Ocean Species Discoveries 13–27 — Taxonomic contributions to the diversity of Polychaeta, Mollusca and Crustacea

Background Despite centuries of exploration, marine invertebrate biodiversity remains notably under-described. The majority of species in major marine groups are still unnamed, limiting our ability to understand and conserve ecosystems facing rapid environmental change. The rate of species discovery continues to outpace the formal process of species description. This gap creates an urgent need for streamlined, scalable approaches to taxonomy. The SENCKENBERG OCEAN SPECIES ALLIANCE was founded to help meet this challenge by facilitating global collaboration, offering technical support for species documentation and promoting efficient taxonomic publishing. Within this framework, Ocean Species Discoveries provides a forum for concise, but data-rich descriptions of marine invertebrate taxa. This second collection presents a diverse set of taxonomic contributions, based on recent and historical collections, including newly-described species and a re-description of a previously poorly-known taxon. The integrative documentation of the taxa treated herein was facilitated by the newly-established Discovery Laboratory at the Senckenberg Research Institute, the first service unit dedicated to supporting alpha taxonomists. New information This article presents 14 new species and one re-description, two new genera, with taxa spanning three phyla. Newly-described taxa comprise two polychaete annelids: Nicon salinus Hernández-Alcántara & Dávila-Jiménez, sp. nov. and Spinther bohnorum Tilic & Rouse, sp. nov. Molluscs span four classes, with three polyplacophorans: Craspedochiton zefranki Vončina, sp. nov., Ferreiraella charazata Sigwart, sp. nov. and a new genus with type species Pycnodontochiton sinensis Sirenko, Zhang & Sigwart, gen. et sp. nov. and Pycnodontochiton tenuidontus (Saito and Okutani, 1990), comb. nov. The new monoplacophoran Veleropilina gretchenae Sigwart & Steger, sp. nov. is one of the first species of this class with a high-quality genome, published from the specimen that is now the holotype. The scaphopod Laevidentalium wiesei Sahlmann, 2012 represents a re-description and range extension and the bivalve Myonera aleutiana Machado & Sigwart, sp. nov. is the second bivalve including an anatomical description with noninvasive methods using micro-CT. Amongst crustaceans, there are two new amphipod species: Apotectonia senckenbergae Momtazi & Riehl, sp. nov. and Metharpinia hirsuta Souza-Filho & Andrade, sp. nov. Three isopod species were described, including the parasitic species Zeaione everta Boyko & Williams, sp. nov. that is the only species in the new genus Zeaione Boyko & Williams, gen. nov. and two free-living isopods: Haploniscus bulbosus Henseler, Knauber & Riehl, sp. nov. and Macrostylis peteri Riehl, sp. nov. Finally, there are two new tanaidaceans: Hoplopolemius olo Jóźwiak & Stępień, sp. nov. and Nesotanais thalassinus Stępień, sp. nov. The data used for the description of ten of the species and one of the new genera treated herein were wholly or partially obtained at the SOSA Discovery Laboratory using integrative methods including light and electron microscopy, confocal imaging, molecular barcoding and micro-CT scanning. Additional novel findings include the first record of the family Macrostylidae and the genus Macrostylis G. O. Sars, 1864 from Australian waters (Macrostylis peteri, sp. nov.) and novel host associations: Ferreiraella charazata, sp. nov. is documented with epibiotic tubeworms on its tail valves that are typical of this genus and the decapod Eucalliaxiopsis aequimana (Baker, 1907) is newly recorded as a host for bopyrid isopods, representing the first such record for the family Eucalliacidae.