Interstitial Harpacticoid Research Articles

Taxonomic review of the genus Stenocaris Sars (Copepoda, Harpacticoida, Cylindropsyllidae), with (re)descriptions of two Stenocaris species from the Far East.

The taxonomic concept of the genus Stenocaris Sars, 1909 is uncertain because none of the synapomorphies for the species of Stenocaris are defined. Detailed comparison of previous records of Stenocaris minor (T. Scott, 1892) from different localities reveals that this species represents a species complex composed of two species, S. minor s. str. and S. minor sensu Cottarelli & Venanzetti, 1989. Because the latter species has fundamental differences in the nature of the fifth leg in females and the sexual dimorphism of the second leg in males, we propose a new species for S. minor sensu Cottarelli & Venanzetti, 1989, S. figaroloensis sp. nov. We also suggest that S. minor sensu Apostolov, 1971, S. minor sensu Marinov, 1971, and S. minor sensu Apostolov & Marinov, 1988 from the Black Sea and S. minor sensu Wilson, 1932 from North America should be relegated to species inquirenda in the genus. Taxonomic review of the morphology of all Stenocaris species indicated that the generic concept must be restricted to accommodate S. minor s. str., S. gracilis Sars, 1909, S. intermedia Itô, 1972, S. figaroloensis sp. nov., and the South Korean new species, S. marcida sp. nov., based on the synapomorphic condition of the confluent fifth leg in males. As a result of our analysis, two Stenocaris species, S. baltica Arlt, 1983 and S. pygmaea Noodt, 1955, are transferred to the genus Vermicaris Kornev & Chertoprud, 2008 as V. baltica (Arlt, 1983) comb. nov. and V. pygmaea (Noodt, 1955) comb. nov. based on the synapomorphic characters of a reduced condition of the second and fifth legs. Additionally, S. arenicola Wilson, 1932 and S. kliei (Kunz, 1938) are allocated to a new genus, Huysicaris gen. nov., mainly characterized by obvious caudal rami with a recurved dorsal spinous process and convex inner margins, as H. arenicola (Wilson, 1932) comb. nov. and H. kliei (Kunz, 1938) comb. nov. A marine interstitial harpacticoid collected from the subtidal substrate off Dok-do Island in the East Sea of South Korea is proposed as S. marcida sp. nov. and the distribution of S. intermedia, originally known from its type locality in Japanese waters only, is extended to the East Sea of Korea and Russia. We provide their detailed descriptions and illustrations and discuss the morphological characters supporting their identities.

Interstitial harpacticoid (Copepoda, Harpacticoida) fauna inhabiting mediolittoral zone of the Gulf of Saros (Turkey)

The study was aimed to reveal interstitial harpacticoid copepod fauna of the Gulf of Saros (Turkey), where no detailed research has been done before on this subject. The samples were collected from 30 stations located along the mediolittoral zone of the gulf between 2013 and 2014. As a result, a total of 72 species/subspecies belonging to 44 genera in 15 families were identified. All identified taxa except Tryphoema gallipoliensis Alper et al., 2018 are new records for the study area, besides 16 species were also recorded for the first time from the Turkish seas.

Faunistic and ecological assessment of interstitial Harpacticoida (Crustacea, Copepoda) on a sandy beach in Balıkesir (Turkey)

Interstitial harpacticoids along the mediolittoral zones of Sarımsaklı Beach, Turkey, were sampled monthly between April 2016 and March 2017 in order to reveal the effects of pH, water temperature, salinity, electrical conductivity, dissolved oxygen, and grain size on the occurrence and composition of the harpacticoids. Examination of the samples from nine stations revealed a total of 66 species. In terms of harpacticoid species abundance, Ectinosoma soyeri Apostolov, 1975 was ranked first followed by Sarsamphiascus angustipes (Gurney, 1927) and Leptomesochra eulitoralis Noodt, 1952. The variations in harpacticoid community were estimated by using some ecological indices (Species richness, Shannon’s diversity and Pielou’s evenness). Principal component analysis (PCA) based on the abiotic factors was applied for ordination of the stations. Relationships between environmental and temporal parameters as well as harpacticoid community structure were analyzed using distance-based Linear Models (DistLM). Relationships between environmental variables and most abundant species were determined with the Redundancy analysis (RDA). The abundance of S. angustipes and Klieonychocamptus ponticus (Serban and Plesa, 1957) were positively correlated with all tested variables except water temperature. The abundance of Klieonychocamptus kliei (Monard, 1935) was positively correlated with water temperature, grain size and salinity, while it was negatively correlated with dissolved oxygen and pH. The abundance of Ameira sp. and Microsetella norvegica (Boeck, 1865) were negatively correlated with all tested variables except water temperature. The abundance of E. soyeri and Ameira parvula (Claus, 1866) were negatively correlated with all tested variables except pH. The abundance of Leptomesochra eulitoralis was positively correlated with water temperature and salinity, while it was negatively correlated with grain size, dissolved oxygen and pH.

