Correction: Arias et al. An Introduction to Diopatra, the Amazing Ecosystem Engineering Polychaete. Biology 2023, 12, 1027.

The authors wish to make an erratum to the published version of the paper [...].

An Introduction to Diopatra, the Amazing Ecosystem Engineering Polychaete.

The annelid genus Diopatra occurs in all major oceans but is best represented in the shallow depths of warmer waters, where it lives in elaborately decorated tubes. This paper provides an introduction to the animals, discussing their history and diversity. We describe and illustrate its morphology and geographic distribution. While they were thought to be predominantly gonochoristic, recent reproductive studies show that several species are protandric simultaneous hermaphrodites. Development is by broadcast spawning with a brief pelagic stage or direct development in the parental tube or egg mass attached to it. Diopatra is a key ecosystem engineer, altering water flow and deposition and increasing the availability of refugia. We also discuss its harvesting as fishing bait, its role as an alien or introduced species, its capacity to regenerate, its therapeutic potential, and its applications as a bioindicator species for climate change, geographic distribution changes, and dispersal.

Annelids of the eastern Australian abyss collected by the 2017 RV 'Investigator' voyage.

In Australia, the deep-water (bathyal and abyssal) benthic invertebrate fauna is poorly known in comparison with that of shallow (subtidal and shelf) habitats. Benthic fauna from the deep eastern Australian margin was sampled systematically for the first time during 2017 RV 'Investigator' voyage 'Sampling the Abyss'. Box core, Brenke sledge, and beam trawl samples were collected at one-degree intervals from Tasmania, 42°S, to southern Queensland, 24°S, from 900 to 4800 m depth. Annelids collected were identified by taxonomic experts on individual families around the world. A complete list of all identified species is presented, accompanied with brief morphological diagnoses, taxonomic remarks, and colour images. A total of more than 6000 annelid specimens consisting of 50 families (47 Polychaeta, one Echiura, two Sipuncula) and 214 species were recovered. Twenty-seven species were given valid names, 45 were assigned the qualifier cf., 87 the qualifier sp., and 55 species were considered new to science. Geographical ranges of 16 morphospecies extended along the eastern Australian margin to the Great Australian Bight, South Australia; however, these ranges need to be confirmed with genetic data. This work providing critical baseline biodiversity data on an important group of benthic invertebrates from a virtually unknown region of the world's ocean will act as a springboard for future taxonomic and biogeographic studies in the area.

Two new species of Mooreonuphis (Annelida: Onuphidae) from Australia.

Two new species of Mooreonuphis, a genus best known from the coasts of the Americas, are described from Australia, bringing the number of recognized Mooreonuphis species to 23. Mooreonuphis ariasi n. sp. was collected from off Sydney to Wollongong, New South Wales in sandy sediments, in depths of 25-50 m and M. wilsoni n. sp. in the Bass Strait and Tasmania, in 89-130 m. The two new Australian species are among the smallest and the only known abranchiate species in the genus. The summer collections of M. ariasi n. sp. contained a large number of brooders with their young undergoing asynchronous direct development in the parental tube. Nothing is known about the development of M. wilsoni n. sp.

Three new species of Aponuphis (Annelida: Onuphidae) from eastern Australia.

The genus Aponuphis, previously known from the eastern North Atlantic and the Mediterranean, is newly reported from Australia. Three new species are described from off Sydney to Wollongong, New South Wales in sandy sediments, in depths of 25-70 m, bringing the number of recognized Aponuphis species to ten. Aponuphis annae n. sp. and A. bellani n. sp. are abranchiate, whilst A. danicae n. sp. has branchiae over a short region of its body. The tubes of A. annae and A. danicae have a fragile mucous consistency with attached sand grains and that of A. bellani is transparent, tight-fitting and smooth. Two specimens of A. annae were collected with developing juveniles in their tubes demonstrating their direct development but the reproductive mode of the other two species is not known. The distinguishing characteristics of all recognized species are tabled and a key to the three Australian species is presented.

