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Gray A. Williams - One of the best experts on this subject based on the ideXlab platform.
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research note rasping patterns of the high shore Limpet cellana grata
2014Co-Authors: Nicholas P Burnett, Karen A Villarta, Gray A. WilliamsAbstract:Patellid Limpets are dominant grazers on many rocky shores around the world, strongly influencing intertidal community structure as a result of their feeding on the epilithic biofilm and macroalgae (Branch, 1981; Lubchenco & Gaines, 1981; Hawkins & Hartnoll, 1983). To quantify grazing pressure, many studies have examined the temporal and spatial patterns of Limpet foraging excursions (e.g. Chelazzi, Della Santini & Santini, 1994; Santini, Ngan W Gray & Williams, 2010; Santini et al., 2011); nevertheless, integrating rasping intensity with observed movement patterns is rare (but see Chelazzi et al., 1994b), primarily due to difficulties involved in making such measurements. As a result, spatial and temporal variation of grazing has mostly been assessed during random sampling periods within a foraging excursion or in aquariums under laboratory conditions (Newell, Pye & Ahsanullah, 1971; Zeldis & Boyden, 1979; but see Chelazzi et al., 1994a, b). The Limpet Cellana grata (Gould) is an abundant grazer in the upper intertidal zone of Hong Kong (Morton M Davies et al., 2006). Despite the general movement patterns of this Limpet having been described in detail, grazing patterns are speculative because identifying when the animal is rasping the rock surface has proved difficult due to wave action (Williams & Morritt, 1995). Here we report the use of a contact microphone to record the rasping of C. grata individuals in situ and to describe the spatial and temporal variation of the Limpets’ rasping. Recordings of Limpet rasping were made with a contact microphone based on a LIS352AXMEMS inertial sensor (ST Microelectronics, Geneva, Switzerland). A 10-m length of paired and insulated 24 AWG wires with 50-cm leads (33 AWG wire wrap) was soldered to the sensor and the sensor was water-proofed with a small amount of Instant Mix 5 minute epoxy (Loctite, Westlake, OH, USA). The thin leads gave flexibility for the Limpet to move freely and reduced drag from wave action. The 24 AWG wires were connected to a 3.5-mm stereo phone plug and the whole system was powered by a 3 V battery pack. Recordings were made on a digital audio recorder (VN-6200 PC, Olympus, San Jose, CA). Continuous recordings were made of C. grata individuals (n 1⁄4 7; 30.8–56.2 mm shell length; Table 1) at Cape d’Aguilar, Hong Kong (228130N, 1148120E) in July, September and October 2012 during spring tides. Hong Kong experiences mixed, semidiurnal spring tides (see Williams, 1994, for a description of tidal patterns in Hong Kong) with a maximum amplitude of the high, high tide at Cape d’Aguilar of about 2.5 m above chart datum (þCD). Since C. grata moves up and down the shore following the tide, one tidal cycle represents one activity period. Microphones were attached at low tide while the Limpets were inactive and, for each Limpet, recordings commenced before movement began (or within about 15 min) and ended after movement ceased on the following ebb tide. Microphones were attached to the shell over each Limpet’s head with a mixture of adhesive putty and cyanoacrylate glue (Aron Alpha Gel, Japan). Hourly, real-time tidal heights were obtained from the Hong Kong Observatory station at Waglan Island, 5 km southeast of Cape d’Aguilar. Distinct rasping sounds were clearly distinguishable from wave swash or other background noises on the audio recordings (Fig. 1; Supplementary Material). Rasping rates were calculated from audio recordings following Petraitis (1992) and converted to rasps per minute (rpm). Rasping rates were calculated at 2-min intervals for the duration of each recording (i.e. 30 measurements per hour).
