New species of the genus Spio (Annelida, Spionidae) from the southern and western coasts of Korea

A new spionid polychaete, Spio pigmentatasp. nov., is described from the southern and western coasts of Korea. This new species differs from its congeners by the combination of the following morphological characteristics: the presence of orange-brown pigmentation on the anterior part of the prostomium, black pigmentation on the peristomium and along the body, U-shaped nuchal organs, a comparatively long extension of metameric dorsal ciliated organs, three pairs of white dots per chaetiger, two to three posterior abranchiate chaetigers, and the presence of tridentate neuropodial hooded hooks. The partial 16S ribosomal DNA (rDNA) and nuclear 18S rDNA sequences of the new species and Spio sp. 2 reported by Abe and Sato-Okoshi (2021) from Japan showed high similarity, indicating that these two specimens belong to the same species. A detailed description and illustrations of the new species, together with molecular information, are provided.

Who’s who in Magelona: phylogenetic hypotheses under Magelonidae Cunningham & Ramage, 1888 (Annelida: Polychaeta)

Known as shovel head worms, members of Magelonidae comprise a group of polychaetes readily recognised by the uniquely shaped, dorso-ventrally flattened prostomium and paired ventro-laterally inserted papillated palps. The present study is the first published account of inferences of phylogenetic hypotheses within Magelonidae. Members of 72 species of Magelona and two species of Octomagelona were included, with outgroups including members of one species of Chaetopteridae and four of Spionidae. The phylogenetic inferences were performed to causally account for 176 characters distributed among 79 subjects, and produced 2,417,600 cladograms, each with 404 steps. A formal definition of Magelonidae is provided, represented by a composite phylogenetic hypothesis explaining seven synapomorphies: shovel-shaped prostomium, prostomial ridges, absence of nuchal organs, ventral insertion of palps and their papillation, presence of a burrowing organ, and unique body regionation. Octomagelona is synonymised with Magelona due to the latter being paraphyletic relative to the former. The consequence is that Magelonidae is monotypic, such that Magelona cannot be formally defined as associated with any phylogenetic hypotheses. As such, the latter name is an empirically empty placeholder, but because of the binomial name requirement mandated by the International Code of Zoological Nomenclature, the definition is identical to that of Magelonidae. Several key features for future descriptions are suggested: prostomial dimensions, presence/absence of prostomial horns, morphology of anterior lamellae, presence/absence of specialised chaetae, and lateral abdominal pouches. Additionally, great care must be taken to fully describe and illustrate all thoracic chaetigers in descriptions.

New species of the genus Spio (Annelida, Spionidae) from the southern and western coasts of Korea

A new spionid polychaete, Spio pigmentata sp. nov., is described from the southern and western coasts of Korea. This new species differs from its congeners by the following morphological characteristics combined: the presence of orange-brown pigmentation on the anterior part of the prostomium, black pigmentations on the peristomium and along the body, U-shaped nuchal organs, a comparatively long extension of metameric dorsal ciliated organs, three pairs of ventral epidermal glands per chaetiger, two to three abranchiate chaetigers, and the presence of tridentate neuropodial hooded hooks. The partial 16S ribosomal DNA (rDNA) and nuclear 18S rDNA sequences of the new species and Spio sp. 2 reported by Abe and Sato-Okoshi (2021) from Japan showed high similarity, indicating that these two belong to the same species. A detailed description and illustrations of the new species, together with molecular information, are provided.

Annelids in Extreme Aquatic Environments: Diversity, Adaptations and Evolution

We review the variety of morphological, physiological and behavioral modifications that annelids have acquired to cope with environments either unsuitable for, or on the limits of, survival for most animals. We focus on polychaetes (excluding sipunculans and echiurans) and clitellates (oligochaetes and leeches) and source information mostly from the primary literature. We identified many modifications common to both polychaetes and clitellates, and others that are specific to one or the other group. For example, certain land-adapted polychaetes show reduction in nuchal organs, epidermal ciliation and receptor cells, and other coastal polychaetes use adhesive glands and glue-reinforced tubes to maintain position in surf zones, while oligochaetes, with their simple body plans, appear to be ‘pre-adapted’ to life underground. Modifications common to both groups include the ability to construct protective cocoons, make cryoprotective substances such as antifreeze and heat shock proteins, develop gills, transform their bodies into a home for symbiotic chemoautotrophic bacteria, metabolize contaminants, and display avoidance behaviors. Convergent evolution in both directions has enabled annelids to transition from salt water to freshwater, sea to land via beaches, freshwater to soil, and surface water to subterranean water. A superficially simple worm-like body and a mostly benthic/burrowing lifestyle has facilitated radiation into every conceivable environment, making annelids among the most common and diverse animal groups on the planet.

