The development of activity ranges in juvenile Brown Boobies Sula leucogaster

The post‐fledging dependence period is extremely important because it allows young birds the opportunity to develop behavioural skills required for later life. We raised 12 hatchling Brown Boobies Sula leucogaster and attached a miniaturized GPS logger to each bird to examine how flight improves after fledging. The Boobies made daily trips and increased the maximum distance, total distance travelled each day, trip duration and flight speed. Young Boobies seemed to gradually acquire flight skills towards independence.     

Molecular phylogeography of the microturbellarian Monocelis lineata (Platyhelminthes: Proseriata) in the North‐East Atlantic

Monocelis lineata is a complex of cryptic species (three in the Mediterranean and one in the Atlantic) widespread in midlittoral habitats. Throughout the range, populations with or without an ocular pigmented shield are found. We investigated the genetic structure of the North‐East Atlantic populations with the aim of shedding light on their phylogeography and reconstructing possible patterns of recolonization after the Würmian glaciation. Fourteen samples were investigated using cytochrome c oxidase subunit I (COI) and 13 by inter‐simple sequence repeats (ISSRs). COI did not exhibit a clear pattern of decreased genetic diversity along a latitudinal gradient. Populations from Ferrol (Spain), Doolin (Ireland), and Helsingør (Denmark) showed a higher genetic variability, whereas a reduction in the number of haplotypes was found at the northernmost edge of the distribution and in northern Ireland and Scotland. Two genetically differentiated areas (southern Europe and south‐western Ireland versus northern Atlantic) were revealed by ISSR data. The results obtained provided evidence of three refugia (Iberian Peninsula, south‐western Ireland, and North Sea), and the occurrence of secondary contacts that shaped the genetic variability of some of the populations examined. Two different recolonization pathways of north‐western Europe during the post‐Würmian glaciations have been detected. Furthermore, ISSR analysis provided evidence of genetic divergence among populations with and without pigmented eyespot, suggesting the action of ecological differentiation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 117–135.     

IgG and IgM levels in dairy cows during the periparturient period

In dairy cows, the incidence of infectious diseases during the periparturient period is high. The most common diseases ante partum (a.p.) and post partum (p.p.) are mastitis and puerperal toxicaemia, puerperal septicaemia, and chronic endometritis, respectively. Studies suggest that this is related to an immunosuppressed status during this period.Therefore, the aim of this study was to determine the periparturient immune status characterized by concentrations of IgG and IgM in peripheral blood and colostrum samples of dairy cows and to assess in detail whether variations in immunoglobulin levels may be related to age and status of productivity. In addition, a possible correlation between the course of immunoglobulin levels and lymphocyte concentrations was assessed.Eighteen clinically healthy German Holstein and Red Holstein dams were selected for this study and sampled regularly between the 8^th week a.p. and the 4^th week p.p. IgG and IgM levels were determined using two novel competitive ELISAs.Results demonstrated a dramatic decrease of serum IgG and IgM levels beginning at the 8^th week and 4^th week a.p., respectively, both reaching trough at parturition. The IgG level recovered by the 4^th week p.p., while IgM concentrations remained low. The extent of IgG reduction seemed to be dependent on the initial IgG concentration when the cow was dried-off (8^th week a.p.). In contrast to IgM, the degree of IgG reduction correlated significantly with the IgG concentrations in the colostrum. Furthermore, a cross-correlation between the IgG levels and the lymphocyte counts was detectable (P < 0.01).In conclusion, the antepartal decline of blood IgG and IgM levels as well as the low periparturient IgG levels could reflect a “physiological phenomenon” of dairy cattle. If the phenomenon is associated with an unstable immune system, it must be assessed in future studies. Nonetheless, a sensitive immune system could explain the high incidence for infectious diseases during this period.     

