the new taxon. Methodology/Principal Findings Using several microscopical techniques we investigated the external and internal anatomy, including the muscular and nervous systems of the new species. Additional specimens were used to obtain the 18S rRNA gene sequence; molecular data was analysed cladistically in conjunction with data from additional species belonging to the near complete Macrodasyida taxonomic spectrum. Specimens are vermiform, up to 806 μm in total length, and show a well-defined head equipped with peculiar leaf-like sensorial organs and a single-lobed posterior end. The adhesive apparatus includes anterior, ventrolateral, dorsal and posterior tubes. Pharynx is about 1/4 of the total length and shows pores at its posterior 3/4. Adult specimens exhibit maturing eggs and a bulky, muscular caudal organ, but do not show sperm nor the frontal organ. Musculature and nervous system organisation resemble the usual macrodasyidan plan; however, the somatic circular muscles of the intestinal region surround all other muscular components and a third FMRFamide-IR commissure ventral to the pharyngo-intestinal junction appear to be an autoapomorphic traits of the new species. Conclusions/Significance While the anatomical characteristics of the Asian specimens appear so unique to grant the establishment of a new taxon, for which the name Thaidasys tongiorgii gen. et sp. nov. is proposed, the result of phylogenetic analyses based on the 18S rRNA gene unites the new genus with the family Macrodasyidae.

First records of Gastrotricha from South Africa, with description of a new species of Halichaetonotus (Chaetonotida, Chaetonotidae).

Abstract During a survey of the biota of the St. Lucia Estuary in the iSimangaliso Wetland Park, South Africa, a number of Gastrotricha were found among samples of meiofauna. Fresh, marine sediment yielded several specimens belonging to a total of seven species. Of these, two are already known from other regions (i.e., Dactylopodola australiensis and Heteroxenotrichula squamosa), one is described as new to science (Halichaetonotus sanctaeluciae sp. n.), while the remaining four (Pseudostomella sp., Halichaetonotus sp.1, Halichaetonotus sp. 2, Xenotrichula sp.) require further collections and analysis, in order to establish the extent of their affiliation to species already described. General appearance, shape of hydrofoil scale and the occurrence of three long spines on the dorsal side make the new species most closely related to Halichaetonotus australis and Halichaetonotus marivagus. The key differences from these taxa and between Halichaetonotus sanctaeluciae sp. n. and Halichaetonotus aculifer are discussed.

Antygomonas caeciliae, a new kinorhynch from the Mediterranean Sea, with report of mitochondrial genetic data for the phylum

AbstractKinorhyncha is a phylum of microscopic marine metazoans living from intertidal to abyssal depths. More than 200 species are known; nevertheless, recent studies have pointed out that most of this group’s diversity has not been revealed. A survey of the peculiar Meloria Shoals seabed (Ligurian Sea, Italy) led to the discovery of a new kinorhynch named Antygomonas caeciliae sp. nov. A cytochrome c oxidase subunit I (COI) mtDNA gene is reported for the new species; hence, a morphological and molecular approach is used for the description of this new taxon, and a comparison with related species is proposed, including a key to the species of Antygomonas. Some additional COI sequences are reported for other taxa of the phylum, with the aim of developing molecular tools which will be useful for species identification, particularly when dealing with juvenile stages.http://zoobank.org/urn:lsid:zoobank.org:pub:26BD19DD-30E6-40D3-9E4C-82D117D9CEF9Abstract Kinorhyncha is a phylum of microscopic marine metazoans living from intertidal to abyssal depths. More than 200 species are known; nevertheless, recent studies have pointed out that most of this group’s diversity has not been revealed. A survey of the peculiar Meloria Shoals seabed (Ligurian Sea, Italy) led to the discovery of a new kinorhynch named Antygomonas caeciliae sp. nov. A cytochrome c oxidase subunit I (COI) mtDNA gene is reported for the new species; hence, a morphological and molecular approach is used for the description of this new taxon, and a comparison with related species is proposed, including a key to the species of Antygomonas. Some additional COI sequences are reported for other taxa of the phylum, with the aim of developing molecular tools which will be useful for species identification, particularly when dealing with juvenile stages. http://zoobank.org/urn:lsid:zoobank.org:pub:26BD19DD-30E6-40D3-9E4C-82D117D9CEF9

