Increased Feeding Activity Research Articles

First instar and adult male bed bugs, Cimex lectularius (Hemiptera: Cimicidae), increase feeding activity in the presence of adult females

BackgroundBed bugs, Cimex lectularius, form day-time aggregations from which they depart at night to feed on human blood. Obtaining an initial blood meal is a critical step in the development of first instars. Previous research had shown that first instars had greater success in obtaining this essential meal when in the presence of adults than when they were alone.MethodsFeeding by bed bugs was tested in upright vertical cylindrical chambers fitted with a paper ramp to aid in climbing toward a blood feeder suspended across the upper end of the cylinder. Feeding success by the first instars was tested when they were alone in the chamber or when they were in the presence of adult females, males, or both together. ResultsThe mean proportions of the first instars that fed were significantly higher when they were confined with adults of both sexes or adult females than when they were confined alone or with males. Feeding by adult males was also enhanced by confinement with females. When first instars and adult females were confined together, the mean duration before first instars began feeding was longer than for females. There was no difference in feeding success by first instars confined with their mothers or nonmothers.ConclusionsElevated feeding by first instars and adult males in the presence of females may be adaptive traits that enhance fitness. First instars must feed to avoid dehydration and starvation and to obtain resources needed for development. Adult males would benefit not only by increased feeding success but also by greater likelihood of finding a recently engorged female with which to mate. The lack of any difference in feeding success of first instars in the presence of their mothers or nonmothers argues against parental care in this species.Graphical

Daily patterns in parasite processes: diel variation in fish louse transcriptomes

Parasites, similar to all other organisms, time themselves to environmental cues using a molecular clock to generate and maintain rhythms. Chronotherapeutic (timed treatment) techniques based on such rhythms offer great potential for improving control of chronic, problematic parasites. Fish lice are a key disease threat in aquaculture, with current control insufficient. Assessing the rhythmicity of fish lice transcriptomes offers not only insight into the viability of chronotherapy, but the opportunity to identify new drug targets. Here, for the first known time in any crustacean parasite, diel changes in gene transcription are examined, revealing that approximately half of the Argulus foliaceus annotated transcriptome displays significant daily rhythmicity. We identified rhythmically transcribed putative clock genes including core clock/cycle and period/timeless pairs, alongside rhythms in feeding-associated genes and processes involving immune response, as well as fish louse drug targets. A substantial number of gene pathways showed peak transcription in hours immediately preceding onset of light, potentially in anticipation of peak host anti-parasite responses or in preparation for increased feeding activity. Genes related to immune haemocyte activity and chitin development were more highly transcribed 4 h post light onset, although inflammatory gene transcription was highest during dark periods. Our study provides an important resource for application of chronotherapy in fish lice; timed application could increase efficacy and/or reduce dose requirement, improving the current landscape of drug resistance and fish health while reducing the economic cost of infection.

A comparison of the retinal structure in the zebra-snout seahorse (Hippocampus barbouri Jordan & Richardson, 1908) between juveniles and adults in captivity

The activity of the sensory organ in the eye structure of the teleost fish is essential as it plays an important role in regulating fish-feeding behaviours. Unfortunately, the above information of zebra-snout seahorse Hippocampus barbouri, an aquaculture species in Thailand, has not been described. In this study, the eye structure, together with the retinal structure of juvenile [5th and 20th day after birth (DAB)] and adult (35th DAB), H. barbouri reared in captivity was investigated. All DABs were carried out and histologically observed. Light microscopic level explored the external-lateral surface of eye structure of H. barbouri, which consisted of the external, middle, and inner layers, as similarly reported in other teleost species. A well-differentiated retinal and photoreceptor cell layer were observed at 35th DAB compared to that at other DABs. This feature might be adequate to support the base of the increased feeding activity of adult seahorse in captivity for further research.

The Mediterranean mussel Mytilus galloprovincialis: responses to climate change scenarios as a function of the original habitat.

