Female Preferences for Sailfin and Body Size in the Sailfin Molly, Poecilia latipinna

We tested the mating preference of female sailfin mollies (Poecilia latipinna) by presenting them with pairs of dummy males differing in: (I) sailfin and body size together (holding sailfin : body size ratio constant); (II) body size alone (holding sailfin size constant); (III) sailfin size alone (holding body size constant); and (IV) sailfin : body size ratio (holding total lateral projection area constant). Females spent more time near dummies of greater sailfin or greater body size. The preference functions based on the first three sets of stimuli showed a similar pattern: the preference between any two simultaneously presented dummies increased with the magnitude of the discrepancy in lateral projection area (LPA) between them. However, when LPA was held constant in expt (IV), neither body size, sailfin size, nor any particular dummy (i.e. any particular sailfin + body size combination) was preferred. These findings suggest that increased LPA is more stimulating to sexually receptive females and that females consequently prefer larger males. The sailfin may therefore have evolved as a way for males to exploit this sensory bias and appear larger to prospective mates.     

Flies evolved small bodies and cells at high or fluctuating temperatures

Recent theory predicts that the sizes of cells will evolve according to fluctuations in body temperature. Smaller cells speed metabolism during periods of warming but require more energy to maintain and repair. To evaluate this theory, we studied the evolution of cell size in populations of Drosophila melanogaster held at either a constant temperature (16°C or 25°C) or fluctuating temperatures (16 and 25°C). Populations that evolved at fluctuating temperatures or a constant 25°C developed smaller thoraxes, wings, and cells than did flies exposed to a constant 16°C. The cells of flies from fluctuating environments were intermediate in size to those of flies from constant environments. Most genetic variation in cell size was independent of variation in wing size, suggesting that cell size was a target of selection. These evolutionary patterns accord with patterns of developmental plasticity documented previously. Future studies should focus on the mechanisms that underlie the selective advantage of small cells at high or fluctuating temperatures.     

Female bias for enlarged male body and dorsal fins in Xiphophorus variatus

Female preference for male fin elaborations in Poeciliid fishes may be driven by a sensory bias for increased lateral projection area (LPA) that has existed since the lineages diverged from a common ancestor. Previous research supports this hypothesis demonstrating female Poecilia latipinna, Poecilia mexicana, and Poecilia reticulata prefer males of larger body and dorsal fin size, but exhibit no such preferences when controlling for total LPA. In the current study, we further tested this hypothesis by presenting female platys, Xiphophorus variatus, with pairs of dummy males differing in: (1) body size (holding dorsal fin size constant); (2) dorsal fin size (holding body size constant); and (3) dorsal fin: body size ratio (holding total LPA constant). Females spent more time near dummies of greater body and dorsal fin size; however, in the third experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These results provide additional support for the LPA and sensory bias hypotheses, demonstrating that female X. variatus not only prefer males with “swords”, but sailfin-like dorsal fins as well when body size is held constant. Shared preference for increased LPA is consistent with common ancestry of the sensory/neural systems in females of all four species.     

Analysis of protein adsorption characteristics to nano-pore silica particles by using confocal laser scanning microscopy

The effect of average pore size of nano-pore silica particles on protein adsorption characteristics was determined experimentally by the dissociation constant and the adsorption capacity determined from the Langmuir equation. As the average pore size was increased from 2.2 to 45 nm, the BSA adsorption capacity increased from 16.8 to 84.3 mg/g-silica so as the equilibrium constant (from 2.6 to 9.4 mg/ml). Using confocal microscopy with fluorescence labeling, we could visualize the protein adsorption in situ and determine the minimum pore size required for efficient intraparticle adsorption. The confocal microscopy analysis revealed that BSA was adsorbed mainly on the surface of the particles with a smaller pore size, but diffused further into the interstitial surface when it was sufficiently large. It was concluded that for BSA whose Stoke's diameter is ca. 3.55 nm the minimum pore size of about 45 nm or larger was required for a sufficient adsorption capacity.     

