Talitrus Saltator Research Articles

Relationship between heavy metals pollution and genetic diversity in Mediterranean populations of the sandhopper Talitrus saltator (Montagu) (Crustacea, Amphipoda)

Trace metals are one of the groups of pollutants that reduce genetic variability in natural populations, causing the phenomenon known as “genetic erosion”. In this study we evaluate the relationship between trace metals contamination (Hg, Cd and Cu) and genetic variability, assessed using fluorescent Inter-Simple Sequence Repeats (fISSRs). We used eight populations of a well-established biomonitor of trace metals on sandy beaches: the amphipod Talitrus saltator. The trace metals analysis confirmed the ability of sandhoppers to accumulate Hg, Cd and Cu. Moreover, populations from sites with high Hg availability had the lowest values of genetic diversity. Our results validate the use of fISSR markers in genetic studies in sandhoppers and support the “genetic erosion” hypothesis by showing the negative influence of Hg contamination on sandhopper genetic diversity. Therefore, genetic variability assessed with fISSR markers could be successfully employed as a biomarker of Hg exposure.

Niche segregation in sandy beach animals: an analysis with surface-active peracarid crustaceans on the Atlantic coast of Spain

Several species of sandy beach invertebrates regularly switch between burial in the sand during the day and surface activity at night to feed on stranded organic matter. Because all species consume essentially the same type of food (i.e., wrack) deposited over a restricted area, the potential for competition exists. Conversely, spatial and temporal segregation of surface activity behaviour is predicted to allow for niche separation. Here, we tested whether such behavioural niche separation occurs in three species of sympatric crustaceans (the talitrid amphipods Talitrus saltator (Montagu 1808) and Talorchestia brito Stebbing 1891, and the oniscoidean isopod Tylos europaeus Arcangeli 1938). We also assessed whether surface activity is modulated by weather, sea conditions and moon phases. Surface activity was measured over three consecutive moon phases on an exposed beach on the Atlantic Coast of Spain using pitfall traps along three transects from the foredunes to the swash. Adults of the amphipod T. saltator and the isopod T. europaeus overlapped spatially and temporally in their surface activity for most of the night. By contrast, the activity of T. brito was strongly disjunct in time and concentrated into significantly shorter bouts around dawn or dusk. Niche differentiation was also evident along the space axis, where T. brito occurred distinctly lower on the beach. Although several environmental factors (e.g., air and sand temperature, humidity, atmospheric pressure, wind speed and wind direction) were correlated with surface activity, this was highly variable amongst species, life stages, and synodic phases, and did not obscure the fundamental mosaic of spatio-temporal heterogeneity amongst species. Nocturnal feeding on beach wrack creates the potential for competition amongst sympatric crustaceans which can, however, be mitigated by behaviour patterns that separate consumers in time and space.

The trophic significance of the invasive seaweed Sargassum muticum in sandy beaches

Native and exotic seaweeds frequently lie on the beach and sustain part of the benthic food web. However, the role of exotic seaweeds as food sources for beach consumers has been poorly studied. We studied the temporal and spatial variability in the trophic significance of the invasive brown seaweed Sargassum muticum on sandy beaches. We measured the stable isotopes ( δ 13C and δ 15N) in the tissues of S. muticum and of invertebrate consumers and estimated the dietary biomass proportion of S. muticum during four sampling dates at two beaches and heights on the shore. Samples were collected from eight pitfall traps placed at a distance of 2 m from each other. Detrital macroalgae and seagrasses were also collected by hand within an area of 30 cm around each pitfall trap. We measured the spatial and temporal variability in the isotope composition of the beach consumers and of S. muticum using different models of analyses of variance. We then calculated the biomass proportion of S. muticum to the animal diet with a two-isotopic mixing model. The invasive alga S. muticum seemed to be one of the main food sources for the amphipod Talitrus saltator and, to a less extent, for the isopod Tylos europaeus. The importance of S. muticum was however temporally variable and decreased during spring (in March and May), probably due to the availability of native macrophytes. The supply of invasive wrack to beach food webs thus deserves more attention if we want to understand their role in influencing food web dynamics.

