Differential olfactory perception of enantiomeric compounds by blind subterranean mole rats (Spalax ehrenbergi)

The behavior of mole rats (Spalax ehrenbergi) near pairs of enantiomeric compounds was examined in 901 two-choice experimental tests. Positioning of the nest and food store and the preferred location of the tested animal were used to assess attraction or aversion to the tested odorants. The results indicated that mole rats respond differentially to odors of stereoisomers (enantiomers of carvone, citronellol, and fechone). They responded to one enantiomer of each tested pair but were indifferent to or did not smell the other. Both sexes were attracted to the odor of R-(–)-carvone and repelled by the odor of (+)-citronellol. Females were attracted to the odor of (–)-fenchone while males had no preference. By contrast, all animals were indifferent to or did not smell the odor of S-(+)-carvone, (–)-citronellol, and (+)-fenchone. Further research to distinguish between these alternatives (indifference vs hyposmia/anosmia) is suggested.     

Selection for class II Mhc heterozygosity by parasites in subterranean mole rats.

Mhc organization and polymorphism have previously been studied in the four chromosomal species of the Spalax ehrenbergi superspecies in Israel, serologically, and at the DNA, RFLP and sequence levels of class I and class II genes. Here we demonstrate that the observed heterozygosity of Mhc class II genes P alpha 1 with 11 alleles, and Q beta, with at least 14 alleles, is positively and significantly correlated with infectivities of ectoparasites (gamasid mites) and endoparasites (helminths). Mhc heterozygosity is highest in the most infected area, which is in the most humid-warm region of the superspecies range, or where two zoogeographic regions overlap. We conclude that the evolutionary forces responsible for the Mhc class II two-gene polymorphisms include selection for increased heterozygosity as a defense strategy against ecto- and endoparasite infections.     

Magnetic compass orientation in the subterranean rodentCryptomys hottentotus (Bathyergidae)

Summary To test whether mole-ratsCryptomys hottentotus were able to use the magnetic field for orientation, laboratory experiments were conducted which were based on the animals' spontaneous tendency to build their nests at the same position in a circular arena. In the local geomagnetic field, the animals preferred the SE-sector. When magnetic north was turned by 120^o or by 180^o, the mole-rats changed their nest position accordingly. This clearly shows that they can use the magnetic field for direction finding.     

Selection for resistance to azadirachtin in the green peach aphid,Myzus persicae

Two lines ofMyzus persicae of the same origin were treated repeatedlywith pure azadirachtin (aza), or a refined neem seed extract (NSE), at the equivalent concentration of aza. After 40 generations, the aza-selected line had developed 9-fold resistance to aza compared to a non-selected control line, whereas the NSE-selected line did not. These results suggest that a blend of active constitutents in a botanical insecticide such as neem might diffuse the selection process, mitigating the development of resistance compared to that expected with a single active ingredient.     

Individual recognition and incest avoidance in eusocial common mole-rats rather than reproductive suppression by parents

Non-reproductive females in families of eusocial common mole-rats (Cryptomys sp., Rodentia) are not suppressed by their mother, (either behaviourally or pheromonally) as is generally assumed. They do not mate with their father and brothers simply because they are not sexually attractive for them (and vice versa). The incest avoidance is based on the capability to recognize (and keep in memory for up to three weeks) each family member individually. A sterile daughter may conceive and deliver young in her parental family if given the opportunity to mate with an unfamiliar mate in a separate cage. In this way, two females may breed side by side in one family.     

Host tree unsuitability recognized by pine shoot beetles in flight

Summary In spring, the landing rate of flying European pine shoot beetles,Tomicus piniperda L., on injured Scots pine diminishes as colonization continues. This is due to olfactory cues that indicate progressive host degradation. Verbenone was shown to play a role in the beetle's recognition of this unsuitability of a formerly suitable host, since the compound was increasingly released from colonized tree sections as they aged, but not from uninfested sections. Also, the release of verbenone at natural rates in the forest inhibited the attraction of beetles to host monoterpenes.     

Vitamin B12 amplifies circadian phase shifts induced by a light pulse in rats

Vitamin B₁₂ (VB₁₂) is a putative modulator of the human circadian clock, improving entrainability to the 24 h light-dark cycle. The present study was intended to elucidate the mechanism of VB₁₂ action in an animal model. In male rats free-running under constant dim illumination, a single light pulse of 50–1000 lux for 20 min given at circadian time (CT) 20 induced a 0.28 to 1.08 h phase advance and at CT 14 induced a 0.54 to 2.10 h phase delay. A 3 h intracerebroventricular (icv) infusion of 30 nmol VB₁₂ starting 2 h prior to a 20 min 200 lux light pulse significantly amplified phase shifts in comparison with saline-treated or untreated controls. The mean phase advance (1.13 h) was 1.8-fold greater than that of saline-infused controls, whereas the mean phase delay (2.28 h) was 2.9-fold greater. These values were comparable to the maximal phase shifts caused by 1000 lux light pulses in untreated rats. Since the same VB₁₂ treatment alone had failed to induce a phase shift in a previous experiment, these results indicate that VB₁₂ strongly enhanced light pulse-induced phase shifts and thus augmented the entrainability of the circadian clock to light.     

Suppression of chaos by periodic oscillations in a model for cyclic AMP signalling inDictyostelium cells

We investigate how the introduction of cells oscillating periodically affects the behaviour of a suspension ofDictyostelium discoideum amoebae undergoing chaotic oscillations of cyclic AMP. The analysis of a model indicates that a tiny proportion of periodic cells suffices to transform chaos into periodic oscillations in such suspensions. A similar result is obtained by forcing the aperiodic oscillations by a small-amplitude, periodic input of cyclic AMP. The results provide an explanation for the observation of regular oscillations in suspensions of a putatively chaotic mutant ofDictyostelium discoideum ¹². More generally, the results show how chaos in biological systems may disappear through the coupling with periodic oscillations.