Feeding Success Research Articles

A forceful upper jaw facilitates picking-based prey capture: biomechanics of feeding in a butterflyfish, Chaetodon trichrous

Biomechanical models of feeding mechanisms elucidate how animals capture food in the wild, which, in turn, expands our understanding of their fundamental trophic niche. However, little attention has been given to modeling the protrusible upper jaw apparatus that characterizes many teleost species. We expanded existing biomechanical models to include upper jaw forces using a generalist butterflyfish, Chaetodon trichrous (Chaetodontidae) that produces substantial upper jaw protrusion when feeding on midwater and benthic prey. Laboratory feeding trials for C. trichrous were recorded using high-speed digital imaging; from these sequences we quantified feeding performance parameters to use as inputs for the biomechanical model. According to the model outputs, the upper jaw makes a substantial contribution to the overall forces produced during mouth closing in C. trichrous. Thus, biomechanical models that only consider lower jaw closing forces will underestimate total bite force for this and likely other teleost species. We also quantified and subsequently modeled feeding events for C. trichrous consuming prey from the water column versus picking attached prey from the substrate to investigate whether there is a functional trade-off between prey capture modes. We found that individuals of C. trichrous alter their feeding behavior when consuming different prey types by changing the timing and magnitude of upper and lower jaw movements and that this behavioral modification will affect the forces produced by the jaws during prey capture by dynamically altering the lever mechanics of the jaws. In fact, the slower, lower magnitude movements produced during picking-based prey capture should produce a more forceful bite, which will facilitate feeding on benthic attached prey items, such as corals. Similarities between butterflyfishes and other teleost lineages that also employ picking-based prey capture suggest that a suite of key behavioral and morphological innovations enhances feeding success for benthic attached prey items.

Food and feeding of Argentine hake (Merluccius hubbsi) larvae in the Patagonian nursery ground

Feeding success during the early life stages of fish is one of the main factors that determines recruitment and stock fluctuations. In the Argentine Sea, the Patagonian stock of Merluccius hubbsi is the most important in biomass, spawning from December to April in the north Patagonian shelf region (43–45°30′). Since previous knowledge about larval feeding of the species in this region is fragmentary, adequate information is required for a complete assessment of its importance in the food web and its effect upon recruitment. Our primary objective was to examine the feeding strategy of M. hubbsi larvae in relation with prey availability in the nursery ground. Feeding incidence was 87%; hake larvae consumed mainly calanoid copepodites <2mm in size, which were preferred prey upon more available items, and that may be nutritionally beneficial for larvae. Hake larvae were specialist at a population level toward such prey, with a narrow trophic niche. There was a clear trophic diel pattern in the number of prey ingested. Results indicate that the nursery area might be favorable for a successful feeding of hake larvae while they grow and develop. Data provided here are relevant not only to determine trophic interactions in the region but also to identify possible causes of recruitment success.

Spatio-temporal Variability in Larval-Stage Feeding and Nutritional Sources as Factors Influencing Striped Bass (Morone saxatilis) Recruitment Success

Prey availability and feeding success affect survival of larval striped bass (Morone saxatilis) in Chesapeake Bay and contribute to the >30-fold interannual recruitment variability. Gut contents and stable isotope analyses (δ15N and δ13C) were conducted on striped bass larvae to evaluate sources of nutrition in 2007 and 2008, years of high and poor recruitment, respectively. Ichthyoplankton and zooplankton were surveyed in the upper Chesapeake Bay, in proximity to the estuarine turbidity maximum and associated salt front. Feeding incidence and numbers of prey per gut were similar in both years and varied in relation to the salt front. The primary prey in each year was the estuarine copepod Eurytemora affinis. Substantial consumption of the freshwater cladoceran Bosmina spp. also occurred, especially up-estuary of the salt front in 2007, demonstrating that secondary prey are important to larval diets in some years. Stable isotope analysis of yolk sac and feeding-stage larvae of striped bass revealed an ontogenetic shift from maternal stable isotope signatures to those indicative of prey source. Feeding-stage larvae from up-estuary locations had the most negative δ13C values, indicating a relatively high terrestrial carbon source in prey. Spatio-temporal variability in δ15N signatures of larvae followed similar trends of δ15N variability in zooplankton prey with the highest δ15N values up-estuary of the salt front and estuarine turbidity maximum. A stable isotope analysis on archived striped bass larvae collected in 1998 and 2003, years of moderate and high recruitment, respectively, expanded the documented range of isotope signatures but did not clearly distinguish effects of nutritional sources on recruitment.

