Influence of host plants on feeding, growth and reproduction of Papilio polytes (The common mormon)

We studied the feeding, growth and reproductive behaviour of Papilio polytes (common mormon butterfly) on five different host plants, Murraya koenigii, Toddalia asiatica, Glycosmis pentaphylla, Aegle marmelos and Citrus medica. The growth rate of P. polytes was fastest on M. koenigii followed by T. asiatica, C. medica, G. pentaphylla and A. marmelos. We related this to the nutrient contexts of the five plants. The plants T. asiatica and C. medica had higher water contents, which influenced the growth rate of the insect. M. koenigii was found to contain rich quantities of carbohydrate. M. koenigii, T. asiatica and C. medica were also rich in protein when compared to A. marmelos and G. pentaphylla. Total amino acid levels were comparatively higher in M. koenigii, T. asiatica, C. medica rather than A. marmelos and G. pentaphylla.     

Effect of intestinal erythrocyte agglutination on the feeding performance of Triatoma brasiliensis (Hemiptera: Reduviidae)

Triatoma brasiliensis is an important vector of Trypanosoma cruzi in Brazil. The feeding efficiency on its hosts depends on several parameters including the maintenance of the ingested blood at low viscosity, which could be modulated by the anterior midgut (crop) anticoagulant and haemagglutinant activities. In the present study, we characterized T. brasiliensis crop haemagglutination activity and evaluated its importance in the feeding process. Soluble crop contents (SCC) of T. brasiliensis were able to agglutinate rat, mouse and rabbit eryhtrocytes, but had no activity on cattle and Thrichomys apereoides, a rodent species commonly associated with T. brasiliensis in the wild. The haemagglutination was characterized by the immediate formation of several clusters of erythrocytes connected by flexible elastic-like fibers. The feeding efficiency of T. brasiliensis on rat (agglutinated by SCC) was almost double that from T. apereoides (not agglutinated by SCC). The influence of haemagglutination on feeding was confirmed by artificially feeding bugs on a diet composed of cattle or rat erythrocytes. The bugs fed on cattle erythrocytes had lower ingestion rates in comparison to those fed on rats. The results indicate that, in addition to other parameters, haemagglutination brought about by SCC has an important role in the feeding efficiency of T. brasiliensis.     

Variability in response of four populations of Amblyseius largoensis (Acari: Phytoseiidae) to Raoiella indica (Acari: Tenuipalpidae) and Tetranychus gloveri (Acari: Tetranychidae) eggs and larvae

Raoiella indica (Acari: Tenuipalpidae) is a phytophagous mite that recently invaded the Neotropical region. A predatory mite Amblyseius largoensis (Acari: Phytoseiidae) has been found associated with R. indica in Florida. This study evaluated A. largoensis by determining its likelihood of consuming eggs and larvae of R. indica and Tetranychus gloveri (Acari: Tetranychidae) under no-choice and choice conditions. To detect variations in the response of A. largoensis to R. indica, four populations of predators were examined: (1) predators reared exclusively on R. indica in the laboratory for 2 years, (2) predators reared on T. gloveri in the laboratory for 2 months but reared on R. indica for 2 years previously, (3) predators collected from a field infested with R. indica, and (4) predators collected from a field that had never been infested with R. indica. Results of this study suggest that A. largoensis is likely to accept and consume high numbers of R. indica eggs regardless of their previous feeding experience. In contrast, all populations consumed relatively fewer R. indica larvae than the other prey tested. Predators previously exposed to R. indica were more likely to consume R. indica larvae. By contrast, predators not previously exposed to R. indica showed the lowest likelihood of choosing to feed on this prey item. Plasticity in the response of A. largoensis to R. indica larvae could be associated to selection, learning, or a combination of both. The possible implications of the observed differences in terms of biological control of R. indica are discussed.     

