Two new species of the genus Pliciloricus (Loricifera, Pliciloricidae) from the Faroe Bank, North Atlantic

Five cruises to the Faroe Bank in the northeast Atlantic revealed a rich loriciferan fauna inhabiting shell gravel to fine carbonate sand. This paper describes two new species of Pliciloricus found at depths of 120-260 m. Currently, only six species of this genus have been described from various localities around the world, but several new species are currently being described. The diagnosis of the genus Pliciloricus is emended to include the two new taxa. The first of the two new species Pliciloricus leocaudatus sp. n. is characterized by having four new kinds of scalids in the second row and an additional row of alternating plates in the eighth row. The second species Pliciloricus shukeri sp. n. is characterized in having a secondary double organ in the third row. The morphology of the two species, including the new structures, has been investigated using LM and scanning electron microscopy. Conclusively, the scalid pattern of the introvert of Pliciloricus has been re-evaluated, due to the finding of the new structures. Additionally, a discussion of the life cycle of the genus Pliciloricus is given, since the postlarval stage is reduced in both new species.     

Rugiloricus bacatus sp. nov. (Loricifera ‐Pliciloricidae) and a ghost‐larva with paedogenetic reproduction

Abstract

A new species of Loricifera, Rugiloricus bacatus sp. nov. is described together with the diagnoses of two other Rugiloricus species, Rugiloricus sp. nov. A and B, from the Faroe Bank (North Atlantic). Characteristic for all three species is the presence of a new type of reduced larva, a ghost‐larva. This type of reduced larva was discovered in 1986 by Jeanne Renaud‐Mornant, but it was with the Faroe Bank material that it was first discovered that the ghost‐larvae belonged to the phylum Loricifera. The ghost‐larvae are eitherfound inside late instar Higgins‐larvae, called penultimate Higgins‐larvae, or in the sediment. The three types of Higgins‐larvae from the Faroe Bank can be distinguished by characters such as anterior setae, posterior setae and toes. The adults of Rugiloricus bacatus sp. nov. are characterised by a prominent ruff resembling a pearl necklace; two of the eight clavoscalids are modified in the 1st row; the 2nd row of leg‐shaped scalids are very large and robust, and the 9th row with 30 beak‐like scalids alternating with 30 alternating plates. The postlarvae are free‐living and their scalids on the introvert are reduced to protoscalids. Postlarvae and adult stages have not been found for Rugiloricus sp. nov. A and B and therefore only diagnoses of these two species are presented here.     

RAD sequencing of common whelk,Buccinum undatum,reveals fine‐scale population structuring in Europe and cryptic speciation within the North Atlantic

Buccinum undatum is a subtidal gastropod that exhibits clear spatial variation in several phenotypic shell traits (color, shape, and thickness) across its North Atlantic distribution. Studies of spatial phenotypic variation exist for the species; however, population genetic studies have thus far relied on a limited set of mitochondrial and microsatellite markers. Here, we greatly expand on previous work by characterizing population genetic structure in B. undatum across the North Atlantic from SNP variation obtained by RAD sequencing. There was a high degree of genetic differentiation between Canadian and European populations (Iceland, Faroe Islands, and England) consistent with the divergence of populations in allopatry (F _ST > 0.57 for all pairwise comparisons). In addition, B. undatum populations within Iceland, the Faroe Islands, and England are typified by weak but significant genetic structuring following an isolation‐by‐distance model. Finally, we established a significant correlation between genetic structuring in Iceland and two phenotypic traits: shell shape and color frequency. The works detailed here enhance our understanding of genetic structuring in B. undatum and establish the species as an intriguing model for future genome‐wide association studies.     

The effects of sediment type on growth rate and shell allometry in the soft shelled clam Mya arenaria L

Hatchery-reared juvenile Mya arenaria L. were grown for 11 wk in replicated gravel, sand, mud, and pearl net treatments under flow-through sea-water conditions in Maine. Analyses of variance showed significant differences between sediment treatments for final shell length, dry meat weight, chondrophore growth increment, and percent shell weight. Growth of juvenile M. arenaria was more rapid in fine sediments than in coarse sediments or nets.Regression slopes of shell length-shell height and shell length-shell depth varied significantly between sediment treatments. Slower-growing clams from nets and gravel were more globose than clams from sand or mud treatments. Clams grown in sand were longer and narrower than those from mud. Differences in growth rates and shell form were attributed primarily to the physical properties of the substrata, and their effects on the scope for growth of M. arenaria.     

