Nemertea is a phylum of predominantly marine worms that exhibit various larval forms, including the iconic pilidium. Pelagic lecithotrophic pilidia are considered more derived than pelagic planktotrophic pilidia, but data on the structure of lecithotrophic larvae are limited to the light-optical level. Here, we study the lecithotrophic reversed Iwata's larvae of an undescribed heteronemertean, Nipponomicrura sp. Using transmission electron microscopy and confocal laser scanning microscopy with F-actin, acetylated α-tubulin, and serotonin (5-hydroxytryptamine) labeling, the provisional structures of the larva are described. The larval envelope of Nipponomicrura sp. consists of three layers: the epidermis, the circular musculature, and the epithelium of the amnion. The larval epidermis contains a considerable amount of yolk, only half of which is consumed by the end of metamorphosis. The apical plate consists of 5-hydroxytryptamine-negative cells, each bearing a cilium surrounded by a collar of eight to nine microvilli. Four monociliated 5-hydroxytryptamine-like-immunoreactivity sensory apical neurons are associated with the apical plate. For the first time, a pair of longitudinal muscles running along the body of the juvenile and joining the anterior and posterior parts of the provisional epithelium has been identified in nemertean larvae. These muscles serve as retractors of the apical plate and fix the position of the juvenile within the larva. The obtained data indicate a similar morphology of the apical organ in Pilidiophora larvae; however, in the Nipponomicrura sp. larva, there are more layers under the apical plate, and the muscle-retractor is derived from two longitudinal muscle cords that pass through the juvenile's body, and in posterior pole, attach at the base of the larval envelope.

Tetrodotoxin (TTX) is an extremely potent neurotoxin, a selective blocker of voltage-gated sodium (NaV) channels, produced by bacteria and accumulated across a wide range of taxa. Several TTX-bearing animals have developed molecular adaptations in their NaV channels that provide TTX resistance, making this toxin one of the factors of molecular evolution. However, the molecular basis of TTX resistance in NaV channels of a significant proportion of tetrodotoxic species remains poorly studied. Nemertea is a phylum of marine worms, comprising both TTX-bearing and non-TTX-bearing species. Here, we analyzed the amino acid sequences of the NaV1 channel regions responsible for TTX binding from 22 species of nemerteans. Substitutions previously characterized as conferring TTX resistance in other taxa were detected in sixteen nemerteans; local clustering was observed within several families. These findings suggest that TTX resistance in nemerteans evolved multiple times independently and may serve as either as an adaptation facilitating TTX accumulation for subsequent use for defense and predation, or as a mechanism allowing consumption of tetrodotoxic prey without toxin accumulation.

A digital atlas of every cell in a developing marine worm reveals how networks across the body coordinate sensing and movement, and provides insights into the evolution of the nervous system.

Marphysa moribidii (marine polychaetes) exhibits distinct age-related characteristics based on body width in the initial seven chaetigers, excluding parapodia or bristles that are classified into three age classes: Class Ι (body width ranging from 3–5 mm), Class ΙΙ (6–8 mm), and Class ΙΙΙ (9–11 mm). Despite its potential, the exploration of metabolites in marine worms, particularly through metabolomics, remains limited. The aim of this study is to identify the metabolite profile and depict the metabolic pathways of different age classes of M. moribidii utilising proton nuclear magnetic resonance spectroscopy (1H NMR) metabolomics and liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. A total of 35 metabolites were identified using 1H NMR metabolomics, including amino acids, carbohydrates, fatty acids, glycerol, nitrogenous compounds, organic compounds, and vitamins. LC-MS/MS analysis also discovered 36 metabolites that can be categorised into organic acids, carbohydrates, phenolic compounds, fatty acids, and amino acids. Class II M. moribidii emerged to have the highest concentration of chemicals originating from amino and fatty acids, making it the ideal age for harvesting. Comparing the metabolite profiles across different age groups of M. moribidii could provide valuable insights into its physiological processes, metabolic dynamics, and potential bioactive compounds present at various developmental stages.