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Plasticity in the temporal organization of behaviour in the Limpet Cellana grata
Marine Biology, 2011Co-Authors: Giacomo Santini, Avis Ngan, Gray A. WilliamsAbstract:The behaviour of intertidal consumers is often tightly constrained to tidal movements, although activity patterns can vary within these constraints. Spatio-temporal variability in behaviour of a Limpet, Cellana grata, was analysed over different tidal conditions (spring and neap tides) and during different times of the year (one summer and one winter) at sites in Hong Kong. Activity was generally dictated by tidal movements, being concentrated when animals were awash. Plasticity in behaviour was observed, with some Limpets anticipating activity during the summer period and delaying activity during winter time. Limpets were active for a time equal, or slightly less, than time awash. As the time awash exceeded ~14–16 h, however, activity duration decreased. Within this general pattern, tidal variation as well as variation among times of the year was noted, with the lowest dependence on time awash being recorded during winter neap tides. Limpets showed a slight preference for being active during nighttime, which was particularly evident when animals were emersed during the summer period. Although the basic activity in C. grata is constrained to a specific temporal window, this Limpet is able to modulate its foraging strategies and resting height, according to local, daily changes in environmental conditions.
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physiological responses to heat stress on a tropical shore the benefits of mushrooming behaviour in the Limpet cellana grata
Marine Ecology Progress Series, 2005Co-Authors: Gray A. Williams, Maurizio De Pirro, Kenneth M Y Leung, David MorrittAbstract:Sub-lethal responses to heat stress were investigated in the Limpet Cellana grata. Dur- ing summer low tides, foot temperatures were hotter than rock temperatures, but positively corre- lated with, heart rate, air and rock temperatures. Hotter Limpets showed mushrooming behaviour, raising their shell from the rock. Over 30% of monitored Limpets were not relocated during the sub- sequent daytime low tide. Missing animals were mostly situated on horizontal surfaces, were smaller than those recaptured, and had higher body temperatures, mushrooming heights and heart rates. A laboratory protocol was designed to resemble on-shore thermal stress conditions. Firstly, small and large Limpets were held on a hot plate for 60 min and either constrained or allowed to mushroom. Secondly, unconstrained, large animals were held on the hot plate for 120 min. Unconstrained Limpets were able to mushroom and had lower foot temperatures but higher heart rates than those con- strained, suggesting mushrooming is an active response. Small animals had higher heart rates than large individuals. Mantle water could not be collected from most small, mushrooming Limpets but was from constrained animals, and was more concentrated in small Limpets. Small and constrained Limpets had more concentrated haemolymph than large or mushrooming animals. Mantle and haemolymph osmolalities were positively related, except at high mantle water osmolalities. Smaller animals lost relatively more water, and constrained Limpets more than those allowed to mushroom. Large Limpets on the hot plate for 120 min showed similar mushrooming heights and heart rates but had hotter foot temperatures, higher haemolymph concentrations, lost all their mantle water and nearly twice as much water than those held for 60 min. Mushrooming behaviour appears to be a short-term, high-risk strategy that allows Limpets temporary relief from stressful conditions and may increase their chance of survival until the next tidal immersion.
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Assessment of factors affecting heart rate of the Limpet Patella vulgata on the natural shore
Marine Biology, 2000Co-Authors: Giacomo Santini, Gray A. Williams, Guido ChelazziAbstract:Heart rate variations of a population of the Limpet Patella vulgata were monitored in the natural environment (Lough Hyne, southern Ireland) by non-invasive, optoelectronic recording. The heart rates of 145 Limpets of different sizes, living on vertical and horizontal substrata, were measured both in air and water at different environmental temperatures, while the animals were inactive on their home scars. The heart rates of emersed, inactive Limpets were positively related to air temperature and negatively related to Limpet size. These relationships were similar for Limpets on vertical and horizontal substrates. In contrast, no significant relationship between heart rate and temperature was found in submerged Limpets, probably due to the narrow thermal range of the water during the study period. During submersion, a significant negative relationship between heart rate and size was evident for Limpets on vertical surfaces but not for Limpets on horizontal surfaces. In general, submerged Limpets had a higher heart rate, 1.16 times that of Limpets exposed to air. Moreover, the heart rates of nine animals were recorded while they were moving and while inactive on their home scars. Active Limpets had a faster heart rate, 1.6 times that of Limpets resting on their home scars. The dependence of heart rate on environmental temperature, size, respiratory medium and activity, as observed in Limpets on the shore, agrees well with laboratory data and with previous findings of the correlation of oxygen consumption with the same factors. Such in situ measurements may, therefore, prove useful in attempts to determine natural levels of energy expenditure in models on the behaviour of foraging molluscs.