Impact of the diatom-derived polyunsaturated aldehyde 2-trans,4-trans decadienal on the feeding, survivorship and reproductive success of the calanoid copepod Temora stylifera

Many diatoms, a major class of unicellular algae contributing to over 45% of oceanic primary production, are known to induce deleterious effects on reproductive processes in crustacean copepods. This is mainly due to the production of teratogenic oxylipins, including polyunsaturated aldehydes (PUAs). Here we tested the direct effect of the PUA 2E,4E-decadienal (DD) on feeding activity, survivorship and reproductive success of the calanoid copepod Temora stylifera. DD-inoculated cultures induced high mortality at concentrations above 3 μg mL−1 compared to controls in both males and females, with males having a higher mortality. Low DD concentrations triggered an increase in female filtration and ingestion rates. Egg production rates and hatching times were also higher in the presence of DD, whereas egg hatching success decreased with increasing DD concentration. Our study shows, for the first time, that the presence of diatom PUAs may increase feeding rates in copepods.

The Habitat Use and Home Range Analysis of Dunlin (Calidris alpina) in Chongming Dongtan, China and their Conservation Implications

Natural coastal wetlands are important habitats for shorebirds while flooded agricultural croplands, may also be useful habitats. Shorebirds in East Asia utilize an often highly developed coastal landscape, which may be dissected by seawalls with intertidal flats on the seaward side, and aquaculture ponds and agricultural croplands on the landward side. Little is known about the value of aquaculture ponds to shorebirds. We investigated the habitat use, preference and home range of wintering Dunlin (Calidris alpina) in Chongming Dongtan, east China, through radio tracking and field observations in 2006–2007. Our results indicated that Dunlins preferred tidal flats, avoided agricultural croplands, and used aquaculture ponds in proportion to their availability. The probability of Dunlin usage of aquacultural ponds decreased with increasing size of unflooded area in the aquaculture ponds. Dunlins foraging in aquaculture ponds had lower feeding success rate than those in tidal flats. Thus, tidal flats may provide important foraging habitats for wintering Dunlins, while aquaculture ponds may provide alternative roosting and supplemental foraging habitat. Conserving the natural wetlands on tidal flats is vital for shorebird conservation in East Asia but at the same time, the aquaculture ponds also could play an important role if managed properly.