The impact of simulated seawater acidification and warming conditions on specimens of the mussel Mytilus galloprovincialis locally adapted to very distinct, widely separated sites in the Mediterranean Sea (Tunisia) and Atlantic Sea (Galicia, NW Spain) was evaluated in relation to key behavioural and eco-physiological parameters. Over the 2-month exposure to the experimental conditions, mussels were fed optimally to ensure that there are no synergistic interactions between climate change drivers and energetic status of the individuals. In general, regardless of origin (Atlantic or Mediterranean), the mussels were rather resilient to acidification for most of the parameters considered and they were able to grow in strongly acidified seawater through an increased feeding activity. However, shell strength decreased (40%) consistently in both mussel populations held in moderately and highly acidified seawater. The observed reduction in shell strength was not explained by slight alterations in organic matter, shell thickness or aragonite:calcite ratio. The combined effects of high acidification and warming on the key response of byssus strength caused a strong decline in mussel performance, although only in Galician mussels, in which the valve opening time decreased sharply as well as condition index (soft tissue state) and shell growth. By contrast, the observed negative effect of highly acidified scenario on the strength of Tunisian mussel shells was (partly but not totally) counterbalanced by the higher seawater temperature. Eco-physiological and behavioural interactions in mussels in relation to climate change are complex, and future scenarios for the ecology of the species and also the feasibility of cultivating them in Atlantic and Mediterranean zones are discussed.

Effects of non-native tree plantations on soil microarthropods and their feeding activity on the Chinese Loess Plateau

Afforestation with non-native tree species is regarded as a rapid management strategy to rehabilitate degraded ecosystems. Despite the well-documented effects of non-native forest plantations (NNFPs) on plant diversity, relatively few studies have explored the effects of NNFPs on soil fauna and ecosystem processes mediated by them. Soil microarthropods are key contributors to decomposition and soil biogeochemical cycling processes, and their feeding activity has been recognized as an important functional indicator in soil. Here, we investigated the soil microarthropod diversity (mites and springtails) and their feeding activity in non-native Robinia pseudoacacia (RP), Populus × canadensis (PC) and native Armeniaca sibirica (AS) forests on the Chinese Loess Plateau. We also investigated the soil properties and understory plant diversity to explore the potential links among these variables and feeding activity by using structural equation modeling (SEM). The abundance of soil microarthropods was significantly greater in the non-native RP and PC plantations than in the native AS plantations. The feeding activity in the RP and AS plantations was at a similar level to each other and was significantly lower than that in the PC plantations. Results from SEM showed that non-native PC rather than RP plantations significantly increased feeding activity by raising the abundance of mites and/or springtails. The results demonstrate that the effects of NNFPs on feeding activity depend on tree identity, and suggest that non-native PC rather than RP plantations contribute to enhancing soil ecosystem functioning, which provide guidance for non-native tree selection on the Loess Plateau.

The effect of short-term feed-deprivation and moult status on feeding behaviour of the Pacific white shrimp (Litopenaeus vannamei)

There is increasing recognition of the need to understand behaviours of species important in aquaculture to facilitate their production, however to date there has been limited focus in this area. The Pacific white shrimp (Litopenaeus vannamei), for example, is the most cultivated species in crustacean aquaculture globally, yet there are few studies that have addressed its feeding behaviour in detail. The objective of the present study was to evaluate the feeding behaviour of L. vannamei in response to feed-deprivation and moult status. Twenty-four juvenile shrimp (10.51 ± 2.17 g) were divided across three different feed-deprivation conditions (+0 h (control), +24 h or +48 h; n = 8 per treatment). Shrimp in all treatment groups were provided with their last food intake at 19.00 and subsequently experienced 14 h feed-deprivation. Those in the control group were recorded for behaviour at 09.00 the following day and were not feed-deprived for any additional time (+0 h), whereas the other treatments were feed-deprived by one (+24 h treatment) or two (+48 h treatment) extra days. Moult status was constantly monitored as it changed in all shrimp throughout the course of the experiment. Shrimp, provided with food, were observed individually via video in test arenas for 20 min where behaviours (e.g. inactivity, detection, feeding, attraction-to-feed) were recorded. Each shrimp was observed five times across different days with three days between recordings to obtain information on within-individual in addition to between-individual variation. Shrimp feed-deprived for +24 h and +48 h showed significantly increased feeding activity compared to the control group, which spent more time inactive and performing detection behaviours. Shrimp deprived of food for +48 h also had higher attraction-to-feed score, which were positively correlated with feeding activity. Shrimp in the inter-moult stage displayed increased feeding activity and a higher attraction-to-feed score. Longer periods of feed-deprivation reduced within- and between-individual variation across the majority of the behaviours measured. The results of this study highlight the relevance of feed-deprivation and moult status in nutritional trials and provide important baseline information for developing the use of behaviour to improve L. vannamei production.

