Tentoxin effects on infrastructure and greening of ivyleaf morningglory (Ipomoea hederacea var. hederacea) cotyledons

The effects of 20 μM tentoxin on mesophyll chloroplast ultra-structural development, chlorophyll organization and accumulation, and pigment transformations in cotyledons of dark-grown, 4-day-old ivyleaf morningglory [Ipomoea hederacea (L.) Jacq. var. hederacea]were monitored. After 6 h of white light (200 μEm^?2T.s^?1), many plastids of tentoxin-treated tissues contained prolamellar bodies or inconsistent internal membrane orientation in contrast to the uniform internal membrane orientation and absence of prolamellar bodies in controls. Grana stacking did not progress beyond three to four disc loculi in tentoxin-treatments, and fret membranes were usually discontinuous and reduced. Cylindrical or cupped grana appeared in many chloroplasts after 3 days of light, while other chloroplasts in which disruption was more pronounced had few grana except for remnants, but usually did possess vesicles or structures resembling prolamellar bodies. Tentoxin had no apparent effect on stroma density or plastoglobuli size and number. No starch grains appeared in any of the tentoxin treatments, whereas they appeared after 24 h in controls. Initial protochlorophyllide content and its photoconversion to chlorophyllide and subsequent Shibata shift were not affected by tentoxin. Chlorophyll accumulation rates in tentoxin-treated cotyledons were about 10% of control rates during the first 24 h of greening and about 20% of controls from 48 to 72 h of greening. Chlorophyll alb ratio and PSU size (total Chl/P700) were not significantly affected by tentoxin.     

Varietal variation in uptake and utilization of potassium (rubidium) in high-salt seedlings of barley

Seedlings of eleven varieties of barley (Hordeum vulgare L.) showed differences in utilization of K⁺ from a full nutrient solution containing 3.0 mM K⁺. The K⁺ content of both roots and shoots was proportional to the fresh weights and dry weights after a week in the nutrient solution. The K⁺ use-efficiency ratio, which indicates the efficiency of nutrient utilization (mg dry weight produced per mg K⁺ absorbed), differed significantly among the varieties. There was no correlation between influx of Rb⁺ and the content of K⁺. It is suggested that there are wide varietal differences in such genetically-determined properties as ion influx and efflux and net ion transport to the shoot. Further-more, the influx of Rb⁺ was closely linked to transpiration, probably due to a variety-specific non-metabolic part of Rb⁺ influx. Varietal differences in influx of Rb⁺ were more pronounced in high-K⁺ roots than in low-K⁺ roots with maximum rate of Rb⁺ uptake, but the rank of varieties was the same in each case. – Criteria for the selection of K⁺ use-efficient varieties of barley are discussed.     

The food of coral-reef Drupa (Gastropoda)

Eight species of the predatory gastropod Drupa are abundant in exposed habitats of Indo-Pacific coral reefs. The diets of seven species and two subspecies were investigated by gut content analysis of over 1400 specimens from a number of localities from the Red Sea to the western Pacific. Two species, D. grossularia and D. lobata , are sipunculan specialists, whilst D. morum and D. rubusidaeus mainly eat eunicid polychaetes . Drupa ricinus and probably D. elegans feed upon a wide variety of prey including crustacea, vermetid gastropods, chitons, polychaetes and sipunculans. The Red Sea subspecies D. ricinus hadari also eats small gobiid fish. Drupa clathrata clathrata, probably the least advanced species in the genus, has a diet of molluscs and barnacles, similar to that of other thaiid gastropods.     

Influence of sampling strategy on the relationships between fauna and vegetation structure,plant lifeform and floristics

The effect of sampling strategy on animal-habitat relationships was evaluated with data collected from a 50 ha area containing a sequence of tropical vegetation types. Sampling sites were located randomly within defined habitat types (i.e. stratified random sampling) and systematically irrespective of habitat type. At each site the fauna, comprising birds (63 species), reptiles (15 species), amphibia (13 species) and grasshoppers (32 species) were sampled for the abundance of species. Simultaneously, vegetation and related data, comprising vertical structure (52 attributes), ground surface condition (18 attributes), plant lifeform (18 attributes) and the abundance of plant species (200) were recorded. Random and systematic data matrices, comprising sites defined by animal or vegetation attributes, were reduced dimensionally by correspondence analysis. Animal first dimension vectors were then regressed on the first dimension vectors of vegetation structure, lifeform and floristics, respectively. With stratified random sampling, vegetation structure (comprising vertical and ground attributes) and lifeform explained most of the variation in the fauna; floristics were not a significant factor. On the other hand with the systematic data, fioristics explained almost all of the variation in animal abundance and distribution. By removing the ecotonal sites from the systematic data set and recalculating vectors, the animal—vegetation relationships became similar to those generated from the stratified random sampling data. Clearly, the sampling strategy employed in a faunal survey has a major influence on the inventory of species, and on the relative importance of vegetation structure, lifeform and floristics in explaining animal distribution. The presence of ecotones in the systematic data set was highlighted as the key to the difference between the sampling strategies.     

