Impact of logging activities in a tropical mangrove on ecosystem diversity and sediment heavy metal concentrations

Productivity of mangrove ecosystems is compromised by anthropogenic activities including over-exploitation of wood. This study set out to understand how different wood harvesting regimes have affected the biodiversity of a tropical ecosystem and to identify relationships between the heavy metal concentrations in the mangrove sediments and tree felling. Soil samples were collected and plant diversity studies carried out on seven sites in the mangrove. Physico-chemical, chemical and mineralogical analyses were done on soil samples and plant population structure, species richness, evenness and diversity index at these sites were calculated. Results showed that soils across sites were characteristically clayey and acidic, with high organic matter content. Minerals identified included quartz, gibbsite, goethite, hematite and kaolinite. Heavy metal concentrations were higher in Sites 6 and 7 with a longer history of anthropogenic activity. There were strong negative correlations between the duration of logging and NO₃-N (r = ?0.838, p = 0.019), total N (r = ?0.837, p = 0.019), NH₄ ⁺-N (r = ?0.844, p = 0.017), Mg = (?0.789, p = 0.035), K (r = ?0.819, p = 0.024), and Na (r = ?0.988, p = 0.002). Sites which had experienced logging for longer periods (sites 3, 6, and 7) had lower nutrient content and lower values for species richness and diversity index. Logging in mangrove ecosystems could alter soil characteristics, decreasing plant diversity and abundance. Logging dynamics around mangrove ecosystems should be considered in the wider strategy for management and conservation of similar mangrove ecosystems.     

Population structure of two northern hemisphere polychaetes,<Emphasis Type="Italic"> Neanthes virens</Emphasis> and<Emphasis Type="Italic"> Hediste diversicolor</Emphasis> (Nereididae), with different life-history traits

The present study compared population genetic structure of two northern hemisphere polychaetes, Neanthes virens (Sars, 1835) and Hediste diversicolor (O.F. Müller, 1776), with different life-history traits. N. virens has a pelagic larval phase that may last as long as 9 days, while H. diversicolor broods its offspring. It was predicted that N. virens populations, especially over relatively short geographic distances, would be more genetically similar than H. diversicolor populations. Sequence data were obtained for two mitochondrial genes, cytochrome c oxidase I (COI) and cytochrome b (cyt b). The COI gene showed no variation in 16 N. virens individuals from 12 locations, and it was not examined in H. diversicolor. The nucleotide sequence of the cyt b gene was examined in 93 N. virens individuals collected in 1992, 1999, and 2000 from 12 localities throughout its range (North America, Europe, Japan) and from 33 H. diversicolor individuals collected in 1999 and 2001 from one locality in eastern Canada and two localities in France (Roscoff and Marseille). In N. virens, one cyt b haplotype was shared by 89% (83 out of 93) and only two other haplotypes were found. Significant population structure was observed in H. diversicolor. In the 33 sequences compared, 18.9% of sites were polymorphic and 12 haplotypes were identified. There were two haplotypes in the Canadian population, three in the Marseille samples, and seven in the Roscoff samples, and no haplotype was found in common between any two sites. These results show that widely separated H. diversicolor populations are strongly differentiated at the cyt b locus. The most plausible interpretation for the low variation at the COI and cyt b loci in N. virens, and for the lack of variation at allozyme loci (based on an initial survey of a smaller subset of populations), is that this species has experienced a drastic bottleneck and that a few remaining lineages recolonized its entire range.     

