Activity patterns in the terebellid polychaete <Emphasis Type="Italic">Eupolymnia nebulosa</Emphasis> assessed using a new image analysis system

The activity and surface sediment displacement by the terebellid polychaete Eupolymnia nebulosa were monitored, using new image acquisition and image analysis procedures. We used a video sensor mounted on a motorized table, to acquire adjacent images of the whole studied aquarium within about 2 s. These images were then grouped within a composite image acquired every 15 s. Consecutive composite images were compared to infer activity and surface sediment displacement. This procedure proved efficient for E. nebulosa as indicated by (1) the continuity of the tentacles within composite images, and (2) the direct comparison of images and detected activities. There were important temporal changes in the relative importance of the three main types of activity: feeding, tube-building and (both partial and total) emergence from the tube, accounting, respectively, for 75, 15 and 10% of the entire experiment duration. Activity intensity (cm² min^-1) was assessed through the surface of pixels with grey levels differing by more than 20 (on a 0–255 scale) between two consecutive images. Feeding was associated with low activity intensity, whereas tube-building and emergence from the tubes were associated with high activity intensities. Surface sediment displacement mostly resulted from tentacle activity both during feeding and tube-building and was almost zero when worms emerged from their tube. We used our experimental set up to assess spatial changes in activity intensity and particle displacements along the tentacles. Most of the activity occurred within the first 4–6 cm from the tube aperture. Particle loss during their transfer along the tentacles preferentially affected larger particles as postulated by the model of particle selection and transport in tentaculate deposit-feeders. Moreover, the speed of the particles along the tentacles correlated negatively with their size. This contributed to increase in the residence time of larger particles on the tentacles and thus, to further enhance their probability of being lost. The size distributions of particles during feeding and tube-building did not differ significantly although visual observations confirmed the preferential use of larger particles for tube-building. This suggests the existence of a sorting step occurring elsewhere than on the tentacles as already demonstrated for spionid polychaetes.     

Factors influencing particle selection and feeding rate in the polychaete Cistenides (Pectinaria) gouldii

Feeding behavior of the deposit feeding polychaete Cistenides (Pectinaria) gouldii was examined to determine factors affecting particle selection and feeding rate. Worms were found to select large particles preferentially and particle size selection increased with worm size. Particle selection behavior was unaffected by changes in sediment bacterial abundance. Feeding rates were affected by sediment size, bacterial density and worm size. Generally feeding rates increased in sediment containing more food, although the response was worm size specific. When viewed in a theoretical construct these results were inconsistent with predictions of deposit feeder optimal foraging models. Alternative explanations, such as morphological constraints placed upon the polychaete, may explain C. gouldii feeding behavior.     

The microhabitat of Symbion pandora (Cycliophora) on the mouthparts of its host Nephrops norvegicus (Decapoda: Nephropidae)

The microhabitat of Symbion pandora (Cycliophora) was described by recording the prevalence and distribution of two life cycle stages, namely feeding individuals and chordoid cysts on the mouth appendages of 65 Norway lobsters. The commensals infested lobsters with a carapace length >35 mm, while the intensity of the commensals increased with host size up to more than 1,100 feeding individuals and 173 chordoid cysts. Feeding individuals and chordoid cysts were found on all six pairs of mouth appendages, but were rare on Mxp3. A Kruskal–Wallis analysis of variance showed that the distribution of the two stages over individual segments deviated significantly from random expectations (P<0.001). Feeding individuals densely aggregated on a few medial segments, generally those that are pervaded by suspended food particles during host feeding. Chordoid cysts, which arise from non-feeding females occurred in low numbers and were more evenly distributed over the segments, often aggregating on the lateral parts and in the articulations of the segments. Based on these findings we suggest that the feeding activity of S. pandora is synchronized with that of the host.     

