Large Food Items Research Articles

Predator-prey relationships within the pelagic community of Neusiedler See

Neusiedler See, a shallow alkaline lake, has become increasingly eutrophic; this enrichment improved the nutritive situation of the herbivorous zooplankton leading to a higher standing stock. A multiple regression analysis of the long-term development of the crustacean plankton indicates that abiotic factors (i.e. wind, temperature) have the most important impact on the community in spring and autumn, biotic factors (i.e. food, predation) during the summer months. Currently an invertebrate (Leptodora kindti) and two planktivorous fish (Pelecus cultratus and Alburnus alburnus) control the population development of Diaphanosoma mongolianum during summer. L. kindti predation acts on immature stages, whereas the fishes consume adult stages. L. kindti densities of 100 to 200 ind. × m-3 affect the prey population to a negligible extent; densities between 300 and 500 ind. × m-3 result in elimination rates of 5% to >40% of the juvenile Diaphanosoma stock. The impacts by the invertebrate predator are pronounced but short-term events. Juvenile and underyearling fish eliminate 4–13% of the zooplankton in the open lake and 5–33% inshore; their predation pressure acts on all younger stages of the crustaceans. Planktivorous fish older than 0 + concentrate on the large food items (adult stages of the crustaceans). A. alburnus is able to consume 6–16% of the zooplankton standing stock during summer. P. cultratus eliminates about 1–49% of D. mongolianum, 1–4% of A. spinosus and 1–31% of L. kindti. From May until August the position of the dominant predator changes, beginning with juvenile fish which are then followed by P. cultratus and then by A. alburnus. Predation by L. kindti is of importance in July and August; at that time it causes suppression of the juveniles of D. mongolianum, but, on the other hand, the older stages of L. kindti are endangered themselves by the predatory impact of planktivorous fish.

Strategies and Tactics for Larval Culture of Commercially Important Carp

This paper reviews state-of-the-art techniques for culture of larval common carp, Cyprinus carpio, silver carp, Hypophthalmichthys molitrix, bighead carp, H. nobilis, and grass carp, Crenopharyngodon idella. Water temperature, food, and predation are important factors influencing larval survival and growth. Lower and upper lethal temperatures range from 3 to 44°C. Optimum growth temperatures range from 38 to 40°C. Lethal and optimum temperatures vary with acclimation temperature, fish age, and development stage of fish. Water temperatures are close to optimum for larval culture in tropical regions but are often too low in temperate climates. Intensive culture in temperature-controlled systems is important in temperate climates. The first food eaten by larvae in ponds consists mainly of protozoa, rotifers, and copepod nauplii. As fhe larvae grow, they quickly shift to larger food items, including cladocera and insect larvae. Management practices to enhance natural food development in earthen ponds include ...

Confined Modes Between a Lossy Slab Load and a Metal Plane as Determined by a Waveguide Trough Model

The particular mode types which can propagate in the region underneath a large thick food item in for example a microwave oven are investigated by a model using the geometry of a rectangular wave guide trough. The waves are trapped surface waves and may have inefficiently small losses to the load if there is no additional dielectric layer such as a shelf Too high losses, resulting in absorption of most of the energy in the outer parts of the load may, however, occur in slabs having dielectric properties corresponding to those of large frozen food items.

A comparison of the energetics of foraging of three species of Leptogenys (Hymenoptera, Formicidae)

Abstract. The three Leptogenys species L.nitida, L.schwabi and L.attenuata coexist in the coastal forests of South Africa and exhibit an array of foraging strategies ranging from individual foraging to group raiding. To determine whether there is a physiological basis for these strategies, the energetic cost of locomotion of individuals in these three species was determined. Carbon dioxide emission of voluntary running ants was measured using a flow‐through technique, in order to determine their metabolic rate when running. The minimum cost of transport was constant over a range of temperatures (20–35°C), and similar for all three species (common value 212.96 ± 17.35 Jkg_1m_1). A comparison of the energy required to sustain representative foragers at 25°C indicated that it was energetically less expensive for L. nitida workers to forage than for the other two species. This may explain why L.nitida uses group raiding, while the other two species use individual foraging with limited recruitment for retrieval of large food items.

