Status of the Nemertea as prey in marine ecosystems

Nemerteans are predators of a wide variety of animals, but little is known of their role as prey for other animals. The presence of toxins in the tissues and secretions of these worms has led to the assumption usually suggested that they are ingested only rarely. However, analysis of a Food Habits Data Base from the United States National Marine Fisheries Service, compiled for fishes collected in the Atlantic Ocean from the Canadian border to Cape Hatteras, North Carolina (1973–1990), showed that nemerteans were recovered from the stomachs of 27 species of fishes in 14 families. They were found in 223 of 26 642 (0.84%) fish stomachs examined in the laboratory, but only in 0.09% of 58 812 fish examined in the field. Among species in the former category, for which 1000 were examined, the winter flounder, Pseudopleuronectes americanus(Walbaum), and the yellowtail flounder, Limanda ferruginea (Storer), had the greatest frequency of nemerteans, 71 of 1545 (4.6%) and 33 of 1045 (3.2%), respectively. These nemerteans were identified as Nemertea, Cerebratulus sp. or Micrura sp., but it is likely that they were all of a Cerebratulus-like type. Nemerteans have also been recorded from the guts of eight additional species (including four additional families) of fishes collected from the western Atlantic Ocean, Gulf of Mexico, eastern Pacific Ocean (Washington, Alaska), North Sea and Indian Ocean off South Africa. The black-bellied plover, Pluvialis squatarola(L.), semipalmated plover, Charadrius semipalmatus Bonapart and the herring gull, Larus argentatus Pontoppidan are the only three species known to feed on nemerteans (Cerebratulus lacteus (Leidy) and Paranemertes peregrina Coe by the black-bellied plover and C. lacteus by the other species). Several species of nemerteans are known to ingest other nemerteans, and several arthropods, a squid, and a few other invertebrates also feed on these worms. On the other hand, careful laboratory studies have shown that some members of the Palaeonemertea, Heteronemertea and Hoplonemertea, when fed to various species of fishes, crustaceans (Astacidea, Anomura, Brachyura and Amphipoda) and a polychaete, were rejected, usually violently. There is a history of using large nemerteans, e.g. Cerebratulus lacteus and Polybrachiorhynchus dayi, as bait by sport fishermen in the United States and South Africa. The incongruity of successfuly using these toxic animals to catch fish is discussed in relation to conclusions on the importance of nemerteans as prey in the marine environment.     

Monoamine- and peptide-containing elements in the body wall and nervous trunks of nemerteans

Localization and morphological peculiarities of cateholamine-containing (CA-C), serotonin-(5HTIR), neurotensin-(NT-IR) and FMRFamide-immunoreactive (FMRFa-Ir) cells and processes in the body wall and lateral nervous trunks of nemerteans were investigated. The following nemertean species from three orders occurring in the White Sea were studied by fluorescent histochemistry and by immunohistochemistry: Lineus viridis, Lineus ruber and Cerebratulus sp. (Heteronemertini), Cephalothrix linearis (Palaeonemertini), and Amphiporus lactifloreus (Hoplonemertini). The similarity and characteristics of morphological types of monoamine-and peptide-containing elements, their distribution and possible participation in regulation of some functions in different nemertean species and in other invertebrates are discussed. We suggest that 5HT-IR and CA-C bi-and multipolar intra-and subepidermal open-type cells prevailing in the body wall perform a receptive function, while the FMRFa-Ir and NT-IR neurons of the nerve trunks and body wall are responsible for efferent innervation of musculature and connections within the nervous system.     

