Seasonal pattern of filial cannibalism by Apogon doederleini mouthbrooding males

In temperate waters of southern Japan, mouthbrooding males of the cardinal fish Apogon doederleini sometimes ate their entire brood within a day of spawning. In spite of annual variation in age structure and length of the breeding season, however, the annual cannibalism rate (broods cannibalized to total broods spawned) was nearly constant, 12–16%. Fish 1 year old frequently cannibalized early broods of the season, especially the first brood, whereas the cannibalism rate by 2 year-old fish did not vary within the season. In contrast, the cannibalism by older males increased late in the season. This tendency was attributed to their different allocation patterns to growth and reproduction. For 1 year-old fish, which can enhance future reproductive success by growth and cannibalizing on early broods instead of mouthbrooding (at relatively low temperatures), this may be a tactic for investing energy in growth. For fish 3 years, which have more breeding cycles and grow little, cannibalizing late broods may be energetic compensation for their poor somatic condition. No seasonal variation of cannibalism by 2 year-old fish can be explained by their intermediate nature of growth and reproduction. Multiple mate availability is one factor facilitating the cannibalism by 2 and 3 + year-old fish whose operational sex ratio is female-biased.     

Conditional and Unconditional Simulation of Healthy Patients' Visual Fields

This paper describes a simulation problem, motivated by the study of glaucoma, a very serious and widespread ocular illness. To ascertain whether a patient suffers from glaucoma, a perimetric test is done, but the evolution of the disease is very slow, and large longitudinal sets of tests taken on the same patient are needed to study its evolution, to analyze the efficiency of existing methods to detect the progression of glaucoma and to develop new ones. Simulation can be a very useful procedure to get appropriate data sets to work with. Our aim in this work is to simulate several VFs in a healthy patient to reflect his evolution in time. We use a spatio‐temporal model to simulate from, taking into account the correlation existing between the observed (or simulated) values in space and time. Two different simulation procedures (unconditional and conditional) are studied, and applied to obtain the simulations we are interested in. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Neutral mutations and repetitive DNA

We have previously shown that computer simulations of processes that generate selectively advantageous changes together with random duplications and deletions give rise to genomes with many different genes embedded in a large amount of dispensable DNA sequence. We now explore the consequences of neutral changes on the evolution of genomes. We follow the consequences of sequence divergences that are neutral when they occur in dispensable sequences or extra copies of genes present in multigene families. We find that when divergence occurs at about the same frequency as duplication/deletion events, genomes carry repetitive sequences in proportion to their size. Inspection of the genomes as they evolved showed that multigene families were generated by relatively recent duplications of single genes and so would be expected to be highly homogeneous.     

Mating behavior of male deer ticksIxodes dammini (Acari: Ixodidae)

To analyze the sexual behavior of male black-legged deer ticks Ixodes dammini,we collected ticks infesting 202 white-tailed deer. On average, 17.7 males and 8.8 females infested each deer. Field-collected males copulated with a mean of 2.25 females, and virgin males mated with 2.4 females. On experimental hosts, males established sexual contact with feeding females and repelled other males, and about half remained paired after their mate detached. Engorged females continue to be receptive, and males mate more readily with them than with nonfed females. We conclude that male I. damminiare endowed with a repertoire of behaviors which favor an opportunistic mating before seeking a host and a preference for mating with feeding females on the host accompanied by tenacious mate guarding.     

Total root length as estimated from small sub-samples

A method is proposed for estimating the total length of a root system from sub-samples. This method is based on the measurement of the length and diameter of small pieces of roots, and on the measurements of the bulk density of root sub-samples. It is assumed that roots are cylinders with a given bulk density. The length and diameter of small root pieces are measured by image analysis. A weighted quadratic mean (W.Q.M.) root diameter is then calculated and used in estimating the root length. This W.Q.M. diameter is defined as the real mean diameter of an equivalent single root with the same length and volume as the tested root system. The accuracy of prediction is demonstrated for one theoretical root system. The standard deviation of estimation can be calculated using sampling simulations.     

Confidence Intervals on Ratios of Variance Components for the Unbalanced Two Factor Nested Model

The model considered in this article is the two-factor nested unbalanced variance component model: for p = 1, 2, …, P; q = 1, 2, …, Q_p; and r = 1, 2, …, R_pq. The random variables Y_pqr are observable. The constant μ is an unknown parameter, and A_p, B_pq and C_pqr are (unobservable) normal and independently distributed random variables with zero means and finite variances σ²_A, σ²_B, and σ²_C, respectively. Approximate confidence intervals on ?_A and ?_B using unweighted means are derived, where The performance of these approximate confidence intervals are evaluated using computer simulation. The simulated results indicate that these proposed confidence intervals perform satisfactorily and can be used in applied problems.     