Corticocolpoda kaneshiroae N. G., N. Sp., a New Colpodid Ciliate (Protozoa, Ciliophora) from the Bark of Ohia Trees in Hawaii

ABSTRACT Corticocolpoda kaneshiroae n. g., n. sp. was discovered in the bark of Ohia trees (Metrosideros polymorpha) from the Hawaiian Archipelago. Its morphology and infraciliature were studied in live cells, with the scanning electron microscope, as well as in specimens impregnated with protargol, silver nitrate, and silver carbonate. The new genus, Corticocolpoda, belongs to the family Colpodidae and is unique in having a left oral ciliary field (polykinetid) composed of 13–20 equidistantly spaced, paired rows of monokinetids. The new species, C. kaneshiroae, measures 100–300 × 60–250 μm and has a huge vestibulum used to capture large food items, mainly other ciliates. The oral ciliary fields are within the vestibulum and of equal length; the right field is a paroral membrane composed of a single row of dikinetids. Several micronuclei are attached to the ellipsoid macronucleus. The mucocysts are inconspicuous and arranged around the somatic dikinetids. The resting cyst is globular and has a 1–2 μm thin, firm, yellowish inner wall and a 20‐μm‐thick, fragile, hyaline outer wall. Convergent evolutionary paths and a possible polyphyly of the Colpodidae are discussed. An improved key to the genera of the family Colpodidae is provided. Twenty‐three species of ciliates and one flagel***iate (Hemimastix amphikineta), which occurred together with C. kaneshiroae, are new for the fauna of Hawaii and listed in the ecology section.

A comparison of two methods for sampling assemblages of subterranean, wood‐eating termites (Isoptera)

Abstract Within a 50 × 50 m area of wandoo Eucalyptus capillosa woodland in the Western Australian wheatbelt, the diversity and frequency of occurrence of wood‐eating termite species was assessed at two food types. Over a 12 month period, monthly termite activity was determined: (i) at sound/undecayed artificial baits (seasoned wooden stakes of Jarrah, Karri, Pine, Batu, Oregon; Jarrah sawdust; paper rolls); and (li) at naturally occurring timber, fallen logs and branches of wandoo, in varying stages of decay. Termite diversity was 11 species at baits, 18 species at wandoo out of an overall site richness of 21 species. Karri attracted the most species (9); sawdust attracted none. At wandoo, Nasutitermes exitiosus, Coptotermes acinaciformis and Occasitermes occasus accounted for 59% of samples where termites were recorded. At baits, Heterotermes occiduus accounted for a mean of 80% of samples across bait types, but was rarely sampled at wandoo (5% of samples). Only H. occiduus, C. acinaciformis and Amitermes neogermanus ate bait. Pine, Oregon and paper rolls were most effective in attracting foraging termites in terms of highest per cent of replicates showing bait consumption and highest consumption rates. Jarrah and Batu were least attractive to foraging termites. Samples from wandoo underestimated the relative frequency of occurrence of H. occiduus within the study site. Coptotermes acinaciformis, which attack large food items, and certain species of Amitermes, which forage on subterranean food, may have been underestimated by both sampling methods. These findings indicate that a proper understanding of the structure of wood‐eating termite assemblages within a given area requires a composite sampling strategy which addresses termites that eat sound or decayed wood, as well as surface and subsurface foragers.

Energy Trade‐Offs and Foraging Mode Choice in American Eels

American eels (Anguilla rostrata) use three different models when handling food: suction, shaking, and spinning (rotational feeding). We investigated mode selection and mode switching during foraging in terms of relative costs and benefits of different modes. Eels were fed food items that differed in size and consistency, thereby inducing particular modes. To test the hypothesis that American eels forage efficiently by selecting foraging models that maximize net energy intake and growth, we determined whether modes differed in short—term energy costs and long—term effects on growth rate, and whether eels preferred food types that maximize short— and long—term net benefits. Net energy intake (energy ingested — energy consumption represented by oxygen uptake) was greatest when suction was the chief mode employed, and was reduced during shaking and spinning. Animals using spinning fed the slowest and ate relatively little food. Eels fed a diet that required them to feed by only spinning or shaking lost mass faster than eels allowed to feed by suction. When given a choice of food types, eels preferred energetically efficient types (suction over both shaking and spinning, shaking over spinning). Our results suggest that rotational feeding is an alternative foraging mode that facilitates dismembering of large food items, but this benefit can be compromised by energy and time costs. Spinning is the least preferred mode and is used when other modes are ineffective. Mode switching in this species can be considered optimal in that mode choice and switching appear to maximize net energy intake in a manner that directly affects growth rate and, presumably, fitness.

