Morphological diversification has led to inter-specific variation in elastic wing deformation during flight in scarab beetles.

Insect wing shapes and the internal wing-vein arrangement are remarkably diverse. Although the wings lack intrinsic musculature to adjust shape actively, they elastically deform due to aerodynamic and inertial loads during flapping. In turn, the deformations alter the shape of the wing profile affecting the aerodynamic force. To determine how changes in wing-vein arrangement affect elastic wing deformation during free flight, we compared elastic wing deformations between free-flying rose chafers (Protaetia cuprea) and dung beetles (Scarabaeus puncticollis), complementing the comparison with wing static bending measurements. The broader relevance of the results to scarab beetle divergence was examined in a geometric morphometric (GM) analysis of wing-vein arrangement in 20 species differing in phylogeny and ecology. Despite rose chafers and dung beetles demonstrating similar flapping kinematics and wing size, the rose chafer wings undergo greater elastic deformation during flapping. GM analyses corrected for phylogenetic relatedness revealed that the two beetles represent extremes in wing morphology among the scarab subfamilies. Most of the differences occur at the distal leading edge and the proximal trailing edge of the wing, diversifying the flexibility of these regions, thereby changing the pattern of elastic wing deformation during flapping. Changes to local wing compliance seem to be associated with the diversification of scarab beetles to different food sources, perhaps as an adaptation to meet the demands of diverse flight styles.

Light pulses administered during the circadian dark phase alter expression of cell cycle associated transcripts in mouse brain.

The circadian mode of cell division has been known for more than a century, but the association between circadian rhythms and mitosis is not yet clear. Synchronization of circadian oscillators with the outside world is achieved because light, or other external temporal cues, have acute effects on the levels of the clock's molecular components. Thus, an important question is whether environmental signals also affect transcription levels of cell machinery genes in a similar manner? In a microarray analysis, we have tested the influence of light pulses on the expression of transcripts in the mouse brain. Light pulses consistently affect transcription levels of genes that are essential and directly control the cell cycle mechanism, as well as levels of genes that are associated with the various cell cycle checkpoints. The changes in the levels and the direction of these changes could possibly lead to cell cycle arrest. We also found consistent changes in transcription levels of genes that are associated with tumorigenesis and are directly implicated with enhanced proliferation and metastasis.

6-Sulphatoxymelatonin secretion in different locomotor activity types of the blind mole rat Spalax ehrenbergi.

6-Sulphatoxymelatonin (aMT6S) excretion was examined in the urine of rhythmic and arrhythmic blind subterranean mole rats (Spalax ehrenbergi) to test the correlation between melatonin secretion (as represented by aMT6S) and variability in circadian locomotor activity. Activity pattern was tested in four males, first for a week under short photoperiod [light:dark (LD) 10:14], followed by 10 days in constant darkness (DD). After several months the experiment was repeated under long photoperiod (LD 14:10), followed by DD conditions. Under LD conditions all animals exhibited aMT6S excretion during the dark phase, with a decline just before the onset of light. No correlation was found between activity pattern and melatonin secretion. The animal with the highest melatonin secretion both under LD and DD had an arrhythmic locomotor pattern. The results suggest that in mole rats melatonin secretion and circadian locomotor activity are controlled by two different mechanisms. There were large differences in the aMT6S levels among individuals, suggesting the importance of duration of melatonin secretion over amplitude for gonadal development and thermoregulatory changes. During summer, i.e., before the breeding season, the animals keep a more stable aMT6S secretion than in winter, and the amplitude of secretion is higher under DD vs. LD conditions.

Circadian rhythm and the per ACNGGN repeat in the mole rat, Spalax ehrenbergi.

Individual variability in circadian locomotor activity has recently discovered in the blind mole rat, Spalax ehrenbergi. An interesting association was found between different circadian types and two DNA fragments, 5.6 and 5.9 kb long, that contain the ACNGGN repeat sequence, homologous to a part of the period gene of Drosophila. Nine of 12 arrythmic animals showed the 5.6-kb band, while 13 of 17 circadian rhythmic animals had the 5.9-kb band. This repeat exists also in the brain RNA of the mole rat, apparently in higher quantities during the sleeping phase, suggesting that an unusual protein(s), composed of a poly-Thr-Gly segment, affects in circadian rhythm.

Activity pattern and rhythm in the subterranean mole rat superspecies Spalax ehrenbergi.

Good candidates for naturally occurring variability in circadian rhythms may be subterranean herbivores, since they are not normally subjected to entraining light stimulation. To test this possibility, we selected the blind mole rat Spalax ehrenbergi superspecies in Israel and tested it in short- and long-term experiments. Short-term experiments showed that the animals exhibited three patterns of activity: a regular circadian rhythm (26.6%), an altered circadian rhythm (shorter or longer than normal, 53.1%), and an arrhythmic pattern (20.3%). A long-term experiment showed that the arrhythmic pattern indeed reflected a genuine arrhythmic genotype. The mole rats were found to be active less than 25% of the day and exhibited a multiphasic mode of activity, both diurnally and nocturnally. The number of activity periods and the level of activity were negatively correlated: Animals that exhibited a high level of activity per unit of time showed low numbers of activity periods, while animals that exhibited a lower level of activity showed higher numbers.

Period-homologous sequence polymorphisms in subterranean mammals of the Spalax ehrenbergi superspecies in Israel.

