Cellana Toreuma Research Articles

Causations of phylogeographic barrier of some rocky shore species along the Chinese coastline.

BackgroundSubstrate, ocean current and freshwater discharge are recognized as important factors that control the larval dispersal and recruitment of intertidal species. Life history traits of individual species will determine the differential responses to these physical factors, and hence resulting in contrasting phylogeography across the same biogeographic barrier. To determine how these factors affect genetic structure of rocky shore species along the China coast, a comparative phylogeographic study of four intertidal and subtidal species was conducted using mitochondrial and nuclear DNA by combining new sequences from Siphonaria japonica with previously published sequences from three species (Cellana toreuma, Sargassum horneri and Atrina pectinata).ResultsAnalysis of molecular variance and pairwise ΦST revealed significant genetic differences between the Yellow Sea (YS) and the other two marginal seas (East China Sea, ECS and South China Sea, SCS) for rocky-shore species (S. japonica, C. toreuma, S. horneri), but not for muddy-shore species Atrina pectinata. Demographic history analysis proved that the population size of all these four species were persistent though the Last Glacial Maximum (LGM, ~20 ka BP). Migration analysis revealed that gene flow differentiated northward and southward migration for these four species. However, the inferred direction of gene flow using alternatively mitochondrial or nuclear markers was contradictory in S. japonica.ConclusionsIt is concluded that there is a phylogeographical break at the Yangtze River estuary for the rocky shore species and the causation of the barrier is mainly due to the unsuitable substratum and freshwater discharge. All four intertidal and subtidal species appear to have persisted through the LGM in China, indicating the lower impact of LGM on intertidal and subtidal species than generally anticipated. The imbalanced gene flow between YS and ESCS groups for these four species could be explained by historical refugia. The discordance between mitochondrial and nuclear markers in the MIGRATE analysis of S. japonica prove the importance of employing multi-locus data in biogeographic study. Climate change, land reclamation and dam construction, which are changing substrate and hydrological conditions around Yangtze River estuary, will consequently affect the biogeographic pattern of intertidal species.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0387-0) contains supplementary material, which is available to authorized users.

Latitudinal variability of physiological responses to heat stress of the intertidal limpet Cellana toreuma along the Asian coast

Potential future distribution shifts of intertidal invertebrates along the Asian coast in the face of global change remain unclear. Integrative study that comprise environmental temperature monitoring and comparative physiological study of thermal adaptation among different geographical populations of species are important to identify population-related differences in thermal ecology that could affect the persistence of species in their present distribution ranges. In the present study, in situ operative temperatures were recorded continuously for 5 mo from August 2011 to January 2012, and measurements of lethal temperature, cardiac performance and gene expression were carried out in 3 geographical populations of the limpet Cellana toreuma (tropical shore: Sichang Island, Thailand; subtropical shore: Nanding Island, Zhangzhou, China; temperate shore: Dagong Island, Qingdao, China). Compared to limpets on the tropical shore in Sichang Island with high mean temperature (28.28°C) and narrow thermal range (19.13 to 46.56°C), limpets on the subtropical shore in Nanding Island have to cope with a thermal environment characterized by a wider temperature range (6.42 to 44.98°C). The absence of differences in lethal temperature (LT50) of limpets from all the locations indicates that limpets currently suffer from intensive heat stress across their biogeographic range. Although the populations lacked differences in upper thermal limit, variations were noted among populations in transcriptional responses in genes linked to energy metabolism. Limpets on the subtropical shore in Nanding Island live closer to their upper thermal limits and thus will be very sensitive to future temperature increases.

