Tidal Rhythm Research Articles

The feeding relationships of the larger fish species in a Scottish sea loch

Patterns within a fish assemblage have been examined from catches obtained over a period of 17 months using fixed nets and rod and line sampling. A total of 19 species were caught with summer samples dominated by dab and saithe and winter samples by whiting. Cod were caught regularly throughout the year. Catches at the study site of dab and whiting occurred mainly at night but for cod and saithe catches occurred throughout the day. There was no indication ofa crepuscular or tidal rhythm for any species. Differences between our own observations and those from other published studies lead us to conclude that no species‐specific generalizations about feeding periodicities can be made. Feeding patterns are more likely to be determined by site‐specific features of particular habitats and their associated prey and predator assemblages.Examination of stomach contents data using a variety of methods indicates that conclusions are highly dependent on the form of the resource matrix used. However, our analyses indicate that during summer cod and dab feed on a much narrower range of prey than saithe and that there is significant overlap in their diets if a resource matrix based on percentage occurrence of prey species is used. Nevertheless, most diet overlap values for the species examined were low (between 0.1 and 0.2) suggesting that competition for food is unlikely. To date, no experiments have been performed to test the hypothesis that cod and dab compete for food.

Comparative studies of tidal rhythms. x. a dissection of the persistent activity rhythms of the crab,sesarma

The spontaneous locomotor activity of 86 penultimate‐hour crabs was studied during the last 4 summers in constant darkness, and in normal and reversed light/dark cycles. In constant conditions some of the individuals exhibited only solar‐day rhythms, some displayed only tidal rhythms, and some described both. The normal and reversed light/dark cycles entrained the solar‐day rhythm, but produced only masking and relative coordination in the tidal components. In 3 crabs, one of the two tidal peaks split, indicating that these peaks can act independently of one another. This suggests that the tide‐associated display of Sesarma—like 5 other crab species—may use two circalunidian clocks, one to control each peak in this rhythmic display.

Short-term shell growth in bivalves: Individual, regional, and age-related variations in the rhythym of deposition ofCerastoderma (=Cardium) edule

The influence of potential sources of variations (age, site, region) on the production of shell microgrowth increments was studied in the cockleCerastoderma edule (L.) from the shores of Denmark, Jersey Island and South Wales between 1978 and 1986. Microgrowth increments in the shell of the cockle were counted between annual growth marks corresponding to the second, third, and fourth yearly growth period of the cockle. The number of microgrowth increments per year showed a decrease with increasing age. Increments formed after deposition of the last annual mark in cockles sampled at different dates indicate that the rate of increment formation differed between age classes and populations. Furthermore, we observed pronounced intrapopulation differences in the number of increments for specimens of the same age, and differences in both number and clarity of increments in subtidal and intertidal populations. Our results do not support the hypothesis of a general endogenous rhythm of microgrowth that closely corresponds to tidal rhythms inCerastoderma edule. Instead, they emphasize the plasticity of deposition according to the origin and age of the experimental specimens.

Tide versus storm in Epeiric coastal deposition: Two Proterozoic sequences, India

AbstractThe relative importance of tides and storms in coastal sedimentation in ancient epeiric seas is frequently problematical. Here we appraise the depositional regimes in two Proterozoic Vindhyan formations in India with the aim of elucidating the records of each of these processes. The respective products of the two processes are not easily distinguished as both of them entail repeated fluctuations in water level and depositional energy. Two orders of fluctuation are recognized in both formations. The nature and scale of these two orders of fluctuation along with high‐resolution facies analysis make the distinction between the respective products of the two processes possible. Many of the features so long counted as characteristics of tidal rhythms, in the studied formations, exclusively or frequently manifest waxing and waning of storms or fairweather–storm cyclicity. This study highlights the need for reevaluation of ancient coastal sequences in epeiric setting.