Effects of precipitation on photosynthesis and water potential in Andropogon gerardii and Schizachyrium scoparium in a southern mixed grass prairie

In grassland ecosystems, spatial and temporal variability in precipitation is a key driver of species distributions and population dynamics. We experimentally manipulated precipitation to understand the physiological basis for differences in responses of species to water availability in a southern mixed grass prairie. We focused on the performance of two dominant C₄ grasses, Andropogon gerardii Vitman and Schizachyrium scoparium (Michx.) Nash, in treatments that received ambient rainfall, half of ambient rainfall (“drought” treatment), or approximately double ambient rainfall (“irrigated” treatment). Water potentials of S. scoparium were lower than A. gerardii, suggesting superior ability to adjust to water deficit in S. scoparium. Additionally, drought reduced photosynthesis to a greater extent in A. gerardii compared to S. scoparium. Leaf-level photosynthesis rates were similar in ambient and irrigated treatments, but were significantly lower in the drought treatment. Although stomatal conductance was reduced by drought, this was not limiting for photosynthesis. Leaf δ¹³C values were decreased by drought, caused by an increase in C_i/C_a. Chlorophyll fluorescence measures indicated light-harvesting rates were highest in irrigated treatments, and were lower in ambient and drought treatments. Moreover, drought resulted in a greater proportion of absorbed photon energy being lost via thermal pathways. Reductions in photosynthesis came as a result of non-stomatal limitations in the C₄ cycle. Our results provide mechanistic support for the hypothesis that S. scoparium is more drought tolerant than A. gerardii.     

Independence of genetic variation between circadian rhythm and development time in the seed beetle, Callosobruchus chinensis

A positive genetic correlation between periods of circadian rhythm and developmental time supports the hypothesis that circadian clocks are implicated in the timing of development. Empirical evidence for this genetic correlation in insects has been documented in two fly species. In contrast, here we show that there is no evidence of genetic correlation between circadian rhythm and development time in the adzuki bean beetle, Callosobruchus chinensis. This species has variation that is explained by a major gene in the expression and period length of circadian rhythm between strains. In this study, we found genetic variation in development time between the strains. The development time was not covaried with either the incidence or the period length of circadian rhythm among the strains. Crosses between strains suggest that development time is controlled by a polygene. In the F₂ individuals from the crosses, the circadian rhythm is attributable to allelic variation in the major gene. Across the F₂ individuals, development time was not correlated with either the expression or the period length of circadian rhythm. Thus, we found no effects of major genes responsible for variation in the circadian rhythm on development time in C. chinensis. Our findings collectively give no support to the hypothesis that the circadian clock is involved in the regulation of development time in this species.     

Night-interrupting light inhibits diapause induction in the Kanzawa spider mite, Tetranychus kanzawai Kishida (Acari: Tetranychidae)

The inhibitory effects of the timing, intensity (I_I) and period (I_T) of night-interrupting light on diapause induction of the Kanzawa spider mite (Tetranychus kanzawai) were investigated in a series of laboratory experiments. During a light and dark period of 8 and 16 h d⁻¹, respectively, a single 1-h night-interrupting light was applied at early (E), middle (M), and late (L) parts of the dark period: i.e., at 3, 7.5, and 12 h after the start of the dark period, respectively. No interrupting light was applied in the control treatment. The incidence of diapause was significantly lower in the M treatment (63%) compared to the control treatment (100%). In the E and L treatments, more than 90% of females entered diapause, which was comparable to the control treatment. Since the longest consecutive dark period during the E and L treatments was longer than the critical dark period (CDP) of 10.5-11 h d⁻¹, during which 50% of females entered diapause, the night-interrupting light probably failed to prevent diapause induction. However, in the M treatment, the longest consecutive dark period was shorter than the CDP; therefore, the night-interrupting light inhibited diapause induction. Moreover, the inhibitory effects of night-interrupting light in the M treatment increased as I_I and I_T increased. The dose of night-interrupting light (I_I × I_T) was significantly negatively related to the incidence of diapause. The median effective dose for 50% disturbance of diapause induction was 2.5 kJ m⁻² at wavelengths between 350 and 1050 nm. Our results suggest that the longest consecutive dark period and the dose of night-interrupting light should both be considered when a lighting-based physical control is applied to inhibit diapause induction and consequent overwintering of T. kanzawai in commercial agricultural fields.     

Effects of cold immobilization and recovery period on honeybee learning, memory, and responsiveness to sucrose

In addition to human error and variation in laboratory conditions, there are numerous factors that can complicate comparisons among studies. Furthermore, differences in how experimental methods are executed can make it difficult to distinguish between effects of focal versus extraneous variables. Insect neural function is commonly evaluated using Pavlovian conditioning techniques; learning and memory in many species can be assessed using the proboscis extension reflex (PER). However, there are significant inconsistencies in methods used to immobilize insects prior to PER tests. We compared responses of honeybees immobilized in a refrigerator, on ice, and in a freezer, and evaluated influence of recovery interval before testing. Ice-chilling weakly decreased learning (response to an originally neutral odor) more so than refrigeration or freezing, but not 24-h recall of odor. We found no significant differences in responsiveness to sucrose relative to cooling method, but responsiveness was significantly lower among honeybees left to recover for only 0.75 h versus 1.5 or 3 h. Finally, we observed increased responsiveness to sucrose and geraniol between June and August. Our results suggest that inconsistencies in cold immobilization methods could confound interpretation and comparison of results from a large body of work on honeybee learning and memory.     