Temperature relations of aerial and aquatic physiological performance in a mid‐intertidal limpet Cellana toreuma: Adaptation to rapid changes in thermal stress during emersion

The physiological performance of a mid-intertidal limpet Cellana toreuma was determined to study the physiological adaptation of intertidal animals to rapid changes and extreme temperatures during emersion. The relationship between the Arrhenius breakpoint temperature (ABT) and in situ operative body temperature was studied to predict the possible impact of climate change on the species. The temperature coefficient (Q10) of emersed animals was higher than that of submersed animals and the ratio of aerial: aquatic heart rate rose with increasing temperature. The ABTs of submersed and emersed animals were 30.2 and 34.2°C, respectively. The heart rate and levels of molecular biomarkers (hsps, ampkα, ampkβ and sirt1 mRNA) were determined in 48 h simulated semi-diurnal tides. There were no obvious changes of heart rate and gene expression during the transition between emersion and submersion at room temperature, although expressions of hsp70 and hsp90 were induced significantly after thermal stress. These results indicate that C. toreuma can effectively utilize atmospheric oxygen, and the higher Q10 and ABT of emersed animals are adaptations to the rapid change and extreme thermal stress during emersion. However, the in situ operative body temperature frequently exceeds the aerial ABT of C. toreuma, indicating the occurrence of large-scale mortality of C. toreuma in summer, and this species should be sensitive to increasing temperature in the scenario of climate change.

Stress modulation of cellular metabolic sensors: interaction of stress from temperature and rainfall on the intertidal limpet Cellana toreuma.

In the natural environment, organisms are exposed to large variations in physical conditions. Quantifying such physiological responses is, however, often performed in laboratory acclimation studies, in which usually only a single factor is varied. In contrast, field acclimatization may expose organisms to concurrent changes in several environmental variables. The interactions of these factors may have strong effects on organismal function. In particular, rare events that occur stochastically and have relatively short duration may have strong effects. The present experiments studied levels of expression of several genes associated with cellular stress and metabolic regulation in a field population of limpet Cellana toreuma that encountered a wide range of temperatures plus periodic rain events. Physiological responses to these variable conditions were quantified by measuring levels of mRNA of genes encoding heat-shock proteins (Hsps) and metabolic sensors (AMPKs and Sirtuin 1). Our results reveal high ratios of individuals in upregulation group of stress-related gene expression at high temperature and rainy days, indicating the occurrence of stress from both prevailing high summer temperatures and occasional rainfall during periods of emersion. At high temperature, stress due to exposure to rainfall may be more challenging than heat stress alone. The highly variable physiological performances of limpets in their natural habitats indicate the possible differences in capability for physiological regulation among individuals. Our results emphasize the importance of studies of field acclimatization in unravelling the effects of environmental change on organisms, notably in the context of multiple changes in abiotic factors that are accompanying global change.

Temporal patterns of cardiac performance and genes encoding heat shock proteins and metabolic sensors of an intertidal limpet Cellana toreuma during sublethal heat stress

Intertidal invertebrates develop effective physiological adaptations to cope with the rapidly changing thermal environment in the intertidal zone. In the present study, the temporal patterns of heart rate, protein carbonyl groups, and genes encoding heat shock proteins (hsp70 and hsp90) and metabolic sensors (ampkα, ampkβ and sirt1) were measured to study the effect of sublethal heat stress on the cardiac function, oxidative stress, heat shock response and cellular metabolism of an intertidal limpet Cellana toreuma. All the physiological parameters are sensitive to temperature and duration of heat stress. Spearman correlation analysis revealed that the correlations between heart rate and levels of heat shock proteins mRNA and metabolic sensors mRNA were statistically significant. These results further suggest that cardiac function plays crucial roles in cellular energy metabolism and heat shock responses. The significant increase of protein carbonyl groups at 34°C after 4h exposure indicated that the failure of cardiac function and the increase of anaerobic metabolism partly leads to the increase of protein carbonyl groups. Generally, the physiological responses to heat stress are sensitive to temperature and are energy-consumptive, as indicated by the upregulation of metabolic sensors mRNA. However, the upregulation of heat shock proteins and metabolic sensors at the post-transcriptional level and related functions need to be confirmed in further experiments.