The impact of dark exposure on broiler feeding behavior and weight of gastrointestinal tract segments and contents

Ross 308 broilers were observed at 2 ages to quantify how duration of darkness affects behavior and alters the gastrointestinal tract (GIT, segment and content weights) over 24h. Four treatments provided 1 (1D), 4 (4D), 7 (7D), or 10 (10D) h of darkness. Birds (n = 4000) were housed in 8 rooms with 8 pens per room (2 replications per treatment and 4 replications per gender per room). The GIT data were collected on day 27 to 28 (6 males per treatment, euthanized at 2h intervals for 24h) and expressed as a percentage of body weight. Data were analyzed as a completely randomized design, with treatment nested within room. Production data were analyzed as a 4 (dark) x 2 (gender) factorial arrangement and GIT data as a 4 (dark) x 12 (time) factorial arrangement. Regression analyses established relationships between darkness and dependent variables. At 31 d, regression analyses showed no effect on body weight. The highest feed consumption was observed under 4D. Mortality was lowest under 10D. Birds on 10D were the most feed efficient and had the heaviest crops. Crop content interacted with time of day, with peaks prior to dark under 4D, 7D, and 10D. Empty gizzard weight increased linearly as dark increased (P < .01). Behavior was examined as a 4 (dark) x 2 (age) x 2 (gender) factorial arrangement of treatments. Five birds per gender per room were focally observed for 24h. Dark data were examined using regression analyses and an analysis of variance assessed age and gender data. As dark increased, feeding bout frequency increased and total time spent at the feeder decreased linearly (P = 0.01 and P < .01, respectively). As birds aged, feeding frequency decreased and feed bout length increased. Males visited the feeder more frequently. Birds anticipated dark periods >4h and increased feeding activity prior to dark. Broilers adapt their feeding behavior in response to dark exposure, which alters GIT segment and content weight and likely feed passage rate.

Relationship between metabolic status and behavior in dairy cows in week 4 of lactation

Blood metabolite and hormone concentrations are indicative of metabolic status, but blood sampling and analysis is invasive and time-consuming. Monitoring behavior can be done automatically, and behaviors may also be used as indicators of metabolic status. The aim of this study was to analyze the relationships between metabolic status and feeding behavior, lying behavior, motion index and steps of dairy cows in week 4 postpartum. Behavioral data from 81 Holstein-Friesian cows were collected using computerized feeders and accelerometers, and blood samples were collected for analysis of free-fatty acid (FFA), β-hydroxybutyrate (BHB), glucose, insulin, IGF-1 and growth hormone (GH) concentrations. First, cluster analysis was performed to categorize cows as having poor, average, good or very good metabolic status based on their plasma FFA, BHB, glucose, insulin, IGF-1 and GH concentration. Subsequently, the performance and behavior of cows in clusters with poor, average and good metabolic status were compared using GLM. Cows with a poor or average metabolic status tended to have greater fat-and-protein-corrected milk yield than cows with good metabolic status. Furthermore, cows with a poor metabolic status had a lower energy balance and dry matter intake (DMI) than cows with an average or good metabolic status and had a lower number of meals than cows with good metabolic status. Daily number of visits to the feeder and lying time tended to be positively related with metabolic status. Feeding rate (kg/min), daily meal time (min/day), number of lying bouts per day, steps and motion index were not related with metabolic status. In conclusion, better metabolic status in dairy cows in early lactation was associated with a greater DMI, increased feeding activity and a tendency to more time spent lying, compared with poor metabolic status. These results suggest that compromised metabolic status is reflected in altered cow’s behavior in week 4 of lactation.

Effects of the herbicide Roundup® on the metabolic activity of Gammarus fossarum Koch, 1836 (Crustacea; Amphipoda).