Harpacticoid assemblages (Copepoda: Harpacticoida) in the hyporheic zone of four streams in central Slovenia

Harpacticoids are an important component of meiofaunal assemblages in hyporheic zone. The goal of this study was to investigate distribution patterns of interstitial harpacticoid assemblages from four pre-Alpine streams originating in the Dinaric Karst and flowing into the Ljubljanica River. The sampling was conducted in 2002 at 12 locations distributed at a distance of approximately 1 km along each stream including tributaries, at a depth of 30–60 cm in the wetted channel (three sites per location) and depths from 65 to 160 cm on the stream banks (one site per location) using a Bou-Rouch pump. Concurrently, the interstitial water’s physical and chemical parameters were measured at two sites within each location (streambed, streambank). A total of 24 harpacticoid species were found, 12 of which were stygobionts (i.e., species living exclusively in groundwaters). Among them, two previously unknown species for science were found. Harpacticoid assemblage composition, with the exception of those from the Iška stream, did not differ significantly between the streams, indicating interconnectivity of the interstitial milieu. Sediment structure, amounts of particulate organic matter, conductivity and redox conditions seemed to have certain impacts, indicating the importance of hydrological and geological settings for harpacticoid assemblages.

A new species of the genus Paramesochra (Copepoda: Harpacticoida) from Korean waters

We describe a new species of the genus Paramesochra that was found in sandy sediments off Taean on the west coast of Korea during a study of interstitial harpacticoid copepods. Paramesochra taeana, sp. nov. superficially resembles P. acutata hawaiiensis Kunz, 1981, in the structure of the antenna, shape of the caudal rami, and seta formulae of thoracopods P1–P4. However, the new species was clearly distinguishable from P. acutata hawaiiensis by a combination of characteristics. With the exception of the last two somites, the new species is the only species in the genus that has well-developed hyaline frills on all of the body segments. The female displays eight-segmented antennules, and the median incision between both plates of its baseoendopod reaches about to the proximal line of the exopod in P5. Lastly, in males the baseoendopodal plate has a deeper median incision in P5. An updated key for species of the genus Paramesochra is provided.

Interstitial harpacticoids from groundwater in Tuscany (Central Italy): Parastenocaris reidae sp. nov., Nitocrella ensifera sp. nov., and notes on the morphology of Parastenocaris cf. glacialis Noodt (Crustacea: Copepoda)

Two new interstitial harpacticoids were recently collected from groundwater in Tuscany (Central Italy). The Parastenocarididae Parastenocaris reidae sp. nov. was collected from both phreatic and hyporheic habitats of River Serchio, Lucca province, together with specimens of Parastenocaris cf. glacialis Noodt. We describe and discuss the affinities of the former species, and give a preliminary description of the latter. Nitocrella ensifera sp. nov. was collected from the phreatic habitat of Fiora River, Grosseto, and from a well in the same area; this new species is described and its affinities are discussed.

Two new species of interstitial harpacticoids from southern Italy and proposal of a new Parastenocaris species‐group

Two interstitial harpacticoids collected in subterranean freshwater in Calabria are described and discussed. Ichnusella ionica sp. nov. was collected in the interstitial habitat of the Portigliola stream, a record extending the distribution of the genus, which was previously recorded only from Latium and Sardinia. Parastenocaris sibaritica sp. nov. is described from a similar habitat of the Crati River. This new taxon belongs to a group of species living exclusively in estuarine interstitial habitats and all characterised by peculiar morphological and ecological features. The creation of a new group, the “hera‐group”;, is proposed for these species.

Ichnusella improvisa sp. nov. from subterranean waters of Sardinia (Italy) and remarks on Itunella intermedia and Itunella muelleri (Copepoda, Harpacticoida)

Data are presented on interstitial harpacticoids collected at the estuaries of some rivers and streams in Sardinia. Ichnusella improvisa sp. nov., from the interstitial habitat of Ciuchesu Stream (Sassari Province, Sardinia), is described and discussed. A new key to the five species is presented, as well as observations on the genus ecology. New data on the morphology and ecology of Itunella intermedia, collected in the interstitial habitat of the Li‐scia River and Vignola Stream (Sassari Province, Sardinia) are given. This record extends the distribution of the species, which was previously recorded only from the Black Sea. Brief information on ecology and distribution of Itunella muelleri is also presented.