Particle size-selection of two deposit feeders: the amphipod Corophium volutator and the prosobranch Hydrobia ulvae

The feeding biology of the deposit-feeding amphipod Corophium volutator is compared to that of the coexisting, deposit-feeding prosobranch Hydrobia ulvae. Regarding ingestion of particles, both forms show size selection which alone can explain their coexistence. Particle size-selection also explains some qualitative differences in the composition of the food of the two forms; thus, diatoms play a relatively larger role in the diet of H. ulvae than in the diet of c. volutator, whereas bacteria are probably relatively more important for the latter. Results of experiments with feeding of C-14 labelled microorganisms are in accordance with the findings on particle size-distribution of the gut contents, and show that (1) C. volutator can only utilize bacteria adsorbed to particles within the size range 4 to 63 (this is why the presence of clay and silt particles in the sediment are necessary for efficient feeding of this amphipod); (2) C. volutator can utilize bacteria suspended in the water pumped through its burrow for respiration if silt and clay particles are present in the sediment. (3) H. ulvae can utilize large particles, and also browses on surfaces, and some evidence is brought forward that it also utilizes mucus for trapping microorganisms. The coexistence of deposit-feeding animals is discussed. It is concluded that the number of coexisting, closely related species is usually small, and that their resource partitioning is probably mainly based on particle-size selectivity. In the case of unrelated forms (e.g. H. ulvae and C. volutator, a number of behavioural, physiological and morphological differences, and also the widespread ability of deposit feeders to utilize alternative feeding mechanisms may also lead to resource partitioning. Thus, there are often several niche dimensions related to feeding allowing a certain diversity of coexisting deposit feeders.     

Grazing by adult estuarine calanoid copepods of the Chesapeake Bay

Grazing by adult female Eurytemora affinis, Acartia tonsa and A. clausi on natural distributions of particles from the Chesapeake Bay has been investigated. During the course of a year's sampling, a wide variety of particle size-biomass distributions were observed as seasonal shifts in detritus, and over 150 algal species occurred. These distributions were grouped into 5 basic types in the analyses of feeding. All three species demonstrated similar capabilities for feeding over a broad range of particle size with selection (higher filtering rates) on larger particles and on biomass peaks. Feeding on multiple-peak distributions resulted in strong selection or tracking of each biomass peak with reduced filtering rates between peaks. Evidence is presented which suggests that the copepods first feed on large particles and then successively switch to biomass peaks of the smaller size categories. Comparisons of the feeding behavior of Eurytemora affinis and the Acartia species showing that the Acartia species have greater capabilities for taking large particles may be associated with modifications of their mouth parts for raptorial feeding. The results suggest considerable flexibility in copepod feeding behavior which cannot be explained solely by the mechanism of a fixed sieve.     

Molt cycle alterations in behavior,feeding and diel rhythms of a decapod crustacean,the spiny lobster Panulirus argus

The crustacean molt cycle manifests extensive behavioral changes in addition to physiological and integumentary modifications. The paucity of quantitative studies led us to characterize molt stage dependent alterations in rhythmic locomotor, feeding, and agonistic behavior of subadult spiny lobster Panulirus argus held grouped and solitarily in simulated natural conditions. Non-disruptively determined molt stages were defined as proportions of intermolt duration. Significant nocturnal rhythmicity persisted through the full molt cycle, though daily form varied as a function of activity level and molt stage. A distinct early evening peak signaled initiation of foraging and walking behavior. Thereafter, rhythm amplitude either declined progressively (low activity: unimodal pattern), remained high (high activity: nocturnal plateau), or exhibited a secondary early morning peak (intermediate activity: bimodal and polymodal patterns). Activity ceased at or immediately prior to sunrise. Ecdysis was predominantly nocturnal, probably reflecting species specific spatiotemporal movement patterns and social behavior. A selective advantage of nocturnal ecdysis was postulated concerning avoidance of cannibalism and diurnal predators. Locomotor activity and feeding rates were not equivalent through the molt cycle, though both peaked in stages B₂-C₁. Locomotor activity remained high in metecdysis, decreased sharply at proecdysis initiation (D₀), reaching lowest levels in D₁-D₃, then increased in D₃ through B₁. Activity dropped steeply at ecdysis, though lobsters were capable of intense and coordinated activity. Feeding decreased slowly through metecdysis after the B₂-C₁ maximum, then increased temporarily in C₄ and D₀, indicating heightened feeding motivation. This contrasts with the locomotor activity decrease at proecdysis. Food consumption declined rapidly in D₁ and D₂ and ceased at the D₂-D₃ transition. Feeding resumed in B₁ or B₂, intensifying to maximum in late B₂. Feeding remained relatively constant within stages, whereas locomotor activity varied greatly, though both correlated with metabolic needs. Grouped and solitary lobsters displayed similar patterns of foraging and walking, equivalent to those of locomotor activity and feeding of solitary individuals. Frequency of agonistic interactions (not aggression per se) remained relatively constant through the cycle, peaking in metecdysis, though the highest relative proportion occurred near ecdysis. Lobsters then were submissive and avoided physical contact with conspecifics. Clearly, locomotor activity, feeding, and social behavior of P. argus are not simply determined. Indeed, behavior is distinctly phase coordinated with varying metabolic requirements dependent on the proximity to ecdysis and ecological pressures.     