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Foraging in the Limpet Patella vulgata: the influence of rock slope on the timing of activity
Journal of the Marine Biological Association of the United Kingdom, 1999Co-Authors: Gray A. Williams, Colin Little, Linda Teagle, David Morritt, Penny Stirling, Alison Miles, Graham M. Pilling, Mireille ConsalveyAbstract:Preliminary observations of Limpet activity at Lough Hyne, in south-west Ireland, showed that individuals on steep slopes were primarily active at night, when emersed; while those on near-horizontal rocks were often active during daytime submersion. Observations of Limpet populations over an 11 d period of Limpet populations on a near-vertical and a near-horizontal site, only 45 m apart, confirmed that animals on the near-vertical site were active on nocturnal low tides, whilst those on the near-horizontal site were active on daytime high waters. A short-term survey at ten sites, which had Limpets on both extremes of slope (i.e. either near-vertical or near-horizontal), showed that Limpets on near-horizontal surfaces were, on average, more active at daytime high waters than those on near-vertical faces. In 1996 and 1997 surveys of activity at daytime high, and nocturnal low waters were conducted at sites (14–15) with varying rock slopes (∼3–87°). In all cases, Limpets on more steep slopes were active at nocturnal emersion whilst animals on more gentle slopes were active on daytime submersion periods. In most cases these trends were significant and explained between 22–40% and 37–44% of the variation in activity with site in 1996 and 1997 respectively. Analysis of the head orientation of Limpets on their home scars showed that animals orientated in a down shore direction at all sites (1997 data) suggesting that Limpets do perceive and respond to slope. Whilst slope does appear to influence the timing of Limpets' activity (and especially on very steep or gently sloping sites) it does not account for a large degree of the variation in activity and, on sites with slopes between 30 and 60°, is likely to work in combination with other factors.
Ross A. Coleman - One of the best experts on this subject based on the ideXlab platform.
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Up or down? Limpet orientation on steeply sloped substrata
Aquatic Biology, 2010Co-Authors: Clarissa M. L. Fraser, Ross A. Coleman, Judith C. KleinAbstract:Variation in the distribution of animals across the landscape, within and between habi- tats, can occur at a variety of scales. At the smallest scale, individuals can either be positioned ran- domly or can be orientated in regard to variables. Differences in orientation can, for many animals, directly affect their reproductive success and/or survivorship, and these effects may have down- stream ecological consequences. Organisms may orientate themselves in a specific way in response to varying environmental conditions or habitat properties; alternatively they may consistently orien- tate in a specific direction. The present study investigated patterns of orientation during low tide in the intertidal marine Limpet Cellana tramoserica on steeply sloped rocky surfaces (>60° to the verti- cal). We also examined whether individual Limpets consistently orientated in the same direction or if orientation was dependent upon their orientation during the previous low tide. There was a down- ward bias in orientation. Mensurative and manipulative experiments measuring Limpet orientation over different days showed that individual Limpets did not consistently orientate in the same direction and that their orientation was independent of their orientation during the previous low tide. Thus, whilst Limpets on slopes often orientate with their heads downwards, there is much inherent individ- ual variation in the orientation patterns exhibited by resting Limpets. Simple mechanistic explana- tions such as responses to desiccation are unlikely to be sufficient to explain why Limpets choose different orientations at the end of foraging excursions. These findings have implications for under- standing Limpet distributions on rocky shores and downstream ecological consequences.
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Limpet aggregation does not alter desiccation in the Limpet Cellana tramoserica
Journal of Experimental Marine Biology and Ecology, 2010Co-Authors: Ross A. ColemanAbstract:Abstract Animals, particularly intertidal snails, are frequently found in groups or aggregations. The biological explanations for such patterns frequently espouse a behavioural response to physical stresses, i.e. is that Limpets form groups to minimise desiccation risks. There is little or no reliable experimental evidence for this. I experimentally manipulated the surroundings of individual Limpets, such that grouped Limpets became solitary and solitary Limpets became grouped, with appropriate controls. If grouping reduced desiccation, this should result in a changed osmotic potential of circulatory fluid; a measure of desiccation. Testing this required new information on extraction and storage of haemolymph. The methods of extraction had a small, but significant, effect on the osmolality of haemolymph, with in-situ collection probably the most desirable. I found the haemolymph may be stored for up to 4 days at 4 °C and 3 weeks at − 10 °C without any measurable changes. The prediction of a link between desiccation and aggregation in Limpet was not supported. Hence the idea that Limpets may gain the benefit of reduce desiccation by joining a group was refuted. These results are similar to those from studies examining the vertical distribution of Limpets, that desiccation is not likely to be a causal factor in determining small spatial scale distributions of Limpets. It is less likely then that Limpet aggregation occurs in response to desiccation risks and it is more likely that behavioural responses to predation risk may be involved.
