Abdominal Uncini Research Articles

Jasmineira filatovae Levenstein, 1961, the deepest known sabellid is a Potamethus Chamberlin, 1919: redescription, new combination and generic emendation

Jasmineira filatovae Levenstein, 1961 was described from the Bering Sea from sediments at 3812–3940 m. Later, it was reported from 6328–9735 m in the Aleutian and Japan Trenches, thus becoming the deepest sabellid ever recorded. In the present study, syntypes of J. filatovae were examined. The syntypes possess anterior and posterior peristomial rings distinctly elongated, ventral sacs, parallel lamellae, companion chaetae and avicular thoracic uncini with long handles, and lack bayonet chaetae and inter-radiolar membrane. This combination of features does not match the diagnosis of Jasmineira Langerhans, 1880, but does match that of Potamethus Chamberlin, 1919. Consequently, the new combination of Potamethus filatovae (Levenstein, 1961) is presented with a complete redescription; further, a lectotype is proposed and other specimens are regarded as paralectotypes. Specimens of P. malmgreni (Hansen, 1887) were examined form the Norwegian Sea and the Arctic Ocean for comparative purposes. The diagnosis of the genus Potamethus is emended based on the variability found in some species: 1) the inter-radiolar membrane may be present, 2) peristomial moldures present in some species, 2) thoracic uncini with long handles, and 3) a hump on the angle between external margin of neck and handle of thoracic and abdominal uncini may be present.

A new freshwater fabriciid species (Sabellida, Fabriciidae) from the Uruguay River, Argentina, with some remarks on the relationships of Monroika Hartman, 1951, Manayunkia Bourne, 1884 and Brandtika Jones, 1974.

Between the years 2007 and 2009 a hitherto unknown fabriciid species was found in the Lower Uruguay River, Argentina. Initially, it was assumed that this species could represent Manayunkia speciosa, a freshwater species originally described from North America. However, re-examinations have revealed that these specimens are clearly different from M. speciosa but they resemble Monroika africana. However, differences were also found that clearly distinguish this South American species from the African species so that it is described here as M. clarae sp. nov. The characters found in Monroika clarae sp. nov. make it also possible to compare and discuss these characters with those from the West African species Monroika africana, the Southeast Asian species Brandtika asiatica as well as Manayunkia species in terms of their systematic position. This mainly concerns the structure of the radiolar crown, the number of abdominal chaetigers, the presence of transitional chaetae as well as the structure of the thoracic and abdominal uncini. Potential origins of the freshwater Fabriciidae are also discussed.

To name but a few: descriptions of five new species of Terebellides (Annelida, Trichobranchidae) from the North East Atlantic

The number of described species of the genus Terebellides Sars, 1835 (Annelida, Trichobranchidae) has greatly increased in the last years, particularly in the North East Atlantic. In this context, this paper deals with several putative species recently delineated by molecular means within a well delimited clade of Terebellides. Species are characterised here by a combination of morphological characters, and a complementary nucleotide diagnostic approach. Three species were identified as the nominal species T. stroemii Sars, 1835, T. bigeniculatus Parapar, Moreira & Helgason, 2011 and T. europaeaLavesque et al., 2019. Five species are described as new: T. bakkenisp. nov., T. kongsrudisp. nov., T. norvegicasp. nov., T. ronningaesp. nov. and T. scoticasp. nov. The distinctive morphological characters refer to the branchial shape, absence or presence of papillae on lamellae of anterior margin of branchial dorsal lobes, absence or presence of ciliated papillae dorsal to thoracic notopodia, geniculate chaetae in one or two chaetigers, and the morphology of thoracic and abdominal uncini teeth. Furthermore, the description of T. bigeniculatus is revised and complemented after examination of type specimens. An updated identification key to all species of the genus in NE Atlantic and a proposal of a classification of different types of abdominal uncini to be used in taxonomy are also included.

Structure, function and cell dynamics during chaetogenesis of abdominal uncini in Sabellaria alveolata (Sabellariidae, Annelida).

