FoxA expression pattern in two polychaete species, Alitta virens and Platynereis dumerilii: Examination of the conserved key regulator of the gut development from cleavage through larval life, postlarval growth, and regeneration.

BACKGROUND: foxA orthologs are involved in various processes from embryo patterning to regulation of metabolism. Since foxA conserved role in the development of the gut of errant annelids has never been thoroughly studied, we used a candidate gene approach to unravel the molecular profile of the alimentary canal in two closely related nereid worms with a trochophore-type lecithotrophic larva. RESULTS: The character of foxA expression in the two polychaetes was similar but not identical. The genes were successively activated first in blastoporal cells, then in the stomodeum, the midgut, and hindgut primordia, and in the cells of central and peripheral nervous system. Before the start of active feeding of nectochaetes, we observed a short phase of foxA expression in the entire digestive tract. After amputation of posterior segments, foxA expression was established de novo in the new terminal part of the intestine, and then in the developing hindgut and the anus. CONCLUSIONS: We discovered an early marker of endoderm formation previously unknown in errant annelids. Its expression dynamics provided valuable insights into the gut development. Comparative analysis of foxA activity suggests its primary role in gastrulation morphogenesis independently of its type and in midgut and foregut specification. Developmental Dynamics 248:728-743, 2019. © 2018 Wiley Periodicals, Inc.

Description of a New Species for Asian Populations of the "Cosmopolitan" Perinereis cultrifera (Annelida: Nereididae).

An Asian species of Perinereis, which has been regarded as a local population of a cosmopolitan species P. cultrifera ( Grube, 1840 ) (type locality: Italy), is described as a new species, P. euiini., based on Korean specimens. This new species is distinguishable from P. cultrifera and other similar species such as P. floridana ( Ehlers, 1868 ) (type locality: USA), P. anderssoni Kinberg, 1866 (type locality: Brazil), and P. helleri ( Grube, 1878 ) (type locality: Philippines) by the character combination of the absence of lateral group of paragnaths in area III on the proboscis, the presence of small notopodial prechaetal lobe in anterior parapodia, and the greatly expanded dorsal ligule in posterior parapodia. All previous records of "P. cultrifera" from eastern Asia (Taiwan, China, Japan, and Korea) are judged to belong to P. euiini sp. nov., leading to the conclusion that P. cultrifera is not a cosmopolitan species. Specimens previously identified as P. cultrifera var. floridana (or P. cultrifera floridana) in eastern Asia are also judged to belong to P. euiini sp. nov., although they have different paragnath number in area V (one instead of three). Their aberrant paragnath number was regarded as an intraspecific variation of P. euiini sp. nov. The comparison of DNA sequences of the mitochondrial cytochrome c oxidase subunit I (COI) between P. euiini sp. nov. and "P. cultrifera" from China and Portugal also supports the erection of the new species.

Molecular Evidence for the Expansion of the Asian Cryptic Invader Hediste diadroma (Nereididae: Annelida) into the Northeast Pacific Habitats of the Native H. limnicola.

We used previously established molecular methods to determine how far the Asian invader nereidid worm Hediste diadroma has spread into northeast Pacific estuaries that are inhabited by the native congener H. limnicola. Further, we analyzed the mitochondrial DNA of 702 Hediste specimens collected from 27 estuaries along 1,350 km of coastline in Washington, Oregon, and California, USA, to distinguish between the morphologically indistinguishable immature stages of these two species. In total, 377 specimens were identified as the invader H. diadroma and 325 were identified as the native H. limnicola. The invader H. diadroma was dominant at many sites in Puget Sound, Washington, and in the Columbia River estuary, Washington, and Oregon, suggesting that this species initially invaded estuaries in Washington or northern Oregon. In contrast, the native H. limnicola was dominant at intertidal sites in California and at subtidal sites in the Columbia River estuary. We also analyzed a partial nucleotide sequence from the mitochondrial cytochrome oxidase subunit I gene of H. diadroma in specimens collected from seven sites in the US and 11 sites in Japan, which showed no marked geographic differentiation between 18 US and 31 Japanese haplotypes. This finding suggests that H. diadroma have been introduced repeatedly into US estuaries from many regions in Japan.

A whole-body transcriptome assembly of the annelid worm Hediste diversicolor.

