Dorvilleid Polychaetes Research Articles

Temporal variation in infaunal community structure of chemosynthetic and non-chemosynthetic environments in Barkley Hydrates, British Columbia, Canada

Increasing evidence points to greater temporal variation in deep-sea ecosystems than previously thought. In cold seeps, most available evidence focuses on successional stages of megafauna, with few studies on temporal variability in infaunal communities. We present a temporal study of infaunal communities and sedimentary organic matter characteristics from Barkley Hydrates outcrop, a chemosynthetic environment that receives organic matter from chemosynthetic and photosynthetic (phytodetritus) origins. In order to help interpret results from the outcrop, we contrast temporal variability in outcrop communities during two sampling periods with corresponding variation in an adjacent background sedimentary habitat (both habitats at ~900 m depth, offshore of British Columbia, Canada), that receives food input only from a photosynthetic source (phytodetritus). Comparisons with the background community help in differentiating chemosynthetic from photosynthetic food effects at the outcrop. Our results show contrasting temporal patterns for each community. First, lower (though not significantly) total density at the outcrop site in May 2014 corresponded to a significant change in species characteristic of that location (i.e., oligochaetes, dorvilleid polychaetes, and bivalves) in the previous sampling period (i.e., September 2013). Background communities did not change significantly in total density or species composition. Changes at the outcrop coincided with higher values of δ13C in sediment layers in May 2014, indicating reduced contributions of chemosynthetic organic matter to the total organic carbon pool relative to September 2013, and low bottom water methane concentrations. Second, although not significantly different, we detected more recruits in September 2013 for multiple species (Bipalponephtys cornuta, Cossura longocirrata, ampharetid polychaetes, Leitoscoloplos sp., and Levinsenia sp.) at the background site, following increased surface primary productivity in summer (June-August 2013). The presence of recruits of ampharetid polychaetes at both sites in September 2013 suggests that, although most individuals from the hydrate site depend on chemosynthetic food sources and therefore track temporal variation of organic matter chemosynthesised from methane, some outcrop site species also track phytodetritus pulses, much as observed in the background community. Our results demonstrate the utility of temporal studies in identifying the primary food source(s) fueling seafloor communities, and the dynamic nature of deep-sea infaunal communities from contrasting sites in Barkley Hydrates.

Energy transfer in the Congo deep-sea fan: From terrestrially-derived organic matter to chemosynthetic food webs

Large amounts of recent terrestrial organic matter (OM) from the African continent are delivered to the abyssal plain by turbidity currents and accumulate in the Congo deep-sea fan. In the recent lobe complex, large clusters of vesicomyid bivalves are found all along the active channel in areas of reduced sediment. These soft-sediment communities resemble those fuelled by chemoautotrophy in cold-seep settings. The aim of this study was to elucidate feeding strategies in these macrofaunal assemblages as part of a greater effort to understand the link between the inputs of terrestrially-derived OM and the chemosynthetic habitats. The biochemical composition of the sedimentary OM was first analysed in order to evaluate how nutritious the available particulate OM is for the benthic macrofauna. The terrestrial OM is already degraded when it reaches the final depositional area. However, high biopolymeric carbon contents (proteins, carbohydrates and lipids) are found in the channel of the recent lobe complex. In addition, about one to two thirds of the nitrogen can be assigned to peptide-like material. Even if this soil-derived OM is poorly digestible, turbiditic deposits contain such high amounts of organic carbon that there is enough biopolymeric carbon and proteacinous nitrogen to support dense benthic communities that contrast with the usual depauperate abyssal plains.Stable carbon and nitrogen isotopes and fatty acid biomarkers were then used to shed light on the feeding strategies allowing the energy transfer from the terrestrial OM brought by the turbidity currents to the abyssal food web. In the non-reduced sediment, surface detritivorous holothurians and suspension-feeding poriferans rely on detritic OM, thereby depending directly on the turbiditic deposits. The sulphur-oxidising symbiont bearing vesicomyids closely depend on the reprocessing of OM with methane and sulphide as final products. Their carbon and nitrogen isotopic signatures vary greatly among sites and could reflect the intensity of the anaerobic oxidation of methane (AOM) in the sediments. Within the vesicomyid habitats, the heterotrophic fauna exhibits a distinctively light carbon isotopic signature in comparison to the background sediments, clearly indicating the utilisation of chemosynthetically-derived OM. Fatty acid biomarkers further confirm that dorvilleid polychaetes consume aggregates that perform AOM. Terrestrial OM reprocessing by microbial consortium thus ensures its transfer to the benthic food web in the Congo deep-sea fan.