Tubicolous polychaete worms (Annelida) from Bahía de Chamela Islands Sanctuary, Mexico, with the description of a new bamboo worm

The islands and islets of Bahía de Chamela, in the Eastern Tropical Pacific, were declared as the first marine sanctuary in Mexico and has been protected since 2002. Their marine biodiversity has been documented in a series of papers in the last decade, but only three species of polychaete worms have been reported. Sixteen species of sedentary polychaete worms belonging to the families Maldanidae, Oweniidae, Sabellariidae, Sabellidae and Serpulidae are reported to the Bahía de Chamela Islands Sanctuary, 15 of these species constituting the first records in the area. Isocirrus tropicus (Monro, 1928) (Monro 1928) and Notaulax californica (Treadwell, 1906) (Treadwell 1906) constitute new records to Mexico; Idanthyrsus mexicanus Kirtley, 1904 (Kirtley 1994) is first recorded since its description and one species of bamboo worm (Maldanidae) is described as new to science. The new species belongs to the genus Clymenura Verril, 1900 (Verrill 1900) and its characterised by the presence of a glandular shield on chaetiger 8; a cephalic plaque oval with smooth margins and a rounded palpode; nuchal organs straight, parallel, almost full length of plaque; manubriavicular uncini present from chaetiger 1 with 3–4 teeth above the main fang without hairs or bristles; two pre-anal achaetous segments with tori; an anal funnel with alternating triangular cirri, being the longest that are located mid-ventrally.

Revision of Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 (Annelida, Errantia, Hesionidae)

Leocrates Kinberg, 1866 and Leocratides Ehlers, 1908 are two genera of hesionid errant annelids (Hesionidae, Hesioninae) whose species have 16 chaetigers (21 segments). Leocrates species are free living in rocky or mixed bottoms, whereas Leocratides species are usually symbiotic with hexactinellid sponges. Marian Pettibone revised both genera as part of the R/V Siboga Expedition monographs 50 years ago, and most of her ideas have remained unchallenged regarding synonymy for genera and species. For example, she included three genera as junior synonyms of Leocrates: Lamprophaes Grube, 1867, Tyrrhena Claparède, 1868, and Dalhousia McIntosh, 1885, and from 21 nominal species, she regarded only eight as valid. In this revision, all material available was studied, and different morphological patterns were noted in nuchal organs lobes, pharynx armature, and chaetal features. Leocratides species belong to a single pattern; however, in Leocrates several patterns were detected. Three patterns are present for nuchal organs lobes: barely projected posteriorly (horizontal C-shaped), markedly projected posteriorly (U-shaped), and with lateral transverse projections (L-shaped). In the pharynx, upper jaws were noted as single, fang-shaped, or as double, T-shaped structures, whereas the lower jaw can be single, fang-shaped, or a transverse plate. Neurochaetal blades can be bidentate with guards approaching subdistal tooth, unidentate without guards, or with guards hypertrophied projected beyond distal tooth. The combinations of these features are regarded as different genera and consequently, Leocrates is restricted (including Tyrrhena), but Dalhousia, and Lamprophaea (name corrected) are reinstated, and three new genus-group names are proposed: Paradalhousia n. gen., Paralamprophaea n. gen., and Paraleocrates n. gen. Further, the standardization of morphological features allowed several modifications and the recognition of novelties. Thus, four type species were redescribed, four others were reinstated, 10 were newly combined, and 18 from different World localities are described as new. The new species are Lamprophaea cornuta n. sp. from the French Polynesia, L. ockeri n. sp. from the Hawaiian Islands, L. paulayi n. sp. from the Red Sea, L. pettiboneae n. sp. from the Marshall Islands, L. pleijeli n. sp. from La Réunion, L. poupini n. sp. from the French Polynesia, Leocrates ahlfeldae n. sp. from India, L. harrisae n. sp. from the Revillagigedo Islands, L. mooreae n. sp. from New Caledonia, L. reishi n. sp. from the Marshall Islands, L. rizzoae n. sp. from the Seychelles Islands, L. rousei n. sp. from Papua New Guinea, L. seidae n. sp. from the French Polynesia, Leocratides jimii n. sp. from Madagascar, Paralamprophaea bemisae n. sp. from the Maldives, P. crosnieri n. sp. from Madagascar, P. leslieae n. sp. from Kiribati, and P. meyeri n. sp. from the French Polynesia. However, Leocrates japonicus Gustafson, 1930 is a nomen nudum. Keys are included for identifying all hesioninae genera, and for all species in all the included genera.

