Feeding mechanisms, and their variation in form, of some adult ground-beetles (Coleoptera: Caraboidea)

The structure of the mouthparts and foregut of some caraboid beetles has been correlated with their type of feeding mechanism. These may be adapted to fragmentary feeding, fluid feeding (where pre-oral digestion is important), or to mixed feeding (a large category which ranges from a mainly fluid to a mainly solid intake). Head structures concerned with feeding have been discussed in relation to these methods; they include the mandibles, maxillae, labrum-epipharynx and anterior foregut, proventriculus, labium-hypopharynx and the head floor. Different types of head floor were denned in relation to gular structure, in particular the presence or absence of the mid-gular apodeme. Convergent evolution of feeding mechanisms was noted amongst both fragmentary feeders and fluid feeders; in the latter group, sucking pumps have been evolved in the Carabitae, Scarites , Cicindelidae, Paussini and some other caraboids. It was suggested that head shape in caraboids may reflect locomotory adaptations more frequently than feeding adaptations.     

Cranial shape in fruit,nectar, and exudate feeders: Implications for interpreting the fossil record

At least 29 species of fossil primates have been referred to fruit, nectar, and/or exudate feeding dietary niches. Many studies have detailed the morphological correlates of fruit feeding in comparison to insectivory and folivory. In contrast, few studies have sought to differentiate the morphological correlates of fruit feeding from those of nectar and exudate feeding. This study investigates the differences between fruit, nectar, and exudate feeders using 22 cranial and dentary shape variables representing 28 species of living marsupials, bats, and primates. Discriminant function analysis is used to investigate the differences between these dietary categories using both the complete data set and a reduced data set composed of variables that might reasonably be available from fragmentary fossil material. The success rates of post-hoc classifications are 94 and 88%, respectively. These results demonstrate that it is possible to discriminate among fruit, nectar, and exudate feeders among fossil taxa with a reasonable degree of certainty using the data and techniques outlined here. Nectar feeders exhibit a unique combination of features that are associated with reduced masticatory strength and their role as pollination agents. Exudate feeder skulls and dentaries exhibit a combination of features that reflect the high stresses encountered by the anterior dentition through bark gouging behavior. Fruit feeders are morphologically diverse, exhibiting cranial and mandibular shape values that overlap with both nectar and exudate feeders. It is suggested that this diversity reflects the variety of physical properties represented among fruits, and the tendency for individual frugivore species to specialize on particular fruits. Am J Phys Anthropol 102:187–202, 1997 © 1997 Wiley-Liss, Inc.     

Diet of combtooth blennies (Blenniidae) in Kochi and Okinawa,Japan

Combtooth blennies (Blenniidae) have a wide array of diets, including coral polyps, fish scales/mucus/rays, and detritus. However, there is limited knowledge about the diet of some species. We described the diet of 30 blenny species from subtidal, intertidal, or supralittoral habitats in Kochi (warm temperate) and Okinawa (tropical), Japan. Cluster analysis of dietary overlap grouped blennies into seven feeding groups: omnivores, herbivores, detritivores, molluscivores, corallivores, worm-like invertebrate feeders, and fish mucus/scale/ray feeders. The largest cluster, detritivores, contained 17 blenny species from all habitat zones and both climate zones. Our findings suggest that closely related species fill similar feeding niches and detritus is an important component of many blenny diets.     

Oral Fimbriae and Papillae in Parasitic Lampreys (Petromyzontiformes)

There are 38 species of living lampreys, 18 parasitic and 20 nonparasitic. The parasitic species feed as adults, while the nonparasitic do not. The taxonomy and systematics of the living lampreys is based primarily on dentition characters. Since the number of oral fimbriae and oral papillae have never been systematically investigated in lampreys, we compared them in 17 of the 18 parasitic lampreys to assess their usefulness as taxonomic characters. Both showed little variation with total length and sex within a species, while exhibiting greater variation between species. Parasitic species belonging to the three lamprey families could be distinguished using the number of oral fimbriae: southern hemisphere Mordaciidae (0) and Geotriidae (55–65) and northern hemisphere Petromyzontidae (81–144). However, the taxonomic usefulness of the two characters at the species level was limited. Ten out of the 17 species of parasitic lampreys were placed into four distinct groups based on their numbers of oral fimbriae, and only in two of these was the character diagnostic. Twelve out of the 17 species were placed into two distinct groups based on their numbers of oral papillae and for none of these was the character diagnostic. Blood feeders and intermediate feeders (blood + flesh) were shown to have significantly higher numbers of oral fimbriae than flesh feeders. The higher numbers of oral fimbriae in the former two types of feeders were presumed to be linked to their greater need to create a good seal for feeding purposes. Blood feeders were also shown to have significantly higher numbers of oral papillae than either intermediates or flesh feeders. The higher numbers of oral papillae in the blood feeders were presumed to be linked to their greater need to find suitable attachment sites for feeding purposes.     