New Synthesis: Investigating Mutualisms in Virus-Vector Interactions

Most plant viruses depend on insect vectors for transmission from one host to another. Aphids are the most notable among these insect vectors, transmitting more than half of all described virus species. Virus transmission ranges from simple attachment to the tip of the aphid stylets tomore complicated interactions that involve ingestion of the viruses, passage through the haemolymph to the salivary glands, and subsequent injection into a new host plant. Plant viruses, which clearly benefit from being transported to new hosts, generally do not harm their aphid vectors. To the contrary, the frequent observation of improved aphid growth on virus-infected plants suggests that these interactions can be mutualistic, benefitting both the viruses and their insect vectors. Several studies have demonstrated that plant viruses manipulate plants, thus increasing the number of inoculated insect vectors. This can be accomplished by attracting aphids to infected plants and/or changing plant physiology in a manner that improves aphid reproduction. Increased fecundity and developmental rate of aphids on virus-infected plantswill result in greater dispersal of viruliferous aphids tonewhosts as host plant qualitydeclines andaphids becomecrowded.Crowding also induces the formation of alate aphids, which provide longer-distance virus transmission. Virus-vector interactions can be mediated indirectly by virusinduced increases in plant nutritive value, suppression of plant defense responses, or some combination of these effects. Recent publications provide evidence for active manipulation of herbivore defenses by plant-pathogenic viruses. For instance, the 2b silencing suppressor protein of cucumber mosaic virus compromises jasmonate-regulated insect defenses and improves performance of Myzus persicae (green peach aphid; Lewsey et al. 2010). Similarly, pathogenicity factor βC1, which is encoded in the betasatellite of tomato yellow leaf curl China virus, suppresses jasmonate-mediated defenses and improves growth of Bemisia tabaci (silverleaf whitefly) on Nicotiana tabacum (Zhang et al. 2012). Because arthropod-mediated transmission benefits plant viruses, and there is an apparent reproductive benefit for the insects, in many cases, the virus-vector interaction can be considered a mutualism. For instance, individual aphids that transport viruses to a new host plant would benefit from rapid virus-mediated suppression of plantdefenses. In suchasituation, it clearlywouldbeadvantageous foraphids topick up and transmit viruses. It is also possible that, by transmitting plant-pathogenic viruses, hemipteran insects can expand their ranges to include normally unsuitable host plants.Our ownunpublishedobservations show that, ifNicotiana benthamiana is infected with turnip mosaic virus, the survival of newly arrivingMyzus persicae (green peach aphids) increases from 30% to 90%. Similarly,N. tabacum is a poor host for some B. tabaci biotypes, but whitefly performance is improved greatly through prior begomovirus infection (Zhang et al. 2012). If an insect vector arriving at an uninfected plant benefits from being viruliferous, this suggests that such insects will benefit by acquiring viruses prior to moving to new host plants. For instance, aphids could be feeding from virus-infected tissue in a targetedmanner, or specifically selecting virus-infected cells as they are probing to reach the phloem. When an aphid punctures a cell infected with cauliflower mosaic virus, the virus rearranges itself rapidly, thereby promoting attachment to the aphid stylets (Martiniere et al. 2013). It has been suggested that this is due to viral recognition of some component of the plant defense signaling pathway that is triggered by aphid feeing. However, it also is possible that the aphids acquire viruses by actively manipulating plant cellular metabolism. Conversely, when a viruliferous aphid settles on a new plant, its feeding success may be promoted if viruses are deposited in a cellular location that allows rapid replication and thereby suppression of plant defenses. To date, most research on the molecular mechanisms of virus-vector interactions has focused on studying host plant manipulation by viruses that promotes aphid performance. However, aphids and other insect vectors also may promote virus transmission by altering plant physiology. To initiate progress in this research area, it will be necessary to identify conditions under which there are immediate benefits to insect vectors carrying viruses to newhost plants. Furthermore, future investigation of these ecologically important but relatively under-investigated three-way interactions should include a greater focus on discovering behavioral and molecular mechanisms by which insect vectors can actively manipulate plant-virus interactions for their own benefit.

Prey Selectivity of Fraser River Sockeye Salmon during Early Marine Migration in British Columbia

AbstractMortality of salmon during early marine life has long been thought to be a critical factor in limiting overall abundance. One of the key hypotheses proposed to explain the long‐term productivity decline of Canada's iconic Fraser River Sockeye Salmon Oncorhynchus nerka, is deficient habitat conditions experienced during early marine life. Our study is a first step towards testing this hypothesis, with an aim of understanding food availability and prey choice of juvenile salmon early in their coastal migration. We investigated zooplankton density, diet composition, and foraging selectivity of juvenile Fraser Sockeye Salmon during the 2009 and 2010 migrations and determined whether the timing of their migration was related to feeding success. Sockeye Salmon diets showed high prey diversity and a preference for euphausiid, amphipod, decapod, terrestrial insect, fish, egg, and cumacean prey. Calanoid copepods, the most abundant available prey, were not strongly selected in either year. Zooplankton densities were highest in the tidally mixed Discovery Passage–Johnstone Strait area. The fish appeared to have an adequate prey resource pool during their early marine migration, and in the 2 years of our study we observed similar feeding success throughout the migration period. Importantly, we found no evidence of food limitations that might indicate that juveniles suffered food deprivation. Further research is needed to test the generality of these findings, including the potential impacts of warming ocean temperatures on the timing and availability of prey during migration.