New insights into the biodiversity and generic relationships of foliose Bangiales (Rhodophyta) in Iceland and the Faroe Islands

Foliose species of the Bangiales (Porphyra sensu lato) have a long history of study in the N Atlantic, but there are still regions, especially in the northern parts of the N Atlantic that need more attention. A molecular study using rbcL and cox1 sequences was undertaken to assess the diversity of foliose Bangiales species in Iceland and the Faroe Islands. Herbarium collections from the intertidal and subtidal of Iceland (summer and winter) and the Faroe Islands (all seasons) revealed a total of 13 species (11 common to both areas), which were referred to four of the genera recognized in a recent two-gene global phylogeny. Boreophyllum birdiae, Porphyra dioica, P. linearis, P. purpurea, P. umbilicalis, Pyropia ‘leucosticta’ A, Pyropia njordii Mols-Mortensen, J. Brodie & Neefus, sp. nov., Wildemania amplissima and W. miniata were common to both areas, while Pyropia thulaea and Wildemania abyssicola (Kjellman) A. Mols-Mortensen & J. Brodie, comb. nov. (=Porphyra abyssicola Kjellman) were reported from Iceland but not from the Faroe Islands; Porphyra sp. FO and Pyropia elongata were reported from the Faroe Islands but not from Iceland. Boreophyllum birdiae is reported for the first time for Iceland and Porphyra sp. FO is reported for the first time for the Faroe Islands. Pyropia njordii is described from the Faroe Islands and is also recorded for Iceland, Greenland, New England, USA and Nova Scotia, Canada. A total of 25 foliose Bangiales species are now reported from the N Atlantic and these results demonstrate the importance of investigating as many areas as possible to reach a more complete understanding of species diversity and distribution.     

Preliminary Studies of the Tardigrade Fauna of the Faroe Bank

Four cruises to the Faroe Bank have collected bottom samples for qualitative analysis of the meiofauna. The preliminary results show a very rich tardigrade fauna, with a large proportion of species new to science. At present 35 species of tardigrades belonging to 4 families (6 sub-families) have been found, of these are 22 new to science (63%). The 35 species comprise more than 20% of all known marine tardigrades. Halechiniscidae is represented by 30 species (1 Euclavarctinae, 11 Styraconyxinae, 12 Tanarctinae, 3 Halechiniscinae, 2 Florarctinae and 1Dipodarctinae). This family comprises 87.87% of the specimens sorted out so far. Specimens from the subfamilies Tanarctinae (46.63%) and Styraconyxinae (31.54%) are dominating. Batillipedidae is represented with 3species (8.63% of the specimens) and Coronarctidae (1.89%) and Stygarctidae (1.61%) with a single species each. Samples with similar sediment from 104—260 m depth have similar species distribution in the families. This implicates that the sediment is the key factor involved in the species distribution and that depth is less important. The calcareous sediment is a unique substrate and the tardigrade fauna of the Faroe Bank can be compared with that of sub-tropical and tropical coralline sand. The composition of species exhibits a strong taxonomic affinity with the tardigrade fauna from more southern latitudes, i.e. the Mediterranean Sea and the south-eastern coast of USA.     

Small-scale spatial distribution of marine meiobenthos: the effects of decaying macrofauna

Summary To evaluate the effects of decaying animals on small-scale horizontal distribution of meiobenthos in muddy habitats, a laboratory experiment was performed at the Askö Laboratory in the northwestern Baltic Sea. A microcosm (35×55×28 cm) containing a ca. 7-cm thick layer of sieved (0.5 mm) sublittoral mud was established in June 1990. Three months later specimens of the bivalve Macoma balthica were collected and killed in boiling water. The sediment inside the microcosm was implanted with empty shell, empty shell and dead animal or left alone. At the end of the experiment (17 days) visual examination of the microcosm revealed black spots at the sediment surface where dead animals had been implanted. The densities of nematodes, the most abundant group (98%), were not significantly different between areas. However total non-nematode fauna was found in much lower numbers (P<0.01) in the black spot areas. A multivariate analysis (detrended correspondence ordination) of nematode species abundance data separated samples from the black spot areas from the others. Of the 25 nematode species recorded in the microcosm, there was a significant difference between areas for four species. The decaying animals clearly attracted Monhystera disjuncta which was almost 6 times as abundant in the black spot areas compared to control and shell areas. Both the overall dominant species, Leptolaimus elegans and Calomicrolaimus honestus were found in lower numbers in the areas of dead Macoma than in control and shell areas. Sabatieria pulchra was found in lower numbers in the control areas compared to shell and dead animal areas. The overall structure of the nematode assemblage indicated a shift to lower dominance in the dead animal areas and it is speculated that decomposing animal tissue may be of primary importance regarding spatial distribution of meiobenthos.     

