Suspension-feeding Invertebrates Research Articles

Modelling of ciliary downstream collecting in suspension-feeding invertebrates

Modelling of ciliary downstream collecting in suspension-feeding invertebrates

PHYSIOLOGY OF THE ROCKY INTERTIDAL PREDATORNUCELLA OSTRINAALONG AN ENVIRONMENTAL STRESS GRADIENT

To gain insight into suborganismal mechanisms underlying responses of predators to environmental stress, we examined the effects of temperature and food availability on the physiology and feeding activity of the predatory whelk Nucella ostrina (formerly N. emarginata). Studies were conducted in the mid-low transition zone on rocky reefs at two sites on the Oregon coast: Strawberry Hill (SH) and Boiler Bay (BB). SH is dominated by suspension-feeding invertebrates and their predators, while BB is dominated by macrophytes. In wave-exposed (EX) and wave-protected (PR) habitats at each site, we measured air and water temperatures, whelk body temperatures, and indices of physiological condition (malate dehydrogenase [MDH] activities and RNA : DNA ratios) for wild-caught whelks. The influence of food (±prey) and thermal conditions (±shelter) on prey consumption, physiological performance (oxygen consumption rate), and response to thermal stress (induction of Hsp70-class stress proteins) of whelks was determined in field experiments. Low-tide air temperatures, whelk body temperatures, and biochemical indices of whelk field condition were consistently different between sites (SH > BB) and wave exposures (temperatures: PR > EX, condition: PR < EX). Foraging activity, metabolic rates, and stress protein (Hsp) expression were consistently higher at SH than BB. Respiration rates were lower for all −prey treatments than for +prey treatments; however, whelks in −prey +shade treatments had lower Hsp expression and higher respiration rates (an indication of better physiological condition) than whelks in −prey −shade treatments. Most measures of performance suggested that wave-exposed individuals were more physiologically robust than wave-protected individuals. Temporal physiological responses to stress suggested that high levels of heat stress compromise whelk performance later in the summer. These data are consistent with the hypothesis that physiological stress interacts with prey abundance to modify activity of whelks. Detailed studies of the effects of environmental stress on predator–prey interactions are needed to elucidate the relationship between physiological stress and predator–prey interactions. However, present evidence suggests that whelks alter activity (behavioral modification) and physiology (biochemical modification) in ways that lead to differential impacts by these predators on prey populations at different sites.

Influence of environmental factors on burrow irrigation and oxygen consumption in the mudflat invertebrate Urechis caupo

We examined burrow irrigation activity by the mudflat worm Urechis caupo in response to suspended food, ambient hypoxia (down to 3.3 kPa PO2), hydrogen sulfide exposure (up to 100 µmol l–1), and short-term temperature change (range 10–22°C). In normoxic, nutrient-free water at 14°C, O2 consumption \( \left( {\dot M{\rm O}_2 } \right) \) was 45 nmol min–1 g–1, water flow rate \( \left( {\dot V_{\rm W} } \right) \) was 27 ml min–1 (0.66 ml min–1 g–1), frequency of peristaltic waves (FP) was 2.6 contractions min–1, stroke volume (SV) was 11 ml, and O2 extraction coefficient (EO2) was 0.27. Adding suspended food to the burrow water occasionally elicited stereotypical feeding behavior but had no effect on any measured variables during nonfeeding periods. Hypoxia greatly decreased \( \dot M{\rm O}_2 \) (75% reduction at 3.3 kPa PO2) but did not affect \( \dot V_{\rm W} \) , FP, SV, or EO2. Sulfide at 50 µmol l–1 or less had no effect on burrow irrigation activity, whereas 100 µmol l–1 sulfide decreased \( \dot V_{\rm W} \) by 58% and FP by 50% but had no effect on SV. Temperature strongly affected \( \dot V_{\rm W} \) (Q10 of 1.9 from 10°C to 22°C). We propose that U. caupo's ability to live in the hypoxic, sulfidic mud of productive mudflat environments, combined with its very efficient mucous net, allows it to process much less water for feeding than other suspension-feeding invertebrates. This, in turn, necessitates an efficient O2 extraction mechanism, which is provided by the water lung activity of U. caupo's unique hindgut.