Distribution of Unusual Cholesterol Precursors, 4-Methyl- and 4, 4-Dimethylsterols with ^|^Delta;8 Unsaturation, in Gonads of Marine Archaeogastropods

In the present study, we show that four unusual cholesterol precursors, 5α-cholesta-8,14-dien-3β-ol, 4-methyl-5α-cholesta-8,24-dien-3β-ol (4-methylzymosterol), 4,4,14-trimethyl-5α-cholesta-8,24-dien-3β-ol (lanosterol), and 4,4-dimethyl-5α-cholesta-8,24-dien-3β-ol (4,4-dimethylzymosterol) are present in testes of the limpet Cellana grata, which is part of one of the most primitive gastropod families (Nacelllidae Family). The distribution of these sterols in testes and ovaries of four dominant species of limpets, Cellana grata, Cellana toreuma, Nipponacmea concinna, and Nipponacmea fuscoviridis, was examined by capillary gas chromatography-mass spectrometry. Based on the data, we discuss about the biological roles and possible application as bio-resources of these sterols. This is the first identification of 5α-cholesta-8, 14-dien-3β-ol, 4-methylzymosterol, and 4,4-dimethylzymosterol in marine invertebrate gonads.

Metabolic energy sensors (AMPK and SIRT1), protein carbonylation, and cardiac failure as biomarkers of thermal stress in an intertidal limpet: linking energetic allocation with environmental temperature during aerial emersion

The effects of heat stress on organisms are manifested at the levels of organ function, metabolic activity, protein stability and gene expression. Here, we examined effects of high temperature on the intertidal limpet Cellana toreuma to determine how the temperatures at which (1) organ failure (cardiac function), (2) irreversible protein damage (carbonylation) and (3) expression of genes encoding proteins involved in molecular chaperoning (hsp70 and hsp90) and metabolic regulation (ampk and sirt1) occur compare with field temperatures, which commonly exceed 30°C and can reach 46°C. Heart failure, indexed by the Arrhenius break temperature, occurred at 34.3°C. Protein carbonylation rose significantly at 38°C. Genes for heat shock proteins HSP70 (hsp70) and HSP90 (hsp90), for two subunits of AMP-activated protein kinase (AMPK) (ampkα and ampkβ) and for histone/protein deacetylase SIRT1 (sirt1) all showed increased expression at 30°C. Temperatures of maximal expression differed among genes, as did temperatures at which upregulation ceased. Expression patterns for ampk and sirt1 indicate that heat stress influenced cellular energy homeostasis; above ~30°C, upregulation of ATP-generating pathways is suggested by elevated expression of genes for ampk; an altered balance between reliance on carbohydrate and lipid fuels is indicated by changes in expression of sirt1. These results show that C. toreuma commonly experiences temperatures that induce expression of genes associated with the stress response (hsp70 and hsp90) and regulation of energy metabolism (ampk and sirt1). At high temperatures, there is likely to be a shift away from anabolic processes such as growth to catabolic processes, to provide energy for coping with stress-induced damage, notably to proteins.

The Impact of Yangtze River Discharge, Ocean Currents and Historical Events on the Biogeographic Pattern of Cellana toreuma along the China Coast