Female-Biased Sex Ratio at Hatching in the Green Woodhoopoe

Female-Biased Sex Ratio at Hatching in the Green Woodhoopoe

Systematic revision of the neotropical ant genus Megalomyrmex Forel (Hymenoptera: Formicidae: Myrmicinae), with the description of thirteen new species

This revision includes comparative morphological analysis, biological data from various sources and a consideration of geographical distributions. The genus is considered to be a natural group, including 31 valid species, of which 13 are here described as new. The species are distributed in four groups, morphologically and behaviorally characterized; individual keys and distributional maps are given. All types were examined, except for that of M. bituberculatus (Fabricius, 1798), probably lost; the species is considered inquirenda. M. duckei Forel, 1912 and M. leoninus var. nasutus Forel, 1912 are considered junior synonyms of respectively, M. balzani Emery, 1894 and M. staudingeri Emery, 1890. The Modes tus group comprises medium sized species that occupy or dig cavities under logs or rocks. Colonies may be large and may have one to several true queens. Workers forage in groups on the ground of tropical and subtropical forests, recruiting nestmates toward large food items. In the Modestus group are described as new M. ayri, M. caete and M. cupecuara. The Leoninus group comprises larger species, the gamergates of which take over the reproductive function. Nests occupy cavities under logs, with no traces of architecture. Workers forage individually on the ground or on shrubs, tending membracid nymphs. New species in this group are M. acauna, M. cyendyra, M. pacova and M. timbira. Species of the Silvestrii group maintain apparent non-obligatory lestobiotic relations with several genera of Attini. They occupy secondary cavities of the nests of their fungus-growing hosts and always have monogynous colonies with true queens. New in this group are M. cuatiara, M. mondabora, M. piriana, M. poatan and M. tasyba. The Pusillus group includes the smallest species of the genus, which live in general in diffuse colonies in the litter of tropical and subtropical forests. Some species may have colonies either with gamergates or with true queens. The shape of the mandibles and the relatively large eyes suggest predatory habits. M. miri is the only new species in the group. Lectotypes and paralectotypes are designated for M. balzani, M. foreli, M. goeldii, M. iheringi, M. latreillei, M. leoninus, M. modestus, M. myops, M. pusillus and M. symmetochus.

Diet composition of larval Leiostomus xanthurus in and about the Mississippi River plume

The diet of the larvae of the sciaenid fish Leiostomus xanthurus collected within the Mississippi River plume differs from that of larvae collected in adjacent Gulf of Mexico shelf waters. Larvae collected in plume water had eaten twice as many food organisms as had larvae collected in shelf waters. Larvae collected within the plume had eaten mostly small food organisms (tintinnids, copepod nauplii, pelecypod veligers and invertebrate eggs), whereas larvae collected in shelf waters had eaten mostly larger food items (copepodite and adult copepods). Differences in the abundance of food organisms in and differences in the photic environments of these water masses may account for the differences in diet.

A Proposal Regarding the Source of Nutrition of Leptocephalus Larvae

AbstractThe large size, transparency and peculiar dental configuration of leptocephalus larvae can be interpreted as adaptations to a diet of large, transparent and soft food items. It is suggested that gelatinous zooplancton, in particular the discarded house of the Appendicularia or Larvacea, is their main food. Calculations show that an ingestion rate of the order of magnitude 10 houses/ hour is sufficient to sustain an eel larva.