Abstract. Iehata S, Hamzah SR, Azmi SS, Ibrahim YS. 2025. Gut microbiome profile of Namalycastis sp. at Setiu wetland in Terengganu, Malaysia. Biodiversitas 26: 358-367. Marine worm regulates the surrounding sediment microbial composition structure and diversity. While there are increasing reports on marine worm-related microbiome assemblage and their functional role in the ecosystem, more knowledge still needs to be reported on the gut microbiome associated with the Nypa worm (Namalycastis sp.). The present study conducted 16S rRNA gene amplicon sequencing to investigate the microbiome community of the Nypa worm gut as well as the environmental sample (rotten Nypa and surrounding water) and analyzed potential microbial functions using functional annotation of prokaryotic taxa (FAPROTAX). Principal coordinates analysis (PCoA) and upset plot results revealed the obvious relationship between microbiome compositions associated with Namalycastis sp. gut and their habitat (Nypa). Similarly, some genera, such as genus Demequina, were found to be in higher abundance in Namalycastis sp. gut and Nypa. This higher abundance could indicate a symbiotic relationship or a specific adaptation to the Nypa environment. Functional predictions based on FAPROTAX indicated that Nypa worms possess higher potentials for aromatic hydrocarbon degradation, aromatic compound degradation, aliphatic non-methane hydrocarbon degradation, and hydrocarbon degradation than environmental samples. The findings in this study suggested that the Nypa worm gut is a reservoir of several beneficial bacteria, such as Rhodococcus and Saccharimonadales, which create a unique microbial environment that facilitates the microbiological degradation of organic compounds. In addition, the genus Rhodococcus and candidatus Xiphinematobacter would become potential biomarkers to monitor the shifting environmental condition of mangroves.

The multifunctional catalytic hemoglobin from the terebellid polychaete Amphitrite ornata, also named dehaloperoxidase (AoDHP), utilizes the typical oxygen transport function in addition to four observed activities involved in substrate oxidation. The multifunctional ability of AoDHP is presently a rare observation, and there exists a limitation for how novel dehaloperoxidases can be identified from macrobenthic infauna. In order to discover more infaunal DHP-bearing candidates, we have devised a facilitated method for an accurate taxonomic identification that places visual and molecular taxonomic approaches in parallel. Traditional visual taxonomic species identification by the non-specialist, at least for A. ornata or even for other marine worms, is a very difficult and time-consuming task since a large diversity is present and the method is restricted to adult worm specimens. The work herein aimed to describe a method that simplifies the taxonomic identification of A. ornata in particular through the assessment of its mitochondrial cytochrome c oxidase subunit I gene by employing the DNA barcoding technique. Furthermore, whole-worm specimens of A. ornata were used to extract and purify AoDHP followed by an H2O2-dependent peroxidase activity assay evaluation against substrate 2,4,6-trichlorophenol. AoDHP isoenzyme A was also overexpressed as the recombinant protein in Escherichia coli, and its peroxidase activity parameters were compared to AoDHP from the natural source. The activity assay assessment indicated a tight correlation for all Michaelis–Menten parameters evaluated. We conclude that the method described herein exhibits a streamlined approach to identify the polychaete A. ornata, which can be adopted by the non-specialist, and the full procedure is predicted to facilitate the discovery of novel dehaloperoxidases from other marine invertebrates.

Serpulid polychaetes are marine worms that secrete calcium carbonate tubes in which they live. Despite extensive previous research on their microstructures, there are no crystallographic data and their biomineralization process remains unclear. Here, the microstructures of the tubes of seven serpulid species were studied, including their chemical composition, mineralogy and crystallography, using X-ray diffraction, Raman and Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, focused ion beam, electron backscatter diffraction, and thermogravimetric analysis. Generally, serpulid tubes have a high amount of organic matter (~ 7.5 wt%), consisting of chitin and proteins, and the calcite is always present as medium to high magnesium calcite. Three main microstructures were identified: granular-prismatic and lamello-fibrillar calcite, and fibrous aragonite. They all displayed an axial texture, which is stronger in the lamello-fibrillar calcite, with the c-axis aligned with the elongation axis of the crystals. These findings demonstrate that only some instances of the granular-prismatic and the lamello-fibrillar calcite are biogenic (primary) microstructures. Conversely, other instances of the granular-prismatic calcite and the fibrous aragonite are a consequence of a recrystallization process (i.e. secondary). Replacement may occur on either primary or secondary calcitic microstructures (replaced by aragonite). Secondary microstructures retain remnants of the previously replaced microstructures, such as vestigial crystals or major growth increments. The high-Mg nature of the calcite favors recrystallization. The plywood arrangement of the lamello-fibrillar calcite is hypothesized to result from the ordering of a chitin fibrillar precursor into a cholesteric liquid crystal phase, with the calcite subsequently growing by oriented nucleation onto the organic fibrils.