Xylem feeding by periodical cicada nymphs on tree roots

Abstract. 1. Histological sections of tree roots on which periodical cicada nymphs of both the 17-year and the 13-year race arid various instars had fed showed that salivary sheaths made by the nymphs ended in xylem vessels.
2. Because no salivary sheaths were found in phloem cells, this observation indicates that cicada nymphs are xylem feeders throughout their developmental period.
3. The habit of feeding on xylem fluid, which is extremely dilute, may explain why periodical cicada nymphs require so many years (13 or 17) to mature. It may also explain why they excrete amino acids rather than sugars, as phloem feeders do.     

Feeding behavior of the cichlid,Sarotherodon galilaeum: selective predation on Lake Kinneret zooplankton

In laboratory feeding trials, we analyzed the feeding behavior and selectivity of the cichlid, Sarotherodon galilaeum, for zooplankton prey from Lake Kinneret, Israel. The feeding behavior was dependent on fish size. Fish less than 20 mm SL fed on zooplankton as obligate particulate feeders. Fish from 20 to 42 mm SL fed either as particulate feeders or as filter feeders. Fish larger than 62 mm SL fed as obligate filter feeders. Particulate-feeding fish were size selective and had highest feeding electivities for large-sized zooplankton species. Filter-feeding fish had highest feeding electivities for zooplankton species with poor escape ability. In general, S. galilaeum predation pressure would be greatest on Ceriodaphnia reticulata, a large-bodied and easily captured species which is selected by both particulate-feeding and filter-feeding fish.     

Extraoral and intraoral feeding: flexible foraging tactics in the South American sun-star, Heliaster helianthus

The South American sun-star, Heliaster helianthus , is capable of adopting both the extraoral and intraoral mode of feeding. Observations were made on the feeding activities of H. helianthus in an intertidal habitat in central Peru. The proportion of individuals engaged in intraoral feeding was high amongst small H. heliunthus of less than 14 cm in diameter and gradually declined in larger size classes. Extraoral feeders had significantly larger meal sizes (total prey biomass) than intraoral feeders in all the size categories of H. heliunthus . Extraoral feeders also consumed larger individuals of the most important prey species, Semimytilus algosus , than intraoral feeders. The advantages and disadvantages of the two feeding modes are discussed and the meaning of the dual foraging tactics in H. helianthus is considered.     

Why are there no small species among xylem-sucking insects?

Xylem-sucking herbivores must cope with negative tension and extremely low nutrient concentration of xylem fluid. We test the hypothesis that the energetic cost of xylem fluid extraction grows with decreasing body size, as small species have relatively high metabolic rates and small feeding apparatus. The suction pressure gradient needed for feeding (P), calculated using Poiseuilles Law, and the cibarial pump load (L), estimated as xylem fluid volume per unit volume of cibarial muscles, were used to quantify energetic costs associated with feeding. Interspecific relationships between body size and frontoclypeus (cibarial pump) volume, proboscis length and food canal diameter were quantified using the structural relations model and model I (ordinary) regressions applied on species as data points (phylogeny ignored), and on independent (intrageneric) contrasts (taxonomy used as a surrogate of phylogeny). All the dimensions of feeding apparatus changed approximately isometrically with body volume. In consequence, the suction pressure gradient P (body volume)–0.21, and the cibarial pump load L (body volume)–0.17. These relationships result in an allometric change in energetic costs associated with xylem feeding. Energy needed to overcome the resistance of feeding apparatus (P) becomes negligible for any species longer than about 8mm, and there is an important decrease in the L values in species over about 17mm in body length. These allometric trends can result in large species having a wider range of potential (energetically profitable) host plants than small species. Analysis of body size distributions in xylem-feeding insects, which all belong to the Auchenorrhyncha (Hemiptera), showed that xylem feeders tend to be larger than phloem feeders, especially in terms of the minimum body size. Two evolutionary transitions from phloem to xylem feeding in Hemiptera were associated with an increase in the minimum body size. A possibility that the evolution of minimum body size in xylem feeders is energetically constrained is discussed.     