The Annelida phylum is composed of a myriad of species exhibiting key phenotypic adaptations. They occupy key ecological niches in a variety of marine, freshwater and terrestrial ecosystems. Importantly, the increment of omic resources is rapidly modifying the taxonomic landscape and knowledge of species belonging to this phylum. Here, we comprehensively characterised and annotated a transcriptome of the common ragworm, Hediste diversicolor (OF Müller). This species belongs to the family Nereididae and inhabits estuarine and lagoon areas on the Atlantic coasts of Europe and North America. Ecologically, H. diversicolor plays an important role in benthic food webs. Given its commercial value, H. diversicolor is a promising candidate for aquaculture development and production in farming facilities, under a circular economy framework. We used Illumina next-generation sequencing technology, to produce a total of 105 million (M) paired-end (PE) raw reads and generate the first whole-body transcriptome assembly of H. diversicolor species. This high-quality transcriptome contains 69,335 transcripts with an N50 transcript length of 2313 bp and achieved a BUSCO gene completeness of 97.7% and 96% in Eukaryota and Metazoa lineage-specific profile libraries. Our findings offer a valuable resource for multiple biological applications using this species.

Complete mitochondrial genome of the ragworm annelid Hediste diversicolor (of Müller, 1776) (Annelida: Nereididae).

Marine annelids are a globally distributed and species-rich group, performing important ecological roles in macrobenthic communities. Yet, the availability of molecular resources to study these organisms is scarcer, comparatively with other phyla. Here, we present the first complete mitogenome of the Atlantic ragworm Hediste diversicolor (OF Muller, 1776). The mitogenome (15,904 bp long) contains 13 protein-coding genes, 22 transfer RNA, and two ribosomal RNA genes, all encoded in the same strand. Gene arrangement and composition are identical to those observed in two available congeneric species, Hediste diadroma and Hediste japonica. The phylogenetic analysis using both maximum-likelihood and Bayesian inference methods reveal a well-supported monophyly of genus Hediste and the already reported paraphyletic relationships within the subfamilies Nereidinae and Gymnonereidinae. Our results highlight the relevance of increasing the molecular sampling within this diverse group of marine fauna.

Complete mitochondrial genome of the marine polychaete, Nereis zonata (Phyllodocida, Nereididae) isolated from the Beaufort Sea.

Here, we present the first whole mitogenome sequence of the marine polychaete, Nereis zonata, isolated from the Beaufort Sea. The mitochondrial genome of N. zonata is 15,757 bp in length and consists of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and a non-coding region that is typical of polychaetes. GC content of the N. zonata mitogenome is 37.2%. A maximum-likelihood gene tree based on the N. zonata mitogenome combined with previously published annelid mitogenome data revealed that N. zonata is clustered with Cheilonereis cyclurus, which form a sister group to Nereis sp.

Two new species of nereidids (Annelida, Polychaeta) from Taiwan.

Two new species of nereidids, Dendronereis chipolini n. sp. and Neanthes hsinchuensis n. sp., collected from brackish aquaculture ponds near coasts of southern Taiwan and fouling community on docks of the Hsinchu fishing port in northwestern Taiwan, respectively, are described in the present study. Dendronereis chipolini n. sp. differs from its congeners by a combination of number and morphology of branchiae, morphology of neuropodia and form of neuropodial homogomph spinigers. Neanthes hsinchuensis n. sp. can be distinguished from congeners reported from East and Southeast Asia by a combination of numbers of conical paragnaths, morphology of notopodia, the absent/present of prechaetal lobe and forms of neuropodial chaetae. A key to Dendronereis species of the world is included, together with a table of morphological characters of Neanthes species reported from East and Southeast Asia, which have no conical paragnaths on Area V of the pharynx.

Spatio-temporal trends and body size differences of OCPs and PCBs in Laeonereis culveri (Polychaeta: Nereididae) from Southwest Atlantic estuaries.

Southwest Atlantic (SWA) estuaries have been historically impacted by industrial and agricultural activities that represent an important source of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs). Intraspecific differences in OCPs and PCBs levels were evaluated in the benthic polychaete Laeonereis culveri from SWA estuaries (Samborombón; Mar Chiquita; Quequén Grande and Bahía Blanca) at different spatio-temporal scales. Regarding inter- and intra-estuarine spatial comparisons polychaetes showed significant differences in OCPs/PCBs levels (p < 0.05) being DDTs, endosulfan, penta- and hexa-CBs homologues the most representative compounds. Intra-estuarine comparisons also showed significant differences in terms of seasonality and body size (p < 0.05). OCPs/PCBs concentrations were negatively correlated with animal weight, but this covariable was not relevant on differences observed. OCPs/PCBs levels in polychaetes showed strong relationships with those of sediments, being suitable for estuarine biomonitoring studies. Seasonal and body-size differences found in OCPs and PCBs levels in tissues reveal the importance of these factors for intra-estuarine monitoring.

Determination of complete mitogenome sequence for Eastern Asian population of Cheilonereis cyclurus (Harrington, 1897) (Polychaeta: Nereididae).

