A new genus and species of feather duster worm (Annelida, Sabellidae) from shallow hydrocarbon seeps in the Gulf of Mexico

Background

Sabellid species are known to have a broad depth distribution and have been reported from various deep-sea habitats, including chemosynthetic systems. Despite this presence, only two species have been identified from deep water chemosynthetic habitats and only one has been identified to species. When examining hydrocarbon seep systems along the Upper Louisiana Slope in the Gulf of Mexico, we observed an abundant sabellid species new to science. The characters for the collected specimens did not match any existing genus.

New information

The description for the new sabellid genus and species are presented, supported by external morphology and DNA sequence data (cytochrome c oxidase I). Seepicolaviridiplumi gen. nov., sp. nov. are gregarious, facultative hyper-epibionts within the examined methane seep communities and, seemingly, have a blend of morphological features of the genera Perkinsiana and Pseudopotamilla. Specimens also have several distinctive characters including the presence of a pair of peristomial chambers between the ventral lappets and parallel lamellae and the short, button-like shape of the radiolar tips. Abundance estimates for S.viridiplumi gen. nov., sp. nov. within the seep habitats are also presented.

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.

Redescription of Manayunkia caspica Annenkova, 1929 and M. danubialis Băcescu, 1944 n. comb. (Fabriciidae, Sabellida, Polychaeta)

The spread of the subspecies M. caspica danubialis Băcescu, 1944, which has been found in the Danube since 1944, into the upper section of the Danube as far as Austria was the reason for describing the characters of this species and comparing it with the nominotypical subspecies M. caspica caspica Annenkova, 1929, which lives in the Caspian Sea. Both subspecies are similar in the most important diagnostic characters, such as the number of branches of the radioles and the presence and number of pseudospatulate chaetae on thoracic chaetigers. However, they differ in other, less conspicuous characters, such as the number of thoracic uncini and the length of chaetigers. But these characters vary depending on the size of the specimens. Both subspecies inhabit completely different habitats. Based on the ecological species concept, the spatially and ecologically separated populations are regarded as distinct species, M. caspica, and M. danubialis n. comb. The occurrence of transitional uncini in both species and the presence of a brood chamber in the females of M. caspica are described for the first time. The structure of the radiolar crown is also described for both species. A molecular barcode for M. danubialis n. comb., a 654 base pair fragment of cytochrome c oxidase I is presented, allowing a fast and simple identification of this species by using a robust PCR/sequencing approach.

Host specificity of coral-associated fauna and its relevance for coral reef biodiversity

Coral-associated fauna predominantly consists of invertebrates and constitutes an important component of coral reef biodiversity. The symbionts depend on their hosts for food, shelter and substrate. They may act as parasites by feeding on their hosts, by overgowing their polyps, or by excavating their skeletons. Because some of these species partly reside inside their hosts, they may be cryptic and can easily be overlooked in biodiversity surveys. Since no quantitative overview is available about these inter-specific relationships, this present study adresses variation in host ranges and specificity across four large coral-associated taxa and between the Atlantic and Indo-Pacific oceans. These taxa are: coral barnacles (Pyrgomatidae, n = 95), coral gall crabs (Cryptochiridae, n = 54), tubeworms (Serpulidae, n = 31), and date mussels (Lithophaginae, n = 23). A total of 335 host coral species was recorded. An index of host specificity (STD) was calculated per symbiont species, based on distinctness in taxonomic host range levels (species, genus, family, etc.). Mean indices were statistically compared among the four associated taxa and the two oceanic coral reef regions. Barnacles were the most host-specific, tubeworms the least. Indo-Pacific associates were approximately 10 times richer in species and two times more host-specific than their Atlantic counterparts. Coral families varied in the number of associates, with some hosting none. This variation could be linked to host traits (coral growth form, maximum host size) and is most probably also a result of the evolutionary history of the interspecific relationships.

Phylogeny of Serpulidae (Annelida, Polychaeta) Inferred from Morphology and DNA Sequences, with a New Classification

Serpulidae Rafinesque, 1815 is a speciose group of polychaetes that all inhabit calcareous tubes. The family was traditionally subdivided into Serpulinae, Filograninae, and Spirorbinae. Recent phylogenetic analyses have suggested that both Filograninae and Serpulinae are paraphyletic, though with limited sampling. Here we report the first phylogenetic analysis of Serpulidae based on comprehensive sampling of genera (though excluding most spirorbin genera). We include a much-needed revision of serpulid taxonomy based on a phylogenetic hypothesis derived from both morphological and molecular data. We analysed 18S, 28S, histone H3 ribosomal nuclear DNA and cytochrome b (cytb) mitochondrial sequences, combined with morphological data. The proposed new classification includes the re-formulated Serpulinae (with tribes Serpulini and Ficopomatini), Spirorbinae, and Filograninae, with apomorphies highlighted for major taxa.