Cryptic species and colonization processes in Ophryotrocha (Annelida, Dorvilleidae) inhabiting vertebrate remains in the shallow‐water Mediterranean

Over the past several years, there has been growing interest in how bones of decaying mammals are colonized in the marine seabed. One of the most common opportunistic taxa occurring worldwide on bones is dorvilleid polychaetes of the genus Ophryotrocha. In a recent study in the Mediterranean, Ophryotrocha puerilis and Ophryotrocha alborana were two of the most abundant species occurring in experimentally deployed bones. These species have direct development and this makes them a suitable model to study the mechanisms and processes allowing organisms lacking a dispersive larval phase to colonize new substrates. Here, we address the colonization processes at the molecular level for populations of O. puerilis and O. alborana on experimentally deployed mammal bones in the shallow‐water Mediterranean collected over a year at 3‐month intervals. High genetic distances between some of the O. puerilis organisms collected indicated the occurrence of at least two cryptic sibling species (O. puerilis ‘Shallow’ and O. puerilis ‘Deep’) apart from O. puerilis sensu stricto. This was corroborated with phylogenetic analyses using an alignment of three concatenated genes (COI, 16S, H3) and with species delimitation analyses using COI. The haplotype network inferred from COI sequences for O. puerilis ‘Shallow’ showed a few common haplotypes shared between the two trimesters analysed and several other less represented haplotypes only present in one trimester. Thus, colonization of these experimental bones may have been achieved by a few organisms that arrived to the bones and were able to reseed, and by several individuals arriving to the experimental bones and not persisting across time. In contrast, the haplotype network for O. alborana revealed that none of the haplotypes present in three different trimesters were shared, suggesting that the populations arriving at the bones during each trimester were totally replaced by new individuals during the subsequent trimesters. Our study suggests that different species of shallow‐water Ophryotrocha occurring in the Mediterranean may have different patterns of substrate colonization despite sharing similar life histories.

Ecological release and niche partitioning under stress: Lessons from dorvilleid polychaetes in sulfidic sediments at methane seeps

Organisms inhabiting methane seep sediments are exposed to stress in the form of high levels of hydrogen sulfide, which result mainly from sulfate reduction coupled to anaerobic methane oxidation. Dorvilleidae (Polychaeta) have successfully invaded this ecosystem, and multiple species in divergent genetic clades co-occur at high densities. At methane seeps in the NE Pacific off California and Oregon, the genera Ophryotrocha, Parougia and Exallopus are especially well represented. To test the hypothesis that dorvilleid coexistence is facilitated by niche partitioning through sulfide tolerance and trophic patterns, we examined dorvilleid species-specific patterns of occurrence and nutrition at methane seeps off Eel R. [ER] on the Californian continental slope and at Hydrate Ridge [HR] on the Oregon continental slope, and in two habitats (clam bed and microbial mat) characterized by lower and higher hydrogen sulfide levels, respectively. Microelectrode measurements of hydrogen sulfide enabled characterization of environmental sulfide levels for species sampled in background sediment cores and in colonization trays. Dorvilleids tolerated H2S levels from 10μM to over 2.6mM, with the majority of species inhabiting sediments with similar environmental H2S concentrations (median 85–100μM). Dorvilleid species richness was greater at HR than ER, but did not differ between clam bed and microbial mat habitats. Species distribution patterns reflected preferences for ER clam bed (lower sulfide levels), ER mat and HR clam bed (moderate sulfide levels), or HR mat (very high sulfide levels). Nutritional patterns, including trophic diversity and functional similarity, were examined using community stable isotope metrics based on δ15N and δ13C. Within each region, dorvilleid species exhibited multiple trophic strategies. Co-existing congeners typically exhibited distinct isotope signatures, suggesting trophic partitioning. Trophic diversity and δ15N range for whole assemblages (measured by Total Hull Area and Standard Elliptical Area using species averages) and functional redundancy or species packing (measured as distance to nearest neighbor) among species and individuals were generally higher at ER, where sulfide levels were lower than at HR. In contrast, average trophic diversity among individuals within a species was greater at HR than ER. In colonization experiments involving agar-based manipulations of sulfide in tray sediments that mimicked clam bed and mat conditions, dorvilleids comprised 68% and 48% of colonists at ER and HR, respectively. Dorvilleid species richness was higher in trays that were initially more sulfidic. However, habitat exerted stronger influence on the composition of colonizing dorvilleids than did sulfide additions. In the NE Pacific, regional, habitat and vertical (down-core) variation in hydrogen sulfide creates complex environmental heterogeneity at methane seeps, promoting high diversity of stress-tolerant taxa such as dorvilleid polychaetes.