Feeding habits and diet overlap of marine fish larvae from the peri-Antarctic Magellan region

The Magellan region is a unique peri-Antarctic ecosystem due to its geographical position. However, the knowledge about the distribution and feeding ecology of fish larvae is scarce. Since this area is characterized by low phytoplankton biomass, we hypothesize that marine fish larvae display different foraging tactics in order to reduce diet overlap. During austral spring 2009–2010, two oceanographic cruises were carried out along southern Patagonia (50–56°S). Larval fish distribution and feeding of the two most widely distributed species were studied, the smelt Bathylagichthys parini (Bathylagidae) and black southern cod Patagonotothen tessellata (Nototheniidae). Larvae of B. parini showed a lower increase in the mouth gape at size, primarily feeding during daytime (higher feeding incidence during the day) mostly on nonmotile prey (invertebrate and copepod eggs, appendicularian fecal pellets, diatoms). They showed no increase in feeding success (number, total volume of prey per gut and prey width) with increasing larval size, and the niche breadth was independent of larval size. Larvae of P. tessellata showed a large mouth gape at size, which may partially explain the predation on motile prey like large calanoid copepods (C. simillimus) and copepodites. They are nocturnal feeders (higher feeding incidence during night) and are exclusively carnivorous, feeding on larger prey as the larvae grow. Nonetheless, niche breadth was independent of larval size. Diet overlap was important only in individuals with smaller mouth gape (<890 μm) and diminished as larvae (and correspondingly their jaw) grow. In conclusion, in the peri-Antarctic Magellan region, fish larvae of two species display different foraging tactics, reducing their trophic overlap throughout their development.

Green crab (Carcinus maenas (Linnaeus, 1758)) foraging on soft-shell clams (Mya arenaria Linnaeus, 1758) across seagrass complexity: Behavioural mechanisms and a new habitat complexity index

Although many studies have examined foraging success across seagrass complexity, few have identified underlying behavioural mechanisms or examined effects of belowground complexity. Here, I used a new habitat complexity index (IBG), behavioural data, and laboratory manipulations of artificial above- and belowground structures and predator sizes to understand foraging of invasive green crabs (Carcinus maenas) on soft-shell clams (Mya arenaria) in seagrass (Zostera marina) beds. IBG was calculated as interstitial area between rhizomes (i.e., belowground complexity) divided by claw area; belowground complexity was varied while claw area was held constant. This meant that as IBG increased, belowground complexity itself decreased. Belowground complexity strongly affected crab foraging, and a sigmoid function described predation rate across increasing IBG. This relationship was not evident when aboveground complexity was high (i.e., interstitial area between shoots was small), and no patterns in predation across a gradient of aboveground complexity were observed. Important behavioural mechanisms included encounter rate with prey and the probability of capture upon encounter, both of which increased hyperbolically as IBG increased, and handling time per prey, which decreased exponentially as IBG increased. Most handling time was spent excavating prey from the sediments. Predator size did not change these relationships, although larger crabs had more difficulty capturing prey at low IBG than smaller crabs. Clearly, success of crabs feeding on infauna in seagrass beds is limited most by claw size relative to opening size from which prey are extracted. IBG incorporates this limitation, and can be used to predict effects of habitat complexity on foraging success of epibenthic predators in various habitat types.

