The vertical distribution of Chthamalus montagui and Chthamalus stellatus (Crustacea,Cirripedia) in two areas of the NW Mediterranean Sea

The Mediterranean Sea is characterised by a small tidal range (0.3–1 m). Despite this, intertidal communities are well established and their upper limits often extend above mean high water level. Organisms living in the intertidal region and in the supralittoral zone rely on both tides and wave action to perform their biological functions. Lack of food, desiccation and predation are common stresses in such a harsh environment. The present study deals with the vertical distribution of two species of intertidal barnacles, Chthamalus montagui Southward and Chthamalus stellatus (Poli), which are the main constituents of the barnacle belt along Mediterranean rocky shores. Previous work, carried out in the Atlantic, showed that where the distribution ranges of the two Chthamalus species overlap, C. montagui is more common in the upper barnacle zone while C. stellatus is dominant lower down. The main aims of our study are: (1) to establish if there is a relationship between position and extension of the barnacle belt on the shore and tidal range and/or wave exposure, (2) to test the hypothesis that in the study areas C. montagui is more abundant than C. stellatus high on the shore, and that the pattern is reversed lower down. Barnacle populations were monitored in summer 1998 in the Gulf of Genoa (Ligurian Sea) and in the Gulf of Trieste (North-Adriatic Sea). The two areas differ in tidal range and hydrodynamism, the former presenting quite strong wave action and a tidal range of 30 cm, the latter having limited wave action and 1 m tidal range. Three shores were randomly selected in each gulf and two transects on each shore. Counts of barnacles in 10 ^* 10 cm quadrats were done at different shore heights along each transect. The data was subjected to analysis of variance. Results showed that a more pronounced hydrodynamic regime corresponded to a shift of the barnacle belt towards the higher shore (Gulf of Genoa), while in more sheltered areas (Gulf of Trieste), the barnacle distribution was confined to the intertidal region. The relative spatial distribution of C. montagui and C. stellatus within the barnacle belt varied locally, even between transects on the same shore, and this obscured the distribution pattern along the vertical gradient. Nevertheless, it was still possible to conclude that at mid and high shore in Genoa, C. stellatus was more abundant than C. montagui, while in Trieste the pattern was reversed.     

Settlement and post-settlement processes limit the abundance of the geniculate coralline alga Calliarthron on subtidal walls

Cover of geniculate coralline algae is significantly greater on subtidal platforms than on vertical walls in a central California kelp forest. To determine the cause(s) of this pattern, settlement and growth of Calliarthron were compared on horizontal and vertical substrata attached to platforms or walls. Recruitment on horizontal substrata attached to reef walls indicated that spores were abundant along the walls. Densities of recruits were significantly smaller on vertical substrata attached to walls than on horizontal substrata attached to platforms, indicating that Calliarthron settlement is reduced on vertical substrata. Growth of basal crusts and the densities of fronds were also significantly greater on horizontal substrata attached to platforms than on vertical substrata attached to walls. Irradiance reaching wall surfaces was less than irradiance reaching platform surfaces. We suggest that light reaching wall surface is low enough to affect Calliarthron growth. These results indicate that the low abundance of Calliarthron on subtidal walls is a result of poor recruitment and slow growth.     

Taxonomy and distribution of Sargassum (Phaeophyceae) in the Gulf of Thailand

Ten species of Sargassum (Sargassaceae, Phaeophyceae) were found along the Gulf of Thailand. Morphological characteristics of Sargassum baccularia (Mertens) C.A. Agardh, S. binderi Sonder, S. cinereum J.G. Agardh, S.crassifolium J.G. Agardh, S. longifructum Tseng et Lu, S. oligocystum Montagne, S. polycystum C.A. Agardh, S. siliquosum J.G. Agardh, S. swartzii (Turner) C.A. Agardh and one unidentified species were examined and are described in detail. The most common species were S. polycystum distributed widely in almost all the study sites, S. crassifolium restricted to Prachuap Khirikhan Province, S. longifructum restricted to Chumphon Province, S. siliquosum restricted to Surat Thani Province and one unidentified species restricted to Songkhla Province. Three species (S. cinereum, S. longifructum and S. swartzii) are new records for the algal flora of Thailand. Five species (S. baccularia, S. cinereum, S. longifructum, S. polycystum and the unidentified species) belong to the section Zygocarpicae (J.G. Agardh) Setchell.     