The present paper deals with Bar-toothed nereid, Perinereis nuntia (Lamarck, 1818), a first record from the state of West Bengal, India, based on 21 specimens collected from the Digha coast. This marine worm’s morphological characteristics, such as paragnaths and setae arrangements, jaw structure, and head morphology, agree well with those of the previous original description and the number of paragnaths of the proboscis. The present study contributes to the knowledge of Indian polychaete, providing taxonomic descriptions of this species with detailed accounts of their distribution.

Alzheimer's disease (AD) is a severe and high costs health problem all over the world. To date, there is no therapy capable of curing AD, making drug discovery a challenging and intriguing field to explore. Targeting marine natural products (MNPs) as a source of drug leads is a suitable choice considering the content of bioactive compounds and promising pharmacological benefits. This article aims to look at MNPs with prospects in several prime targets in AD pathology to cure AD. Marine vertebrates (fishes), marine invertebrates (sponges, tunicates, ascidian, clams, scallops, sand dollars, crabs, cockle, sea cucumber, shrimp, bryozoa, marine worm), algae/seaweed, and marine microorganisms (marine fungi, bacterium, dinoflagellata, microalgae) can be potentially used as disease-modifying treatments (DMTs) for AD. By targeting multiple aspects of AD pathology, these MNPs offer a multifaceted approach to treating and potentially modifying the disease course. This result is an intriguing gap for researchers in the discovery and development of new drugs that can improve AD pathology.

Unusual polyunsaturated fatty acids in edible marine worms identified by covalent adduct chemical ionization mass spectrometry

Hexavalent chromium damages intestinal cells and coelomocytes and impairs immune function in the echiuran worm Urechis unicinctus by causing oxidative stress and apoptosis

To date, polychaetes remain a poorly studied class of invertebrate animals in the context of clarification of their immune system functioning and, in particular, of antimicrobial peptides (AMPs) biodiversity. AMPs, also known as host defense peptides, play a key role in host protection from various pathogens and regulation of the species composition of symbiotic microbes. The study of biosynthesis of AMPs in polychaetes has revealed an interesting pattern, namely so-called BRICHOS domain in the precursor proteins of a number of such peptides. The conserved structure of this domain allows to perform a bioinformatic search for AMP precursors in polychaete transcriptomes. In this work, we found and studied a new BRICHOS-associated AMP from the lugworm Arenicola marina, which represents a structural family of defensin-like peptides stabilized by four disulfide bonds, not previously identified in marine worms. The peptide, designated as AmBRI-44a, contained 44 amino acid residues and was obtained by heterologous expression in Escherichia coli. AmBRI-44a was shown to have a specific activity against a narrow spectrum of Gram-positive bacteria and did not exhibit pronounced cytotoxic effects on eukaryotic cell line HEK293T. A potential mechanism of the antibacterial action of this peptide may be associated with inhibition of bacterial cell wall biosynthesis, as indicated by genetic and phenotypic analysis of selected AmBRI-44a-resistant bacteria Bacillus licheniformis B-511. The results obtained allow us to consider the novel peptide AmBRI-44a as a candidate compound for the development of an antibiotic agent that could potentially be effective in the treatment of infectious diseases mediated by multidrug-resistant Gram-positive bacteria.

The escalating resistance of agricultural pests to chemical insecticides necessitates the development of novel, efficient, and safe biological insecticides. Conus quercinus, a vermivorous cone snail, yields a crude venom rich in peptides for marine worm predation. This study screened six α-conotoxins with insecticidal potential from a previously constructed transcriptome database of C. quercinus, characterized by two disulfide bonds. These conotoxins were derived via solid-phase peptide synthesis (SPPS) and folded using two-step iodine oxidation for further insecticidal activity validation, such as CCK-8 assay and insect bioassay. The final results confirmed the insecticidal activities of the six α-conotoxins, with Qc1.15 and Qc1.18 exhibiting high insecticidal activity. In addition, structural analysis via homology modeling and functional insights from molecular docking offer a preliminary look into their potential insecticidal mechanisms. In summary, this study provides essential references and foundations for developing novel insecticides.