Changes in feeding mechanisms during early ontogeny in juveniles of <Emphasis Type="Italic">Crepidula fecunda</Emphasis> (Gastropoda,Calyptraeidae)

Feeding in early life stages of the sedentary snail Crepidula is effected both by the use of the radula and by filtering with the gill. The present study is a contribution to the knowledge of the mechanisms of feeding by early juvenile snails of Crepidula fecunda. Experimental observations were made on specimens of known ages as they were fed constant concentrations of microalgae in the presence of a primary biological film on a glass substrate. Feeding activity was filmed under the microscope, and images were digitized for the identification and quantification of feeding structures. A morphological analysis was made of the structures associated with this process. Results showed that the radula was functional beginning in 1-day-old juveniles, and the gill functioned in respiration. Gill function in filter-feeding began in juveniles of 9 days old when dorsal and ventral ciliation had developed, as well as the food pouch. The latter structure begins activity as soon as the gill starts food collection. Osphradia appeared simultaneous with development of the filter feeding capacity by the gill. In their earliest stages after metamorphosis, the young snails begin life by radular scraping of primary biofilms, gradually shifting to filter feeding as the gill developed a critical number of filaments and cilia.     

Relation of particle-size spectrum and food abundance to particle selectivity in the mud snail Hydrobia totteni (Prosobranchia: Hydrobiidae)

We studied the relationship between particle-size selectivity and variable particle-size distribution in the American mud snail Hydrobia totteni Morrison (Prosobranchia: Hydrobiidae) collected in the summer of 1979 and 1982, from saltmarsh mudflats at Flax Pond, Old Field, New York, USA. Using individual size fractions of native sediment, snails fed fastest on intermediate-sized particles (41 to 63 m); this pattern was related to diatom abundance, which was similarly greatest on the intermediate particle-size classes. These results conform to another study, which found a quite different relationship between feeding rate and particle size, but a similarly strong correlation between particle size and diatom abundance. Snails were fed a range of particle-size distributions of glass beads. As median particle size increased, preference shifted towards smaller particles. This shift cannot be explained by feeding rates determined from individual particle-size classes. The most reasonable alternative model is a shift towards feeding on fine particles that occur among the coarser particles that are not ingested. Our data suggest that diatom growth on certain particle sizes is as important to particle selectivity as the particle sizes themselves. Particle size preference cannot be extrapolated from studies of feeding rates on individual size classes since selectivity is qualitatively different in mixtures of various size classes.     

Comparing macroalgal food and habitat choice in sympatric, tube-building amphipods, Ampithoe lacertosa and Peramphithoe humeralis