Impact of grazing and bioturbation of marine benthic deposit feeders on dinoflagellate cysts

The impact of benthic deposit feeders on marine dinoflagellate cysts was studied by adding a concentrated natural Swedish cyst assemblage to sediment with different deposit feeders in replicate 4-l aquaria. The deposit feeders used were the bivalve Abra nitida, the echinoderm Amphiura filiformis, and the polychaetes Melinna cristata and Nereis diversicolor. These species occur naturally near the Swedish west coast and were selected to represent different ways of feeding. The results showed a significant relative decrease of unfossilizable cyst species; whereas, the common fossilizable species Lingulodinium polyedrum significantly increased in the cyst assemblage after grazing. This work suggests that differences in dinoflagellate cyst compositions can in part be caused by different animal grazing behaviors.     

Suction feeding in orchid bees (Apidae: Euglossini)

Energy flux during nectar feeding is maximized at an intermediate sugar concentration, the value of which depends on the morphology of the feeding apparatus and the modality of fluid feeding. Biomechanical models predict that a shift from capillary-based lapping to suction feeding will lead to a decrease in this optimal sugar concentration. Here, I demonstrate that the four major genera of orchid bees (Apidae: Euglossini) are suction feeders and provide experimental evidence that the feeding optimum for one species, Euglossa imperialis, falls below the optimum for bee taxa that lap.     

Feeder design and available feeding space influence the feeding behaviour of hens

This paper describes a study of the influences of feeder design and available feeding space on the feeding behaviour of laying hens.When feeders were partitioned, feeding rates and the number of feeding bouts were higher than when the feeders were unpartitioned, but feed consumption was lower and the duration of feeding was shorter. Increased feeding space led to longer feeding times with fewer but longer feeding bouts. These results are discussed in relation to animal welfare, with particular reference to feather-pecking.     

Community structure and food web based on stable isotopes (δN and δC) analysis of a North Eastern Atlantic maerl bed

Maerl beds are highly biodiverse biogenic substrata that have been receiving increasing attention in the last decade. Although maerl beds represent important nursery areas for commercial fishes and molluscs, little is known on the trophic web of their communities. Community structure parameters of maerl bed of the Bay of Brest (species richness, abundance, biomass and dominating species) were studied in parallel with the carbon and nitrogen isotopic composition of their main benthic species (macrofaunal, and megafaunal organisms) in order to assess the trophic levels and differences in the potential food sources of maerl inhabitants. The major potential sources of energy were identified to originate either from epiphytic macroalgae and microphytobenthos both growing on maerl thalli, together with sedimenting (sedimentary) particulate organic matter (POM) originating from the water column. The majority of the macro- and megafaunal organisms investigated were filter feeders, selective-deposit feeders and predators/scavengers. Filter feeders fall into three different groups representing different trophic pathways (i) sponges feeding directly on POM (water column filter feeders I), (ii) ascidians and holothurians feeding on POM and probably captured pelagic preys (water column filter feeders II), and (iii) filter feeding molluscs and crustaceans were hypothesised to feed on microphytobenthos or on decaying sedimented POM (Interface filter feeders). Selective deposit feeders were also divided into two subgroups. Carnivores were also distinguished between those with scavenging habits and true predators. Coupling of the trophic levels observed with the community biomass structure revealed that most of the benthic biomass derives its food from detritic sedimented POM and/or microphytobenthos, with interface filter feeders (23% of the biomass), selective deposit feeders (12%). Carnivores made up to 14% of the total biomass. Generally stable isotopes ratio mean values overlap and cover a large range within feeding types, indicating a strong overlap in food sources and a high degree of complexity of the food web presumably due to the diversity of the potential food sources.     

Adult feeding time, lipid accumulation, and overwintering in Aglais urticae and Inachis io (Lepidoptera: Nymphalidae)

The influence of restricted feeding time on the subsequent survival of adult Aglais urticae and Inachis io during diapause was tested in the laboratory. Abdominal lipid weight increased in the first 7 days of feeding by A. urticae and up to day 15 in I. io. Lipid as a proportion of dry weight also increased during this time. Individuals of both species feeding for 0–3 days began overwintering at significantly lower weights, and percentage weight loss during overwintering was more rapid than for those feeding for longer periods. Differences in fresh weights at the beginning of the overwintering period are reflected by differences in overwintering survival. In A. urticae , all 0–3 day feeders died in less than 150 days, in contrast, over 75% of 7–30 day feeders survived this period. In I. io , all 0–1 day feeders died within 160 days, less than 50% of 3 day feeders survived, whilst over 90% of7–15 day feeders were alive after this time. In I. io individuals feeding for one day, fresh weight is correlated with survival time suggesting that a larger body size may enhance survival time if feeding time is restricted.     