First vertebrate BRICHOS antimicrobial peptides: β-hairpin host defense peptides in limbless amphibia lung resemble those of marine worms

Sipuncula are marine unsegmented worms that can be found in benthic habitats, from shallow to deep-sea waters. In Mexico these worms have been scarcely studied. Among nine studies in the entire Mexican Pacific coasts, seven are from the central and northwestern Mexican Pacific. For over 80 years, only 24 species have been recorded. To improve the knowledge of the sipunculans from the central and northwestern Mexican Pacific, 501 specimens from three scientific collections of Mexico were revised. The specimens were collected by diverse methods from intertidal, subtidal, and bathyal depths (~1000 m), from 27 locations along the central and northwestern Mexican Pacific. Sixteen taxa belonging to nine genera and five families were identified. One species is recorded for the first time in the Mexican Pacific and five new species are described, one from intertidal and shallow subtidal depths: Phascolosoma (Phascolosoma) azteca sp. nov.; two from subtidal depths: Phascolion (Lesenka) salgadoi sp. nov. and Sipunculus (Sipunculus) bastidai sp. nov.; and two from bathyal depths: Apionsoma (Apionsoma) silviae sp. nov. and Apionsoma (Edmondsius) hendrickxi sp. nov.

In Mexico, there are six scientific collections of polychaetous annelids. The "Colección Poliquetológica" from the Universidad Autónoma de Nuevo León houses one of the three most important collections of annelids in the country, based on a number of lots and number of type materials deposited, as well as geographical coverage. A catalogue of type materials of polychaete annelids housed at the "Colección Poliquetológica" from the Universidad Autónoma de Nuevo León (México) is presented for the first time. The Collection contains 37 holotypes, 174 paratypes and one syntype. These type materials are grouped in 15 families, 35 genera and 54 species of marine worms. Types were described mostly from the Mexican waters, with a low number of types from Ecuador, El Salvador, Argentina, USA, Philippines, New Caledonia and Japan.

Nusa Tenggara is a traditional ritual that is carried out once a year with the aim of catching indigenous Nyale worms in its coastal waters. Nyale sea worms are members of the Annelida phylum which have been identified around 9,000 species and mostly consist of 8,000 species of Polychaeta. Nyale worms are also known by many names, including Pyak worms, Laor worms and sea worms in general. The Kendari coastal community believes in consuming sea worms as a traditional medicine, because some of the chemical compounds present in sea worms are thought to have properties that contain high protein content with efficacious properties for treating various diseases. The amino acids of sea worms consist of 2 types of acids, namely essential amino acids and non-essential amino acids which consist of 15 subindicators of amino acids. The highest essential amino acid is found in arginine, namely, 7355.37 ± 7.21. in fresh marine worms while in freeze dry marine worms that is 2537.55 ± 1.46.

Comparative analysis of the cytoarchitecture of the excretory bladder of adult Digenea (Platyhelminthes) with consideration of the presence of mineralized excretory corpuscles in marine and freshwater adult worms

Nonspecific immune, histology and accumulation of marine worm, Urechis unicinctus in response to bisphenol A (BPA)

Echiura is a distinctive family of unsegmented sausage-shaped marine worms whose phylogenetic relationship still needs strong evidence from the phylogenomic analysis. In this family, Urechis unicinctus is known for its high nutritional and medicinal value and adaptation to harsh intertidal conditions. Herein, we combined PacBio long-read, short-read Illumina and Hi-C sequencing, generating a high-quality chromosome-level genome assembly of U. unicinctus. The assembled genome spans ~1,138.6 Mb with a scaffold N50 of 68.3 Mb, of which 1,113.8 Mb (97.82%) were anchored into 17 pseudo-chromosomes. The BUSCO analysis demonstrated the completeness of the genome assembly and gene model prediction are 93.5% and 91.5%, respectively. A total of 482.1 Mb repetitive sequences, 21,524 protein-coding genes, 1,535 miRNAs, 3,431 tRNAs, 124 rRNAs, and 348 snRNAs were annotated. This study significantly improves the quality of U. unicinctus genome assembly, sets the footsteps for molecular breeding and further study in genome evolution, genetic and molecular biology of U. unicinctus.