Effect of dietary history and algal traits on feeding rate and food preference in the green sea urchin Strongylocentrotus droebachiensis

Feeding behaviour is influenced by a variety of factors, including nutritional requirements, the quality of available foods, and environmental conditions. We examined the effect of two factors, food morphology and dietary history, on the feeding rate and preference of the sea urchin Strongylocentrotus droebachiensis. Standardizing food shape and structure did not alter urchins' expected preference for the native kelp Laminaria longicruris over the invasive alga Codium fragile ssp. tomentosoides. However, when foods containing L. longicuris were shaped to mimic the algae, the C. fragile mimic was consumed more rapidly than the kelp mimic. Dietary history had no effect on single diet feeding rate. Urchins feeding on C. fragile consistently consumed twice as much (by mass) as those fed kelp, regardless of their previous diet. Despite higher feeding rates on C. fragile, urchins feeding on this alga were unable to compensate for its low energetic content and ingested less energy. Dietary history had a short-term effect on food preference, with urchins tending to prefer less familiar foods. Our findings suggest that urchins feed on C. fragile at a high rate, due to ease of handling and/or compensatory feeding, and that they do not a have strict preference hierarchy. Rather, food choice appears to reflect active maintenance of a mixed diet.     

Use of spent mushroom substrates from Agaricus subrufescens (syn. A. blazei, A. brasiliensis) and Lentinula edodes productions in the enrichment of a soil-based potting media for lettuce (Lactuca sativa) cultivation: Growth promotion and soil bioremediation

This study aimed to assess physicochemical and microbiological properties of fresh spent mushroom substrates (SMSs) – without post-crop heat treatment – from Agaricus subrufescens and Lentinula edodes production to optimize the use of these residues in the soil enrichment for lettuce growth promotion and soil remediation. Organic matter and C content of both SMSs were high. Fresh A. subrufescens SMS was a good source of N, P and K. On the other hand, L. edodes SMS presented a lower concentration of these nutrients and a high level of immaturity. Both SMSs presented high electric conductivity values (2.5–3.4 mS/cm). Microbiological analysis, based upon enumeration of culturable bacteria (thermophilic and mesophilic) and fungi, and also evolution of CO₂, showed that SMSs played higher microbial diversity than soil control. Laccase activity from A. subrufescens SMS tended to remain constant during a 2-month period, while L. edodes SMS presented low laccase activity throughout the same period. Agaricus subrufescens and L. edodes were able to grow on a PDA (Potato Dextrose Agar) media supplemented with different concentrations of atrazine (1–50 μg/ml), degraded the herbicide, attaining rates of 35% and 26%, respectively. On experiments of lettuce growth promotion using a soil-based potting media with different SMS rates, 5% and 10% (dw) rates of A. subrufescens SMS resulted in higher lettuce aerial dry weights than the rates of 25% and 40%, the chemical fertilization (NPK) and the control (soil). At 10% supplementation, lettuce aerial dry weight increased 2.2 and 1.3 times compared to the control and the NPK treatment, respectively. Protein content increased along with SMS rates. Fresh A. subrufescens SMS was an excellent supplement for lettuce growth promotion and showed potential for remediation of biocides possibly due to improved microbial diversity and enzymatic activity. Fresh L. edodes SMS was not a good fertilizer, at least under the conditions tested. However, microbiological analysis showed that promising results may be achieved when using fresh L. edodes SMS for soil remediation.     

Comparative studies on the allelopathic effects of two different strains of Ulva pertusa on Heterosigma akashiwo and Alexandrium tamarense

Allelopathic effects of fresh tissue and dry powder of a nonsexual and a sexual strain of the macroalga Ulva pertusa on the growth of the microalgae Heterosigma akashiwo and Alexandium tamarense were evaluated using long-term coexistence culture systems in which several concentrations of macroalga fresh tissue and dry powder were used. The effects of macroalga culture medium filtrate on the two HAB algae were also investigated. Moreover, isolation co-culture systems were built to confirm the existence of allelochemicals and preclude the growth inhibition by direct contact. Short-term algicidal effect assays of macroalgae on H. akashiwo were carried out to measure the rate of algal cell lysis. The results of the coexistence assays showed that the growth of H. akashiwo and A. tamarense was strongly inhibited by fresh tissue and by dry powder of both strains of U. pertusa. The allelochemicals were lethal to H. akashiwo at relatively higher concentrations. The macroalga culture medium filtrate exhibited no apparent growth inhibitory effect on the two HAB algae under initial or semicontinuous filtrate addition, which suggested that continuous release of small quantities of rapidly degradable allelochemicals from the fresh tissue of both strains of U. pertusa was essential to effectively inhibit the growth of H. akashiwo and A. tamarense.     