Gastropod shells recycled – an example from a rocky tidal flat in the northern Red Sea

Gastropod recycling at a rocky intertidal flat in the Northern Bay of Safaga (Red Sea, Egypt) is a process of increasing encrustation, changing secondary inhabitants, and probably decreasing shell strength. Encrustation by coralline red algae starts in the living gastropods, with the aperture area staying free of epigrowth. The dead gastropod shells are colonized by hermit crabs, tend to be more heavily encrusted and show encrustation of the aperture. This justifies the description ‘pagurized’ and the conclusion that coralline red algae produce the same pagurization features as predominantly suspension-feeding invertebrates. After the shells are abandoned by inhabitants that carry them around, further growth of coralline algae leads to rhodoliths, which are sometimes colonized by stomatopods. Secondary inhabitants therefore influence not only the taphocoenoses of gastropods but also the formation of rhodoliths.

Water flow over subtidal rock walls: relation to distributions and growth rates of sessile suspension feeders in the Gulf of Maine Water flow and growth rates

Moving water delivers food resources to sessile suspension feeding invertebrates and the interaction between water motion and substrate topography may dramatically influence the ecology of these animals. Growth rates of two species of sessile suspension feeders were compared between positions within individual 1.5-m high rock walls at an offshore site at 30-m depth in the Gulf of Maine, USA. The site is characterized by strong, highly variable water flow. Growth rates for the active suspension feeding mussel Mytilus edulis (Linnaeus), were greater at upper than at lower wall positions, while growth rates for the facultatively-active suspension feeding sponge Halichondria panicea (Pallas) showed the opposite pattern, with higher rates at lower than upper wall positions. Mussel and sponge growth rates were related both to patterns of bulk fluid flux across the walls and to naturally occurring distributions of sessile suspension feeders. Dissolution of alabaster and plaster solids indicated that upper wall positions experienced significantly higher bulk fluid flux than lower wall positions. Distribution data show non-random suspension feeder abundances across a series of small rock walls at two offshore sites. The abundance of passive suspension feeders was greatest near the top edges, while active and facultatively-active suspension feeders occur in greatest densities at lower wall positions. The results show that the interaction of small scale, abrupt, topographic features with variable local flow conditions can lead to physical gradients within rock walls. These gradients significantly affect the growth of suspension feeders, and may influence the structure sessile of invertebrate communities on subtidal rock walls.

Effects of zebra mussels on food webs: interactions with juvenile bluegill and water residence time

We evaluated how water residence time mediated the impact of zebramussels Dreissena polymorpha and bluegill sunfish Lepomis macrochirus on experimental food webs established in1100-l outdoor mesocosms. Water residence time was manipulated asa surrogate for seston resupply – a critical variable affectinggrowth and survival of suspension-feeding invertebrates. We used a2×2×2 factorial experimental design witheight treatment combinations (3 replicates/treatment) including thepresence or absence of Dreissena (2000 per m2), juvenilebluegill (40 per mesocosm), and short (1100 l per d) or long (220 lper d) water residence time. Measures of seston concentration(chlorophyll a, turbidity and suspended solids) were greaterin the short- compared to long water-residence mesocosms, butintermediate in short water-residence mesocosms containing Dreissena. Abundance of rotifers (Keratella and Polyarthra) was reduced in Dreissena mesocosms and elevatedin short residence time mesocosms. Cladocera abundance, in general,was unaffected by the presence of Dreissena; densities werehigher in short-residence time mesocosms, and reduced in thepresence of Lepomis. The growth of juvenile Lepomiswere unaffected by Dreissena because of abundant benthicfood. The final total mass of Dreissena was significantlygreater in short- than long-residence mesocosms. Impacts of Dreissena on planktonic food webs may not only depend on thedensity of zebra mussels but also on the residence time of thesurrounding water and the resupply of seston.

Effects of Flow and Seston Availability on Scope for Growth of Benthic Suspension-Feeding Invertebrates from the Gulf of Maine.

Metridium senile, the frilled sea anemone, and Modiolus modiolus, the northern horse mussel, are important members of benthic suspension-feeding assemblages at several rocky hard-bottom subtidal (30-35 m) sites in the Gulf of Maine. Measurements of food availability, rates of food capture, absorption efficiencies, and standard metabolic costs show that inshore populations of Metridium senile have a significantly lower scope for growth than offshore populations, despite higher mean concentrations of particulate organic matter inshore. Similar measurements and calculations for Modiolus modiolus reveal the opposite pattern. These differences persisted at both of these sites during two summers, 1989 and 1990, when differences in mean temperature were not physiologically significant. Thus temperature is precluded as the primary effect on metabolism and growth. We suggest that these physiological differences reflect a response to flow regime and food availability that appears to be manifested differently for Metridium senile and for Modiolus modiolus, a passive and an active suspension feeder, respectively. Results from a reciprocal transplant experiment, to measure growth rates, carried out over a one-year period support the calculated scope for growth during the season when maximum growth rates would be expected. The flux of seston appears to be an important factor affecting the organismal performance of the passive suspension feeder (M. senile), whereas the concentration of seston is more important for the active suspension feeder (M. modiolus).

