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Burrowing was investigated in two Antarctic infaunal bivalve molluscs, Laternula elliptica and Yoldia eightsi, representing amongst the least and most active members of the class Bivalvia in the Southern Ocean. Burrowing rate was expressed via the Burrowing Rate Index (BRI=[3√wet weight/time to bury]×104), and produced values of 0.1–10.6 for L. elliptica and 8.8–49.8 for Y. eightsi. These compare with values ranging from 3 to 2,000 for N. American bivalves (mean=222, SE=42.6, n=81), and 200 to 2,200 for Hong Kong bivalves (mean=1,140, SE=346, n=6). Values for the Antarctic species are, therefore, low compared to warmer-water bivalves, and the values below 1 for large L. elliptica are the lowest on record by around ×5. There is no compensation of burrowing activity for low temperature in these species. The relative BRI values for L. elliptica and Y. eightsi reflect the differences in their mode of life, with the former being large, sedentary and suspension-feeding, and the latter being smaller, mobile, ploughing through the sediment and feeding on sediment-surface organic matter. Burrowing in L. elliptica is unexpected, because other members of the Laternulidae do not burrow. This ability is most probably a response to the regular disturbance of sediments in Antarctica by ice, and the strong selective advantage to being able to resume a protected position after disturbance. The burrowing cycle in L. elliptica is composed of three main phases: (1) foot extension and sediment penetration; (2) foot dilation to form an anchor; (3) the drawing down of the shell by contraction of the pedal retractor muscles. Burrowing in Y. eightsi also has three phases: (1) foot extension and penetration of the sediment (digging); (2) rocking movements in the upright position; (3) shell anchorage. In excess of burrowing activity, L. elliptica exhibits a unique suite of movements when exposed at the surface. These comprise levering, where the tips of the siphons are pressed against the sediment to lift the shell from the substratum, looping, where the siphons are extended and rotated and, in the process, translocate the whole animal across the sediment, and jetting, where water is ejected forcibly through the siphons while their tips are directed towards the sediment, lifting part or all of the animal clear of the substratum. In the field, following exhumation by icebergs, these activities serve to place the animal in a favourable position for reburial, which is a clear advantage in disturbed polar environments where predatory nemerteans and asteroids are abundant.

Observations of a New Zealand harbour beach revealed that aggregative feeding behaviour was common in the buccinid gastropod Cominella glandiformis (Reeve, 1847). The majority of such aggregations are associated with either the tellinid bivalve Macomona liliana (Iredale, 1915) or the venerid cockle Austrovenus stutchburyi (Wood, 1828). Marking experiments indicate that aggregations persist for one tidal cycle. This information, together with the density of aggregations associated with each ‘prey’ species allows the calculation of rate of predation by Cominella glandiformis and of the mortality of M. liliana and A. stutchburyi at different stations on the beach. Averaged over spring periods, when predation and mortality are reduced, and summer, the calculated rates suggest that between 2 to 16% of M. liliana and 3 to 9% of A. stutchburyi fall prey to Cominella each year. The majority of bivalves at the centre of aggregations appeared to be tightly shut and undamaged, suggesting that the gastropods are predators attacking live prey, although late arrivals may be attracted as scavengers by leaking body fluids. Aggregated feeding may provide the gastropod with both competitive and metabolic benefits.

verge in scores on dead animal remains, and may also be active carnivores, thrusting the long proboscis through the narrow umbonal fissures of Chione and other bivalves”, as the universal scavenger of mud Members of the buccinid gastropod genus Cominella are abundant components of the intertidal fauna of many Australian and New Zealand sheltered beaches where they commonly form aggregations around food items1,2,3. For New Zealand, Morton & Miller2 desJ. Moll. Stud. (2000), 66, 419–422 © The Malacological Society of London 2000

Rates of sediment ejection were recorded from 20 burrows of the echiuran worm Maxmuelleria lankesteri at monthly intervals over a 13-month period. Environmental parameters, numbers of ejecta mounds and the spatial persistence of burrows were also monitored. All 20 marked burrows retained signs of occupation over the study year. Sediment turnover was recorded in all months, with no cessation of activity over the winter. Volumes of sediment expelled during each 2-day measurement period were extremely variable, up to a maximum of ∼97 g dry weight burrow −1 day −1 . Over the year, the mean ejection rate from 20 burrows was 7.53±5.24 S.D. g burrow −1 day −1 , with peaks of activity recorded in December and April. The superficial sediment (on which M. lankesteri feeds) was very rich in organic matter, with monthly values of 11.7–16.7% sediment dry weight. Thermally labile organic matter, determined by combustion at 250°C, comprised 16.7–71.4% of the total organic content, with highest and lowest values in April and August, respectively. There was no significant correlation between monthly sediment ejection rate and total sediment organic content, but a highly significant correlation was found between ejection rate and the percentage of labile material in the sediment organic matter. Ejection rate remained constant at labile fractions below ∼50%, but increased sharply above this threshold. Topographic relief and numbers of feeding traces at the site suggested that activity level was lowest in late summer (August–September). Burrows appeared to be static, and the animals sedentary in habit. Individual ejecta mounds could persist for up to 15 months. There was no evidence that the worms alternated the functions of the feeding and ejection openings of their burrows. This burrow stasis contrasts with the pattern seen in some deep-sea echiurans, a behavioural difference probably determined by the nutritional status of the respective habitats.