Seep communities from two mud volcanoes in the deep eastern Mediterranean Sea: faunal composition, spatial patterns and environmental control

The Mediterranean Sea constitutes a unique environment to study cold-seep ecosystems due to the presence of different geodynamic settings, from an active margin along the Mediterranean Ridge (MR) to a passive margin in the Nile Deep-Sea Fan (NDSF). We attempted to identify the structure of benthic communities associated with the Napoli and Amsterdam mud volcanoes (MVs) located on the MR and to establish the links between faunal distribution and environmental conditions at different spatial scales. Comparison between the 2 MVs revealed that the faunal distribution seemed to be mainly controlled by the characteristics of the microhabitats. On both geological structures, the variability between the different microhabitats was higher than the variability observed between replicates of the same microhabitat, and the distribution of macrofauna was apparently linked to gradients in physico-chemical conditions. The peripheral sites from Napoli were generally more oxygenated and harboured lower species richness than the active sites. The reduced sediment microhabitat from Amsterdam presented the highest methane concentrations and was mainly colonised by symbiont-bearing vesicomyid bivalves and heterotrophic dorvilleid polychaetes. Overall, a higher taxonomic diversity was observed on Napoli. Substratum type was hypothesised to be the second factor influencing faunal distribution. The results of this study highlight the high heterogeneity of faunal communities associated with seep ecosystems within this region and the need to pursue investigations at various spatial and temporal scales.

Chemosynthetic trophic support for the benthic community at an intertidal cold seep site at Mocha Island off central Chile

We analyzed C and N stable isotope ratios of benthic fauna and their potential food sources at an intertidal methane seep site and a control site without emanation at Mocha Island (central Chile). The objective was to trace the origin of the main food sources used by the local heterotrophic fauna, based on the hypothesis that chemosynthetic production could be partially fueling the local food web at the seep site. Food sources sampled at both sites included macroalgae, particulate organic matter and bacteria-like filaments found growing over the red algae Gelidium lingulatum within the areas of active methane release. At the control site, located 11 km away from the gas emanation, fauna exhibited moderate δ 13C values ranging from −16.2‰ (in a nereid polychaete) to −14.8‰ (in a cirolanid isopod), which were consistent with those of the potential photosynthetic food sources sampled at this site (−20.2 to −16.5‰). δ 13C values of the photosynthetic food sources at the seep site similarly ranged between −25.4 and −17.9‰. However, a portion of the animals at this site were consistently more 13C-depleted, with δ 13C values close to that of the seeping methane (−43.8‰) and the bacteria-like filaments (−39.2 ± 2.5‰) also collected at this site. Specific examples were the Marphysa sp. polychaetes (δ 13C = −44.7 ± 0.6‰), the Schistomeringos sp. dorvilleid polychaetes (δ 13C = −42.9‰), and the tanaid crustacean Zeuxo marmoratus (δ 13C = −37.3 ± 0.2‰). The significantly higher δ 13C values of the herbivorous gastropod Tegula atra at the seep site (−29.3 ± 3.1‰) than at the control site (−12.6 ± 0.3‰) also indicated differences among sites of the preferred carbon sources of this species. Mixing model estimates indicate that at the seep site bacteria-like filaments could be contributing up to ∼60% of the assimilated diet of selected invertebrates. Furthermore, several indicators of trophic structure, based in isotopic niche metrics, indicate a considerably higher variety of basal resources used at the seep site and a consequent enhanced trophic diversity, compared with the non-seep site. The isotopic data gathered at the seep site clearly and unequivocally reflects the ingestion of a 13C-depleted primary food source, which could be the bacteria-like filaments observed at this site.