Settlement and early survival of red coral on artificial substrates in different geographic areas: some clues for demography and restoration

The red coral Corallium rubrum (L 1758) is a long-lived, slow-growing gorgonian, endemic to Mediterranean rocky bottoms. Because of its high economic value, red coral has long been harvested, and most populations have been depleted. In the present study, 54 marble tiles were placed in June 2003 within red coral populations over 3 different geographic areas (Calafuria–Livorno and Elba MPA in Italy and Medes Islets MPA, in Spain), on vertical cliffs between 25 and 35 m. In each area 2 different sites were randomly selected. Tiles were subsequently sampled photographically. Between July and August 2003 red coral recruits settled on tiles in all the geographic areas and sites, exhibiting wide variability in their density. On the basis of a 2-factors nested ANOVA a significant variability between different sites at a few hundred metres distance occurred, indicating high variations in the recruitment process within the same red coral population. Mortality, measured in June 2004, widely varied between different geographic areas.     

An experimental test of the effects of variation in recruitment intensity on intertidal community composition

The rocky intertidal has been a model system for experimentally testing hypotheses regarding the factors that structure natural communities. Many ecologists have proposed that changes in the intensity of recruitment of individuals into a community should influence community structure. Past work investigating this hypothesis has primarily been surveys of recruitment and community structure across large spatial scales. Surprisingly, no researchers to date have manipulated recruitment into a rocky intertidal community to assess the response of interactions of the whole community to variation in recruitment intensity. We manipulated the densities of Balanus glandula and Chthamalus spp. recruits across a four-fold difference at two sites spanning the Monterey Bay, California, USA, to experimentally test if differences in recruitment intensity influenced initial changes in community composition and if these changes persisted through time. The results of this work indicate that differences in recruitment influence community composition initially, but that these changes can be short-lived.     

Demersal schooling prior to settlement by larvae of the naked goby

Synopsis Field observations and collections indicate that the naked goby, Gobiosoma bosci, undergoes a near-bottom schooling phase prior to settlement. The size of these demersal larvae was intermediate between the sizes of larvae collected in plankton tows and of metamorphosed juveniles collected from the benthos. Two larvae that were captured unharmed quickly settled and metamorphosed. Otoliths of demersal larvae contained 20–41 daily increments. Most larvae were in schools made up of at least 25 individuals although single larvae were also seen. The dispersion pattern of demersal larvae was far more aggregated than that of recently settled juveniles indicating that larvae in schools probably do not settle to the benthos en masse.     

Paralytic shellfish toxin profile in strains of the dinoflagellate Gymnodinium catenatum Graham and the scallop Argopecten ventricosus G.B. Sowerby II from Bahía Concepción, Gulf of California, Mexico

Gymnodinium catenatum Graham is a paralytic shellfish poison (PSP) producer that was described for the first time from the Gulf of California in 1943. During the last decade, its distribution along the Mexican Pacific coastline has increased. In Bahía Concepción, a coastal lagoon on the western side of the Gulf of California, G. catenatum has been linked to significant PSP concentrations found in mollusks. In this study, we describe the saxitoxin profile of 16 strains of G. catenatum, and catarina scallops (Argopecten ventricosus) from Bahía Concepción. Toxins were analyzed by HPLC with post-column oxidation and fluorescence detection. The average toxicity of the G. catenatum strains was 26.0±6.0 pg and 28.0±18.0 pg STX eq/cell after 17 and 22 days of growth, respectively. Ten toxins were recorded, but only dcSTX, dcGTX2, dcGTX3, C1, and C2 were always present in all strains at both growth stages. Since toxin profiles in scallops were similar to the cultures, biotransformations are not significant in catarina scallop. NeoSTX, GTX2, GTX3, and B2 were present in some G. catenatum strains and their presence varied with the age of the culture. In scallop samples, dcSTX, dcGTX2, and dcGTX3 were the most abundant toxins, and from the C-toxin group, only C2 was found. This unique toxin profile can be used as a biomarker for this population, when compared with strains of G. catenatum from other geographic regions.     