BackgroundDynamic apical microvilli of a single cell, called the chaetoblast, inside an ectodermal invagination form the template of annelid chaetae. Changes in the pattern of microvilli are frozen in time by release of chitin, such that the structure of the definitive chaeta reflects its formation. Cellular interactions during chaetogenesis also influence the structure of the chaeta. Analysing chaetogenesis allows for testing hypotheses on the homology of certain chaetal types. We used this approach to test whether the unusual uncini in Sabellaria alveolata are homologous to apparently similar uncini in other annelid taxa.ResultsOur study reveals unexpected details of sabellariid uncini, which mechanically reinforce the neuropodia enabling their use as paddles. The final structure of the chaeta is caused by pulses of microvilli formation and dynamic interaction between the chaetoblast and adjoining follicle cells. Cell dynamics during chaetogenesis of the uncini in Sabellaria alveolata exceeds by far that reported in previous studies on the formation of this type of chaetae.ConclusionDespite the superficial similarity of uncini in sabellariids and other annelids, differences in structure and details of formation do not support the homology of this type of chaetae. Chaetogenesis of sabellariid uncini involves unexpected microvilli and cell dynamics, and provides evidence that interactions between cells play a larger role in chaetogenesis than previously expected. In addition to their function as anchors, uncini in Sabellaridae stabilize the paddle-shaped notopodia, as each uncinus possesses a long, thin rod that extends deeply into the notopodium. The rods of all uncini in a single row form a bundle inside the notopodium that additionally serves as a muscle attachment site and thus have a similar function to the inner chaeta (acicula) of errant polychaetes (Aciculata).

Aracia sinaloae sp. n., a new brooding, simultaneous hermaphroditic fan worm from southern Gulf of California (Polychaeta: Sabellidae)

Currently, only two species are known in the sabellid genus Aracia: A. riwo (Rouse, 1996) and A. heterobranchiata (Nogueira, López & Rossi, 2004). The first was described from the surface of a Teredo-riddled log lying in 1 m of water among mangrove roots, in Papua (New Guinea), whilst the second was found on an organically enriched beach at São Sebastião (Brazil). In this contribution, a third species of Aracia is described from settling panels and red mangrove roots in an estuarine system located in southern Gulf of California (Mexico). The new species is a simultaneous hermaphrodite and brooder, unique in the presence of a rectangular ventral shield on the collar, shorter than those in posterior thoracic segments; and a high number of rows of teeth in thoracic and abdominal uncini, covering from one-half to three-quarters of the main fang length. Information about color patterns in live specimens, glandular patterns, and reproduction is provided.

Three species of Amphicorina (Annelida, Sabellida, Sabellidae) from Japan, with descriptions of two new species.

We describe two new species and redescribe one in the polychaete genus Amphicorina Claparède, 1864 (Sabellidae) from Hokkaido, Japan. Amphicorina ascidicola sp. n. differs from its 38 congeners chiefly in the reduction of the collar, but also in having three pairs of radioles, one pair of ventral radiolar appendages, a bifurcate ventral lobe on the anterior peristomial ring, six abdominal chaetigers, and a large anterior tooth on the abdominal uncini. Amphicorina ezoensis sp. n. has a crenulated collar, three pairs of radioles, and more than eight (12) abdominal chaetigers; Amphicorina ezoensis shares these character states with Amphicorina anneae (Rouse, 1994), Amphicorina eimeri (Langerhans, 1880), and Amphicorina persinosa (Ben-Eliahu, 1975), but differs from them in having two pairs of ventral radiolar appendages and a non-oblique collar. Amphicorina mobilis (Rouse, 1990) was previously known only from the type locality (New South Wales, Australia), but we identify our Japanese material as conspecific on the basis of morphological and molecular similarity.

Inference of phylogenetic relationships within Fabriciidae (Sabellida, Annelida) using molecular and morphological data.