Macrofaunal succession in sediments around kelp and wood falls in the deep NE Pacific and community overlap with other reducing habitats

Sunken parcels of macroalgae and wood provide important oases of organic enrichment at the deep-sea floor, yet sediment community structure and succession around these habitat islands are poorly evaluated. We experimentally implanted 100-kg kelp falls and 200 kg wood falls at 1670 m depth in the Santa Cruz Basin to investigate (1) macrofaunal succession and (2) species overlap with nearby whale-fall and cold-seep communities over time scales of 0.25–5.5 yr. The abundance of infaunal macrobenthos was highly elevated after 0.25 and 0.5 yr near kelp parcels with decreased macrofaunal diversity and evenness within 0.5 m of the falls. Apparently opportunistic species (e.g., two new species of cumaceans) and sulfide tolerant microbial grazers (dorvilleid polychaetes) abounded after 0.25–0.5 yr. At wood falls, opportunistic cumaceans become abundant after 0.5 yr, but sulfide tolerant species only became abundant after 1.8–5.5 yr, in accordance with the much slower buildup of porewater sulfides at wood parcels compared with kelp falls. Species diversity decreased significantly over time in sediments adjacent to the wood parcels, most likely due to stress resulting from intense organic loading of nearby sediments (up to 20–30% organic carbon). Dorvilleid and ampharetid polychaetes were among the top-ranked fauna at wood parcels after 3.0–5.5 yr. Sediments around kelp and wood parcels provided low-intensity reducing conditions that sustain a limited chemoautrotrophically-based fauna. As a result, macrobenthic species overlap among kelp, wood, and other chemosynthetic habitats in the deep NE Pacific are primarily restricted to apparently sulfide tolerant species such as dorvilleid polychaetes, opportunistic cumaceans, and juvenile stages of chemosymbiont containing vesicomyid bivalves. We conclude that organically enriched sediments around wood falls may provide important habitat islands for the persistence and evolution of species dependent on organic- and sulfide-rich conditions at the deep-sea floor and contribute to β and γ diversity in deep-sea ecosystems.

Broad-scale effects of marine salmonid aquaculture on macrobenthos and the sediment environment in southeastern Tasmania

A comparison of sediments and associated macrobenthos at sites sampled within 20 fish farm leases distributed across southeastern Tasmania indicated major natural changes along a regional cline. Introduced taxa were strongly represented in the fauna, comprising 45% of total macrofaunal biomass. Large differences were evident between sites affected by different levels of organic farm waste. Sites located adjacent (< 10 m) to farm cages possessed significantly depressed sediment redox levels, a dominance of capitellid and dorvilleid polychaetes, and low macrofaunal species richness. Subtle impacts extended across farm lease areas in the form of depressed redox potential at 40 mm depth and changes to the macrobenthic community, including a prevalence of the dogwhelk Nassarius nigellus and a paucity of the heart urchin Brissus sp. and the maldanid polychaetes Asychis sp. and Rhodine sp. Minor farm effects were also evident at sites sampled 35 m outside farm lease boundaries, most notably as elevated population numbers of the polychaete Terrebellides sp., bivalve Mysella donaciformis and heart urchin Echinocardium cordatum. Amongst the univariate metrics examined, redox potential at 40 mm depth and the ratio of bivalves to total molluscs provided the most sensitive indicators of farm impacts, with the latter metric relatively insensitive to spatial variation between locations within the region studied.