Differences in the swimming behaviour of the amphipod Corophium volutator from different populations

The swimming behaviour of Corophium volutator from Wales and East Anglia was investigated to establish whether differences apparent from two previous studies are real or artefacts of the different techniques used. Swimming C. volutator were caught in a Welsh estuary in the summer, but only rarely in the autumn and winter, and in both daylight and darkness. In simulated tidal conditions in the laboratory C. volutator from two sites in East Anglia never swam, while those from Wales swam whenever the substratum was immersed, in daylight and darkness, mostly on the ebb tide and in winter. The unnatural swimming in winter may have been stimulated by laboratory conditions, but the East Anglian amphipods were not so affected. The tidal swimming rhythm is different to east coast C. volutator which only swim at night. This difference may be related to the time of spring tides, when most swimming occurs. In Wales high water of spring tides may occur only in daylight in summer and nocturnal swimming may not be possible. The ebb tide swimming by C. volutator in Wales contrasts with the flood and ebb swimming of east coast amphipods and may reflect differences in their habitats. The former were collected close to the sea while the latter were 15 km up a narrow estuary and may represent a sub-population of amphipods with a disposition to swim early (on the flood tide) enabling them to colonise upstream habitats.

Zonation and activity patterns of two species of the genusPhaleria Latreille(Coleoptera Tenebrionidae) inhabiting an equatorial and a Mediterranean sandy beach

Two species, Phaleria prolixa Fairmaire and Phaleria bimaculata Linnaeus were compared. The first species lives on a Somalian beach with large tidal fluctuations, while the second inhabits a beach on the Tyrrhenian littoral of Italy where tidal excursions are negligible. For Ph. prolixa the data were collected in two different climatic seasons, the dry and the wet season. Instead for Ph. bimaculata the data refer to a 4 month survey. Zonations and activity patterns were obtained from the capture frequencies of directional cross and wall traps. Both species prefer the seaward part of the sandy beach with slight variations in the different seasons for Ph. prolixa. Both species are nocturnal but only Ph. prolixa, being largely tied to a tidal rhythm, shows activity even throughout the day.

External synchronizers of tidal activity rhythms in the prawns Penaeus indicus and P. monodon

Phasing of persistent circatidal rhythmicity to an artificial tidal cycle was assessed in the prawns Penaeus indicus Milne Edwards and P. monodon (Fabricius) collected from the Vellar estuary, South India, in the period between June and December 1984. Simulated 6 h cycles of 20 and 30‰ S, and 6 h cycles of 20° and 30°C induced a persistent tidal rhythmicity after 20 cycles. The imposed 6 h cycles of 25 and 30‰ S, and 25° and 30°C induced tidal rhythms after 30 cycles. In both cases, re-established tidal activity rhythms were evident for at least 48 h — higher activity occurring during the higher salinity and lower temperature phases of the simulated tidal cycles. Artificial tidal cycles of still water and running water synchronized the tidal rhythm after 20 cycles. Combined 30‰ S, 20°C, for 6 h and 20‰ S and 30°C for 6 h established a persistent tidal rhythm after 10 cycles, whereas wave action had no influence on tidal synchronization. The influence of possible interactions of tidal rhythms and in situ tidal variables on circatidal activity is discussed.

Comparative studies of tidal rhythms. VIII. A translocation experiment involving Circalunidian rhythms

One of the earliest experiments that provided support for the exogenous clock hypothesis was a translocation experiment involving fiddler crabs. The activity rhythm of a sample of crabs placed in constant conditions, abandoned (in a week's time) the phase of the tidal cycle to which the crabs had been exposed in nature, and the peaks attuned themselves to the approximate times of lunar nadir and zenith. The study reported in the present paper was an attempt to repeat this interesting and important finding. The effort at replication was unsuccessful. But other more recent findings of tide‐associated rhythms, such as splitting, uncoupling, and temporary arrhythmicity, were confirmed. And an “ultradian”; rhythm was discovered to exist in conjunction with a typical circalunidian frequency.