Phytotoxic effects of phenolic acids from <Emphasis Type="Italic">Merostachys riedeliana,</Emphasis> a native and overabundant Brazilian bamboo

Merostachys riedeliana Rupr. is a native and overabundant bamboo species in the Brazilian Atlantic Forest. Moderate to strong allelopathic activity may be one mechanism that explains this super-dominance and the changes in structure and composition of forest areas occupied by bamboo. This study evaluated the phytotoxic effect of M. riedeliana extracts and fractions and identified their putative allelochemicals. We investigated the presence of allelochemicals in soil collected from stands occupied by M. riedeliana. Furthermore, we evaluated the putative effect of tree allelochemicals, individually and combined, on germination and growth. The aqueous extract of leaves and its ethyl acetate fraction presented the highest inhibitory effects on seed germination and seedling growth. The effect of the extracts and fractions on the target species was species-specific. Neither the individual nor the combined phenolic acids significantly inhibited seed germination; however, a pronounced growth inhibition was observed in M. bimucronata seedlings treated with vanillic acid and in E. verna and M. bimucronata seedlings treated with combined phenolic acids. Isovitexin, vitexin, isoorientin, orientin, and their O-glycoside derivatives, the lactonic dimer of the p-hydroxybenzoic acid and 3,4-methylenedioxymandelic acid were identified in the aqueous extracts and ethyl acetate fraction by Liquid Chromatography-Diode Array Dectector/Electrospray Ionization/Mass Spectrometry (LC-DAD/ESI–MS/MS). The Gas Chromatography-Mass Spectrometer (GC–MS) profile of the same extract and fraction showed the presence of benzoic, benzeneacetic, salicylic, p-hydroxybenzoic, p-hydroxyphenylacetic, vanillic, p-coumaric, protocatechuic, syringic, gallic, m-coumaric vanillylmandelic, 4-methylmandelic, 3,4-methylenedioxymandelic and trans-ferulic acids. The p-benzoic acid and the apigenin 6-C-glucoside (isovitexin) were identified in the soil extract collected from under bamboo-growing areas. Even though laboratory bioassays are not completely predictive of the allelopathic effects that occur in nature, the results of this study provide preliminary evidence of allelopathy as a possible species-specific inhibition mechanism of native species that explain the impoverishment of floristic richness and the functional groups in areas where M. riedeliana is overabundant.     

Insights on plant interaction between dominating species from patterns of plant association: expected covariance of pin-point cover measurements of two species

It has been suggested that in order to infer ecological processes from observed patterns of species abundance we need to investigate the covariance in species abundance. Consequently, an expression for the expected covariance of pin-point cover measurements of two species is developed. By comparing the observed covariance with the expected covariance we get a new type of information on the spatial arrangement of two species. Here the discrepancy between the observed and expected covariance may be thought of as a measure of the spatial configuration of the two species that may indicate underling ecological processes. The method is applied in a case study of Calluna vulgaris and Deschampsia flexuosa on dry heathland sites. The observed covariance of Calluna and Deschampsia at the level of the sites was positively and significantly correlated with the expected covariance. Negative covariance was observed on sites where both Calluna and Deschampsia had a high cover, which is in agreement with the notion that both species form distinct patches. Oppositely, at sites where both species have a low cover, we found that both the expected and observed covariance were positive. The proposed measure for the expected covariance of two species does capture information on the combined spatial configuration of the two species if the species are common. We show how this may be relevant for understanding the underlying ecological processes leading to the observed covariance.     

Trophic specialisation of metazoan meiofauna at the Håkon Mosby Mud Volcano: fatty acid biomarker isotope evidence

We report the results of a detailed investigation on the trophoecology of two dominant meiofaunal species at the Håkon Mosby Mud Volcano (HMMV), a deep-sea cold methane-venting seep. Analyses of fatty acids (FAs) and their stable carbon isotopes were used to determine the importance of chemosynthetic nutritional pathways for the dominant copepod species (morphologically very similar to Tisbe wilsoni) inhabiting the volcano’s centre and the abundant nematode Halomonhystera disjuncta from the surrounding microbial mats. The strong dominance of bacterial biomarkers (16:1ω7c, 18:1ω7c and 16:1ω8c) coupled with their individual light carbon isotopes signatures (δ¹³C ranging from ?52 to ?81‰) and the lack of symbiotic relationships with prokaryotes (as revealed by molecular analyses and fluorescent in situ hybridisation) indicated that chemosynthetically derived carbon constitutes the main diet of both species. However, the copepod showed a stronger reliance on the utilisation of methanotrophic bacteria and contained polyunsaturated FAs of bacterial origin (20:5ω3 and 22:6ω3 with isotope signatures δ¹³C < ?80‰). Instead, the FA profiles of H. disjuncta suggested that sulphide-oxidising bacteria constituted the main diet of this nematode. Therefore, HMMV can be regarded as a persistent deep-sea cold seep, allowing a chemosynthesis-based trophic specialisation by the dominant meiofaunal species inhabiting its sediments. The present investigation, through the determination of the fatty acid profiles, provides the first evidence for trophic specialisation of meiofauna associated with sub-habitats within a cold seep.     