Tail-flip escape trajectories of the brown shrimp Crangon crangon have been investigated in response to a natural predator, the cod Gadus morhua, and an artificial stimulus. Shrimps escaped by rolling to their left or right during the initial tail-flip of a response, and thereafter swam on their side. As a result of the laterally directed first tail-flip, initial escape angles always lay between 75° and 156° with respect to the (pre-escape) longitudinal axis (anterior=0°) of the shrimp. Symmetrical attacks from either head-on or tail-on produced escapes to the shrimp’s left or right in equal proportions, although a contralateral bias did occur if the shrimp experienced a looming object from one side before a symmetrical attack was applied. Lateral attacks produced a significantly greater proportion of contralateral responses than ipsilateral ones. Empirical and theoretical analyses indicate that the initial escape direction is influenced by an interaction between the range of first tail-flip escape angles that the shrimp is capable of performing and the risk of being intercepted by a predator during the initial stage of an escape. Thus, the unpredictability (‘protean behaviour’) of the response may be affected by the conditions of the interaction. Subsequent tail-flips of an escape usually directed the response away from the stimulus, but sometimes escapes were instead steered to the side of the stimulus and then behind it. The probability of each type of escape occurring changed with attack direction. The elements of protean behaviour that have been identified in both the initial and subsequent stages of the escape may prevent predators from learning a fixed pattern of response, but a trade-off occurs when escape trajectories infringe upon zones of high capture risk.

Buried individuals of the bivalve Donax vittatus (Bivalvia: Donacidae) respond to change in incident light intensity by adjusting their position in the sediment. Video recordings of activity in aquarium tanks in natural daylight revealed that individuals responded to shading by moving upwards, causing some to partially emerge from the sand. Subsequent removal of the shading stimulated reburial to the normal position. Recordings in laboratory aquaria show similar upward movement and partial emergence occurring when illumination in the visible range is switched off. Upward movement and partial emergence of D. vittatus has also been observed to take place prior to spawning.

This paper summarizes the available information on the distribution and biology of Maxmuelleria lankesteri. This large echiuran was described almost a century ago but its local abundance and potential importance as a bioturbator were recognized only recently. The species is widespread around the British and Irish coasts, most commonly in fine muds. A deep-burrowing, nocturnal deposit feeder, M. lankesteri is unlikely to be seen by divers, but its presence can be deduced from the form of ejecta mounds and proboscis tracks. The worms are very difficult to capture intact. Body size in a sample from Loch Sween, Argyll, was approximately normally distributed. Very small individuals are rarely found. Developing oocytes were found in the coelom over the spring and summer. Mature eggs accumulate in the gonoducts, with maximum loads found from October to December, possibly indicating a single annual spawning during the winter. Despite intensive examination of a large number of adult females, no dwarf males were found, leaving open the question of their existence. The large, yolky eggs indicate lecithotrophy or direct development. Larval stages have not been recognized. The apparent scarcity of developmental stages and of very small adults suggests that recruitment may be sparse and infrequent.

Bioturbation by the deep-burrowing echiuran Maxmuelleria lankesteri was studied in Loch Sween, Scotland. Results were used to evaluate the animal's likely effects on the movement of radionuclides in sediments of the NE Irish Sea, where the species is also common. Individual burrow openings were monitored by video for up to 23 days. There was no consistent relationship between the frequencies of sediment intake and ejection, an anomaly which suggests that the burrow of M. lankesteri has two surface openings rather than one, as believed previously. Sediment output was measured by changes in ejecta mound volume and by direct collection of vented material. Both methods gave a value of approximately 13 g dry matter · day−1, of which about 0.8 g (6%) was faecal matter. The remainder consisted of non-faecal fluidized sediment, for which concentrations of 234Th suggested a surface origin. There were no significant differences in particle size composition between burrow ejecta and ambient surface sediment. Sediment ingestion rate was not directly measurable, but was estimated at about 1.7 g · day −1 using a model derived from studies of other marine deposit feeders. Bioturbation by M. lankesteri seems to result in a short-term redistribution of material (about 13 g · day−1) on the sediment surface, with about 0.9 g · day−1 incorporated into the burrow lining as faecal pellets. In the NE Irish Sea, burrows will act as sinks for surface-derived radionuclides and there is probably little return of deeply-buried material to the sediment surface.

Fishes were sampled by seine and beam trawl over tidal and diel cycles on a sandy beach on the west coast of Scotland in June and August. Species composition of the catches of the 2 gear types differed. There was a significant positive relationship between depth (0 to 5 m) and species richness but a few species were restricted to depths of

The burrow morphology of the echiuran worm Maxmuelleria lankesteri (Herdman) was investigated in situ using a resin casting technique. Work was carried out in Lochs Sween and Creran on the west coast of Scotland in predominantly fine mud sediments. Burrow casts typically had only 1 opening, although there is evidence to suggest that a second opening may exist. In 58% of burrows, the opening, which was small and funnel-shaped, was associated with a surface mound reaching up to 20 cm in height. The tunnel below the burrow opening, the ‘neck’, was narrow and circular in transverse section with a smooth wall, possibly due to the action of the mucus-laden proboscis which emerges during feeding. The maximum burrow depth recorded was 80 cm and tunnel orientation became more horizontal with increasing depth. In some larger burrows, the tunnel began to orientate upwards towards its end. Below the neck, the tunnel was much wider but had a sub-circular transverse section. The burrows had distinct striations on the w...

