Landscape vision and zonal orientation in the Equatorial sandhopper Talorchestia martensii

Abstract

We investigate the role of the landscape in the zonal recovery of the Equatorial sandhopper Talorchestia martensii Weber. It is known that this species uses the sun and the magnetic compasses to return to the belt of damp sand of the beach following the shortest route (the sea-land axis). However, the sun is not always easy to use at Equatorial latitudes because of astronomical reasons (its zenithal culmination and its hourly azimuthal speed) at least during the central time of the day (around noon) and close to the equinox. Our experiments were performed in Kenya, during the equinoctial period. We tested adult individuals, belonging to Malindi (Kenya) population, in a confined environment with and without the vision of the landscape of their home beach and with the vision of the prominent landscape of a different-orientated shore (Temple Point). Releases were carried out with either natural or zeroed magnetic field. Results clearly show the importance of the landscape as an orienting factor mainly during the central hours of the day when it seems to assume a greater importance than magnetic cues.

Sky radiance and spectral gradient are orienting cues for the sandhopperTalitrus saltator(Crustacea, Amphipoda)

“…It is important to note that the spectral gradient was the only available cue in the experiments where the simulated sun was switched off. Thus, the reduction of the number of radially orientated individuals could be caused by the absence of any further reliable cues, such as the substrate slope and the surrounding landscape (Ercolini and Scapini, 1974;Craig, 1973;Hartwick, 1976;Ugolini et al, 1986Ugolini et al, , 2006Ugolini, 2014;Ugolini and Ciofini, 2016). It remains an open question why the sandhoppers exhibited a relatively low number of radially oriented individuals (50%) registered from the morning releases with the artificial sun switched on (Fig.…”

“…However, the sun and moon are not the only celestial cues used by this species. Beside astronomical cues, sandhoppers can use local cues, such as the slope of the substratum and the vision of the landscape as references to return to their belt of damp sand (Ercolini and Scapini, 1974;Craig, 1973;Hartwick, 1976;Ugolini et al, 1986Ugolini et al, , 2006Ugolini, 2014;Ugolini and Ciofini, 2016). In addition to the sun, sunlight scattering on atmospheric particles generates additional skylight cues, such as a polarization pattern as well as profiles of radiance and spectral distributions (e.g.…”

Strengthening marine amphipod DNA barcode libraries for environmental monitoring

“…The barcoded Talorchestia martensii (Weber, 1892) in this study is generally referred to as equatorial sandhoppers occurring in African beach sand (Ugolini, 2016) and Kenyan coast (Ugolini and Ciofini, 2015). T. martensii was widely used astronomical orientations researches (Ugolini and Ciofini, 2015;Ugolini, 2016). Victoriopisa chilkensis (Chilton, 1921) barcoded in the present study was known to occur on Malaysian coast (South China Sea) and…”

The Drivers of Heuristic Optimization in Insect Object Manufacture and Use

“…Invertebrate prey-capture traps come in two broad categories of design, pitfall traps or a web-based trap ( Hansell, 2007 ; Scharf et al, 2011 ). Trap building involves structural considerations, for instance spider-webs need to be robust to environmental damage ( Cranford et al, 2012 ; Sensenig et al, 2012 ; Qin et al, 2015 ), and functionally, these constructed objects may be used for other purposes such as mating rituals ( Vibert et al, 2016 ). Their primary purpose, however, is food acquisition.…”