Phytotoxicity in seven higher plant species exposed to di-<Emphasis Type="Italic">n</Emphasis>-butyl phthalate or bis (2-ethylhexyl) phthalate

We investigated phytotoxicity in seven plant species exposed to a range of concentrations (0–500 mg·kg^?1 soil) of di-n-butyl phthalate (DnBP) or bis (2-ethylhexyl) phthalate (DEHP), two representative phthalate esters (PAEs) nominated by USEPA as priority pollutants and known environmental estrogens. We studied seed germination, root elongation, seedling growth, biomass (fresh weight, FW) and malondialdehyde (MDA) content of shoots and roots of wheat (Triticum aestivum L.), alfalfa (Medicago sativa L.), perennial ryegrass (Lolium perenne), radish (Raphanus sativus L.), cucumber (Cucumis sativus L.), oat (Avena sativa) and onion (Allium cepa L.), together with monitoring of plant pigment content (chlorophyll a, b and carotinoids) in alfalfa, radish and onion shoots. Root elongation, seedling growth and biomass of the test species were generally inhibited by DnBP but not by DEHP, indicating a lower level of phytotoxicity of DEHP than of DnBP. MDA contents of four species were promoted by PAE exposure, but not in alfalfa, ryegrass or onion shoots, indicating lower sensitivity of these three species to PAE pollutants. Plant pigment contents were clearly affected under the stress of both pollutants, implying the potential damage to the photosynthetic system of test plants, mainly by decreasing the content of chlorophyll a and b. Results of DnBP and DEHP phytotoxicity to the primary growth of test plants has provided information for the assessment of their environmental risk in the soil and also forms a basis for the further analysis of their toxic effects over the whole growth period of different plant species.     

Free-living marine nematodes from Biscayne Bay,Florida, I. Comesomatidae: the male of Laimella longicauda Cobb, 1920, and description of Actarjania new genus

The male of Laimella longicauda Cobb, 1920 is described as having short arcuate spicules and a gubernaculum with caudally directed apophyses. The genus Paracomesoma Schuurmans Stekhoven, 1950 is reinstated to accommodate species of Laimella sensu Chitwood, 1937. Paramesonchium n. gen. is proposed to accommodate Laimella (?) serialis Wieser, 1954. Actarjania n. gen. (type species A. splendens n. sp.) differs from Sabatieria in having irregular lateral rows of longitudinal punctations and short arcuate spicules with distinctive distal extremities.     

A systematic study of some Black Corals species (Antipatharia,Hexacorallia) based on rDNA internal transcribed spacers sequences

A phylogenetic analysis based on rDNA internal transcribed spacers (ITS) sequences was performed on 15 species of black corals assigned to the genera Antipathes, Stichopathes, Cirrhipathes, Rhipidipathes, Antipathella, Myriopathes and Cupressopathes recorded from the Messina Strait (Mediterranean Sea) and the Bunaken Marine Park (Celebes Sea, Indonesia). The phylogenetic analysis shows that the examined species are grouped in two main branches corresponding to the families Antipathidae-Aphanipathidae and Myriopathidae. While among the Myriopathidae species there is a very small genetic distance, the Antipathidae-Aphanipathidae clade shows a high degree of divergence between different genera. According to this study, the taxon Antipathes? sp. 3 characterised by a bush-like corallum without a well-defined axis, probably belongs to a new undescribed genus of the family Antipathidae.     