Reproductive Ecology of Three Species of Interstitial Harpacticoid Copepod in Otsuchi Bay, Northeastern Japan

Reproductive Ecology of Three Species of Interstitial Harpacticoid Copepod in Otsuchi Bay, Northeastern Japan

Physical reworking by near-bottom flow alters the metazoan meiofauna of Fieberling Guyot (northeast Pacific)

Although much of the deep sea is physically tranquil, some regions experience near-bottom flows that rework the surficial sediment. During periods of physical reworking, animals in the reworked layer risk being suspended, which can have both positive and negative effects. Reworking can also change the sediment in ecologically important ways, so the fauna of reworked sites should differ from that of quiescent locations. We combined data from two reworked, bathyal sites on the summit of Fieberling Guyot (32°27.631′N, 127°49.489′W; 32°27.581′N, 127°47.839′W) and compared the results with those of more tranquil sites. We tested for differences in the following parameters, which seemed likely to be sensitive to the direct or indirect effects of reworking: (1) the vertical distribution of the meiofauna in the sea bed, (2) the relative abundance of surface-living harpacticoids, (3) the proportion of the fauna consisting of interstitial harpacticoids, (4) the ratio of harpacticoids to nematodes. We found that the vertical distributions of harpacticoid copepods, ostracods, and kinorhynchs were deeper on Fieberling. In addition, the relative abundance of surface-living harpacticoids was less, the proportion of interstitial harpacticoids was greater, and the ratio of harpacticoids to nematodes was greater on Fieberling. These differences between Fieberling and the comparison sites suggest that physical reworking affects deep-sea meiofauna and indicate the nature of some of the effects.

Spatial variation in feeding, prey distribution and food limitation of juvenile flounder Rhombosolea tapirina Günther

The feeding and prey distribution of juvenile greenback flounder Rhombosolea tapirina Günther was compared between Swan Bay, a sheltered bay with muddy sediments and a well-developed seagrass-detrital system, and an adjacent area of Port Phillip Bay, a more exposed area with coarser sandy sediments. Meiofauna was dominated by benthic harpacticoid copepods in both bays. Harpacticoids in Port Phillip Bay, however, were mainly interstitial while epibenthic species were dominant in Swan Bay. The diet of juvenile flounder in Swan Bay was almost entirely composed of epibenthic harpacticoids. Juvenile flounder in Port Phillip Bay ate epibenthic harpacticoids, harpacticoid nauplii and gammaridean amphipods; interstitial harpacticoids were apparently not susceptible to flatfish predation. In Swan Bay, there was a rapid increase in the number of prey consumed with fish size but the mean size of prey was constant, reflecting the size distribution of harpacticoids in the environment. At one site in Port Phillip Bay, the pattern was similar except that the increase in prey number with growth was much lower. At a second site, prey number decreased while prey size increased with increasing fish size, due to a replacement of harpacticoid nauplii with much lower numbers of gammaridean amphipods. Consumption of prey in terms of weight increased allometrically with fish size at all sites. The rate was significantly higher (80%) in Swan Bay, suggesting that fish in Port Phillip Bay were food-limited. Gut clearance times for juvenile flounder feeding on epibenthic harpacticoids was estimated to be ≈ 13 h. Feeding rate, in terms of prey number, was approximately three to four times higher in Swan Bay relative to Port Phillip Bay. Although abundance of juvenile flounder in Swan Bay was higher than in Port Phillip Bay, prey abundances were also much higher, and predatory impact was estimated to be insignificant. Impact of predation also appeared insignificant in Port Phillip Bay although more data are needed.

NAUPLIAR DEVELOPMENT OF PARALEPTASTACUS BREVICAUDATUS WILSON, 1932 (COPEPODA: HARPACTICOIDA: CYLINDROPSYLLIDAE)

ABSTRACT All 6 naupliar stages of Paraleptastacus brevicaudatus Wilson, 1932, from a sandy intertidal beach of Helgoland Dune (North Sea), raised in the laboratory, are described in detail. As in other interstitial harpacticoid nauplii, the body form is elongate. Remarkable metamorphic changes throughout the naupliar phase provided a sufficient number of stage-specific characters for a key which allows the identification of the nauplius stages.

Does epibenthic structure negatively affect meiofauna?