Modelling heat transfer in fluidized beds of large particles and its applications in the freezing of large food items

Bed-to-surface heat transfer coefficients in fluidized beds of large particles were studied. It was found that heat transfer coefficients in fluidized beds of large particles are two to three times larger than those in forced air convection and that particle diameter had a reverse effect on heat transfer coefficient (e.g. larger particle has smaller bed-to-surface heat transfer coefficient). Freezing curves were compared for two food items in (a) fluidized beds and (b) forced air convection. Freezing time and moisture loss in fluidized beds were both less than those in forced air convection. Computer simulation showed close agreement between the predicted and experimental results.

Central-place foraging by Rattus norvegicus on a radial maze.

We studied central-place foraging in rats (Rattus norvegicus) by placing food items that varied in size and weight at the ends of a 4-arm radial maze. In Experiments 1-3, rats increasingly tended to carry food to the center of the maze as the size of those items increased. Very large food items often were hoarded in the center. Rats consumed food faster on the arms than in the center, and rats traveled faster when carrying food than when not. Blocking arm entrances increased travel time between the center and the arms and decreased food carrying at every item weight except the largest. In Experiments 4-6, important conditions that influence the degree of food-carrying behavior were discovered; these were the intersection of maze arms, the presence of a conspecific, and the use of open vs. closed maze arms.

Benefits of Courtship-Feeding for Rifleman (Acanthisitta Chloris) Parents

Abstract1. Courtship-feeding was studied in riflemen (Acanthisitta chloris) in a population at Kaikoura, South Island, New Zealand between 1982 and 1984. The proportion of the food males collected which was donated to his mate was calculated and what proportion of the female's diet this represented. This information revealed that males made a significant early season contribution to parental care. 2. Allied information collected during the pre-lay and egg-laying periods included the time to form eggs, laying interval and clutch size. 3. Courtship-feeding in riflemen involved no ceremony. 4. Copulation attempts did not correspond with bouts courtship-feeding or the peak of courtship-feeding. 5. Pairs spent 91.2% of daylight hours in each other's company, which facilitated coursthip-feeding. 6. Food items delivered in courtship-feeding were significantly larger than those eaten by males or females while foraging for themselves, and larger food items were consistently offered throughout the pre-laying and egg-laying periods. 7. The peak in the volume of food delivered to the female occurred about 3.5 days after the first egg was laid. 8. Overall the male contributed 42% of the food he gathered to the female and this comprised 35% of her total food intake. 9. Females fed themselves enough food to meet maintenance requirements and the extra required for oogenesis was received from the male through courtship-feeding and any reserves stored by the female. 10. Riflemen laid eggs every 48 hours which probably reduced peak energy demands during oogenesis. 11. Courtship-feeding was not associated with second clutches which were significantly smaller than the first clutch laid and reared in a season. 12. Incubation occurred after the last egg was laid but was sometimes delayed. During the delay courtship-feeding continued until incubation started. 13. Courtship-feeding represents a significant early season investment by male riflemen in their offspring which probably allows time to rear two broods thereby improving both parents' productivity. Such early season investment might influence sexual selection towards stable, monogamous pair bonds.

The feeding ecology of the African lily trotter Actophilornis africanus (Gmelin) at Lake Naivasha, Kenya

SummaryThe only feeding habitats available to African lily trotters, Actophilornis africanus (Gmelin), at Lake Naivasha are mats of the alien water fern, Salvinia molesta Mitch. This has replaced the native floating leaved water lily beds. Lily trotters were able to use these mats, taking invertebrate food items from the surface or turning plants over and pecking at the rootlets. Pecking rates and turning rates responded to the nature of the available food, with pecking rates high and turning rates low when terrestrial arthropods were found on the mat surface. Both pecking rates and turning rates were low when large aquatic food items, such as the swamp worm (Alma emeni Michaelsen), were available. Pecking rates and turning rates were both high when the predominant food items were aquatic insect larvae. The largest of these (hydrophilid larvae) were taken in preference to the smaller but commoner chironomid larvae. Colonization of the mats of S. molesta by invertebrates was low if the mats were affected by wind action but higher if they were constrained by enclosure or stranding; mats with higher invertebrate densities supported more feeding lily trotters.