Developmental and genetic evidence for the existence of three morphologically cryptic species of<Emphasis Type="Italic"> Crepidula</Emphasis> in northern Chile

The taxonomy of Crepidula has been based principally on shell morphology, but shell characteristics in this genus may be strongly influenced by the substrates they inhabit and are thus of limited use in classification. Four species in this genus are currently recognized from the Chilean coast, of which two, Crepidula dilatata and C. fecunda, are sympatric. These species are morphologically cryptic and differ only in their larval development: C. dilatata has indirect development with a planktonic phase, and C. fecunda direct development within egg capsules. The other two species, C. coquimbensis and C. philippiana, are species that occur within gastropod shells inhabited by hermit crabs and differ from the other species in internal morphology of the shell, developmental features, and geographic distribution. Analyses of nine morphological characters, eight developmental characters, and 26 enzymatic loci were carried out on four Crepidula populations in the Coquimbo region of northern Chile. Four populations of Crepidula were identified based on morphological, developmental, and protein electrophoresis features. Our results suggest the presence of C. coquimbensis plus three morphologically cryptic species including C. dilatata, C. fecunda, and a new previously unrecognized cryptic species. All four populations showed differences in larval development pattern. C. fecunda have indirect development, with free-swimming larvae. The remaining three species have intracapsular metamorphosis, but different modes of larval nutrition. C. dilatata have nurse eggs that are consumed by mechanical destruction; C. coquimbensis engulf nutritional embryos; and the new species eat nutritive embryos by rotation. Protein electrophoresis data support the specific condition of each group with different larval development and endorse the use of developmental differences in taxonomy of Crepidula. Genetic distance shows that C. dilatata and C. fecunda are closely related, and that C. coquimbensis is closer to them than to the new cryptic species.     

Genetic structure of<Emphasis Type="Italic"> Linckia laevigata</Emphasis> and<Emphasis Type="Italic"> Tridacna crocea</Emphasis> populations in the Palawan shelf and shoal reefs

Allozyme variation of 10 populations of Linckia laevigata at 8 polymorphic loci and 13 populations of Tridacna crocea at 6 polymorphic loci were analyzed to compare genetic variability and genetic affinities among reefs in Palawan, Philippines. Two to five populations were sampled from each of four regions: the shelf reefs in (1) northern Palawan and (2) southern Palawan and the offshore reefs in (3) the Kalayaan island group (KIG) in the South China Sea and (4) the Tubbataha shoals in the Sulu Sea. Heterozygosity was highest in populations of L. laevigata from the south shelf of Palawan and populations of T. crocea from the Tubbataha shoals of the Sulu Sea. The lowest heterozygosity estimates were from the reefs of the KIG in the South China Sea, for both species. Overall F _ST values for both species were significant, with an estimated average number of effective migrants per generation (N _EM) of 4.85 (~5 individuals) for L. laevigata and 3.54 (~4 individuals) for T. crocea. Within-region comparisons showed N_EM ranging from 6.29 to 92.34 for L. laevigata and from 3.40 to 6.30 for T. crocea. The higher gene flow among L. laevigata populations relative to T. crocea is consistent with the greater dispersal potential of the former species. Finer scale genetic structuring was evident in T. crocea populations. For both species, the Tubbataha reefs in the Sulu Sea have higher genetic affinity with the populations from the southern shelf of Palawan, while the reefs in the KIG had higher affinity with the northern Palawan shelf reefs. The north and south shelf populations have the least genetic affinity. Genetic patchiness among reefs within regions suggests the importance of small-scale physical factors that affect recruitment success in structuring populations in small island and shoal reef systems in Palawan.     