The epibenthic harpacticoid copepod Parastenhelia megarostrum attains very high population densities in troughs of persistent sediment ripples on open intertidal sand banks in Pauatahanui Inlet, New Zealand. In closely adjacent eelgrass Zoslera capricorni Aschers beds, individuals of this species are only infrequently recorded from subcanopy sediments. Epibenthic structure in the form of flexible artificial seagrass plants was emplaced in the ripple field at two different times (June, September). Field experiments were undertaken to test the premise that presence of such structure would, by the creation of turbulent water flows around plants, lead to a progressive alteration in the microtopographic profile of the sediment leading to reductions in abundance of P. megarostrum. Moreover, these experiments were designed to test the effects of imposed overhead structure not only on this surface-dwelling copepod but also other components of the primarily infaunal meiobenthos. The experimental design consisted of two location treatments (inside and outside mimic grass plots) and two density levels of mimic plants within plots (30, 60 plants · 0.5 m −2), sampled at eight intervals representing time in days (D) since implantation of mimic plants (D1,2,4,6,8,12,16,31). Core samples were taken from within experimental plots, with replicates taken outside acting as undisturbed controls. The imposition of artificial epibenthic structure resulted in the rapid breakdown of ripple integrity, marked changes in profile and a net accumulation of sediment over the experimental period in both plant density treatments. In both 30- and 60-plant density plots, there were highly significant interactions between experimental period and location for P. megarostrum, with decreases in abundance inside plots. No equivalent interactions or main effects on abundance of the interstitial harpacticoid Paraleptastacus sp. or nematodes were revealed. Variance analyses indicated that abundance of P. megarostrum is less dependent on gross changes in the sediment surface than to the presence of overhead cover and that high densities in sediment depressions are a function of active aggregation rather than passive accumulation. Modification of sediment surface profile and mechanical disturbance by the sweeping action of seagrass blades clearly has a significant impact on epibenthic meiofauna but not on infaunal species.

Can passive recruitment explain harpacticoid copepod distributions in relation to epibenthic structure?

The importance of epibenthic structure and food in determining harpacticoid copepod densities was examined. Short-term recruitment of total harpacticoids, harpacticoid nauplii, Harpacticus spp., Tachidius triangularis Shen & Tai, Huntemannia jadensis Poppe, and interstitial harpacticoids into paired, defaunated sediment containers with mimic marsh grass or no structure was monitored in three field experiments. Although few statistically significant recruitment differences between these treatments were found, there was a general pattern of higher recruitment into one type of treatment for each experiment. In the first two experiments, higher abundances were usually found in the no-structure member of a treatment pair. These results matched those of a flume study in which less particulate matter accumulated within an area with structure compared to structureless areas. In the third experiment, the pattern was reversed. Trends in harpacticoid colonization among sampling periods were similar to that of bulk sediment transport. Harpacticoids responded positively to an enriched treatment created by allowing sediment containers to develop a rich microbial flora prior to deployment in the field, compared to an unenriched treatment. This positive response suggests that behavior can be important in determining local harpacticoid abundance. We conclude that passive recruitment alone cannot explain small-scale spatial distributions of harpacticoids.

Distributins of some interstitial harpacticoid copepods in an intertidal sediment (Preliminary report)

Three species of interstitial harpacticoid copepod (Phyllopodopsyllus punctatus, P. setouchiensis and Oniscopsis inabai) are characteristic inhabitants at the upper shore of Mukaishima Island in the Inland Sea of Japan. These species occurred jointly in the narrow zone, but their center of distributions were delicately separated. The depth distribution of each species in the sediment and their seasonal and diurnal migrations were investigated. Each species had characteristic depth-distribution pattern, and their relative positions were unchanged throughout most of the year irrespective of vertical seasonal mi.gration. P. punctatus, dweller of the shallow layer, made clear seasonal shift to the deeper layer in winter, but the tendency was not so obvious in other two deeper zone dwellers. Two Phyllopodopsyllus species made slight vertical movement during one daily tidal cycle, moved toward surface at ebb tide and toward deeper at flood tide. Some physical properties of the sediment were measured, but none of them positively correlated with species specific distribution patterns. Positive evidence of interspecific competition was not observed. To elucidate difference of species specific distribution by biological nature of the sediment, a series of choice experiments was carried out. Each harpacticoid species showed positive preference to the sand of the depth in which the species highly populated. It is suggested that the species specific preference to the organic film on the surface of sand grains may be one of the factors inducing microhabitat segregation within the sand-dwelling copepod community.

Forficatocaris Schadeni, a New Copepod (Harpacticoida) from Central Brazil, with Keys to the Species of the Genus

ABSTRACT A new species of interstitial harpacticoid copepod, Forficatocaris schadeni (Parastenocarididae) is described from a wet campo (field) in central Brazil. Males of F. schadeni differ from all previously described species in possessing a subterminal hypophysis extending well past the end of the endopod of leg 4, together with a strong lateral spine on leg 5. Females are distinguished by the small, triangular, flat outer subterminal spine of leg 5. This is the first record of this genus on a highly organic substrate. The wet campo habitat is described; it seems similar in stability to the psammic habitats of other forficatocarid species. Keys to known species of Forficatocaris are furnished.