AimGenetic data were used to measure the phylogeographic distribution of the limpet, Cellana toreuma along the China coast in order to acsertain impacts of historic events, ocean currents and especially freshwater discharge from the Yangtze River on the connectivity of intertidal species with limited larval dispersal capability.Methodology/Principal FindingsGenetic variation in 15 populations of C. toreuma (n = 418), ranging from the Yellow Sea (YS), East China Sea (ECS) and South China Sea (SCS), were determined from partial mitochondrial cytochrome c oxidase subunit I gene. Genetic diversity and divergence based on haplotype frequencies were analyzed using CONTRIB, and AMOVA was used to examine genetic population structure. Historic demographic expansions were evaluated from both neutrality tests and mismatch distribution tests. Among the 30 haplotypes identified, a dominant haplotype No. 1 (H1) existed in all the populations, and a relatively abundant private haplotype (H2) in YS. Pairwise FST values between YS and the other two groups were relatively high and the percentage of variation among groups was 10.9%.ConclusionsThe high nucleotide and gene diversity in the YS, with large pairwise genetic distances and relatively high percentages of variation among groups, suggests that this group was relatively isolated from ECS and SCS. This is likely driven by historic events, ocean currents, and demographic expansion. We propose that freshwater discharge from the Yangtze River, which may act as physical barrier limiting the southward dispersal of larvae from northern populations, is especially important in determining the separation of the YS group from the rest of the Chinese populations of C. toreuma.

Localization of intracrystalline organic macromolecules in mollusk shells

As a crucial first step for understanding the organic–inorganic interaction in biomineralization of mollscan shells, localization of the intracrystalline organic macromolecules in biogenic calcium carbonate crystals of the nacreous, prismatic ( Pinctada fucata) and foliated ( Cellana toreuma) microstructures were investigated using Fresnel contrast analysis in a transmission electron microscope. Spherular Fresnel contrasts in the crystals correspond to organic substances, which was confirmed by the detection of 1s→π ⁎ (CC) transition peak at 284 eV in electron energy loss spectroscopy. Nano-sized (5–10 nm) spherules in the aragonite tablets constituting the nacreous layer of P. fucata specifically concentrate in the vicinity of the interlamellar membrane between the aragonite tablets. The dominant sizes of the organic macromolecules extracted by dissolving the aragonite tablets in the nacreous layer of P. fucata were estimated using the gel-filtration analysis to be roughly 10 and 4 nm, which dimensionally corresponds to the sizes observed by Fresnel contrast imaging in the tablets. These results will serve for understanding the functions of intracrystalline organic macromolecules in mollusk shells.

New alien species in the Atlantic Ocean?

The family Patellidae has been recognized as a complex taxonomic group for many years and its poor fossil record has complicated the study of the group. One of these limpet species, Cymbula nigra has its distributional range from Namibia to the Mediterranean and two varieties of Cymbula nigra (formerly named Patella nigra) have been reported: Patella nigra plumbea (typical form widely spread) and Patella nigra ghananis (variety from Ghana). The results of the present study clearly show that some specimens from Ghana reported as Cymbula nigra belong to a different species. In fact, this species is closely related to Cellana toreuma from Java (Indonesia), whereas specimens from Java appear as a distinct and cryptic species of Cellana toreuma distributed in Japan to Hong Kong. The specimens from Ghana could have been recently introduced in West Africa from the Indian Ocean. It represents the first record of the genus Cellana in the Atlantic. Furthermore, the variety described as Patella nigra ghananis in the previous literature probably were specimens of this new Cellana species.

The influence of multiple environmental stressors on the limpet Cellana toreuma during the summer monsoon season in Hong Kong

Although environmental stressors affect natural systems in a multitude of ways, the interactive effect of multiple stressors on ecological assemblages remains largely misunderstudied. On tropical shores which experience seasonal monsoons, rocky intertidal habitats are physiologically stressful environments, being strongly affected by high temperatures and monsoon rains during emersion. In Hong Kong the limpet, Cellana toreuma, often takes refuge in mid-shore tidepools. In summer, these populations experience high mortality, probably as a result of stressful environmental conditions during low-spring tide days with high temperatures and/or intense rainfall periods can occur. Laboratory experiments were designed to mimic the effects of temperature stress (and increasing pool salinity) and reduced salinity as a result of monsoon rains on C. toreuma in tidepools . In general, haemolymph osmolality increased with salinity and limpet mortality increased with temperature. As salinity decreased after simulated rainfall, haemolymph osmolality (after 60 min) and survival (after 180 min) were significantly lower than in control treatments. Salinity fluctuations, coupled with high temperatures during emersion had both sub-lethal physiological effects and lethal effects on limpets in tidepools. Conducting experiments of multiple stressors simultaneously, however, revealed no interaction between hot temperatures and salinity variation, both of which operated independently for different response variables. Individually, therefore, hot temperatures and large salinity changes associated with the wet monsoon season are likely to play an important role in the population dynamics of intertidal species such as C. toreuma, and as a result will influence the structure and functioning of tropical rocky shores.