Experimental Tests of the Advantages and Disadvantages of High Density for Two Coexisting Cockles in a Southern Ocean Lagoon

As a strong test of the prevailing generalization that competition plays a relatively trivial role among suspension-feeding invertebrates in the soft sediments on the estuarine seafloor, we manipulated local densities of bivalves, two species of Katelysia, in a Western Australia lagoon, characterized by exceptionally high bivalve abundances (averaging 157 m −2 ). Competition appeared weakly and sporadically, evident in only one of five intervals, when survivorship was 20-30% lower, production of undamaged empty shells 3-5 times higher, and average growth of survivors 50% lower for both Katelysia scalarina Lamarck and Katelysia rhytiphora Lamarck in the highest density treatment (320 m −2 ) than in the others (20-160 m −2 )

Food Availability and Resource Allocation in Senescent Placopecten magellanicus: Evidence From Field Populations

The relationship between present reproductive activity and possible trade-offs in future growth and reproductive potential has been a topic of interest to evolutionary ecologists. In many species of benthic suspension-feeding invertebrates energy available for growth and reproduction decreased as they increased in size until eventually all resources were required for maintenance metabolism and maximum size reached. By studying sea scallops from natural habitats with different food regimes it was possible to assess the role of food ration in the allocation of resources to reproduction when they are constrained by body size. Physiological estimates of seasonal energy intake and expenditure predicted maximum sizes of approximately 17 and 45 g for Placopecten magellanicus from habitats with low and high food availability, respectively

Impact of fouling organisms on mussel rope culture: interspecific competition for food among suspension-feeding invertebrates

The clearance rate of natural planktonic assemblages was measured for the blue mussel Mytilus edulis (L.) and a co-occurring fouling community from mussel rope cultures using flow cytometry. Blue mussels had significantly higher clearance rates for all particle types and size classes. In addition, blue mussels showed selective feeding in favor of small phytoplankton (3–5 μm), whereas the solitary ascidian Ciona intestinalis (L.) and the suspension-feeding gastropod Crepidula fornicata (L.) showed preferential selection for large phytoplankton (> 16 μm). Clearance rates for large phytoplankton by these members of the fouling community were, however, always lower than blue mussels. Under conditions where food is not a limiting factor, interspecific competition for food by the associated fouling community should not significantly limit the yield of mussels.

Total and methyl-mercury content in bivalves, Mytilus galloprovincialis Lamarck and Ostrea edulis Linnaeus: relationship of biochemical composition and body size.

Mussels and oysters are of interest to pollution ecologists because they are widely distributed, suspension feeding invertebrates and are likely to accumulate pollutants from their environment (Goldberg 1975). Many authors have estimated the relation between the concentration of metals in the flesh and various biotic and abiotic parameters. Body mass (estimated in dry weight) is evidently an important factor governing the uptake of metals by these organisms (Boyden 1974, 1977). Cossa et al. (1980) showed, furthermore, that the highest concentrations of certain metals were often found in the smallest individuals. The relation between metal content and body size can best be described using Boyden's model (Walne 1972; Boyden 1974) which is useful for quantifying any physiological activities in relation to the dry weight of the specimens. The regression coefficient b in Boyden's model is a measure of an organism's control over metal accumulation in its tissues. In practice, widely different values can be obtained for regression coefficient b when investigating the same metal. Cossa et al. (1979) suggested that this variability is primarily correlated with differing amount of gonad development. Gonad growth and maturation are accompanied by numerous biochemical changes in the flesh, especially in relation to glycogen content. Moreover, rapid changes in both wet and dry weights occur during the spawning period (Zandee et al. 1980). These changes are more profound in the largest individuals. Fortunately, the reproductive cycle of the mussel Mytilus galloprovincialis Lam. and Ostrea edulis L. have been thoroughly studied in Limski kanal by Hrs-Brenko (1971). In the present paper we describe our investigation into the relationship between total and methyl-mercury content and body mass in mussels and oysters collected in Send reprint requests to M. Najdek at the above address

The Trace-Fossil Diplocraterion: Evidence of Animal-Sediment Interactions in Cambrian Tidal Deposits