The orientation of tail-flip escape swimming in a range of adult decapod and mysid crustaceans is reviewed. In mechanical terms, tail-flip swimming constitutes unsteady locomotion in which a single ‘appendage’, the abdomen, produces thrust by a combination of a rowing action and a final ‘squeeze’ force when the abdomen presses against the cephalothorax. In small crustaceans, a symmetrical ‘jack-knife’ tail-flip is more typical. Tail-flip flexion is controlled by two giant-fibre pathways, and also by a non-giant-neuronal network. The direction of thrust in the sagittal plane, and hence the elevation, translation and rotation of the tail-flip are dependent upon the point of stimulation and on the giant-fibre pathway activated. The laterality of the stimulus also affects the orientation of swimming, which is directed away from the point of stimulation. In large decapods such as the lobstersNephrops norvegicusandJasus lalandiisteering is produced by asym-metrical movements of various abdominal appendages, and by rotation of the abdomen about the cephalothorax. In slipper lobsters the flattened antennae provide steering surfaces. In smaller decapods, such as the brown shrimpCrangon crangon, and in mysids, such asPraunus flexuosus, steering is effected by a rapid rotation of the whole body about its longitudinal axis during the initial stages of tail-flip flexion. The effectiveness of tail-flip swimming is considered in the context of predator-prey interactions under natural conditions and in relation to artificial threats from fishing gear.

Underwater television with time lapse video recording was used to record in situ activity of the tellinacean bivalve Donax vittatus on West Sands Beach, St Andrews on the east coast of Scotland. Individuals emerged from the sand most frequently immediately before and after low water, when wave action in shallow water caused disturbance of the sediment. During this period, emergence was most frequently followed by ‘leaping’ and/or transport by waveinduced currents. Emergence or partial emergence during mid-tide periods was more frequently followed by surface or subsurface crawling. These activities resulted in a redistribution of the population which affected up to 44% of individuals during each tidal cycle. In all cases, reburial followed quickly. The number of emergence, ‘leaping’, and reburial events in each 30 min time interval showed a positive, and the number of crawling events a weak negative, correlation with the degree of disturbance by wave action. The separate inhalant and exhalant siphons, used...

Rates of predation on 0-group plaice, Pleuronectes platessa. in aquaria were compared under four different combinations of conditions to test the hypothesis that the presence of sand in which they may bury affords a refuge from predators. The effect of light and darkness on predation rate was also examined, Two crustaceans, the shrimp, Crangon crangon, and the portunid crab, Liocarcinus holatus, and two fishes, cod, Gadus morhua, and pollack, Pollachius pollachius, were used as predators. Predaton rates were significantly higher in the dark for all predators except pollack. Predation rates in the absence of sand were signifcantly greater only for pollack. The results suggest that predation rates on plaice during their juvenile nursery stage on sandy beaches will be significantly greater during darkness than during the day. Burying in sand appears to provide only a partial refuge from predation, perhaps because natural predators have evolved effective methods of foraging for buried prey.

Genetic variation at eight polymorphic enzyme loci was investigated in 13 populations of the scallop Pecten maximus (L.) from a number of sites in Scotland, UK and Brittany, France. Two of the populations had initially been transplanted, as spat, to Brittany from Scottish and Irish collection sites. In common with other studies of marine bivalves, an overall deficiency of heterozygotes was observed, but genotype frequencies of transplanted populations were generally in agreement with the Hardy-Weinberg model indicating little post-transplant selection. There was high genetic similarity among all the populations surveyed and no overall differences between the Scottish and Brittany samples. The results are discussed in relation to contrasting evidence, derived from studies on the reproductive cycle of P. maximus and the genetics of Aequipecten (Chlamys) opercularis (L.), which suggests that the Scottish and Brittany scallop populations are, nevertheless, genetically distinct.

The seasonal reproductive and storage cycles of scallops, Pecten maximus (L.), transplanted as juveniles into the Bay of St. Brieuc, Brittany, from Scotland and from the Bay of Brest, were compared with the cycles of similar scallops in their areas of origin and with those of native St. Brieuc scallops. Major features of the reproductive cycle of the transplanted scallops remained unchanged from those of their areas of origin, indicating that genetic factors played a major role in controlling this cycle. In contrast, environmental factors apparently played the dominant role in determining events in the storage cycle. The results provide strong evidence, based on reproductive physiology, for the existence of partially genetically separated stocks within the European distribution of this scallop.

The burial mechanism ofCrangon crangonwas examined in detail using high-speed video-recording equipment. Four stages of burial were identified which were associated with three modes of burial. As the mode of burial changed, a change in the angle of substratum penetration was also noted.The effect of particle size on the burying ability of three discrete size classes of shrimp was examined using both artificially graded and naturally occurring sediments. Particle size was found to be a major influencing factor on the degree of burial achieved by C.crangon, but no significant effect of shrimp size on burying ability was found over the size range tested.

