A New Species of Branchellion (Hirudinea: Piscicolidae) Parasitizing the Gills of Short-Tail Stingrays (Batoidea: Dasyatidae) from the West Pacific.

A new fish leech, Branchellion brevicaudatae sp. n., is described based on specimens parasitizing the gills of the short-tail stingray, Bathytoshia brevicaudata (Hutton, 1875), collected from Japanese waters. The new species can be distinguished from other congeners by having: i) pulsating vesicles emerging from posterior base of branchiae, one pair per somite; ii) dorsal white spots, not arranged in longitudinal row; and iii) blackish body. A phylogenetic tree based on partial sequences of the mitochondrial cytochrome c oxidase subunit I gene from the new species and other piscicolid worms showed that the new species is sister to Branchellion torpedinis Savigny, 1822. This is the first record of Branchellion Savigny, 1822 from Japanese waters.

Metachromins X and Y from a marine sponge Spongia sp. and their effects on cell cycle progression.

New sesquiterpene quinones, metachromins X (1) and Y (2), together with the known metachromins C (3), J (4), and T (5), were isolated as inhibitors of cell cycle progression in the HeLa/Fucci2 cells. The structure of 1 was assigned by spectroscopic data and confirmed by a total synthesis. The planar structure of 2 was determined by interpretation of spectroscopic data, whereas its absolute configuration was analyzed by a combination of chiral HPLC and CD spectroscopy. Metachromins X (1) and C (3) arrested the cell cycle progression of HeLa/Fucci2 cells at S/G2/M phase.

A new genus and species of nudibranch-mimicking Syllidae (Annelida, Polychaeta).

Nudibranch mollusks, which are well-known for their vivid warning coloration and effective defenses, are mimicked by diverse invertebrates to deter predation through both Müllerian and Batesian strategies. Despite extensive documentation across different taxa, mimickers have not been detected among annelids, including polychaetes, until now. This study described a new genus and species of polychaete living on Dendronephthya octocorals in Vietnam and Japan. Belonging to Syllidae, it exhibits unique morphological adaptations such as a low number of body segments, simple chaetae concealed within the parapodia and large and fusiform antennae and cirri. Moreover, these appendages are vividly colored, featuring an internal dark red area with numerous terminal white spots and bright yellow tips, effectively contributing to mimicking the appearance of a nudibranch. This discovery not only documents the first known instance of such mimicry among annelids, but also expands our understanding of evolutionary adaptation and ecological strategies in marine invertebrates.

Two new species of Parahesione (Annelida: Hesionidae) associated with ghost shrimps (Crustacea: Decapoda) and their phylogenetic relationships.

Two new species of Hesionidae, Parahesione pulvinata sp. nov. and Parahesione apiculata sp. nov. are described based on materials collected at tidal flats in Okinawa (Japan) from burrows of the ghost shrimps Neocallichirus jousseaumei and Glypturus armatus. The two new species are characterized by having eight enlarged cirri, dorsal cirrophores with dorsal foliose lobe and biramous parapodia, and by lacking median antenna. Parahesione apiculata sp. nov. has digitate lobes on the posterior margin of the dorsal foliose lobe (absent in P. pulvinata sp. nov.). The two new species were never found outside the ghost shrimp burrows, suggesting they are obligate symbionts. Phylogenetic analyses based on four concatenated genes suggest that the symbiotic lifestyle has evolved several times in Hesionidae.

Investigating the diversity of bioluminescent marine worm Polycirrus (Annelida), with description of three new species from the Western Pacific.

Bioluminescence, a phenomenon observed widely in organisms ranging from bacteria to metazoans, has a significant impact on the behaviour and ecology of organisms. Among bioluminescent organisms, Polycirrus, which has unique emission wavelengths, has received attention, and advanced studies such as RNA-Seq have been conducted, but they are limited to a few cases. In addition, accurate species identification is difficult due to lack of taxonomic organization. In this study, we conducted comprehensive taxonomic survey of Japanese Polycirrus based on multiple specimens from different locations and described as three new species: Polycirrus onibi sp. nov., P. ikeguchii sp. nov. and P. aoandon sp. nov. The three species can be distinguished from the known species based on the following characters: (i) arrangement of mid-ventral groove, (ii) arrangement of notochaetigerous segments, (iii) type of neurochaetae uncini, and (iv) arrangement of nephridial papillae. By linking the bioluminescence phenomenon with taxonomic knowledge, we established a foundation for future bioluminescent research development. We also provide a brief phylogenetic tree based on cytochrome c oxidase subunit I (COI) sequences to discuss the evolution of bioluminescence and the direction of future research.

Impact of the citizen science project COLLECT on ocean literacy and well-being within a north/west African and south-east Asian context.

Plastic pollution is both a societal and environmental problem and citizen science has shown to be a useful tool to engage both the public and professionals in addressing it. However, knowledge on the educational and behavioral impacts of citizen science projects focusing on marine litter remains limited. Our preregistered study investigates the impact of the citizen science project Citizen Observation of Local Litter in coastal ECosysTems (COLLECT) on the participants' ocean literacy, pro-environmental intentions and attitudes, well-being, and nature connectedness, using a pretest-posttest design. A total of 410 secondary school students from seven countries, in Africa (Benin, Cabo Verde, Côte d'Ivoire, Ghana, Morocco, Nigeria) and Asia (Malaysia) were trained to sample plastics on sandy beaches and to analyze their collection in the classroom. Non-parametric statistical tests (n = 239 matched participants) demonstrate that the COLLECT project positively impacted ocean literacy (i.e., awareness and knowledge of marine litter, self-reported litter-reducing behaviors, attitudes towards beach litter removal). The COLLECT project also led to higher pro-environmental behavioral intentions for students in Benin and Ghana (implying a positive spillover effect) and higher well-being and nature connectedness for students in Benin. Results are interpreted in consideration of a high baseline in awareness and attitudes towards marine litter, a low internal consistency of pro-environmental attitudes, the cultural context of the participating countries, and the unique settings of the project's implementation. Our study highlights the benefits and challenges of understanding how citizen science impacts the perceptions and behaviors towards marine litter in youth from the respective regions.

