Effect of crab effluent and scent of damaged conspecifics on feeding,growth, and shell morphology of the Atlantic dogwhelk Nucella lapillus (L.)

Juvenile Nucella lapillus of two different shell phenotypes, exposed shore and protected shore, were maintained in running seawater under each of three experimental conditions for 94 d: a) laboratory control, b) exposed to the effluent of crabs (Cancer pagurus) fed frozen fish (fish-crab), and c) exposed to the effluent of crabs fed live conspecific snails (snail-crab). Rates of barnacle consumption and rates of body weight change varied significantly between phenotypes and among experimental conditions. Individuals from the protected-shore consumed consistently fewer barnacles and grew consistently less than those from the exposed shore. Body weight increases in the fish-crab treatments were from 25 to 50% less than those in the controls and body weights in the snail-crab treatment either did not change or actually decreased. The perceived risk of predation thus appears to have a dramatic effect on the rates of feeding and growth of N. lapillus.At the end of the experiment, size-adjusted final shell weights for both phenotypes were consistently higher than controls (no crab) in both the fish-crab and snail-crab treatments. In addition, apertural tooth height, thickness of the lip, and retractability (i.e. the extent to which a snail could withdraw into its shell), with few exceptions all varied in an adaptive manner in response to the various risk treatments. Similar changes in the shell form of starved snails exposed to the same stimuli suggest very strongly that the morphological responses of both phenotypes were not just due to differences in rates of growth. These differences, at least in part, represented a direct cueing of the shell form of Nucella lapillus to differences in the perceived risk of predation. Somewhat surprisingly, the extent of phenotypic plasticity appeared to differ between the populations examined. Both field and laboratory evidence suggest that the exposed-shore population was much more labile morphologically than the protected-shore population.In many instances, particularly among starved snails, the development of antipredatory shell traits was greater in the fish-crab treatment than in the snail-crab treatment. Because the scent of crabs was present in both treatments, these results suggest a) that, at the frequency/concentration used in the experiments, the scent of damaged conspecifics may have been a supernormal stimulus and b) that the morphological response in these treatments might have been greater if the stimulus had been provided at a lower level.     

Improved methods of cultivation and production of deuteriated proteins from E. coli strains grown on fully deuteriated minimal medium

AIMS: The aim was to develop reliable and economical protocols for the production of fully deuteriated biomolecules by bacteria. This required the preparation of deuterium-tolerant bacterial strains and an understanding of the physiological mechanisms of acquisition of deuterium tolerance. METHODS AND RESULTS: We report here improved methods for the cultivation of Escherichia coli on fully deuteriated minimal medium. A multi-stage adaptation protocol was developed; this included repeated plating and selection of colonies and resulted in highly deuterium-tolerant cell cultures. Three E. coli strains, JM109, MRE600 and MRE600Rif, were adapted to growth on deuteriated succinate medium. This is the first report of JM109 being adapted to deuteriated minimal media. The adapted strains showed good, consistent growth rates and were capable of being transformed with plasmids. Expression of heterologous proteins in these strains was reliable and yields were consistently high (100-200 mg l-1). We also show that all E. coli cells are inherently capable of growth on deuteriated media. CONCLUSIONS: We have developed a new adaptation protocol that resulted in three highly deuterium-tolerant E. coli strains. Deuterium-adapted cultures produced good yields of a deuteriated recombinant protein. We suggest that E. coli cells are inherently capable of growth on deuteriated media, but that non-specific mutations enhance deuterium tolerance. Thus plating and selection of colonies leads to highly deuterium-tolerant strains. SIGNIFICANCE AND IMPACT OF STUDY: An understanding of the mechanism of adaptation of E. coli to growth on deuteriated media allows strategies for the development of disabled deuterium-tolerant strains suitable for high-level production of deuteriated recombinant proteins and other biomolecules. This is of particular importance for nuclear magnetic resonance and neutron scattering studies of biomolecules.     