The biology of coral metamorphosis: molecular responses of larvae to inducers of settlement and metamorphosis

Like many other cnidarians, corals undergo metamorphosis from a motile planula larva to a sedentary polyp. In some sea anemones such as Nematostella this process is a smooth transition requiring no extrinsic stimuli, but in many corals it is more complex and is cue-driven. To better understand the molecular events underlying coral metamorphosis, competent larvae were treated with either a natural inducer of settlement (crustose coralline algae chips/extract) or LWamide, which bypasses the settlement phase and drives larvae directly into metamorphosis. Microarrays featuring > 8000 Acropora unigenes were used to follow gene expression changes during the 12 h period after these treatments, and the expression patterns of specific genes, selected on the basis of the array experiments, were investigated by in situ hybridization. Three patterns of expression were common—an aboral pattern restricted to the searching/settlement phase, a second phase of aboral expression corresponding to the beginning of the development of the calicoblastic ectoderm and continuing after metamorphosis, and a later orally-restricted pattern.     

Competition and the distribution of spring peeper larvae

Studies of tadpole distributions have shown that despite overlapping affinities for semipermanent and permanent ponds, distributions of the spring peeper (Pseudacris crucifer) and the green frog (Rana clamitans) tend to be nonoverlapping. Because spring peepers are believed to be poor competitors, I hypothesized that competition from green frog larvae limits the distribution of spring peeper larvae. I stocked field enclosures with a constant density of spring peeper larvae, and one of four densities of green frog larvae (a target-neighbor design). Increased green frog density had a small effect on metamorphic size and no effects on survivorship, larval period or growth rates of spring peepers. In contrast to these small interspecific effects, green frogs had a large effect on their own performance. Intraspecific competition resulted in a 50% decline in growth rate and an 11% decline in metamorphic size. These results suggest that the species are segregated in resource use, or that compared with green frogs, spring peepers are better able to cope with depressed resource densities. In either case, this field experiment provides no evidence that interspecific competition from green frogs limits distributions of spring peepers. Other factors such as predation and breeding site choice by adults may contribute to the absence of spring peeper larvae from many semipermanent and permanent ponds.     

Spatial and temporal patterns in the recruitment of the intertidal barnacle Chthamalus malayensis Pilsbry (Crustacea: Cirripedia) on the equatorial shores of Peninsular Malaysia and Singapore

Spatial and temporal variation in the recruitment of the intertidal barnacle Chthamalus malayensis was examined over one year (September 2003-August 2004) on the equatorial shores of southern Peninsular Malaysia and Singapore. A nested sampling design was applied for the first time on these shores, over three spatial scales - hundreds of kilometres, kilometres to tens of kilometres and tens of metres - and temporal variation was determined through monthly sampling of recruits. Shores within 2° north of the equator on the East and West coasts of southern Peninsular Malaysia and the southern coast of Singapore were selected as study sites. Generally, all three coasts recruited throughout the year, with varying intensities. There was a clear regional pattern, where the largest number of recruits was found on the East Coast of Malaysia, and the least in Singapore. Analyses of variance (ANOVA) showed that variability occurred on the smallest scale, but only in nine of the twelve months examined, consequently resulting in significant temporal and spatial interaction. Calculated variance components indicated that small-scale variation accounted for most of the overall variability. The potential causes of the spatial and temporal patterns of C. malayensis recruitment, and implications on tropical-temperate comparisons will be discussed.     