Differences in the species- and size-composition of fish assemblages in three distinct seagrass habitats with differing plant and meadow structure

Fish faunas were sampled seasonally using a large and a small beam trawl in three seagrass habitats comprising predominantly Amphibolis griffithii or Posidonia sinuosa or Posidonia coriacea, which differ in seagrass and meadow structure. Amphibolis griffithii and P. sinuosa both produce a relatively dense leaf canopy, but the former exhibits a distinct architecture, with the leaf canopy overlying relatively open spaces surrounding woody stems, compared to the uniformly dense blade-like leaves of P. sinuosa which emerge directly from the sediment. In comparison, P. coriacea provides a landscape of patchy seagrass amongst areas of bare sand. Since the latter seagrass habitat contains large areas of sand, fish were also sampled in adjacent unvegetated areas. The number of species and density of fish were greater (P<0.05) in P. sinuosa than in either A. griffithii or P. coriacea. The mean number of species caught using the large trawl ranged from 16 to 24 in the first of these habitats compared to 14–21 and 9–15 in the last two habitats, respectively, and the mean densities ranged between 78 and 291 fish 1000 m^?2 in P. sinuosa compared to 31–59 fish 1000 m^?2 in A. griffithii and 31–59 fish 1000 m^?2 in P. coriacea. The biomass of fish was greater (P<0.05) in both P. sinuosa and A. griffithii than in P. coriacea (4.2–5.3 kg and 3.3–6.2 kg versus 0.7–1.9 kg 1000 m^?2, respectively). Furthermore, the size-structure of fish differed among these habitats, where the median weight of fish was 72.1 g in A. griffithii, compared to 7.5 g and 19.8 g in P. sinuosa and P. coriacea, respectively. Ordination and ANOSIM demonstrated that the species-composition differed markedly among the three seagrass habitats (P<0.001), suggesting that fish species display a distinct preference for particular seagrasses characterised by different architecture. Differences in species-composition among the seagrass habitats partly reflected the size-composition of fish in each habitat. The open space below the canopy of A. griffthii is likely to allow larger fish to occupy this habitat, whereas only small fish would be able to penetrate the dense foliage of P. sinuosa. Differences in species- and size-composition of fish among these habitats may be the result of settlement-sized larvae discriminating between particular seagrass and meadow structures, or fish being subject to different levels of predation and/or accessibility to food or space. The species-composition in P. coriacea was highly dispersed and did not differ from that of unvegetated areas. While several species were associated with both P. coriacea and bare-sand habitats, some species did display a high affinity with the seagrass P. coriacea. This may reflect an association with the sparse and narrower leaves of this seagrass or with the patchy occurrence of the seagrass Heterozostera tasmanica, which commonly occurs as an understorey in this habitat.     

Physiological adaptations of the invasive cordgrass<Emphasis Type="Italic"> Spartina anglica</Emphasis> to reducing sediments: rhizome metabolic gas fluxes and enhanced O<Subscript>2</Subscript> and H<Subscript>2</Subscript>S transport

Cordgrasses of the genus Spartina form dense monospecific stands worldwide, profoundly influencing the ecology of estuaries. One species, Spartina anglica, originated by allopolyploidy in the 1800s and has been particularly prolific as an invasive species worldwide. S. anglica tolerates low-lying estuarine mudflats that its progenitor species and other coastal halophytes cannot. However, very little is known of the physiology of S. anglica. In the present study, an automated flow-through respirometry system was used to quantify metabolic gas fluxes (O₂, H₂S, CO₂, and NH₃) of S. anglica rhizomes. Enhanced physiological mechanisms to transport O₂ and H₂S in both directions between the rhizosphere and the atmosphere were exhibited by S. anglica, but not by the native North American species S. alterniflora. These results suggest that tolerance of anoxia and H₂S may assist S. anglica in colonizing extensively flooded environments. Enhanced sediment oxygenation by S. anglica may be potentially useful for phytoremediation of contaminated sediments, since microbial degradation of organic pollutants is often limited by O₂ availability.     