Cladistic relationships among fabriciids have to date been explored in the context of adult morphology, but resolution has been declining as more species are described. In this study, we incorporated data on the reproductive system, including features related to the male sperm and sperm storage by females, to supplement existing data on adult morphology (for a total of 50 characters). Three nuclear DNA markers (18S rDNA approximately 1800 bp, the D1 region of 28S rDNA approximately 320 bp, and histone H3 approximately 330 bp) were sequenced from 21 species of fabriciids. We assessed the phylogeny of Fabriciidae based on an integrative analysis of these morphological and molecular characters. Our results show that, in addition to three previously recovered apomorphies for Fabriciidae (absence of ventral lips, modification of abdominal uncini to an elongate manubrium, and presence of branchial hearts), six more apomorphies associated with the reproductive system can be used to support this clade-spermiogenesis only in the thorax, spermiogenesis in large clusters with a central cytophore, single dorsal sperm duct, sperm nuclear projection, thickening of the sperm nuclear membrane and the sperm extra-axonemal sheath. The results require the erection of two new genera and two new species, which are described. © The Willi Hennig Society 2010.

Revised systematics of Fabricia oregonica Banse, 1956 (Polychaeta: Sabellidae: Fabriciinae): an example of the need for a uninomial nomenclatural system

Previous descriptions of members of Fabricia oregonica Banse, 1956, have distinguished it by the presence of only narrowly hooded inferior thoracic notochaetae, in contrast to the presence of pseudospatulate chaetae in median chaetigers of the type species, F. stellaris (Müller, 1774). In other respects, past descriptions of specimens to which F. oregonica refers have lacked the necessary detail to clearly determine generic placement, and the type material is in poor condition. Recently collected specimens matching earlier descriptions are used to redescribe members of the species. An exclusive sister-group relationship does not exist between F. stellaris and F. oregonica, precluding the latter species being assigned to Fabricia. Fabricia oregonica is therefore placed in a new genus, Bansella. Under the view that all taxa, whether phylogenetic or specific, are explanatory hypotheses, it is pointed out that the monotypic Bansella cannot be defined as such a hypothesis. While the International Code of Zoological Nomenclature requires that names be defined by way of ‘differentiating characters,’ this approach is at odds with the scientific endeavor of biological systematics to infer explanatory hypotheses, colloquially known as taxa. In addition to only having narrowly hooded inferior notochaetae, members of B. oregonica differ from F. stellaris specimens in having abdominal uncini with a much shorter manubrium. The ventral, lobe-like collar in B. oregonica specimens is also distinctly rectangular as opposed to triangular. Members of the two species are similar in that females have pigmented spermathecae in the bases of branchial lobes and spermiogenesis occurs in males in chaetigers 3–8.

Phylogeny of Chone Krøyer, 1856 (Polychaeta: Sabellidae) and related genera

An analysis was undertaken to test the monophyly of the sabellid genus Chone Krøyer using maximum parsimony methodology. Cladistic analysis revealed three monophyletic genera whose respective members were assigned previously to Chone. Chone sensu stricto (containing the type species) is defined by the presence of broadly rounded dorsal lips and thoracic uncini with a large tooth above the main fang, followed by a series of smaller teeth. Dialychone Claparède is re‐established for the second genus and a new name – Paradialychone – is proposed for terminals nested in the third clade. Dialychone and Paradialychone gen. nov. are the sister groups of Chone, defined by the presence of a simple pre‐pygidial depression and modified posterior abdominal uncini. Amphicorina Claparède is basal within Sabellinae and Euchone Malmgren is the sister group of Chone, Paradialychone gen. nov. and Dialychone. The analysis supports the transfer of C. princei and C. reayi to Jasmineira Langerhans. Present address: Laboratorio de Invertebrados Bentónicos, Instituto de Ciencias del Mar y Limnología, Unidad Académica Mazatlán, Universidad Nacional Autónoma de México, Calzada Joel Montes Camarena s/n, 82000, Mazatlán, Sinaloa, Mexico.

