Talitrus Saltator Research Articles

The relationship between antennal segment number and moulting in Talitrus saltator (Montagu, 1808) (amphipoda, talitridae) : Williams, J.A., 1987. Crustaceana, 53(3):243–252. Dept. of Oceanogr., The Univ., Southampton S09 5NH, UK

The relationship between antennal segment number and moulting in Talitrus saltator (Montagu, 1808) (amphipoda, talitridae) : Williams, J.A., 1987. Crustaceana, 53(3):243–252. Dept. of Oceanogr., The Univ., Southampton S09 5NH, UK

Evaporative water loss under desiccation stress in semiterrestrial and terrestrial amphipods (Crustacea: Amphipoda: Talitridae)

Transpiration rates were measured in both still and moving air systems in three talitrid amphipods, Orchestia gammarellus (Pallas), Talitrus saltator (Montagu), and Arcitalitrus dorrieni (Hunt). Significant differences were demonstrated between the rates of water loss in the three species. The terrestrial A. dorrieni exhibited much higher rates than the supralittoral species. In still air at 15 °C and 75% r.h., for example, the mean rate in A. dorrieni was 0.183 ± 0.008 mg· h −1· mg wet wt −1 compared with 0.111 ± 0.003 for Orchestia gammarellus and 0.106 ± 0.003 for Talitrus saltator. In moving air, regression lines plotting weight-specific rates of water loss against saturation deficit were significantly different between the three species in their slope. The regression line for Arcitalitrus dorrieni ( R= - 0.0514 + 0.0481 φ) was much steeper than that for Orchestia gammarellus ( R = 0.0465 + 0.0187 φ) and for Talitrus saltator ( R = 0.033 + 0.0128 φ). Arcitalitrus dorrieni therefore showed the highest rates ofwater loss, under conditions of high desiccation stress, but there was no clear difference between the species at low values of saturation deficit. Mean calculated permeabilities reflect this trend: A. dorrieni, 0.0403 ± 0.0009 mg · h −1· mg wet wt −1 · mm Hg −1, Orchestia gammarellus, 0.0247 ± 0.0008, and Talitrus saltator, 0.0188 − 0.0006. Juvenile supralittoral talitrids of approximately the same body size as Arcitalitrus dorrieni consistently showed higher weight-specific rates of water loss in still air than adults of their own species, but the rates were usually lower than those of adult A. dorrieni. The very high rates of transpiration in A. dorrieni are not explicable by purely allometric considerations. The results are discussed with reference to the ecology and natural habitats of the species investigated and in relation to the colonization of the terrestrial habitat.

Copper and zinc in an ecological series of talitroidean Amphipoda (Crustacea).

Cu and Zn concentrations were determined for the following talitroidean amphipods, Hyale nilssoni (Rathke), Talitrus saltator (Montagu), Talorchestia deshayesii (Audouin), Orchestia mediterranea Costa, O. gammarellus (Pallas), O cavimana Heller and Arcitalitrus dorrieni (Hunt) in September 1986 from sites in W. Britain (mostly Scottish). To minimize size effects, only animals >2mg body dry weight were included in analyses. Only Talorchestia (Cu & Zn) and O. cavimana (Zn) showed any residual relationship between metal concentration and dry weight. Log transformed data for concentrations of each metal against log dry wt. in all species were compared by ANCOVA. Copper and zinc concentrations of males and females were not significantly different in O. gammarellus, O. mediterranea and T. deshayesii, though Cu (but not Zn) concentrations differed with sex in O. cavimana. The order of species when ranked according to an ascending series of Cu concentrations (at standard body weight) reflected their ecological zonation from sea to land closely, with species living proximal to the sea having lowest Cu concentrations. The 6 talitrid species all had similar Zn concentrations but the Zn concentration of H. nilssoni was considerably lower. There was a relationship between Cu and Zn concentrations in individuals of only one species (O. gammarellus). Data on Cu and Zn concentrations for O. gammarellus derived from the same site in September 1983 were almost exctly the same as in September 1986. The possible impact of seasonal variation on haemocyanin levels is discussed.