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a continental scale evaluation of the role of Limpet grazing on rocky shores
Oecologia, 2006Co-Authors: A.j. Underwood, Ross A. Coleman, João J. Castro, Lisandro Benedetticecchi, Per Aberg, Francisco Arenas, Julio Arrontes, R. G. HartnollAbstract:It is critical for our knowledge of biodiversity and ecosystem processes to understand how individual species contribute to ecosystem processes and how these contributions vary in space and time. We used a manipulative field experiment in five locations over 17° of latitude [from southern Portugal to the Isle of Man (British Isles)] to determine the relative response of rocky intertidal algal assemblages released from control by the grazing of Limpets. Response ratios showed that when Limpets were removed there was a trend of effects from north to south. In the north, grazing had a strong effect on algal assemblages, but removing grazers reduced spatial variability in assemblages. In the south, the effect of Limpet grazing was far weaker and removal of grazers had a much reduced impact on spatial variability. Here we show a clear trophic control of an ecosystem in that grazing by Limpets not only determines macroalgal abundance overall but also modifies ecosystem stability via variability in cover of algae.
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european scale analysis of seasonal variability in Limpet grazing activity and microalgal abundance
Marine Ecology Progress Series, 2001Co-Authors: Stuart R. Jenkins, Stephen J. Hawkins, Suzanne Kay, Ross A. Coleman, João J. Castro, Francisco Arenas, Julio Arrontes, J Bussell, Brezo Martinez, J OliverosAbstract:The film of microalgae and macroalgal propagules which coats intertidal rocks is the main food resource of Limpets, the dominant grazers on exposed shores of north-west Europe. Spatial and temporal variability in feeding activity of Limpets and abundance of microalgae were examined at mid-tide level across a European gradient from the Isle of Man in the British Isles to south-west Portu- gal. Feeding activity was assessed as the frequency of radula scrapes on wax surfaces placed on the shore. This was undertaken monthly at 2 shores at each of 4 locations, the Isle of Man, south-west Eng- land, northern Spain and south-west Portugal, over 1 yr. The abundance of the microalgal film was de- termined simultaneously at 3 of the 4 locations by measuring the concentration of chlorophyll a on the rock surface. The density and species diversity of Limpets increased with decreasing latitude. This was mirrored by a trend of increased levels of Limpet grazing, although 1 location (northern Spain) did not fit this trend. Seasonal changes in Limpet grazing intensity were found at 3 of the 4 locations, charac- terised by elevated grazing during the summer and autumn. The seasonal variations resulted from changes in the level of foraging of individual Limpets and were positively correlated with mean sea temperature in the Isle of Man and south-west England. The pattern of grazing activity was not solely a function of sea temperature. In the Isle of Man, grazing by Patella vulgata declined during the later stages of gonad development and increased following spawning. Seasonal variation in the standing stock of microalgae, measured as the concentration of chlorophyll a, was found at all 3 locations ex- amined, the Isle of Man, south-west England and northern Spain, with greater abundance in the win- ter compared to summer. This pattern was consistent over both large (among locations: 100s of kilo- metres) and medium (between shores: 1000s of metres) scales. There were no correlations between microalgal abundance and Limpet grazing activity at any location. There were significant negative cor- relations between chlorophyll a and maximum monthly air temperature and monthly sunshine hours. Comparison of microalgal abundance among locations showed a general decline in standing stock with decreasing latitude, but differences between specific locations varied with season. South-west England showed similar levels of microalgal abundance to the most northerly location (Isle of Man) in winter, and to the most southerly location (northern Spain) in the summer.