The genera Bispira Krøyer, 1856 and Stylomma Knight-Jones, 1997 (Polychaeta, Sabellidae): systematic revision, relationships with close related taxa and new species from Australia

A cladistic analysis undertaken to test monophyly of Bispira and Stylomma (including new species of both genera) and to ascertain relationships with related taxa reveals that Bispira is paraphyletic without the inclusion of Pseudobranchiomma and Branchiomma, and that Stylomma is monophyletic due to the presence of a structure on the dorsal basal flanges which has never been described before. New species of Bispira and Stylomma from Australia are described. Bispira serrata n. sp., differs from the other species of the genus in having serrated radiolar flanges whereas all other Bispira species have smooth flanges or lack them, and also by the shape of the thoracic and abdominal uncini, which are short-handled and have 2–3 rows of big teeth above the main fang, instead of having medium-sized handles and small, numerous rows of teeth over the main fang. Stylomma juani n. sp., is characterized by the presence of serrated radiolar flanges and unpaired compound eyes along the branchial radioles, whereas other species in the genus have smooth radiolar flanges and subterminal compound radiolar eyes.

FIRST REPORT OF POLYCHAETES FROM THE GENUS ORIOPSIS (POLYCHAETA: SABELLIDAE) ASSOCIATED WITH THE JAPANESE ABALONE HALIOTIS DISCUS HANNAI AND OTHER NATIVE MOLLUSCS IN CHILE

Abstract The external morphology of sabellids polychaetes gathered from green abalone (H. discus hannai) and 2 species of Chilean native gastropods (Fissurella sp. and Concholepas concholepas) was studied. According to the taxonomic keys of Fauchald (1977) and Rozbaczylo (1980), all of these polychaetes belong to the family Sabellidae; subfamily Fabriciinae, and genus Oriopsis (according to Day 1967 and Fitzhugh 1989). This work constitutes the first report of the presence of sabellids of the genus Oriopsis forming tubes in the shell of the green abalone Haliotis discus hannai. The worms analyzed correspond to small sized sabellids (1–2 mm long). The body is fusiform, not sacciform like T. heterouncinata. The gill crown is constituted of three pairs of radiolae, unlike T. heterouncinata counting with 2 pairs of radiolae. Another important difference with this sabellid previously reported habiting abalone shells is the shape of the abdominal uncini, in Oriopsis are rasp-shaped plates, without main fang, de...

Redescription of Chone infundibuliformis Krøyer, 1856 (Polychaeta: Sabellidae) and histology of the branchial crown appendages, collar and glandular ridge

Fifty-three species have been formally described in Chone Krøyer, 1856, showing wide variation in the shapes of dorsal lips, peristomium, and posterior abdominal uncini. Previous studies indicate that such variation could result in splitting of the genus; however, the original description of the type species, C. infundibuliformis did not include critical details and illustrations, and for other species, incomplete or misleading information has been provided. In order to redescribe the species C. infundibuliformis and delineate the genus, type and topotype materials were reviewed, and histological sections of the appendages of the branchial crown, collar and glandular ridge are described. The redescription points out that in C. infundibuliformis: 1) insertion of the branchial lobes is not exposed beyond the collar; 2) radioles have a paired series of pinnules of different sizes; 3) radiolar flanges are broad; 4) dorsal lips are broadly rounded, as long as wide, without mid-rib; they have hyaline cartilage, but there is no extension of the branchial skeleton; 5) dorsal lips are vascularized by a plexus of small blood vessels derived from the basal branchial blood vessels, which further back communicate with the dorsal vessel; 6) thoracic uncini have teeth above the main fang of unequal size, median tooth of basal row larger than teeth in subsequent rows; 7) uncinus shape shows variation within each torus, but no intersegmental gradation is appreciable; 8) females with oocytes distributed in all thoracic and abdominal segments; males with sperm in abdomen, with barrel-shaped nucleus and mushroom-shaped acrosome. The collar is supported by a dense mass of hyaline cartilage and covered by glandular epithelium composed of basophile glands. Acidophil glands, tubular-shaped with granulose secretions, constitute the glandular ridge. Size of teeth in thoracic uncini, presence or absence of abdominal uncini variation, latero-ventral posterior abdominal depression, dorsal lips internal construction and glandular ridge are compared among some species of Chone and close genera.