Phylogeography of North Atlantic intertidal tardigrades: refugia,cryptic speciation and the history of the Mid‐Atlantic Islands

Aim To analyse the phylogeographical history of intertidal tardigrades in the North Atlantic in order to improve our understanding of geographical differentiation in microscopic organisms, and to understand the potential importance of the Mid‐Atlantic Islands as stepping stones between the American and European coasts of the Atlantic Ocean. Location Twenty‐four localities from the Mid‐Atlantic Islands (Greenland, Iceland and the Faroe Islands) and both sides of the North Atlantic Ocean. Methods A mitochondrial marker (cytochrome c oxidase subunit I) was sequenced from individual tardigrades belonging to the genus Echiniscoides. The existence of cryptic species was detected using generalized mixed Yule coalescence analysis; lineage ages were estimated with relaxed clock methods; and the degree of geographical differentiation was analysed with samova analyses, haplotype networks and Mantel tests. Results Echiniscoides hoepneri, previously known only from Greenland, was recovered throughout the Mid‐Atlantic Islands. The Faroe Islands population was isolated from Greenland and Iceland, but overall genetic variation was low. The morphospecies Echiniscoides sigismundi had high genetic variation and consisted of at least two cryptic species. A northern and a southern species were both recovered on both sides of the Atlantic, but only the northern species was found on the Mid‐Atlantic Islands. The northern species showed signs of long‐term isolation between the Western and Eastern Atlantic, despite the potential of the Mid‐Atlantic islands to act as stepping‐stones. There was no sign of long‐term isolation in the southern species. The Mid‐Atlantic individuals of the northern species were of Eastern Atlantic origin, but Greenland and Iceland showed signs of long‐term isolation. The genetic pattern found in the southern species is not clearly geographical, and can probably be best explained by secondary contact between former isolated populations. Main conclusions North Atlantic intertidal tardigrades from the genus Echiniscoides showed strong geographical differentiation, and the Mid‐Atlantic Islands seemed unimportant as stepping stones across the Atlantic. The geographical variation of the northern species of E. sigismundi suggests post‐glacial recolonization from several refugia.     

Interpopulation comparison of growth patterns of 14 fish species on Faroe Bank: are all fishes on the bank fast-growing?

Individual growth and sexual maturity of 14 common fish species on Faroe Bank have been investigated and compared with published data from 36 geographical areas. To examine the importance of the Faroe Bank environment on fish growth, a discrimination between resident and migratory species was made. The present study shows that individuals of the resident species on Faroe Bank have higher growth performance and are, on average, 36% larger when they reach sexual maturity than individuals of the same age in other populations. For the migratory species, the difference is only 6%. Abundance of food and high temperatures are probably the main reasons for the high individual growth.     

Shell-shape variation in Faroese dog-whelks (Nucella lapillus (L.))

Nucella lapillus is a common and widely distributed carnivorous gastropod of North Atlantic rocky sea shores. Populations of this animal usually show variation in shell shape according to the exposure of their habitat to wave action, with individuals from exposed sites having a short squat shell and a wide aperture as compared with a more elongated form seen in shelter. The same pattern of variation is seen over most of the species European range, but there are some exceptions. One of these has been described in Sullom Voe (Shetland) and this prompted an investigation of Faroese populations to ascertain whether they behaved in a similar manner. It is shown in this paper that Faroese populations vary in shell shape with exposure in the usual way (and not like those in Shetland) and moreover show such a fine and precise reflection of minor alterations in environmental conditions that measurement of dog-whelk shells may prove to be the best way of 'measuring' exposure in Faroe.     