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Limpet Patella spp. Consumption by oystercatchers Haematopus ostralegus: a preference for solitary prey items
Marine Ecology Progress Series, 1999Co-Authors: Ross A. Coleman, John D. Goss-custard, Sarah E. A. Le V. Dit Durell, Stephen J. HawkinsAbstract:Patellid Limpets are very important grazers on NE Atlantic rocky shores, and can occur in clumps or as solitary individuals. When oystercatchers are foraging for Limpets on rocky shores, they are often presented with a choice between solitary and clumped Limpets. We attempted to establish whether oystercatchers express a preference for Limpet prey items from these different distributions. Oystercatchers spent far more time foraging in areas of less clumped Limpets than in areas of clumped Limpets, despite lower prey density. We found a strong preference for solitary prey items, and increased chances of successful predation of solitary Limpets. Possible explanations for this choice are discussed. This preference for attacking solitary Limpets may have important implications for rocky shore dynamics by shaping the spatial patterns of Limpets. This may then influence the probability of Fucus germlings escaping Limpet grazing.
Stephen J. Hawkins - One of the best experts on this subject based on the ideXlab platform.
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Rock-pools as nurseries for co-existing Limpets: Spatial and temporal patterns of Limpet recruitment
Regional Studies in Marine Science, 2020Co-Authors: Maria Inês Seabra, Stephen J. Hawkins, Cristina Espírito-santo, João J. Castro, Teresa CruzAbstract:Abstract Rock-pools are considered to be important habitats for early shore-life of intertidal Limpets. We investigated recruitment patterns of three co-existing Limpet species in the region of Sines (SW Portugal): the patellids Patella depressa and Patella ulyssiponensis, and the siphonariid Siphonaria pectinata. Juvenile Limpets (shell length ≤ 10 mm for P. depressa and ≤ 5 mm for S. pectinata) were counted in summer 2007 and winter 2009, in a wide range of intertidal habitats, on three natural shores (one shore inside the Port of Sines and two shores outside the Port, 4 and 9 km away). Temporal and among-shore patterns of abundance of recruits (shell length
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Barnacle cover modifies foraging behaviour of the intertidal Limpet Patella vulgata
Journal of the Marine Biological Association of the United Kingdom, 2019Co-Authors: Giacomo Santini, R. G. Hartnoll, Stuart R. Jenkins, Guido Chelazzi, Richard C. Thompson, Suzanne Kay, Stephen J. HawkinsAbstract:Limpets and barnacles are important components of intertidal assemblages worldwide. This study examines the effects of barnacles on the foraging behaviour of the Limpet Patella vulgata , which is the main algal grazer in the North-west Atlantic. The behaviour of Limpets on a vertical seawall on the Isle of Man (UK) was investigated using autonomous radio-telemetry, comparing their activity patterns on plots characterized by dense barnacle cover and plots from which the barnacles had been removed. Limpet behaviour was investigated at mid-shore level, but two different elevations were considered. This experiment revealed a significant effect of barnacle cover on the activity of P. vulgata . Limpets on smooth surfaces spent a greater proportion of total time active than did Limpets on barnacles. Movement activity was also greater in areas that were lower down in the tidal range. In general, Limpets were either predominantly active during diurnal high or nocturnal low tides and always avoided nocturnal high tides. Individuals on barnacles at the higher elevation concentrated their activity during nocturnal low water. All the other groups of Limpets (smooth surfaces on the upper level and all individuals on the lower shore) had more excursions centred around daylight hours with an equal distribution of activity between periods of low and high water. Inter-individual variability was, however, pronounced.
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Rare predation by the intertidal crab Pachygrapsus marmoratus on the Limpet Patella depressa
Journal of the Marine Biological Association of the United Kingdom, 2004Co-Authors: Ana Silva, Diana Boaventura, Augusto A. V. Flores, Stephen J. HawkinsAbstract:The predatory effects of Pachygrapsus marmoratus on populations of the intertidal Limpet Patella depressa were analysed on rocky shores located on the central coast of Portugal. Nocturnal observations on crab feeding behaviour were conducted and experimental exclusion cages were set in the substratum to assess density effects on Limpets. The results indicated that although crabs feed on adult Limpets the predatory level was minimal. Crabs used consistent tactics to detach Limpets from the substratum but the majority of the attacks were unsuccessful, possibly due to morphological and behavioural adaptations of Limpets. An alternative recruitment hypothesis is advanced to explain non-significant differences between experimental treatments and a possible predatory role on shaping levels of recruitment on lower levels of the shore is considered.