Sabellidae (Annelida: Polychaeta) living in blocks of dead coral in the Coiba National Park, Panam

During a study devoted to the characterization of the polychaete fauna associated with dead coral (Pocillopora spp.) in the Coiba National Park (Paci¢c coast of Panama¤ ), nine species belonging to seven genera of sabellids (Annelida: Polychaeta: Sabellidae) were found. Three species new to science are described. Amphicorina bichaeta sp. nov. is characterized by having three pairs of radioles, smooth collar, broad thoracic notochaetae of two kinds (plus bayonet chaetae), and abdominal uncini with a large anterior tooth. Amphicorina perkinsi sp. nov. is characterized by having four pairs of radioles, six to eight abdominal chaetigers, smooth and oblique collar, broad thoracic notochaetae and thoracic uncini with main fang surmounted by a distinct subdistal tooth and a curved row of little teeth. Amphiglena jimenezi sp. nov. is characterized by having long radiolar appendages, medium-sized handles in thoracic uncini, and gametes in middle abdominal segments. Another six species are recorded: Branchiomma cf. bairdi and Notaulax occidentalis, which are new for the Paci¢c Ocean, while Notaulax nudicollis and Megalomma circumspectum, are new for the Paci¢c coast of Panama¤ . The presence of Bispira melanostigma and Pseudopotamilla intermedia is veri¢ed.

Structure and Formation of Thoracic and Abdominal Uncini in Fabricia stellaris (Müller, 1774) – Implication for the Evolution of Sabellida (Annelida)

Within the Sabellida, Serpulidae and Sabellidae are sister groups and possess uncini, which are aligned in a transverse row inside the neuropodial rim of the thorax and the notopodial rim of the abdomen. In several sabellid species the shaft (manubrium) of thoracic neurochaetae is much longer than that of abdominal notochaetae. In order to compare both kinds of chaetae and to find hypotheses on the chaetation in the ground pattern of the Sabellidae, structure and development of thoracic and abdominal uncini of the small sabellid Fabricia stellaris were studied ultrastructurally and compared with SEM studies of the sabellids Branchiomma bombyx, Euchone analis and Sabella spallanzani, and the serpulids Protula tubularia and Pomatoceros triqueter. The thoracic uncini of F. stellaris consist of a large rostrum, which is surmounted by several spines of the capitium. Rostrum and capitium are bent towards the manubrium. The chaetae are formed at the dorsal edge of the neuropodial rim, close to the notopodial group of capillary chaetae. A group of microvilli preforms the rostrum, while individual microvilli give rise to each spine of the capitium. During chaetogenesis re-orientation of the microvilli causes curvation of the rostrum and capitial spines. The abdominal uncini have no rostrum. At the begining of their chaetogenesis several individual microvilli form the spines of the capitium. Their characteristic curvature also results from re-orientation of the microvilli during chaetogenesis. A comparison within the Sabellida leads to the assumption that reduction of the rostrum in abdominal uncini occured in the stem lineage of the Fabriciinae, because Sabellinae, Caobangia and Serpulidae retain the plesiomorphic uncinal design with rostrum, capitium and a short manubrium. Increase of the manubrial length of thoracic uncini evolved in the stem lineage of the Sabellidae. This result corroborates the assumption that sabellids evolved an elastic, rapidly secreted tube the animals can easily migrate from and thus were able to colonize instable environments.

New fan worm genera and species (Polychaeta, Sabellidae, Fabriciinae) from the western Pacific, and cladistic relationships among genera