Recent phytoplankton productivity of the northern Bering Sea during early summer in 2007

Although the northern Bering Sea is one of the most productive regions in the northern North Pacific Ocean and currently considered a declining productivity region, no recent primary productivity measurements have been collected in this region. Phytoplankton productivity was measured in the northern Bering Sea in 2007 using a dual ¹³C–¹⁵N isotope tracer technique to quantify present rates of primary productivity and to assess changes under recent environmental conditions in this area. We found that large diatoms (mostly Fragilaria sp.) dominated the phytoplankton during the initial part of the cruise, whereas unidentified nano + pico phytoplankton largely dominated at the surface about 2 weeks later (at “revisited stations”). At the 1% light depth, diatoms and Phaeocystis sp. were the dominant species, whereas diatoms and unidentified nano + pico cells were dominant at the revisited sites. Based on nitrate and ammonium uptake rates, the estimated f-ratios (the ratio of nitrate uptake rate/nitrate + ammonium uptake rates of phytoplankton) were high (0.65–0.74), indicating that nitrate was an important nitrogen source supporting primary production in the northern Bering Sea during the cruise in 2007. Compared with previous studies performed several decades ago, we found significantly lower chlorophyll-a concentrations and carbon uptake rates of phytoplankton in the northern Bering Sea in 2007. This is consistent with recent studies that have shown lower rates of production in the Chukchi Sea and declines in benthic biomass and sediment oxygen uptake in the northern Bering Sea.     

Spatial, seasonal and species variations of harmful algal blooms in the South Yellow Sea and East China Sea

The occurrences of harmful algal blooms (HABs), in terms of frequency and area in the Chinese coastal waters, have been increasing since 1980s and caused considerable economic losses. In the present study, we have analyzed spatial and seasonal characteristics of HAB events in the southern Yellow Sea and East China Sea along Chinese coast from 1933 to 2004. With a total 435 HAB records, the most frequent HAB occurrence area (FHA) is off the Yangtze River mouth and another two FHA areas are located south of the Yangtze River estuary along about isobaths of 30–60 m coastal water in the East China Sea. The time of HAB occurrence shifted during our study period: from autumn (August–October) before 1980s to July–August in 1980s, during May–July in 1990s, and May–June for the period of 2000–2004. Causative species were found to be different: Noctiluca scintillans and Skeletonema costatum were dominant causative species prior to 2000; and Prorocentrum donghaiense Lu was dominant from 2000 to 2004 and also caused large blooms in May. Trichodesmium sp. caused many HABs in autumn (August–October) prior to 1980s with only one HAB between 1980 and 2004. The changes of the dominant HAB species may have affected the timings of HAB occurrence, as well as the increasing HAB-affected areas in recent years.     

Composition and distribution of pelagic ostracods (Ostracoda: Myodocopa) in the Somov and Ross seas and adjacent waters of the Southern Ocean

The study of materials collected by Russian expeditions and literature data showed that the pelagic ostracod fauna of the Somov Sea, which lies south of the Antarctic Divergence (AD), is an impoverished complex of the fauna of the Australian-New Zealand Antarctic sector. While to the north of the AD the ostracod fauna includes species introduced from waters of the subantarctic and tropical-subtropical structures, ostracods of the Somov Sea are mainly typical Antarctic species. To the north and south of the AD, ostracod abundance and species richness are highest in the depth range of 200–500 m (especially at 300–400 m). Austrinoecia isocheira is the most common species in the Somov Sea and Alacia hettacra in the adjacent northern region. The more southerly Ross Sea has harsher environmental conditions than the Somov Sea and its ostracod fauna is a more impoverished complex of mainly Antarctic species. Alacia belgicae and A. isocheira are the dominant species in the Ross Sea, with their highest abundances at 200–300 m depths. The proportion of A. hettacra in the Ross Sea taxocene decreases southwards. The taxonomical composition and biogeographical structure of ostracod faunas change in the AD region at the northern boundaries of both seas.     