Two new species of sea cucumbers (Echinodermata: Holothuroidea) from the seagrass meadow of Penang, Malaysia.

Two new species of sea cucumber, Euthyonidiella zulfigaris sp. nov. and Acaudina spinifera sp. nov. were described. The specimens were collected from the seagrass meadow of Pulau Gazumbo and Middle Bank, located east of Penang Island, Malaysia. E. zulfigaris sp. nov. can be distinguished from its congeners based on the presence of table ossicles with round disc, spires formed with four pillars, and absence of modified support tables in tube feet. A. spinifera sp. nov. can be distinguished from its congeners based on the presence of spinose doughnut-shaped ossicles in the body wall.

Worm on worm: Two rare genera of Calamyzinae (Annelida, Chrysopetalidae), with a description of new species.

Marine annelids in the subfamily Calamyzinae (family Chrysopetalidae) are either symbiotic or free-living forms that have been mainly reported from deep-sea chemosynthetic environments. Symbiotic calamyzines predominantly live in the mantle cavity of bivalves distributing at hydrothermal vents or methane seeps except for two species inhabiting the epidermis of polychaetes and octopuses. In this study, we describe a new species, Calamyzas crambon sp. nov., from Japan and report a new record of Nautiliniella calyptogenicola from the Mariana Trench. We also provide the phylogenetic position of the two species within Chrysopetalidae based on four gene markers (COI, 16S, 18S, and H3).

First record of the genus Discorhabdella (Porifera, Demospongiae, Poecilosclerida, Crambeidae) from Sagami Bay, Japan with description of two new species.

Two new species of Discorhabdella are described from Sagami Bay, Japan. Discorhabdella has been suggested to have an ancient Tethyan origin according to discovery of their unique pseudoastrose acanthostyles from late Eocene to Oligocene deposits. This is the first record of the genus from the northwest Pacific and first record of the family Crambeidae from Japan. Discorhabdellahispida sp. nov. is distinctive within the genus by possession of special sigmoid microscleres and C-shaped isochelae with short alae. Discorhabdellamisakiensis sp. nov. is characterized by short choanosomal subtylostyles, and their length overlapped with that of the ectosomal subtylostyles. Only one other species, Discorhabdellatuberosocapitata (Topsent, 1890), has the same spicule composition. However, all spicule types are larger in D.tuberosocapitata than those of D.misakiensis sp. nov., and the shape of the isochelae is different: the alae are more widely opened in D.tuberosocapitata. An identification key to species of the genus Discorhabdella is also provided. The discovery of two new species from warm temperate northwest Pacific extends the geographical distribution of the genus Discorhabdella.

First record of Hamacantha (Porifera, Demospongiae, Merliida, Hamacanthidae) from Japan, with description of two new species.

Two new species of thinly encrusting sponge Hamacantha (Demospongiae, Merliida, Hamacanthidae) are described from Japan. Hamacantha (Vomerula) mamoi sp. nov. was collected from Sagami Bay, and Hamacantha (Vomerula) umisachii sp. nov. from off Hachijo Island. This is the first record of Hamacantha and the Hamacanthidae from Japan. H. (V.) mamoi sp. nov. is characterized by having styles, two types of diancistras and one of sigmas. Only two known species have the same spicule composition: H. (V.) acerata Lévi, 1993 and H. (V.) esperioides Ridley Dendy, 1886, described from New Caledonia, and south-west Africa and south-east South America, respectively. H. (V.) acerata has larger diancistras and much smaller sigmas compared with those of H. (V.) mamoi sp. nov. H. (V.) esperioides can be separated by having larger styles and smaller sigmas than those of H. (V.) mamoi sp. nov. H. (V.) umisachii sp. nov is characterized by having styles, diancistras, cyrtancistra-like diancistras and sigmas. Hamacantha (V.) carteri Topsent, 1904 seems to have similar spicule composition, however the size of all spicule types is different.

A taxonomic revision of the genus Apostichopus (Holothuroidea: Stichopodidae) from Japan.

Complete redescriptions of sea cucumbers in the genus Apostichopus Liao, 1980 are provided using the type specimens and specimens deposited in the National Museum of Nature and Science, Tsukuba, Japan. The genus consists of A. armatus (Selenka, 1867) and A. japonicus (Selenka, 1867), which can be distinguished by some spicules in the dorsal body wall; the rim of reduced table spicules in A. armatus is spinous, while that in A. japonicus is smooth. Spicules from the tentacles, papillae, tube feet, and cloaca are similar for both species.

Sea cucumbers of the genus Stichopus Brandt, 1835 (Holothuroidea, Stichopodidae) in Straits of Malacca with description of a new species.

Five sea cucumber species including one new species of the genus Stichopus are reported from the shallow coral reefs of Straits of Malacca. The new species Stichopus fusiformiossa has unusual fusiform spicules in the tentacles, which are not found in the other species of the genus. Pseudo-tables and large perforated plates are newly recorded for Stichopus hermanni Semper, 1868 and Stichopus vastus Sluiter, 1887, respectively.