Complete mitogenome sequence for eastern Asian population of Cheilonereis cyclurus (Polychaeta: Nereididae) was determined for the first time. The length of circular genome of C. cyclurus is 14,917 bp including 13 protein-coding genes, two rRNA genes, 22 tRNA genes, and a non-coding region of 383 bp. The gene order of C. cyclurus is identical to that of the following four nereidid species: Hediste diadroma, Namalycastis abiuma, Paraleonnates uschakovi, Tylorrhynchus heterochaetus. The phylogenetic position of C. cyclurus compared to 16 selected polychaetes was conducted and present species is closely related to the clade containing Perinereis nuntia, P. aibuhitensis, and Platynereis dumerilii with high bootstrap value.

The complete mitochondrial genome of epitokous Nereis species (Phyllodocida, Nereididae) from Dok-do, Korea.

The mitogenome sequence of the epitokous Nereis species (Phyllodocida, Nereididae) was determined first in the genus Nereis. The complete mitogenome is 15,667 bp in length, containing 13 protein-coding genes, two ribosomal RNAs, 22 transfer RNAs and a control region, and their gene order and structure is identical to those of other nereidid species. The mitogenome consists of 33.5% A, 20.0% C, 13.3% G, 33.1% T, showing a high content of A + T similar to the other phyllodocid polychaetes. These results will be useful for inferring the phylogenetic relationships among the members of Nereididae within the phyllodocids.

A new species of Websterinereis from the Gulf of California and redescription of Websterinereis foli (Fauvel, 1930) (Annelida, Nereididae).

A new species of Websterinereis Pettibone, 1971, Websterinereis pettiboneae sp. n. is described from La Paz Bay, Gulf of California, Mexico. This species is similar to Websterinereis foli (Fauvel, 1930) in the neuropodial falcigers shape, but can be separated by the tentacular cirri length, notopodial prechaetal lobe shape, and the size of the notopodial dorsal and ventral ligules on posterior parapodia. Websterinereis foli is redescribed based upon type material. Additional observations on the inter-annual density variation of Websterinereis pettiboneae sp. n. during a four-year study are also provided. A key to all species of Websterinereis is included.

Mitochondrial genome of the polychaete Tylorrhynchus heterochaetus (Phyllodocida, Nereididae).

We firstly reported the complete mitochondrial genome (mitogenome) of the polychaete Tylorrhynchus heterochaetus. Illumina next-generation sequencing generated a total of 19,796 reads with an average depth of 122.91×. The mitogenome is 16,106 bp in length including the typical structure of 13 protein coding genes, two rRNA genes, 22 tRNA genes and a putative control region. However, T. heterochaetus differs from other Nereididae species in the positions of four genes (tRNA-Met, tRNA-Asp, ATP8, tRNA-Tyr). All 37 genes are encoded on the heavy strand whose nucleotide composition is 32.20 % A, 13.67% C, 21.33% G and 32.80% T.

The complete mitochondrial genome of the marine polychaete: Hediste diadroma (Phyllodocida, Nereididae).

The mitogenome sequence of a polychaete Hediste diadroma (Phyllodocida, Nereididae) was determined first in the genus Hediste. The circular genome is 15,765bp in size including 13 protein-coding genes (PCGs), 2 rRNA and 22 tRNA of which the order and structure is same as those of other Nereididae species. All PCGs use ATG as the start codon while for the stop codon, COI, ND5 and ND1 use an incomplete codon of T. The genome consists of 32.4% A, 18.2% C, 14.2% G, 35.2% T, showing a high content of A + T similar to the other Phyllodocid polychaetes.

Complete mitochondrial genome sequence of the giant mud worm Paraleonnates uschakovi Khlebovich & Wu, 1962 (Polychaeta: Nereididae).

Complete mitochondrial genome sequence of the giant mud worm Paraleonnates uschakovi (Polychaeta: Nereididae) was determined in this study for the first time. The mitogenome of P. uschakovi is 15,540 bp in length. It has 13 protein-coding genes, two rRNA genes, 22 tRNA genes and a non-coding region. Mitogenome analysis of P. uschakovi showed inversion in the positions of three tRNAs compared to the mitogenome sequences of Perinereis aibuhitensis, P. nuntia and Platynereis dumerilii. The phylogenetic position of P. uschakovi compared to 15 selected polychaetes was investigated. P. uschakovi was grouped into the family of Nereididae. It is closely related to the clade containing Tylorrhynchus heterochaetus and Namalycastis abiuma.

The complete mitochondrial genome of the marine polychaete: Perinereis aibuhitensis (Phyllodocida, Nereididae).