Hyalinecia (sic) Edwardsi Roule, 1898-the enigmatic ghost from abyssal depths-redescribed as Nothria edwardsi (Annelida: Onuphidae).

The deep sea is one of the largest ecosystems on earth, extending from 200 m, where sunlight becomes inadequate for photosynthesis, to the deepest trenches. However, it is still one of the least explored. Polychaetes are among the dominant groups in these environments worldwide and play a critical role in the deep sea food chain. Within polychaetes, the onuphids are one the best represented families from 2000 m deep to the hadal zone, with 46 recorded species (Paterson et al. 2009). Hyalinoecia edwardsi Roule, 1898 is one of the early described abyssal onuphids. The species was described from the Talisman station 136, located between the Azores archipelago and the Iberian Peninsula (referred as "l'Espagne") at 4255 m depth (Roule 1898). The original description is rather brief without illustrations and the species was characterised as follows: thick antennae, lateral ones reaching chaetiger 3; first chaetiger twice as long as second one; parapodia of first chaetiger with thick falcate hooks; parapodia of second chaetiger with bidentate hooks; parapodia of third chaetiger with limbate chaetae; following chaetigers with limbate, pectinate chaetae and subacicular hooks; oval tube looking flattened and covered by small particles, mainly quartzites of different colours (Roule 1898).

The identity of Paradiopatra bihanica (Annelida: Onuphidae) and reinstatement of P. calliopae.

Examination of the holotype of Paradiopatra bihanica (Intes & LeLoeuff, 1975) indicated that the identity of this species had been incorrectly represented in recent papers and that the ensuing synonymisation of P. calliopae Arvanitidis & Koukouras, 1997 was unwarranted. This led us to researching the history of the holotype and its representation in the literature to reinstate P. calliopae as the correct name for this very common Mediterranean and eastern North Atlantic species (Martínez & Adarraga 2001; Arias & Paxton 2015; Santelli et al. 2015).

Paradiopatra Ehlers, 1887 (Annelida: Onuphidae) from southwestern Europe with the description of a new species and new ultramorphological data for the genus.

This work recognises five species of Paradiopatra from southwestern Europe, represented in the Bay of Biscay, the Atlantic coasts of Iberia and the western Mediterranean Sea. One species, Paradiopatra florencioi sp. nov., is newly described from the Cantabrian slope, northern Spain. We are presenting detailed diagnoses of all species and report ontogenetic changes of P. bihanica and P. hispanica. Scanning electron microscopy elucidated previously known Methylene Blue or Green staining patterns of the ventral glandular pads as cuticular pores. A dichotomous key to all species is included.

Minibrachium, a new subgenus of Rhamphobrachium (Annelida: Onuphidae) from Australia with the description of three new species.

This study describes a new subgenus of miniature, progenetic Rhamphobrachium species from eastern Australia. Minibrachium, n. subg. is characterised by such paedomorphic features as lack of peristomial cirri and branchiae, possession of only two pairs of modified parapodia with spiny recurved hooks and very early onset of subacicular hooks. Three new species are described, of which at least R. (Minibrachium) nutrix n. sp., the type species (from Lizard Island, Great Barrier Reef), is a fully grown adult, brooding several 16- to 20-chaetiger juveniles in the parental tubes. Rhamphobrachium (M.) talboti n. sp. (from off Sydney) and R. (M.) fractum n. sp. (from Bass Strait), although twice as large as the type species, have only partially developed frontal lips, indicating either incomplete growth or presenting an additional paedomorphic character. We discuss the position of the new subgenus in the Rhamphobrachium complex and present a key to the subgenera of Rhamphobrachium and species of R. (Minibrachium).

Onuphis and Aponuphis (Annelida: Onuphidae) from southwestern Europe, with the description of a new species.

