Plastic inducible morphologies are not always adaptive: The importance of time delays in a stochastic environment

Summary We present a mathematical model for predicting the expected fitness of phenotypically plastic organisms experiencing a variable environment. We assume that individuals experience two discrete environments probabilistically in time (as a Markov process) and that there are two different phenotypic states, each yielding the highest fitness in one of the two environments. We compare the expected fitness of a phenotypically fixed individual to that of an individual whose phenotype is induced to produce the better phenotype in each environment with a time lag between experiencing a new environment and realization of the new phenotype. Such time lags are common in organisms where phenotypically plastic, inducible traits have been documented. We find that although plasticity is generally adaptive when time lags are short (relative to the time scale of environmental variability), plasticity can be disadvantageous for longer lag times. Asymmetries in environmental change probabilities and/or the relative fitnesses of each phenotype strongly influence whether plasticity is favoured. In contrast to other models, our model does not require costs for plasticity to be disadvantageous; costs affect the results quantitatively, not qualitatively.     

Studies on the role of abscisic acid in the initiation of bud dormancy in Alnus glutinosa and Betula pubescens

Summary The effects of leaf-applied (+-)-abscisic acid on the growth and dormancy of Betula pubescens Ehrh. and Alnus glutinosa Gaertn. growing under long days provide no evidence that leaf-applied abscisic acid induces or promotes the formation of resting buds in these species. Radiotracer studies show that a small percentage of the radioactivity applied as [2-¹⁴C]abscisic acid to the leaves accumulates in the apical region of the shoot. Of the radioactivity that was recovered from this region after 8 days, less than 10% was chromatographically similar to [2-¹⁴C]abscisic acid. The significance of these results with respect to the role of abscisic acid in regulating the induction of bud dormancy is discussed.Abbreviation ABA abscisic acid     

Epidemiological Tracing of Pseudomonas aeruginosa: Antibiogram and Serotyping

The spread of a particular strain of Pseudomonas aeruginosa through a pediatric burn unit was monitored using serological typing and antibiotic susceptibility data.     

Immunocytochemical localization of soluble protein in the adrenal medulla

Synopsis An indirect immunocytochemical technique (Nakane, 1970) was employed to localize the soluble proteins purified from lysates of catecholamine (CA)-containing vesicles of the bovine adrenal medulla. Antiserum to the proteins, produced in rabbits, was used for incubation of sections of bovine adrenal tissue prepared by fixation in glutaraldehyde and embedding in serum albumin (McLean & Singer, 1970). The site of the antigen-antibody complex was visualized by incubating the sections with anti-rabbit -globulin (goat) conjugated to peroxidase, followed by the deposition of electronopaque reaction product generated by the enzyme. The reaction product, also visible at the level of the light microscope, appeared to have a distribution similar to that of the CA-storage vesicles. Electron microscopic examination revealed that nearly all the reaction product was deposited over the electron-opaque core of the vesicles. The intravesicular localization is consistent with the proposal that these proteins exist primarily in the CA-containing granular vesicle and may function to stabilize the CA-storage complex.     

Phosphatase Activity Among Candida Species and Other Yeasts Isolated from Clinical Material

A group of 277 yeasts isolated from burned children and 14 reference strains were tested for phosphatase activity by using phenolphthalein phosphate substrates. Phosphatase activity was widely distributed among various species and strains representing seven genera. Candida albicans, which was the most common yeast isolated from clinical material, was notably absent in producing the enzyme, whereas Candida tropicalis was the most consistent, strong, and rapidly active phosphatase-producing organism. The characteristic enzyme activity of a selected isolate of C. tropicalis was demonstrated in the presence of concentrations of inorganic phosphate which inhibited enzyme activity of other species. The greater enzyme activity of C. tropicalis was not related to more rapid or greater cell growth or decrease in the pH of culture media. Extracellular constitutive heat-labile acid phosphatase was found in broth filtrates of C. tropicalis, C. krusei, and a strain of Staphylococcus aureus.     

Behaviour of Aedes mosquitos in relation to blood-feeding and repellents

About four thousand females of Aedes aegypti (L.) and two thousand of several Canadian species of Aedes were studied in the field and the laboratory. Their behaviour in relation to a host and to repellent chemicals was divided into eight phases and the conditions influencing them as well as the stimuli responsible for the initiation, inhibition, and termination of these phases were investigated; orientation was also considered. The factors studied include surface temperature, convective and radiant heat, light and colour, moisture, wind, odour, taste, gravitation, sound, and movement. The relevance of these results for the development of improved mosquito repellent chemicals is discussed.