We determined the complete mitochondrial genome sequence of the marine polychaete Perinereis aibuhitensis (Grube, 1878) (Phyllodocida, Nereididae), a dominant species in the mudflat of the West Pacific and Indian Ocean. The complete genome of P. aibuhitensis is 15,852 bp in size including 13 protein coding genes (PCGs), 2 rRNA and 22 tRNA with the same gene order and structure as those of other Nereididae species. The nucleotide composition is 29.5% A, 21.2% C, 14.1% G, 35.2% T, showing a high content of A+T with G being used least in the third codon position (6.7%). All PCGs use ATG as the start codon while for the stop codon COI and ND1 use incomplete codon of T. The mitogenome sequence of P. aibuhitensis is second to that of P. nuntia known in the genus Perinereis, which will provide useful information for understanding evolutionary history of the genus Perinereis within the family Nereididae.

A new species of Nicon Kinberg, 1866 (Polychaeta, Nereididae) from Ecuador, Eastern Pacific, with a key to all known species of the genus.

A new species of Nicon Kinberg, 1866 from the east Pacific coast of Ecuador is described. The new species is characterized by a long, thin dorsal ligule on median and posterior parapodia and infracicular sesquigomph falcigers in the neuropodia. A key to all species of Nicon is provided.

A new species of Perinereis (Polychaeta, Nereididae) from Florida, USA, with a key to all Perinereis from the American continent.

Specimens belonging to a new species of Perinereis Kinberg, 1865 were collected fromnatural oyster reefs in an estuarine environmenton Florida's southwest coast. The genus Perinereis includes more than 70 species, of which, Perinereis aibuhitensis (Grube, 1878), Perinereis brevicirrata (Treadwell, 1920), Perinereis camiguinoides (Augener, 1922), Perinereis jascooki Gibbs, 1972, Perinereis kuwaitensis Mohammad, 1970, Perinereis singaporiensis (Grube, 1878), Perinereis vancaurica (Ehlers, 1868) and the new species have two short bars on Area VI and notopodial dorsal ligules that are not greatly expanded. The most geographically close species is Perinereis brevicirrata. The new species can be distinguished from Perinereis brevicirrata by the absence of a notopodial prechaetal lobe, Area V with 3 cones in a triangle, and Area VII-VIII with two well-defined rows of 33 paragnaths, the basal row having longer paragnaths in relation to the distal ones. The new species resembles Perinereis singaporiensis based on the absence of notopodial prechaetal lobe; however, the two species differ in some morphological characteristics such as tentacular cirri length, shape of dorsal notopodial ligules, and falciger blades. A key to all American species of Perinereis is included.

Description and phylogeny of Namalycastis jaya sp. n. (Polychaeta, Nereididae, Namanereidinae) from the southwest coast of India.

Namalycastis jayasp. n. (Polychaeta: Nereididae: Namanereidinae)is described from the southern coast of Kerala in southwest India. One important characteristic feature of the species is the lack of notochaetae in all parapodia, a characteristic that it shares with at least two other species, Namalycastis elobeyensis Glasby, 1999and Namalycastis hawaiiensis Johnson, 1903. It differs from Namalycastis elobeyensis by virtue of its smaller antennae, unequal eye size, bilobed acicular neuropodial ligule and multi-incised pygidium rim. Moreover, it differs from Namalycastis hawaiiensis by having fewer teeth on the serrated blades of the sub-neuroacicular falciger in chaetiger 10, and by possessing finely serrated falcigers in posterior segments. Beyond morphological analyses, molecular phylogenetics was used for the first time for Namalycastis to support population monophyly and recognition of the new species.The analysis, using both mitochondrial and nuclear data, corroborated the morphological analysis in suggesting that our specimens represent an as yet undescribed species, Namalycastis jayasp. n., which forms a monophyletic group among the sampled nereidid taxa. Finally, a taxonomic key for Namalycastis species recorded from the Indian region is provided.

Some Nereididae (Annelida: Polychaeta) from the Pacific Coast of Costa Rica

Fifteen species of Nereididae (Annelida: Polychaeta) belonging to nine genera are reported from the subtidal and intertidal of the Pacific Coast of Costa Rica. A new species, Nereis costaricaensis, is described. Laeonereis brunnea Hartmann-Schrõder 1959 is removed from synonomy with L. culveri (Webster 1880) while Perinereis seridentata (Hartmann-Schrõder 1959) is moved from the genus Neanthes based upon the presence of bar-shaped paragnaths on area VI of the proboscis. The presence of Neanthes micromma Harper 1979 is an extension of the range of this species from the Gulf of California and Neanthes roosevelti Hartman 1939 is the first record of this species since its description from the Galapagos. A taxonomic key to these nereidid species is included.