Effect of arsenic species on the growth and arsenic accumulation in <Emphasis Type="Italic">Cucumis sativus</Emphasis>

The effects of arsenic (As) species, such as As(III), As(V) and dimethylarsinic acid (DMA), on the accumulation of As in cucumber (Cucumis sativus), as well as on its growth in a soil mesocosm were evaluated. When Cucumis sativus was cultivated in soils contaminated with 20 and 50 mg/kg of As(III), As(V) or DMA for 40 days, the growth was markedly inhibited by the inorganic As (As(III) and As(V)) rather than the organic As (DMA). Irrespective of the As species, the As concentrations accumulated in Cucumis sativus increased with increasing As concentration in the soil. The As bioaccumulation factors from soil into the tissue of Cucumis sativus were 17.5–35.4, 29.3–42.7 and 17.6–25.7 for As(III), As(V) and DMA, respectively. In addition, the As translocation factors from the roots to shoots were 0.025–0.031, 0.018–0.032 and 0.014–0.026 for As(III), As(V) and DMA, respectively. In conclusion, Cucumis sativus mainly accumulated As in its roots rather than its shoots and easily accumulated inorganic rather than organic As from the soil into its tissue.     

Patterns of gamete incompatibility between the blue mussels<Emphasis Type="Italic"> Mytilus edulis</Emphasis> and<Emphasis Type="Italic"> M</Emphasis>.<Emphasis Type="Italic"> trossulus</Emphasis>

Previous research on gametic incompatibility in marine invertebrates suggests that for highly dispersive marine invertebrate species, barriers to fertilization among closely related taxa are often incomplete and sometimes asymmetric. The nature of these barriers can dramatically affect the patterns of gene flow and genetic differentiation between species, and thus speciation. Blue mussels, in the genus Mytilus, are genetically distinct in allopatry yet hybrids are present wherever any two species within the group co-occur. The present study sampled M. edulis (L.) and M. trossulus (Gould) in May and June 2001 from the East Bay section of Cobscook Bay, Maine, USA (latitude 44°56′30″N; longitude 67°07′50″W), where the two species are sympatric. Gamete incompatibility was investigated in a series of laboratory fertilizations carried out in July 2001. The proportion of fertilized eggs typically exceeded 80% at sperm concentrations of 10³–10⁴ ml^?1 among intraspecific matings (n=18), but was <30% even at sperm concentrations in excess of 10⁵–10⁶ ml^?1 for interspecific matings (n=13). Further analysis indicated that approximately 100- to 700-fold higher sperm concentrations were required to achieve 20% fertilization in interspecific matings relative to intraspecific matings, indicating strong barriers to interspecific fertilization. The proportion of fertilized eggs did not follow this general pattern in all matings, however. The eggs from two (out of five) M. edulis females were almost as receptive to M. trossulus sperm as they were to M. edulis sperm. In contrast, the eggs from all M. trossulus females (n=3) were unreceptive to M. edulis sperm, suggesting that fertilization barriers between these species may be asymmetric. Given the experimental design employed in this study, the results are also consistent with a strong maternal or egg effect on the level of interspecific gamete compatibility in M. edulis.     

Variation in fertilisation abilities between hemiclonal hybrid and sexual parental males of sympatric water frogs (<Emphasis Type="Italic">Rana lessonae</Emphasis>,<Emphasis Type="Italic"> R. esculenta</Emphasis>,<Emphasis Type="Italic"> R. ridibunda</Emphasis>)