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Size matters: competition within populations of the Limpet Patella depressa
Journal of Animal Ecology, 2003Co-Authors: Diana Boaventura, Luís Cancela Da Fonseca, Stephen J. HawkinsAbstract:Competitive interactions within and between size-classes of the Limpet Patella depressa Pennant were investigated in central Portugal. Experimental enclosures of 25 x 25 cm containing marked Limpets were set up at mid-tidal level on the shore. Twelve treatments with different combination of densities and size-classes were assigned to the plots, with three replicates of each. Mortality was recorded every 15 days and length was measured monthly during the approximately 6 months of the experiment. 2. At the end of the experiment Limpets were collected for determination of length, height, dry weight, sex and gonad development. The availability of food was assessed indirectly by determination of chlorophyll concentration with spectrophotometric analysis of rock chips. Reduced density treatments showed very low mortality and substantially increased growth. Both size-classes of Limpets showed increased mortality and reduced growth in increased density treatments. This effect was, however, more marked for large than small Limpets when caged separately. 3. Although both size-classes could negatively affect each other, the effect of large Limpets on small was greater than the reverse. Large Limpets are superior competitors that may modulate the abundance of small Limpets on the shore. It is unlikely, however, that they will totally exclude small Limpets due to intensity of competition within the large size-class. Niche differentiation and high recruitment at low shore levels are other possible factors that can contribute to reduce competition between the size-classes.
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european scale analysis of seasonal variability in Limpet grazing activity and microalgal abundance
Marine Ecology Progress Series, 2001Co-Authors: Stuart R. Jenkins, Stephen J. Hawkins, Suzanne Kay, Ross A. Coleman, João J. Castro, Francisco Arenas, Julio Arrontes, J Bussell, Brezo Martinez, J OliverosAbstract:The film of microalgae and macroalgal propagules which coats intertidal rocks is the main food resource of Limpets, the dominant grazers on exposed shores of north-west Europe. Spatial and temporal variability in feeding activity of Limpets and abundance of microalgae were examined at mid-tide level across a European gradient from the Isle of Man in the British Isles to south-west Portu- gal. Feeding activity was assessed as the frequency of radula scrapes on wax surfaces placed on the shore. This was undertaken monthly at 2 shores at each of 4 locations, the Isle of Man, south-west Eng- land, northern Spain and south-west Portugal, over 1 yr. The abundance of the microalgal film was de- termined simultaneously at 3 of the 4 locations by measuring the concentration of chlorophyll a on the rock surface. The density and species diversity of Limpets increased with decreasing latitude. This was mirrored by a trend of increased levels of Limpet grazing, although 1 location (northern Spain) did not fit this trend. Seasonal changes in Limpet grazing intensity were found at 3 of the 4 locations, charac- terised by elevated grazing during the summer and autumn. The seasonal variations resulted from changes in the level of foraging of individual Limpets and were positively correlated with mean sea temperature in the Isle of Man and south-west England. The pattern of grazing activity was not solely a function of sea temperature. In the Isle of Man, grazing by Patella vulgata declined during the later stages of gonad development and increased following spawning. Seasonal variation in the standing stock of microalgae, measured as the concentration of chlorophyll a, was found at all 3 locations ex- amined, the Isle of Man, south-west England and northern Spain, with greater abundance in the win- ter compared to summer. This pattern was consistent over both large (among locations: 100s of kilo- metres) and medium (between shores: 1000s of metres) scales. There were no correlations between microalgal abundance and Limpet grazing activity at any location. There were significant negative cor- relations between chlorophyll a and maximum monthly air temperature and monthly sunshine hours. Comparison of microalgal abundance among locations showed a general decline in standing stock with decreasing latitude, but differences between specific locations varied with season. South-west England showed similar levels of microalgal abundance to the most northerly location (Isle of Man) in winter, and to the most southerly location (northern Spain) in the summer.