Surface activity of the deep-burrowing echiuran Maxmuelleria lankesteri (Herdman) was observed in Loch Sween, Argyll (Scotland, UK) using underwater television. Activity, consisting of proboscis emergence and sediment venting, was observed in all seasons. Proboscis emergence was strictly nocturnal, occurring on average on one night in two. Emergence occurred at irregular intervals during the night, with no consistent rhythmicity. Feeding extensions of the proboscis usually lasted about 10 min, but were often curtailed by accidental contact with ophiuroids or other epifauna. The extending proboscis skims off the top layer of sediment, then rapidly pulls the collected material into the burrow. Animals showed a capacity to select material from particular areas within the feeding radius. The feeding strategy may be to accumulate several loads of sediment in the burrow, then selectively ingest material over the following day. Large volumes of sediment were often vented from burrows, either in a fine suspension...

Forty-three species of fishes and 16 species of larger crustaceans were caught by trawl and seine during a 4 yr study on a sandy beach on the west coast of Scotland. There were considerable differences in the species composition of the trawl and seine catches such that neither alone provided an adequate description of the sampled cornnlunity. Approximately monthly s a m p h g demonstrated a clear seasonal cycle in abundance and species composition. A few species were resident on the beach all year round; the majority were only present from spring to autumn. Increases in both numbers and species were caused mainly by the recruitment of young of the year individuals whose numbers subsequently declined rapidly probably due to a combination of predation and emigration. There were marked differences in both species composition and abundance between years. Annual cycles in species richness and abundance closely paralleled those of temperature and sahnity. It is suggested that the cycles result mainly from recruitment and mortality rather than from immigration and emigration in response to physical factors.

Living specimens of Terebratulina retusa from the Firth of Lorn, Scotland, were surgically damaged by drilling 2 mm diameter holes or narrow slits one cm long in the anterior portion of one valve, by bevelling the anterior margin of both valves, or by amputation of the anterior third of one valve. These injuries to the shell and mantle simulated the type of repaired shell damage seen in Paleozoic species, i.e., scalloped, divoted, cleft, and embayed valves. Less than ten percent of the 200 damaged specimens survived until the 25th week after surgery. Specimens of T. retusa showed the ability to repair drill holes, slits, and bevelled anterior shell regions, but not the most severe damage, i.e., amputations of the anterior third of one valve. Shell‐repair was initiated in the fourth week after surgery by the development of a membrane across the wound. The development of caeca in the new shell layer secreted to plug the drill holes became apparent by the eighth week. The punctate pattern was complete in the...

Many infaunal marine bivalve molluscs have the capacity to move over the sediment surface by 'creeping' or 'leaping' movements, either spontaneously or in response to predators or physical disturbance.1 The evolution of a deep-burrowing habit in some bivalve families has been accompanied by loss of the capacity for surface movement and for reburial,2-3 since burrowing to greater depths provides effective protection from both natural disturbance and most predators. It is unusual, therefore, to discover that one normally deeply burrowing species, living in the cold waters of Antarctica, has a capacity for surface movement and by a different method to any previously described for an infaunal bivalve. Laternula elliptica (King and Broderip) (Anomalodesmata, Laternulidae) is among the most abundant and ubiquitous infaunal bivalves in shallow waters around the Antarctic continent, reaching population densities of up to 86 m"2 in a variety of soft sediment types.4 Adult individuals of up to 90 mm shell length may be 12-13 years old.5 L. elliptica show many features in common with other deepburrowing genera such as Mya, Lutraria or Xirfaea including long, muscular, fused and periostracumcovered siphons that are capable of considerable extension; extensively-fused mantle edges that firmly seal the mantle cavity except for siphonal and pedal apertures; a relatively small foot; and a shell that is emarginated posteriorly and cannot contain all of the soft tissues. Unlike such well-studied temperate bivalves and other species of Laternula from lower latitudes,*-7 L. elliptica retain throughout their life the ability to re-burrow if uncovered from the sediment, and also exhibit a hitherto undescribed mode of movement on the sediment surface, following dislodgement, powered by contractions of the muscles of the siphons and mantle. The observations reported here were made at the Dunstaffnage Marine Laboratory (DML) on a group of 14 L. elliptica (shell lengths ranging 44.6-78.0 mm). These were the survivors of a larger group collected near the British Antarctic Survey (BAS) base at Signy Island, Antarctica by one of us (MCR) during the austral summer of 1994-95, and subsequently retained at c 0°C, without sediment, in the marine aquarium of BAS, Cambridge for observations on their energy metabolism. At DML, small groups (

Antarctic anemones of the genus Halcampoides inhabit low intertidal and shallow subtidal zones. They readily burrow into soft sediments following disturbance. The process of re-burying was recorded using time-lapse video in the aquarium of the British Antarctic Survey with specimens of a species collected from the shallow sublittoral (1 m depth) at Signy Island. Penetration of the sediment takes place by a similar mechanism to that employed by burrowing anemones such as Peachia hastata from lower latitudes. Penetration initially is brought about by peristaltic contractions that involve only the modified base, or physa. Later, as the column becomes buried, the peristaltic contractions start in the upper part of the scapus and pass down the column before extending the physa. At this stage penetration is aided by contractions of the longitudinal muscles that draw the column down into the sediment. At 0 degrees C the frequency of initiation of peristaltic contractions down the column, and of contractions of the longitudinal muscles are on average1.6 and4.0 times slower, respectively, compared with those of Peachia hastata from Scotland, recorded at approximately 11-14 degrees C. Q(10) values calculated from these data are in the range 1.4-3.0, and thus provide little evidence supporting any evolutionary acclimation of the processes involved in burrowing has occurred in Halcampoides from the Antarctic, although the data are limited.