Multi-annual changes in the parasite communities of rabbitfish Siganus rivulatus (Siganidae) in the Gulf of Aqaba, Red Sea

The parasite communities of the rabbitfish, Siganus rivulatus, were used to track multi-annual changes in the northern Gulf of Aqaba, Red Sea, in an environment subjected to ongoing anthropogenic impact. Parasitological data from these fish were collected from 1998 to 2000, with spring and fall samplings at three locations: at a coral reef (OBS), at a sandy beach area (NB) and at a mariculture cage farm (FF). These data were compared with data from 1995–1997 as well as data collected during 1981–1985 at the coral reef sampling site. The data analyses indicate that the ratio between heteroxenous and monoxenous parasite species declined significantly at all sites between 1995–1997 and 1998–2000. During the same period, the species richness of monoxenous parasites increased significantly at all sites. The species richness of heteroxenous parasites decreased significantly at the coral reef site, but remained steady at the other two sites. This coincided with a significant increase in the prevalence of monogeneans at the OBS and FF sites and a significant decrease in the prevalence of digeneans at the FF and NB sites. The decline in the abundance of the latter, specifically of Opisthogonoporoides sp. and Gyliauchen sp., was even more significant when compared with the 1981–1985 data. The prevalence of other gut helminths, namely the digenean Hexangium sigani and the nematodes Cucullanus sigani and Procamallanus elatensis, however, showed a significant increase over the same period. Analysis of the species richness and diversity indices of the parasite communities did not reveal conspicuous differences. These, however, did become apparent when heteroxenous and monoxenous members of particular taxa were analyzed separately. Therefore, when using parasite assemblages to detect ecological changes, it is essential to analyze not only at the community level, but also to consider separate components of particular parasitic groups. Communicated by H. von Westernhagen, A. Diamant     

Effects of increases in salinity on phytoplankton in the Broadwater of the Myall Lakes, NSW, Australia

The Broadwater of the Myall Lakes system is highly susceptible to cyanobacterial bloom formation after heavy rain events. During prolonged low flow periods, saline intrusion from the lower Myall River increases salinity levels and effectively controls some bloom forming algal taxa. To assess the effect of low-to-moderate increases in salinity (up to 4 ppt) on phytoplankton chlorophyll a, cell abundance, diversity and assemblage structure, salinity enhancement experiments were conducted on Broadwater samples collected in June 2005 (salinity 1.5 ppt), October 2005 (4 ppt) and January 2006 (12 ppt). Natural phytoplankton assemblages were incubated in the laboratory for 10 days, under different treatments of salinity (no addition, +2 ppt, + 4 ppt) and nutrient conditions (no addition, excess N+P). The greatest impact of salinity enhancement in N+P enriched samples was observed in June (1.5–5.5 ppt); chlorophyll a was significantly reduced in samples with the highest salinity treatment, and the taxon most negatively affected by an elevation in salinity to 5.5 ppt was Anabaena circinalis. Taxonomic richness and diversity (Shannon–Wiener index) were unexpectedly significantly higher at 5.5 ppt than at 1.5 ppt. This result, in part, explains the observed significant differences in phytoplankton assemblage structure over this salinity range. In October, the main effect of elevating salinity levels from 4 ppt to 8 ppt was a reduction in the abundance of chlorophytes, particularly Scenedesmus. Phytoplankton samples that were collected when the lake salinity level was 12 ppt were little affected by salinity increases of 2 ppt and 4 ppt, most likely because field samples were already relatively high in salt content. We suggest that further investigations focus on phytoplankton responses to salinity under a range of nutrient regimes that are common to coastal lakes.     

Predation rates of nemertean predators: the case of a rocky shore hoplonemertean feeding on amphipods

