The evolutionary stability of attenuators that mask information about animals that social partners can exploit

Signals and cues are fundamental to social interactions. A well‐established concept in the study of animal communication is an amplifier, defined as a trait that does not add extra information to that already present in the original cue or signal, but rather enhances the fidelity with which variation in the original cue or signal is correctly perceived. Attenuators as the logical compliment of amplifiers: attenuators act to reduce the fidelity with which variation in a signal or cue can be reliably evaluated by the perceivers. Where amplifiers reduce the effect of noise on the perception of variation, attenuators add noise. Attenuators have been subject to much less consideration than amplifiers; however, they will be the focus of our theoretical study. We utilize an extension of a well‐established model incorporated signal or cue inaccuracy and costly investments by emitter and perceiver in sending and attending to the signal or cue. We present broad conditions involving some conflict of interest between emitter and perceiver where it may be advantageous for emitters to invest in costly attenuators to mask cues from potential perceivers, and a subset of these conditions where the perceiver may be willing to invest in costly anti‐attenuators to mitigate the loss of information to them. We demonstrate that attenuators can be evolutionary stable even if they are costly, even if they are sometimes disadvantageous and even if a perceiver can mount counter‐measures to them. As such, we feel that attenuators of cues may be deserving of much more research attention.     

Initiation of Flowering and Changes in Endogenous Inhibitors and Promoters in Olive Buds as a Result of Chilling

Olive trees require a period of chilling temperatures, either diurnally fluctuating, or at a constant—but definite—level before inflorescences develop. In this study, bud and leaf samples were taken at weekly intervals during this critical period from trees receiving temperatures favorable for flowering and from trees under temperature conditions known to prevent flowering. Extracts were obtained from these samples, separated by paper chromatography and the different growth-active materials were bioassayed by the mung bean rooting test for the presence of promoters and inhibitors. Extracts from buds on trees under conditions unfavorable for flowering generally consisted only of promoters. Extracts from buds on trees placed under conditions favorable for flowering showed a definite and consistent pattern for the presence of rooting inhibitors and promoters. Within one or two weeks after being placed under such conditions a strong inhibitor band appeared from R_f 0.50 to 0.70. This persisted for 6 to 7 weeks, gradually decreasing in intensity, followed by promoters at these bands. During this period all other bands, at different R_f values, showed strong promoters. Extracts from leaves on shoots under temperature regimes favorable for flowering showed a pattern like the buds in the appearance and disappearance of inhibitors and at the same R_f values but with about one week lag in time. Bud extracts from defoliated shoots on trees under temperature conditions known to result in inflorescence production failed to show the characteristic inhibitor pattern associated with flowering. Such defoliated shoots do not form inflorescences.     

A class of ompA mutants of Escherichia coli K12 affected in the interaction of ompA protein and the core region of lipopolysaccharide

Summary A group of ompA mutants of Escherichia coli K12 are described which were sensitive to bacteriophage K3 in a background wild-type for lipopolysaccharide (LPS). With mutant LPS in vivo (lacking some core sugar residues), however, the ompA mutations gave resistance to K3. Outer membrane levels of OmpA protein were normal or near-normal when the mutations resided in either wild-type or mutant LPS backgrounds. Strains in which the mutations occurred in a wild-type LPS background adsorbed K3 phage at the same initial rate and to the same extent as a wild-type strain, but the efficiency of plaquing of the adsorbed K3 was reduced to 25–50% of wild-type levels. Under conditions where a wild-type strain irreversibly adsorbed over 90% of available phage K3 within 3 min, double mutants (ompA mutant, LPS mutant) left 90% of the phage viable after 1h. The 10% of inactivated phage did not form plaques.     

Diagnosis of pregnancy in the ewe at mid-gestation

Detection of the pregnancy-specific antigen, chorionic somatomammotrophin in serum was applied to the diagnosis of pregnancy in a commercial-type flock of 286 sheep 70 days after joining with rams. At the time of testing the ewes were between Days 47 and 70 of pregnancy. Based upon lambing results, the positive diagnoses were 97% correct. However, the accuracy in diagnosing non-pregnancy, which rose from 85% when all the ewes (Day 47–70) were considered to 99% after Day 55, suggest that some pregnant ewes whose stage of pregnancy was earlier than Day 55 were not being detected and were wrongly designated non-pregnant. This pregnancy test can be successfully used from Day 55, although a correct prediction of pregnancy was made in 40 ewes between Days 47 and 54.