Scaling of rectal gland mass in the European lesser-spotted dogfish

In the European lesser-spotted dogfish Scyliorhinus canicula , rectal gland mass in mg ( M _Rg) followed the allometric relationship: M _Rg = 1·15 M ^0·68, where M is body mass (g). The concept of allometric scaling is an important consideration in studies investigating the function of osmoregulatory organs.     

Scaling of Sexual Dimorphism in Body Mass: A Phylogenetic Analysis of Rensch's Rule in Primates

We examined the relationship between body mass dimorphism, measured as the natural logarithm of the male/female ratio, and body mass, defined as ln (female mass), with interspecific allometry, phylogenetically independent contrasts, and phylogenetic autocorrelation in 105 primate species. We repeated the analyses for Strepsirhini (N = 23), Haplorhini (N = 82), Platyrrhinii (N = 32), and Catarrhini (N = 47). With independent contrasts, there is statistically significant (p < .05) positive allometry in Primates in general, Haplorhini, and Catarrhini, but not in Strepsirhini or Platyrrhini. The steepest slope (0.134) is for Catarrhini. Results differed when we conducted analyses with traditional interspecific allometry. For example, not only was the Catarrhini slope not statistically significant but also the magnitude of the slope was shallower than that of all other groups, except Strepsirhini. The results indicate that phylogenetic effects influence the scaling of sexual size dimorphism, and that the statistical method used has a large impact on the interpretation of this biological relationship. We discuss issues involved in applying these statistical methods in detail.     

Reactive oxygen species production and discontinuous gas exchange in insects

While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production.     

Diffusion in gas exchange of insects

The air-filled tracheal system constitutes the organ for gas exchange in terrestrial insects-its finest branches, the tracheoles, contacting individual cells. In the pupal stage, in which the animal lacks significant ventilatory movement, diffusion in the gas phase of the tracheal system constitutes the only mechanism for gas transfer between the environment and the tissues, transport in the hemolymph being insignificant. We have attempted to identify the main sites of diffusional resistance in the tracheal gas system by measuring the evolution of inert gases of low solubility from the pupa of the giant silkworm moth (Hyalophora cecropia). The results are compatible wih a single model in which the resistance to diffusional gas transfer in the tracheal system is concentrated at its opening at the body surface (spiracle).     

Test of the Optimal Body Size Model for Strepsirhines

We determined if data on strepsirhine body and home range sizes support an optimal body size (OBS) model of 100 g, as predicted from studies of energetics in terrestrial mammals. We also tested the following predictions of the OBS model: 1) relationships between body and home range sizes will change slope and sign above and below the OBS threshold of 100 g and 2) best-fit lines for OBS regression models (above and below the 100-g threshold) will intersect at ca. 100 g (range of 80–250 g). We collected data on body mass, home range size, and vertical ranging behavior for 37 strepsirhines from the literature. Linear regression analyses and phylogenetic independent contrasts methods revealed that body size is a significant determinant of both 2-dimensional (ha) and 3-dimensional (km³) home range sizes only in taxa weighing >100 g. There were consistent changes in the sign of the slopes above and below the OBS threshold. The intersections of the best-fit lines were within the OBS range for the body size to 3-dimensional home range comparisons. Thus, the data provide some support for the OBS model in strepsirhines. However, no regression model was statistically significant for the taxa below the OBS threshold, which may reflect small sample sizes. Also, no slope differed significantly between taxa above and below the OBS. Significant correlations between body and home range sizes for the complete data sets refute the √-shaped constraint space predicted via the OBS model.     

Diversity in gas exchange and muscular activity patterns in insects studied by a respirometer-actograph

Different events in insect gas exchange and muscular activity are described by a new system of automatic respirometers, a differential electrolytic microrespirometer-actograph. This is very sensitive to volumetric changes caused by insect respiration and/or body movements. In this system, oxygen generation and its regulation are combined in the same current circuit. According to this principle, the oxygen consumed by the insect is continuously replaced by equal amounts of electrolytically produced oxygen. This simple laboratory-made apparatus records simultaneously metabolic rate, the cyclicity of external gas exchange, rhythms of muscular ventilating and the pattern of other body movements, including abdominal pulsations not observable with the naked eye. The respirometer-actograph described here is applicable also to the recording of the respiration of other terrestrial arthropods or other living organisms or tissues.     