Experimental test of biodeposition and ammonium excretion from blue mussels (Mytilus edulis) on eelgrass (Zostera marina) performance

Blue mussels and eelgrass have been found to coexist in many locations. However, knowledge of the interactions between these species is limited. Two experiments were conducted in the laboratory, a “Deposit” and an “Epiphyte” experiment. The Deposit experiment examined possible effects of increasing load of blue mussel (Mytilus edulis) biodeposits on sediment biogeochemistry and eelgrass (Zostera marina) performance. Z. marina mesocosms received normal or high loads of mussel biodeposits (Normal and High), while no biodeposits were added to the Control. High dosage had overall negative effects on Z. marina, which was reflected as lower leaf numbers and biomass and accumulation of elemental sulphur in rhizomes. The sediment biogeochemical conditions were altered, as the mussel biodeposits enhanced sulphate reduction rates and increased sulphide concentrations in the porewater, which may result in sulphide invasion and reduced growth of Z. marina.In the Epiphyte experiment effects of mussel excretion, with particular emphasis on ammonium, on the growth of Z. marina and their epiphytes were examined. A thick cover of epiphytes developed on Z. marina growing together with M. edulis, and the relative growth rate was reduced with 20% compared to plants from control without mussels. Overall the experiments showed negative effects on Z. marina growing together with M. edulis, thereby supporting a preceding field study by Vinther et al. [Vinther, H.F., Laursen, J.S., Holmer, M. 2008. Negative effects of blue mussel (Mytilus edulis) presence in eelgrass (Zostera marina) beds in Flensborg fjord, Denmark. Est. Coast Shelf. Sci. 77, 91-103.].     

Effects of feeding regime on growth rate in the Mediterranean Sea anemone Actinia equina (Linnaeus)

Polyps of Actinia equina are the most common sea anemones in the rocky intertidal zone of the Mediterranean coast of Israel, where they occur in one of the southernmost populations of this species in the northern hemisphere. We examined effects of feeding rate on polyp growth at ambient sea temperature for this population. Under laboratory conditions, polyps were left unfed, or were fed with brine shrimp (Artemia) once every 2 weeks, once a week, or twice a week. Of the four experimental treatments, only feeding twice a week resulted in polyp growth; under all other regimes, the sea anemones lost body mass. We conclude that a high rate of feeding is required at sea temperatures in the eastern Mediterranean, where these sea anemones may have high metabolic rates relative to more northern populations.     

Seasonal variability in feeding behaviour, metabolic rates and carbon and nitrogen balances in the Sydney oyster, Saccostrea glomerata (Gould)

To establish if nutrients limit the growth of bivalves requires information not only on the quality of food available, but also the animals' feeding behaviour and endogenous metabolic demands. We hypothesized that growth of the Sydney rock oyster (Saccostrea glomerata) would vary in response to seasonal changes in food quality rather than quantity. We also predicted that the oysters would show feeding preferences for nitrogen over carbon, and this behaviour would result in carbon/nitrogen (C/N) ratios for ingested and absorbed matter that would be lower than the C/N of both the seston and the oysters' estimated metabolic maintenance requirements. The experiments were done in two phases under natural conditions. In phase 1, feeding behaviour was assessed on a single occasion and the results used to pose hypotheses for testing in phase 2, which included measurements made on three occasions encompassing autumn, winter and spring conditions. Growth rates varied with changes in ambient food quality and not with the concentration of total suspended matter. Feeding behaviour responded to food quality and, in most cases, resulted in nitrogen enrichment. For example, when nitrogen was potentially limiting to growth and/or maintenance, due to high food C/N (July) or high nitrogen demand (March), pre-ingestive selection ensured nitrogen enrichment of ingested matter and C/N ratios of ingested matter which were below the maintenance requirement. However, in November, when endogenous demands indicated an increased requirement for carbon, feeding behaviour resulted in carbon enrichment, an increase in carbon conversion efficiency, and ingested C/N ratios greater than the maintenance requirement. The results support the assertion of variable feeding physiology in oysters, responsive to both exogenous (seasonal differences in carbon and nitrogen availability) and endogenous (cycles of reproduction and growth) factors.     