Intraspecific diet shift in Talitrus saltator inhabiting exposed sandy beaches

Talitrid amphipods are the most abundant herbivores on exposed sandy beaches. Despite their important role as trophic intermediates between macrophytes and higher levels (i.e. insect and bird) of beach food webs, very little information is available on their feeding patterns. The main aim of this study was to investigate intraspecific differences in the feeding behaviour of Talitrus saltator. We tested the hypotheses that: (1) adult females and males showed different isotope signatures and therefore relied on different sources of food; and (2) patterns of variation of isotope signatures of juveniles differed from those of adult specimens, evidencing a diet shift during the development. We used stable isotope signatures and tested for differences upon the level on the shore, times of the year and beaches experiencing similar morpho-dynamic and environmental conditions. Finally, we investigated the trophic significance of macrophyte detritus in the diet of males, females and juveniles. Results showed that adult males had a more variable diet than females and juveniles (inferred from δ 13C and δ 15N values). Dual-isotope graphs suggested that Sargassum muticum and Cystoseira baccata wrack could be among the main food sources for both juvenile and adult stage.

Seawater Ca2+ concentration influences solar orientation inTalitrus saltator(Crustacea, Amphipoda)

The role of salinity in the ecophysiology of many intertidal invertebrates has been extensively investigated. Calcium (Ca(2+)), magnesium (Mg(2+)), potassium (K(+)) and sodium (Na(+)) are the major constituents of seawater and it has been demonstrated that sandhoppers tested under the sun in diluted seawater (3.5 per thousand) head seaward, instead of going landward as expected. Therefore, the variation in seawater salinity (from 35 per thousand to 3.5 per thousand) influences their directional choice. This paper investigates the contribution of different cations to the sea-land directional choice of Talitrus saltator (Crustacea, Amphipoda) by the sun compass orientation mechanism. Results of releases carried out in basic seawater selectively deprived of Ca(2+), Mg(2+) or K(+) and containing the same concentration of Na(+) indicate that only the reduction in Ca(2+) concentration affects the capacity of solar orientation. The pH does not influence the directional choice of sandhoppers and nor do small variations in salinity in the range 32-39 per thousand. Moreover, the clear photopositive tendency registered in experiments of phototaxis in Ca(2+)-deprived seawater indicates that the absence of Ca(2+) does not affect the normal functioning of the visual cells. Therefore, our results show that Ca(2+) seawater concentration is important for the correct functioning of one of the principal mechanisms of orientation in supralittoral amphipods and it could affect their survival in the field.

Impact of Environmental Factors on Zonation, Abundance, and Other Biological Parameters of Two Tunisian Populations of Talitrus Saltator (Amphipoda, Talitridae)

Impact of Environmental Factors on Zonation, Abundance, and Other Biological Parameters of Two Tunisian Populations of Talitrus Saltator (Amphipoda, Talitridae)

Sandhopper solar orientation as a behavioural biomarker of trace metals contamination

Although many studies have focused on trace metals accumulation, investigations of talitrid amphipods as biomarkers are rare. This study explores the possibility of using the solar orientation capacity of Talitrus saltator as a behavioural marker of exposure to two essential (Cu and Zn) and two non-essential (Cd and Hg) metals. LC 50 analyses performed before the solar orientation tests showed that the 72 h LC 50 for Hg was 0.02 ppm while the 96 h LC 50 values for Cu, Cd and Zn were 13.28 ppm, 27.66 ppm, and 62.74 ppm, respectively. The presence of metals in seawater affects the solar orientation capacity of T. saltator in a concentration-dependent manner and according to the toxicity ranking of the metals (Hg > Cu > Cd > Zn). Therefore, the solar orientation capacity of T. saltator seems to be a promising behavioural marker for exposure to trace metals.

