Polychaetes of Greece: an updated and annotated checklist

A sea of worms: the striking cases of the European Perinereis cultrifera and P. rullieri (Annelida: Nereididae) species complexes, with description of 13 new species

Molecular data have been suggesting the existence of a complex of cryptic species within the taxon Perinereis cultrifera , which has not been fully explored yet. In this study, we performed a morphological and molecular analysis (mtCOI-5P , 16S rRNA and 28SD2 rRNA ) of Perinereis specimens from intertidal marine and brackish European localities, mostly focusing on the Mediterranean Sea and the Canary Islands. Two major phylogenetic clades with at least 18 divergent (COI , 19.8; 6.4-28.5%) and completely sorted lineages were uncovered based on original data, 13 of which occurred exclusively in the Mediterranean Sea, a further 5 of which are unique to Italian brackish waters. An additional morphologically similar lineage, corresponding to P. oliveirae , coexisting with the single NE Atlantic lineage of the complex, was also retrieved as an ingroup. Careful morphological inspection, combined with the deep divergence between the two major molecular clades and the perfect match of each clade to the specific paragnath and chaetal types, highlighted the existence of two distinct groups of European Perinereis species: Clade A, which shows features matching historical descriptions of P. cultrifera , and Clade B corresponding to an overlooked morphotype described as P. rullieri . Although paragnaths show a similar pattern in the two clades, their sizes are considerably smaller in P. rullieri and the chaetae are characterised by coarse serration at the base of the spiniger blades and long falciger blades, as opposed to the lightly serrated blades and short falcigers in P. cultrifera . Further overlooked morphological features mainly based on thickness, direction and length of paragnaths, as well as the expansion of posteriormost dorsal ligules were also revealed within each major clade, which together with geographic and environmental boundaries allowed for the differentiation of most of these lineages without molecular data. Thirteen new species are here formally described, eight belonging to Clade A: P. caesarea sp. nov., P. faulwetterae sp. nov., P. houbinae sp. nov., P. maleniae sp. nov., P. miquellai sp. nov., P. muscoi sp. nov., P. nieri sp. nov. and P. twobae sp. nov.; and five belonging to Clade B: P. castellii sp. nov., P. juno sp. nov., P. jupiter sp. nov., P. minerva sp. nov. and P. tibicena sp. nov. The new combination P. beaucoudrayi is also proposed for Nereis beaucoudrayi , previously considered synonymous with P. cultrifera , for the only lineage occurring in the NE Atlantic. Lastly, Perinereis cultrifera s.s., P. rullieri s.s and the ingroup P. oliveirae are redescribed using topotypical material, with available syntypes and lectotypes assigned to the former two. ZooBank: urn:lsid:zoobank.org:pub:28C64123-DE82-411D-BC96-5E892FC692E3.

Reappraisal of the hyperdiverse

Morphologically similar species are often overlooked but molecular techniques have been effective in signalling potential hidden diversity, boosting the documentation of unique evolutionary lineages and ecological diversity. Platynereis dumerilii and Platynereis massiliensis are part of a recognised species complex, where differences in the reproductive biology have mainly been highlighted to date. Analyses of DNA sequence data (COI, 16S rDNA and D2 region of the 28S rDNA) of populations of the apparent morphotype of P. dumerilii obtained from a broader sampling area along European marine waters, including the Azores and Webbnesia islands (Madeira and Canaries), provided compelling evidence for the existence of at least 10 divergent evolutionary lineages. Complementing the genetic data, morphological observations of the better represented lineages revealed two major groups with distinctive paragnath patterns. Two new Platynereis species were erected: P. nunezi sp. nov., widespread in the Azores and Webbnesia islands, and P. jourdei sp. nov., restricted to the western Mediterranean. The new combination P. agilis is also proposed for Nereis agilis, previously unaccepted for one of the lineages present both in the Northeast Atlantic and western Mediterranean. Platynereis dumerilii is redescribed based on topotypic material. However, uncertainty in the identity of P. massiliensis due to the original brief description and the absence of type and topotypic material prevents the unequivocal assignment to the lineage assumed in this and previous studies. The remaining five lineages are represented by only a few small specimens with morphological features poorly preserved and were therefore not described in this study. ZooBank: urn:lsid:zoobank.org:pub:50079615-85E5-447E-BDD7-21E81C2A6F4D

Description of the new species Sigambra nkossa (Annelida, Pilargidae), with an analysis of the distribution patterns of polychaetes associated with artificially hydrocarbon-enriched bottoms

The monitoring of the N'Kossa offshore oil and gas fields in the Republic of Congo allowed us to assess the ecological traits of two polychaete species belonging to Sigambra (Annelida, Pilargidae). Sigambra parva occur in very low densities in all bottoms, except the most impacted, where it is totally absent; it is an undescribed species that reached >4,000 ind/m2 in hydrocarbon-enriched sediments. Their distribution patterns are compared with those of other polychaetes, showing a range of affinities for hydrocarbon-enriched sediments in the N'Kossa region. Our results suggest that S. parva would be a representative of the original local fauna, while the species associated with artificial hydrocarbon-enriched sediments, including the other Sigambra, six more polychaetes and a bivalve, could be natively associated with natural hydrocarbon-enriched sediments, using the former as alternative habitats and as dispersal stepping stones. This ecological segregation, together with a careful morphological and morphometric analyses led us to describe the latter as a new species, namely Sigambra nkossa sp. nov. Moreover, morphometric analysis allowed us to discuss on the taxonomic robustness of the key morphological characters of S. nkossa sp. nov., as well as to emend the generic diagnosis of Sigambra to accommodate the new species.