Pesticides can easily reach surface waters via runoff and their potential to have detrimental impacts on freshwater organisms is high. Not much is known about how macroinvertebrates react to glyphosate contamination. In this study we investigated lethal and sublethal effects of the exposure of Gammarus fossarum to Roundup®, a glyphosate-based herbicide. The LC10 and LC50 values after 96 h were determined to be 0.65 ml/L Roundup® (230 mg/L glyphosate) and 0.96 ml/L Roundup® (340 mg/L glyphosate), respectively. As a sublethal measure of toxicity we conducted eight experiments with the feeding activity and the respiratory electron transport system (ETS) activity as endpoints. All experiments lasted seven days. Although the LC10 concentration of Roundup® was used for the feeding activity tests, 49% of the gammarids died before the end of the experiments, which is inconsistent with the calculated LC10-values. The feeding activity was significantly higher in Roundup®-enriched water (mean = 0.18 mg/mg x d) in comparison to pure spring water (mean = 0.079 mg/mg x d). No significant difference was observed between the ETS activity, which was determined after 24, 48 or 96 h after the start of the experiment, of the gammarids in Roundup® solution and in the control. The LC-values determined here are rather high, and exceed background glyphosate concentrations in most anthropogenically influenced surface waters. The increased feeding activity when exposed to Roundup® in combination with an unchanged ETS activity suggests effects on the metabolic efficiency of G. fossarum. We argue that Roundup® enhances the anabolic activity (feeding activity) in order to maintain the catabolic activity (ETS activity).

Daphnia magna increase feeding activity in the presence of four amino acids

Daphnia magna increase feeding activity in the presence of four amino acids

Biological control agent selection under environmental change using functional responses, abundances and fecundities; the Relative Control Potential (RCP) metric

We currently lack the capacity to rapidly and reliably predict the efficacy of biological control agents due to inadequate consistency in derivations of functional and numerical responses and potential effects of context-dependencies. Here, we propose and apply a novel metric, Relative Control Potential (RCP), which combines the functional response (FR, per capita effect) with proxies for the numerical response (NR, agent population response) to compare agent efficacies, where RCP = FR × abundance (or other proxies e.g. fecundity). The RCP metric is a comparative ratio between potential biocontrol agents, where values > 1 indicate higher relative control efficacy. Further, RCP can compare the efficacy of agents under environmental contexts, such as temperature change. We thus derived the RCP for two predatory cyclopoid copepods, Macrocyclops albidus (Cyclopoida: Cyclopidae) and Megacyclops viridis (Cyclopoida: Cyclopidae), towards larvae of the mosquito Culex pipiens (Diptera: Culicidae) under temperatures representative of current and future climate. Both copepods exhibited potentially population destabilising Type II FRs, with increasing temperatures inducing greater magnitude FRs through increased attack rates and decreased handling times. Attack rates by M. albidus were higher than M. viridis, yet handling times and maximum feeding rates were similar between the species across all temperatures. The inclusion of abundance data drives an elevated RCP of M. albidus and the integration of fecundity drives greater RCP of M. albidus at peak temperatures. Q10 values are indicative of increased feeding activity by both copepods with temperature increases, however relative feeding level increases of M. viridis slowed towards the peak temperature. We present RCP calculations and biplots that represent the comparative efficacies of the two biological control agents across temperatures. The Relative Control Potential (RCP) metric thus provides a new tool for practitioners to better assess the potential efficacy of biocontrol agents before their integration into management approaches for pests, vectors and invasive species.

In shallow water ecosytems the abiotic environment is more important than prey abundance for foraging terns

Shallow freshwater aquatic ecosystems are discrete feeding patches for fish eating birds. A unique feature of these ecosystems is that their physical conditions can change dramatically in a short period of time, particularly temperature, turbidity, and dissolved oxygen. Based on previous research we predicted that increasing turbidity will reduce the availability of fish to birds due to reduced visibility, while increasing temperature and decreasing dissolved oxygen will increase their availability through increases in activity and movement towards the more oxygenated surface areas, respectively. We also predicted that overall abundance of fish should increase feeding activity by terns. We measured these environmental variables, bird activity, and fish abundance from May to August from 2006 to 2008 in a marsh in southern Manitoba, Canada. Our results showed that only variation in dissolved oxygen levels affected feeding activity by terns. Since there was no relationship between bird and fish abundance either within or among years, these results suggest that it is the availability of prey (i.e. the upward movement of fish into the water column) and not their abundance per se that influences the number of avian predators present and hence the risk of predation to fish. These data demonstrate how the physical environment of aquatic ecosystems can impact terrestrial avian predators, and the link that exists between the physical environment and predator-prey interactions.

