The effect of food availability, female culture-density and photoperiod on ephippia production in Daphnia magna Straus (Crustacea: Cladocera)

SUMMARY. A method is described whereby ephippia (sexual eggs plus protective membranes) are experimentally induced at low food levels (≤ 0.05 mg spinach D. magna ^-1), high female culture-densities (≤ 0.4 D. magna ml^-1) and in short-day photoperiods (L:D < 12:12, 12°C). The density-dependent ephippial response was related to an increased encounter rate between females at the higher densities. External metabolites had no significant effect on ephippia production. Ephippia were formed in the second generation after exposure to short day-lengths. Five clones from the same population exhibited genetic variation in their critical photoperiods for induction of sexual reproduction (≥= 10% ephippia). There was evidence of a genetic difference in photoresponse between two populations of D. magna. The evolution of timing mechanisms for ephippia production are discussed in relation to the predictability of environmental change.     

Relationship between Serum Gold Content and Distribution to Serum Immunoglobulins and Complement<Superscript>*</Superscript>

A protein, which consists of a defined sequence of amino-acids, can be converted into another protein of equal length by changes in the sequence of nucleotides in the segment of DNA by which it is coded. It is convenient to term this segment a gene. Most proteins are 200–400 amino-acids long, so that most genes, if defined in this way, are represented by 600–1,200, or about 10³, nucleotides. The evolution of protein molecules may appear to be limited by the need for each step in the sequence to be at a selective advantage. Maynard Smith¹ has compared this with a word game in which, using exclusively meaningful words, one word has to be changed to another by altering one letter at a time.     

The virobacterial agglutination test as a rapid means of detecting cocoa swollen shoot virus

The virobacterial agglutination (VBA) test was developed as a means of detection of cocoa swollen shoot virus (CSSV). Identification of CSSV-infected Theobroma cacao in the field has only been possible by visual examination of symptoms, by virus transmission using mealybugs and by grafting to induce symptom expression in Amelonado cocoa seedlings. Detection of latent infection has not been possible even using enzyme-linked immunosorbent assays (ELISA). The VBA test successfully detected CSSV in infected sap diluted to 1/2560. Antisera to a range of mild and severe CSSV isolates were tested, and the results suggest a close relationship between seven isolates (1A, Bosomtwi, Bosomuoso, Nkrankwanta, Nsaba, Seidi-Nkawie and SS365B) while the mild isolate N1 appears to be less closely related. The VBA test was compared with both direct and indirect ELISA in the field. Only VBA detected all the cocoa trees which were known to be infected and additionally identified infection in many symp-tomless trees.     

Designating Seasonality Using Rate of Movement

ABSTRACT Traditionally, seasons for animals have been designated based on single external variables such as climate or plant phenology, rather than an animal's response to the dynamic environments within which it lives. By interpreting a rate of movement function of cumulative movement through time we established a method that distinguishes transitions between behaviors limited by winter habitat conditions from those present during summer. Identification of these time periods provides temporal definition to subsequent home-range analyses and use-availability comparisons. We used location data from 32 Global Positioning System-collared female moose (Alces alces) to demonstrate the method. We used model selection (Akaike's Information Criterion) to differentiate between candidate rate of movement response curves. Of 32 moose, 29 clearly conformed to an annual movement pattern described by a logistic curve, with increased rates of movement in summer compared to winter. Conversely, 3 aberrant individuals did not alter their movement rate through the year and were best fit with a linear response curve. The seasonal rate of movement model we developed suggests an average summer period of 122 days (median = 119 days, range = 96–173 days) for moose in northwestern Ontario, Canada. The rate of movement model we applied to individuals indicated 1 May as the median date for the winter-summer transition (range = 2 Apr–24 May), and the median transition from summer to winter was 25 August (range = 1 Aug–23 Oct). Wide variation in timing and duration of summer and winter seasons among individuals demonstrates potential failure of the single external variable approach to capture the suite of factors potentially influencing animal behaviors. By plotting cumulative distance moved throughout the year, we elucidated individual variation in response to known and unknown variables that affect animal movement. Accounting for variability among individuals in designation of biologically significant temporal boundaries is critical to delineation of seasonally important habitats for conservation and sustainability of healthy wildlife populations.     

The promotion of ear emergence by gibberellic acid in Ethrel-induced male sterile wheat

Ethrel at a concentration of 2000 ppm active ingredient (a.L), applied to the spring wheat cv. Sirius before meiosis was initiated in the oldest florets of the ears, induced almost complete male sterility but prevented full ear emergence. Concentrations of 100, 200 and 300 ppm a.i. GA₃, applied 2 or 5 days after the Ethrel, were equally effective in promoting full emergence of sterilized ears, without affecting female fertility or markedly affecting flowering time.     

New species of Stygiopontius (Copepoda, Siphonostomatoida) from a deep–sea hydrothermal vent at the East Pacific Rise

Three dirivultid copepods, Stygiopontius puxillifer sp.n . and S. appositus sp.n., unusual in having pegs along the ventral edges of the cephalosome, and S. lurniger sp.n., distinguiahcd from congeners by the modificd thorn-like seta on the second segment of the maxilliped, arc dcscrihcd from a depth of 2616 m at 21°N in the eastern Pacific.     

Evidence for mate‐encounter Allee effect in an invasive longhorn beetle (Coleoptera: Cerambycidae)

1. Limited empirical support is available for mate‐encounter Allee effects in invasive insects due to the logistical challenges of studying demographic trends in low‐density populations. 2. Traps baited with pheromone and spruce volatiles were used to monitor the abundance of female Tetropium fuscum F. (Coleoptera: Cerambycidae) at multiple sites in Nova Scotia in 2011 and 2012. Each female was dissected to determine the presence or absence of sperm in its spermatheca (mated or virgin female, respectively). 3. Both male and total T. fuscum abundance declined with increasing distance to the focal point of T. fuscum's invasion. Female mating probability declined with male abundance and with distance from the invasion focus, and mating probabilities were very low at the most peripheral sites. Difficulty in encountering mates may thus contribute to limiting the spread of T. fuscum. 4. The approach outlined here could be integrated into existing surveys of wood borers using traps baited with semiochemicals to improve our understanding of the role of the mate‐encounter Allee effect in invasion dynamics.