Feeding ability of a fluvial habitat-specialist and habitat-generalist fish in turbulent and still conditions

Species termed 'habitat-generalists' are able to survive across a wide range of habitats, potentially enabled by the plastic behaviours and morphologies of individuals. This study aimed to compare habitat-related adaptive specialisation in habitat-generalists and specialists, by comparing feeding abilities of fish under varied hydrodynamic conditions. We compared the proportion of prey consumed by a New Zealand fluvial habitat- specialist, the redfin bully, to a closely related habitat-generalist found in fluvial and lacustrine habitats, the common bully, over a 6-h period in either still or turbulent aquaria. We tested for intraspecific habitat-specific adaptations by comparing feeding of common bullies from habitats with different hydrodynamic conditions. Within common bullies, previous research has documented a pattern of more lateral-line system oculoscapular canal pores in fluvial habitats compared to lacustrine ones. By testing for a relationship between total pores and feeding success, we also aimed to identify the adaptive value of an increase in pores in turbulence. We identified decreased feeding (i.e., proportion of prey consumed) by both species in turbulence, but less so for redfin bullies. There was no clear indication of adaptation to habitat type by common bullies, with high variability in feeding by fish from all locations. We also found no statistical relationship between feeding and total oculoscapular canal pores. The results of this study suggest specialised adaptations of a habitat-specialist to turbulent environments. The variability in feeding activity of common bullies also suggests the importance of behavioural plasticity in the survival of a habitat-generalist across a wide range of conditions.

Impact of swimming behaviour and nutrient limitation on predator–prey interactions in pelagic microbial food webs

Heterotrophic dinoflagellates are motile protozoans, important consumers of phytoplankton in aquatic environments. Motility is a main advantage for predators during grazing activities, but can also serve as defence mechanisms against being grazed. Thus, numerous microalgal species are also motile. We hypothesise that the nutrient status of an organism affects its swimming speed and especially that nutrient limitation has a negative impact on cell motility. Such altered motility of both predator and prey should influence feeding success of grazers. We tested those hypotheses by investigating the impact of nutrient (phosphorus) limitation on motility of two algal species, Rhodomonas salina and Teleaulax sp., and the heterotrophic dinoflagellate Oxyrrhis marina and examined how differences in prey swimming speed affect grazing of O. marina. We show that nutrient limitation had a strong impact, reducing algal swimming speed and escape success and in turn significantly influencing food uptake of O. marina which was maximal for intermediate prey swimming speed. We also tested the importance of algal behaviour on O. marina selective feeding and observed that Teleaulax sp. presented an escape behaviour, which appeared to be an effective defence mechanism against grazing of O. marina. While this study has focused on the trophic interactions between two algal species and one dinoflagellate, the impact of nutrient limitation and escape strategy on feeding success of the predator is likely to be found in the whole range of plankton trophic interactions.

Size and biomechanic properties of diatom frustules influence food uptake by copepods

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 481:41-51 (2013) - DOI: https://doi.org/10.3354/meps10227 Size and biomechanic properties of diatom frustules influence food uptake by copepods L. Friedrichs1,*, M. Hörnig1, L. Schulze1, A. Bertram1, S. Jansen1, C. Hamm1,2 1Alfred-Wegener-Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany 2Institute for Marine Resources GmbH, Bussestr. 27, 27570 Bremerhaven, Germany *Email: lars.friedrichs@awi.de ABSTRACT: Diatoms are encased within sophisticated stable lightweight silica cell walls. These frustules have the potential to protect the algal cell against the feeding tools of their most abundant metazoan predators, the copepods. We examined the mechanical strengths of the 3 North Sea diatom species Actinoptychus senarius, Thalassiosira punctigera and Coscinodiscus wailesii and their effect on feeding efficiency of copepods. (1) We determined the stability of the diatoms by means of ‘micro-crush-tests’ performed in the laboratory with calibrated microneedles. (2) In feeding experiments, we compared the ability and efficiency of the 3 North Sea copepod species Temora longicornis, Centropages hamatus and Acartia clausi to crush frustules. The results showed a remarkable correlation between mechanical properties and size of diatom frustules and feeding success of the copepods. The weakly silicified diatom T. punctigera was the least stable and best fed upon, whilst having the highest growth rate. The diatoms having the most complex frustule, A. senarius, exhibited the greatest stability, whilst being fed upon least. The largest diatom, C. wailesii, was partially protected by its size, but was nonetheless suitable as prey for the large copepods that, in the case of C. hamatus, seem to have developed special feeding techniques to overcome the size-mediated protection. KEY WORDS: Diatoms · Copepods · Frustules · Functional morphology · Feeding experiments · Mechanical protection · Co-evolution Full text in pdf format PreviousNextCite this article as: Friedrichs L, Hörnig M, Schulze L, Bertram A, Jansen S, Hamm C (2013) Size and biomechanic properties of diatom frustules influence food uptake by copepods. Mar Ecol Prog Ser 481:41-51. https://doi.org/10.3354/meps10227 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 481. Online publication date: May 07, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Feeding behaviour and digestive physiology in larval fish: current knowledge, and gaps and bottlenecks in research