Effects of combined temperature and salinity on the entrainment of endogenous rhythms in the shore crabcarcinus maenas

Shore crabs (Carcinus maenas) were exposed in the laboratory to simultaneous, artificial tidal cycles of temperature and salinity. Cycles applied with high salinity coincident with low temperature, the normal pattern of such variables on the shore in summer, induced exogenous tidal rhythmicity at times of low salinity and re‐set endogenous circatidal rhythmicity. In subsequent constant conditions the endogenous circatidal rhythm persisted with maximum activity at “expected”; times of high salinity/low temperature. When the two variables were applied in tidal antiphase the dominant cycle of activity during treatment is an apparent tidal cycle driven by episodes of low salinity. In constant conditions after such treatment, however, a semi‐circatidal (6.2 h) pattern of activity was exhibited, suggesting that summer high tide characteristics of high salinity and low temperature applied in tidal antiphase entrain separate circatidal components of the crabs’ physiological clocks.

Rhythms in larval release of the sublittoral crab Neopanope sayi and the supralittoral crab Sesarma cinereum (Decapoda: Brachyura)

Ovigerous females of the subtidal xanthid crab Neopanope sayi (Smith) and the high intertidal grapsid crab Sesarma cinereum (Bosc) were collected during the summers of 1986 and 1987 in the Beaufort, North Carolina (USA), area and brought into the laboratory, where rhythms in larval release were monitored. When crabs with late-stage embryos were put under a 14 h light:10 h dark cycle in an otherwise constant-environment room, an apparent tidal rhythm in release of larvae was observed for both species, with N. sayi releasing near the time of day and night high tides, and S. cinereum releasing around the time of night high tides. The time of sunset relative to high tide was a complicating factor, since larval release for both species was often concentrated around sunset when evening high tides fell several hours before sunset. When a group of N. sayi and S. cinereum were brought into the laboratory and placed under constant lowlevel light for 5 d, the release rhythm of the population persisted, thus implying that the rhythm is endogenous. Larval release near the time of high tide and often at night is common among brachyurans living in tidal areas, regardless of specific adult habitat, suggesting a common functional advantage. Possibilities include transport of larvae from areas where predation and the likelihood of stranding and exposure to low-salinity waters are high, as well as a reduced probability of predation on adult females. Results of the present study suggest that the importance of release after darkness may increase with increasing tidal height of the adult.

Comparative studies of tidal rhythms. IV Spontaneous frequency changes and persistence in the locomotor rhythm of an intertidal crab

Continuous recordings of the locomotor activity of the intertidal grapsid crab Helice crassa in constant laboratory conditions were obtained from two individuals for periods in excess of three months. The records show that the strength of the tide‐related rhythm varies with time. On occasion the crabs are arrhythmic or only weakly rhythmic but clear rhythms are often spontaneously re‐established. Even after 3–6 months in the laboratory, clear rhythmicity is seen at times. Rhythms with periods varying from 6.5 h to 28 h were recorded. The relationship between the period of the overt rhythm and that of the underlying oscillatory system is considered.

Age and growth rate determinations of an intertidal bivalve, Phacosoma japonicum , using internal shell increments

A venerid bivalve Phacosoma japonicum (Reeve) occurring commonly in the Japanese coastal area preserves periodic growth lines in the shell cross-section. Long-term shell growth patterns of this species have been traced for many individuals on the intertidal flat of the Seto Inland Sea, west Japan. Sclerochronological analysis of these individuals and specimens collected monthly shows that several growth cessation marks within their shells are formed during the winter of each year prior to spawning. Hence the marks were used for age and growth rate determinations. As large individuals showed little shell growth for more than two years after the formation of 7 or 8 annual increments, this species probably has a lifespan of more than ten years. Shell growth patterns of this species based on annual increments can be accurately approximated by a von Bertalanffy curve. The number of microgrowth increments formed during a year tends to decrease with age, although it varies markedly among specimens of the same age. Furthermore, even in summer during rapid shell growth, the microgrowth increments do not represent daily and/or sub-daily tidal rhythms in many specimens. The results of this study and those by several authors strongly suggest that the annual increments are the key for age and growth rate determinations of both living and fossil bivalve species.