A gene-driven recovery mechanism: Drosophila larvae increase feeding activity for post-stress weight recovery.

Recovery from weight loss after stress is important for all organisms, although the recovery mechanisms are not fully understood. We are working to clarify these mechanisms. Here, we recorded enhanced feeding activity of Drosophila melanogaster larvae from 2 to 4h after heat stress at 35°C for 1h. During the post-stress period, expression levels of sweet taste gustatory receptor genes (Grs), Gr5a, Gr43a, Gr64a, and Gr64f, were elevated, whereas bitter taste Grs, Gr66a, and Gr33a, were decreased in expression and expression of a non-typical taste receptor Gr, Gr68a, was unchanged. Similar upregulation of Gr5a and downregulation of Gr66a was recorded after cold stress at 4°C. Expression levels of tropomyosin and ATP synthase ß subunit were significantly increased in larval mouth parts around 3 to 5h after the heat stress. We infer that up-regulation of post-stress larval feeding activity, and weight recovery, is mediated by increasing capacity for mouth part muscular movements and changes in taste sensing physiology. We propose that Drosophila larvae, and likely insects generally, express an efficient mechanism to recover from weight loss during post-stress periods.

Feeding and social activity of insectivorous bats in a complex landscape: The importance of gallery forests and karst areas

Worldwide, increasing human activity, such as agriculture and mining, and decreased landscape complexity, are negatively affecting numerous mammal species. For example, bat communities are becoming threatened in many locations mostly due to the loss of their preferred roosting and foraging habitats. Brazilian landscapes and their associated bat communities are no exception, with the situation being further exacerbated by recently adopted permissive environmental laws that have resulted in reduced biodiversity protection and conservation. Therefore, there is an urgent need to understand how landscape and environmental variables relate to bat activities in Brazil in order to support efforts for their conservation. We used acoustic monitoring data to investigate differences in foraging and social activity of insectivorous bats among four habitat types in a heterogeneous landscape in the Cerrado-Atlantic forest ecotone in southeastern Brazil. We also sampled insect availability and measured temperature at the same sites. Our results showed increased social activity and a greater number of species emitting social calls in karst, and increased feeding activity with a greater number of species emitting feeding buzzes in gallery forest. We also found a positive influence of both temperature and insect abundance on foraging and social activity. Our study provides new insights regarding habitat use by bats in a heterogeneous landscape, and demonstrates the importance of preserving different habitats in heterogeneous landscapes for the conservation of bat species and the ecological functions they perform.

Short communication: The diurnal intake and behavior of dairy cows when access to a feed of consistent nutritive value is restricted

The diurnal variation in pasture nutritive value adds a confounding factor to studies elucidating the effect of time of day on behavior. Our work separates the effect of time of day on both feeding and lying patterns for cows outdoors to enable the alignment of feeding behavior with feed management. We determined the diurnal intake patterns and behavior of dairy cows when the nutritive value of feed remained constant throughout 24 h in an outdoor environment, and when feed access was restricted. Nine nonlactating Holstein-Friesian cows (live weight 626 ± 53 kg, age 96 ± 33 mo; mean ± SD) were split into 3 groups of 3 and offered lucerne hay cubes (cube volume 32 mm3) ad libitum according to 3 treatments: full access (FA, feed access 24 h), day access (DA, feed access between 0600 and 1800 h), and night access (NA, feed access between 1800 and 0600 h). Treatments were applied to individual cows in a crossover design with 7-d periods. During the last 4 d of each period, data were collected on feed intake, as well as feeding and lying behaviors. Total daily intake was greater for cows on the FA treatment (3.5% of BW) compared with the DA and NA treatments at 3.1 and 2.9% of BW, respectively. The cows with FA consumed 69% of their total intake during the day (0600-1800 h), with the greatest intake (39%) occurring during 1200 to 1800 h and only 12% of intake occurring during 2400 to 0600 h. Cows with DA consumed 56% of feed during 0600 to 1200 h and 44% during 1200 to 1800 h. In contrast, NA cows consumed more feed (74%) during the first 6 h period (1800-2400 h), thus maximizing lying time between 2400 and 0600 h. The time spent lying throughout daylight periods varied between treatments; however, total daily lying time was similar across the 3 treatments. This experiment shows the feeding and lying behaviors of cows when feed quality remains constant throughout 24 h, which will assist the formulation of variable feed allocation strategies for future testing in both robotic and conventional milking systems. Varying the quantity of feed offered throughout 24 h may benefit robot utilization at night in automatic milking systems through increased feeding activity, and as we observed, is likely to have little effect on lying time or DMI, with cows readily adapting to changes in feed management. Conversely, aligning feed on offer with preferred feeding time in conventional milking systems may increase the intake of high quality pasture.