Enumeration of anaerobic oxalate-degrading bacteria in the ruminal contents of sheep

Abstract Concentrations of oxalate-degrading anaerobes in ruminal contents of sheep were determined from counts of colonies producing clear zones on a calcium oxalate medium (D agar with 7 mM CaCl₂). Viable counts of oxalate degraders from a 55-kg sheep fed a diet containing 32% halogeton (4.6% oxalate) averaged 2.6 × 10⁶/ g (dry weight). When the halogeton concentration in the diet was reduced to 16%, counts of oxalate degraders decreased nearly 300-fold. Oxalate-degrading isolates from this sheep were similar to OxB, the type strain of Oxalobacter formigenes . When a 45-kg sheep was fed diets containing 2.2, 1.5, and 0.8% oxalate, viable counts of oxalate degraders (enumerated on D agar with 14 mM CaCl₂ and 20% filter-sterilized ruminal fluid) represented 0.85, 0.52, and 0.06% of the total viable population, respectively; total viable counts were essentially unchanges by these concentrations of dietary oxalate. Similar percentages of oxalate degraders were also observed when a 23-kg sheep was fed diets containing 1.5 or 0.8% oxalate. This report presents the first direct measurements of the concentrations of oxalate-degrading bacteria in the rumen and supports the concept that the availability of oxalate in the diet influences the proportion of oxalate-degrading bacteria in the rumen     

Behavioral adaptations of two phytophagous insects feeding on two species of phototoxic Asteraceae

Two phototoxic plants of the Asteraceae family were studied in relation to species of phytophagous insects for which they are hosts:Argyrotaenia velutinana Wlk. feeding onChrysanthemum leucanthemum L. andChlorochlamys chloroleucaria (Guenée) colonizingRudbeckia hirta L. The toxicity of these two plants is related to the presence of acetylenes and thiophenes that induce a light-mediated production of deleterious singlet oxygen and other free radicals (phototoxicity). Results showed that females ofA. velutinana laid their eggs preferentially in the shade and the larvae adopted hiding behaviors, such as bending of ligulate corollas and silk spinning to build opaque shelters. By avoiding direct exposure to the sun, both behaviors may reduce phototoxicity associated with ingested plant materials. Furthermore, larvae ofC. chloroleucaria demonstrated a preference in the field for pollen, which constitutes a nonphototoxic tissue of their host plant. Experimental alterations of these specific behaviors induced important biological consequences for larvae of both insects such as mortality or reduction of larval growth rate. These results reinforce the idea that behavior may constitute an efficient adaptation to avoid phototoxicity.     

Morphological changes in an acidophilic bacterium induced by heavy metals

The Acidiphilium strains inhabit acidic mine regions where they are subjected to occasional environmental stresses such as high and low temperatures, exposure to various heavy metals, etc. Change in morphology is one of the strategies that bacteria adopt to cope with environmental stresses; however, no study on this aspect has been reported in the case of Acidiphilium sp. This work is an attempt using the acidophilic heterotrophic bacterium Acidiphilium symbioticum H8. It was observed that the maximum alterations in size occurred when the bacterium was exposed to sub-inhibitory concentrations of Cu and Cd. Loosely packed coccobacillus-type normal cells formed characteristic chains of coccoidal lenticular shape with constrictions at the junctions between them in the presence of Cd; Cu induced transformation of cells to become round shaped; Ni caused the cells to aggregate, but Zn showed no effect. Respective metal depositions on the cell surface were confirmed by scanning electron microscopy equipped with energy dispersive X-ray analysis. Cell bound Ca²⁺ ions were replaced by these metal ions and measured by inductively coupled plasma mass spectrometry from the culture filtrate. Cell shape changed only after the addition of sub-inhibitory concentrations of the metals, but in growth inhibitory concentrations it was similar to the normal cells.     

Autecological investigations on marine diatoms. 5:Coscinodiscus concinnus W. Smith andRhizosolenia setigera Brightwell

The cold oligo-eurytherm diatomsCoscinodiscus concinnus W. Smith andRhizosolenia setigera Brightwell were cultured to determine their best competitive position by growth. Comparison of their generation times with those of other diatoms indicate that they reach this position between 6°C and 12°C. Both species grew between –1.5°C and about 20°C. The experiments indicate thatC. concinnus flowerings are possible in a deep water column, during periods of high light intensities. The simultaneous death of species in the upper layer is also caused by high light intensities.C. concinnus appeared in two morphological forms; the normal voluminous form, and a flatter form with a few intercalary bands only, filled with large oil-droplets. The latter appeared at 0°C and below, and at the upper temperature limit for growth of about 19°C–20°C. The separation of nov. spec. fromC. concinnus based on the absence or presence of a hyaline area and intercalary bands as identification characteristics should be reconsidered.     