The effects of the reed,Phragmites australis (Trin.), on substratum grain-size distribution in a salt marsh

The effects of the reed,Phragmites australis (Trin.), growing in a brackish water lagoon, were studied in relation to the grain-size distribution of the substratum. At the salt marshes near the lagoon, the upper soils from the surface to a depth of 20 cm contained much silt-clay. These fine particles were found to be transferred from the river and fish ponds near the lagoon, and to be deposited when the tidal rhythm changed, that is, when the water current stopped. In addition, the fine particles, which were deposited on the bottom of the lagoon adjacent to the marshes, became resuspended as a result of wind-caused wave action, and then were transported and redeposited in the salt marshes at the flood tide. Since the reeds further reduced the water current caused by the waves and tide, the reeds were thought to promote redeposition of the resuspended matter. In other words, the reeds were considered to protect deposited and redeposited particles such as silt and clay from resuspension as a result of wave action by reducing the effects of waves and wind. These processes suggested that silt-clay will become abundant in the substratum of the salt marsh adjacent to the lagoon.

Entrainment of Tidal and Semilunar Rhythms by Artificial Moonlight Cycles

A marked feature of the larval release activity of the terrestrial crab Sesarma haematocheir is its synchronization with the time of high water. This activity occurs only at night, so that the pattern of the tidal rhythm recurs at semi-monthly intervals. When adult specimens from Seto (Okayama Prefecture) and Shima (Mie Prefecture) populations were brought from the field into 24-h light-dark conditions in spring, the larval release occurred at night, but the overall activity pattern gave no indication of a tidal component. On the contrary, under simulated moonlight cycles the timing of release was strongly coordinated and exhibited a well-defined tidal component arranged at semi-monthly intervals. The phase difference between the evoked tidal rhythms of the two populations of 4-5 h was about equal to the phase difference of the tidal cycles in their natural habitats. Synchronization of larval release with the artificial moonlight cycle required more than 40 days of exposure. In addition to entraining the tidal rhythm, artificial moonlight induced a semilunar rhythm in both populations. Entrainment could be achieved with exposure to moonlight for just a few days around the time of the full moon. In this paper, underlying mechanisms of the Sesarma larval release rhythm, which involves both tidal and semilunar components, are explained in terms of circadian oscillatory systems.

Comparative studies of tidal rhythms. VI. Several clocks govern the activity of two species of fiddler crabs

The tide‐associated persistent activity rhythms of the ocypod crabs, Uca pugnax and U. pugilator were observed in constant conditions, some for as long as three months. In some animals the twice/day peaks of activity were found to scan the day at significantly different rates from one another. Individual peaks in some animals split into two fragments. And at times, one peak would fade and then return, or vanish completely. These examples of the independence between tide‐related activity peaks have become the basis for a hypothesis that each peak is controlled by its own clock(s). The basic period of these clocks is “circalunidian”, with periods varying up to about 4–8% on either side of 24.8 hours.

Osmotic and ionic regulation in shore crabsCarcinus maenas inhabiting a tidal estuary

Shore crabsCarcinus maenas were exposed to salinities fluctuating according to the natural tidal rhythm. To this end they were maintained in net cages positioned in the estuarine waters of the river Elbe. The cages were lifted every hour, and between 8–12 specimens were analyzed for hemolymph concentrations of Na, K, Ca, Mg, and osmolality. The results obtained were compared with the respective data measured in external brackish water. In addition, the specific activity of Na−K-ATPase in a posterior gill was determined. Hemolymph Na and Mg as well as branchial Na−K-ATPase were also determined in crabs collected in the North Sea and the Baltic. The results show that inC. maenas living in salinities fluctuating with the tides by approx. 15‰ S, Na, K and Ca were hyperregulated, and Mg was effectively hyporegulated. The concentrations of all hemolymph ions and the activity of the Na−K-ATPase were kept constant over the whole tidal cycle. In Baltic crabs, Na was effectively hyperregulated and gill Na−K-ATPase was significantly elevated by a factor of ca 2 when compared with North Sea crabs. It is suggested that long-term hyperregulation of Na in constant salinities results from an increased number of Na−K-ATPase molecules which may change by synthesis or degradation following salinity stress. Constant hemolymph levels of hyperregulated Na in crabs inhabiting fluctuating brackish water are accomplished by activation of existing Na−K-ATPase by low Na and inhibition by higher ambient concentrations.