Feeding habits of Japanese butterfyfishes (Chaetodontidae)

Synopsis Stomach content data from 32 species of Japanese butterflyfishes of the family Chaetodontidae were used to classify them into feeding groups and to determine their important food resources. Four major feeding groups were distinguished: (1) obligative coral feeders which prey exclusively or mostly on Scleractinian corals, (2) facultative coral feeders that take both corals and other benthic organisms, (3) noncoralline invertebrate feeders which consume benthic invertebrates other than corals, and (4) zooplankton feeders. Ten species representing 31% of the butterflyfishes belong to the first category. The second and third categories include 13 (41%) and 8 (25%) species, respectively. The fourth category is represented by only one species which picks individual zooplankters, especially calanoid copepods, in midwater above the reefs. Facultative coral feeders consumed varying quantities of scleractinians (from 2 to 74% of food volume), along with a variety of benthic organisms including algae, alcyonarians, sea anemones, sedentary polychaetes, sponges, hydroids, etc. Noncoralline invertebrate feeders, on the other hand, tend to have low diversified diets, predominated by one prey item such as sea anemones, zoanthideans, polychaetes, or colonial ascidians. These dietary data suggest that scleractinian corals are the most important food resource for the Japanese butterflyfishes, and next important are sea anemones, sedentary polychaetes, alcyonarians, and algae.     

Evolution of regulatory responses to feeding in snakes

Do animal species that normally consume large meals at long intervals evolve to down-regulate their metabolic physiology while fasting and to up-regulate it steeply on feeding? To test this hypothesis, we compared postfeeding regulatory responses in eight snake species: four frequent feeders on small meals and four infrequent feeders on large meals. For each species, we measured factorial changes in metabolic rate, in activities and capacities of five small intestinal brush border nutrient transporters, and in masses of eight organs that function in nutrient processing after consumption of a rodent meal equivalent to 25% of the snake's body mass. It turned out that, compared with frequent feeders, infrequent feeders digest that meal more slowly; have lower metabolic rates, organ masses, and nutrient uptake rates and capacities while fasting; have higher energy expenditure during digestion; and have higher postfeeding factorial increases in metabolic rate, organ masses, and nutrient uptake rates and capacities. These conclusions, which conform to the hypothesis mentioned above, remain after phylogeny has been taken into account. The small organ masses and low nutrient transporter activities during fasting contribute to the low fasting metabolism of infrequent feeders. Quantitative calculations of partial energy budgets suggest that energy savings drive the evolution of low mass and activities of organs during fasting and of large postfeeding regulatory responses in infrequent feeders. We propose further tests of this hypothesis among other snake species and among other ectotherms.     

Cambrian cinctan echinoderms shed light on feeding in the ancestral deuterostome

Reconstructing the feeding mode of the latest common ancestor of deuterostomes is key to elucidating the early evolution of feeding in chordates and allied phyla; however, it is debated whether the ancestral deuterostome was a tentaculate feeder or a pharyngeal filter feeder. To address this, we evaluated the hydrodynamics of feeding in a group of fossil stem-group echinoderms (cinctans) using computational fluid dynamics. We simulated water flow past three-dimensional digital models of a Cambrian fossil cinctan in a range of possible life positions, adopting both passive tentacular feeding and active pharyngeal filter feeding. The results demonstrate that an orientation with the mouth facing downstream of the current was optimal for drag and lift reduction. Moreover, they show that there was almost no flow to the mouth and associated marginal groove under simulations of passive feeding, whereas considerable flow towards the animal was observed for active feeding, which would have enhanced the transport of suspended particles to the mouth. This strongly suggests that cinctans were active pharyngeal filter feeders, like modern enteropneust hemichordates and urochordates, indicating that the ancestral deuterostome employed a similar feeding strategy.     

