A phylum-wide survey reveals multiple independent gains of head regeneration in nemertea

Animals vary widely in their ability to regenerate, suggesting that regenerative ability has a rich evolutionary history. However, our understanding of this history remains limited because regenerative ability has only been evaluated in a tiny fraction of species. Available comparative regeneration studies have identified losses of regenerative ability, yet clear documentation of gains is lacking. We assessed ability to regenerate heads and tails either through our own experiments or from literature reports for 35 species of Nemertea spanning the diversity of the phylum, including representatives of 10 families and all three orders. We generated a phylogenetic framework using sequence data to reconstruct the evolutionary history of head and tail regenerative ability across the phylum and found that all evaluated species can remake a posterior end but surprisingly few could regenerate a complete head. Our analysis reconstructs a nemertean ancestor unable to regenerate a head and indicates independent gains of head regenerative ability in at least four separate lineages, with one of these gains taking place as recently as the last 10-15 Myr. Our study highlights nemerteans as a valuable group for studying evolution of regeneration and identifying mechanisms associated with repeated gains of regenerative ability.Fil: Zattara, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. National Museum of Natural History; Estados Unidos. University of Maryland; Estados UnidosFil: Fernández Álvarez, Fernando Ángel. Consejo Superior de Investigaciones Científicas. Instituto de Ciencias del Mar; EspañaFil: Hiebert, Terra. University of Oregon; Estados UnidosFil: Bely, Alexandra. University of Maryland; Estados UnidosFil: Norenburg, Jon L.. National Museum of Natural History; Estados Unido

A comparative study of nemertean complete mitochondrial genomes, including two new ones for Nectonemertes cf. mirabilis and Zygeupolia rubens, may elucidate the fundamental pattern for the phylum Nemertea

<p>Abstract</p> <p>Background</p> <p>The mitochondrial genome is important for studying genome evolution as well as reconstructing the phylogeny of organisms. Complete mitochondrial genome sequences have been reported for more than 2200 metazoans, mainly vertebrates and arthropods. To date, from a total of about 1275 described nemertean species, only three complete and two partial mitochondrial DNA sequences from nemerteans have been published. Here, we report the entire mitochondrial genomes for two more nemertean species: <it>Nectonemertes </it>cf. <it>mirabilis </it>and <it>Zygeupolia rubens</it>.</p> <p>Results</p> <p>The sizes of the entire mitochondrial genomes are 15365 bp for <it>N</it>. cf. <it>mirabilis </it>and 15513 bp for <it>Z. rubens</it>. Each circular genome contains 37 genes and an AT-rich non-coding region, and overall nucleotide composition is AT-rich. In both species, there is significant strand asymmetry in the distribution of nucleotides, with the coding strand being richer in T than A and in G than C. The AT-rich non-coding regions of the two genomes have some repeat sequences and stem-loop structures, both of which may be associated with the initiation of replication or transcription. The 22 tRNAs show variable substitution patterns in nemerteans, with higher sequence conservation in genes located on the H strand. Gene arrangement of <it>N</it>. cf. <it>mirabilis </it>is identical to that of <it>Paranemertes </it>cf. <it>peregrina</it>, both of which are Hoplonemertea, while that of <it>Z. rubens </it>is the same as in <it>Lineus viridis</it>, both of which are Heteronemertea. Comparison of the gene arrangements and phylogenomic analysis based on concatenated nucleotide sequences of the 12 mitochondrial protein-coding genes revealed that species with closer relationships share more identical gene blocks.</p> <p>Conclusion</p> <p>The two new mitochondrial genomes share many features, including gene contents, with other known nemertean mitochondrial genomes. The tRNA families display a composite substitution pathway. Gene order comparison to the proposed ground pattern of Bilateria and some lophotrochozoans suggests that the nemertean ancestral mitochondrial gene order most closely resembles the heteronemertean type. Phylogenetic analysis proposes a sister-group relationship between Hetero- and Hoplonemertea, which supports one of two recent alternative hypotheses of nemertean phylogeny.</p