Whole-head recording of chemosensory activity in the marine annelid Platynereis dumerilii

Chemical detection is key to various behaviours in both marine and terrestrial animals. Marine species, though highly diverse, have been underrepresented so far in studies on chemosensory systems, and our knowledge mostly concerns the detection of airborne cues. A broader comparative approach is therefore desirable. Marine annelid worms with their rich behavioural repertoire represent attractive models for chemosensation. Here, we study the marine worm Platynereis dumerilii to provide the first comprehensive investigation of head chemosensory organ physiology in an annelid. By combining microfluidics and calcium imaging, we record neuronal activity in the entire head of early juveniles upon chemical stimulation. We find that Platynereis uses four types of organs to detect stimuli such as alcohols, esters, amino acids and sugars. Antennae are the main chemosensory organs, compared to the more differentially responding nuchal organs or palps. We report chemically evoked activity in possible downstream brain regions including the mushroom bodies (MBs), which are anatomically and molecularly similar to insect MBs. We conclude that chemosensation is a major sensory modality for marine annelids and propose early Platynereis juveniles as a model to study annelid chemosensory systems.

Whole-head recording of chemosensory activity in the marine annelidPlatynereis dumerilii

Chemical detection is key to various behaviours in both marine and terrestrial animals. Marine species, though highly diverse, have been underrepresented so far in studies on chemosensory systems, and our knowledge mostly concerns the detection of airborne cues. A broader comparative approach is therefore desirable. Marine annelid worms with their rich behavioural repertoire represent attractive models for chemosensory studies. Here, we study the marine wormPlatynereis dumeriliito provide the first comprehensive study of head chemosensory organ physiology in an annelid. By combining microfluidics and calcium imaging, we record neuronal activity in the entire head of early juveniles upon chemical stimulation. We find thatPlatynereisuses four types of organs to detect stimuli such as alcohols, esters, amino acids and sugars. Antennae, but not nuchal organs or palps as generally hypothesised in annelids, are the main chemosensory organs. We report chemically-evoked activity in possible downstream brain regions including the mushroom bodies, which are anatomically and molecularly similar to insect mushroom bodies. We conclude that chemosensation is a major sensory modality for marine annelids, and propose earlyPlatynereisjuveniles as a model to study annelid chemosensory systems.

Cirrophorus species (Annelida: Polychaeta: Paraonidae) in the Sea of Marmara, with description of a new species

This paper deals with specimens of Cirrophorus collected from the depths ranging from 3 to 500 m in 2012 and 2013 in the Sea of Marmara, Turkey. Among the material, one new species and two already known species were found. The new species is mainly characterized by having long and clavate notopodial postchaetal lobes in the branchial region; red speckles near nuchal organs; and a very long branch of lyrate chaetae (4 times longer than the shorter one). A recently described species, Cirrophorus nikebianchii, was found at the majority of soft-bottom stations. All species found in the area were described and discussed.

A serial multiplex immunogold labeling method for identifying peptidergic neurons in connectomes

Electron microscopy-based connectomics aims to comprehensively map synaptic connections in neural tissue. However, current approaches are limited in their capacity to directly assign molecular identities to neurons. Here, we use serial multiplex immunogold labeling (siGOLD) and serial-section transmission electron microscopy (ssTEM) to identify multiple peptidergic neurons in a connectome. The high immunogenicity of neuropeptides and their broad distribution along axons, allowed us to identify distinct neurons by immunolabeling small subsets of sections within larger series. We demonstrate the scalability of siGOLD by using 11 neuropeptide antibodies on a full-body larval ssTEM dataset of the annelid Platynereis. We also reconstruct a peptidergic circuitry comprising the sensory nuchal organs, found by siGOLD to express pigment-dispersing factor, a circadian neuropeptide. Our approach enables the direct overlaying of chemical neuromodulatory maps onto synaptic connectomic maps in the study of nervous systems.