O-Methylated mannogalactan from the microalga Coccomyxa mucigena, symbiotic partner of the lichenized fungus Peltigera aphthosa

A structural study of the carbohydrates from Coccomyxa mucigena, the symbiotic algal partner of the lichenized fungus Peltigera aphthosa, was carried out. It produced an O-methylated mannogalactan, with a (1 → 6)-linked β-galactopyranose main-chain partially substituted at O-3 by β-Galp, 3-OMe-α-Manp or α-Manp units. There were no similarities with polysaccharides previously found in the lichen thallus of P. aphthosa. Moreover, the influence of lichenization in polysaccharide production by symbiotic microalgae and the nature of the photobiont in carbohydrate production in lichen symbiosis are also discussed.     

The influence of bioturbation by the sandprawn Callianassa kraussi on feeding and survival of the bivalve Eumarcia paupercula and the gastropod Nassarius kraussianus

Field observations and experimental evidence have shown that bioturbation by the southern African sandprawn Callianassa kraussi may significantly influence the abundance and distribution of the filter-feeding bivalve Eumarcia paupercula and the grazing gastropod Nassarius kraussianus. It was hypothesized that (1) sediment reworking by C. kraussi negatively affects microalgal growth on the sediment surface, leading to a reduction in food intake by N. kraussianus, (2) sediment deposited by C. kraussi will also diminish the food uptake of E. paupercula by interfering with its filtration mechanism. To test these hypotheses, manipulative field and laboratory experiments were undertaken in which N. kraussianus and E. paupercula were added to treatments with and without C. kraussi, and their survival and gut chlorophyll-a content measured. The effects of C. kraussi on sediment erodability and on condition of E. paupercula (tissue mass/shell length) were determined in a second experiment. In the presence of C. kraussi, (1) microalgal consumption by both N. kraussianus and E. paupercula was halved; (2) condition and survival of E. paupercula were significantly reduced but survival of N. kraussianus was unaffected; and (3) sediment erodability was increased. A significant negative relationship was established between sediment erodability and condition of E. paupercula. Evidently C. kraussi exerts a strongly negative influence on the feeding of E. paupercula and N. kraussianus, and this may explain the scarcity of these organisms in areas containing high densities of C. kraussi.     

RPB2 sequences reveal a close phylogenetic relationship between tetraploid Hordelymus and diploid Hordeum species in Triticeae (Poaceae)

The origin of Hordelymus genome has been debated for years, and no consensus conclusion was reached. In this study, we sequenced and analyzed the RPB2 (RNA polymerase subunit II) gene from Hordelymus europaeus (L.) Harz, and its potential diploid ancestor species those were suggested in previous studies. The focus of this study was to examine the phylogenetic relationship of Hordelymus genomes with its potential donor Hordeum, Psathyrostachys, and Taeniatherum species. Two distinguishable copies of sequences were obtained from H. europaeus. The obvious difference between the two copies of sequences is a 24 bp indel (insertion/deletion). Phylogenetic analysis showed a strong affinity between Hordeum genome and Hordelymus with 85% bootstrap support. These results suggested that one genome in tetraploid H. europaeus closely related to the genome in Hordeum species. Another genome in H. europaeus is sister to the genomes in Triticeae species examined here, which corresponds well with the recently published EF-G data. No obvious relationship was found between Hordelymus and either Ta genome donor, Taeniatherum caput-medusae or Ns genome donor, Psathyrostachys juncea. Our data does not support the presence of Ta and Ns genome in H. europaeus, and further confirms that H. europaeus is allopolyploid.     