Endogenous circadian changes in orientational behaviour of Talitrus saltator: Edwards, J.M. and E. Naylor, 1987. J. mar. biol. Ass. U.K., 67(1):17–26. Mar. Sci. Lab., Univ. College of North Wales, Bangor, Gwynedd LL57 2UW, UK

Endogenous circadian changes in orientational behaviour of Talitrus saltator: Edwards, J.M. and E. Naylor, 1987. J. mar. biol. Ass. U.K., 67(1):17–26. Mar. Sci. Lab., Univ. College of North Wales, Bangor, Gwynedd LL57 2UW, UK

A case for hormonal modulation of locomotor rhythmicity in Talitrus saltator (Crustacea: Amphipoda)

1. 1. In order to establish hormonal regulation of the circadian locomotor rhythm of Talitrus saltator, the influence of Carcinus eyestalk extract, the site of the crustacean neural depressing hormone (NDH), on the activity pattern of Talitrus was examined. 2. 2. A reduction in the absolute activity level of Talitrus was consistently observed for at least one circadian cycle after injection of treated eyestalk tissue extract. 3. 3. A linear dose-response relationship exists between the concentrations of NDH-containing fractions injected, monitored as total protein content, and the reduction in locomotor activity elicited. 4. 4. The cross-sensitivity to Carcinus NDH apparent in Talitrus suggests that the same/similar hormonal agents are utilized to modulate the overt locomotor activity rhythms of both species.

Genetic differentiation between populations of Talitrus saltator and Talorchestia deshayesii (Crustacea: Amphipoda) from coastal areas of the north-western European continent

Electrophoretic studies of gene-enzyme variation in the littoral talitrids Talitrus saltator (Montagu) and Talorchestia deshayesii (Audouin) were undertaken to estimate the amount of divergence among geographically separated populations. Samples of both species were taken from sandy beaches over a transect of approximately 3 500 km along the coast of the European continent including Baltic, North Sea and Atlantic locations. A total of 22 T. saltator and 15 T. deshayesii populations were analysed for genetic variation at various enzyme loci. Both amphipods revealed relatively low levels of polymorphism and heterozygosity. Among the loci studied, phosphoglucose isomerase (Pgi) and phosphoglucomutase (Pgm) were highly polymorphic. Patterns of micro- and macrogeographic variation in terms of distributions of allele frequencies at these particular loci are compared. Interpopulation allozymic variation was shown to be lower in T. deshayesii than in T. saltator. As demonstrated by T. saltator populations sampled in coastal sites ranging from Denmark to western France, clinal variation in frequencies of two alleles became evident at the PGI locus, exhibiting a steady increase in the level of polymorphism with decreasing latitudes. It is argued that limited gene flow and, to some extent, random genetic drift may account for the gene pool structure of the talitrid species investigated.

Interaction between solar orientation and landscape visibility in Talitrus saltator (Crustacea: Amphipoda)

A series of experiments on the littoral amphipod Talitrus saltator (Montagu) was carried out between April and September, 1978–1981, both under natural conditions and inland with artificial landscapes of different heights on the horizon, in order to assess the visual importance of the landscape in zonal orientation in populations from the Mediterranean coast, and to determine interactions between solar orientation and orientation based on the landscape. Inland, orientation in controls (permitting only vision of the sky and the sun) was compared to that of the experimental individuals, who could see a simulated landscape positioned landwards to them and seawards. In nature, sandhoppers released in a level arena with the landscape screened from view were compared with others released in an unscreened arena and on the sand in absolutely natural conditions. Situations where solar orientation contradicted local cues were produced both by releasing the sandhoppers on a shore diversely orientated to their own, and by shifting their internal clock by nine hours. Results show that T. saltator uses the landscape as a cue in its orientation towards the sea, in conjunction with solar orientation: the latter being the principal factor involved even when the sandhoppers are separated from the “local optical factor” in the sky (in trials at a distance from the sea). In fact, with the artificial landscape set seawards, none of the populations we studied showed any orientation based on the landscape comparable in accuracy to orientation based exclusively on the sun. From the experiments carried out in natural conditions, it is possible to deduce that conflicting conditions gave rise to two types of results: deviation from the mean direction and an increase in dispersion, up to total dispersion when the local factors were in total contrast to solar orientation (clock-shifted sandhoppers released on the sand).

The rôle of photoperiod in the initiation of breeding and brood development in the amphipod Talitrus saltator Montagu

The supralittoral amphipod Talitrus saltator Montagu has a discrete breeding period between late May and August. Individuals were maintained at five experimental photoperiods of constant dark, LD 12:12, LD 14:10, LD 16:8, and LD 18:6 at ambient temperature for 225 days between March and October. During this time the onset of reproductive activity and aspects of brood development were monitored. Data provide evidence of a “critical daylength” influencing reproduction. Photoperiods in excess of LD 14:10 were necessary to induce reproductive behaviour comparable to that of a field population. At these photoperiods reproductive activity was sustained over a longer period than observed in natural populations. Amphipods were also held in LD 16:8 and constant dark for 163 days between October and March, at ambient temperature. After an 80 to 100-day period, resting stage females exhibited “normal” reproductive activity. Photoperiod is suggested to have a direct effect on the onset of reproductive activity and probably on the duration of activity in Talitrus. Temperature appears to have a limited influence on the onset of reproduction.