Estimates of the predation rates of benthic nemerteans are often based on observations of single individuals, and consequently they may not be representative for all members of a population of these predators. Herein we conducted controlled and repeatable laboratory experiments on the predation rate of the hoplonemertean Amphiporus nelsoni Sánchez 1973, which is common at exposed rocky shores along the central Chilean coast. During the austral fall (April, May 2000), nemerteans were observed in relatively high numbers crawling in the intertidal zone during early morning or late-afternoon low tides. When these nemerteans were offered living amphipods held by a forceps, they immediately attacked the amphipods and fed on them. In the laboratory experiments, nemerteans preferred the amphipod Hyale maroubrae Stebbing, 1899, which is also very common in the natural habitat of A. nelsoni. The nemerteans preyed to a higher extent on small males and non-ovigerous females than would have been expected from their abundance. We suggest that these (non-reproductive) stages of H. maroubrae are very mobile and therefore have a high likelihood of encounters with nemerteans. Predation rates reached maxima when nemerteans were provided prey densities of four or more of their preferred prey species, H. maroubrae, furthermore indicating that encounter rates with prey may affect predation rates. In long-term laboratory experiments, A. nelsoni consumed more amphipods during low tide conditions than during high tide conditions. Many nemerteans in the field prefer particular environmental conditions (e.g. nocturnal low tides), which restricts the time available for successful feeding. In the long-term experiment, predation rates of A. nelsoni never exceeded 0.5 amphipods nemertean^–1 d^–1. Maximum feeding events were 3 or 4 amphipods nemertean^–1 d^–1, but this only occurred during 10 out of a possible 2634 occasions. Nemerteans that had consumed 3 or 4 amphipods during 1 day, consumed substantially less prey during the following days. Towards the end of the long-term experiment, average predation rates decreased to 0.2 amphipods nemertean^–1 d^–1, corresponding to predation rates reported for other nemertean species (0.1–0.3 prey items nemertean^–1 d^–1). We suggest that predation rates from laboratory experiments represent maximum estimates that may not be directly transferable to field populations. Additionally, low predator–prey encounter rates with preferred prey in the field may further limit the predation impact of nemertean predators in natural habitats.     

Estimation of spawning sites in the spotted flagtail, Kuhlia marginata, based on sperm motility

To estimate the spawning site of the spotted flagtail, Kuhlia marginata, sperm motility was examined under conditions of different salinities. The spermatozoa were immotile in 0 and 5 ppt test solutions and in seminal fluid but lived longer in 20–30 ppt. Sperm were most active at 25–35 ppt. Therefore, we considered that spotted flagtail spawn in 20–35 ppt salinity. Because the mean salinity of the Genka estuary is below the optimum required for spawning, the spawning site in Okinawa Island would be seawater. This evidence suggested that the spotted flagtail is a catadromous species. Received: January 26, 2001 / Revised: July 6, 2001 / Accepted: July 24, 2001     

New species of Pogonophryne (Pisces, Artedidraconidae) from the Bellingshausen Sea, Antarctica

A new species of notothenioid fish, Pogonophryne bellingshausenensis n. sp., is described from the Bellingshausen Sea, Antarctica. The new species belongs to the dorsally-spotted “mentella” group of the genus and is characterized by having a short (about 13% SL) mental barbel with a short (about 16% of barbel length), narrow (barely wider than the stalk), and relatively inconspicuous terminal expansion composed of short, irregular, fingerlike processes. Compared to most other dorsally-spotted species of Pogonophryne (“barsukovi”, “marmorata”, and “mentella” groups), P. bellingshausenensis has a relatively wide (about 7% SL) interorbital region. An unspotted patch on the median dorsal surface of the head, posterior to the posttemporal ridges and anterior to the first dorsal fin, has not been observed previously in any dorsally-spotted species. The holotype was collected at 1,947 m, one of the deepest records for any species of Pogonophryne. A revised key to the ten species of the “mentella” group of Pogonophryne is also provided.     

Species composition,seasonal dynamics of quantities and spatial distribution of hydromedusae (Cnidaria: Hydrozoa) in Vostok bay of the Sea of Japan

Hydromedusae (Cnidaria: Hydrozoa) are one of the most common and widely spread plankton organisms. Due to their low quantities in the plankton and complicated species identification, they are poorly observed in zooplankton research works, especially in the Northwestern part of the Sea of Japan. The subjects of the present work are the seasonal dynamics of the spatial distribution and abundance of hydromedusae that inhabit Vostok bay (Peter the Great bay of the Sea of Japan), which were observed from April to November in 2002–2004. The timing of mature specimens was studied for different species. Eighteen species were found. Of these, Coryne sp., Tiaropsis multicirrata (Sars, 1835) and Neoturris breviconis (Murbach et Shearer, 1903) are the first records for Peter the Great Bay; the last two species are the first records for the Northwestern part of the Sea of Japan.     