Chemical mediation of reciprocal mother–offspring recognition in the Southern Water Skink (Eulamprus heatwolei)

Abstract Kin recognition has been demonstrated to play an important role in the social structure of a wide range of animals. Most studies to date have examined parent–offspring recognition only in species that provide offspring with direct parental care, however, there are several advantages to parent–offspring recognition even in the absence of direct parental care. In this study we investigated reciprocal mother–offspring recognition in the Australian scincid lizard Eulamprus heatwolei, a species that does not show direct parental care. We examined whether neonates could discriminate between their mothers and unrelated females, and whether females could discriminate between their offspring and unrelated neonates, via chemical cues, using retreat site selection experiments. We conducted trials when neonates were 1 and 4 weeks old to investigate whether responses are maintained as neonates age. We found that both neonates and mothers could discriminate between related and unrelated individuals when neonates were 1 week old. Mothers were more likely to take refuge under tiles treated with the odours of their own offspring, while neonates spent less time in areas treated with the odours of unrelated females. At 4 weeks of age, mothers no longer exhibited discriminatory behaviour between their offspring and unrelated neonates, while neonates were more likely to associate with the odour of any female over the odourless control. We hypothesize that reciprocal mother–offspring recognition in E. heatwolei reduces interference competition between mothers and their offspring and also may be important in habitat selection and territory establishment.     

Population genetic structure in Atlantic and Pacific Ocean common murres (Uria aalge): natural replicate tests of post‐Pleistocene evolution

Understanding the factors that influence population differentiation in temperate taxa can be difficult because the signatures of both historic and contemporary demographics are often reflected in population genetic patterns. Fortunately, analyses based on coalescent theory can help untangle the relative influence of these historic and contemporary factors. Common murres (Uria aalge) are vagile seabirds that breed in the boreal and low arctic waters of the Northern Hemisphere. Previous analyses revealed that Atlantic and Pacific populations are genetically distinct; however, less is known about population genetic structure within ocean basins. We employed the mitochondrial control region, four microsatellite loci and four intron loci to investigate population genetic structure throughout the range of common murres. As in previous studies, we found that Atlantic and Pacific populations diverged during the Pleistocene and do not currently exchange migrants. Therefore, Atlantic and Pacific murre populations can be used as natural replicates to test mechanisms of population differentiation. While we found little population genetic structure within the Pacific, we detected significant east–west structuring among Atlantic colonies. The degree that population genetic structure reflected contemporary population demographics also differed between ocean basins. Specifically, while the low levels of population differentiation in the Pacific are at least partially due to high levels of contemporary gene flow, the east–west structuring of populations within the Atlantic appears to be the result of historic fragmentation of populations rather than restricted contemporary gene flow. The contrasting results in the Atlantic and Pacific Oceans highlight the necessity of carefully considering multilocus nonequilibrium population genetic approaches when reconstructing the demographic history of temperate Northern Hemisphere taxa.     

Postzygotic isolation between the two European subspecies of the house mouse: estimates from fertility patterns in wild and laboratory-bred hybrids

We assessed the fertility (reproductive success, litter size, testis weight, spermatocyte-to-spermatid ratio) of F₁s and backcrosses between different wild-derived outbred and inbred strains of two mouse subspecies, Mus musculus domesticus and M. m. musculus . A significant proportion of the F₁ females between the outbred crosses did not reproduce, suggesting that female infertility was present. As the spermatocyte-to-spermatid ratio was correlated with testis weight, the latter was used to attribute a sterile vs. fertile phenotype to all males. Segregation proportions in the backcrosses of F₁ females yielded 11 (inbred) to 17% (outbred) sterile males, suggesting the contribution of two to three major genetic factors to hybrid male sterility. Only one direction of cross between the inbred strains produced sterile F₁ males, indicating that one factor was borne by the musculus X-chromosome. No such differences were observed between reciprocal crosses in the outbred strains. The involvement of the X chromosome in male sterility thus could not be assessed, but its contribution appears likely given the limited introgression of X-linked markers through the hybrid zone between the subspecies. However, we observed no sterile phenotypes in wild males from the hybrid zone, although testis weight tended to decrease in the centre of the transect.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 379–393.