Impacts by heavy-oil spill from the Russian tanker Nakhodka on intertidal ecosystems: recovery of animal community

The impact of a heavy-oil spill from the Nakhodka on an intertidal animal community, and the recovery process of animals from the damage were surveyed from the autumn of 1997 to the spring of 2001. The field study was carried out in the rocky coast of Imago-Ura Cove, located along the Sea of Japan, where clean-up operations for oil pollution had been conducted less intensely than in other polluted areas. We have examined individual number of each animal taxon by continuously placing a quadrat of 5 m width along the entire intertidal zone of the cove. A total of 76 invertebrate taxa including 57 species of mollusks, 10 species of crustaceans were observed during the survey. The number of taxa increased from 1998 to 1999 in areas where the initial oil pollution was intense. Total individual number of benthic animals continued to increase from 1998 to 2000 in the polluted areas. The impact of oil on benthic animals was different from species to species. Some species such as Cellana toreuma and Monodonta labio confusa increased rapidly after the oil spill, whereas other species such as Patelloida saccharina lanx and Septifer virgatus did not show any apparent temporal tendencies. Population size structure of P. saccharina lanx varied greatly among years, however that of M. labio confusa did not. For P. saccharina lanx, recruitment was unsuccessful in 1997, possibly due to the effect of oil pollution. These differences in responses to oil pollution among benthic animals are considered to be caused by the differences in habitat use, susceptibility to heavy-oil, life history and migration ability. The findings suggest that it took at least 2–3 years for the intertidal animal community to recover to its original level after the oil spill.

ESCAPE RESPONSES OF INTERTIDAL GASTROPODS ON A SUBTROPICAL ROCKY SHORE IN HONG KONG

Frequent encounters between a specific pair of predator and prey are assumed to be the basic condition for escape responses to evolve and is widely applied to temperate gastropods. This study tested the applicability of this hypothesis in a subtropical situation. The escape responses of rocky shore gastropods were investigated at the Cape d'Aguilar Marine Reserve, Hong Kong. The species investigated were Cellana grata, Cellana toreuma, Siphonaria atra, Chlorostoma argyrostoma, Lunella coronata, Monodonta labio, Nerita albicilla, Nodilittorina radiata, Nodilittorina trochoides and Planaxis sulcatus. These were tested against the slow-moving predatory gastropods, Thais clavigera, Thais luteostoma and Morula musiva, and a starfish Coscinasterias acutispina. The species-specific escape responses of the gastropods were investigated through staging contacts between the gastropods and predators in situ. The nature of the stimulus for the escape response was identified through the `beaker' and Y-maze experiment in vitro, which mimic the conditions in a rock pool and under flowing water, respectively. Qualitative encounter rate between predator and prey was recorded and expressed in terms of habitat overlap, including vertical zonation, microhabitat use, and diel activities. The results show that the encounter frequency hypothesis can be applied only partially to the Cape d'Aguilar gastropods, as there are times when encounter rate and responsiveness were not proportional. This discrepancy thought to be due to the physical constraints on the shore and variations in shell morphology.

