BIOTIC Species Information for Talitrus saltator
|Researched by||Georgina Budd||Data supplied by||MarLIN|
|Refereed by||This information is not refereed.|
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|Typical food types||Partly decayed seaweed and other vegetation.||Habit||Free living|
|Bioturbator||Flexibility||High (>45 degrees)|
|Height||Insufficient information||Growth Rate||1.3-5.5mm/100 days depending on life stage|
|Adult dispersal potential||100-1000m||Dependency||Independent|
|General Biology Additional Information||Growth rate
Williams (1978) reported that juvenile growth rates averaged 5.5 mm in 100 days decreasing to 1.3 mm in 100 days after sexual differentiation at around 8.0 mm.
The leaping habit of the Talitridae is confined to the family and is achieved by the sudden extension of the intucked, short posterior end of the body. In order to achieve a leap, the species has to stand on its legs in a manner not characteristic of the Amphipoda, which normally move on their side. The sudden tail-flick is undirected and it may land anywhere. Hopping is repeated until a safe place is found (Reid, 1947).
Pattern of activity
Despite the widespread occurrence of Talitrus saltator in the supralittoral zone of sandy beaches along the Atlantic coasts of Europe and the Mediterranean (Dahl, 1952), most work concerning the species has focused on its behaviour, in particular influences on the locomotor activity rhythm of the species e.g. Williams (1980, 1979, Williams, J.A., 1983).
During the day, Talitrus saltator is found buried in the substratum above the high tide line but, at night it emerges on the ebb tide to forage intertidally on the strandline algae. It must, however, return to the high supralittoral before the flood tide. Williams, J.A. (1983) found that this activity was under a precise endogenously controlled rhythm, which in constant conditions will free-run for > 100 days without variation.
Following specific light cues at dawn (a threshold light intensity of 1.5 lux, Williams, 1980), nocturnal surface foraging activity ceases and the sand hopper moves upshore in order to locate burrowing sites above the previous high tide level. This dawn upshore migration is also controlled by an endogenous circadian rhythm, probably independent of that controlling emergence and foraging (Hayward, 1994), as following peak nocturnal activity, the sand hopper quite suddenly switches to orientated movement in the direction of light/dark boundaries (horizon). A behaviour that Edwards & Naylor (1987) demonstrated experimentally.
The activity cycle of Talitrus saltator is also entirely circadian. Its nocturnal activity in the intertidal zone occupies a six to eight hour period which, peaks between 0100 and 0300 hours GMT regardless of tidal state and cycles over a period of 24.46 hours. Owing to the requirement for the activity pattern to be phased with the seasonally changing night/day ratio (nL/D) a perceptible daily shift is apparent (Hayward, 1994). Williams (1980) found that the dawn light transition, rather than dusk, was used by Talitrus saltator to synchronize its periods of activity with the nL/D cycle.
The pattern of behaviour seems to serve two purposes. Firstly, it prevents the sand hoppers' burrow zone being completely inundated during the next high tide and consequently a semi-lunar horizontal displacement of the burrow zone occurs (Williams, 1979).
Secondly, the activity is related to humidity. Moisture conservation is a major stress for crustaceans living a transition between marine and terrestrial life-styles and behavioural mechanisms used to locate and maintain humid microhabitats during the diurnal quiescent phase of their circadian activity cycle is vital.
Differences in physical morphology and behaviour are reported (Scapini et al., 1999). For instance, where tides are virtually absent in parts of the Mediterranean, the sand hopper moves landwards beyond high water to forage (Scapini et al., 1992). It navigates back to the supralittoral zone, using celestial orientation, with a circadian timing that is reinforced by visual clues (e.g. Mezzetti & Scapini, 1995; Ugolini & Scapini, 1988).
In conclusion, endogenous behaviour rhythms are especially important in mobile intertidal organisms for the maintenance of a zoned distribution on the shore and for the synchronization of whole population behaviour, vital for reproduction.
|Biology References||Williams, 1979, Dahl, 1946, Dahl, 1952, Hayward, 1994, Williams, J.A., 1983, Williams, 1983b, Williams, 1980, Edwards & Naylor, 1987, Scapini et al., 1999, Mezzetti & Scapini, 1995, Scapini et al., 1992, Ugolini & Scapini, 1988,|