Development of the sand-dwelling meiobenthic harpacticoid copepod huntemannia jadensis Poppe in the laboratory

Huntemannia jadensis Poppe, a common intertidal copepod in coastal waters of the north-western United States and British Columbia, Canada ranges in length from 0.1 mm at birth to 1.3 mm (adult female) and 1.5 mm for the larger of two male morphs. Body lenght alone is not a reliable indicator of the stage of development for ths species. All six naupliar and the first two copepodite stages are interstitial, but older stages are burrowers. Individual sand grains were grasped with antennae, first maxillae, and caudal rami for browsing attached diatoms. Males of both morphs clasped immature females up to several days before females molted to the adult stage and were inseminated. In cultures with daily addition of benthic diatoms, H. jadensis grew from egg to adult in 50 days at both 15 and 20°C, 66 days at 12°C, and 95 days at 8°C. Development never progressed past the naupliar stages at 4°C. Females lived for more than a year in culture, and a maximum of four broods per female was produced with broods 3 to 5 wk apart. A single observation of generation time (egg to egg) of 167 days was made at 8°C. aboratory egg moratality ranged from 17 to 83% per brood. Naupliar mortality was also very high, but copepodites suffered less than 25% mortality within each stage. Survivorship to maturity in the laboratory was highest at 8°C. Laboratory mortality patterns were similar to those observed in ield populations. Growth was so slow and cultures so difficult to mantain that H. jadensis is not recommended for future laboratory study of burrowing or interstitial harpacticoid copepods.

The zonation of psammolittoral harpacticoid copepods around the Isle of Man

The early qualitative works on the harpacticoid fauna of the British Isles by T. & A. Scott, Norman, Brady, Gurney and Thompson largely omitted the intertidal psammic biotopes. Nicholls (1935, 1939) did much to redress the situation, describing many new species of interstitial harpacticoids from the sandy shores of the Firth of Clyde. Although his studies were taxonomic, he supplied some useful information on the distribution of the species. Some ecological data is also to be found in subsequent works on the east coast of Ireland (Wells, 1963 a; O'Riordan, 1971), the Exe estuary (Wells, 1963 b) and the Isles of Scilly (Wells, 1961, 1970). The only detailed studies of interstitial harpacticoid zonation on British coasts are those of Harris (1972) for the lower shore at Whitsand Bay, Cornwall, and Mclntyre & Murison (1973) for Firemore Bay, Scotland.

Vertical and horizontal distribution of sub-littoral meiofauna in Algoa Bay, South Africa

Meiofauna was sampled using SCUBA along 4 transects from 5 to 30 m depth in Algoa Bay, South Africa. Substrates were well-sorted medium to fine sands with traces of sewage pollution in some areas. Meiofauna numbers recorded in the upper 10 cm of sediment were 55 to 584 10 cm-2, but total numbers, including deeper-living animals, were 680 to 2090 10 cm-2 at 6 stations. Longer cores showed meiofauna to be abundant down to at least 35 cm, and samples of interstitial water taken from this depth in the sediment were 7% saturated with oxygen. This is the first detailed record of meiofauna penetration into sub-littoral sand and stresses the need for long cores for quantitative work. Nematode numbers were found to be significantly related to nitrogen in the sand while interstitial harpacticoid numbers were related to median particle diameters, which determine pore space. Effects of sewage were slight and only one station showed notable enrichment, increased meiofaunal numbers and extreme dominance by nematodes.

Seasonal Changes in Population Density and Vertical Distribution of Harpacticoid Copepods on an Intertidal sand Beach

An account has been given (Harris, 1972b) of the distribution of interstitial harpacticoid copepods on an intertidal transect at Whitsand Bay, E. Cornwall. The present work describes seasonal changes observed in the copepod species populations over a period of 2 years, from May 1968 to May 1970. Changes in population density and vertical distribution are described, and the relationship between these changes and the physical environment are discussed. A full account of the reproductive activity and lifecycles of the copepod species will be given later (Harris, 1972d). The only detailed accounts of seasonal cycles of individual intertidal harpacticoids are those of Lasker, Wells & Mclntyre (1970) for the sand-dwelling benthic copepod Asellopsis intermedia (T. Scott) and of Barnett (1968, 1970) for two species of Platychelipus Brady on an intertidal mudflat.