Marine nutrient contributions to freshwater apex predators

Recent investigations into the nutrient cycling of coastal ecosystems have suggested that migratory or anadromous fish could be important vectors of marine nutrients. Anadromous fish have assimilated marine nutrients that would contribute to the nutrient budgets of freshwater systems by excretion, gamete release, or the decay of post-reproductive carcasses. However, the extent to which freshwater predators utilize marine material is not well understood. In systems where anadromous fish temporarily constitute a major portion of the fish community, they may contribute substantially to the diet of piscivorous fish and other predators. Here we show the contribution of anadromous blueback herring, shad, and alewife (Alosa) to diets of large, non-indigenous piscivorous catfish (Ictalurus furcatus) using δ³⁴S and δ¹³C. The spawning anadromous Alosa, captured in tidal freshwater, had enriched δ³⁴S and δ¹³C values compared to resident, native freshwater species. As a result of consuming the anadromous Alosa, the I. furcatus isotope signature shifted towards the marine signal. The isotope analysis revealed that anadromous fish contribute substantially to the diet of most captured I. furcatus. The percentage of anadromous Alosa carbon and sulfur that was incorporated into I. furcatus (≥38 cm total length) ranged from 0 to 84% and 10 to 69%, and had means (±SD) of 42 (±24) and 43 (±16)%, respectively. Although the δ¹⁵N signal of marine-derived biomass is enriched by approximately 3‰ relative to terrestrial or freshwater biomass, it was not as useful as δ³⁴S and δ¹³C for nutrient source owing to trophic fractionation. This study demonstrates that anadromous fish may be a significant source of nutrients to tidal freshwater apex predators. Received: 19 March 1999 / Accepted: 26 October 1999     

Spatial differences in bacterioplankton composition along the Catalan coast (NW Mediterranean) assessed by molecular fingerprinting

Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA gene fragments was used to compare surface bacterioplankton assemblages along the Catalan coast (NW Mediterranean). Samples from three coastal stations were compared with samples taken inside the Barcelona harbour and open sea samples taken during a cruise. The bacterial assemblage of each sample showed a characteristic and reproducible DGGE fingerprint. Between 17 and 35 bands were detected in each sample, and about 40% of the bands accounted for more than 80% of the band intensity in each sample. The presence of bands as well as their relative intensity was used to compare bacterial assemblages. Clear differences between the harbour samples and the coastal samples were evident during all periods. Marked temporal changes in the bacterial assemblages were detectable for the coastal sites, suggesting seasonal succession of coastal bacterioplankton. During each season, two stations presented a very similar bacterial composition (Barcelona and Masnou) whereas bacterial assemblages in Blanes were slightly different. These differences were consistent with the different hydrography of the area. Diversity indices calculated from DGGE fingerprints were relatively similar for all samples analysed, even though harbour samples were expected to present lower diversity values.     

腹毛目纤毛虫皮膜演化的一种特殊形式--卵圆急纤虫无性二分裂期间的形态发生学

对海洋纤毛虫卵圆急纤虫无性分裂过程中的形态发生做了跟踪观察,结果表明,该种的皮膜演化表现了一系列在腹毛目种类中所罕见的特征:1)新老口围带有一临时性汇联为一的阶段;2)左右缘棘毛原基分步出现,即明显的不同步现象;3)大核的改组在细胞分裂开始前即已完成;4)本种后仔虫之棘毛原基的分化既非独立发生又非来自于老结构的反分化,而是紧靠口原基的一侧向外分衍并极可能是孤立地发展而成;5)老的波动膜在形态发生过程中亦无反分化现象,而呈独特的半原基模式.     

Free-living marine nematodes of shrimp culture ponds in Thailand. I. New species of the genera Diplolaimella and Thalassomonhystera (Monhysteridae) and Theristus (Xyalidae)

Three new species belonging to the genera Diplolaimella and Thalassomonhystera of the family Monhysteridae and Theristus of the family Xyalidae are described from shrimp culture ponds near mangrove zones of Khung Kraben Bay, Thailand. Diplolaimella thailandica sp. n. resembles D. dievengatensis but differs from it by features of the ratios b and V, and size of the spicules and tail of the male. Thalassomonhystera siamensis sp. n. resembles T. diplops but differs from it in features of the amphids, ocelli, cloaca and gubernaculum. Theristus (Penzancia) longisetifer sp. n. resembles T. flevensis, T. ambronensis, T. macroflevensis, and T. pratti but differs from them in features of the cervical setae, ventral supplement of the male and others. This revised version was published online in July 2006 with corrections to the Cover Date.     