A new species of sublittoral marine gastrotrich, Lepidodasys ligni sp. n. (Macrodasyida,Lepidodasyidae), from the Atlantic coast of Florida

A new species of Lepidodasys is described from sublittoral sandy sediments off the Atlantic coast of Florida. Lepidodasys ligni sp. n. is a small species (≤ 450 µm) with a crossed-helical pattern of small, non-keeled, non-imbricated scales on the dorsal and lateral body surfaces, two columns of ventral, interciliary scales that form a herringbone pattern, and a series of anterior, lateral, dorsal and posterior adhesive tubes. Similar to Lepidodasys castoroides from the Faroe Islands, the new species possesses a caudal constriction that demarcates the posterior end containing the caudal organ. The frontal organ lies within the posterior constriction, which is heavily invested with somatic circular muscles. These muscles are also present throughout the trunk and represent a novel condition for species of Lepidodasys,which were previously considered to lack somatic circular muscles. Posterior of the caudal constriction is a large, barrel-shaped caudal organ that is wrapped in a series of interdigitating, spindle-shaped, incomplete circular muscle fibers. The caudal organ contains a sclerotized central canal, but the absence of distal cuticular endpieces distinguishes the new species from its morphologically similar congener, Lepidodasys castoroides.     

贝壳堤岛3种植被类型的土壤颗粒分形及水分生态特征

运用土壤粒径质量分布原理与分形学理论,以黄河三角洲贝壳堤岛的3种植被类型为研究对象,以裸地为对照,测定分析土壤颗粒分形维数、粒径组成和水分物理参数,探讨不同植被类型的土壤颗粒分形特征及其影响因素。结果表明：贝壳砂土壤中粗砂粒含量最高;其次是细砂粒,而石砾和粉粘粒含量较低。灌木林地和草地具有降低石砾、粗砂粒,增加细砂粒和粉粘粒含量的作用。不同植被类型土壤颗粒分形维数均值在1.5845－1.9157之间,大小依次为酸枣林、杠柳林和草地,表层高于20－40cm土层。酸枣林、杠柳林及草地0－40cm土壤容重均值分别比裸地低23.87%,14.51%和10.47%;总孔隙度均值分别比裸地增加16.96%,16.71%和1.31%。植被恢复措施对贝壳砂表层的孔隙结构、疏松程度改善较好,草地及灌木林地的蓄水性能均表现为0－20cm高于20－40cm。土壤颗粒分形维数与粉粘粒含量、毛管孔隙度、总孔隙度、饱和蓄水量、吸持蓄水量等呈极显著正相关,与细砂粒含量呈显著正相关,与粗砂粒含量和容重呈极显著负相关,与石砾含量、非毛管孔隙度、滞留蓄水量的相关性不大。从土壤分形维数及其水分生态特征来看,贝壳堤岛3种植被类型的改良土壤物理性质及蓄水保土功能表现为灌木林好于草地,其中酸枣林好于杠柳林,0－20cm好于20－40cm土层。     

Invasive tunicate restructures invertebrate community on fishing grounds and a large protected area on Georges Bank

Marine invasive species can profoundly alter ecosystem processes by displacing native species and changing community structures. The invasive tunicate Didemnum vexillum was first found on the northern edge of Georges Bank in 1998. It can form encrusting colonies on gravel substrates that are also a preferred habitat for a number of other invertebrates. In this study we used data collected via HabCam, a vessel-towed underwater imaging system, to investigate the distribution of D. vexillum and its relationship to other epibenthic macroinvertebrates in a portion of Georges Bank that includes fishing grounds and an area protected from bottom-fishing. This novel technology provides imaging of epibenthic species distributions in areas of the benthic environment that were previously unobservable. We found that D. vexillum density is negatively correlated with the Atlantic sea scallop (Placopecten magellanicus), barnacles (genus Balanus), the tube anemone (genus Cerianthus), the green sea urchin (Strongylocentrotus droebachiensis), the globular sponge of the genus Polymastia, and Bryozoa. However D. vexillum is positively correlated with Cancer spp. Crabs, the tube forming polychaete, Filograna implexa, and Asterias spp. sea stars. The hypothesis that D. vexillum restructures the invertebrate community is supported by principal components analysis, revealing it as a primary driver of variation in the community when present. Additionally, there is an effect of the closed area as compared to fishing grounds on the structure of the invertebrate community and the abundance of certain species as consistent with previous studies, bottom-fishing affects invertebrate community structure. Principal components analysis revealed that bottom-fishing also appears to weaken clustering among species in the invertebrate community as compared to the community structure in the closed area. Biodiversity in high gravel sites of the epibenthic environment, as measured by the Shannon diversity index, also declined with increasing D. vexillum percent cover, while the open and closed areas were not significantly different in their level of biodiversity. D. vexillum appears to be the key driver of biodiversity decline in the epibenthos when present, rather than other processes such as direct disturbance and extraction from dredging. This research evaluates ecological responses to the presence of an invasive tunicate and suggests that this invasive species is a major force in shaping the ecological interactions in invaded areas.     