Availability,uptake and regeneration of phosphate in mesocosms with varied levels of P deficiency

A population of cyclomorphic Bosmina coregoni was studied in Lake Östersjön, southwestern Sweden and results from field samples collected in 1988, 1989, 1990 and 1991 are presented. Animals collected in summer have remarkably higher carapace and prolonged antennule compared to what we call the normal morph. In 1991 the extreme morph reach its maximum body length, body height and antennule length in July to September. The occurrence of the extreme morph coincide with the hatching of the predaceous cladoceran Leptodora kindtii.The two morphs fluctuate in abundance and in relation to each other. In early spring only the normal morph occurred in the samples followed by a period of about two months when the two morphs were found together, in July only the extreme morph was found. In September the two morphs were again present in the lake. As has been shown for other cladoceran, the conspicuous carapace and antennule could be an adaptive response that decreases mortality due to invertebrate predation. Spectacular features like these are likely also accompanied by some sort of costs.     

Further expansion of the genus Cercopagis (Crustacea,Branchiopoda, Onychopoda) in the Baltic Sea,with notes on the taxa present and their ecology

The onychopod cladoceran Cercopagis that recently invaded the Baltic Sea is reported from new zones of the northern Baltic proper. Because of successful survival and an expanding distribution range, the addition of Cercopagis to the Baltic fauna is considered to be permanent. What has previously been cited as Cercopagis pengoi encompasses the morphology of several other species, subspecies and forms. Either a number of morphologically similar species is present, or there is a number of spurious species in Cercopagis. The last hypothesis is favoured. The spatial distribution pattern of Cercopagis, as well as that of total zooplankton, was correlated with depth. Deep (>100 m) and shallow (<10 m) stations had significantly lower abundance than stations of intermediate depth (<100 m). An overview of the distribution of C. pengoi group in fresh and brackish waters suggests a high tolerance to environmental factors, but with differences among taxa. Due to this ecological flexibility, the colonization of the Baltic is not unexpected. Increasing salinity may restrict dispersal of cercopagids to the southern areas of the Baltic and to the North Sea, but inland lakes (e.g. in Sweden) present an ecological profile suitable for colonization.     

Findings of new and rare fish species in the coastal zone of the Crimea (the Black Sea)

Characteristics of seven Atlantic-Mediterranean fish species are provided. Of them, four (gobies—yellow-headed Gobius xanthocephalus and red-mouthed G. cruentatus, incognito blenny Parablennius incognitus, and greater pipefish Syngnathus acus) were either first found in the Black Sea coastal zone of the Crimea, or their findings were doubted, and three species (thin-lipped grey mullet Liza ramada, European barracuda Sphyraena sphyraena, and Black Sea salmon Salmo trutta labrax) are very rare. Over the last decade, the authors recorded 15 fish species; of them, seven Atlantic-Mediterranean species have dispersed along the Crimean coasts by now, one endemic of the far eastern seas (chameleon goby Tridentiger trigonocephalus) has naturalized in Sevastopol Bay, four invading species, freshwater by origin, permanently occur in the estuary zones of the peninsula; the remaining three species are known from single findings and apparently belong to the category of accidental fish. An increase in the species composition of ichthyofauna off the Black Sea coasts of the Crimea results from the on-going process of mediterranization—the invasion in the estuary of freshwater tolerant species at the expense of accidental species that penetrated here either independently or with ballast waters.     

A free lunch? No cost for acquiring defensive plant pyrrolizidine alkaloids in a specialist arctiid moth (Utetheisa ornatrix)

Many herbivorous insects sequester defensive chemicals from their host plants. We tested sequestration fitness costs in the specialist moth Utetheisa ornatrix (Lepidoptera: Arctiidae). We added pyrrolizidine alkaloids (PAs) to an artificial diet at different concentrations. Of all the larval and adult fitness components measured, only development time was negatively affected by PA concentration. These results were repeated under stressful laboratory conditions. On the other hand, the amount of PAs sequestered greatly increased with the diet PA concentration. Absence of a detectable negative effect does not necessarily imply a lack of costs if all individuals express the biochemical machinery of detoxification and sequestration constitutively. Therefore, we used qPCR to show that expression of the gene used to detoxify PAs, pyrrolizidine‐alkaloid‐N‐oxygenase (pno), increased 41‐fold in our highest PA treatment. Nevertheless, fitness components were affected only slightly or not at all, suggesting that sequestration in this species does not incur a strong cost. The apparent lack of costs has important implications for our understanding of the evolution of ecological interactions; for example, it implies that selection by specialist herbivores may decrease the levels of certain chemical defences in plant populations.