Testing the effect of transient Plio‐Pleistocene barriers in monsoonal Australo‐Papua: did mangrove habitats maintain genetic connectivity in the Black Butcherbird?

Changes in climate and sea level are hypothesized to have promoted the diversification of biota in monsoonal Australia and New Guinea by causing repeated range disjunctions and restricting gene flow between isolated populations. Using a multilocus (one mtDNA locus, five nuclear introns) phylogeographic approach, we test whether populations of the mangrove and rainforest restricted Black Butcherbird (Cracticus quoyi) have diverged across several geographic barriers defined a priori for this region. Phylogeographic structure and estimates of divergence times revealed Plio-Pleistocene divergences and long-term restricted gene flow of populations on either side of four major geographic barriers between and within Australia and New Guinea. Overall, our data are consistent with the hypothesis that mesic-adapted species did not disperse across the open dry woodlands and grasslands that dominated the transient palaeo-landbridges during the Plio-Pleistocene despite the presence of mangrove forests that might have acted as dispersal corridors for mesic-adapted species. Our study offers one of the first multilocus perspectives on the impact of changes in climate and sea level on the population history of widespread species with disjunct ranges in Australia and New Guinea.     

Low but structured chloroplast diversity in Atherosperma moschatum (Atherospermataceae) suggests bottlenecks in response to the Pleistocene glacials

Background and Aims

The cool temperate rainforests of Australia were much reduced in range during the cold and dry glacial periods, although genetic evidence indicates that two key rainforest species, Nothofagus cunninghamii and Tasmannia lanceolata, survived within multiple locations and underwent only local range expansions at the end of the Last Glacial. To better understand the glacial response of a co-occurring but wind-dispersed and less cold-tolerant rainforest tree species, Atherosperma moschatum, a chloroplast phylogeographic study was undertaken.

Methods

A total of 3294 bp of chloroplast DNA sequence was obtained for 155 samples collected from across the species'' range.

Key Results

The distribution of six haplotypes observed in A. moschatum was geographically structured with an inferred ancestral haplotype restricted to Tasmania, while three non-overlapping and endemic haplotypes were found on the mainland of south-eastern Australia. Last glacial refugia for A. moschatum are likely to have occurred in at least one location in western Tasmania and in Victoria and within at least two locations in the Great Dividing Range of New South Wales. Nucleotide diversity of A. moschatum was lower (π = 0·00021) than either N. cunninghamii (0·00101) or T. lanceolata (0·00073), and was amongst the lowest recorded for any tree species.

Conclusions

This study provides evidence for past bottlenecks having impacted the chloroplast diversity of A. moschatum as a result of the species narrower climatic niche during glacials. This hypothesis is supported by the star-like haplotype network and similar estimated rates of chloroplast DNA substitution for A. moschatum and the two more cold tolerant and co-occurring species that have higher chloroplast diversity, N. cunninghamii and T. lanceolata.     

Infectivity-associated PrPSc and disease duration-associated PrPSc of mouse BSE prions

ABSTRACT

Disease-related prion protein (PrP^Sc), which is a structural isoform of the host-encoded cellular prion protein, is thought to be a causative agent of transmissible spongiform encephalopathies. However, the specific role of PrP^Sc in prion pathogenesis and its relationship to infectivity remain controversial. A time-course study of prion-affected mice was conducted, which showed that the prion infectivity was not simply proportional to the amount of PrP^Sc in the brain. Centrifugation (20,000 ×g) of the brain homogenate showed that most of the PrP^Sc was precipitated into the pellet, and the supernatant contained only a slight amount of PrP^Sc. Interestingly, mice inoculated with the obtained supernatant showed incubation periods that were approximately 15 d longer than those of mice inoculated with the crude homogenate even though both inocula contained almost the same infectivity. Our results suggest that a small population of fine PrP^Sc may be responsible for prion infectivity and that large, aggregated PrP^Sc may contribute to determining prion disease duration.