Reexamination of the Species Assignment of Diacavolinia Pteropods Using DNA Barcoding

Thecosome pteropods (Mollusca, Gastropoda) are an ecologically important, diverse, and ubiquitous group of holoplanktonic animals that are the focus of intense research interest due to their external aragonite shell and vulnerability to ocean acidification. Characterizing the response of these animals to low pH and other environmental stressors has been hampered by continued uncertainty in their taxonomic identification. An example of this confusion in species assignment is found in the genus Diacavolinia. All members of this genus were originally indentified as a single species, Cavolinia longirostris, but over the past fifty years the taxonomy has been revisited multiple times; currently the genus comprises 22 different species. This study examines five species of Diacavolinia, including four sampled in the Northeast Atlantic (78 individuals) and one from the Eastern tropical North Pacific (15 individuals). Diacavolina were identified to species based on morphological characteristics according to the current taxonomy, photographed, and then used to determine the sequence of the “DNA barcoding” region of the cytochrome c oxidase subunit I (COI). Specimens from the Atlantic, despite distinct differences in shell morphology, showed polyphyly and a genetic divergence of <3% (K2P distance) whereas the Pacific and Atlantic samples were more distant (∼19%). Comparisons of Diacavolinia spp. with other Cavolinia spp. reveal larger distances (∼24%). These results indicate that specimens from the Atlantic comprise a single monophyletic species and suggest possible species-level divergence between Atlantic and Pacific populations. The findings support the maintenance of Diacavolinia as a separate genus, yet emphasize the inadequacy of our current taxonomic understanding of pteropods. They highlight the need for accurate species identifications to support estimates of biodiversity, range extent and natural exposure of these planktonic calcifiers to environmental variability; furthermore, the apparent variation of the pteropods shell may have implications for our understanding of the species’ sensitivity to ocean acidification.     

Standing stock,vertical distribution and flux of planktonic foraminifera in the Panama Basin