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Zusammenfassung Weibchen von Aedes aegypti sowie einiger Kanadischer Aedes-Arten wurden im Freien und im Laboratorium beobachtet. Ihr Verhalten in bezug auf verschiedene Opfer und auf abstossende Substanzen wird in die folgenden acht Phasen unterteilt: Ruhe, Flug, spontanes Suchen im Flug, Landung auf dem Wirt, Suchen zu Fuss, Untersuchung mit dem Rüssel und Stich. Die Hierarchie dieser Verhaltensweisen sowie ihre gewöhnliche Aufeinanderfolge werden diskutiert. Die oben beschriebene Reihenfolge scheint die natürlichste und ist vermutlich am häufigsten. Aber je nach den Umständen kommen auch andere Teilfolgen vor und insbesonders können einzelne Phasen ausbleiben. Unter den für die einzelnen Verhal-tensweisen — oder besser gesagt Verhaltensübergänge — massgebenden Faktoren wurden Oberflächentemperatur, Konvektions- und Strahlungswärme, Licht, Farbe, Feuchtigkeit, Geruch, Geschmack, Schwerkraft, Schall und Bewegung geprüft und in bezug auf ihre Effekte untersucht.Die Bedeutung dieser Ergebnisse und der gesamten Problemstellung für die Ausarbeitung verbesserter Mücken-abstossender Chemikalien wird diskutiert. Offensichtlich ist das Problem des Schutzes gegen Insektenstiche nicht einfach eine Frage der Chemie und kann nicht durch das übliche Herumprobieren mit gekäfigten Mücken gelöst werden. Prinzipiell können die Verhaltensketten sowohl der weiblichen Mücke als auch des Menschen, die gemeinsam zum Stiche führen, an mehreren Stellen und in mannigfaltiger Weise unterbrochen werden, und zwar sowohl im Freien als auch in Häusern oder Zelten. Unter diesen Möglichkeiten ist der Gebrauch abstossender Substanzen nur eine, wenn auch wichtige Hilfe.Aber selbst auf diesem beschränkten Gebiet müssen mehr Variable berücksichtigt werden, als dies gewöhnlich geschieht. Die Entscheidung, ob eine Mücke sticht oder nicht, kann als Ergebnis eines Wettstreits antagonistischer Faktoren verstanden werden. In diesem Zusammenhang ist es wichtig, dass die gleichen Substanzen, z.B. in Abhängigkeit von der Konzentration, abstossend oder anziehend wirken können, und dass sie die verschiedenen Verhaltensphasen nicht immer gleichsinnig beeinflussen, sodass etwa eine Substanz, die das Stechen verhindert, nicht auch das Niederlassen unterbinden muss. Endlich muss man in Betracht ziehen, dass sowohl der Stechtrieb der Mücken als auch die Anziehung durch das Opfer mannigfaltigen und komplizierten Schwankungen unterliegen, von denen nur einige bekannt sind.

     

The ecology of terrestrial invertebrates on Pacific salmon carcasses

In coastal streams throughout the north Pacific region, spawning salmon (Oncorhynchus spp.) subsidize terrestrial communities with their nutrients and carcasses. We document the previously unreported composition and ecology of terrestrial invertebrates using salmon carcasses in forest habitats from two high salmon density watersheds in coastal British Columbia. From experimental placement of 186 carcasses, terrestrial Diptera-dominated salmon carcass decay (85.5% of carcasses). Overall, we recorded over 60 species from salmon carcasses, including saprophagous Diptera and Coleoptera (15 spp.), dipteran predators (eight spp.) and parasitoids (four spp.), and opportunistic predators, scavengers, and detritivores (24 spp.). Using stable isotopes of nitrogen and carbon, we reconstruct the dietary niches of select species relative to salmon muscle tissue and previously sampled non-salmon feeding invertebrate species. From comparisons across seasons, sampling locations and larval and adult life stages, we find evidence for a diet of salmon tissue in flies (Calliphora terraenovae and Dryomyza anilis), and beetles (Nicrophorus investigator and Anthobium fimetarium). The parasitic wasps Alysia alticola and Atractodes sp. had the highest levels of enrichment of all species, representing their larval diet of fly larvae that have fed on salmon carcasses 1 year prior to adult wasp sampling. Temporal and spatial isotopic variation in insect indicator species varies by species mobility and the pathway of salmon nutrient uptake. Cataloguing these associations may be useful for developing indices of intact salmon runs, bear foraging, and subsequent nutrient transfer in coastal watersheds.