Tail-flip escape swimming by the brown shrimp Crangon crangon has been investigated across a range of body lengths (11–69 mm) using high-speed video analysis. This has revealed several novel aspects of the tail-flip mechanism when compared with that of other decapod crustaceans that have been studied. (i) The pattern of body flexion in C. crangon produces movement of the cephalothorax as well as the abdomen about the centre of mass. (ii) Shrimps form a ‘head-fan’ with their antennal scales, in addition to the tail-fan formed by their uropods, apparently for generating thrust during tail-flips. (iii) Shrimps typically swim on their side rather than in an upright body position. It is suggested that these features may be interlinked and derive from habitat specialisation. The kinematic properties of tail-flips were found to vary with shrimp size. As shrimp body length increased, the rate of body flexion and re-extension decreased whilst the duration of tail-flips increased. Mean (and maximum) velocity estimates ranged between 0.4 m s−1 (0.7 m s−1) and 1.1 m s−1 (1.8 m s−1) for shrimps of different sizes. The combined effects of escape behaviour and size-dependent variability in tail-flip kinematics will have important implications with regard to predation risk.

Oxygen consumption and ammonia excretion rates were assessed for Terebratulina retusa (L.) held under 3 different regimes of temperature and food availability. These were: 5.6ˆC, no food (cold, starved); 5.8ˆC, food present (cold, fed) and 10.7ˆC food present (warm, fed), which simulated winter conditions, summer conditions and an intermediate treatment. Regressions of oxygen consumption on ash‐free dry weight (AFDW) had slopes which were not significantly different from each other and ranged from 0.953 to 0.999. A common slope of 0.976 was calculated and intercepts based on the common slope used to compare oxygen consumption in each treatment. The rise from cold, starved conditions to warm, fed was 24.5 per cent and this was significant (P 0.05) but the cold, fed result was 12.6 per cent higher than cold, starved. Therefore feeding and temperature probably account for equivalent proportions of the rise in metabolism from winter to summer. Ammonia produ...

Ash-free-dry-weight determinations for a representative range of living brachiopod genera have revealed that a consistently high proportion of total organic mass is contained within the shell, partly as the organic matrix for biomineralisation and partly as minute extensions of the mantle tissues (caeca) housed within hollow endopunctae permeating the shell. On average 40% to 50% of the total organic mass of both articulate and inarticulate brachiopods is situated within the shell. This is true even for a rhynchonellid brachiopod which does not possess endopunctae, but which has a more dense protein matrix in its shell. The effectively hidden constituent of brachiopod tissue mass which is included in this component has often been overlooked, and as a result total metabolic tissue mass has been underestimated. This throws into question some previous interpretations of brachiopod respiratory and metabolic data.The oxygen consumption rates of several living brachiopods have been measured, and when respiring tissue in caeca in the shell is taken into consideration, it is clear that brachiopod metabolic rates are low when compared with other marine invertebrates (e.g. between 10% and 50% of the oxygen uptake of comparable gastropods and bivalve molluscs held in similar conditions). This low rate cannot be attributed to a slower pumping rate by the brachiopod lophophore, as has been suggested, because the rate of water movement is comparable to that across the bivalve gill.Nitrogen excretion rates have also been measured for a few living brachiopods, allowing a comparison with rates of oxygen consumption and providing an indication of the metabolic substrates used. These data on oxygen: nitrogen ratios suggest that one Antarctic brachiopod utilises exclusively protein as a metabolic substrate, while a temperate latitude species uses mainly protein during winter but lipids and carbohydrates during summer months. Histological observations, particularly of Terebratulina retusa from temperate waters, show that a specialised tissue layer in the brachiopod outer mantle epithelium proximal to the shell may be the site of storage of the protein that is metabolised during winter, and of carbohydrate mobilised during gonadal development in summer. The caeca have also been suggested as sites of storage of metabolites, and the possible relationships between these areas of mantle are discussed. It seems that the ability to store nutrients in the mantle, combined with flexibility of substrate utilisation and an inherently low metabolic rate, have been important factors in brachiopod evolution.

The total ATP-content of representatives of 23 bivalve families was found to vary from 1.26–0.26 % of the dry tissue weight, with the dry tissue containing about 40 % carbon. Representatives from certain families consistently had more than average and others less than average ATP values, and there were greater differences between species from different families than between closely related species. Variations in the oxygen uptake of whole animals accounted for little of the observed variation in ATP-content. The ATP-content of individual tissues from the same individual showed wide variation, as did that of the same tissue from different species. The highest values of ATP were found in muscle tissues. High maintained levels of ATP were associated with the ability of the species to use energy rapidly for short periods, for example, in escape responses.