Difference in skylight intensity is a new celestial cue for sandhopper orientation (Amphipoda, Talitridae)

We investigated the use of the skylight intensity gradient as a new celestial compass cue in sandhoppers (Talitrus saltator). Experiments were conducted at different latitudes (temperate and equatorial) with different zenithal distances of the sun under a translucent (opaline) Plexiglas dome. We also used a blue filter placed on the translucent dome to remove the spectral sky gradient, and a screen for the sun to remove the skylight intensity gradient. Therefore, in our experimental conditions, the spectral gradient and skylight polarization were impossible to use as directional information. Sandhoppers used the difference in skylight intensity in their directional choice when zenithal distance was greater than 10°. Therefore, the anisotropic radiance distribution (i.e. the difference in skylight intensity between the hemidome containing the sun and the opposite one) is a real celestial factor in animal spatial orientation. However, it is probably more imprecise than the solar orientation and could not be used by all animals.

The sandhopper Talitrus saltator (Crustacea: Amphipoda) as a biomonitor of trace metal bioavailabilities in European coastal waters

The amphipod crustacean Talitrus saltator is an established, easily accessible, biomonitor of trace metal bioavailabilities in coastal waters. We have carried out a geographically widespread collection of T. saltator from European shores, stretching from the north-west Atlantic through the Baltic to the Mediterranean. A primary aim of the work was to establish a database of accumulated trace metal concentrations (Cd, Cr, Cu, Fe, Mn and Zn) in this biomonitor. Statistical analysis has shown significant geographical differences in the bioavailabilities of all the metals, the most distinct being copper, iron and manganese. It has proved possible to identify unusually high accumulated concentrations of Cd, Cr, Cu, Fe, Mn and Zn in this biomonitor, indicative of high metal bioavailability at a particular site. These may serve as reference points for future biomonitoring programmes seeking to identify metal contamination in coastal waters.

On the role of Posidonia oceanica beach wrack for macroinvertebrates of a Tyrrhenian sandy shore

The use of Posidonia oceanica beach wrack by macroinvertebrates of the sandy beach at Burano (Tuscany, Italy) was assessed by following the colonisation dynamics of the wrack and analysing the stable isotopes ‘scenario’ of the main local carbon and nitrogen sources and consumers. One-hundred experimental cylinders, filled with P. oceanica wrack, were placed on the beach and sampled over a 1-month period. Abundance and species richness of macroinvertebrates in wracks varied through time. Wrack was colonised by crustaceans almost immediately after deployment of the experimental cylinders. The amphipod Talitrus saltator largely dominated the faunal assembly and, together with the isopod Tylos europaeus, occupied the wracks closer to the sealine. These were followed by dipterans, staphylinids, pselaphids and tenebrionids that occurred in drier wracks higher up on the eulittoral. Moisture content of the wrack and sand decreased through space and time. This was the primary factor explaining the spatial and temporal changes observed in macroinvertebrate abundance, with species colonising or abandoning wracks according to thresholds of environmental parameters. Isotopic analysis clearly established the absence of any direct dietary link between P. oceanica wrack and macroinvertebrates. Terrestrial food sources were also discarded. Both our experimental data and a literature search showed that the organic matter from seston as filtered by the sand is the most plausible carbon and nitrogen source for beach food webs. Even if P. oceanica wrack is not a trophic source for macroinvertebrates, it is vitally important as a physical structure that provides detritivorous and predatory species with refuge from environmentally stressful conditions.

The sandy beach macrofauna of Gulf of Gabès (Tunisia)

AbstractThis study describes the macrofauna of the three beaches situated in central Gulf of Gabès (Tunisia): Ouderef, Gabès and Zarrat. The Gulf of Gabès has the largest tides in the Mediterranean and the beaches showed a wide intertidal zone. The beaches were sampled once during the spring low tides of June 2005. A transect was extended at each beach, from above the drift line to below the swash line at five sampled levels; at each level six 0.05 m2 replicates were taken to a depth of 30 cm and sieved through a 1‐mm mesh, and the organisms collected and preserved. The three beaches showed a different physical environment. Sediment type was medium sand at the steeper Ouderef beach, fine sands at Gàbes beach, and very fine sands at the flatter Zarrat beach. The total number of species collected was 31: 12 crustaceans, 10 polychaetes, four molluscs and five insects. The supralittoral and mediolittoral zones were very different. The supralittoral zone was dominated by Talitrus saltator and insects. The most abundant mediolittoral species were the amphipod crustacean Bathyporeia guilliamsoniana at Ouderef beach (23069 ind.m−1), the surf clam Donax trunculus at Gabès beach (60711 ind.m−1) and the spionid polychaete Scolelepis mesnili at Zarrat beach (18345.6 ind.m−1).

