Gut Residence Time Research Articles

The feeding habits of the amphipods Lembos websteri Bate and Corophium bonnellii Milne Edwards

The gut contents of both Lembos websteri Bate and Corophium bonnellii Milne Edwards include detritus and sand grains. Lembos websteri collected from Laminaria holdfasts also contain strands of filamentous algae although Corophium bonnellii do not. In addition, macroalgal fragments and naviculoid diatoms are present, more often in Lembos websteri than in the guts of Corophium bonnellii. Occasionally, in animals collected from a sheltered algal turf, arthropod appendages may also be observed in the gut of Lembos websteri. The size of particles consumed by Lembos websteri is larger than in Corophium bonnellii. Feeding in both species is primarily by filtration but a variety of other methods may be used, including deposit-feeding, consumption of food of animal origin (including the species' own eggs), and consumption of tube material. These alternative techniques are brought to bear increasingly in poor feeding conditions. The behavioural sequences involved in these activities are described in detail and food preferenda related to the nutritional state of the animals. Defaecation in Lembos websteri (males and females) is normally followed by immediate refection of the faecal pellet but again is more noticeable when food is scarce. Gut-residence time in both species is ≈ 2 h at 13–15 °C. The proposition is made that Corophium bonnellii is a more efficient small-particle filter-feeder than Lembos websteri and that as such, it has met no evolutionary requirement to recycle its faeces (large particles) in the manner of L. websteri. Lembos, on the other hand, having a very “plastic” feeding repertoire appears to be better adapted to withstand periods of low food availability. The larger particles on which L. websteri feeds will be scarcer and will require more turbulence to keep them in suspension and even at exposed localities where L.websteri is more common, periods of calm occur, so flexibility in food-gathering technique is clearly advantageous. The more efficient small particle filter-feeding technique of Corophium bonnellii is well suited to a life in sheltered waters, where only the smallest particles remain in suspension for long periods, which is so typical of the genus.

Some observations on food and feeding of the supralittoral beach-hopperOrchestia gammarellus(Pallas) (Crustacea: Amphipoda)

Abstract The composition of faeces from Orchestia gammarellus collected from different supralittoral biotopes was found to vary according to position on the shore. Consumption of different materials was to some extent a function of availability. Material of plant origin dominated: few animal fragments were found in the faeces. In short-term habitat selection experiments O. gammarellus chose to congregate amongst wetted straw rather than chopped kelp (perhaps reflecting availability of void space). Over the longer term, in raw straw/alga mixtures, O. gammarellus preferentially consumed algal material. The size of angiosperm vascular (tracheid) elements consumed by O. gammarellus gave insight into food particle handling by the amphipod. The maximum length of tracheid elements approximated to oesophagus length suggesting that more rigid particles are pushed or sucked through the mouth lengthways until the proximal end reaches the opening of the stomach whereupon the distal end is bitten off. Given a choice between hard and soft food items, Orchestia gammarellus habitually chose to consume softer items. Certain red algae and Ulva may be unpalatable. Gut residence time at 10 °C is ∼ 10-22 h. Food consumption was markedly reduced in continuously-lit conditions but continued at a high level under aerated water. Acidification of seawater to pH values <6.8 inhibited feeding. Presented with agar made up with different salt contents O. gammarellus ate more of (and preferred) the more saline food. Alkali treated, macerated straw was an acceptable food for all size-classes. Orchestia gammarellus exhibited little reaction to amino acid tainted filter paper (present at 10-2 M), except for glycine.

Food passage and defaecation in Ciona intestinalis (L.); The effects of suspension quantity and quality

The faeces of Ciona intestinalis (L.) (Ascidiacea) consist of a food cord thrown in a sinuous manner within a crescentic peritrophic membrane. With increasing suspension concentration the food cord swells, narrowing the gap between the sinuous folds, such that at satiation the folds are indistinguishable. The weight of faeces produced is dependent upon both the quantity and nature of paniculate suspension ingested. Gut residence time is constant and reduced assimilation efficiencies at higher particulate concentrations are thought to be associated with the degree of satiation.