SynopsisEstimates of the rates of secondary production by the individual macrofaunal invertebrates of two Indian beaches are presented and these are combined to give an estimate of the energy flow through the macrobenthos of the two beaches. The production by individual species and by the macrofauna as a whole is compared with that of other tropical, and of temperate beaches, and it is concluded that a similar biomass in the tropical beaches produces a rate of turnover of biomass some ten times that of the temperate beaches. Values of production to biomass ratios (P/B) and of elimination to biomass ratios (E/B) for the invertebrates of sandy substrata in various geographical areas are reviewed and the use of these ratios in comparisons of productivity, and their relationship to mortality and longevity are discussed.

Aquarium observations of naticid gastropods from Hong Kong show that different species attack their bivalve prey in different ways. Natica gualteriana and Glossaulax didyma appeared always to use conventional modes of boring, i.e., through one shell valve, before consuming the prey, but some larger prey of C. didyma with incomplete borings were consumed after having apparently suffocated before boring was complete. In contrast, Polinices tumidus prey may be side-bored, edge-bored (i.e., through the commisure of the valves) or suffocated and consumed without boring. The frequency of each of these modes of attack vary with different prey species. Non-boring predation, in aquarium experiments, accounted for 14.7–54.9% of attacks with different species of prey. Suffocated prey were found to be enwrapped in a thick, viscous coat of mucus, which in partially consumed prey showed a round hole overlying the ventral shell gape marking the entrance hole made by the proboscis. The observations reveal considerable flexibility in predation behaviour in this tropical naticid and have important implications in the interpretation of naticid predation rates in recent and fossil dead shell assemblages.

The acute oxygen consumption of Donax vittatus (da Costa) freshly collected at different times from a beach at Barrassie, Ayrshire, Scotland, has been measured at different temperatures. The logarithmic relationship between oxygen consumption and body weight showed a significant difference on only one occasion, and a common regression coefficient (b) of 0.865 could be used for regressions of oxygen consumption on weight. Over the temperature range 2.9–20 °C oxygen consumption rose with temperature. There was a linear decline of Q10 with temperature in the range 2.9 –20 °C. Differences in values of the constant (a) in the regression equation suggest that there is some acclimation to temperature, resulting in rotation of the rate/temperature curve counterclockwise for warm-acclimated animals, and a reduction of Q10 in cold-acclimated animals. The differences in oxygen consumption which result are small and appear to have little practical significance. High levels of metabolically-inactive materials such as stored glycogen reserves lead to a reduction in the weight-specific oxygen consumption. Spawning animals show an increased oxygen consumption.

Experiments in the mass culture of Phneodactylum using 15-L cultures, with inorganic fertilizers or sewage effluent as a nutrient source, are described. Following inoculation, growth may start immediately or after a short lag. A logarithmic growth phase is followed by a period of constant population density or by an immediate decline. Growth rate in the logarithmic phase varied from 0.25 division/day in winter to >l division/day in summer. Purified sewage effluent, with or without salinity adjustment, is at least as good as inorganic fertilizers as a source of nutrients for the growth of PhaeoductyZum. INTRODUCTION purified sewage effluent reduced the saSome of the problems encountered in linity of the culture in the jars to which it the mass culture of marine plankton algae was added, the salinity in some cases was (Ansell, et al. 1963) cannot be investigated adjusted by the addition of a mixture of easily in large tank cultures, partly because NaCl, MgCla, NazSOJ, CaClz, KCl, and of the difficulty in controlling environmenNaIICOR in the proportions recommended tal conditions sufficiently accurately, and by Harvey ( 1955) for the preparation of partly because the setting up of a largeartificial sea water. Additions of sewage scale tank culture is a time-consuming opeffluent were made to give as near as poseration. Investigation of some problems sible 0.8 mg P/L. h as therefore been carried out using Cell counts, determinations of inorganic smaller scale outdoor cultures, and this panitrogen and phosphorus fractions in the per outlines the work carried out in this medium, and chlorophyll content determiway. nations were carried out by the methods described in part II of the present series MATERIAL AND METHODS of papers (Ansell, et al. 1963). The experiments were conducted using We gratefully acknowledge the co-oper15 L of culture in battery jars of 20-L total ation received from Mr C. L. Bennett, capacity, which were placed on the roof of Superintendent of Broadstone Sewage PuPoole Electricity Generating Station, As in rification Works* previous series (Raymont and Adams 1958; Ansell, et al. 1963), flue gas from the staRESULTS tion boilers, or “pure” carbon dioxide from The general conditions prevailing in the cylinders was used to reduce the pH as series of experiments to be described are required. No attempts were made to conshown in Table 1. Series xiv-xvi, xviii, xxi, trol conditions of temperature and light and xxixa used normal nutrient additions; which therefore showed their usual diurnal and seasonal rhythms. in series xxviii, xxx, xxxii, and xxxiv puriNutrient additions were usually designed fied sewage effluent provided the source to give 0.8 mg P/L and 6.0 mg N/L (25.8 of nutrients, except in control jars where the normal nutrients were used. pg-at. P/L and 428.5 pg-at. N/L), using The results in general confirm earlier ammonium sulphate and disodium hydrogen phosphate as fertilizers. In experiments observations made on the growth of Phaeodactyluna in outdoor battery jar cultures where purified sewage effluent was used as ( Raymont and Adams 1958). The rates nutrient source, the effluent was collected of growth obtained are summarized in Tafrom Broadstone Sewage works. Since such ble 2.