The Belgian sandy beach ecosystem: a review

AbstractThis paper reviews the available knowledge on sedimentology, hydrodynamics and five major ecosystem components (microphytobenthos, vascular plants, terrestrial arthropods, zoobenthos, and avifauna) of Belgian sandy beaches. It covers the area from the foredunes to the lower foreshore, takes an ecosystem approach to beaches of this specific geographic area. Morphodynamically, Belgian beaches are (ultra‐)dissipative, macrotidal, and wide. Characteristic grain sizes are 160–380 μm. The sand becomes coarser, beach slopes steeper and tidal range smaller towards the south‐west, where beaches have also been frequently reshaped by human interference such as nourishment. Beach organisms are highly adapted to this unique environment and can reach high numbers. We show that even on a heavily populated coastline subjected to intense recreational and development pressure, beaches provide critical, yet threatened, habitats. Vascular plants growing near the drift line, on the dry beach and in the embryonic dunes are mostly short‐lived and thalassochorous; the most common species include sea rocket (Cakile maritima), prickly saltwort (Salsola kali subsp. kali), and sea sandwort (Honckenya peploides). These zones are habitat to a highly diverse suite of terrestrial arthropods of halobiontic, halophilous and haloxene species; prominent members are sandhoppers (Talitrus saltator) and dipterans (flies). Microphytobenthos, mainly diatoms, is an important primary producer on Belgian beaches but is not well known. The meio‐ and macrobenthos of Belgian beaches contains specific assemblages such as the Scolelepis squamata–Eurydice pulchra community of the upper intertidal zone. Birds no longer nest on the beaches itself, but Belgian sandy shores continue to function as important resting and foraging areas for birds such as the sanderling Calidris alba. We identify several human pressures on the beach ecosystems arising from recreation, beach management and fisheries.

The effect of human use of sandy beaches on developmental stability ofTalitrus saltator(Montagu, 1808) (Crustacea, Amphipoda). A study on fluctuating asymmetry

AbstractIn recent years, there has been an increasing intensity of human use of coastal areas in Galicia (NW Spain). Actually, there is great concern about rapid and unplanned urban and industrial development on certain locations, as this can generate adverse impacts on those areas. In this study, we selected three sandy beaches along the Galician coast (Chanteiro, Insuela and Valieros) facing different levels of anthropic pressure, and we analysedTalitrus saltatorindividuals with the aim of elucidating whether anthropogenic pressures on beaches such as tourism or pollution have an influence on the incidence of morphological developmental alterations in sandhoppers in the field. Specifically, levels of fluctuating asymmetry were selected as indicators of environmental stress. Results of two sampling dates (May and September) show that individuals collected at the most touristy and polluted beach were those showing the highest asymmetry values, although results were only statistically significant for samples collected during spring. Results are in accordance with the hypothesis that beach management and pollution reduce symmetry in sandhoppers living in altered beaches.

Responses of talitrid amphipods to a gradient of recreational pressure caused by beach urbanization