Free-Running, Endogenous Semilunar Rhythmicity in a Marine Isopod Crustacean

In recent years several workers have postulated the occurrence in a number of coastal animals of endogenous behaviour and physiological rhythms of semilunar periodicity (see Naylor, 1982). However, only a few of these long term rhythms have been demonstrated as free-running cyclical behaviour over long periods of time in constant conditions. For example, the supra-littoral amphipod Talitrus saltator (Montagu) has been shown to express semilunar variations in daily locomotor activity over three cycles of neap/spring tides during 46 days in constant conditions in the laboratory (Williams, 1979). In contrast, in the mid-shore sand-beach isopod E. pulchra (Leach) semilunar variations in swimming behaviour (Fish & Fish, 1972; Alheit & Naylor, 1976) and of respiration (Hastings, 1981a) have so far been demonstrated only in isopods collected at various stages of the neaps/springs cycle of tides and recorded for a few days in the laboratory. It, therefore, still remains to confirm unequivocally in Eurydice, and in many other forms, which appear to show semilunar periodicity, that such rhythmicity is expressed as a free-running rhythm over long periods of time in constant conditions.

Environmental regulation of the burrow depth distribution of the sand-beach amphipod Talitrus saltator

The diurnal burrow depth distribution of Talitrus saltator, a sand-beach talitrid amphipod was examined in relation to moisture content and temperature profiles of the substrate. Individuals burrow to depths maintaining a moisture content of between 2·0 and 4·0% irrespective of the temperature profile, and therefore burrow depth is suggested to be regulated primarily by the requirements of the amphipods for an optimal humidity environment.

A circadian rhythm of oxygen consumption in the sand beach amphipod Talitrus saltator (Montagu)

A circadian rhythm of oxygen consumption is demonstrated in the supralittoral sand-beach amphipod Talitrus saltator (Montagu). A low diurnal respiratory rate is recorded with a nocturnal increase of ≈ 150 to 200%. The light-sensitive rhythm is endogenous, persisting in constant dark for at least 50 h. There is no suggestion of circatidal periodicity in the magnitude of the respiratory rhythm, nor is there any influence associated with the spring-neap tidal cycle. These observations, together with the absence of any respiratory rhythm during moult, are used to clarify the generation of the semi-lunar rhythm of locomotor activity reported in T. saltator.

The respiratory rhythm and respiratory quotient of Talitrus saltator

1. 1. An endogenous circadian rhythm of oxygen consumption was demonstrated in the amphipod Talitrus sakator. A low diurnal respiratory rate of approximately 0.55 μl O 2 mg −1 hr −1 was recorded with a nocturnal increase of between 137–195%. 2. 2. The circadian pattern was reflected in the oxygen consumption rate-size regression relationship, and the experimental significance of the rhythm was highlighted. 3. 3. The respiratory quotient of individually monitored amphipods was 0.80, suggesting lipid to be the major storage product used in basic metabolism.

The light-response rhythm and seasonal entrainment of the endogenous circadian locomotor rhythm ofTalitrus saltator(Crustacea: Amphipoda)

Talitrus saltator, a supralittoral, sand-beach amphipod, exhibits a nocturnal, circadian, locomotor rhythm entrained by the natural photoperiod (nLD). A phase-response curve (PRC) (light pulse: 2h/400 lx) of the free-running rhythm exhibits a conventional shape; steady-state delay shifts of approximately 3·5 h occur in response to light pulses around subjective dusk, with similar advance shifts when exposed to light pulses around dawn. The seasonal variation of the overt expression of the rhythm indicates that entrainment is predominantly non-parametric, while the constant phase-angle difference between the peak of locomotor activity and dawn confirms the latter as the effective field signal for entrainment. The qualitative relationship between the time scale of the PRC and nLD, together with the absence of any seasonal variation in the periodicity of the free-running rhythm (τ), suggests that entrainment occurs through the interaction of phase shifts defined by the PRC, essentially in response to the systematically changing photoperiod.

The effect of dusk and dawn on the locomotor activity rhythm of Talitrus saltator (Montagu) (Crustacea: Amphipoda)

Entrainment of the nocturnal, endogenous locomotor activity rhythm of Talitrus saltator (Montagu) by the natural light-dark cycle is non-parametric, the phase of the rhythm shifting only in response to changes in the time of an experimentally simulated ‘dawn’ transition. The difference in response to light at ‘dusk’ and ‘dawn’ illustrates a phase-dependent responsiveness common to endogenous rhythms. Activity begins after complete darkness, with cessation always occurring during the ‘dawn’ transition and never continuing past the onset of total experimental illumination. The point of activity cessation is taken to be the position of a synchronizing cue controlling entrainment. The ‘dawn’ cue appears to be an absolute irradiance level of approximately 1.5 × 10 −4 W/m 2 (1.5 lux). The implications of such a cue are discussed in relation to field behaviour.