This account of the boring mechanisms of those bivalve groups which bore mainly by mechanical means attempts to show partly by reference to published accounts of boring and partly from our own recent observations of certain characteristics of the boring process in the Pholadidae and Petricolidae, that in contrast to the movements of burrowing forms from which originally all the boring movements derive, the process of boring makes few demands on the hydrodynamic system of the bivalve. The characteristics of the boring process are closely related to the movements in modern forms having epifaunal or infaunal habits, supporting the suggestions of Yonge (1963) concerning the origin of this habit in the Bivalvia. In all groups in which boringis mechanical, the shell forms the boring tool. However, in those groups in which boring has its origin in the epifaunal habit, the major force applied to the shell in abrading the burrow isprovided by contractions of the pedal or byssal retractor muscles. In the Adesmacea alone, where boring has been derived from a deep burrowing habit, the adductor muscles provide the major force in abrasion, and the basic digging cycle has become specialized by the addition of the rocking action of the valves which succeeds retraction. In the former group the ligament is retained and provides the strong outward force with which the shell is held against the wall of the burrow. In the latter group, the ligament is reduced, allowing the valves to rock, but here the reciprocal action of the adductors allows the valves to diverge anteriorly as the large posterior retractor muscle contracts. In the more specialized species, water pressure plays a minor role, the maximum pressures recorded being associated with actions subordinate to those involved primarily in abrasion, such as rotation in the burrow or expulsion of debris from the burrow aspseudofeces. The least specialized borers, such as Petricola, resemble burrowing forms in the importance of the hydrodynamic role of the body fluids. In all groups there is a tendency for hypertrophy to take place in the muscles which produce the main boring effect, and for their action to be applied with maximum mechanical advantage against a fulcrum provided in most cases by the foot.

The functional morphology of twelve British species of the Veneridae is described. The systematic position of Mysia undata and evolution within the Veneracea are discussed.Structurally, the members of the family Veneridae show a lack of special adaptations. The ability to move horizontally as well as ventrally in soft substrata is retained; the pedal gape is large and the foot well developed. The siphons are relatively short and fused. The food-collecting mechanisms of the mantle cavity are largely unspecialized and function in maintaining a considerable flow of water, and retaining as much as possible of the suspended material. Members of the Veneridae show a considerable uniformity of structure, but trends of evolutionary change may be distinguished. The genera Gafrarium and Callista are least specialized. The genus Dosinia has evolved along an independent line and is specialized by the possession of a stream-lined, circular shell, deep lunule, and greatly elongated siphons, for a relatively deep-burrowing habit. Within the superfamily Veneracea major lines of adaptive evolution have given rise to the rock-boring Petricolidae and the deep-burrowing Glaucomyidae, and the genera Venerupis and Irus show affinities with both these families.

Changes in the body weight and composition of Tellina tenuis exposed to enriched sea water contained in large experimental tanks were followed in two experiments in 1965 and 1966. In both years, following enrichment, there was a rapid increase in body weight, which did not occur in animals in non-enriched tanks. The increase was reflected in changes in carbohydrate, lipid and protein, and increased storage of reserves in response to increased phytoplankton abundance. Changes in body weight of animals of the 5 + year group for the period of the 1966 experiment have been calculated and estimates made of the contribution to total production represented by growth, gonadal development, and storage of reserves.

Characteristics of the growth of PhaeodactyZum in culture in fertilized sea water in 1,000-L concrete tanks are dcscrihed. Successful experiments showed a constant pattern of events as follows: 1) active growth of PhaeocZnctyZum, 2) reduction in growth rate of Phaeodnctylum, 3 ) period of constant cell density, or rapid decline, 4 ) rcgcneration period, and, 5) second period of active growth, Growth of Phaeodactylum shows seasonal variation, but final population density reached is more or less constant. N and P utilization follow parallel courses, the mean ratio of N:P uptake during the 1st growth period bdng 6.5 2 0.44: I. During growth, inorganic P is incorporated in the cells as particulate organic P. Following dcclinc of PhaeocZactyZum dissolved organic P incrcascs, and later, inorganic P is regencratcd and may be reutilized during the 2nd growth phase. Decline of Phneodactylum is normally associated with increase of the heterotroph Mows. Thcrc was a close relationship bctwecn peak numbers of Mows and the number of Phaeotlactylum in the previous peak. The second growth phase consisted either of one or more chlorophycean flagcllatcs, or of Phaeoductylum. Estimates of production based on 02 bottle exposures, change in inorganic P, change in pH, and change in packed ccl1 volume agree closely, although initial uptake of P may bc excessive. Estimates from change in inorganic P indicate a seasonal variation in the rate of organic production of up to 2.2 gC/m”/24 hr in March, 4.9 gC/m2/24 hr in May-August, and 2.0 gC/m”/24 hr in October, November. For Tetruselmis production rates up to 5.2 gC/m2/24 hr were recorded. The efficiency of utilization of solar energy for Phaeoductykm culture ranged from 3.0 to 4.4% with a mean for 5 cstimatcs of 3.7%. For Tetraselmis values of 1.0-1.3s wcrc obtained.