A new species of Aspidiophorus (Gastrotricha, Chaetonotida) from the Russian Far East with a key to marine species of the genus

Abstract The Russian gastrotrich fauna is virtually unknown, particularly the marine fauna. In the ocean, investigations have been restricted to the White Sea, from where only three fully described species have been reported so far. In this study we describe a new species of Aspidiophorus found in a sandy sample collected from off of Vladivostok (Peter the Great Bay, Sea of Japan). Aspidiophorus oculatus n. sp. is the first marine chaetonotid gastrotrich described from Russia and the first representative of the order Chaetonotida reported from the Sea of Japan. Specimens of the new species are characterized by a body up to 147.5 µm in total length; enveloped by 57 alternating columns of 65–70 keeled, elongate scales. Pharyngeo-intestinal junction at U27; the head bears cephalion, hypostomion, pleuria and a pair of eye-spots; the furca is 20 µm long including the 12-µm long adhesive tube; the ventral interciliary field is naked, with the exception of a pair of elliptical, keeled scales occurring near the anus. Morphological differences between the new species and the other 13 marine con-generic taxa are discussed. A key to the known marine species of the world based on easily identifiable traits, visible in both living and formalin-fixed specimens is provided.

Two new interesting species of Macrodasyida (Gastrotricha) from KwaZulu-Natal (South Africa)

Abstract This study is part of a larger research program aimed at shedding light on meiofauna and macrofauna communities of the subtropical Eastern Province of KwaZulu-Natal, South Africa. Previous articles on the phylum Gastrotricha have detailed faunistic and preliminary taxonomic data on marine and freshwater species found in the iSimangaliso Wetland Park. Here, two new interesting marine macrodasyidan species, in the families Cephalodasyidae and Turbanellidae, are reported from a wider area of the KZN coast. Descriptions are based on observations carried out on living specimens using differential interference contrast microscopy. Pleurodasys incomptus new species is the second species in the genus; surprisingly, it lacks the peculiar gravireceptor organs (pharyngeal knobs) thought to be an autapomorphic trait of the genus. Paraturbanella africana new species is a mid-sized species (up to 520 μm in length), showing a peribuccal swelling; its most obvious autapomorphic trait pertains to the testes, which are located well passed half the body rather than at- or near the pharyngo-intestinal junction as occur in the other species of the genus. The relevant anatomical novelties shown by the two new species testify that current knowledge about gastrotrich basic morphology is far from complete. This holds true also for taxa that are considered to be well-known (e.g. the speciose genus Paraturbanella), and stresses once again the importance of investigating new geographic areas in order to improve our understanding of global gastrotrich morphological diversity and species richness.

A new species of Turbanellidae (Gastrotricha, Macrodasyida) from Jamaica, with a key to species of Paraturbanella

Abstract The study falls within the framework of a wider research programme aimed at investigating the gastrotrich diversity of the Tropical North-Western Atlantic (TNWA). A new macrodasyidan gastrotrich is described from fine-medium sand collected at Duncans Bay, Jamaica. The description is based on observations carried out on living specimens using differential interference contrast microscopy. Paraturbanella xaymacana sp. n., the third gastrotrich taxon reported from Jamaica, is a mid-sized species, up to 564 μm long, with a feeble peribuccal swelling. The most obvious autapomorphic traits pertain to the testes and the male pore, both of which are located approximately at mid body, rather than at- or near the pharyngo-intestinal junction as occur in the other species of the genus. Additional differences with congeners are discussed and a key to the Paraturbanella species is provided, in the hope it will be useful to both gastrotrich experts and marine ecologists who discover these microscopic metazoans during their research.