Felicita Scapini

Surface activity, zonation and migrations of Talitrus saltator on a Mediterranean beach

The present study considers a population of Talitrus saltator (Montagu, 1808) living along a Mediterranean beach (Burano, Grosseto, Italy). From April 1986 to March 1987 the annual and daily patterns of amphipod activity were analysed together with zonation and the direction and extent of movements. An annual bimodal activity pattern was established with a first peak of activity in late spring and another one in autumn. Daily activity was predominantly nocturanl with two peaks, one of which could be suppressed or depressed in accordance with particular climatic conditions. The species studied was generally limited to the eu- and supralittoral part of the beach, but the extent of zonation could vary according to climate. Differences between juveniles and adults appeared both for activity patterns and for zonation. Movements were predominantly (ca. 85%) along the sea/land axis with a landward migration always followed by seaward one. Under conditions of high relative humidity and rain, the migrations towards land could extend to the dune. Movements parallel to the shoreline were demonstrated in a separate experiment (in June and October 1987 and June 1988) using the capture-mark-recapture method. The maximum distance covered registered in one night was 200 m.

Comparison of Talitrus saltator (Amphipoda, Talitridae) biology, dynamics, and secondary production in Atlantic (Portugal) and Mediterranean (Italy and Tunisia) populations

Talitrus saltator biology, population dynamics, and reproduction were studied more or less simultaneously at three sand beaches: Lavos, on the western coast of Portugal; Collelungo, on the Italian coast of the Thyrrenian Sea; and Zouara, on the northern coast of Tunisia. The species exhibited a consistent pattern of aggregated distribution. Densities were higher at Lavos than at Collelungo and Zouara. Reproduction took place from early March to late September at Lavos and Collelungo, and from late February to early November at Zouara. The average sex ratio was favourable to males at Lavos and Collelungo, and to females at Zouara. Based on data from Lavos, the population abundance was positively correlated with temperature, while the percentage of juveniles in the population was positively correlated with temperature and sediment moisture. Adult individuals from the Atlantic population were larger than the Mediterranean ones, while newborn individuals from the Mediterranean were slightly larger than Atlantic ones. Life span was estimated at 7-11 months at Lavos, 6-9 months at Collelungo, and 6-8 months at Zouara. Cohorts born at the beginning of the reproductive period tend to have shorter lives than the ones born later in the season, with longer life spans occurring in cohorts that crossed the winter to breed in the next year. The minimum period necessary for sexual differentiation after birth was estimated at ±4 weeks at Lavos, ±3 weeks at Collelungo, and ±4.5 weeks at Zouara, for males, and ±6 weeks at Lavos, and ±5 weeks at Collelungo and Zouara, for females. The period necessary for females sexual maturation after being born was estimated at ±10 weeks at Lavos, and ±8 weeks at Collelungo and Zouara. At the studied sites, T. saltator appeared as semiannual species, with iteroparous females appearing to produce at least two broods per year, and exhibited a bivoltine life cycle. Growth production (P) was estimated at 0.74 g m -2 yr -1 ash-free dry weight (AFDW; 17.7 kJ m -2 yr -1 ) at Lavos, 0.12 gm -2 yr -1 AFDW (2.8 kJ m -2 yr -1 ) at Collelungo, and 0.61 g m -2 yr -1 AFDW (14.3 kJ m -2 yr -1 ) at Zouara. Elimination production (E) was estimated at 1.40 gm -2 yr -1 AFDW (33.5 kJ m -2 yr -1 ) at Lavos, 0.20 g m -2 yr -1 AFDW (4.8 kJ m -2 yr -1 ) at Collelungo, and 1.11 g m -2 yr -1 AFDW (26.6 kJ m -2 yr -1 ) at Zouara. The average annual biomass (B) (standing stock) was estimated at 0.13 g m -2 at Lavos, 0.014 g m -2 at Collelungo, and 0.084 g m -2 at Zouara, resulting in P/B ratios of 5.7 at Lavos, 8.2 at Collelungo, and 7.3 at Zouara, and E/B ratios of 10.8 at Lavos, 14.4 at Collelungo, and 13.1 at Zouara. The present results, combined with information from literature, revealed a geographic variation in T. saltator populations with regard to their morphological characteristics, growth rates, life spans, and life cycles.