Burrowing in Cardium echinatum, Laevicardium crassum and Cardium edule involves similar integrated cyclic movements, in which the active stage of downward movement is that of contraction of the pedal retractor muscles. Final position in the sand is reached only after several repetitions of the digging cycle comprised in a digging period. Digging cycles in the three species differ in the timing of the various stages. The species also differ in the number of cycles comprised in a digging period. These differences may be related to shell form. Recovery from deep burial occurs by similar cyclic movements, but modifications in anchorage and in the time and duration of the forces acting on the shell cause upward movement. The stage of protraction and straightening of the foot is the active stage of recovery. Leaping in C. echinatum and in L. crassum involves also cyclic movements, the leaping cycle, and occurs in response to starfish contact. The species differ in the number of repetitions comprising a single response and in the duration of various stages of the cycle. In burrowing, recovery and leaping succeeding cycles in a single period occupy progressively longer time intervals.

Summary Two individuals of the stenoglossan gastropod Bullia melanoides were found carrying egg capsules. In one, 33 capsules contained up to four early embryos; in the other, three capsules remained attached each containing one or two fully formed miniature adults. This species exhibits a form of brood protection in which the expanded foot is folded around the egg capsules to form a tubular brood pouch, and this habit is associated with the animals' occurrence on disturbed surf beaches on the tropical west coast of India.

The seasonal changes in the body weight and composition of Tellina tenuis from Kames Bay, Millport, and Firemore Bay, Loch Ewe, have been studied during 1965–1966. The composition of an animal of standard size was calculated for each sampling date to give information on seasonal changes independent of shell growth. Increase in body weight took place rapidly in both localities in early summer as the gonad developed and reserves were built up. Spawning resulted in a fall in body weight in June in both localities, and this was followed in Kames Bay by fluctuations in body weight and in Firemore Bay by a steady rise in body weight. Glycogen forms the major reserve in the body, accounting for about 90% of the total carbohydrate, and this is partially utilized during the winter months, resulting in a fall in body weight in both localities at this time. The changes in body weight for animals of the 5 + year group during one-year's growth have been calculated and estimates made of the contribution to total production represented by growth, gonadal development and storage of reserves.

The bivalve Donax vittatus (da Costa) occurs in Kames Bay, Millport, Scotland,only intermittantly. Successful settlements may occur with a frequency of no more than two in twenty years. There was one such settlement in the summer of 1962. The distribution in 1967 of survivors from this settlement was mainly just below L.W.S.T. Shell ring measurements indicated that the maximum mean size was reached in 5–6 years. Seasonal changes in body weight and biochemical composition are associated with the processes of reproduction, growth, and storage and utilization of reserves. The main period of increase in reserves and of gametogenesis corresponded with the spring peak of diatom abundance. The autumn peak of phytoplankton abundance is apparently less well utilized, although there is some increase in carbohydrate reserves. Spawning, which occurs in the early summer, produces a marked fall in the mean body weight, and a slower fall during the winter months is the result of elimination of reserves to meet the metabolic demands of the animal when food is scarce.

Estimates of the organic production by mass cultures of Phaeodactylum grown in outdoor tanks have been made from changes in the packed volume of the cells in culture, from oxygen bottle cxperimcnts, from change in the inorganic phosphate content of the medium, and by harvesting the cells. The results confirm the validity of comparisons upon which production estimates in earlier series of experiments wcrc based. Harvcstcd cells have been analyzed and the bulk constituents found not to vary greatly in spite of variation in the growth rate and in size of cell. Phosphorus balances made at the bcginning and end of each period of cultnrc show that the efficiency of incorporation of added nutrients into the cell is high.

Observations were made on the movements of the bivalves Mactra olorina and Donax incarnatus , and of the gastropod Bullia melanoides , collected from an exposed sandy beach near Shertallai in southwest India. The burrowing movements were remarkable for the speed at which they occurred. In Mactra olorina , the foot probed with a frequency of at first 8–9 probes per sec, later reduced to 5 probes per sec. The events associated with the establishment of the pedal anchorage and of active downward movement occupied 0.35 sec only and those of establishment of the shell anchorage and of probing occupied 1.15 sec. The complete digging cycle occupied 1.5 sec. These movements are compared with those of M. corallina from the Mediterranean and from the Clyde. The movements responsible for recovery from deep burial were also examined. Rapid burrowing and active upward movement through the sand, as appropriate, enable the animal to maintain its position in disturbed sediments. Similar observations were made on Donax incarnatus , which was compared with the north temperate species D. vittatus . In D. incarnatus rapid burrowing and active emergence form part of a complex of movements which lead to tidal migration of the population on the beach. Tidal migration was also a feature of the behaviour of Bullia melanoides , and in this species too, rapid burrowing and active emergence from the substratum at appropriate times are elements in the complex of movements by which this tidal migration is performed.