Effect of rock type on the recruitment and early mortality of the barnacle Chthamalus montagui

Discontinuities in distribution of sessile species due to changes in available habitat have rarely been investigated. In the English Channel, soft sedimentary rocks including chalk could potentially present a barrier to eastward range extension of the southern barnacle Chthamalus montagui. To test the effect of rock type on recruitment and mortality, prepared settlement tiles of four calcareous rocks that form important platforms close to existing limits of distribution were fixed to the shore at a site in south-west England, known to have consistently high larval settlement. Prior to fixation, the roughness parameter “R_a” and Potential Settlement Sites (PSS) index was measured. Recruitment was monitored photographically on four occasions during the settlement season and subsequent mortality for 7 months after the settlement season. By the end of the settlement season, recruitment on the hard Kimmeridge Cementstone was significantly less than on the other three rock types and attributed to low surface roughness and fewest Potential Settlement Sites (PSS), yet only 28% of variance could be attributed to PSS. Post-recruitment mortality was more variable, however after 7 months there were significant differences between rock types. Simultaneous surveys of post-recruitment mortality in natural populations showed that although recruitment on chalk can potentially be high, survivorship was relatively low. Thus rock type could be influential in setting species geographical limits.     

The distribution of Paenibacillus larvae spores in adult bees and honey and larval mortality, following the addition of American foulbrood diseased brood or spore-contaminated honey in honey bee (Apis mellifera) colonies

Within colony transmission of Paenibacillus larvae spores was studied by giving spore-contaminated honey comb or comb containing 100 larvae killed by American foulbrood to five experimental colonies respectively. We registered the impact of the two treatments on P. larvae spore loads in adult bees and honey and on larval mortality by culturing for spores in samples of adult bees and honey, respectively, and by measuring larval survival. The results demonstrate a direct effect of treatment on spore levels in adult bees and honey as well as on larval mortality. Colonies treated with dead larvae showed immediate high spore levels in adult bee samples, while the colonies treated with contaminated honey showed a comparable spore load but the effect was delayed until the bees started to utilize the honey at the end of the flight season. During the winter there was a build up of spores in the adult bees, which may increase the risk for infection in spring. The results confirm that contaminated honey can act as an environmental reservoir of P. larvae spores and suggest that less spores may be needed in honey, compared to in diseased brood, to produce clinically diseased colonies. The spore load in adult bee samples was significantly related to larval mortality but the spore load of honey samples was not.     

Geographic distribution of the bathypelagic genus paraeuchaeta (Copepoda,Calanoida)

The geographic distribution of the bathypelagic calanoid genus Paraeuchaeta was investigated by examining midwater trawl and plankton net samples collected mostly from depths exceeding 1000 m throughout the world's oceans. Of the 81 species referred to Paraeuchaeta, the geographic ranges of about 50 species could be defined with reasonable certainty. Contrary to early authors, the number of species having a worldwide distribution was surprisingly small (12 species or 15% of the 81 species of the genus) as compared to common species endemic to various geographic regions (34 species or 42% of the total of 81). Almost twice as many species were found in the Indo-Pacific Ocean as in either the Atlantic or the Southern Ocean. Faunistically, the northern Atlantic, mid-Atlantic, northern Pacific, East Pacific, Indo-West Pacific, and Southern Ocean were distinct in terms of endemic species. A number of species were found to be endemic to highly productive areas, where they were usually very abundant. Rare species, on the other hand, were generally found to be widely distributed, although some were too rare for their range to be determined with certainty. To explain these findings, the following hypothesis is proposed: Bathypelagic calanoids endemic to and abundant in eutrophic areas are those adapted to eutrophic conditions of their habitats and therefore cannot expand their ranges into contiguous oligotrophic waters even if the other environmental conditions are favorable. Other species, on the other hand, generally have extensive geographic ranges because of their survival ability in widely expanding oligotrophic conditions and the absence of physicochemical barriers at bathypelagic depths of the world's oceans.     

