The metabolic rate and its scaling relationship to colony size were studied in the colonial ascidian Botrylloides simodensis. The colonial metabolic rate, measured by the oxygen consumption rate (V O 2 in millilitres of O 2 per hour) and the colony mass (wet weight M w in grams) showed the allometric relationship (V O 2 = 0.0412 M 0 .79 9 w . The power coefficient was statistically not different from 0.75, the value for unitary organisms. The size of the zooids and the tunic volume fraction in a colony were kept constant irrespective of the colonial size. These results, together with the two-dimensional colonial shape, excluded shape factors and colonial composition as possible causes of allometry. Botryllid ascidians show a takeover state in which all the zooids of the parent generation in a colony degenerate and zooids of a new generation develop in unison. The media for connection between zooids such as a common drainage system and connecting vessels to the common vascular system experienced reconstruction. The metabolic rate during the takeover state was halved and was directly proportional to the colonial mass. The scaling thus changed from being allometric to isometric. The alteration in the scaling that was associated with the loss of the connection between the zooids strongly support the hypothesis that the allometry was derived from mutual interaction among the zooids. The applicability of this hypothesis to unitary organisms is discussed.

The allometric scaling of metabolic rate of organisms, the three-quarters power rule, has led to a questioning of the basis for the relation. We attacked this problem experimentally for the first time by employing the modular organism, the ascidian that forms a single layered flat colony, as a model system. The metabolic rate and colony size followed the three-quarters power relation, which held even after the colony size was experimentally manipulated. Our results established that the three-quarters power relation is a real continuous function, not an imaginary statistical regression. The fact that all the hypotheses failed to explain why the two-dimensional organism adhered to the three-quarters power relation led us to propose a new hypothesis, in which the allometric relation derives from the self-organized criticality based on local interaction between modulus-comprising organisms.

SUMMARY In order to characterize the energy expenditure of Paramecium, we simultaneously measured the oxygen consumption rate, using an optic fluorescence oxygen sensor, and the swimming speed, which was evaluated by the optical slice method. The standard metabolic rate (SMR, the rate of energy consumption exclusively for physiological activities other than locomotion)was estimated to be 1.18×10–6 J h–1cell–1 by extrapolating the oxygen consumption rate into one at zero swimming speed. It was about 30% of the total energy consumed by the cell swimming at a mean speed of 1 mm s–1, indicating that a large amount of the metabolic energy (about 70% of the total) is consumed for propulsive activity only. The mechanical power liberated to the environment by swimming Paramecium was calculated on the basis of Stokes' law. This power, termed Stokes power, was 2.2×10–9 J h–1 cell–1, indicating extremely low efficiency (0.078%) in the conversion of metabolic power to propulsion. Analysis of the cost of transport (COT, the energy expenditure for translocation per units of mass and distance) revealed that the efficiency of energy expenditure in swimming increases with speed rather than having an optimum value within a wide range of forced swimming, as is generally found in fish swimming. These characteristics of energy expenditure would be unique to microorganisms, including Paramecium, living in a viscous environment where large dissipation of the kinetic energy is inevitable due to the interaction with the surrounding water.

During the spawning process in starfish, oocytes are arrested at metaphase of meiosis I (MI) within the ovary, and reinitiate meiosis only after they have been released into the seawater. However, this arrest does not occur if the ovary is removed from the animal. As the pH of the coelomic fluid is buffered by CO2/H(+)/HCO3(-), we investigated the involvement of gas concentrations in MI arrest. In vivo, the CO2 level in the coelomic fluid was high (∼1.5% vs. 0.04% in air) and the O2 level was low (0.1-1.0% vs. ∼20% in air). When these gas conditions were reproduced in isolated coelomic fluid or seawater, ovarian oocytes arrested at MI, just as in vivo. Isolated oocytes from the ovary required the similar high CO2 and low O2 level to remain arrested in MI and had an intracellular pH of ∼6.9. Intracellular pH increased to ∼7.3 when oocytes were transferred to seawater equilibrated with air, a condition that mimics that of spawning. We used ammonium acetate to clamp intracellular pH at different levels and found that MI arrest occurred when intracellular pH was ∼6.9. Our results support the idea that high CO2 and low O2 in the ovarian environment lead to low intracellular pH and MI arrest, while spawning into the seawater with low CO2 and high O2 results in high intracellular pH and release from MI arrest. The biological significance of MI arrest is that oocytes are spawned into seawater at the optimal physiological state of MI when the least polyspermy occurs.