The relationships between planktonic foraminifera in the upper 2000 m of the water column and those in sediment traps and deep-sea sediments of the Panama Basin were investigated as part of the Composition, Flux and Transfer Experiments (CFATE) and the Sediment Trap Intercomparison Experiment (STIE) July–Dec. 1979. Planktonic foraminifera larger than 333 μm, sampled during the July–August trap deployment cruise, occurred most abundantly in the euphotic zone with maximal populations associated with the chlorophyll and primary production maxima both located in the upper thermocline just below the mixed layer. Juvenile abundances exceeded those of the >333 μm adults by 3–4 orders of magnitude and their depth distribution systematics indicated that most foraminifera reproduction occurs prior to sinking of the adults from the euphotic zone. Macroscopic aggregates and fecal pellets were identified as major carriers of smaller sized shells from the euphotic zone.During the July–August cruise, the species changed from an assemblage dominated byG. theyeri to one dominated byG. ruber; the liveG. theyeri population sank passively from the euphotic zone in early August with a mean settling speed of 150 m day^?1 while theG. ruber population grew in. The abundance of empty shells of all species in the upper 200 m varied by a factor of 40 during the deployment cruise and peaked on July 30, 1979. This variability was reflected in foraminifera collection rates of sediment traps deployed at 305 m for 24- and 6-h periods. The trap and watercolumn data were combined to calculate mean sinking speeds (>333 μm fraction) of several dominant foraminiferal species (G. ruber andG. theyeri, 500 m day^?1;G. dutertrei, 2000 m day^?1). Size and weight analysis of empty shells from plankton tows yielded values of empty shell density (calculated on a spherical basis using maximum shell dimension) ranging from 0.12 and 0.15 g cm^?3 (G. theyeri andG. ruber) to 0.60 g cm^?3 (G. dutertrei). These speeds and shell densities were found to be consistent with the laboratory sinking experiments of Berger and Piper (1972) and Fok-Pun and Komar (1983). It was concluded that shell fluxes through the water column may be calculated with reasonable accuracy using a modified version of the Bishop et al. (1977) settling model and empty shell size distribution data from pump and plankton tow collections. The Fok-Pun and Komar (1983) settling model is recommended for future modelling efforts but requires a more extensive set of measurements of each foraminiferal specimen to be made.The interpretation of foraminiferal flux profiles, based on the collections of sediment traps, plankton tows, and pumps deployed on time scales shorter than several days, must take into account the very short residence times of empty shells in the water column and short term temporal variability in empty shell production rates.Populations of >333 μm foraminifera sampled in Nov.–Dec. 1979 were reduced by a factor of six relative to the July–Aug. values. The cruise-to-cruise differences were due to reduced primary production and greater mixed layer depth.Planktonic foraminifera were well preserved in sediment traps deployed for 112 days at 665, 935 and 1770 m, although aragonitic pteropod shells were partially dissolved. The fluxes of many species into the 935 m trap could not be explained based on the standing stock data from the July–August cruise alone and it was noted that species fluxes during STIE were comparable to or exceeded maximal values measured by Thunell and Reynolds (1984) in bi-monthly time series traps deployed at the same location during the whole of 1980. The moored trap data could only be explained by higher mean foraminifera shell fluxes in the interval between trap deployment and recovery, consistent with the Bishop and Marra (1984) model of primary production and carbon flux at the STIE site.Primary differences between core top samples and trap samples, were explained by the loss from the sediments of dissolution prone species,G. theyeri andG. ruber leaving an assemblage dominated by the dissolution resistant species,G. dutertrei.     

First data on the shell structure of the Early Cretaceous (Berriasian) rhynchonellids from Crimea

The shell structure of the Early Cretaceous rhynchonellids from Crimea has not been previously studied. First data on the shell structure of Berriasian rhynchonellids from the family Praecyclothyrididae Makridin, 1964 from southwestern and central Crimea are presented. Sulcirhynchia semenovi (Moisseev, 1939), S. berriasensis (Lobacheva, 1980), S. gracilis (Lobacheva, 1977), Belbekella airgulensis Moisseev, 1939, B. mutabilis Lobacheva, 1983, B. minor Lobacheva, 1983 and partly Lamellaerhynchia rectimarginata (Smirnova, 1972) are studied. The shell wall of most species consists of three layers: external (finely or coarsely crystalline), fibrous, and prismatic layers. The layers are usually strongly recrystallized, especially external and prismatic layers. New fibers were formed by repeated dichotomy of ridges in different areas of the fibrous layer independently of the distance from the anterior margin.     

Strontium/Calcium ratio, carbon and oxygen stable isotopes in coccolith carbonate from different grain-size fractions in South Atlantic surface sediments

In this study, the Strontium/Calcium (Sr/Ca) ratio, and the carbon and oxygen isotopic compositions of coccoliths are investigated in three different grain-size fractions (<20 μm, 15-5 μm, <5 μm) of 17 surface sediment samples from the Equatorial and South Atlantic. The results are compared to environmental parameters in order to assess the factors controlling the observed coccolith geochemical patterns. Isotopic and geochemical composition of coccolith species in surface sediment samples from the South Atlantic greatly varies according to the different grain-size fractions. However, even if the absolute values show a great offset, the general trends are comparable. The δ¹⁸O values show a decreasing trend with increasing temperature. The δ¹³C and Sr/Ca ratio are mainly influenced by productivity of coccolithophores, which is in turn controlled by different factors, such as temperature, nutrient supply and productivity of other phytoplankton groups. Dilution and dissolution are negligible factors in these open marine samples. Therefore, coccolith abundance in bulk sediment is the best approximation for productivity of coccolithophores. The various coccolith species fractionate Sr differently, as is best shown by the 5-15 μm fraction where three species (Calcidiscus leptoporus, Helicosphaera carteri and Coccolithus pelagicus) predominantly occur.