AbstractFood uptake follows rules defined by feeding behaviour that determines the kind and quantity of food ingested by fish larvae as well as how live prey and food particles are detected, captured and ingested. Feeding success depends on the progressive development of anatomical characteristics and physiological functions and on the availability of suitable food items throughout larval development. The fish larval stages present eco‐morpho‐physiological features very different from adults and differ from one species to another. The organoleptic properties, dimensions, detectability, movements characteristics and buoyancy of food items are all crucial features that should be considered, but is often ignored, in feeding regimes. Ontogenetic changes in digestive function lead to limitations in the ability to process certain feedstuffs. There is still a lack of knowledge about the digestion and absorption of various nutrients and about the ontogeny of basic physiological mechanisms in fish larvae, including how they are affected by genetic, dietary and environmental factors. The neural and hormonal regulation of the digestive process and of appetite is critical for optimizing digestion. These processes are still poorly described in fish larvae and attempts to develop optimal feeding regimes are often still on a ‘trial and error’ basis. A holistic understanding of feeding ecology and digestive functions is important for designing diets for fish larvae and the adaptation of rearing conditions to meet requirements for the best presentation of prey and microdiets, and their optimal ingestion, digestion and absorption. More research that targets gaps in our knowledge should advance larval rearing.

Bite force is limited by the force–length relationship of skeletal muscle in black carp,Mylopharyngodon piceus

Bite force is critical to feeding success, especially in animals that crush strong, brittle foods. Maximum bite force is typically measured as one value per individual, but the force-length relationship of skeletal muscle suggests that each individual should possess a range of gape height-specific, and, therefore, prey size-specific, bite forces. We characterized the influence of prey size on pharyngeal jaw bite force in the snail-eating black carp (Mylopharyngodon piceus, family Cyprinidae), using feeding trials on artificial prey that varied independently in size and strength. We then measured jaw-closing muscle lengths in vivo for each prey size, and then determined the force-length relationship of the same muscle in situ using tetanic stimulations. Maximum bite force was surprisingly high: the largest individual produced nearly 700 N at optimal muscle length. Bite force decreased on large and small prey, which elicited long and short muscle lengths, respectively, demonstrating that the force-length relationship of skeletal muscle results in prey size-specific bite force.

Whale watching disrupts feeding activities of minke whales on a feeding ground

Human disturbances of wildlife, such as tourism, can alter the activities of targeted individuals. Repeated behavioural disruptions can have long-term consequences for individual vital rates (survival and reproduction). To manage these sub-lethal impacts, we need to understand how activity disruptions can influence bioenergetics and ultimately individual vital rates. Empirical studies of the mechanistic links between whale-watching boat exposure and behavioural variation and vital rates are currently lacking for baleen whales (mysticetes). We compared minke whale Balaenoptera acutorostrata behaviour on a feeding ground in the presence and absence of whale-watching boats. Effects on activity states were inferred from changes in movement metric data as well as the occurrence of surface feeding events. Linear mixed effects models and generalised estimation equations were used to investigate the effect of whale-watching boat interactions. Measurement errors were quantified, and their effects on model parameter estimates were investigated using resampling methods. Minke whales responded to whale-watching boats by performing shorter dives and increased sinuous movement. A reduction in the probability of observing longer inter-breath intervals during sinuous movement showed that whale-watching boat interactions reduced foraging activity. Further, the probability of observing surface feeding events also decreased during interactions with whale-watching boats. This indicates that whalewatching boats disrupted the feeding activities of minke whales. Since minke whales are capital breeders, a decrease in feeding success on the feeding grounds due to whale-watching boats could lead to a decrease in energy available for foetus development and nursing on the breeding grounds. Such impact could therefore alter the calving success of this species.