Functional analysis of plasma prophenoloxidase system in the marine mussel Perna viridis

The role of prophenoloxidase (proPO) system in recognition and phagocytosis of yeast cells by hemocytes was examined in vitro using whole plasma and proPO system isolated from the plasma of the marine mussel, Perna viridis. The proPO was isolated from the plasma by ammonium sulphate precipitation and gel filtration. The final proPO preparation was homogeneous in native PAGE, and could be activated by trypsin, α-chymotrypsin and pronase-E. Laminarin (a polymer of β-1, 3-glucan) and lipopolysaccharides (LPS) from diverse bacterial species effectively activated the isolated proPO, demonstrating the ability of this proenzyme to interact directly with microbial surface components. The susceptibility of proPO activation to inhibition by serine protease inhibitors such as soybean trypsin inhibitor (STI) or p-nitrophenyl-p′-guanidinobenzoate (p-NPGB), indicates that the isolated fraction may contain an integral serine protease domain in an inactive state. The presence of laminarin- or LPS-activated whole plasma of P. viridis facilitated adherence of yeast cells to hemocyte surface as well as eventually stimulated phagocytic uptake of the target cells by hemocytes, and no such hemocytic response was recorded with STI controls. This and other results strongly suggest that the intermediary factors generated during activation of plasma proPO system by non-self molecules play a key role in recognition and opsono-phagocytosis by hemocytes. However, the proPO system isolated from P. viridis plasma, after activation with microbial surface components, failed to show an opsonic effect.     

Sialic acid in hemolymph and affinity purified lectins from two marine bivalves

Sialic acids have been implicated in a variety of complex biological regulatory and signalling events and their functional importance is reflected by their presence in a wide variety of phyla. Potentially they may inhibit intermolecular and intercellular interactions. Lectins that exhibit specificity for sialic acid or sialoglycoconjugates are ubiquitous in the body fluids of invertebrates and this has supported the assumption that these lectins are involved in defense against microbes that express sialic acids on their surfaces. This biological function has also been inferred from the absence of sialic acids in lower invertebrates. However, most invertebrate lectins are heterogeneous and may also bind other ligands. The biological significance of the different carbohydrate specificities are not yet known. We have demonstrated the presence of sialic acids in hemolymph from two marine bivalves, the Pacific oyster Crassostrea gigas (≈15 μg ml⁻¹) and the horse mussel Modiolus modiolus (48–100 μg ml⁻¹) by several different assays. The sialic acid was mostly in free form. Affinity purified lectins from the horse mussel also contained bound sialic acids (2–5 μmol g⁻¹). Oyster hemolymph stimulated the in vitro phagocytosis of bacteria by oyster hemocytes. The stimulation by hemolymph is facilitated by a dialyzable component, that apparently is active irrespective of the binding to sialic acid (BSM). Addition of sialic acid had no significant effect on the in vitro phagocytosis of bacteria by oyster hemocytes.     

Secondary metabolites of Posidonia oceanica (Posidoniaceae)

Posidonia oceanica Delile is an endemic of the Mediterranean Sea. P. oceanica is one of the few marine higher plants of the Mediterranean and plays a significant role in coastal ecosystems of the Mediterranean Sea. In the past, a number of phytochemical investigations with different focus were carried out. The results of these investigations are summarized and appraised here. A total of 51 natural products was reported from P. oceanica, including phenols, phenylmethane derivatives, phenylethane derivatives, phenylpropane derivatives and their esters, chalkones, flavonols, 5α-cholestanes, and cholest-5-enes. Many of the compounds reported for P. oceanica were, however, not detected by appropriate phytochemical methods and some most probably represent artifacts and are no genuine natural products.     

Toward routine,DNA-based detection methods for marine pests

Marine pest incursions can cause significant ongoing damage to aquaculture, biodiversity, fisheries habitat, infrastructure and social amenity. They represent a significant and ongoing economic burden. Marine pests can be introduced by several vectors including aquaculture, aquarium trading, commercial shipping, fishing, floating debris, mining activities and recreational boating. Despite the inherent risks, there is currently relatively little routine surveillance of marine pest species conducted in the majority of countries worldwide. Accurate and rapid identification of marine pest species is central to early detection and management. Traditional techniques (e.g. physical sampling and sorting), have limitations, which has motivated some progress towards the development of molecular diagnostic tools. This review provides a brief account of the techniques traditionally used for detection and describes developments in molecular-based methods for the detection and surveillance of marine pest species. Recent advances provide a platform for the development of practical, specific, sensitive and rapid diagnosis and surveillance tools for marine pests for use in effective prevention and control strategies.