Does the rock hyrax,Procavia capensis,conform with Bergmann's rule?

Size variation of the skull of the rock hyrax, Procavia capensis , in southern Africa was related to several temperature parameters. All the four skull parameters examined were significantly correlated with temperature. The highest correlation was with the mean maximal temperature and the lowest with temperatures of the coldest month (July). These results are interpreted that the rock hyrax adapted morphologically to high temperatures, but avoids exposure to low temperatures by behavioural mechanisms such as hiding in caves.     

Analysis of the distribution of insectivorous bats in Israel

Data on localities from which insectivorous bats were collected or sighted in Israel were compiled into a Geographical Information System (GIS) in order to analyse patterns of species distribution. By intersecting precipitation and temperature data with spatially-referenced data on species observations stored in the GIS we determined the 'climatic envelope' of each species and constructed predictive maps which show the potential distribution of each species. Using cluster analysis, the bats were classified into three main biogeographic groups according to their distribution, namely desert, Mediterranean, and widespread in Israel. The potential distribution maps of all the species indicate that there are areas which have suitable bat habitats but from which bats have never been collected or observed. In the Mediterranean region of Israel, this is attributed to a large reduction in population size due to fumigation of caves, cave visitation and secondary poisoning.     

Effect of a Purified Initiation Factor F3 (B) on the Selection of Ribosomal Binding Sites on Phage MS2 RNA

STUDIES with T4 mRNA showed that initiation factor F2 (C) promotes the attachment of ribosomes to mRNA¹. On the 30S ribosomal subunit this effect is independent of the function of F2 in the binding of formylmethionyl tRNA², whereas formation of a 70S-mRNA complex depends on the binding of fMet-tRNA³. Template competition experiments⁴ showed that, with F2 (C), the ribosome seems to have the same affinity for synthetic polynucleotides as for natural mRNA. Addition of initiation factor F3 (B), however, leads to preferential binding of ribosomes to the natural mRNA. This suggests⁴ that while factor F2 (C) binds the ribosome to any site on the mRNA, the function of factor F3 (B) is to recognize some specific signal in natural mRNA corresponding, perhaps, to the beginning of a cistron. Fractionation of initiation factor F3 (B) into several species differing in their specificity for different mRNA templates⁵ gave further support to the hypothesis that this protein can select binding sites. An excellent system to demonstrate this effect of F3 (B) would be the binding of ribosomes to RNA from E. coli RNA bacteriophages, since Steitz⁶ has analysed and determined the nucleotide sequence of the three binding sites corresponding to the three cistrons of R17 mRNA. Experiments were thus undertaken to study the effect of a purified fraction of F3 (B) on the binding of ribosomes to the different sites of such a phage RNA.     

Translocation of 14C-Assimilates in Roses

Movement of ¹⁴C-assimilates from young and mature leaves to young rose shoots (Rosa hybrida cv. Marimba) was examined in two developmental stages. In the first stage after bud breaking the young shoot, especially its tip, depends for its supply of assimilates mainly on the mature foliage. At this stage young leaves are powerful sinks and retain 97% of their own photosynthates. The translocated 3% move mainly to the roots. At a later stage, just after the appearance of the flower bud, most of the leaves on the shoot become a source. The upper leaves supply assimilates to the flower bud and to the upper part of the stem. The ¹⁴C-assimilates from the lower leaves move in two directions, the larger part being directed downward.     

The winter fattening model: a test at low latitude using the Clamorous Reed Warbler

Small birds at high latitudes accumulate fat during the day so that they can survive long and cold winter nights. The winter fattening model suggests that birds increase their minimum (morning) mass in cold weather, build up their mass during the day, and then rely on the energy reserves so accumulated until the morning. While data from mid and high latitudes support this model, little is known about the strategies of birds inhabiting lower latitudes (< 40°N). We use an 18-year data set to investigate whether the winter fattening model holds in a mid-latitude (32°N) population of the Clamorous Reed Warbler Acrocephalus stentoreus . We show that morning mass and fat score vary as predicted by the winter fattening model. In addition, adults appear to be better adapted to long and cold winter nights than first-year birds. A long-term trend of increased body mass may be attributable to character release following reduced interspecific competition.     

The use of kairomones for foraging decisions by an aphid parasitoid in small host aggregations

1. The wasp Diaeretiella rapae uses honeydew emitted by its host, the cabbage aphid Brevicoryne brassica, as a kairomone (chemicals emitted by an organism as part of its activity and used by its natural enemies to their advantage). The role of the kairomone in foraging decisions by the parasitic wasp was explored by manipulating the amount of honeydew and the number of aphids in a colony independently. The count-down patch-exploitation mechanism (Iwasa et al., 1981) was employed to predict the results of these manipulations and contrast them with the predictions of Waage's (1979) model. 2. Kairomonal activity of honeydew decreased as the honeydew aged and lost its activity completely within 72 h. 3. The wasp was exposed to different amounts of honeydew on (a) aphid-free leaves and (b) leaves bearing colonies of 150 aphids. The parasitoid search time on both leaf types increased with increasing honeydew contamination. On aphid-bearing leaves, the number of attacked aphids in the colonies also increased with increasing honeydew contamination. The presence of aphids reduced the parasitoid search time compared to search time on aphid-bearing leaves with the same level of honeydew contamination, as predicted by the count-down model. 4. Parasitoids exposed to the same amount of honeydew, but a different number of aphids in a colony on the leaf, first increased the number of aphids attacked in relation to the number of aphids in the colony. But as the colony reached a certain size, the number of aphids attacked levelled off, despite the increase in the number of aphids in the colony. Search time was variable but did not exhibit any trend as the number of aphids in the colonies increased. 5. These results suggest that honeydew level is used by D. rapae as a cue for assessment of the number of aphids in the colony. In such cases, a count-down exploitation mechanism gives the best results to a forager. Many parasitoids may use kairomones for patch assessment and will therefore employ a count-down rule during patch exploitation.     

Fat, hydration condition, and moult of Steppe Buzzards Buteo buteo vulpinus on spring migration

Physical condition of migrating Steppe Buzzards Buteo buteo vulpinus was determined during spring migration at Elat, southern Israel, 1984–1988. An index based on measurements of body mass, wing-length and culmen was used to estimate fat content, based on fat extraction from nine buzzards. In addition, hydration condition was measured in 1988 and moult was checked in 1985–1988. More immatures (1001) than adults (459) were trapped, and a greater percentage of immatures (19.8%) than adults (8.4%) was retrapped during the same season. Adults had significantly greater fat reserves (4.5% of body mass) than immatures (3.8%). Most adults were in some stage of interrupted moult: however, active primary moult was noted only in immatures (10%). These findings suggest that different age groups use different migration strategies. Most of the buzzards trapped in this study could not have completed their entire migration using only stored fat: thus, hunting was probably necessary to replenish their energy reserves. No indication of water stress was found in the spring of 1988.