AbstractDemands for public outdoor recreation and urbanization are a potential source of environmental disturbances, particularly on sandy beaches. These habitats have therefore experienced rapid degradation worldwide. Talitrid amphipods, which are common inhabitants of sandy beaches, are probably good indicators of such disturbances. In this study, we evaluated the responses of the two amphipods Talitrus saltator and Atlantorchestoidea brasiliensis to human pressure on Spanish and a Brazilian beach, hypothesizing that disregarding species differences, their population sizes will decline under urbanized conditions. The Barra da Tijuca (Brazil) and Levante (Spain) beaches have mixed landscapes with varying levels of development, and each has a protected area (MPA) adjacent to urbanized sites. Numbers of talitrids as well as visitors were compared among sites on each beach. Talitrids were most abundant at the protected sites. This was true of both beaches, even though temporal patterns of human activity were quite different, with Levante experiencing sharp declines in the number of visitors during its harsh winter. Urbanized sites did not experience high Talitrid densities even during a period of low human pressure. On this basis, T. saltator and A. brasiliensis were considered good indicators of urbanization and recreational activities on sandy beaches. MPAs were found to be very important for the successful conservation of the talitrid populations. A feasible method of managing human pressure and thereby conserving beach biodiversity therefore seems to be the establishment of beach MPAs.

Orientation of littoral amphipods in two sandy beaches of Brittany (France) with wide tidal excursions

Sandhoppers orient towards the shoreline using a sun compass when they are subject to dry conditions. In this study we analysed the orientation of populations from two sandy beaches with wide tidal excursions (Brittany, France): at Damgan (sea to the South) and at Le Verger (sea to the North). At Le Verger beach Talitrus saltator was found together with Deshayesorchestia deshayesii (former Talorchestia deshayesii). The results of the experiments on sun and landscape orientation showed that the Damgan T. saltator oriented better with ebbing tides than with rising tides, while the Le Verger T. saltator showed the opposite trend as a response to tides. This is probably related to the differing risk of being swept away by tides at the two localities. D. deshayesii was found to be more scattered in orientation than T. saltator, probably because it is a recent colonizer of that beach.

Effects of beach nourishment and groynes building on population and community descriptors of mobile arthropodofauna

Abstract For decades beach nourishment and groyne building have been used to combat sandy beach erosion, but their effects on sandy beach macrofauna are often neglected. Here, we analysed the effects of beach nourishment and groyne building on a sandy beach within the San Rossore-Migliarino-Massaciuccoli Regional Park (a natural park in Tuscany, Italy) on two different levels of organization: the abundance of the crustacean amphipod Talitrus saltator (population level) and community descriptors of the sandy beach arthropod fauna (community level), with emphasis on supralittoral species. Samples were taken bimonthly from September 2004 to January 2006 using pitfall traps. T. saltator abundance was described by generalized linear models (GLMs) and arthropodofauna community descriptors were estimated by species number, diversity indexes and ordered with multivariate ordination methods. The abundance of T. saltator in different seasons was influenced by the month of sampling during the autumn–winter season and by beach width, substrate penetrability and the “species number” biotic factor during the spring–summer season. The abundance models revealed no direct effects of beach nourishment. T. saltator was shown to be both a typifying and discriminating species, confirming its key role in the community of sandy beaches. The arthropodofauna community showed sensitivity to the substrate grain size and quality changes generated by beach nourishment, as the community composition changed at the nourished sites in line with seasonal dynamics. Human actions to stabilise the shoreline therefore emerged as a driving environmental feature, altering the beach's physical characteristics and consequently its fauna on different organizational levels: it was shown to have a direct effect on the arthropodofauna community structure and on sandhopper population abundance by determining habitat availability.

Lunar orientation in sandhoppers is affected by shifting both the moon phase and the daily clock

The use of a moon compass in the sandhopper, Talitrus saltator, is well known, but the mechanism that allows compensation for the changes in moon position during single nights and from night to night is still poorly understood. In a moon phase shift experiment, we exposed sandhoppers to a dim nocturnal light simulating the moon. The false moon was kept in phase with the true moon for controls and gradually shifted for experimental animals so that, at the time of the test, the false moon calendar was set up to coincide with the first quarter for one experimental group and with the last quarter for the other. During the test under the full moon, the experimental groups behaved as expected on the basis of the moon phase shift, whereas controls showed an intermediate orientation. In a daily clock shift experiment, the sandhoppers were subjected to an artificial light:dark treatment, which was coincident with the natural 24 h light:dark cycle for controls, but was slow or fast shifted by 3 h for the experimental groups. When tested under the full moon, the slow- and fast-shifted experimental groups oriented in a direction that was appropriate to the position of the moon some hours later and before the test, respectively. We conclude that the sun and moon compasses are not ruled by independent rhythms and propose that three interacting rhythms (a circadian, a circalunidian and a circalunar one) are involved in the functioning of the moon compass.