Christopher D G Harley - One of the best experts on this subject based on the ideXlab platform.
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Thermal stress and morphological adaptations in Limpets
Functional Ecology, 2009Co-Authors: Christopher D G Harley, Mark W. Denny, Katharine J. Mach, Luke P MillerAbstract:Summary 1On thermally stressful rocky shores, small, slow-moving ectotherms such as Limpets exhibit morphological characteristics such as high-spired and heavily ridged shells which may reduce the likelihood of reaching stressful or lethal body temperatures. 2The effects of shell height and shell surface area on predicted Limpet body temperatures were tested with a previously developed heat budget model. The model was parameterized with morphological data from three species (Lottia gigantea, Patella vulgata and Siphonaria gigas), which differ dramatically in their morphology and in the body temperatures they are likely to reach in the field. 3Limpet models and standard cones with higher height : length ratios lost heat to convection more readily than models with lower spired shells. 4Heavily ridged shells lost heat to convection more readily than smoother shells, but this effect was only pronounced at high wind velocities. 5When the heat budget model parameters were applied to a real environmental data set, the model predicts that maximum body temperatures and cumulative thermal stress vary among species. These differences are related primarily to the height : length ratio of the shell, and to a lesser extent to the presence of ridges. 6These results suggest that some intra- and interspecific variation in Limpet morphology may be phenotypic or evolutionary responses to variation in environmental temperatures. Our findings are supported by observed patterns of Limpet morphological variation across natural thermal gradients.
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Hot Limpets: predicting body temperature in a conductance-mediated thermal system.
The Journal of experimental biology, 2006Co-Authors: Mark W. Denny, Christopher D G HarleyAbstract:Living at the interface between the marine and terrestrial environments, intertidal organisms may serve as a bellwether for environmental change and a test of our ability to predict its biological consequences. However, current models do not allow us to predict the body temperature of intertidal organisms whose heat budgets are strongly affected by conduction to and from the substratum. Here, we propose a simple heat-budget model of one such animal, the Limpet Lottia gigantea, and test the model against measurements made in the field. Working solely from easily measured physical and meteorological inputs, the model predicts the daily maximal body temperatures of live Limpets within a fraction of a degree, suggesting that it may be a useful tool for exploring the thermal biology of Limpets and for predicting effects of climate change. The model can easily be adapted to predict the temperatures of chitons, acorn barnacles, keyhole Limpets, and encrusting animals and plants.
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light availability indirectly limits herbivore growth and abundance in a high rocky intertidal community during the winter
Limnology and Oceanography, 2002Co-Authors: Christopher D G HarleyAbstract:Light availability and consumer pressure are fundamental factors that structure aquatic communities, but their integrated effects are rarely studied in marine benthic systems. Using a factorial experiment, I investigated the effects of light availability and grazing by Limpets (Lottia digitalis) to determine the relative influence of each on the growth and abundance of producers and consumers in a rocky intertidal community during the winter. Light reduction via shading reduced the abundance of filamentous algae and reduced the abundance of the herbivorous periwinkle Littorina sitkana. The effects of Limpet grazing reduced the abundance of filamentous algae, Porphyra spp., and diatom mats. Higher Limpet densities were also associated with significantly lower densities of adult, but not juvenile, Littorina spp. Light and Limpet density interacted to determine Lottia growth, which was high in unshaded, single-Limpet enclosures but was negligible in plots with two Limpets, shades, or both. Variation in bottom-up (resource-driven) and top-down (consumer-driven) forces are important determinants of abundance at both trophic levels, but the effects are complex, taxon-specific, and, for littorine snails, size-specific. Because the study species accomplish most of their growth and reproduction during the winter, the interplay of light and herbivory during this season will likely influence long-term community dynamics.