For small tube-building amphipods that live on the algae they consume, food and habitat are tightly linked. This study compared two closely related amphipods to determine whether the species’ algal preferences are based on the food value of the algae or on some other aspect of their algal habitat. Ampithoe lacertosa and Peramphithoe humeralis are both abundant on Shannon Point beach (Anacortes, Washington, USA; 48°30.542′ N, 122°41.070′ W) but specialize on different algae. In observations and laboratory experiments conducted July–September 1997, 2007, and 2008, the two species exhibited markedly different choices of food and habitat when offered six common macroalgae. Ampithoe lacertosa ate all algae offered, but preferentially built tubes on the green alga Ulva lactuca. Survival was relatively low among juveniles maintained on single species diets, except when they were fed Mazzaella splendens. Conversely, P. humeralis consumed primarily the brown kelp Saccharina latissima, Alaria marginata, and Desmarestia ligulata and preferred those species for tube building. Juvenile P. humeralis could not survive on a diet of U. lactuca or M. splendens. While A. lacertosa builds simple, temporary tubes and relocates frequently, P. humeralis is a highly thigmotactic species that builds long-term, complex tubes on the alga it prefers to eat. Feeding and habitat preferences of the two species were not clearly linked to nitrogen content of the algae, C:N ratio, or toughness of the algal tissue. Instead, preferences of the species may be related to their mobility and the permanence of the tubes they build. Ampithoe lacertosa and P. humeralis also use different feeding strategies; the former appears to mix algae to produce a high-quality diet, while the latter is more selective and has a capacity for compensatory feeding. The species are abundant on the same protected rocky shores, but specialize on different algae for habitat and food. Results suggest that the nutritional requirements of these sympatric mesograzers differ considerably and even closely related species can exhibit divergent behavioral strategies.     

Foraging activity and resource use by three parrotfish species at Fernando de Noronha Archipelago, tropical West Atlantic

Parrotfishes are important components of the herbivore and detritivore guilds of tropical and subtropical reefs. Most of parrotfish species are protogynous hermaphrodites that change colour and sex, from initial phase females or males (IP) to terminal phase males (TP). We studied the foraging behaviour of Sparisoma amplum, S. axillare and S. frondosum, three syntopic scarids on the rocky reefs of Fernando de Noronha Archipelago, Tropical West Atlantic. The three parrotfish species differed in food selection and preference, but IP and TP individuals of the same species preferred the same food types, except for S. amplum. Feeding rates of IP individuals were higher than those of TP individuals, but the distribution of feeding frequencies throughout the day of IP and TP individuals of the same species was similar. IP individuals had higher feeding rates than TP ones, which seems related to the fact that TP individuals spend a large amount of time patrolling their territories and chasing away conspecific individuals at the study site. The general foraging pattern we found for S. amplum, S. axillare and S. frondosum is similar to patterns found for other parrotfish species in the Western Atlantic.     

Early recognition of sediment during settlement of<Emphasis Type="Italic"> Eupolymnia nebulosa</Emphasis> (Polychaeta: Terebellidae) larvae

Analysis of the displacements and activity of larval stages of the terebellid polychaete Eupolymnia nebulosa were carried out on different sediment types collected in the Bay of Banyuls-sur-Mer (western Mediterranean). Results indicated sediment recognition by the larvae. Time devoted to exploration and settlement trials were significantly longer when sediments of similar granulometry had been previously reworked by adults. There were increased responses of settling larvae if the tentacles of adults of the same species had previously been in contact with the tested sediment. The early settlement activity was stronger at the sediment boundaries and increased in the coarse sediment. Our results suggest that larvae are able to recognize biologically bioturbed sediments and modify their behaviour accordingly. There is a larval settlement before the competent stage. Possible consequences of early settlement and the limitation of dispersal in Eupolymnia nebulosa larvae are discussed together with the results of automated measurements of early larval swimming.Communicated by S.A. Poulet, Roscoff     

Tidal-linked behaviour of the shrimp Ligur uvea in a land-enclosed marine pool

At Aldabra Atoll, the shrimp Ligur uvea inhabits a land-locked marine pool which is connected to the sea by a subterranean fissure. The shrimps migrate daily with the tide from a hole in the subterranean labyrinth to a feeding area at the bottom of the pool. The timing of the migration is tidal-linked and independent of light and temperature. With each incoming tide, tagged individuals return to a definite feeding ground. Such homing has not been reported from other L. uvea pools. Feeding activity was quantitatively measured, differences between day and night activity are interpreted as adaptations against predators (terrestrial wading birds). Compared to other L. uvea pools, the shrimps at Aldabra Atoll are exposed to a more rigorous environmental situation, which probably influences the tidal-linked behaviour of the local shrimp population.     