When a Worm Loves a Coral: A Symbiotic Relationship from the Jurassic/Cretaceous Boundary

Reefal limestones of the Štramberk Carbonate Platform are preserved as olistoliths and pebbles in deep-water flysch of the Outer Carpathians (Czech Republic, Poland). They contain the richest coral assemblages of the Jurassic/Cretaceous transition (Tithonian–Berriasian). Symbiotic associations between corals and tube-dwelling macroorganisms were recognized only in the branching scleractinian corals Calamophylliopsis flabellum and Calamophylliopsis sp. One to seven calcareous tubes were recognized either in coral calyces, embedded in the wall, or attached to it. Two types of tubes were recognized: Type 1: tubes with a diameter of 0.3–0.6 mm and a very thin wall (ca. 0.05 mm), mostly occurring inside corallites, and nearly exclusively in the Štramberk-type limestone of Poland; Type 2: tubes with an outer diameter of 0.8–2.0 mm and a thick wall (ca. 0.1 mm, some even up to 0.2 mm), mostly found in the Štramberk Limestone of the Czech Republic. Growth lamellae were observed in some thick walls. Most tubes are almost straight, some are curved. The tubes were probably produced by serpulids or by embedment of organic-walled sabellid polychaete worms. It is likely the oldest record of a sabellid–coral association. Modification of the coral skeleton in contact with tubes indicates that the worms were associated with live corals. For many modern and fossil worm–coral associations, this symbiotic association is interpreted as mutualistic or commensal.

Abundance of coral-associated fauna in relation to depth and eutrophication along the leeward side of Curaçao, southern Caribbean

Coral-associated invertebrates contribute much to the biodiversity of Caribbean coral reefs. Although the nature of their symbiotic relation is usually not fully understood, they can cause damage to their hosts, especially when they occur in high densities. The abundance of seven groups of coral-associated invertebrates was investigated on reefs along the leeward side of Curaçao, southern Caribbean. In particular, coral barnacles (Pyrgomatidae), boring mussels (Mytilidae: Leiosolenus spp.), gall crabs (Cryptochiridae), and Christmas tree worms (Serpulidae: Spirobranchus spp.) were recorded together with their host corals by means of a photo survey at four depths (5, 10, 15, 20 m) and across seven sites with high and five sites with low eutrophication values (based on δ15N isotope data). Feather duster worms (Sabellidae: Anamobaea), coral blennies (Chaenopsidae: Acanthemblemaria), and worm snails (Vermetidae: Petaloconchus) were insufficiently abundant for thorough quantitative analyses. The results show a decrease in the number of barnacles and Christmas tree worms per host over depth, which could be related to the availability of their host corals. Sites with high δ15N values show a higher abundance of barnacles and Christmas tree worms per host than sites with low values. This indicates that eutrophication could be favourable for these filter feeding organisms but when their densities become too high, they tend to overgrow their hosts and may become a threat to them.

Serpulid reefs and their role in aquatic ecosystems: A global review

The Serpulidae are a large family of sedentary polychaetes, characterized by a calcareous habitation tube, which they cannot leave. The calcium carbonate tube is in the form of both aragonite and calcite, in fairly constant ratio for each taxon. Tubes are cemented firmly to any hard substrate (in only few species tubes are free). Although in the majority of the species the tubes encrust the substrate for all their length, the distal part may eventually detach and grow erectly. Certain species in dense populations build tubes vertical to the substrate in clumps and cement the tubes to each other. This gives serpulids the capability of forming reef-life structures when densely settling. Despite the relative smallness of the individual tubes (rarely longer than 15cm and wider than 1cm), such reef-like structures may cover tens of m², with a layer more than 1m thick. Serpulid reefs can be divided roughly into seven groups, according to the building modality and the type of habitat they occupy: (i) pseudocolonies; (ii) littoral belts; (iii) subtidal to deep-water reefs; (iv) reefs in coastal lakes and harbours; (v) brackish water reefs; (vi) tapestries in freshwater caves; (vii) biostalactites inside marine caves. The role of serpulid reefs in the ecosystems they inhabit is multifarious and may be distinguished in functions (biomass and production, benthic pelagic coupling, resistance and resilience, reproductive and survivorship strategies, trophodynamics, bioconstruction, living space and refuge, nursery, sediment formation and retention, food for other species, carbonate deposition and storage) and services (water clearance, reef associated fishery, cultural benefits). On the other hand, many serpulids are important constituents of biological fouling, and their calcareous masses damage submerged artefacts, causing huge economic costs. Positive and negative roles of serpulid reefs need to be compared with common metrics; the overall balance, however, is still to be assessed.