Spatial heterogeneity of macrofauna at northern California methane seeps: influence of sulfide concentration and fluid flow

Relationships among fluid flow, sulfide concentration, sulfur bacteria and macrofaunal assemblages were examined at methane seeps on the northern California margin, near the mouth of the Eel River (512 to 525 m). Over a 6 mo period, sediments covered with microbial mats exhibited significant but variable outflow of altered fluids, with no flow reversals. This fluid flow was associated with high porewater sulfide concentrations (up to 20 mM) and almost no oxygen penetration of sedi- ments ( 300 µm), but biomass and diversity (no. species per core, E(S100), H ') were lower and composition varied in the sulfidic microbial mat sediments relative to clam-bed and non-seep sediments. The community in microbial mat-covered sediments consisted largely (82%) of 6 species in the polychaete family Dorvilleidae, whereas the clam-bed and non-seep microhabitats supported a mixture of annelids, peracarid crustaceans, nemerteans, and mollusks. Vertical microprofiling of sulfide in animal cores indicated that most taxa avoid H2S concentrations >1 mM. However, sulfide-oxidizing filamentous bacteria, dorvilleid polychaetes and bivalves (mainly V. pacifica) exhibited highest densities at sul- fide concentrations of 1 to 5 mM sulfide. Horizontal and vertical patterns of sulfide availability have a strong influence on the fine-scale distribution, structure and composition of macrofaunal assem- blages inhabiting methane seeps and must be accounted for when characterizing the microbiology and ecology of seep habitats.

Comparative analysis of the nervous systems in presumptive progenetic dinophilid and dorvilleid polychaetes (Annelida) by immunohistochemistry and cLSM

AbstractEntire nervous systems of the dinophilids Dinophilus (two species) and Trilobodrilus (three species) and the dorvilleids Parapodrilus psammophilus and Ophryotrocha gracilis (larva) were stained with antisera directed against serotonin, Phe‐Met‐Arg‐Phe‐NH2 (FMRFamide) and acetylated α‐tubulin and analysed by confocal laser scanning microscopy (cLSM). Adult dinophilids and the dorvilleid larva exhibit the same structure of the ventral nerve cord, with two main nerves spaced far apart, one median and two paramedian nerves. A serotonergic plexus is situated between the paramedian nerve pair, above the ventral locomotory ciliary band. These similarities between adults and larva corroborate the presumed progenetic origin of dinophilids. However, since larval nervous systems of other polychaete taxa also seem to be organized in this way, this result cannot support the view that dinophilids originate from dorvilleids. In P.psammophilus the main nerve cords are widely separated only in the last segment, indicating that this pattern may be correlated with the absence of parapodia. The unpaired median nerve of dinophilids, P. psammophilus and many other polychaetes, is considered to be part of the basic annelid body plan. The ground pattern of the ventral paired dinophilid ganglia is represented by three (anterior, main, posterior) commissures, conserved in most of the ganglia in the Dinophilus species and mostly reduced to a main commissure in the Trilobodrilus species. The dinophilid species and P. psammophilus possess six pairs of ganglia indicating six trunk segments – in contrast to former views. The two rings behind the prostomium in both the dinophilid and the dorvilleid species contain one pair of ganglia only, corroborating the presumed homology of this peristomial region in the two taxa. The Dinophilus nervous system with 12 longitudinal nerves and three perpendicular nerve rings per segment resembles orthogonal nervous structures characteristic of platyhelminths.

Micrognathozoa: A new class with complicated jaws like those of Rotifera and Gnathostomulida