Separating the impact of group size, density, and enclosure size on broiler movement and space use at a decreasing perimeter to area ratio

The goal of this study was to determine the impact of enclosure size on space use and movement patterns of domestic fowl (Gallus gallus domesticus), independent of group size and density. Research designed to estimate the effects of group size, density, or enclosure size involves inherent confounding between factors, clouding their individual effects. This experimental design enabled us to conduct multiple contrasts in order to tease apart the specific impacts. Treatments consisted of five combinations of three square enclosures: small (S; 1.5 m²), medium (M; 3.0 m²), and large (L; 4.5 m²), and three group sizes of 10, 20, and 30 birds. We made comparisons while holding group size constant, holding density constant, and the third while maintaining a constant enclosure size. Nearest neighbor distances increased with enclosure size but appeared to be constrained by density. Net displacement and minimum convex polygons increased with enclosure size regardless of group size or density. We found no evidence of social restriction on space use. Results indicate that broilers adapted their use of space and movement patterns to the size of the enclosures, spreading out and utilizing a greater amount of space when it was available.     

Female Preference for Male Lateral Projection Area in the Shortfin Molly, Poecilia mexicana: Evidence for a Pre-existing Bias in Sexual Selection

Sailfin molly (Poecilia latipinna) males possess a large dorsal fin (sailfin) and perform an elaborate courtship display. Females prefer to associate and mate with males of greater body and sailfin size. Evidence supports a single origin for the sailfin species complex from a shortfin ancestor. Unlike sailfin species, males of the shortfin species complex are sexually monomorphic in fin size and exhibit little or no courtship behavior. In this study, we tested the pre‐existing bias and lateral projection area (LPA) hypotheses for sexual selection by examining female mating preferences in the shortfin molly, P. mexicana. Specifically, we presented females with pairs of dummy males differing in: (1) dorsal fin and body size together (holding fin:body size ratio constant); (2) body size (holding dorsal fin size constant); (3) dorsal fin size (holding body size constant); and dorsal fin:body size ratio (holding total LPA constant). Females spent more time near dummies of greater body and dorsal fin size. The preference functions based on the first three sets of stimuli showed a similar pattern: the greater the LPA difference between paired dummies, the stronger the preference for the larger of the two. However, in the fourth experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These findings support the LPA hypothesis suggesting that increased LPA is more stimulating to sexually receptive females and that females consequently prefer larger males. Moreover, these data are consistent with results obtained in an identical series of experiments conducted on P. latipinna. The preference for increased male dorsal fin size/LPA by both female P. latipinna and P. mexicana supports the pre‐existing bias hypothesis. Thus, a bias for increased male LPA and consequent selection for enlarged dorsal fins may have preceded the appearance of the sailfin trait within the Molliensia lineage.     

Ice Recrystallization Behavior of Corn Starch/Sucrose Solutions: Effects of Addition of Corn Starch and Antifreeze Protein III

Knowledge of the behavior of corn starch during frozen storage is necessary to understand more complex systems. In the present study, ice recrystallization in corn starch (0.3% and 3%, w/w)/sucrose (40%, w/w) solution was investigated at −10 °C based on the theory of Ostwald ripening. The addition of corn starch to the sucrose solution increased the ice recrystallization (IR) rate constant. To explore the mechanism causing higher IR rate constant, fluorescence microscopy was used to analyze the distribution of corn starch molecules. Fluorescence micrograph showed corn starch distributed homogenously in the freeze-concentrated phase. Ice crystal size distribution assessment showed that at the same average radius, the addition of corn starch increased the standard deviation of ice crystal size distribution. The findings revealed that the addition of corn starch widened the distribution of ice crystal size, which may be the mechanism causing higher IR rate constant. To inhibit the ice recrystallization process, antifreeze protein type III (AFP III) was added to sucrose solutions with and without corn starch. In the presence of corn starch, 0.01-mg/mL AFP III was enough to significantly reduce the IR rate. Conversely, the samples without corn starch did not show a significant reduction in IR rate constant at the same AFP III concentration. The outcomes revealed that corn starch enhanced the activity of AFP III. The results of this study showed that corn starch increased the IR rate constant, and AFP III supplemented with corn starch was synergistically more efficient in retarding IR rate constant.

     

Interstitial albumin concentration measured during growth of perivascular cuffs in liquid-filled rabbit lung.