Egg size, first instar behaviour and the ecology of Lepidoptera

There is striking variation in egg size among Lepidoptera. Part of the explanation could be a link between egg size and larval feeding ecology.
The relationship between absolute egg size and aspects of feeding ecology for different Lepidoptera families from different temperate regions is examined. Species that overwinter in the egg stage have larger eggs. There are significant differences in egg size with respect to feeding specificity but different families show different patterns. Woody plant feeders have larger eggs than herb feeders. There is little effect of proximity of the egg to the plant part that is eaten.
Patterns in the behaviour and survival of newly hatched larvae of 42 spp. of British Lepidoptera and their relationship to egg and larval size and to food plant characteristics are examined. Patterns in egg size with respect to feeding ecology are similar to those described above. There is a strong correlation between egg size and the size of newly hatched larvae. Newly hatched larvae survived for a mean of 1–20 days without food. Survival is not correlated with larval weight. Grass feeders survive longer than herb and woody plant feeders; the species surviving the longest feeds on lichens. Newly hatched larvae moved at a mean speed of 0.7-267.8 cm h^-1. Speed is not correlated with larval weight or survival time. Grass feeders move faster than woody plant feeders which, in turn, move faster than herb feeders. Woody plant feeders tend to move upwards, grass feeders downwards and herb feeders both upwards and downwards. The proportion of larvae silking is negatively correlated with larval weight.
The strong links between egg size and larval feeding ecology and between feeding ecology and larval behaviour are discussed. It is surprising that larval body size does not appear to constrain the speed of movement, nor tolerance to starvation.     

A New Angle on Microscopic Suspension Feeders near Boundaries

Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces they live upon, whereas we observe that sessile suspension feeders often feed at an angle to these boundaries. Using experiments and calculations, we show that living suspension feeders (Vorticella) likely actively regulate the angle that they feed relative to a substratum. We then use theory and simulations to show that angled feeding increases nutrient and particle uptake by reducing the reprocessing of depleted water. This work resolves an open question of how a key class of suspension-feeding organisms escapes physical limitations associated with their sessile lifestyle.     

A New Angle on Microscopic Suspension Feeders near Boundaries

Microscopic sessile suspension feeders are a critical component in aquatic ecosystems, acting as an intermediate trophic stage between bacteria and higher eukaryotic taxa. Because they live attached to boundaries, it has long been thought that recirculation of the feeding currents produced by sessile suspension feeders inhibits their ability to access fresh fluid. However, previous models for the feeding flows of these organisms assume that they feed by pushing fluid perpendicular to surfaces they live upon, whereas we observe that sessile suspension feeders often feed at an angle to these boundaries. Using experiments and calculations, we show that living suspension feeders (Vorticella) likely actively regulate the angle that they feed relative to a substratum. We then use theory and simulations to show that angled feeding increases nutrient and particle uptake by reducing the reprocessing of depleted water. This work resolves an open question of how a key class of suspension-feeding organisms escapes physical limitations associated with their sessile lifestyle.     

Fish feeding guilds in shallow rocky and soft bottom areas on the Swedish west coast

Multivariate analyses of the diet relationships within fish assemblages resulted in the recognition of five major feeding guilds in shallow (0-9 m) rocky- and soft-bottom habitats on the Swedish west coast. The two habitats had similar guilds that could be broadly described as piscivores, decapod feeders, copepod feeders and amphipod and mollusc feeders. The last guild on the rocky bottom was more strictly one of amphipod feeders, whereas the last guild on soft bottoms consisted of infauna feeders (mainly polychaetes and bivalves). A comparison of the diet of the entire fish assemblages showed that amphipods and gastropods were more prevalent as prey taxa on rocky bottoms, whereas bivalves and teleosts were more common on soft bottoms. A large proportion (12 out of 27 species) of the fish species investigated was found in both habitats. These fish species generally seemed to rely on the same major prey groups in the two habitats, but also included prey taxa characteristic for the habitat in which they resided. Sea trout Salmo trutta , mackerel Scombrus scombrus , saithe Pollachius virens , whiting Merlangius merlangus and cod Gadus morhua were found to be the major piscivores in both the investigated habitats. Herring Clupea harengus and members of the family gobiidae were the most prevalent prey species for piscivores within the rocky- as well as the soft-bottom fish assemblage. A comparison of feeding modes suggested that the fish assemblage on rocky bottoms predominantly (60% of the food items) relied on food found in vegetation. On soft bottoms, the average distribution of food categories among fish species was 44% benthic, 35% pelagic and 21% vegetation-associated food items.