Inhibitory Effects of Mediterranean Sponge Extracts and Metabolites on Larval Settlement of the Barnacle Balanus amphitrite

One of the most promising alternative technologies to antifouling paints based on heavy metals is the development of coatings whose active ingredients are compounds naturally occurring in marine organisms. This approach is based on the problem of epibiosis faced by all marine organisms and the fact that a great number of them cope with it successfully. The present study investigated the antifouling activity of a series of extracts and secondary metabolites from the epibiont-free Mediterranean sponges Ircinia oros, I. spinosula, Cacospongia scalaris, Dysidea sp., and Hippospongia communis. Antifouling efficacy was evaluated by the settlement inhibition of laboratory-reared Balanus amphitrite Darwin cyprids. The most promising activity was exhibited by the metabolites 2-[24-acetoxy]-octaprenyl-1-4-hydroquinone (8a), dihydrofurospongin II (10), and the alcoholic extract of Dysidea sp.     

The spatio-temporal distribution of adult Ceutorhynchus assimilis in a crop of winter oilseed rape in relation to the distribution of their larvae and that of the parasitoid Trichomalus perfectus

The spatio-temporal distribution of Ceutorhynchus assimilis Payk. (Coleoptera: Curculionidae) adults caught in a rectangular grid of flight traps in a crop of winter oilseed rape (Brassica napus L.) was mapped and was analysed using Spatial Analysis by Distance IndicEs (SADIE). Their distribution was compared to that of their larvae and that of their parasitoid Trichomalus perfectus (Walker) (Hymenoptera: Pteromalidae) in pods. The distribution of immigrating C. assimilis adults was consistent with their arrival at the crop boundaries and movement within the crop towards its centre. Adult C. assimilis were aggregated at all times, invasion being on two fronts, leading to the formation of two major clusters within the crop. Large areas of the crop remained relatively unpopulated. During the emigration phase, numbers declined simultaneously in all parts of the crop. The distributions of adult and larval C. assimilis and of larval T. perfectus were spatially associated. The distribution of the parasitoid did not show a density dependent relationship with that of its host. We discuss the movements of insects which underlie their population distributions, the value of integrating spatial information into improved management strategies for C. assimilis and the potential for the spatial targeting of insecticides to reduce the amount applied and to conserve T. perfectus.     

Effects of microhabitat characteristics on the settlement and recruitment of a coral reef fish at two spatial scales

Populations of fishes on coral reefs are replenished by the settlement of pelagic larvae to demersal populations. Recruitment varies spatially and temporally and can exert strong effects on the dynamics of reef fish populations. This study examined the effect of microhabitat characteristics on small-scale and large-scale recruitment variation in the three-spot damselfish, Stegastes planifrons (Cuvier). Comparison of 0.25-m² quadrats occupied by three-spots with randomly sampled null quadrats showed that three-spots quadrats contained a higher percent cover of the coral Montastrea annularis than would be expected at random. Manipulative experiments on three types of 1.0-m² patch reefs (living M. annularis, dead Porites Porites and dead Acropora palmata) patch reefs on showed that this non-random distribution was established by microhabitat choice during settlement and not by differential post-settlement survival. The presence of conspecific juveniles did not affect settlement. Recruitment was monitored at nine sites on three islands over 3 years. Recruitment showed no consistent pattern in the relative levels of recruitment among sites. Similarly, no consistent relationship emerged between recruitment levels and microhabitat characteristics at the nine sites. For example, at this large scale, the percent cover of M. annularis explained variation in recruitment in only 1 out of 3 years. These results suggest that small-scale recruitment patterns are influenced by microhabitat choice during settlement, but that these habitat effects do not scale up to influence large-scale variation in recruitment.     