Restriction fragment length polymorphism (RFLPs) of the mouse period-homologous sequence were studied in 13 populations of the four chromosomal species (2n = 52, 54, 58 and 60) of the mole rat, Spalax ehrenbergi superspecies in Israel. The period locus of Drosophila melanogaster is implicated in controlling the circadian rhythm as well as the male courtship song rhythm. Multiple DNA homologies exist in the mole rat and correspond to more than 10 loci. The level of polymorphism is very high, with a large number of alleles per locus, increasing from the northern to the southern species along a gradient of increasing aridity. Variation was also found in an isolated desert population, with a unique fragment specific to this population. Fragment variation allows distinction between chromosomal species, and confirms earlier evidence that gene flow does not occur between them. A correlation was found between some allelic fragments and the number of apparent harmonics of the courtship calls. This finding suggests an interesting testable hypothesis that the existence of a locus (homology) is responsible for the courtship call parameters.

Haptoglobin DNA polymorphism in subterranean mole rats of the Spalax ehrenbergi superspecies in Israel.

We analyzed the genetic diversity and environmental correlates of the haptoglobin (Hp) gene by RFLP analysis of 121 subterranean mole rats, comprising 13 populations belonging to the 4 chromosomal species (2n = 52, 54, 58 and 60) of the actively speciating Spalax ehrenbergi superspecies in Israel. The following results were indicated: (i) Out of the six restriction enzymes we tested, we found polymorphism only in TaqI, with three allelic fragments, and described their geographic patterning. (ii) Genetic diversity of Hp was highest in the centre of the range. (iii) The two major alleles showed high significant and opposite correlation with humidity. (iv) Genetic differentiation analysis indicated that 40 per cent of the Hp variation was within, and 60 per cent between populations. We conclude that climatic selection plays an important role in haptoglobin genetic differentiation.

Mhc class II DNA polymorphisms within and between chromosomal species of the Spalax ehrenbergi superspecies in Israel.

Restriction fragment length polymorphisms (RFLPs) of two major histocompatibility class II genes (P alpha 1 and Q beta) were studied in 13 populations of four chromosomal species (2n = 52, 54, 58 and 60) of the mole rat, Spalax ehrenbergi superspecies in Israel. A substantial frequency of allelic fragments was found in both genes for all populations, including a desert isolate. In the P alpha 1 gene, one allelic fragment is a result of a deletion mutation which is diagnostic of the 2n = 52 chromosomal species. All other ten allelic variants are the result of point mutations. All mutations are located in a short region flanking the 3' end of the gene. Based on Mhc polymorphisms we confirm earlier evidence that gene flow does not occur between the older chromosomal species (2n = 52, 54, 58), and that reproductive isolation decreases, progressively from the oldest to the youngest species (2n = 60).

Mercury selection of allozymes in marine organisms: Prediction and verification in nature.

The geographic distributions of mercury-tolerant allozyme genotypes of the enzyme phosphoglucomutase in the shrimp Palaemon elegans and the enzyme phosphoglucose isomerase in the marine gastropod Monodonta turbinata were compared in a mercury-polluted site versus several unpolluted sites on the Israeli coast of the Mediterranean sea. We conclude that in both phosphoglucomutase and phosphoglucose isomerase, the level of the mercury-tolerant allozyme genotypes was higher in the polluted as compared with the unpolluted sites. These results suggest that mercury selection is operating in nature on allozyme genotypes of these marine organisms along patterns comparable with those found previously in laboratory experiments. We suggest that the enzymes studied here display an adaptive pattern in polluted environments. Therefore, they may be used as potential indicators and monitors of marine pollution.

Selection of allelic isozyme polymorphisms in marine organisms: pattern, theory, and application.

The evolutionary significance of allelic isozyme polymorphisms in several Mediterranean marine organisms was tested initially by post-hoc gene frequency analyses at 11-15 gene loci in natural populations of barnacles, Balanus amphitrite, under thermal [Nevo et al, 1977] and chemical [Nevo et al, 1978] pollutions. We next carried out pre-hoc controlled laboratory experiments to test the effects of heavy metal pollution (Hg, Zn, Cd) on genotypic frequencies of 15 phosphoglucomutase (PGM) genotypes in thousands of individuals of the shrimp Palaemon elegans [Nevo et al, 1980, 1981a, and the present study]. Similarly, we tested the effects of Hg, Zn, Cd, Pb, Cu pollutions on the genotypic and allelic frequencies of five phosphoglucose isomerase (PGI) genotypes in the two close species of marine gastropods, Monodonta turbinata and M turbiformis [Lavie and Nevo, 1982, and the present study]. In both the thermal and chemical pollution studies, we established in repeated experiments statistically significant differences of allele frequencies at 8 out of 11 (73%) and 10 out of 15 (67%) gene loci, respectively, between the contrasting environments in each. While no specific function could be singled out in the post-hoc chemical study due to the complex nature of polluted marine water, temperature could be specified as the primary selective agent in the thermal study. The strongest direct and specific evidence for significant differential survivorship among allelic isozyme genotypes was obtained in the pre-hoc studies in Palaemon and Monodonta. Their differential viability was probably associated with the different degree of heavy metal inhibition uniquely related to each specific pollutant. Furthermore, we demonstrated in the two closely related Monodonta species parallel genotypic differentiation as a response to pollution. Our results are inconsistent with the neutral theory of allelic isozyme polymorphisms and appear to reflect the adaptive nature of the allelic isozyme polymorphisms studied. Allelic isozyme genotypes are sensitive to and vary with the quality and quantity of specific pollutants. Therefore, they can provide precise genetic indicators of the effects of pollution on the short- and long-term genetic changes of populations. Ideally, in different marine species specific genetic loci, either singly or in combination, may prove sensitive markers to different pollutants and could easily be assayed by quick electrophoretic tests and be used as genetic monitors. An extensive search for the appropriate enzymatic systems in various relatively sedentary marine species exposed to pollutants is therefore urgent.