Oxygen consumption of two nearshore marine elasmobranchs, rhinobatos annulatus (Muller & Henle, 1841) and Myliobatus aquila (linnaeus, 1758)

1. 1. The oxygen consumption of two nearshore marine elasmobranchs, Rhinobatos annulatus and Myliobatus aguila, was studied under laboratory conditions. 2. 2. Nocturnal peaks in routine oxygen consumption of R. annulatus were observed, while the routine oxygen consumption of M. aquila showed nocturnal and diurnal peaks. 3. 3. The periodogram for R. annulatus suggested a circadian rhythm and for M. aquila a weak tidal rhythm. 4. 4. The specific mass exponents (dimension: μgO 2/g/hr) are temperature independent and range from −0.15 to −0.33 (common b: R. annulatus −0.18; M. aquila −0.25). 5. 5. Starving the elasmobranchs results in decreases in active, routine and standard oxygen consumption. 6. 6. The maximum rates of oxygen consumption of the two species induced by feeding were 1.42–2.25 and 1.16–4.30 times the routine value for elasmobranchs that have been starved for 40 hr and 162hr, respectively. 7. 7. Apparent SDA for both species showed some variation and ranged from 4.2 to 32.9% (mean: R. annulatus 17.3%; M. aquila 14.0%).

Tidal rhythms in activity in the intertidal gastropodPolinices incei (Philippi)

When removed into the laboratory, the intertidal snailPolinices incei, retains a tidal rhythm in activity for several days when maintained under conditions of constant light. There is, in addition, a gradual decline in activity following collection and a batch to batch effect of some note. When a 12∶12 light regime is maintained there is apparent also a c. 24 h rhythm in activity which may supercede the tidal one under some circumstances. The simplest explanation of the results is that there exist both tidal and diel rhythms. These results are compared with those observed by others for a variety of marine organisms, the adaptiveness of the behaviour pattern is discussed, and the implications of the work for further behavioural studies is explored.

Feeding and extracellular digestive rhythms in some intertidal bivalve molluscs

The tidal rhythms for changes in morphology, length, dry weight and protein content of the crystalline style are studied in two venerid clams,Meretrix meretrix andKatelysia opima and in a donacid clam,Donax cuneatus. In the two venerid clams the style is housed in a sac conjoined with midgut and there is a tidal rhythm of feeding and extracellular digestion involving a partial dissolution of the style in the ebb tide and reformation in flood tide. But in the donacid clam where the style sac is completely separated from midgut, no detectable changes in the style parameters are recorded during a tidal cycle. However, the rhythmicity in feeding activity is indicated, by the presence of ‘mudcap’ and food particles in the style during flood tide and their subsequent absence during ebb tide. Hence the tidal rhythm of feeding and digestion inDonax cuneatus may be without corresponding changes in the crystalline style. Also this study throws light on the mode of style dissolution.

Occurrence of lysozyme in the common cockle Cerastoderma edule and the effect of the tidal cycle on lysozyme activity

In 1983 a sample of cockles [Cerastoderma edule (L.)] was removed from the mid-tide level at Booterstown Strand, County Dublin, Ireland at 2-h intervals, for a period of 24 h. The gills, mantle and visceral mass tissues contained significant levels of lysozyme, with the gills containing the highest, weight-specific levels. A tidal rhythm of lysozyme activity in the gills, mantle and visceral mass was inversely related to the tidal cycle. The data were best described by a tidal curve shifted-5 hours out of phase, with maximum and minimum levels of activity occurring one hour after low and high tides, respectively. In marine bivalves, lysozyme may be involved in the extracellular digestion and absorption of bacteria during low tide. In this context the present use of bivalves as biological indicators of bacterial pollution is discussed.