The growth rate and albumin concentration of interstitial fluid cuffs were measured in isolated rabbit lungs inflated with albumin solution (3 g/dl) to constant airway (Paw) and vascular pressures for up to 10 h. Cuff size was measured from images of frozen lung sections, and cuff albumin concentration (Cc) was measured from the fluorescence of Evans blue labeled albumin that entered the cuffs from the alveolar space. At 5-cmH2O Paw, cuff size peaked at 1 h and then decreased by 75% in 2 h. The decreased cuff size was consistent with an osmotic absorption into the albumin solution that filled the vascular and alveolar spaces. At 15-cmH2O Paw, cuff size peaked at 0.25 h and then remained constant. Cc rose continuously at both pressures, but was greater at the higher pressure. The increasing Cc with a constant cuff size was modeled as diffusion through epithelial pores. Initial Cc-to-airway albumin concentration ratio was 0.1 at 5-cmH2O Paw and increased to 0.3 at 15 cmH2O, a behavior that indicated an increased permeability with lung inflation. Estimated epithelial reflection coefficient was 0.9 and 0.7, and equivalent epithelial pore radii were 4.5 and 6.1 nm at 5- and 15-cmH2O Paw, respectively. The initial cuff growth occurred against an albumin colloid osmotic pressure gradient because a high interstitial resistance reduced the overall epithelial-interstitial reflection coefficient to the low value of the interstitium.     

Effects of sucrose on betacyanin accumulation and growth in suspension cultures of Phytolacca americana

The effects of sucrose on betacyanin accumulation and growth in suspension cultures of Phytolacca americana L. were investigated. Maximal betacyanin accumulation was observed at 88 m M sucrose on cell number basis and at 175 m M sucrose on fresh weight basis. This is because cell size decreased as the initial sucrose concentration was increased. Supplementary studies using mannitol indicated that sucrose itself caused increased cell number and that cell size was affected by both sucrose concentration and water potential. Betacyanin accumulation per cell and per fresh weight at a constant concentration of sucrose (88 m M ) decreased with decreasing water potential. When sucrose concentration increased at a constant water potential (–0.7 MPa), betacyanin accumulation per fresh weight increased up to 88 m M and remained at constant level at higher concentrations, while betacyanin accumulation per cell decreased remarkably, due to a dramatic increase in cell number.     

Plant growth-form alters the relationship between foliar morphology and species shade-tolerance ranking in temperate woody taxa

Variation in leaf size (area per leaf) and leaf dry weight per area (LWA) in relation to species shade- and drought-tolerance, characterised by Ellenberg's light (ELD) and water demand (EWD) values, respectively, were examined in 60 temperate woody taxa at constant relative irradiance. LWA was independent of plant size, but leaf size increased with total plant height at constant ELD. Canopy position also affected leaf morphology: leaves from the upper crown third had higher LWA and were larger than leaves from the lower third. Leaf size and LWA were negatively correlated, and leaf size decreased and LWA increased with decreasing species shade-tolerance. Mean LWA was similar for trees and shrubs, but trees had larger leaves than shrubs. Furthermore, all relationships were altered by plant growth-form: none of the qualitative tendencies was significant for trees. This implies the considerably lower plasticity of foliar parameters in trees than those in shrubs. Accordingly, shade-tolerance of trees, having relatively constant leaf structure, may be most affected by the variability in biomass partitioning and crown geometry which influence foliage distribution and spacing and finally determine canopy light absorptance. Alteration of leaf form and investment pattern for construction of unit foliar surface area which change the efficiency of light interception per unit biomass investment in leaves, is a competitive strategy inherent to shrubs. EWD as well as wood anatomy did not control LWA and leaf size, though there was a trend of ring-porous tree species to be more shade-tolerant than diffuse-porous trees. Since ring-porous species are more vulnerable to cavitation than diffuse-porous species, they may be constrained to environments where irradiances and consequently evaporative demand is lower.     

Resource-mediated demographic variation during the midsummer succession of a cladoceran community

SUMMARY. 1. The midsummer succession of cladoceran zooplankton in Lake Texoma was examined by demographic characterization of lake populations and a parallel set of life table experiments in which the dominant cladoceran species were raised on naturally occurring lake phytoplankton at lake temperatures. Diaphanosoma leuchtenbergianum occurred throughout the study period (mid June-mid August 1981) but Daphnia parvula, D. galeata mendotae and Ceriodaphnia lacustris were rarely detected after 15 July.
2. Analyses of size structure and size-specific fecundity of the cladoceran populations showed that (1) size structure shifted to smaller individuals in mid July, (2) size-specific fecundity was relatively constant in the smaller size classes and was constant or declined in larger females of each species, and (3) size at maturation did not vary significantly during the study of any population.
3. Individual growth rates of the two Daphnia species and Ceriodaphnia in the life table experiments were significantly lower in mid July when populations were declining and when size structure of each population was more dominated by smaller Individuals. The reduction in individual growth rates was short-lived in the life table experiments; growth rates returned to pre-decline levels by the end of July.
4. Two effects of temporary reductions in individual growth rates when size-specific fecundity and size at maturation are constant are (1) that size structure is temporarily shifted to smaller individuals, and (2) the potential rate of population growth is reduced because of delays in reproduction. Because data on size structure and size-specific fecundity are commonly used to evaluate the relative effects of predators and resource changes on populations it is noteworthy that erroneous conclusions about the mechanism of population decline may be reached when individual growth rates vary.     