A new microscopic aschelminth-like animal, Limnognathia maerski nov. gen. et sp., is described from a cold spring at Disko Island, West Greenland, and assigned to Micrognathozoa nov. class. It has a complex of jaws in its pharynx, and the ultrastructure of the main jaws is similar to that of the jaws of advanced scleroperalian gnathostomulids. However, other jaw elements appear also to have characteristics of the trophi of Rotifera. Jaw-like structures are found in other protostome taxa as well—for instance, in proboscises of kalyptorhynch platyhelminths, in dorvilleid polychaetes and aplacophoran mollusks—but studies of their ultrastructure show that none of these jaws is homologous with jaws found in Gnathostomulida, Rotifera, and Micrognathozoa. The latter three groups have recently been joined into the monophylum Gnathifera Ahlrichs, 1995, an interpretation supported by the presence of jaw elements with cuticular rods with osmiophilic cores in all three groups. Such tubular structures are found in the fulcrum of all Rotifera and in several cuticular sclerites of both Gnathostomulida and Micrognathozoa. The gross morphology of the pharyngeal apparatus is similar in the three groups. It consists of a ventral pharyngeal bulb and a dorsal pharyngeal lumen. The absence of pharyngeal ciliation cannot be used as an autapomorphy in the ground pattern of the Gnathifera because the Micrognathozoa has the plesiomorphic alternative with a ciliated pharyngeal epithelium. The body of Limnognathia maerski nov. gen. et sp. consists of a head, thorax, and abdomen. The dorsal and lateral epidermis have plates formed by an intracellular matrix, as in Rotifera and Acanthocephala; however, the epidermis is not syncytial. The ventral epidermis lacks internal plates, but has a cuticular oral plate without ciliary structures. Two ventral rows of multiciliated cells form a locomotory organ. These ciliated cells resemble the ciliophores present in some interstitial annelids. An adhesive ciliated pad is located ventrally close to a caudal plate. As in many marine interstitial animals—e.g., gnathostomulids, gastrotrichs, and polychaetes—a special form of tactile bristles or sensoria is found on the body. Two pairs of protonephridia with unicellular terminal cells are found in the trunk; this unicellular condition may be the plesiomorphic condition in Bilateria. Only specimens with the female reproductive system have been found, indicating that all adult animals are parthenogenetic females. We suggest that 1) jaws of Gnathostomulida, Rotifera, and the new taxon, Micrognathozoa, are homologous structures; 2) Rotifera (including Acanthocephala) and the new group might be sister groups, while Gnathostomulida could be the sister-group to this assemblage; and 3) the similarities to certain gastrotrichs and interstitial polychaetes are convergent. J. Morphol. 246:1–49, 2000 © 2000 Wiley-Liss, Inc.

Dorvilleidae (Annelida:Polychaeta) from the U.S. Atlantic slope and rise. Description of two new genera and 14 new species, with a generic revision of Ophryotrocha

The present paper contains descriptions of 14 new species of dorvilleid polychaetes that are part of a highly diverse benthic infauna sampled on the U.S. Atlantic slope and rise between the Canadian border and South Carolina. Quantitative samples were taken with a Hessler‐Sandia box core during 18 cruises between 1983 and 1987. Samples were sieved through screens having a mesh opening of 300 μ. The newly described species belong to the genera Ophryorrocha. Exallopus. Parophryotrocha and two new genera, Pseudophryotrocha gen.n. and Anchidorvillea gen.n. An emended generic diagnosis of Ophryotrocha is provided to accommodate some of the new species, but also to include a group of atypical species described earlier by several authors who had modified the generic concept of Ophryotrocha without providing a formal emendation. The genus Ophryotrocha is revised to contain 31 species helonging to two species groups. A comparison of a suite of morphologic characters, however. indicates that these species addressed in this paper are discussed in the context of the entire family Dorvilleidae.

Response of background fauna to disturbance and enrichment in the deep sea: a sediment tray experiment

Free-vehicle sediment trays were deployed on the floor of the Santa Catalina Basin (1300 m) to study the response of deep-sea infauna to defaunation and algal enrichment. We recovered three trays that had been filled with frozen basin sediment: one otherwise untreated, one enriched with 20 g of powdered Macrocystis pyrifera (kelp) and containing oxidized sediment, and one kelp-enriched and anoxic. After 4.7 months on the basin floor, macrofaunal density in the unenriched tray was 10% ( x = 3.8 individuals per 100 cm 2 ) of that in the surrounding sea floor. Most colonists belonged to species dominant in the background basin community. Juveniles and mature individuals were present, suggesting short maturation times or post-larval dispersal ability in some species. The kelp-enriched (oxidized) tray contained a single macrofaunal mite (Arachnida:Acarina), suggesting avoidance of kelp-enriched sediment by available colonists. The anoxic, kelp-enriched tray contained two dorvilleid polychaetes apparently adapted to high sulphide environments. As in other deep-sea studies, we obtained slower colonization of sediment trays than in shallow water experiments. The primary tray respondents, however, were dominants of the background community, in contrast to previous deep-sea experiments. The findings are consistent with the hypothesis that disturbance is important to the ecology of the dominant species in the Santa Catalina Basin.