Dietary nitrogen availability in macroalgae enhances growth of the sea hare Aplysia californica (Opisthobranchia: Anaspidea)

Evidence suggests that marine herbivores select for prey items with elevated nitrogen content. We tested this hypothesis with experimental growth studies of the herbivorous gastropod Aplysia californica offered diets of the rhodophyte Gracilaria ferox with varying nitrogen content. A. californica had a sevenfold feeding preference by weight for G. ferox with higher tissue % N and % protein, and lower % C, % carbohydrate and carbon-to-nitrogen ratio (C/N) as compared to treatments with lower nitrogen and protein content. A. californica provided treatment diets of varying nitrogen availability (high, medium and low) also had significantly different growth rates within 30 days. The high N diet supported a two-fold higher growth rate than that of the medium N diet and four-fold higher than the low N treatment, with mean weights over the experiment reaching 20.4, 9.8, and 5.6 g, respectively. The evolutionary value of this dietary preference may facilitate faster growth to reproductive size, outgrowth of predators and sequestration of organic compounds from nitrogen-enriched macroalgae to deter predators. Despite recent attention, the importance of diet-derived compounds as anti-predatory chemical defenses in Aplysiids remains equivocal. Nitrogen-enriched macroalgal diets, however, may provide “primary metabolites” that serve as alternative defenses for Aplysiids.     

Core and symbiotic genes reveal nine Mesorhizobium genospecies and three symbiotic lineages among the rhizobia nodulating Cicer canariense in its natural habitat (La Palma,Canary Islands)

Cicer canariense is a threatened perennial wild chickpea endemic to the Canary Islands. In this study, rhizobia that nodulate this species in its natural habitats on La Palma (Canary Islands) were characterised. The genetic diversity and phylogeny were estimated by RAPD profiles, 16S-RFLP analysis and sequencing of the rrs, recA, glnII and nodC genes. 16S-RFLP grouped the isolates within the Mesorhizobium genus and distinguished nine different ribotypes. Four branches included minority ribotypes (3–5 isolates), whereas another five contained the predominant ribotypes that clustered with reference strains of M. tianshanense/M. gobiense/M. metallidurans, M. caraganae, M. opportunistum, M. ciceri and M. tamadayense. The sequences confirmed the RFLP groupings but resolved additional internal divergence within the M. caraganae group and outlined several potential novel species. The RAPD profiles showed a high diversity at the infraspecific level, except in the M. ciceri group. The nodC phylogeny resolved three symbiotic lineages. A small group of isolates had sequences identical to those of symbiovar ciceri and were only detected in M. ciceri isolates. Another group of sequences represented a novel symbiotic lineage that was associated with two particular chromosomal backgrounds. However, nodC sequences closely related to symbiovar loti predominated in most isolates, and they were detected in several chromosomal backgrounds corresponding to up to nine Mesorhizobium lineages. The results indicated that C. canariense is a promiscuous legume that can be nodulated by several rhizobial species and symbiotypes, which means it will be important to determine the combination of core and symbiotic genes that produce the most effective symbiosis.     

Association of a luminous Vibrio sp., taxonomically related to Vibrio harveyi, with Clytia linearis (Thornely, 1900) (Hydrozoa, Cnidaria)

A previously unknown association between a luminous Vibrio sp., taxonomically related to the species Vibrio harveyi and a common member of the shallow/mid water communities of the Mediterranean Sea, the hydrozoan Clytia linearis is described. All the specimens of C. linearis observed under blue light excitation showed both a natural luminescence appearing as a series of fine dots due to clytin, and a clear fluorescence on the external side of the perisarc around the colonies due to the presence of luminous bacteria. Luminous bacteria were isolated from the surface of C. linearis, their phenotypic characterization as isolates was performed by several morphological, biochemical, and cultural tests, completed with 16S rDNA sequence analysis. All the isolates were referred to a Vibrio sp. taxonomically related to V. harveyi. The association of the V. harveyi-related species with C. linearis, as already suggested for another hydroid, Aglaophenia octodonta, could be explained with the activity of these bacteria of feeding on the chitinous structures present in these hydroids. Moreover, the adhesion of the luminous bacterium (here referred to as Vibrio sp. CL1) on C. linearis may contribute to the survival of this Vibrio species in the marine environment providing a suitable growth habitat.     