A new species of the Spirobranchuskraussii complex, S.akitsushima (Annelida, Polychaeta, Serpulidae), from the rocky intertidal zone of Japan

A new species of Spirobranchus (Annelida: Serpulidae) is described based on specimens collected at the coastal Shonan area of Sagami Bay and the adjacent areas of Honshu, Japan. Spirobranchusakitsushima sp. nov. forms large aggregations in the intertidal rocky zone of warm-temperate Japanese shores. This species was referred to as Pomatoleioskraussii (Baird, 1864) until the monotypic genus Pomatoleios was synonymized with Spirobranchus. This new species is formally described based on morphologically distinct Japanese specimens with supporting DNA sequence data. The calcareous opercular endplate of Spirobranchusakitsushima sp. nov. lacks a distinct talon, but some specimens have a slight rounded swelling on the endplate underside, while in other species of the S.kraussii complex a talon is present, usually extended, and with bulges. We examined sub-fossil tube aggregations of the new species and suggest that such aggregation stranded ashore is a good indicator of vertical land movements (uplift and subsidence) resulting from past events, such as earthquakes, in Honshu, Japan.

Morphological Modifications and Injuries of Corals Caused by Symbiotic Feather Duster Worms (Sabellidae) in the Caribbean

Some coral-associated invertebrates are known for the negative impact they have on the health of their hosts. During biodiversity surveys on the coral reefs of Curaçao and a study of photo archives of Curaçao, Bonaire, and St. Eustatius, the Caribbean split-crown feather duster worm Anamobaea sp. (Sabellidae) was discovered as an associate of 27 stony coral species (Scleractinia spp. and Millepora spp.). The worm was also found in association with an encrusting octocoral (Erythropodium caribaeorum), a colonial tunicate (Trididemnum solidum), various sponge species, and thallose algae (mainly Lobophora sp.), each hypothesized to be secondary hosts. The worms were also common on dead coral. Sabellids of the genera Bispira and Sabellastarte were all found on dead coral. Some of them appeared to have settled next to live corals or on patches of dead coral skeleton surrounded by living coral tissue, forming pseudo-associations. Associated Anamobaea worms can cause distinct injuries in most host coral species and morphological deformities in a few of them. Since Anamobaea worms can form high densities, they have the potential to become a pest species on Caribbean coral reefs when environmental conditions become more favorable for them.

The complete mitochondrial genome of the marine feather duster, Bispira melanostigma (Annelida: Sabellidae)

The marine feather duster, Bispira melanostigma (Schmarda, 1861), is a tube-dwelling annelid that contributes to ecological and biogeochemical processes in benthic communities. Due to the lack of scientific data, B. melanostigma is often difficult to distinguish from other species of marine worms through morphological characteristics alone. In this study, we report the complete mitochondrial genome of Bispira melanostigma. The complete mitogenome contained 20,624 bp length with a total of 13 protein-encoding genes, 21 tRNA, and 2 rRNA genes. Phylogenetic analysis of the complete mitochondrial DNA of B.melanostigma can aid in the understanding of evolutionary relationships within Sabellidae.

Annelid Diversity: Historical Overview and Future Perspectives

Annelida is a ubiquitous, common and diverse group of organisms, found in terrestrial, fresh waters and marine environments. Despite the large efforts put into resolving the evolutionary relationships of these and other Lophotrochozoa, and the delineation of the basal nodes within the group, these are still unanswered. Annelida holds an enormous diversity of forms and biological strategies alongside a large number of species, following Arthropoda, Mollusca, Vertebrata and perhaps Platyhelminthes, among the species most rich in phyla within Metazoa. The number of currently accepted annelid species changes rapidly when taxonomic groups are revised due to synonymies and descriptions of a new species. The group is also experiencing a recent increase in species numbers as a consequence of the use of molecular taxonomy methods, which allows the delineation of the entities within species complexes. This review aims at succinctly reviewing the state-of-the-art of annelid diversity and summarizing the main systematic revisions carried out in the group. Moreover, it should be considered as the introduction to the papers that form this Special Issue on Systematics and Biodiversity of Annelids.