Still Digging: Advances and Perspectives in the Study of the Diversity of Several Sedentarian Annelid Families

Sedentarian annelids are a diverse and heterogeneous group of marine worms representing more than 8600 species gathered in ca. 43 families. The attention brought to these organisms is unevenly distributed among these families, and the knowledge about them sometimes scarce. We review here the current knowledge about the families Acrocirridae, Cirratulidae (including Ctenodrilidae), Cossuridae, Longosomatidae, Paraonidae, and Sternaspidae in terms of biodiversity as well as the evolution of the taxonomy and systematics of each group. We present the challenges faced when studying these organisms and compare methodologies across groups and perspectives in future research.

On the Diversity of Phyllodocida (Annelida: Errantia), with a Focus on Glyceridae, Goniadidae, Nephtyidae, Polynoidae, Sphaerodoridae, Syllidae, and the Holoplanktonic Families

Phyllodocida is a clade of errantiate annelids characterized by having ventral sensory palps, anterior enlarged cirri, axial muscular proboscis, compound chaetae (if present) with a single ligament, and of lacking dorsolateral folds. Members of most families date back to the Carboniferous, although the earliest fossil was dated from the Devonian. Phyllodocida holds 27 well-established and morphologically homogenous clades ranked as families, gathering more than 4600 currently accepted nominal species. Among them, Syllidae and Polynoidae are the most specious polychaete groups. Species of Phyllodocida are mainly found in the marine benthos, although a few inhabit freshwater, terrestrial and planktonic environments, and occur from intertidal to deep waters in all oceans. In this review, we (1) explore the current knowledge on species diversity trends (based on traditional species concept and molecular data), phylogeny, ecology, and geographic distribution for the whole group, (2) try to identify the main knowledge gaps, and (3) focus on selected families: Alciopidae, Goniadidae, Glyceridae, Iospilidae, Lopadorrhynchidae, Polynoidae, Pontodoridae, Nephtyidae, Sphaerodoridae, Syllidae, Tomopteridae, Typhloscolecidae, and Yndolaciidae. The highest species richness is concentrated in European, North American, and Australian continental shelves (reflecting a strong sampling bias). While most data come from shallow coastal and surface environments most world oceans are clearly under-studied. The overall trends indicate that new descriptions are constantly added through time and that less than 10% of the known species have molecular barcode information available.

The Early Branching Group of Orbiniida Sensu Struck et al., 2015: Parergodrilidae and Orbiniidae

This review addresses the state of the art of the systematics and the improvements in the biology, ecology and species diversity of the two annelid taxa Parergodrilidae and Orbiniidae, the early branching group of Orbiniida sensu Struck et al., 2015 according to molecular studies. An effort to identify gaps of knowledge is given to understand the distribution, dispersal and the diversity Parergodrilidae and Orbiniidae hold, as well as to give several directions for future research. Parergodrilidae is a taxon of interstitial annelids constituted by the terrestrial Parergodrilus heideri (monotypic genus up to date), reported throughout Europe but also in Korea and North America, and the genus Stygocapitella, which includes eleven species from the upper shore of sandy beaches distributed along Europe and other regions of the world. Orbiniidae contains more than 200 described species spread over 20 valid genera, varying in size from a few millimeters up to 30 cm, distributed globally and living in a wide variety of soft bottoms. Improving the knowledge on these two sister-taxa is crucial for the understanding of the evolution to interstitial forms by progenesis in Annelida.

A new species of Pista Malmgren, 1866 (Polychaeta, Terebellidae) from the north-western Mediterranean Sea

A new species of Terebellidae, Pistacolinisp. n., has been identified from the harbour of Banyuls-sur-Mer, north-western Mediterranean Sea. This new species was found in very high densities, exclusively in gravelly sand deposited manually, and was not found in the original source habitat of the gravel. This species is characterized by the colour of the ventral shields with pinkish anterior part and a blood red posterior part in live specimens, a pair of unequal-sized plumose branchiae inserted on segment II and anterior thoracic neuropodia with long-handled uncini. The presence of long-handled uncini even in the smallest specimens constitutes the major difference between Pistacolinisp. n. and other Pista species with a single pair of branchiae such as P.lornensis and P.bansei.