Simultaneous study of particle reworking, irrigation transport and reaction rates in sediment bioturbated by the polychaetes Heteromastus and Marenzelleria

The present study employed simultaneously methods to investigate particle and solute transport and reaction rates in sandy sediments inhabited by two worms (2500 m^− 2) with different feeding modes. Heteromastus filiformis is a head-down deposit-feeder and the main activities exerted by this worm are transport of particles as faecal pellets from subsurface to surface sediments and burrow ventilation. Marenzelleria viridis is a surface deposit-feeder that actively searches for food by burrowing near the sediment surface, producing a network of ventilated galleries in this zone. M. viridis exhibited 1.5 to 2.2 times higher particle mixing rates (D_b = 3.3 to 4 × 10^− 3 cm^− 2 d^− 1) compared to H. filiformis. In M. viridis treatments, continuous advection (eddy diffusion) was the major factor influencing solute transport resulting in apparent diffusion rates (D_a = 2.2 cm^− 2 d^− 1), which were 3 times higher than molecular diffusion within the sediment. In H. filiformis inhabited sediments, the transport of solutes was discontinuous and driven by a surprisingly high nonlocal exchange (α = 1.1-1.3 d^− 1), emphasizing its strong irrigation effects. Accordingly, the enhancement of solute fluxes was more pronounced for H. filiformis compared to M. viridis. Depth integrated TCO₂ production derived from diagenetic modelling, which takes into account three reaction zones, is in good agreement with rates obtained from measured fluxes, indicating the applicability of both approaches to get reliable rates. However, the reaction rates showed that the presence of animals had a modest effect on microbial carbon oxidation. The results proved that transport conditions are deeply related to feeding modes. Exchange of solutes was the most important transport process by H. filiformis, while M. viridis affected both mixing and solute transport.     

Chemically induced predator avoidance behaviour in the burrowing bivalve Macoma balthica

The responses of the burrowing bivalves Macoma balthica and Cerastoderma edule to chemical cues emitted by feeding shore crabs Carcinus maenas were investigated. M. balthica held in the laboratory and exposed to chemical signals in effluent water discharging from tanks containing C. maenas fed 20 M. balthica day^− 1 reacted by increasing their burial depths from approximately 30 mm to depths of > 60 mm, over a period of several days. When the signal was removed the bivalves gradually returned to their original depth over 5 days. C. edule similarly exposed to effluent from crabs feeding on conspecifics showed no response. In an attempt to identify the signal inducing this burrowing response, M. balthica were exposed to a variety of chemical signals. Crabs fed M. balthica elicited the strongest response, followed by crabs fed C. edule. There were also small responses to effluent from crabs fed on fish, crabs previously fed on M. balthica and to crab faeces, but no responses to starved crabs, crushed M. balthica, or controls. We conclude that increased burrowing depth of M. balthica is induced by some as yet unidentified chemical cue produced by feeding crabs and is strongest when the crabs were fed on M. balthica. Unexpectedly, neither the presence of crabs themselves, nor of damaged conspecifics, was effective in eliciting a burrowing response. The mortality rates of M. balthica and C. edule selected by crabs when burrowed at normal depths and after exposure to effluent from feeding crabs were different. Crabs selected 1.5 times more C. edule than M. balthica when both species were burrowed at their normal depths, but 15 times more after the tanks had been exposed to effluent from feeding crabs for 5 days. The burrowing response of M. balthica thus appears to reduce mortality significantly by displacing predation pressure on to the more accessible C. edule.     