This study recognises five species of Onuphis and four species of Aponuphis from southwestern Europe, represented in the Bay of Biscay, the Atlantic coasts of Iberia and the western Mediterranean Sea. One species, Onuphis anadonae sp. nov., is newly described and another species, Aponuphis willsiei Cantone & Bellan, 1996 is a new record for the Iberian Peninsula waters. Aponuphis ornata (Fauvel, 1928) and A. willsiei are shown to be tube brooders and the development of the juveniles is described. The usefulness of some Onuphis characters, as well as the size-dependent distribution of branchiae and chaetae, complicating Aponuphis species identification, are discussed. We are presenting descriptions and photographs of the distinctive Aponuphis colour pattern which we recommend as an identificatory tool instead. A dichotomous key to all species is included.

Hidden diversity within the polychaete Onuphis eremita sensu lato (Annelida: Onuphidae)--redescription of O. eremita Audouin & Milne-Edwards, 1833 and reinstatement of Onuphis pancerii Claparède, 1868 .

Onuphis eremita, type species of the genus, and Onuphis pancerii, originally from La Rochelle (France) and Gulf of Naples (Italy) respectively, are two of the earliest described species of the family Onuphidae. Yet, the definition of the former was extremely confused, the latter was considered its synonym for nearly a century, and types do not exist. We have examined a large amount of material, old museum collections and newly collected specimens from the European Atlantic and Mediterranean and conclude that both, O. eremita and O. pancerii, are valid species. The most obvious differences are that O. eremita is a slender species with only tridentate pseudocompound hooks while O. pancerii is much more robust and has pseudocompound hooks with bi- and tridentate (or even multidentate) tips. Neotypes have been designated for both species and the two taxa are redescribed and illustrated. We regard O. eremita sensu stricto, as redefined on the neotype here, to be restricted to the European Atlantic and western and central Mediterranean; other records need to be re-evaluated. Some specimens of both species were collected with eggs (~ 200 µm diameter) protruding through openings in the body wall, and some O. eremita had ect-aquasperm, suggesting that reproduction is by broadcast spawning and indirect development. 

Paradiopatra (Annelida: Onuphidae) from eastern Australian waters, with the description of six new species.

This study recognises eight species of Paradiopatra from eastern Australian waters, of which only one, Paradiopatra ehlersi, had been previously recorded. Six species are newly described: P. acirrata n. sp., P. imajimai n. sp., P. longicappa n. sp., P. piccola n. sp., P. spinosa n. sp., P. variabilis n. sp., and one species is reported as P. cf. papillata. Descriptions of all species (with the exception of P. ehlersi) are given, accompanied by detailed illustrations, including scanning electron micrographs and drawings. A key to all 32 species of the genus is included plus a table summarising specific diagnostic characters of the Australian representatives.

Mooreonuphis vespa, a new brooding species of Onuphidae (Annelida) from northern Spain (Bay of Biscay).

A new species of the genus Mooreonuphis Fauchald, 1982 collected from the Cantabrian shelf (Bay of Biscay) is described. Mooreonuphis vespa sp. nov. constitutes the first record of this genus in European waters and is characterised by: conspicuous dark brown transverse segmental pigment bands; antennae and palps with 3-5 basal ceratophoral rings and a very long distal ring; unusually long and slender peristomial and dorsal cirri; simple branchiae from chaetiger 17-19. We present observations on its reproductive biology (including brooding behaviour) and remark on the biogeography of the genus.

Molting polychaete jaws--ecdysozoans are not the only molting animals.

Jaw shedding and replacement of Diopatra aciculata (Onuphidae, Eunicida), by the same process as arthropod molting, involving apolysis and ecdysis, is described here. These observations suggest that molting has either evolved convergently in eunicidan polychaetes and ecdysozoans or it was present in the last ecdysozoan/lophotrochozoan common ancestor and thus may not represent a synapomorphy of the ecdysozoans.