A Plant Bacterial Pathogen Manipulates Its Insect Vector's Energy Metabolism.

Insect-transmitted plant-pathogenic bacteria may alter their vectors' fitness, survival, behavior, and metabolism. Because these pathogens interact with their vectors on the cellular and organismal levels, potential changes at the biochemical level might occur. "Candidatus Liberibacter asiaticus" (CLas) is transmitted in a persistent, circulative, and propagative manner. The genome of CLas revealed the presence of an ATP translocase that mediates the uptake of ATP and other nucleotides from medium to achieve its biological processes, such as growth and multiplication. Here, we showed that the levels of ATP and many other nucleotides were significantly higher in CLas-infected than healthy psyllids. Gene expression analysis showed upregulation for ATP synthase subunits, while ATPase enzyme activity showed a decrease in ATPase activity. These results indicated that CLas stimulated Diaphorina citri to produce more ATP and many other energetic nucleotides, while it may inhibit their consumption by the insect. As a result of ATP accumulation, the adenylated energy charge (AEC) increased and the AMP/ATP and ADP/ATP ratios decreased in CLas-infected D. citri psyllids. Survival analysis confirmed a shorter life span for CLas-infected D. citri psyllids. In addition, electropenetrography showed a significant reduction in total nonprobing time, salivation time, and time from the last E2 (phloem ingestion) to the end of recording, indicating that CLas-infected psyllids were at a higher hunger level and they tended to forage more often. This increased feeding activity reflects the CLas-induced energetic stress. In conclusion, CLas alters the energy metabolism of its psyllid vector, D. citri, in order to secure its need for energetic nucleotides.IMPORTANCE Insect transmission of plant-pathogenic bacteria involves propagation and circulation of the bacteria within their vectors. The transmission process is complex and requires specific interactions at the molecular and biochemical levels. The growth of the plant-pathogenic bacteria in the hemolymph of their vectors indicated that the hemolymph contains all the necessary nutrients for their growth. In addition to nutrients, "Candidatus Liberibacter asiaticus" (CLas) can take up energetic nucleotides, such as ATP, from its vector, Diaphorina citri, using ATP translocase. In this study, we found that the CLas pathogen manipulates the energy metabolism of its insect vector. The accumulation of ATP in CLas-infected D. citri psyllids indicated that CLas induces ATP production to fulfill its need for this energetic compound. As a result of ATP accumulation, a shorter life span and altered feeding behavior were observed. These findings increase our knowledge of insect transmission of the persistent-circulative-propagative type of plant pathogens vectored by insects.

Relations between bacterioplankton, heterotrophic nanoflagellates, and virioplankton in the littoral zone of a large plain reservoir: Impact of bird colonies

Interactions of the main components of microbial planktonic food web (bacteria, heterotrophic nanoflagellates, and viruses) were studied in a protected overgrown littoral zone of the Rybinsk Reservoir (Upper Volga).. The effect of bird colonial, settlements (the Laridae family) on these processes was deter- mined. The following systems exhibited significant negative correlations: "heterotrophic nanoflagellates- large rod-shaped bacteria" ("predator-prey"), "viruses-bacteriophages-bacterial products" ("parasite-. host") and "heterotrophic nanoflagellates-viruses-bacteriophages." Relations between biotic factors con- trolling bacterial development were more pronounced outside the zone affected by colonial bird settlements. Near the bird colony the role of viruses in mortality of planktonic bacteria increased. Reproduction of bacte- rial cells accelerated in response to the increase in feeding activity of heterotrophic nanoflagellates. Viruses- bacteriophages and heterotrophic nanoflagellates probably eliminate different targets until medium-sized cells become predominant in the bacterial community. Then heterotrophic nanoflagellates consume bacterial cells infected with viruses.