Editorial: diversity of marine meiofauna on the coast of Brazil

After a first bout of primarily taxonomical effort, meiofauna studies in Brazilian waters remained virtually neglected until the 1990s. At the end of the last century, taxonomical and ecological studies on meiofauna taxa were again published regularly, especially for Nematoda and Copepoda. In this issue, 18 new species are described and ten species are redescribed from seven Phyla. The five ecological articles cover the spatial distribution of forams and amoeba in a lagunar system, the meiofauna associated with biogenic structures, the relationship between nematodes and granulometry, and the response of sandy-beach meiofauna to a natural, short-term pulse of diatoms. All these contributions show the potential of the Brazilian coast for revealing new species and testing small to large-scale hypotheses about ecological processes

Phylogenetics of Trachylina (Cnidaria: Hydrozoa) with new insights on the evolution of some problematical taxa

Some of the most interesting and enigmatic cnidarians are classified within the hydrozoan subclass Trachylina. Despite being relatively depauperate in species richness, the clade contains four taxa typically accorded ordinal status: Actinulida, Limnomedusae, Narcomedusae and Trachymedusae. We bring molecular data (mitochondrial 16S and nuclear small and large subunit ribosomal genes) to bear on the question of phylogenetic relationships within Trachylina. Surprisingly, we find that a diminutive polyp form, Microhydrula limopsicola (classified within Limnomedusae) is actually a previously unknown life stage of a species of Stauromedusae. Our data confirm that the interstitial form Halammohydra sp. (Actinulida) is derived from holopelagic direct developing ancestors, likely within the trachymedusan family Rhopalonematidae. Trachymedusae is shown to be diphyletic, suggesting that the polyp stage has been lost independently at least two times within trachyline evolution. Narcomedusae is supported as a monophyletic group likely also arising from trachymedusan ancestors. Finally, some data, albeit limited, suggest that some trachyline species names refer to cryptic species that have yet to be sorted taxonomicall

Phylogenetics of Trachylina (Cnidaria: Hydrozoa) with new insights on the evolution of some problematical taxa

This is the published version, also available here: http://dx.doi.org/10.1017/S0025315408001732.Some of the most interesting and enigmatic cnidarians are classified within the hydrozoan subclass Trachylina. Despite being relatively depauperate in species richness, the clade contains four taxa typically accorded ordinal status: Actinulida, Limnomedusae, Narcomedusae and Trachymedusae. We bring molecular data (mitochondrial 16S and nuclear small and large subunit ribosomal genes) to bear on the question of phylogenetic relationships within Trachylina. Surprisingly, we find that a diminutive polyp form, Microhydrula limopsicola (classified within Limnomedusae) is actually a previously unknown life stage of a species of Stauromedusae. Our data confirm that the interstitial form Halammohydra sp. (Actinulida) is derived from holopelagic direct developing ancestors, likely within the trachymedusan family Rhopalonematidae. Trachymedusae is shown to be diphyletic, suggesting that the polyp stage has been lost independently at least two times within trachyline evolution. Narcomedusae is supported as a monophyletic group likely also arising from trachymedusan ancestors. Finally, some data, albeit limited, suggest that some trachyline species names refer to cryptic species that have yet to be sorted taxonomically

Sampling multiple life stages significantly increases estimates of marine biodiversity