Predatory feeding of two marine mysids

Predatory feeding of the marine mysids Mysidopsis bigelowi and Neomysis americana on several species of co-occurring copepods was examined in laboratory experiments. M. bigelowi exhibited a curvilinear functional response; there was a negative logarithmic relationship between prey density and clearance rates. N. americana also exhibited higher clearance rates at lower prey densities. Increased clearance rates at lower prey densities were probably due to increased swimming speed or reaction distance as hunger increased. This response occurred only when mysids could visually locate prey; in complete darkness clearance rates were significantly lower and independent of prey density. Feeding rates on different prey species were only partially dependent on prey size; prey movement patterns and escape behavior also strongly affected feeding rates. M. bigelowi showed active prey selection when offered a choice of different prey species. Estimates of predation rates of estuarine mysid populations indicate that they could have a significant effect on co-occurring copepod populations.     

Particle retention and selection by larvae and spat of Ostrea edulis in algal suspensions

Grazing rates and electivity indices of larvae and spat of Ostrea edulis L. were, measured and examined in relation to certain physical parameters using a flow-through system. Retention and size-selection were determined for the major particle sizes present in cultures of Isochrysis galbana Parke, an alga used frequently as food for bivalves. Cultures of the algae Dunaliella tertiolecta Butcher and Phaeodactylum tricornutum Bohlin were used as sources of particle suspensions of various sizes and shapes, respectively. While increases in flow rate caused increased grazing, the mode of selection of I. galbana particles remained constant. Filtration rate, F _f was related to body size, W, by the general allometric equation R _f =aW ^b,while particle-size preference in suspensions of I. galbana by both larvae and spat of O. edulis was independent of W. Grazing rates increased with temperature to an optimum temperature, which was related to the acclimation temperature. Increases above this optimum caused a reduction in feeding activity. No significant change in particle size-preference in the I. galbana suspension with temperature was observed. Grazing rates and selection were dependent, however, on particle number and volume. Both larvae and spat displayed maximum retention at optimum particle concentrations which tended to decrease with increasing particle size. Variations in cell shape of P. tricornutum had no measurable effect on selectivity by O. edulis.     

Feeding rate and duration of daily activity of Astropecten aranciacus (Echinodermata: Asteroidea) in relation to prey density

In a feeding experiment, 16 individuals of Astropecten aranciacus were kept in two enclosures on the sea floor, and were provided with a surplus of food. Feeding at a daily rate of 1.3% of their dry tissue weight, their food intake was four times higher than that of free-living sea stars. The periods of daily activity were shorter than in control individuals kept in enclosures without additional food.     

Gezeitenrhythmische Nahrungsaufnahme und Kotballenablage einer terrestrischen Milbe (Oribatei: Ameronothridae) im marinen Felslitoral

Feeding, locomotory and defecatory activity of the algivorous orbatid mite Ameronothrus marinus have been measured under defined conditions in the laboratory. Of terrestrial origin, these mites inhabit the intertidal zone of rocky shores along the North and Baltic Seas. Under daylight cycles found at the sampling site and in the absence of tides, feeding and defecation follow an endogenous rhythm with a spontaneous period of 12.3 h; in the tideless littoral of the Baltic Sea these activities are synchronized with diurnal cycles. Feeding and defecation follow a definite sequential pattern, repeated on the average every 4 h, i.e., 3 times between two high tides. The phase of this tidal feeding-defecation rhythm is determined by the onset of the high tide, and different patterns of this rhythm can be observed according to the tidal zones. Inhabitants of the lower eulittoral exposed to longer periods of submersion start feeding earlier, take up more food at one time before the beginning of high tide, quickly defecate part of the food undigested after feeding, and later produce other faecal pellets which contain the real remains of digestion. Inhabitants of the upper eulittoral, exposed to shorter periods of submersion, start feeding later and extend their feeding activity over the whole period of low tide; the difference between faecal pellets with digested and undigested contents is indistinct. The occurrence of these different types of faecal pellets in inhabitants of the intertidal zone is interpreted as a compensatory physiological adaptation resulting from increasing periods of submersion.     