Give Beach Ecosystems Their Day in the Sun

The Intergovernmental Panel on Climate Change Fourth Assessment Report ([ 1 ][1]) largely overlooked the impacts of climate change on marine ecosystems ([ 2 ][2]). In their Review (“The impact of climate change on the worlds marine ecosystems,” 18 June, p. [1523][3]), O. Hoegh-Guldberg and J. F

Seasonal variation in the free-running period in two Talitrus saltator populations from Italian beaches differing in morphodynamics and human disturbance

The sandhopper Talitrus saltator Montagu (Amphipoda) is a widespread species adapted to different changing environmental conditions and which typically shows a clear circadian rhythm of locomotor activity. The populations from two beaches on the western Italian coast differing in coastline dynamics (eroded versus dynamically stable) and human disturbance (inside a natural park versus freely used and cleaned for leisure) were studied to highlight intrapopulation variation in the endogenous locomotor rhythm. The activity of adult sandhoppers was studied under constant laboratory conditions within individual recording chambers. Variation of the free-running period was analysed at individual level within each population. Greater variability was found than previously reported for the circadian rhythm period of T. saltator, and seasonal variation was shown for the first time. Differences in the level of variation were correlated with coastline dynamics.

Orientation behaviour and heterozygosity of sandhopper populations in relation to stability of beach environments

Felicita Scapini,’ Marcello Buiatti,’ Elvira De Matthaeis’ and Marco Mattoccia3 ‘Dipartimento di Biologia animale e Genetica, Universitri, via Romana 17, 50125 Firenze, Italy *Dipartimento di Biologia animale e dell’Uomo, Universitti “La Sapienza”, viale dell’Universitci 32, 00185 Roma, Italy 3Dipartimento di Biologia, Tor Vergata, II Universitd di Roma, via 0. Raimondo, 00173 Roma, Italy Key words: Amphipoda; behaviour; orientation; heterozygosity. Introduction The talitrid amphipod Talitrus saltator (Montagu) is a common inhabitant of sandy beaches, where it lives its whole life cycle, avoiding both the arid environment inland and submersion in sea water. Orientation towards the sea is critical for fitness, because good orientation is needed to avoid death by dehydration. During the night sandhoppers from Mediterranean populations migrate inland to feed, during the day they remain burrowed in moist sand at the water’s edge (Scapini et al., 1992). Orientation for zonal recovery occurs mainly by following a sun compass (see Pardi and Ercolini, 1986 for a review). This is of high survival value since these amphipods are not protected against dehydration by morphological structure and the narrow strip of moist sand at water’s edge is subjected to periodic and aperiodic shifting due to tides and storms. It has been shown that the sun compass is genetically determined. Differences among natural populations along the Italian Tyrrhenian and Adriatic shores are related to the orientation of the seashores where they live (Pardi, 1960; Pardi and Scapini, 1983; Scapini et al., 1985; Scapini and Buitatti, 1985; Scapini and Fasinella, 1990). However, the orientation tendency seems to be the result of a non-additive continuous interplay between individual learning and plasticity on one hand, and genetic variation on the population level on the other. It is through both processes that populations adapt to rapid environmental changes (Scapini et al., 1988; Ugolini and Scapini, 1988). Orientation, therefore, being a genetically determined character connected to fitness, for which the relative contributions of genetic and learning components 43

Keynote papers on sandhopper orientation and navigation

This article analyses the relevant studies that have made sandhoppers a model subject for the study of orientation, and traces the development of the paradigm through innovative hypotheses and empirical evidence. Sandhoppers are able to maintain their direction without sensorial contact with the goal, which is their burrowing zone extended along the beach, but very narrow across it. They actively determine the direction of their movements, according to their internal state and the environmental features encountered. Each population shows an ‘innate directional tendency’ adapted to the shoreline of origin, and the inexpert laboratory-born young behave in a similar way to the adults. Genetic differences have been demonstrated between, as well as within natural populations. The question of the calibration of the sun compass to orientation on a particular shoreline implies a redundancy of mechanisms of orientation. Orientation mechanisms may involve environmental cues perceived through diverse sensory modalities, and range from simple orientation reflexes to sun compass navigational systems. These include scototaxis and geotaxis, and the response to the silhouette of the dune, in addition to sun and moon orientation, which is dependent on the time of the day and orientates daily migrations on the beach. Different modalities of orientation may operate singly, or in conjunction with each other, and their ecological significance may vary according to the habitat and lifestyle of the animals. Taken collectively, the orientation behaviour of the group appears to be a most accommodating phenotype, with considerable adaptive potential. The evidence from comparative studies of different populations promotes consideration of behavioural plasticity as an adaptation to changing coastlines.