Metamorphosis and definitive organogenesis in the holothurian Apostichopus japonicus

The structure of the late doliolaria, pentactula and 1-month-old juvenile of the holothurian Apostichopus japonicus was studied using light microscopy and 3D reconstruction methods. It was shown that metamorphosis in this species consists in the reorganization of the shape of the body and the destruction of provisional organs. The late doliolaria has a spindle-like form, ciliary rings and hyaline spheres shifted relative to the anterior-posterior axis of the body. Some provisional organs (ciliary rings, hyaline spheres) are destroyed during settlement, and others (hydropore and hydroporic canal) remain after metamorphosis. Definitive organogenesis in A. japonicus begins long before metamorphosis. The late doliolaria already has well-developed water-vascular and digestive systems, and the ectoneural part of the nervous system. Muscle and hemal systems begin to form in the pentactula. Moreover, the calcareous ring and connective tissue part of the body wall develop at this stage. The pentactula has anlages of the hyponeural part of the nervous system, which form in the mid-ventral and dorsal nerve cords. The hemal ring of the pentactula is located on the inner wall of the water-vascular ring. It remains unclosed in the left ventral radius. One-month-old juveniles have all the major organ systems except respiratory and reproductive systems. The hemal vessels of the intestine are well developed and begin to form the rete mirabile. Differentiation of the intestine into regions due to differential specialization of the enterocytes begins in 1-month-old juveniles. Obviously, emergence of new types of enterocytes enables the animal to consume a wider range of food items and indicates its increased feeding activity.

Mechanisms linking fungal conditioning of leaf litter to detritivore feeding activity

Saprotrophic fungi are one of the primary groups of organisms responsible for decomposition and nutrient cycling processes. Aside from their direct effects on litter decomposition, these organisms may indirectly affect litter invertebrate activity via fungal-mediated conditioning (i.e. ‘priming’) of litter substrates. While this priming effect is generally assumed to take place, this assumption is based on correlative observations and feeding preference trials rather than experimental discrimination of the mechanisms driving the process. We used a microcosm experiment of brown-rot (Fistulina hepatica, Fomitopsis lilacinogilva) and white-rot (Pycnoporus coccineus) fungi on two sclerophyllous leaf litters (Eucalyptus loxophleba and Acacia acuminata) to test if a fungal-mediated change in plant litter increased the nutritive value of the food source, and if a change in cell-wall (structural) compounds reduced the toughness of leaves, resulting in increased feeding activity by invertebrates. Brown- and white-rot fungal colonization had significant and diverse effects on the total nutrient concentrations and proportions of cellulose, lignin and hemicellulose of the leaf litter–fungi complex. However, significant decreases in leaf toughness and increases in mass loss and leaf fragmentation associated with detritivorous millipede (Ommatoiulus moreletii) activity only occurred in white-rot primed microcosms relative to the control. The mechanisms by which the white-rot fungus affected both leaf toughness and millipede feeding activity differed between leaf litters. In E. loxophleba microcosms, reduced leaf toughness and increased millipede grazing were mediated by relative changes in litter inorganic chemistry, rather than structural compounds, whereas in A. acuminata microcosms the effects of fungal priming were not mediated by either. These results suggest that, in the early stages of decomposition, fungal priming effects on leaf litter nutrients are a more important determinant of litter–invertebrate interactions than changes to litter structural compounds. Furthermore, different species of fungi interact with different litter types and invertebrates in functionally different ways.

Seasonal fluctuations in occurrence of inshore Bryde's whales in Plettenberg Bay, South Africa, with notes on feeding and multispecies associations

Seasonal fluctuations in the occurrence of inshore South African Bryde's whales Balaenoptera edeni were investigated between November 2005 and June 2008. Sighting data were collected in Plettenberg Bay on the south-east coast of South Africa. Bryde's whale occurrence was modelled in relation to the following environmental covariates: sea surface temperature, chlorophyll a concentrations and wind speed. Seasonal increases in encounter rates (sightings per day) were observed during summer and autumn, with a peak in April that corresponded to increased feeding activity and above average aggregation sizes. All three environmental covariates were significant factors in terms of explaining variability in the occurrence of whales. Multispecies associations with common dolphins Delphinus capensis and Cape gannets Morus capensis were most common in summer and autumn, when feeding activity was highest.