First Quantitative Study of Rove Beetles in Oklahoma Winter Wheat Fields

Adult rove beetles (Staphylinidae) were sampled every 7–14 days from one winter wheat field located in each of the four major wheat growing regions of Oklahoma during the 1999–2000 and 2000–2001 growing seasons. The number of cereal aphids per tiller, wheat plant growth stage, and wheat tiller density also were estimated. A total of 12 genera representing 13 species of beetles were collected from the field. The density of rove beetles was generally low, ranging from 0.003 beetles per m² in fall to 0.106 beetles per m² in spring. Rove beetle communities differed among seasons. After accounting for the effect of season, there was no statistically significant association between rove beetle community structure and field location, aphid density, wheat plant growth stage, or wheat plant density. Most rove beetle species showed no association with a particular season, however, Aleochara notula Erichson, Lathrobium sp., and Oxypoda sp. were present predominantly in fall, while Bisnius inquitus Erichson was associated with winter. Oxypoda sp. was the most abundant rove beetle in winter wheat fields in spring and was relatively abundant in winter, but was not collected from wheat fields in fall. Tachyporus jocosus Say was present in wheat fields during all seasons. T. jocosus was the most abundant rove beetle species in the winter wheat fields in fall and winter and was the second most abundant species during spring.     

Life-history, thallus ontogeny, and the effects of temperature, irradiance and salinity on growth of the edible green seaweed Gayralia spp. (Chlorophyta) from Southern Brazil

Gayralia K.L. Vinogr. is a monostromatic green alga of commercial importance in the southern Brazil, and its cultivation is being considered. This paper reports some basic aspects of the biology of this poorly known genus. Two populations of Gayralia spp., from outer and inner sectors of Paranaguá Bay, showed an asexual life history with a distinct pattern of thallus ontogeny. In one population (Gayralia sp. 1), zooids developed an expanded monostromatic blade directly, while in the other (Gayralia sp. 2) zooids produced an intermediate saccate stage, before giving rise to a monostromatic blade. Thalli of the two species differ in size and in cell diameter. The effects of temperature (16–30°C), irradiance (50–100 μmol photons m⁻² s⁻¹), and salinity (5–40 psu) on the growth of both populations were assessed. Plantlets of Gayralia sp. 1 from in vitro cultures showed a broader tolerance to all salinity and irradiance levels tested, with the highest growth rate (GR; mean 17% day⁻¹) at 21.5°C and 100 μmol photons m⁻² s⁻¹. Plantlets of Gayralia sp. 1 collected during the winter in the field showed higher GR, ranging from 5% day⁻¹ to 7.5% day⁻¹ in salinities from 20 to 40 psu, and 2.0% day⁻¹ and 4.3% day⁻¹ for plantlets collected during the summer. Gayralia sp. 2 from the field showed highest GR at salinity of 15 psu. These results suggest distinct physiological responses of the two species, in accordance with their distribution: Gayralia sp. 2 is limited to the inner areas of the estuary, while Gayralia sp. 1 grows in outer areas, where salinity values are higher than 20 psu. These data indicate that Gayralia sp. 1 has a higher potential for aquaculture than Gayralia sp. 2 due to its larger thalli, higher GR, and wider tolerance to environmental variations.     