The impact of host species and vector control measures on the fitness of African malaria vectors

Many malaria vector mosquitoes in Africa have an extreme preference for feeding on humans. This specialization allows them to sustain much higher levels of transmission than elsewhere, but there is little understanding of the evolutionary forces that drive this behaviour. In Tanzania, we used a semi-field system to test whether the well-documented preferences of the vectors, Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) for cattle and humans, respectively, are predicted by the fitness they obtain from host-seeking on these species relative to other available hosts. Mosquito fitness was contrasted, when humans were fully exposed and when they were protected by a typical bednet. The fitness of both vectors varied between host species. The predicted relationship between host preference and fitness was confirmed in An. arabiensis, but not in An. gambiae s.s., whose fitness was similar on humans and other mammals. Use of typical, imperfect bednets generated only minor reductions in An. gambiae s.s. feeding success and fitness on humans, but was predicted to generate a significant reduction in the lifetime reproductive success of An. arabiensis on humans relative to cows. This supports the hypothesis that such human-protective measures could additionally benefit malaria control by increasing selection for zoophily in vectors.

Feeding performance of juvenile hatchery‐reared spotted seatrout Cynoscion nebulosus

The feeding performance of individual hatchery-reared (HR) and wild juvenile spotted seatrout Cynoscion nebulosus was compared across a series of six 1·5 h feeding exposures over a 3 day period in a controlled experiment. The predation cycle served as a context for discerning feeding performance elements. The experimental design facilitated assessments of the effects of experience, motivation due to hunger or satiation and prey density and encounter frequency. Although feeding success improved significantly across successive trials for both groups of C. nebulosus, wild C. nebulosus successfully captured and consumed significantly more Palaemonetes spp. prey and completed most performance metrics more efficiently than HR C. nebulosus. Total exposure time decreased with experience for both groups of C. nebulosus; however, HR C. nebulosus took longer to complete feeding exposures. Underpinning this difference was the time spent by HR C. nebulosus in non-search mode and for completing various foraging behaviours. Nevertheless, juvenile HR C. nebulosus exhibited sufficient foraging plasticity to switch from a pelleted diet to live novel prey.

Infectra®-kit: A device for restraining mice and confining tsetse flies during trypanosome infection transmission experiments

Chemical (anaesthesia) and manual techniques are commonly used to restrain mice during vector-mediated parasite transmission experiments in the laboratory. Chemical restraint may interfere with natural fly vector–mouse interactions and therefore potentially affect the outcome of transmission experiments. Conversely, manual restraint is labour-intensive and exposes laboratory animals to excessive restraining-related discomfort. We report development of a mouse restraining device (Infectra®-kit) that allows essential transmission studies to be carried out with minimal human manipulation and without the need for anaesthesia. Infectra®-kit can be used as a single unit for restraining one mouse or as eight-assembled units, thus significantly improving efficiency of a single operator in comparison to manual restraint. The kit was validated by comparing feeding success in tsetse flies fed on mice restrained using Infectra®-kit (Group I) to those manually restrained (Group II). The mean±SE % feeding success was 75.0±8.2% and 82.1±8.2% for tsetse flies in Groups I and II respectively. Statistical analysis using two sample t-test showed no significant difference between the two groups at p≤0.05, indicating that Infectra®-kit as a restraining device was as good as the conventional manual restraint method. The main benefits of using Infectra®-kit for transmission studies therefore include reduction of man-hours and animal restraining-related discomfort. In addition, the risk of accidental injury to laboratory personnel by either mice or tsetse flies is minimized, which is an important consideration when working with zoonotic parasites.