Environmental influence on the locomotor activity rhythm of Talitrus saltator (Crustacea: Amphipoda)

The persistence and precision of the endogenous, nocturnal, circadian locomotor rhythm of the sand-beach amphipod Talitrus saltator is characterised, and the influence of substrate availability, photoperiod, temperature and relative humidity as potential environmental synchronizers of the rhythm is assessed. Individual, cyclic light-dark and temperature regimes synchronize and modify the laboratory activity pattern, but substrate availability and relative humidity have no significant long-term effect. Under simulateneous experimental regimes simulating field conditions of photoperiod, temperature and relative humidity the rhythm is entrained solely by photoperiod. The implications are discussed in relation to field behaviour.

Magnetic field detection is distinct from light detection in the invertebrates Tenebrio and Talitrus

THE mechanism used by animals for geomagnetic field detection has long been discussed1. Leask2 has proposed that sensitivity to magnetic field might result from polarised light detection through optical pumping into the lowest level triplet state of (say) the rhodopsin molecule that possesses spin. Light detection, he suggests, might be a prerequisite for magnetic field detection and might result in an axial rather than a polar response in the animal. However, a unimodal reaction has been found3 with Tenebrio molitor L., the flour-beetle, in a horizontally directed magnetic field and a light field without directional features. This result was obtained when Tenebrio had been allowed to associate the geomagnetic field with the directional properties of the anisotropic light field in the culture container. The preferential direction in the horizontally directed magnetic field could be predicted from the ‘dark direction’ and from the relative humidity in the container (ref. 3, expt 43, page 429). I report here that Tenebrio and Talitrus saltator Mont., the sandhopper, can orientate in the Earth's magnetic field in complete darkness, and that in Tenebrio this orientation is essentially polar, not axial. These results are evidence that these two invertebrates do not require light for the detection of the magnetic field.

The annual pattern of reproduction of Talitrus saltator (Crustacea: Amphipoda: Talitridae)

The reproductive cycle and breeding biology of Talitrus saltator (Montagu), a supralittoral talitrid amphipod, were investigated over a 15 month period on a sandy beach in the Isle of Man. The species is shown to have an annual, univoltine reproductive cycle with a period of high reproductive activity between May and late August. Two generations are present throughout most of the year and the life spans of female and male T. saltator were calculated to be approximately 18 months and 21 months respectively. Initial juvenile growth was rapid, juveniles attaining sexual differentiation within three to four months of hatching. 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 relative brood size of incubating females was shown to be dependent on at least two factors, the length of the female and the stage of embryological development of the brood.It is suggested that photoperiod is the major exogenous factor controlling gonadal maturation and the duration of reproductive activity in T. saltator.

ON THE LUNAR ORIENTATION OF SANDHOPPERS (AMPHIPODA TALITRIDAE)

1. Under the action of appropriate releasing stimuli the amphipod, Talitrus saltator, is capable of orienting by the position of the moon in a relatively constant azimuth. This ability still functions after 10 or more hours of captivity in constant darkness.2. The direction of escape and the degree of scatter are not noticeably influenced by the repeated photo-bulb flashes.3. Additional evidence supports the hypothesis that the lunar orientation of Talitrus is due to a continuously-operating lunar physiological rhythm. The hypothesis of a single-cycle night-time orientation rhythm, put forward for Orchestoidea corniculata, does not seem applicable to Talitrus saltator.

LUNAR ORIENTATION OF ORCHESTOIDEA CORNICULATA STOUT (AMPHIPODA)

1. The orientation of Orchestoidea corniculata in direct moonlight, compared with the orientation when moonlight is reflected from a mirror, demonstrates that apparent lunar position is the dominant night-time orienting stimulus for this organism.2. An analysis of the effects of repeated photographic recording of the orientation indicates that this species changes its angle of lunar orientation and the scatter about the average as a result of repeated electronic photo-bulb flashes.3. Using only single observations of each group of animals, in order to avoid these artifacts, it was determined that this species, kept in total darkness for ten or more hours before observation, orients at a relatively constant angle with the moon, regardless of lunar stage or position. This result is not compatible with the hypothesis that O. corniculata possesses a continuously-operating lunar physiological rhythm similar to that claimed for Talitrus saltator.4. When the amphipods were exposed to sunset and moonrise on the night of observation, there was an indication of subsequently time-shifted angles of orientation with the moon. The tentative hypothesis of a single-cycle night-time orientation rhythm, re-initiated by the appropriate stimuli each night, would explain such observations.