Interspecific variation in heavy metal body concentrations in Hong Kong marine invertebrates

Accumulated body concentrations of cadmium, copper and zinc were investigated in 19 species of intertidal invertebrates (the barnacles Tetraclita squamosa, Capitulum mitella, Balanus amphitrite, Megabalanus volcano, the bivalves Saccostrea cucullata, Septifer virgatus and Brachidontes atratus, the chiton Acanthopleura japonica and the gastropods Cellana grata, Cellana toreuma, Patelloida saccharina, Patelloida pygmaea, Siphonaria japonica, Tegula argyrostoma, Lunella coronata, Monodonta labio, Nerita albicilla, Thais clavigera and Thais luteostoma) collected from a relatively unpolluted area in Hong Kong, i.e. two shores within the Cape d'Aguilar Marine Reserve. In general body metal concentrations could be explained by the accumulation strategy of the analysed organism and by physiological requirements for the essential metals, i.e. copper and zinc. Zinc concentrations were, therefore, greatest in the barnacles and the oyster S. cucullata. Copper concentrations were greatest in those gastropods containing the respiratory pigment haemocyanin and in S. cucullata. One species collected from the sheltered shore, i.e. T. luteostoma, had much higher copper body concentrations compared with exposed shore conspecifics and this may be attributed to a diet that was dominated by oysters, which have high copper body concentrations. In contrast to both copper and zinc, cadmium body concentrations showed little interspecific variation.

Variation in abundance and distribution of the chiton Acanthopleura japonica and associated molluscs on a seasonal, tropical, rocky shore

AbstractTemporal and spatial distribution of the chiton Acanthopleura japonica and associated molluscs were recorded on a semi‐exposed tropical rocky shore in Hong Kong over 24 months. Most molluscs showed a clear vertical distribution pattern which varied with season. Many mobile gastropods, e.g. Monodonta labio, Cellana toreuma, Nerita albicilla and Thais clavigera, were found lower on the shore in summer (June–September), presumably as a response to the hot, desiccating conditions, but extended their range during winter (December–March). Acanthopleura, was distributed throughout the eulittoral and did not show such strong seasonal patterns, possibly due to the ability to use spatial refuges (specifically crevices) as a result of its flexible body‐plan. Chitons exposed on horizontal rocks lost more body water during periods of emersion as compared to those in vertical or crevice habitats and, in summer, all animals on horizontal surfaces died. It is suggested that A. japonica uses cracks and crevices, which are not available to hard‐shelled molluscs, throughout the year to reduce the impact of heat and desiccation stress during periods of emersion. This ability may explain the slight seasonal changes seen in Acanthopleura as compared to other species, and the dominance of chitons as herbivores on tropical shores.

Interindividual Trail Following by the Intertidal Patellid Limpet Cellana Toreuma

Interindividual trail following by the patellid limpet Cellana toreuma was studied by field observations for more than ten successive days in the non-reproductive period. This behaviour was more frequent during spring tides than neap tides, when the limpets were moving longer distances in response to greater tidal amplitudes. Small individuals performed this behaviour with longer distances and higher frequencies than did larger individuals. Path analysis revealed that total distance moved during foraging excursions and mean resting site height had direct and indirect positive effects on the frequency of the interindividual trail following, respectively, and shell length and frequency of intraindividual trail following exerted a direct, negative effect.

Translocation of Ferritin and Biomineralization of Goethite in the Radula of the Limpet Cellana toreuma Reeve

The radula of the limpet, Cellana toreuma, consists of a continuous series of teeth in various stages of iron biomineralization. The major iron-binding protein of the limpet's iron-containing granule (siderosome) has been purified and identified as ferritin. Limpet ferritin has a Mr of 575 kDa and can be resolved into two bands by SDS-PAGE analysis, with respective Mrs of 26 and 21 kDa. The partial N-terminal amino acid sequences of these two subunits were confirmed, and antisera against them were respectively generated. The specifity of these two antisera shows no difference between them. By using transmission electron microscopy and immunogold staining techniques the following two events were revealed: (1) in the superior epithelial cell of the radula, ferritin was disassembled through autophagy or heterophagy before exocytosis; (2) of the limpet ferritin, at least the 26-kDa subunit was found to pass through the microvilli, resulting in the accumulation of iron in the extracellular tooth chamber and the formation of goethite needles. Intracellular ferritin being translocated to the extracellular environment is discussed in the text.