Biodiversity assessments are critical for setting conservation priorities, understanding ecosystem function and establishing a baseline to monitor change. Surveys of marine biodiversity that rely almost entirely on sampling adult organisms underestimate diversity because they tend to be limited to habitat types and individuals that can be easily surveyed. Many marine animals have planktonic larvae that can be sampled from the water column at shallow depths. This life stage often is overlooked in surveys but can be used to relatively rapidly document diversity, especially for the many species that are rare or live cryptically as adults. Using DNA barcode data from samples of nemertean worms collected in three biogeographical regions—Northeastern Pacific, the Caribbean Sea and Eastern Tropical Pacific—we found that most species were collected as either benthic adults or planktonic larvae but seldom in both stages. Randomization tests show that this deficit of operational taxonomic units collected as both adults and larvae is extremely unlikely if larvae and adults were drawn from the same pool of species. This effect persists even in well-studied faunas. These results suggest that sampling planktonic larvae offers access to a different subset of species and thus significantly increases estimates of biodiversity compared to sampling adults alone. Spanish abstract is available in the electronic supplementary material.Fil: Maslakova, Svetlana A.. University of Oregon; Estados UnidosFil: Ellison, Christina I.. University of Oregon; Estados UnidosFil: Hiebert, Terra C.. University of Oregon; Estados UnidosFil: Conable, Frances. University of Oregon; Estados UnidosFil: Heapy, Maureen C.. University of Oregon; Estados UnidosFil: Venera Pontón, Dagoberto E.. Smithsonian Tropical Research Institute; PanamáFil: Norenburg, Jon L.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Schwartz, Megan L.. University of Washington; Estados UnidosFil: Boyle, Michael J.. Smithsonian Tropical Research Institute; PanamáFil: Driskell, Amy C.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Macdonald, Kenneth S.. National Museum Of Natural History. Departamento de Zoología. Area de Invertebrados; Estados UnidosFil: Zattara, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Collin, Rachel. Smithsonian Tropical Research Institute; Panam

Biodiversity estimates and ecological interpretations of meiofaunal communities are biased by the taxonomic approach

Accurate assessments of biodiversity are crucial to advising ecosystem-monitoring programs and understanding ecosystem function. Nevertheless, a standard operating procedure to assess biodiversity accurately and consistently has not been established. This is especially true for meiofauna, a diverse community (&gt;20 phyla) of small benthic invertebrates that have fundamental ecological roles. Recent studies show that metabarcoding is a cost-effective and timeeffective method to estimate meiofauna biodiversity, in contrast to morphological-based taxonomy. Here, we compare biodiversity assessments of a diverse meiofaunal community derived by applying multiple taxonomic methods based on comparative morphology, molecular phylogenetic analysis, DNA barcoding of individual specimens, and metabarcoding of environmental DNA. We show that biodiversity estimates are strongly biased across taxonomic methods and phyla. Such biases affect understanding of community structures and ecological interpretations. This study supports the urgency of improving aspects of environmental high-throughput sequencing and the value of taxonomists in correctly understanding biodiversity estimates

Nemertean taxonomy- Implementing changes in the higher ranks, dismissing Anopla and Enopla

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Raymond Gibson (1938–2023): in memoriam

On 29 January 2023, Raymond (Ray) Gibson (Fig. 1), Professor Emeritus of Liverpool John Moores University, died in a hospital on the Wirral. He lived a very busy life, rich in travels and scientific discoveries, and he was one of the most authoritative world experts in the taxonomy of nemerteans. Ray was born on 23 November 1938 in Catterick Village in Yorkshire. He gained his Private Pilot’s License aged 17 and had several adventures in the small plane. In 1965 after leaving the Royal Airforce as a qualified pilot he got his B.Sc. in Zoology First class degree from Leeds University and in 1968 gained his Ph.D. from Leeds University. Ray began his interest in nemerteans when he was a student at Leeds University. His Ph.D. supervisor was Dr. Joe Jennings, who at the time was researching the nutrition and digestion of nemerteans and “turbellarians” (a grade of free-living platyhelminths). Ray’s first articles on the nutrition and biology of Malacobdella grossa were published when he was at Leeds University (Gibson 1967, 1968; Gibson & Jennings 1969). In 1971 Ray joined the Liverpool Regional College of Technology (this became Liverpool Polytechnic and then Liverpool John Moores University), where he worked for 30 years. His first book (Gibson 1972) is an excellent summary of knowledge on nemertean biology at the time and has ‘entangled’ (rather than ‘hooked’) young students worldwide in the following generations into this field. Ray’s exploratory enthusiasm was unmatched. He would come early in the morning and spend the day in concentrated writing, microscopy, or figure preparation. An ashtray was ever present next to his microscope and cigarettes and black coffee were all he needed to sustain him through the long days. For a long time, the histology unit was complete with the all-pervasive smell of xylene. He supervised post-graduates from many countries and backgrounds, teaching them the intricacies of paraffin sectioning and histochemistry.Peer reviewe