Foraging activity of the sand beach isopod Scyphax ornatus Dana

Abstract The terrestrial isopod Scyphax ornatus lives on exposed sand beaches. Adult isopods spent the daytime in burrows near the high water mark and made nightly foraging excursions over the uncovered middle beach. Hourly records of their night time distribution showed that Scyphax congregated near the water’s edge during the last 4 h of flood tide, where they fed on carrion. Insects (mostly drowned honey bees) were the main food item, but coelenterates, amphipods, crabs, and goose barnacles were also eaten. During ebb and early flood tides Scyphax occurred at low densities over the uncovered middle beach. Analysis of the distribution of large and small food items on the beach showed that by feeding during the flood tide, Scyphax exploited a rich concentration of carrion that accumulated in the swash zone and that was moved slowly up the beach by the incoming tide.

Scatterhoarding by territorial red squirrels: a test of the optimal density model

We observed a high degree of scatterhoarding in a population of red squirrels and tested two predictions of the Optimal Density Model (ODM): (1) large food items will be cached at a greater distance from their source than small items; and (2) caches will be uniformly distributed about their source. Caching experiments supported prediction 1. Red squirrels carried large food items farther than small items before caching them. Prediction 2 was not supported; caches were distributed nonuniformly about their source both within and among caching bouts. We present a simple null model for scatterhoarding, which demonstrates that prediction 1 is not exclusive to the Optimal Density Model. Analyses of our cone-caching data and published data suggested that "optimal densities" were not the primary goal of the caching animal, but rather the result of a positive relationship between food value and investment in caching (carrying distance).

Influences of food particle size and dietary energy content on patterns of gastric evacuation in fish: test of a physiological model of gastric emptying

The evacuation of food from the stomach is probably not a continuous smooth process but may occur in a pulse‐like (step‐wise) fashion. It is hypothesised that the pattern of emptying is influenced by feedback signals from receptors located in the upper intestinal tract and by factors affecting the rate of physical/chemical breakdown of the food particles. Mathematical functions used for describing evacuation patterns imply that emptying is continuous and they are, therefore, at best, only approximations. It was predicted that different mathematical expressions would give best fit to empirical data from gastric evacuation studies dependent upon the experimental conditions employed. An analysis of published data supported the predictions and revealed that an exponential function best described the evacuation of small, easily digested prey items, but a linear expression gave the best fit to data of the emptying of large food items. It is suggested that differences in surface‐to‐volume ratios between large and small food particles and the friabilities of different food types are important in determining the pattern of emptying. Whilst dietary energy content also appears to be an important factor in the governing of gastric evacuation, it appears that emptying pattern in fish species is rather less sensitive to changes in dietary composition than is gastric emptying in mammals.

In Pursuit of Females: Following and Contest Behavior by Males of a Namib Desert Tenebrionid Beetle, Physadesmia globosa

AbstractMale Physadesmia globosa beetles spend much of their active time following females, searching for single females, or contesting with other males for position behind females. Once paired with a female, a male does not feed, can seldom stay paired for more than a few min, and can mate only if the female stops moving. Females rarely stop moving unless they find a large food item, or burrow into the sand and become inactive. Thus, males expend great effort positioning themselves for opportunities to mate, which seldom arise. However, males do not display any alternative mating strategies, and none appear to be available, for females are scarce in relation to males, and do not become receptive to mating at any predictable times or places.

Feeding Structures of Two Atyid Shrimps, with Comments on Caridean Phylogeny

ABSTRACT Atyainnocous and Potimirim glabra (Atyidae) occur in permanent and temporary freshwater streams in the Atlantic and Pacific drainages of Panama. Their mouthparts, mandibles, and foreguts are compared to test the hypothesis that these structures are related to diet. Atya innocous occurs in moderate to fast-flowing streams, feeding on minute particles collected from the water column or bottom. Potimirim glabra inhabits quiet pools, scraping periphyton from leaf surfaces and decaying organic detritus. The feeding appendages of both species arc modified for handling fine particles of food. The mandibles have a strong incisor process but are not used for crushing large food items. The primitive nature of the mandible and foregut suggests the placement of the family Atyidae at the base of the caridean evolutionary tree. The use of the foregut in the construction of phylogenies within the Decapoda is discussed.