Analyses of limpet defense and predator offense in the field

Between November 1982 and August 1984 diving observations of two intertidal limpets' defensive behaviours in response to two predatory species were made near the Seto Marine Biological Laboratory of Kyoto University, in Wakayama Prefecture, Japan, for over 800 h. The focus of the observations was a simple isolated rock, 0.9 m2 in area with an inclination of 75°. The pulmonate homing limpet Siphonaria sirius responded by fleeing from its home in response to the whelk Thais clavigera and by calmping tightly to its home scar in response to the starfish Coscinasterias acutispina. Both behaviours were successful for avoiding predation. After a whelk moved far away, limpets returned to their homes. The patellid limpet Cellana toreuma showed mantle folding behaviour or fled for an average distance of 8 cm vertically upwards in response to the whelk and for an average distance of 21 cm vertically upwards in response to the starfish. The amount of time predators spent foraging increased in the low intertidal zone relative to the mid and high zones, and most predator attacks were observed during the limpets' resting periods (submersion in late afternoon or nighttime). The upward directional flight displayed by C. toreuma was related to the upward orientation of the limpets' heads when they are in a resting position. Half of the limpets observed fleeing downward away from a starfish, a movement elicited by a downward attack, received a second attack. These limpets were preyed upon at the second encounter 67% of the time. The upward fleeing behaviour of C. toreuma resulted in the shifting of its resting site higher up the study site where fewer attacks occurred and where the mortality rate was at its lowest. It is suggested that the homing behaviour of S. sirius and the upward fleeing behaviour of C. toreuma are mechanisms by means of which interspecific competition between limpets is reduced and coexistence on a small rock surface is maintained.

Factors affecting individual variation in resting site fidelity in the patellid limpet, Cellana toreuma (Reeve)

AbstractAn investigation was made of individual variation in resting site fidelity in the limpet, Cellana toreuma, with special attention to the adaptiveness of its homing behaviour. Limpets resting in the higher part of the study site showed strong resting site fidelity while those in the middle part showed weaker fidelity and tended to shift their resting sites to higher parts. Limpets resting in the lower part where there were an abundant supply of food and high predation intensity, had the strongest resting site fidelity and always returned to fixed resting sites with mucous sheets. The resting site fidelity varied continuously among individuals. Four causes for shift of resting site were detected: fleeing from starfish, Coscinasterias acutispina, pushing contests for resting site, non‐returning excursions following and without following other's trail. The frequency of shift of resting sites due to each of these causes varied among individuals. Estimation of energy budget during about half a month showed that the location of resting site and frequency of shift of the site considerably affected the growth of limpets through energy expenditure by respiration and stationary mucus secretion, and energy intake by foraging. These variations were proposed as being a result not of density dependent dispersal nor adaptation to a single factor such as desiccation, heavy wave impacts or predation, but being due to individual difference in a compromise between two conflicting factors, susceptibility to predation and accessibility to food resources.

Studies on activity pattern of the patellid limpet Cellana toreuma (Reeve)

The habits and activity of Cellana toreuma (Reeve) have been studied in a field population. Activity is very high at ebb and flood tide, independent of the time of day, and sharply decreases during complete submergence or complete exposure. Duration of movement fluctuates with tidal amplitude; when neap tide, movement does not stop during low tide owing to continuous awash conditions. Vertical movement entirely coincides with tidal direction at day and night. In this way, the movement does not depend on light but chiefly the tide. Compared with a nocturnal limpet, C. nigrolineata (Reeve), the divergence in the behavioural patterns may be a function of the extent to which limpets are influenced by light. Duration of movement and distance increase with limpet size. Homing behaviour was not observed.