A contribution to the food and feeding habit of the threadfin Galeoides decadactylus

Previous literature on the biology of the threadfin Galeoides decadactylus (Bloch, 1795) and the different methods of food analysis are reviewed. Against this back-ground, new results obtained on food and feeding habit are presented. All specimens sampled belong to the first 2-year classes (Longhurst, 1965). Fishes of the same length are shown to have a wide range of weight, attributable to the effect of spawning and sex change; G. decadactylus is a protandrous hermaphrodite (Longhurst, 1965). Feeding intensities and condition factors are generally high, and show a direct relationship with the size and, consequently, sex, of the fish. The comparatively low percentage of empty stomachs recorded is attributable to the rather more favourable feeding conditions existing in inshore waters where the fishes were caught. G. decadactylus feeds mainly on small seasonally alternating varieties of crustaceans and young fish. Analysis of the composition of the fish food reconciles the apparently contradictory results obtained by Monod (1927), Cadenat (1954) and Longhurst (1957, 1960). The absence of certain common demersal food items such as mud and cephalopods in the stomach of G. decadactylus leads to the conclusion that the fish is selective in its feeding habits.     

Degradation of mangrove leaf litter by the tropical sesarmid crab Chiromanthes onychophorum

The food and feeding habits of 3 species of gadoid larvae — the cod Gadus morhua Linnaeus, 1758, the whiting Merlangius merlangus (Linnaeus, 1758), and the bib Trisopterus luscus (Linnaeus, 1758), collected in the eastern English Channel and Southern Bight during the spring of 1971 are described. All 3 species began to feed in the yolk-sac stage on diatoms, dinoflagellates and tintinnids, but the principal food was the nauplii and copepodites of calanoid copepods, particularly of Pseudocalanus minutes, but also of Paracalanus parvus, Temora longicornis and Acartia clausii. Pseudocalanus minutus and Paracalanus parvus were eaten mainly early in the season and T. longicornis later when it became more abundant. The larvae discriminated for prey size as growth proceeded. They sometimes took the largest prey available to them, but in general the size of the prey was considerably less than the maximum size which could have been swallowed. Feeding larvae were found at all times of the day, but the incidence of feeding was lowest before dawn. Feeding increased at sunrise, declined until late in the morning, and then increased again to a maximum around sunset. There was evidence of feeding by moonlight, particularly by whiting and bib larvae. There was little difference between the English Channel and Southern Bight in regard to the food eaten.     

Feeding grounds for waders in the Bay of the Mont Saint-Michel (France): the Lanice conchilega reef serves as an oasis in the tidal flats

The tube-building polychaete Lanice conchilega can form dense populations, often called reefs, which promote benthic community change and constitute feeding grounds for secondary consumers. The aim of this study was to quantify the role of the L. conchilega reef of the Bay of the Mont Saint-Michel (BMSM) for feeding waders, by combining macrobenthos data, bird counts and bird diet information. Wader densities in the reef were on average 46.6 times higher than in non-reef areas. According to faecal analyses, waders in the reef mainly selected the accompanying fauna and especially crustaceans. The attractiveness of the reef to feeding birds may be largely explained by the high abundance, richness and biomass of macrobenthic species in the reef compared with the rest of the BMSM.     

Feeding responses of the tentaculate deposit-feederEupolymnia nebulosa (Annelida: Polychaeta): Influence of sexual maturity

Feeding responses of the tentaculate depositfeeding polychaeteEupolymnia nebulosa (Montagu) were studied by measuring rates of uptake of three different¹⁴C-labelled diatoms (unialgal cultures ofNavicula incerta Grunow,Nitzschia acicularis Wm Smith, andNitzschia sp.). Worms used during this study were collected in the harbor of Port-Vendre (Western Mediterranean) during August 1986 (immature worms) and December 1987 (mature worms). Uptake rates were affected both by the length of the experiments and by the nature of the food offered. The highest rate of uptake (2.98 10^–4 mg ashfree dry wt of algae mg^–1 dry wt of worms h^–1) was obtained during short-term experiments (4 h) with the smallest diatom (Nitzschia sp.). The lowest rate of uptake (0.21 10^–4 mg ash-free dry wt of algae mg^–1 dry wt of worms h^–1) was also obtained withNitzschia sp., but for a long-term (48 h) experiment. There was no significant difference between rates of uptake of immature and mature worms.