Experimental measurement of particle size distribution and voidage in an expanded bed adsorption system

This paper presents an experimental analysis of matrix bead size distribution and voidage variations with axial height in an expanded bed adsorption system. Use of a specially constructed expanded bed with side ports has enabled sampling from within the expanded bed along the vertical axis. Particles removed from within the bed were measured for their size distributions. Residence time distribution studies were used to estimate bed voidage. Measurements of axial and radial particle size distributions and axial voidage distribution have been made at different flow rates. Particle size was found to be radially constant, indicating constant stratification in the column. The particle size was found to decrease with increasing axial height. Voidage increased with axial height from a settled bed value of 0.39 to approaching unity for high liquid velocities and increased at a constant axial position with increased flowrate. This information provides key insight into bed stability and data for the improved modeling of this important unit operation.     

Pattern stimulation and action potential of frog skin (author's transl)]

Experiments were carried out to investigate the relationship between the pattern of stimulus of efferent or afferent nerve and the size of action potential of frog's skin. Two kinds of preparations were used: the excised nerve skin preparation and the spinal preparation. In the range of moderate intervals of stimuli, the size of skin action potential of the nerve-skin preparation became larger with the increase of number of stimuli, (i) during a definite period of stimulation with various frequencies, or (ii) during various long periods of stimulation with constant frequency. The size of potential depended not only on number of stimuli but also on their interval. The latter property may be called pattern-sensitive. In some state of preparation the size of potential evoked by a constant number of stimuli was nearly constant, being independent from stimulus frequencies, that is, pattern insensitive. Both kinds of results were obtained in cases of the spinal preparation. Michaelis-Menten's equation could be applied to describe the relation between the size of potential and the number of stimuli. However, there was no reason to interprete this relation with a simple concentration-effect relationship. Another hypothesis was then testoned on the supposition that the response is composed of sequentially superposed unitary processes each of which was promptly evoked by each stimulus and decayed exponentially. The calculated response curve reasonably fit with the observed data. Slower processes commonly called accomodation were excluded from the present discussion and only the effect of relatively short period of stimulation was examined.     

Inferences about human demography based on multilocus analyses of noncoding sequences

Data from 10 unlinked autosomal noncoding regions, resequenced in 15 individuals from each of three populations, were used in a multilocus analysis to test models of human demography. Each of the 10 regions consisted of approximately 2500 bp. The multilocus analysis, based on summary statistics (average and variance of Tajima's D and Fu and Li's D*), was used to test a family of models with recent population expansion. The African sample (Hausa of Cameroon) is compatible with a constant population size model and a range of models with recent expansion. For this population sample, we estimated confidence sets that showed the limited range of parameter values compatible with growth. For an exponential growth rate as low as 1 x 10(-3)/generation, population growth is unlikely to have started prior to 50,000 years ago. For higher growth rates, the onset of growth must be more recent. On the basis of the average value of Tajima's D, our sample from an Italian population was found to be incompatible with a constant population size model or any simple expansion model. In the Chinese sample, the variance of Tajima's D was too large to be compatible with the constant population size model or any simple expansion model.     

Factors affecting the proportion of sterile soldiers in growing aphid colonies

The proportion of sterile soldiers in an aphid colony is positively correlated with colony size. Assuming logistic growth of the aphid colony, Aoki and Kurosu (Insect Soc 50:256–261, 2003) presented an inequality that determines, for any colony size, whether a soldier or a reproductive will be added to the colony. To put it in words, if the marginal defensive efficacy of a soldier, multiplied by the number of reproductives, is larger than the mean productivity of reproductives without defense by that soldier, the soldier will be produced; if not, a reproductive will be produced. Based on Aoki and Kurosus inequality, we carried out simulations to determine whether the proportion of soldiers increased with colony size. Given a constant level of depredation per aphid and a constant number of predators, proportion of soldiers continued to increase with colony size unless a single soldier was very effective or unless carrying capacity was very large. Given a constant number of nongluttonous predators and a decreasing level of depredation per aphid, proportion of soldiers soon began to decrease after a peak. However, given an increasing number of nongluttonous predators to keep a constant level of depredation per aphid, proportion of soldiers again continued to increase. These results confirmed the argument that the proportion of soldiers can increase with colony size under a wide range of realistic assumptions.     