The U-shaped, spreiten-bearing burrows Diplocraterion parallelum and D. habichi in the Hickory Sandstone Member of the Riley Formation (Cambrian), record interactions with other metazoans and the substrate, thus revealing paleoecologic, sedimentologic, and environmental details about this basaltransgressive, cratonic sandstone in central Texas. These trace fossils establish the presence of a low-level suspension-feeding, infaunal trophic group not found in the Hickory Sandstone body-fossil record. Diplocraterion probably represents the activity of infaunal, suspension-feeding invertebrates. The Diplocraterion burrow depth of 19.5 cm is additional evidence for a Cambrian suspension-feeding tier deeper than previously estimated. Skolithos/Monocraterion rarely occur in facies with abundant Diplocraterion. High ambient water temperatures may have been a factor controlling the distribution of the organisms within the Diplocraterion-Skolithos/Monocraterion trophic group. The protrusive behavior (downward motion) of Diplocraterion resulted from the interaction with current flow of a high-density tube field of suspension feeders. This interaction caused turbulent eddies to impinge on the bed, resulting in current scour of the substrate. Sediment sorting within the Hickoty may have been a direct result of the reworking of vast tidal sand flats by infauna, aiding already strong tidal currents in removing mud-sized particles. Diplocraterion is a diagnostic marine trace fossil and can be used to separate nonmarine from marine environments in basal Paleozoic, cratonic sandstones. It is useful in identifying tidally influenced environments when found in facies resulting from high-energy deposition.

Streamlines and particle paths in the feeding mechanisms of larvae of the sea urchin Lytechinus pictus Verrill

Streamlines were produced by injecting Evans Blue dye into water currents pumped past sea urchin larvae held stationary on suction micropipettes. The larvae are hydrodynamically shaped in such a way that some of the water propelled backwards by their locomotory cilia is diverted forwards into their suboral pockets. Simultaneous particle paths and streamlines show that algae carried into the suboral pockets by the diverted water currents are captured by direct interception on the adoral cilia. These observations suggest that the pattern of water flow around suspension-feeding invertebrate larvae and adults may be more significant than some recent descriptions have suggested.

The stable carbon isotope ratio of some components of an eelgrass, Zostera marina, bed.

Living and dead Zostera marina blades, plankton samples, sediments, and several animal components of an eelgrass bed near Beaufort, N.C. were collected and analyzed for 13C/12C ratios (δ 13C). The δ 13C values of producer and consumer organisms were compared in order to examine the possible origins of organic matter present in the consumers. Living and dead eelgrass blades displayed similar δ13C values,-12.2 and-10.6 per mil ‰ respectively, while the epiphytic community growing on the grass blades had a mean isotope ratio of-16.0‰. Animal components analyzed represented five major feeding-mode categories: invertebrates living on grass blades an presumably feeding on the epibiota (-15.1‰), deposit feeding invertebrates (-15.0‰), predatory and omnivorous invertebrates (-16.7‰), suspension and surface feeding invertebrates (-18.3‰) and omnivorous fish (-16.8‰).Organisms commonly found on the grass blades appeared to feed primarily on the epibiota growing on the blades. It is hypothesized that the epibiota derive some of their carbon from DOC released by the Zostera blade. The urchin, Lytechinus variegatus, and the brittle star, Ophioderma brevispinum, both deposit feeders, appeared to derive a major proportion of their carbon from eelgrass. With the exception of the shrimp, Alpheus heterochaelis, and the pipefish, Syngnathus floridae, the majority of other organisms analyzed appeared to be linked more directly to a plankton-carbon food chanin than to a seagrass-carbon system in this relatively young eelgrass bed.

THE BENTHIC MACROFAUNA OF MORICHES BAY, NEW YORK

Quantitative sampling of the subtidal macro-benthos of a shallow temperate lagoon shows several structural features of benthic communities in five biotopes. Attempts are made to relate past and present qualities of benthic structure to long-term nutrient and organic loading of this lagoon. While overall benthic species composition has apparently not changed drastically since a 1938 qualitative survey, some important changes in dominant species composition appear to be associated with the biology of these principal species. The best estimate of average annual standing crop of the macro-benthos (< 5 g/m2, ash-free dry weight) is lower than estimates in somewhat comparable estuaries, apparently because of low oxygen concentrations over extensive areas during summers, which derive in turn from large summer influxes of nutrients and organic matter into this poorly flushed lagoon. Clear-cut associations between sediment type and mode of feeding of the benthos are demonstrated; suspension feeding invertebrates dominating in sandy sediments, and deposit feeders dominating in soft clayey silt bottoms. Species diversity appears to be homogeneous over most of the bay, with very low diversity in dredged channels. The need for more, and more carefully allocated, sampling effort in benthic studies is emphasized, given the imprecision in community structural features, particularly species diversity and biomass of genera and species.