Effect of Zeitgeber Intensity Reduction on a Simulated Dual-Oscillator Human Circadian System: Classical and Dynamic Analysis

The two-oscillator model of human circadian rhythmicity was analyzed when a zeitgeber relative intensity of 1, 0.5, or 0.1 was introduced into the equations. Fourier analysis was compared with dynamic analysis such as attractor reconstruction or Liapunov exponent calculation. After a 50 or 90% reduction in zeitgeber intensity, the dynamics of the system became equivalent and differed significantly from those of a system with maximal zeitgeber intensity. When 10% aleatory noise was added to the data, the analysis was still applicable, and the results obtained were essentially the same as in the absence of noise. Dynamic analysis could thus provide a distinct classification for periodic data, based on the type of analysis.     

Stochastic simulation of clonal growth in the tall goldenrod,Solidago altissima

Summary As clonal plants grow they move through space. The movement patterns that result can be complex and difficult to interpret without the aid of models. We developed a stochastic simulation model of clonal growth in the tall goldenrod, Solidago altissima. Our model was calibrated with field data on the clonal expansion of both seedlings and established clones, and model assumptions were verified by statistical analyses.When simulations were based on empirical distributions with long rhizome lengths, there was greater dispersal, less leaf overlap, and less spatial aggregation than when simulations were based on distributions with comparatively short rhizome lengths. For the field data that we utilized, variation in rhizome lengths had a greater effect than variation for either branching angles or rhizome initiation points (see text). We also found that observed patterns of clonal growth in S. altissima did not cause the formation of fairy rings. However, simulations with an artificial distribution of branching angles demonstrate that fairy rings can result solely from a plant's clonal morphology.Stochastic simulation models that incorporated variation in rhizome lengths, branching angles, and rhizome initiation points produced greater dispersal and less leaf overlap than deterministic models. Thus, variation for clonal growth parameters may increase the efficiency of substrate exploration by increasing the area covered and by decreasing the potential for intraclonal competition. We also demonstrated that ramet displacements were slightly, but consistently lower in stochastic simulation models than in random-walk models. This difference was due to the incorporation of details on rhizome bud initiation into stochastic simulation models, but not random-walk models. We discuss the advantages and disadvantages of deterministic, stochastic simulation, and random-walk models of clonal growth.     

Reduced orthostatic tolerance following 4 h head-down tilt

The cardiovascular responses to a 10-min 1.22 rad (70 degrees) head-up tilt orthostatic tolerance test (OST) was observed in eight healthy men following each of a 5-min supine baseline (control), 4 h of 0.1 rad (6 degrees) head-down tilt (HDT), or 4 h 0.52 rad (30 degrees) head-up tilt (HUT). An important clinical observation was presyncopal symptoms in six of eight subjects following 4 h HDT, but in no subjects following 4 h HUT. Immediately prior to the OST, there were no differences in heart rate, stroke volume, cardiac output, mean arterial pressure and total peripheral resistance for HDT and HUT. However, stroke volume and cardiac output were greater for the control group. Mean arterial pressure for the control group was less than HDT but not HUT. Over the full 10-min period of OST, the mean arterial pressure was not different between groups. Heart rate increased to the same level for all three treatments. Stroke volume decreased across the full time period for control and HDT, but only at 3 and 9 min for HUT. There was a higher total peripheral resistance in the HDT group than control or HUT. The pre-ejection period to left ventricular ejection time ratio was less in HDT than for control or HUT groups. These data indicate a rapid adaptation of the cardiovascular system to 4 h HDT that appears to be inappropriate on reapplication of a head to foot gravity vector. We speculate that the cause of the impaired orthostatic tolerance is decreased tone in venous capacitance vessels so that venous return is inadequate.     

A comparison of the accuracy and precision of several open-water oxygen productivity techniques

Several methods for the estimation of the reaeration coefficient were compared by determining the ability of the methods to recover the correct K value from a computer-simulated stream oxygen record affected by a variety of non-ideal conditions. Noisy data and long observation intervals were not a serious problem for most methods. Saturating photosynthesis, fluctuating light intensity, afternoon depression and temperature variation caused failures by some methods but were well handled by others. Serious impairment of all methods occurred with low productivity or high K. In general, the best-performing methods were the modified hysteresis, nighttime regression, daytime regression, Odum and Hornberger-Kelly daytime methods.