Scaling of tree vascular transport systems along gradients of nutrient supply and altitude

A recent metabolic scaling theory predicts that plants minimize resistance to hydraulic conduction in the bulk transport network by narrowing the diameter of xylem conduits distally. We hypothesized that trees growing at high altitude or on nutrient-depleted soils would prioritize survival over minimizing hydraulic resistance, and that their vascular systems would be structured differently from those of trees growing under more benign conditions. In fact, conduits were observed to narrow towards the periphery of vascular system within all 45 trees of three species we investigated, and scaling relationships were indistinguishable across a range of environments. Thus, conduit tapering relationships appear to be invariant with respect to environmental conditions.     

东方蝾螈性二型性特征分析

以东方蝾螈大别山种群为实验材料,随机选取162只蝾螈(雄52只,雌110只),通过单变量、双变量、多变量分析的方法,进行11项体征的测量分析.结果表明,头体长是本研究的最适单变量,且头体长与腋胯距之间的相关性最高;PCl在雄性和雌性中均与头体长密切相关,且大多数体征与头体长进行比例分析均显示出异速生长关系,东方蝾螈性二型性普遍存在.本研究中11项体征呈现符合Renseh法则的雌性依赖性二型性演化特征,这种性二型性特征可能是一系列复杂的非对称性选择的结果.     

Scaling of the marsupial middle ear and its functional significance

The marsupial middle ear performs an anatomical impedance matching for acoustic energy travelling in air to reach the cochlea. The size of the middle ear sets constraints for the frequencies transmitted. For generalized placental mammals, it has been shown that the limit for high-frequency hearing can be predicted on the basis of middle ear ossicle mass, provided that the ears fulfil requirements of isometry. We studied the interspecific size variation of the middle ear in 23 marsupial species, with the following measurable parameters: skull mass, condylobasal length, ossicular masses for malleus, incus and stapes, tympanic membrane area, oval window area, and lever arm lengths for malleus and incus. Our results show that the middle ear size grows with negative allometry in relation to body size and that the internal proportions of the marsupial middle ear are largely isometric. This resembles the situation in placental mammals and allows us to use their isometric middle ear model to predict the high-frequency hearing limit for marsupials. We found that the isometry model predicts the high-frequency hearing limit for different marsupials well, indicating that marsupials can be used as auditory models for general therian mammalian hearing. At very high frequencies, other factors, such as the inner ear, seem to constrain mammalian hearing.     

Scaling of xylem vessels and veins within the leaves of oak species

General models of plant vascular architecture, based on scaling of pipe diameters to remove the length dependence of hydraulic resistance within the xylem, have attracted strong interest. However, these models have neglected to consider the leaf, an important hydraulic component; they assume all leaves to have similar hydraulic properties, including similar pipe diameters in the petiole. We examine the scaling of the leaf xylem in 10 temperate oak species, an important hydraulic component. The mean hydraulic diameter of petiole xylem vessels varied by 30% among the 10 oak species. Conduit diameters narrowed from the petiole to the midrib to the secondary veins, consistent with resistance minimization, but the power function scaling exponent differed from that predicted for stems. Leaf size was an organizing trait within and across species. These findings indicate that leaf vasculature needs to be included in whole-plant scaling models, for these to accurately reflect and predict whole-plant transport and its implications for performance and ecology.     

FURTHER EVIDENCE FOR ANOMALOUS SIZE SCALING OF RESPIRATION IN PHYTOPLANKTON1

Respiration per unit mass decreases as organism size increases among metazoans and heterotrophic unicells. The rate of decrease is described by a power function of organism mass; the exponent of the power function is 0.75 (Three-fourths Rule). Previously unanalyzed respiration rates for 11 species of phytoplankton ranging in size over four orders of magnitude show a size-scaling exponent of 1.13 (SE, ±0.15), which is statistically different from 0.75. This result confirms the result of an earlier study of eight phytoplankton species indicating that size scaling of respiration is absent or minimal in phytoplankton, in contrast to the pattern of heterotrophic unicells. The size-related range of respiration rates per unit mass across the full size spectrum of phytoplankton would be approximately 18–fold if respiration were scaled according to the Three-fourths Rule. If respiration does not scale with size or scales minimally with size, as suggested by present evidence, the size-related range of rates will be much smaller or negligible. The apparent anomaly of size scaling for phytoplankton respiration is potentially of great ecological and adaptive significance in unicellular algae.