Responses of midgut amylases of Helicoverpa armigera to feeding on various host plants

Midgut digestive amylases and proteinases of Helicoverpa armigera, a polyphagous and devastating insect pest of economic importance have been studied. We also identified the potential of a sorghum amylase inhibitor against H. armigera midgut amylase. Amylase activities were detected in all the larval instars, pupae, moths and eggs; early instars had lower amylase levels which steadily increased up to the sixth larval instar. Qualitative and quantitative differences in midgut amylases of H. armigera upon feeding on natural and artificial diets were evident. Natural diets were categorized as one or more members of legumes, vegetables, flowers and cereals belonging to different plant families. Amylase activity and isoform patterns varied depending on host plant and/or artificial diet. Artificial diet-fed H. armigera larvae had comparatively high amylase activity and several unique amylase isoforms. Correlation of amylase and proteinase activities of H. armigera with the protein and carbohydrate content of various diets suggested that H. armigera regulates the levels of these digestive enzymes in response to macromolecular composition of the diet. These adjustments in the digestive enzymes of H. armigera may be to obtain better nourishment from the diet and avoid toxicity due to nutritional imbalance. H. armigera, a generalist feeder experiences a great degree of nutritional heterogeneity in its diet. An investigation of the differences in enzyme levels in response to macronutrient balance and imbalance highlight their importance in insect nutrition.     

Long-term storage of Ascosphaera aggregata and Ascosphaera apis, pathogens of the leafcutting bee (Megachile rotundata) and the honey bee (Apis mellifera)

Survival rates of Ascosphaera aggregata and Ascosphaera apis over the course of a year were tested using different storage treatments. For spores, the storage methods tested were freeze-drying and ultra-low temperatures, and for hyphae, freeze-drying, agar slants, and two methods of ultra-low temperatures. Spores of A. aggregata and A. apis stored well at −80 °C and after freeze-drying. A. aggregata hyphae did not store well under any of the methods tested while A. apis hyphae survived well using cryopreservation. Spores produced from cryopreserved A. apis hyphae were infective. Long-term storage of these two important fungal bee diseases is thus possible.     

Carbon and nitrogen relationships in the feeding and growth of the Pacific oyster, Crassostrea gigas (Thunberg)

Bivalve molluscs, in common with consumers in general, use behavioral and physiological mechanisms to balance metabolic requirements with available nutrients. This study considered how the Pacific oyster, Crassostrea gigas, meets the demands of growth and maintenance, measured in terms of carbon and nitrogen, in a variable food environment. Stoichiometry theory helped to evaluate: a) whether feeding behaviour modifies the intake of C and N given seasonal variability in food quality: b) how rates of metabolism and excretion, and C and N growth efficiencies, respond to mismatch between nutrient intake and the oysters' needs. Two field experiments in the Port Stephens estuary, near Sydney, Australia, measured feeding behaviour, metabolic and growth rates relative to seasonal changes in food supply. In a laboratory experiment, relationships between physiological rates and growth were measured to test a model of growth as a function of absorption of C and N. Potential metabolic targets for compensation were the C/N ratios of body tissues, maintenance and/or of soft tissue added as growth. C/N of whole soft issues varied little during the year (mean 5.4). In July (a time of low food availability of poor quality) growth was negligible and the C/N (maintenance) target was 6.7. In March (abundant food of high quality) growth was rapid with a high N-demand; the C/N of growth was 3.9. In November (medium food quality) there was an enhanced C-demand for glycogen storage; the C/N of growth was 7.9. Feeding behaviour changed the balance between C and N intake across months, primarily due to changes in the selection efficiency for nitrogen, which was highest at low filtration rates on particles of high C/N ratio. Nitrogen intake was favoured over C in July. In November, C-intake increased relative to N. In March, when abundant food nitrogen coincided with a high demand for growth, feeding behaviour was neutral with respect to C/N ratios. In all cases C/N of absorbed matter was greater than the C/N of growth. Growth efficiencies for carbon declined with increased C/N of ingested matter due to higher metabolic increments (SDA) when feeding on lower food quality; the metabolic costs of growth did not vary. In contrast, growth efficiencies for nitrogen did not alter with C/N for ingested matter, due in part to increased nitrogen losses, relative to tissue nitrogen content, when feeding on low C/N food. Nitrogen was therefore conserved metabolically relative to C. Both feeding and metabolic processes contributed to compensation for the mismatch between seasonally variable food quality and the demands of growth.