Five new species are described from among the genera Fabriciola Friedrich, 1939 (one species from Okinawa), Novafabricia Fitzhugh, 1990 (two species from Australia and Papua New Guinea, respectively), and two new monotypic genera, Brifacia gen. n. (Australia), and Pseudoaugeneriella gen. n. (Okinawa). All species are known only from the intertidal. Fabriciola rubra sp. n. is a member of the species complex with red peristomial and pygidial eyes, inferior thoracic flagellate setae, and abdominal pin‐head setae. Novafabricia labrus sp. n., and N. exiguus sp. n., are distinguished from other species based on the distribution of inferior thoracic pseudospatulate setae. Brifacia metastellaris sp. n., resembles Fabricia stellaris (Müller, 1774) with regard to anterior peristomial ring collar construction and distribution of pseudospatulate setae, but differs in having abdominal uncini with relatively short manubria. Pseudoaugeneriella unirama sp. n., most closely resembles species of Augeneriella Banse, 1956 in general form, but has unbranched vascularized ventral filamentous appendages. Revised keys to fabriciin genera and selected species are provided. Cladistic relationships of these new genera and species to other Fabriciinae are examined and the status of some characters are reviewed. Whereas previous analyses have supported a monophyletic Augeneriella on the basis of branched, vascularized ventral filamentous appendages, present results show Augeneriella paraphyletic relative to Fabricia Blainville, 1828, Novafabricia, Fabricinuda Fitzhugh, 1990 Parafabricia Fitzhugh, 1992 and Brifacia. Similarly, some topologies show Novafabricia, which has only been defined by the presence of poorly developed dorsal lips, to be paraphyletic relative to Fabricia, Fabricinuda, Parafabricia, and Brifacia. The cladistic analyses do, however, support recognition of Brifacia and Pseudoaugeneriella. With the addition of Brifacia, the presence of unbranched, vascularized appendages is plesiomorphic for the Fabriciinae, which has not been previously hypothesized.

Three new species and a new genus of Spirorbidae (Polychaeta) from the southern Indian Ocean, with a brief description of two species incerta sedis from the southern hemisphere

Abstract Crozetospira dufresnei gen. n., sp. n. from Crozet Islands is placed provisionally in the Paralaeospirinae. It has asymmetrical distribution of abdominal uncini, 3 thoracic setigers and simple collar chaetae with coarsely serrated and cross-striated blades. Paralaeospira pseudotenuis sp. n. from Heard Island differs from other Paralaeospira in having a strongly calcified conical opercular “plate” without a talon. Romanchella sepicula sp. n. from Crozet and Marion Islands is unusual for the genus in having a pin-shaped talon. Brief descriptions of what appear to be a Eulaeospira sp. and a Nidificaria sp. (from Adelie Land and Kerguelen Islands respectively) are based on non-brooding specimens. The former has unusual opercular morphology, with two talons on the same opercular plate.

A new species ofPerkinsiana(Sabellidae, Polychaeta) from Papua New Guinea; with a description of larval development

Abstract A new species of Perkinsiana, P. riwo, is described from near Madang on the northern coast of Papua New Guinea. This species is smaller than most species of Perkinsiana and is distinctive in having extremely short handles on the thoracic and abdominal uncini. Perkinsiana riwo is similar to P. antarctica (Kinberg) in that they both brood batches of larvae attached to one or more ventral radioles of the radiolar crown. Perkinsiana riwo is a simultaneous hermaphrodite with oocytes in anterior abdominal chaetigers and sperm and spermatids in the following abdominal chaetigers. Sperm have a nearly spherical head with a cap-like acrosome and 4–5 spherical mitochondria surrounding the base of the free flagellum. Oocytes reach a maximum size of around 200 µm in diameter. Larvae develop inside individual egg capsules in the cocoon until they have three thoracic chaetigers. They then escape from the capsules and cocoon and swim for up to two days before settling.

Hydroides ezoensis Okuda, a fouling serpulid new to British coastal waters

The Japanese serpulid Hydroides ezoensis Okuda is reported from British waters for the first time, where it has formed large encrustations on ships' hulls, dock and marina structures and within industrial cooling systems in Southampton Water. The British specimens of H. ezoensis are like those previously described from both Japanese and French waters, apart from possible differences in the thoracic setae and abdominal uncini. Hydroides ezoensis seems to be confined to Southampton Water (including the Hamble Estuary) and the Solent (including the harbours of Portsmouth, Langstone and Chichester), and it is suggested that the species has been brought by shipping from the north-west Pacific, perhaps from Japan.