Processing of allochthonous macrophyte subsidies by sandy beach consumers: estimates of feeding rates and impacts on food resources

Allochthonous subsidies of organic material can profoundly influence population and community structure; however, the role of consumers in the processing of these inputs is less understood but may be closely linked to community and ecosystem function. Inputs of drift macrophytes subsidize sandy beach communities and food webs in many regions. We estimated feeding rates of dominant sandy beach consumers, the talitrid amphipods (Megalorchestia corniculata, in southern California, USA, and Talitrus saltator, in southern Galicia, Spain), and their impacts on drift macrophyte subsidies in field and laboratory experiments. Feeding rate varied with macrophyte type and, for T. saltator, air temperature. Size-specific feeding rates of talitrid amphipods were greatest on brown macroalgae (Macrocystis, Egregia, Saccorhiza and Fucus). Rates for large individuals of both species ranged from ∼40 mg wet wt individual−112 h−1 on brown macroalgae to negligible feeding by M. corniculata on a vascular plant (surfgrass). Amphipod growth rates were also greatest on Macrocystis and lowest on surfgrass, Phyllospadix. For a Californian beach with substantial inputs of macrophyte wrack (>70 kg wet wt m−1 month−1 in summer), we estimated that the population of talitrid amphipods could process an average of 55% of the palatable Macrocystis input. Our results indicate that talitrid amphipod populations can have a significant impact on drift macrophyte processing and fate and that the quantity and composition of drift macrophytes could, in turn, limit populations of beach consumers.

The amphipod Talitrus saltator as a bioindicator of human trampling on sandy beaches

The present paper assesses the use of the supralittoral amphipod Talitrus saltator as a bioindicator of the effects of human trampling on the supralittoral sandy band. Samplings in delimited areas were carried out at sites subjected to different human impact. The results showed a strong negative correlation between the number of swimmers and the sandhopper population density, while there was no clear relationship between sandhopper abundance and the other factors considered: granulometry, compactness and organic carbon content of the sand, and trace metal contents in the sand and sandhoppers. A field test of trampling conducted in a confined space showed its direct negative effect on sandhopper survival. However, trace metal analysis confirmed the ability of T. saltator to bioaccumulate some elements (Hg, Zn, Cu, Cd). Our study demonstrates that T. saltator is a good bioindicator of human impact in the supralittoral zone of sandy shores.

Variation of the Locomotor Activity Rhythms in Three Species of Talitrid Amphipods, Talitrus saltator, Orchestia montagui, and O. gammarellus, from Various Habitats

The expression of biological rhythms was investigated in five populations of three different species of talitrid amphipods from various habitats in the Maremma Regional Park, Grosseto, Italy: Talitrus saltator (from a sandy beach and a canal), Orchestia montagui (form a Posidonia banquette), and O. gammarellus (from a cave entrance and a river bank). Locomotor activity rhythms were recorded in individual animals over 21 days in constant dark at a temperature of 18°±1°C. A high variability in rhythm expression was evident, not only among species and populations but also within populations and the activity pattern of individuals. Activity rhythms of T. saltator and O. montagui were similar, with a good definition and precise circadian periodicity, whereas O. gammarellus showed a high variability and low definition of the circadian rhythm. Significant differences were also observed between two populations of O. gammarellus and T. saltator from different habitats. Within the O. gammarellus species, a significantly higher percentage of active animals (p<0.001) was observed in the cave than the river‐bank population; within T. saltator, a significantly lower percentage of active animals (p<0.01) and higher percentage of periodic animals (p<0.05) was found in the canal than the sandy beach population. With reference to environmental stability and variability, the differences observed are explained as a need for plasticity to adapt to environmental changes.