Negative dietary effects of Colorado potato beetle eggs for the larvae of native and introduced ladybird beetles

Aphidophagous ladybird beetles (Coleoptera: Coccinellidae) are attracted to and feed heavily on aphids, but many species will also feed opportunistically on other prey that they encounter. In potatoes (Solanum tuberosum L.) in Washington State, USA, coccinellids feed on both green peach aphids (“GPA,” Myzus persicae Sulzer) and eggs of the Colorado potato beetle (“CPB,” Leptinotarsa decemlineata Say). The guild of aphidophagous ladybirds includes two native species, Hippodamia convergens Guérin-Méneville and Coccinella transversoguttata Brown. Recently, an introduced species, Coccinella septempunctata L., has invaded and apparently displaced its native congener. A second exotic, Harmonia axyridis Pallas, has colonized the area and is becoming more abundant. We compared larval development of each species on a monotypic diet of GPA, a monotypic diet of CPB eggs, or a mixed diet of both GPA and CPB eggs. Our goal was to answer two questions: (1) do larvae of the four ladybird species benefit from including CPB eggs in their diet and (2) do the four ladybird species differ in their ability to utilize CPB eggs as prey? No larva of any species completed development on a pure diet of CPB eggs, and survivorship was highest for all species when they fed on a pure diet of GPA. One native species, H. convergens, and one exotic species, H. axyridis, exhibited significantly lower survivorship on a mixed diet of both CPB eggs and GPA, compared to a pure GPA diet; H. axyridis also took longer to develop from egg to adult when both prey were provided. Survivorship of the two Coccinella spp. was not altered by the inclusion of CPB eggs with GPA, although CPB eggs lengthened the development time of C. transversoguttata. Adult size was not consistently affected by diet for any of the coccinellids. Overall, no ladybird species benefited from the inclusion of potato beetle eggs in its diet. The two Coccinella species responded similarly to the inclusion of CPB eggs, and so we would not expect any difference in the success of coccinellid larval development in potato fields following the replacement of C. transversoguttata by C. septempunctata. Hippodamia convergens and H. axyridis, the two species whose survivorship was depressed by combining CPB egg and aphid prey, were also the two species that consumed the greatest number of CPB eggs during successful larval development. A comparison of total egg consumption by each species cohort suggested that displacement of the other species by H. axyridis would not alter CPB biological control, because the higher per capita feeding rate by H. axyridis larvae compensated for individuals’ greater mortality risk on a diet including CPB eggs.     

Toxicity of the limonoid allelochemical cedrelone to noctuid larvae

The limonoid cedrelone, a constituent of Cedrela toona and C. odorata (Meliaceae) was evaluated as a larval growth inhibitor for the polyphagous noctuids Peridroma saucia and Mamestra configurata by examining its effects on development and feeding behaviour. Cedrelone significantly inhibited growth of different larval instars when administered orally (in artificial diet), topically or via injection. Nutritional analyses revealed that both growth inhibition and reduced consumption are a consequence of postingestive malaise rather than a peripherally-mediated antifeedant effect. Cedrelone administered via injection to sixth instar P. saucia larvae also inhibited growth, delayed development, and resulted in considerable larval mortality. However, all larvae which survived treatment pupated successfully. The present study suggests that the toxicity of cedrelone does not likely involve the endocrine system.     

Spatial and temporal patterns of recruitment of the tunicate Ciona intestinalis on a mussel farm in Nova Scotia, Canada

Although possibly indigenous to Nova Scotia, the ascidian Ciona intestinalis has become a problem for local mussel aquaculturists. The local population ecology of the ascidian was studied by recording the depth, distribution, and timing of recruitment of C. intestinalis at four different locations (high wave exposure, low wave exposure, recently fallowed, and historically heavily fouled with tunicates) on a mussel farm at Indian Point, Nova Scotia. Animals were collected weekly from 11 collectors deployed at a depth of 4.5 m over two seasons (June-December 2003 and 2004). Recruitment occurred in two peaks during both seasons: the first peak lasted from late June to late July while the second peak lasted from early September to mid-November. Recruitment was highest in the sheltered and historically fouled location, intermediate in the fallowed site, and lowest in the site with highest wave exposure. Collectors were also deployed at different depths. Recruitment was highest at 4.5 m and to a lesser extent at 8.5 m. Little recruitment was seen at the surface (0.5 m) or in deeper water (12.5 and 16.5 m), except during the second peak in 2004. Overall, these results seem to indicate an abbreviated larval dispersal phase with young recruits settling very close to the pool of adults located on the mussel lines.