Seabird species associations and affinities to areas covered with sea ice in the northern Greenland and Barents Seas

Species associations and affinity to sea ice among arctic marine birds were studied during ship transects in the northern Greenland and Barents Seas in the period 1980–1984. Associations were investigated at the scale of visual contact, and the sampling units were 10-min periods, corresponding to a transect length of 1.5–3 km. In the Greenland Sea, three or four of the most abundant species, fulmar (Fulmarus glacialis), little auk (Alle alle), Brünnich's guillemot (Uria lomvia) and kittiwake Rissa tridactyla, composed a recurrent group in all years. In the Barents Sea, fulmars, Brünnich's guillemots and kittiwakes were most often clustered. A positive association with sea ice was found in more than one cruise in three seabird species: black guillemots, ivory gulls and little auks, whereas seven other species showed negative association with ice in more than one cruise. The observed species associations and affinities to sea ice reflect similarities in diet among the species involved. Received: 23 February 1994 / Accepted: 12 January 1997     

Nemertean larvae of the ototyphlonemertidae family in the plankton of Peter the Great Bay, Sea of Japan

Larvae of two nemertean species,Ototyphlonemertes (O.) martynovi Chernyshev, 1993 andOtotyphlonemertes (Norenburgia) sp., found in the neritic plankton of Peter the Great Bay, the Sea of Japan are described. The larvae of both species had two statocysts and a pair of eyes, but differed in the number of statoliths and in their tactile cirri. Changes of some traits during ontogenesis are discussed.     

Dorymenia troncosoi sp. nov. (Mollusca Solenogastres: Proneomeniidae), a new species from the South Shetland Islands (Antarctica)

During the Spanish oceanographic expedition BENTART '95, carried out in Antarctic waters off Livingston Island (South Shetland Islands), five small specimens of a new species of Solenogastres-Cavibelonia, Dorymenia troncosoi sp. nov., were collected at a depth of 65–240 m on a silt bottom. The species is characterized by the presence of a pallial cavity with four pouches (a dorsal, two lateral and a ventral pouch), seminal receptacles that open into the spawning ducts through a short duct, radula having 9–11 teeth per row (1 central and 4–5 lateral, all the same size), the end of the copulatory spicules having a cross-section in the shape of a four-pointed star, and abdominal spicules present. These characteristics separate this species from other species of the genus, particularly from Dorymenia profunda, which is the most similar. Received: 9 April 1998 / Accepted: 12 June 1998     

A new genus and species of prickleback (Perciformes: Stichaeidae) from Japan

A stichaeid fish, Xenolumpenus longipterus gen. et sp. nov., is described on the basis of 2 specimens (107.1–114.9 mm in standard length) collected from 167 to 300 m in the northern Sea of Japan off southern Hokkaido, Japan. Xenolumpenus is unique among all known genera of the subfamily Lumpeninae in having all pectoral, pelvic, and anal fin rays elongate and unbranched with fin membranes well-incised. Xenolumpenus longipterus can be further distinguished from all species of the subfamily in having the following combination of characters: dorsal fin XLVI–XLVIII; anal fin II, 28–29; pectoral fin 11; large black blotches on pectoral fin; and black ocellus on caudal fin.     

Growth and survival of the invasive alga, <Emphasis Type="Italic">Caulerpa taxifolia</Emphasis>, in different salinities and temperatures: implications for coastal lake management

The alga Caulerpa taxifolia is an invasive pest species in many parts of the world and has recently become established in several estuaries in south eastern Australia. A major infestation has occurred in Lake Conjola, an intermittently open and closed coastal lagoon in southern NSW. Short term (1 week) laboratory experiments were carried out to investigate growth and survival of fragments of C. taxifolia collected from this outbreak, under a range of salinities (15–30 ppt) and water temperatures (15–30°C). Fronds, stolons and thalli of the alga all displayed similar responses. Many of the algal fragments doubled in size over the week and a maximum growth rate of 174 mm/week was recorded. Fragments showed good growth (> 20 mm/week) at salinities > 20 ppt and temperatures > 20°C. Almost total mortality occurred at salinities lower than 20 ppt and temperatures less than 20°C. Historical records of water quality demonstrate that prior to entrance manipulation in 2001, salinities in Lake Conjola had often dropped to below 17 ppt for extended periods (up to 2 years). This suggests that management of the alga may be improved if the lake was allowed to undergo its normal cycles of opening and closing to the ocean, and that entrance manipulation may be one factor that has influenced the success of this invasive species.