In many species, males and females mate with multiple partners, which gives rise to sperm competition and multiple paternity. The experiments on water frogs presented here demonstrate that such sperm competition can affect the structure and dynamics of mixed-species communities. The hybrid frog Rana esculenta (LR) mates with one of its parental species, usually R. lessonae (LL), although in some areas R. ridibunda (RR), to regain the premeiotically eliminated parental genome ("hybridogenesis"). Mixed LL/LR-populations are stable although hybrid numbers should continuously increase at the expense of parental animals, because of differences in female fecundity and other factors. This would finally lead to the extinction of the sexual host, followed by that of the sexual parasite, unless the reproductive superiority of R. esculenta is reduced by other factors, such as lower hybrid male fertility. Eggs from LL- and LR-females were fertilised in vitro by single- and multi-male sperm suspensions of LL-, LR- and RR-males. In all experiments, the proportion of offspring sired by R. esculenta sperm was significantly lower than that sired by R. lessonae or R. ridibunda sperm. Gonad mass, sperm morphology, sperm swimming velocity, and sperm survival did not explain these differences in fertilisation success; nor did gamete recognition and compatibility. Sperm density was the only trait that paralleled fertilisation success, but it offers no explanation either, because densities were equalised for the in-vitro fertilisations. In natural LL/LR populations, the significantly smaller amount, poorer competitive ability and lower long-term survival of R. esculenta compared to R. lessonae sperm will reduce the initial reproductive superiority of hybrids and contribute to the stabilisation of mixed water-frog populations. Differences in fertilisation ability are also likely to be relevant for the structure and dynamics of several other systems with encounters between eggs and sperm from different genotypes, ecotypes, ploidy levels and/or species.     

Ecology of a corallivorous gastropod,<Emphasis Type="Italic"> Coralliophila abbreviata</Emphasis>, on two scleractinian hosts. I: Population structure of snails and corals

Despite their potential importance in structuring reef communities, invertebrate corallivores and their population structures are poorly understood. We found distinct differences in the population structures (length-frequency distribution and sex ratio) of the corallivorous gastropod Coralliophila abbreviata residing on two coral-host taxa, Montastraea spp. and Acropora palmata, in the Florida Keys. In each of two survey years, around 50% of the Montastraea spp. colonies were infested, with a mean snail density of eight snails per infested colony (range 1–45), while around 20% of A. palmata colonies harbored three snails per infested colony (range 1–23). Variation in patterns of snail occurrence was also observed within a host taxon. A. palmata occurred in low- and high-density stands (0.4 and 1 colony m^–2, respectively, at the initial survey) at different sites. Hurricane Georges struck the area in September 1998. When resurveyed in 1999, density of colonies in low-density stands had decreased by 75% to 0.1 colonies m^–2. This decrease was accompanied by a doubling in the proportion of colonies infested with snails (from 19% to 46%) and an increase in snail density per infested colony (from 3.7±3.3 SD to 5.4±4.6 SD) as snails apparently concentrated on surviving A. palmata. In contrast, sites with high density A. palmata stands (thickets) retained colony densities of about ~1 colony m^–2 among years, while snail infestation increased only from 9% to 14% of colonies surveyed and snail density essentially remained unchanged (from 2.7±1.8 to 2.9±1.9 snails per infested colony). Snails collected from Montastraea spp. were shorter than those from A. palmata in low-density stands and were longest on A. palmata in thickets. On both host taxa, female snails were longer than males. The sex ratio of snails on Montastraea spp. hosts was even (1:1), while that of snails on A. palmata was skewed (70% males). Factors that could explain observed differences in size structure and sex ratio between Coralliophila populations on the two coral host taxa include: differential susceptibility to predators, influence of host tissue nutritional quality and/or secondary metabolite content, and genetic differences (cryptic species). The host-specific characteristics of C. abbreviata populations imply that the impact of gastropods on reef communities will vary with the coral species composition.     