Orientation in Talitrus saltator (Montagu): trends in intrapopulation variability related to environmental and intrinsic factors

Variability in orientating behaviour of Talitrus saltator (Montagu, 1808) (Amphipoda; Crustacea) was investigated under natural conditions. Two populations were analysed from geomorphologically different Italian shores: a stable beach at Castiglione della Pescaia (Tyrrhenian Sea) and a more dynamic sandy shore intensively eroded by the sea at San Rossore (Ligurian Sea). Orientation was examined repeatedly on single animals on their native beach, releasing them on the sand with all cues available. Tests under controlled conditions were done inland, about 2 km away from the sea, in an experimental arena that permitted only vision of the sky and sun. The effect on orientation of some environmental (sun azimuth and meteorological variables) and intrinsic (sex, size, age and eye left/right asymmetry) factors was studied. Tests were done in spring and autumn, over several days in each season and at different times of the day. Using exploratory analysis and several multiple regression models, sun azimuth, wind direction and eye left/right asymmetry were found to be potential influences on orientation. These processes could explain the variation of orientation within a population that emerged from the choices of animals tested at different times of the day and under different meteorological conditions. The association with environmental variables and intrinsic factors demonstrated that the orientation adopted under natural conditions is dependent on a complex interaction of available cues and also on individual characteristics of the animal.

Metrics to assess ecological condition, change, and impacts in sandy beach ecosystems.

Complexity is increasingly the hallmark in environmental management practices of sandy shorelines. This arises primarily from meeting growing public demands (e.g., real estate, recreation) whilst reconciling economic demands with expectations of coastal users who have modern conservation ethics. Ideally, shoreline management is underpinned by empirical data, but selecting ecologically-meaningful metrics to accurately measure the condition of systems, and the ecological effects of human activities, is a complex task. Here we construct a framework for metric selection, considering six categories of issues that authorities commonly address: erosion; habitat loss; recreation; fishing; pollution (litter and chemical contaminants); and wildlife conservation. Possible metrics were scored in terms of their ability to reflect environmental change, and against criteria that are widely used for judging the performance of ecological indicators (i.e., sensitivity, practicability, costs, and public appeal). From this analysis, four types of broadly applicable metrics that also performed very well against the indicator criteria emerged: 1.) traits of bird populations and assemblages (e.g., abundance, diversity, distributions, habitat use); 2.) breeding/reproductive performance sensu lato (especially relevant for birds and turtles nesting on beaches and in dunes, but equally applicable to invertebrates and plants); 3.) population parameters and distributions of vertebrates associated primarily with dunes and the supralittoral beach zone (traditionally focused on birds and turtles, but expandable to mammals); 4.) compound measurements of the abundance/cover/biomass of biota (plants, invertebrates, vertebrates) at both the population and assemblage level. Local constraints (i.e., the absence of birds in highly degraded urban settings or lack of dunes on bluff-backed beaches) and particular issues may require alternatives. Metrics - if selected and applied correctly - provide empirical evidence of environmental condition and change, but often do not reflect deeper environmental values per se. Yet, values remain poorly articulated for many beach systems; this calls for a comprehensive identification of environmental values and the development of targeted programs to conserve these values on sandy shorelines globally.

Use of multiple regression models in the study of sandhopper orientation under natural conditions

Abstract In sandhoppers (Amphipoda; Talitridae), typical dwellers of the supralittoral zone of sandy beaches, orientation with respect to the sun and landscape vision is adapted to the local direction of the shoreline. Variation of this behavioural adaptation can be related to the characteristics of the beach. Measures of orientation with respect to the shoreline direction can thus be made as a tool to assess beach stability versus changeability, once the sources of variation are correctly interpreted. Orientation of animals can be studied by statistical analysis of directions taken after release in nature. In this paper some new tools for exploring directional data are reviewed, with special emphasis on non-parametric smoothers and regression models. Results from a large study concerning one species of sandhoppers, Talitrus saltator (Montagu), from an exposed sandy beach in northeastern Tunisia are presented. Seasonal differences in orientation behaviour were shown with a higher scatter in autumn with respect to spring. The higher scatter shown in autumn depended both on intrinsic (sex) and external (climatic conditions and landscape visibility) factors and was related to the tendency of this species to migrate towards the dune anticipating winter conditions.

Multiple regression analysis of the sources of variation in orientation of two sympatric sandhoppers, Talitrus saltator and Talorchestia brito, from an exposed Mediterranean beach

Abstract. Two sympatric species from an exposed sandy beach in north-western Tunisia, the sandhoppers Talitrus saltator (Montagu) and Talorchestia brito Stebbing, were compared as regards orientation under natural conditions. Sets of experiments were carried out on the beach using two experimental arenas, one permitting the view of both the sky and landscape and the other of the sky only. Replicates were made at different hours of the day, in different days and period of the year and with various climatic conditions. Multiple regression models were fitted to the angular data obtained. These models allow an estimate of the trends of variation depending on a combination of factors. The simultaneous effects of environmental factors influencing orientation were quantified for each species. The sun was confirmed as the major orientation cue in these populations, but the concentration of directional choices was enhanced by the landscape vision. The climatic factors affected orientation in different ways depending on the time of day and year. When the two species were compared, Talitrus saltator showed a higher flexibility of response than Talorchestia brito under the same environmental conditions, supporting the hypothesis of a higher level of terrestrialization of the former species.