A. N. Hodgson - One of the best experts on this subject based on the ideXlab platform.
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Growth and reproduction in the high-shore South African Limpet Helcion pectunculus (Mollusca : Patellogastropoda)
African Zoology, 2003Co-Authors: D R Gray, A. N. HodgsonAbstract:Growth and aspects of the reproductive biology of the high-shore Limpet Helcion pectunculusl/Ig were determined for a southeast and southwest coast population. Limpets grew allometrically, increasing in height faster than length (a =1.3 to 1.6). Growth rates (about 5-6 mm / year shell length), were similar in both the southeast and southwest coast population, as were the theoretical Llsubgmaxl/subg values of 30.86 mm and 30.71 mm, respectively. Maximum age of Limpets was calculated to be 5-6 years. H. pectunculusl/Ig is a protandrous hermaphrodite, males becoming sexually mature at about 10-12 mm shell length (about one year old), and changing sex at about 16 mm shell length (about two years old). This resulted in sex ratios of about two males to one female. Limpets from both geographic locations spawned mainly in summer (November / December) with a second smaller spawning in autumn (April). There was no significant difference in the gonad index (GI) between southeast coast males and females. However the GI of southwest coast males was about 5% greater than that of the females. The gonad indices of southeast coast and southwest coast Limpets was not significantly different.
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the reproductive cycle of helcion pruinosus patellogastropoda on two south african boulder shores
Journal of Molluscan Studies, 2001Co-Authors: Tony O Henninger, A. N. HodgsonAbstract:The reproductive cycle of the South African Limpet Helcion pruinosus was determined over 19 months for a south-east and south-west coast population. Despite inhabiting shores subjected to different oceanographic conditions, Limpets from both populations spawned mainly in summer with early gametogenesis occurring in spring. The gonads of Limpets were never completely spent suggesting that they are partial spawners. The gonad index (G.I.) of males was significantly greater than that of females in both populations and the G.I. of south-west coast Limpets greater than that of Limpets from the southeast coast. The sex ratio of the population on the south-west coast was 1:1 whereas the south-east coast population contained significantly more males.
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foraging activity of helcion pruinosus patellogastropoda on a south african boulder shore
Journal of Molluscan Studies, 2001Co-Authors: Tony O Henninger, A. N. HodgsonAbstract:Foraging activity of the mid-shore Limpet Helcion pruinosus was monitored on an exposed boulder beach in the Eastern Cape of South Africa. Numbers of Limpets active in 10 fixed quadrats were monitored and compared in different seasons and during spring and neap tides. Foraging excursions were mainly associated with nocturnal low tides, Limpets only emerging from beneath rocks when they were completely uncovered by the receding tide, and they had all retreated to beneath rocks before being splashed by the advancing tide. The number of animals active was greater on full moon spring tides. Significantly more Limpets were active on an autumn spring tide than on similar tides in other seasons.
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temporal variation in foraging behaviour of patella granularis patellogastropoda and siphonaria concinna basommatophora on a south african shore
Journal of Molluscan Studies, 1997Co-Authors: D R Gray, A. N. HodgsonAbstract:Foraging activity of two mid- to low- shore species of Limpet, Patella granulans (Prosobranchia) and Siphonaria concinna (Pulmonata) from an exposed shore on the Eastern Cape coast of South Africa was monitored. In both species, activity was compared during spring and neap tides and, in P. granulans between summer and winter. Rhythms of activity of the two species were similar, with foraging excursions being mainly associated with nocturnal low tide times, although some P. granularis foraged during daytime low tides. It is suggested that foraging excursions in P. granularis are triggered by wave action. Both species foraged further on spring tides than on neap tides and this is suggested to be a result of the limited time Limpets have to forage. P. granularis was also found to forage further during summer when compared to winter and the possibility that seasonal micro-algal productivity influences foraging distances in Limpets is discussed. The foraging activity of both species could be divided into 3 distinct phases, a relatively rapid outward phase, a much slower foraging phase and a rapid homeward phase. Whether or not these Limpets graze throughout an excursion is not known. S. concinna was found to home to a fixed scar, although during the experiment some scar-swapping occurred. P. granularis did not home to a fixed scar but possessed a 'home range' (approx. 5 cm2) to which it returned after each excursion. Patella granularis was found to move randomly during foraging, whilst S. concinna foraged in a nonrandom direction .which took individuals upshore. No tidal-influen ce is thought to be present in this case and the possibility of a learning component in the foraging behaviour of certain Limpet species in relation to the return to optimal feeding patches is discussed.