Characteristics of residual organochlorine pesticides in soils under different land-use types on a coastal plain of the Yellow River Delta

The residual levels of organochlorine pesticides (OCPs) were examined in soils covering five types of land use along a salinity gradient on the Yellow River Delta. The most prominent OCPs were dichlorodiphenyltrichloroethane (∑DDT, arithmetic mean = 5.11 μg kg^?1), hexachlorocyclohexane (∑HCH, 1.69 μg kg^?1) and ∑endosulfan (10.4 μg kg^?1). The spatial variability of OCPs composition shifted from γ-HCH and o,p′-DDT dominated pesticides in coastal soils to p,p′-DDE dominated pesticides in inland soils. In different land-use types, the percentages of β-HCH and p,p′-DDE are characterized by more recalcitrant components in decreasing order of vegetable fields, cereal fields, cotton fields, wetlands and tidal flats with increasing soil salinity. However, the less recalcitrant components, γ-HCH and o,p′-DDT, showed an opposite trend. Endosulfan sulfate predominated in all land-use types. Residual levels of β-HCH were affected by soil organic matter. The correlations between γ-HCH and clay content and between p,p′-DDE, o,p′-DDT and salinity might associate with the influence of sediment cotransport by the Yellow River and the density of anthropogenic activities in coastal region. Depth distribution of the OCPs in typical soil profiles also implied that local historical usage and sediment transport by the Yellow River both affected the OCPs residual in this region.     

Zum protonephridialsystem mariner gastrotrichen der ordnung macrodasyoidea

The protonephridia of marine gastrotrichs are described from Paradasys subterraneus Remane, Turbanella cornuta Remane, and three other species of the Turbanellidae. Both genera have several terminal organs in serial distribution. Paradasys has 6, Turbanella 4 groups of protonephridia. In Paradasys, 3 protonephridial tubules form a continuous system, while in Turbanella such a system consists of 2 to 4 (5) separate protonephridial tubules.     

Geographical expansion of the invader <Emphasis Type="Italic">Caprella scaura</Emphasis> (Crustacea: Amphipoda: Caprellidae) to the East Atlantic coast

Caprella scaura (Templeton in Trans Entomol Soc Lond 1:185–198, 1836) is a native species to the western Indian Ocean. It was first described from Mauritius and later reported from several regions of the world. During the last decade, the species spread out of the Adriatic Sea, and in 2005, C. scaura was reported in Gerona, on the north-eastern coast of Spain. The present study shows the recent rapid expansion of the species to the East Atlantic. During a sampling survey of harbours along the Strait of Gibraltar (Dec 2009–June 2010), we found high densities of C. scaura associated with the bryozoans Zoobotryon verticillatum Della Chiaje, 1822, in Chipiona and Bugula neritina (L.) in Cádiz, Atlantic coast of southern Spain; on the other hand, during May 2009, an important population of C. scaura was also found in the Canary Islands (Tenerife) associated with aquaculture resources. A total of 1,034 individuals of C. scaura were studied, and we confirm that the populations are effectively established, with high densities and reproducing females during the whole year. The population from Cádiz was characterised by smaller specimens but a higher number of eggs per female. These differences could be related to environmental conditions, mainly sea water temperature and to other factors such as competition with other species, or availability of food or substrate. Significant correlation was found between female size and number of eggs in the three populations, but egg size did not vary with female body length. The morphometric relation length/width of the second gnathopod was also calculated and compared between sexes: larger males presented longer gnathopods at the three sites. The most probable introduction vector of this species is shipping; in fact, the Strait of Gibraltar is characterised by an intense shipping traffic. Also, we have observed that the native Caprella equilibra Say, 1818, is being displaced by C. scaura in the harbour of Cádiz, where this species reach densities of 35,945 ind/1,000 g of B. neritina. Further experimental studies are necessary to explore the potential danger of this species, which might spread into natural habitats too.     

Free-living marine nematodes from Biscayne Bay,Florida, II. Oncholaimidae: descriptions of five new species and one new genus (Meyersia)

A new genus, Meyersia, and five new species of the nematode family Oncholaimidae, are described from Biscayne Bay, Florida, and environs, viz., Metoncholaimus pelor n. sp., M. amplus n. sp., Meyersia major n. gen., n. sp., M. minor n. sp., and Filoncholaimus prolatus n. sp. Also included in the genus Meyersia are Adoncholaimus bandaenis Kreis, 1932 and A. meridionalis Kreis, 1932.