The influence of food concentration and feeding rate on the gut residence time of Daphnia

The influence of food concentration and feeding rate on the gut residence time of <i>Daphnia</i>

Variable Gut Residence Time: Problems in Inferring Feeding Rate from Stomach Fullness of a Mysid Crustacean

The gut residence time of the mysid crustacean Neomysis mercedis is extremely variable and is negatively correlated with ingestion rate. In two experiments in which mysids were fed copepod meals followed by continuous exposure to Daphnia, passage times varied from less than 1 to more than 13 h, and there were significant negative correlations of both copepod and daphnid passage times with the average feeding rate on Daphnia. In a third experiment starved mysids retained significant amounts of material in the stomach for more than 3 d. This dependence of evacuation rate on feeding activity may invalidate attempts to infer absolute or relative ingestion rate from the stomach fullness of field-caught animals.

Aspects of feeding, including estimates of gut residence time, in three mytilid species (Bivalvia, Mollusca) at two contrasting sites in the Cape Peninsula, South Africa.

Individuals of three mytilid species (Choromytilus meridionalis; Perna perna; Aulacomya ater) from two sites characterised by different qualities of ration available to these suspension feeders showed different rates in some components of the physiological energy budget. These differences included higher feeding (=clearance) and respiration rates, but lower absorption efficiencies, in individuals from the site with the higher quality ration. A novel technique was employed to estimate the residence time of food particles in the digestive gland. Individuals showing higher feeding rates had shorter residence times than those feeding more slowly and a significant positive correlation was demonstrated between residence time and absorption efficiency. These relationships, together with an exponential increase in rates of respiratory heat loss with an increase in ingested ration, are suggested to provide these animals with a physiological flexibility to compensate for reduced food quality in a way consistent with some theoretical predictions. Such compensations are made more effective if the total gut capacity can also change in response to the quality of the ration.

Seasonal variation in the balance between physiological mechanisms of feeding and digestion in Mytilus edulis (Bivalvia: Mollusca)

Seasonal variations in the balance between physiological mechanisms of feeding and digestion are considered among 45 to 57 mm shell length Mytilus edulis L. from southwest England. Mussels had been acclimated to standardised conditions of food availability in March, June and October, 1981. Results indicate that despite showing a negative relationship (P<0.001) with the efficiency of 15N absorption, coincident alterations of both ingestion rate (0.17 to 0.54 mg total Phaeodactylum tricornutum h-1) and organic gut content (1.00 to 1.80 mg) represent significant mechanisms effecting the seasonal regulation of nutrient acquisition. Concurrent changes in absorption efficiency alone clearly exerted a relatively minor influence upon seasonal rates of absorption. Associated gut residence times of 15N-labelled material varied between 4 and 10 h. Furthermore, despite the ensuing deleterious effects, together with increased gut contents, absorption efficiencies among mussels that had been starved throughout acclimation were consistently maintained equivalent to those among individuals feeding normally. Such constancy was at least partially achieved by an increased residence time of material within diverticulae, relative to the digestive system as a whole. Finally, comparison of isotopic absorption efficiencies with those recorded for total organics and organic nitrogen has demonstrated differences of as much as 30% between “gross” and “net” uptake due, we suggest, to excretion of metabolically derived material within the alimentary canal.

Comparison of estimates of the predatory impact of ctenophores by two independent techniques

The common methods for estimating food consumption in the environment involve either (1) performing experiments in the laboratory and relating food concentrations used to those in the environment, or (2) analyzing gut contents of animals directly from the environment and estimating food consumption by some knowledge of gut residence time. Both techniques involved compromises and assumptions. The greater precision and speed of the laboratory approach is counterbalanced by the impossibility of duplicating the natural feeding milieu. We compared predation rates of the ctenophores from gut content analysis of ctenophores in 1 300 m3 enclosures, with the estimates of expected predatory effects based on controlled laboratory experiments, over a wide range of ctenophore size and food concentration. Despite some larger discrepancies, the two methods often yielded results within a factor of two of each other.