Reproduction and life-cycle of the beachflea (<Emphasis Type="Italic">Orchestia gammarellus</Emphasis> (Pallas) (Crustacea: Amphipoda) at thermal and non-thermal sites in the intertidal of Iceland: how important is temperature? |
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Authors: | A Ingólfsson Ó P Ólafsson D Morritt |
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Institution: | (1) Institute of Biology, University of Iceland, Sturlugata 7, 101 Reykjavík, Iceland;(2) School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK |
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Abstract: | The littoral fringe beachflea Orchestia gammarellus (Pallas) is a seasonal breeder over much of its range. Previous studies indicated that temperature was the most important
factor initiating breeding while photoperiod appeared inconsequential. We tested the effect of temperature by comparing two
populations at non-thermal sites with two populations at thermal sites in Iceland. At the non-thermal sites the species is
probably close to its lower temperature tolerance limits, while potentially able to choose optimal temperatures at all times
of the year at the thermal sites. The species was a seasonal breeder at all sites, but the breeding season started 2–3 months
earlier at thermal sites. Breeding ended at about the same time at all sites. We conclude that photoperiod probably governs
breeding season under constant thermal conditions, and this is also supported by observations on laboratory stocks. At the
thermal sites the animals became sexually mature in a year or less, as is the case where the species has been studied at lower
latitudes, while at the non-thermal sites Icelandic animals, apparently uniquely, need 2 years to become sexually mature. |
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