Statistical model of variable allometric growth: otolith growth in Micropogonias furnieri(Actinopterygii, Sciaenidae)

The main objective of this study was to develop a statistical model for accurate estimates of relative growth. The method was based on identifying patterns of the residuals obtained from the Huxley's allometric equation. Three different approaches were applied: (1) growth with variable proportionality and constant allometry coefficient, (2) growth with constant proportionality and variable allometry coefficient and (3) distinct growth phases in which proportionality and allometry coefficients remained constant. The proposed statistical models were applied to the relationship of the otolith size and fish size of whitemouth croaker Micropogonias furnieri . The best fit was obtained when using approach (3). A change in the growth parameters was associated with the attainment of sexual maturity.     

Genetic Diversity in RNA Virus Quasispecies Is Controlled by Host-Virus Interactions

Many RNA viruses have genetically diverse populations known as quasispecies. Important biological characteristics may be related to the levels of diversity in the quasispecies (quasispecies cloud size), including adaptability and host range. Previous work using Tobacco mosaic virus and Cucumber mosaic virus indicated that evolutionarily related viruses have very different levels of diversity in a common host. The quasispecies cloud size for these viruses remained constant throughout serial passages. Inoculation of these viruses on a number of hosts demonstrated that quasispecies cloud size is not constant for these viruses but appears to be dependent on the host. The quasispecies cloud size remained constant as long as the viruses were maintained on a given host. Shifting the virus between hosts resulted in a change in cloud size to levels associated with the new host. Quasispecies cloud size for these viruses is related to host-virus interactions, and understanding these interactions may facilitate the prediction and prevention of emerging viral diseases.     

Maturity, mating and age-specific reproductive effort of the snake Natrix maura

The ecology of reproduction was studied in the snake Natrix maura. The presence of sperm in cloacal fluid was used to show the size at maturity, the season of mating and, together with information on the persistence of sperm in cloacal fluid of females after mating, the frequency of mating. These results suggest that each female mated several times per year. Female N. maura grew substantially after maturity, and clutch size increased with body size. Current and expected future reproduction increased in parallel during the period of growth after maturity; subsequently they were constant. This pattern would be expected to lead to a constant proportional allocation of energy to current reproduction. Reproductive effort (eggs/body energy) was independent of age as measured by growth rings. There was some evidence that not all stored energy was used in reproduction in the current season even when some follicles regressed.     

Size and fecundity variation in populations of Poecilia vivipara Block & Schneider (Teleostei; Poeciliidae) inhabiting an environmental gradient

The reproductive variables [female size (geometric centroid size), fecundity and offspring size (longest diameter of the embryo)] of the livebearer Poecilia vivipara in the quaternary lagoons of northern Rio de Janeiro State varied significantly among sites and were partially associated within and among sites. Mean female size was directly related to salinity. Fecundity (number of offspring) was directly related to female size both within and among sites. The female size × fecundity relationship, however, was not constant among sites. Offspring size was partially and directly associated with female size and salinity. The relationship between fecundity and female size was positively related with fecundity, suggesting a non-linear relationship of these variables when the total sample was considered. The results suggest that life-history differences among sites were more related to different predation regimes than to simple effects of plasticity caused by increased growth in saltwater environments.     

Number and size of clutch in Ptomascopus morio (Coleoptera: Silphidae: Nicrophorinae), with comparisons to Nicrophorus

Ptomascopus morio displays simpler parental care than Nicrophorus species. The effects of carcass size and clutch number on clutch size in P. morio were examined. Clutch size was related to carcass size. There was a negative correlation between number of clutch and clutch size for most sizes of carcass. Longevity of females was shorter when the carcass size was larger, such that total lifetime fecundity did not differ among carcasses of different sizes. The clutch size of P. morio was larger than that of Nicrophorus quadripunctatus. The clutch size of P. morio declined rapidly with repeated clutch production, but that of N. quadripunctatus was rather constant. This indicates that N. quadripunctatus maintains a more constant clutch size than P. morio over several reproductive attempts, although the former displays more complex parental care.