Individual growth history of larval Atlantic mackerel is reflected in daily condition indices

Abstract We tested the hypothesis that faster-growing Atlantic mackerel (Scomber scombrus) larvae generally achieve better feeding success than their slower-growing counterparts. Feeding success and growth were derived from the analysis of gut content and otolith microstructure of larvae from four cohorts (1997–2000) from the southern Gulf of St Lawrence. We observed a high degree of serial correlation in otolith growth (OG) from hatching, suggesting that events occurring early in life have long-standing effects on future growth potential. The diet of fast-growing individuals was dominated by large prey, such as cladocerans and fish larvae (including conspecifics), while slow-growing larvae foraged primarily on smaller copepod naupliar stages. Both feeding success (stomach content) and an index of condition (body depth) were positively correlated with OG, and these relationships explained approximately three times more variance in mackerel than in larval radiated shanny (Ulvaria subbifurcata) of similar size. Relationships linking age-dependent scores of body depth to feeding success and growth were ∼3.5–4 times stronger than those based on length-dependent indices, suggesting that differences in energy allocation during early ontogeny may play a significant role in determining an individual's capacity to cope with variations in feeding conditions.

Value of nasojejunal nutrition in the treatment of children with acute pancreatitis

To evaluate the feasibility and effectiveness of placement of nasojejunal feeding tube and nasojejunal nutrition feeding in children with acute pancreatitis. Twenty-two patients (of whom 13 had severe acute pancreatitis and 9 acute mild pancreatitis) who needed nutritional intervention were selected. They were from Department of Gastroenterology and Surgery during the years 2009 - 2012, and they were at high nutritional risk after STONGkid nutrition risk screening. The average age of them was 5 - 15 years (9.1 years ± 2.8 years). Assisted by endoscopy, the nasojejunal feeding tube was placed in 22 of 24 patients (in 2 cases of recurrent pancreatitis the tubes were placed again after extubation). Besides the use of regular fasting, antacids, inhibitors of trypsin secretion, and anti-infective treatment, 23 cases of all children got nasojejunal nutrition treatment as well. The outcome measures included the success rate, complications of endoscope-assisted nasojejunal tube placement. The children's tolerance and nutrition indicators (weight, blood lymphocytes count, erythrocytes count, serum albumin, serum creatinine, blood urea nitrogen) were observed before and after enteral nutrition therapy. Malnutrition evaluation was done 24 times before treatment among 22 patients, incidence of malnutrition was 33% in 22 cases. Placement of nasojejunal tube placement was attempted for a total of 24 times and was successful on first placement in 22 cases, in two cases the placement was successful on the second placement, so the success rate of the first attempt for placement was 92%. No significant complications were observed in any of the cases. Twenty-three of 24 cases were given standardized enteral nutrition (one case was not given enteral nutrition therapy but underwent ERCP due to obstructive jaundice). Twenty-two of 23 cases could tolerate enteral nutrition well, only 1 case was unable to tolerate enteral nutrition due to the pancreas schizophrenia, paralytic ileus. The treatment of jejunal feeding success rate was 96%. The feeding duration was 2 - 74 d (27.0 d ± 18.3 d). The adverse reactions include plugging of the tube in two cases, constipation in two cases, five cases had abdominal pain, diarrhea in 2 cases, vomiting in 2 cases and 1 case of jejunum retention. No case had nasopharynx ulcers, gastrointestinal perforation, gastrointestinal bleeding, re-feeding syndrome and infection etc. Blood erythrocytes count, serum creatinine, blood urea nitrogen were not significantly changed. Twenty of 23 cases were cured, 2 cases were improved and 1 case was unchanged. Endoscope-assisted nasojejunal tube placement for children with acute pancreatitis is safe and feasible. Nasojejunal nutrition therapy is effective for acute pancreatitis patients who are at severe nutritional risk, especially for the improvement of the nutritional status of children.