O 2 consumption of a single embryo/planula at each developmental stage was monitored in the reef-building coral Acropora intermedia using an optical O 2 -sensing system with our original micro-chamber system (6.28 µl). The lowest rate of O 2 consumption was observed in unfertilized eggs. After fertilization, O 2 consumption increased and remained constant until the prawn chip blastula stage. However, O 2 consumption began to increase again during the bowl-shaped blastula stage, which involves the formation of 2 germ layers and corresponds to the beginning of gastrulation. The rate of O 2 consumption peaked during the teardrop-shaped planula stage. During this stage planulae are able to swim actively, especially in the vertical plane, so an increase in energy consumption during this stage is to be expected. O 2 consumption began to decrease gradually 5 d after spawning. At this stage, the larvae frequently touched the substrate with their concave aboral end, which features numerous spirocysts required for substrate attachment. When the planulae began to settle, 7 d after spawning, the rate of O 2 consumption dropped to that of unfertilized eggs, suggesting that the planulae slowly use stored energy for crawling/settlement behavior and/or post-settlement growth and survivorship.KEY WORDS: Development · Dispersal · Energy · Larva · Lecithotrophic · Metabolism · Recruitment · Settlement-competency period Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 366: [305][306][307][308][309] 2008 developmental stage is an important index for understanding larval dispersal and recruitment; such data indicate when the larvae use energy and how they allocate the maternally derived energy for dispersal potential, larval fitness, and post-settlement growth and survival (Richmond 1987, Hoegh-Guldberg & Manahan 1995.A number of studies have examined the energetics of the development of planktotrophic and lecithotrophic species of sea urchin and abalone (Crisp et al. 1985, Marsh et al. 1999, Bryan 2004. However, the most common method of measuring O 2 consumption (i.e. an electrode) is unsuitable for small chamber volumes because the sensor itself consumes dissolved O 2 to measure the density of O 2 (Clark 1956). In addition, because numerous embryos or planulae compete with each other to consume excess energy in the chamber, the O 2 consumption rate per embryo or planula derived from this method is not reliable for analyzing the transitions between developmental stages. Here, we present data for O 2 consumption of a single coral embryo/planula at each developmental stage using an optical O 2 -sensing system. This system has several advantages: no O 2 consumption, no membrane or electrolytes required (i.e. easy maintenance), high sensitivity and stability, and an adequate chamber volume (Nakaya et al. 2003(Nakaya et al. , 2005. No previous data are available for O 2 consumption in coral embryos or planulae using the technique described here. MATERIALS AND METHODSWe collecte...

Previous studies examining whether the faces of candidates affect election outcomes commonly measure study participants' subjective judgment of various characteristics of candidates, which participants infer based solely on the photographic images of candidates. We, instead, develop a smile index of such images objectively with automated face‐recognition technology. The advantage of applying this new technology is that the automated process of measuring facial traits is by design independent of voters' subjective evaluations of candidate attributes, based on the images, and thus allows us to estimate “undiluted” effects of facial appearance per se on election outcomes. The results of regression analysis using Japanese and Australian data show that the smile index has statistically significant and substantial effects on the vote share of candidates even after controlling for other covariates.

The energy consumption of echinoderms is low in comparison with that of other invertebrates. We demonstrated this by measuring the oxygen consumption rate per unit of body weight (VO2) of the sea cucumber Actinopyga mauritiana: VO2 was 1/8 that of the "standard" invertebrates. Low energy consumption in echinoderms has been attributed to their high skeletal content and to catch connective tissues (CCTs) that maintain body posture by altering their mechanical properties with little energy expenditure. The former is not applicable to holothurians, and the latter has not been proven experimentally. We postulated that the large content of dermal connective tissue, which maintaines posture economically, contributes to the low energy consumption in holothurians. Body-wall dermis occupied 53.5% of wet body weight, whereas body-wall muscles, including those of tube feet, occupied 5.1%. VO2 of the dermis in the stiff state (2.45 microl x g(-1) x h(-1)) was 1/10 that of the longitudinal body-wall muscle in contraction. the mechanical tests revealed that the stress at an imposed strain of 2% strain was 7 times greater in CCT than in muscles. These results showed that CCT could maintain posture more economically than muscles could. We concluded that the high content of connective tissue with energy-saving posture-maintenance activities contributed to the low energy consumption of holothurians.

Spermatozoa released by males should remain viable until fertilization. Hence, sperm longevity is governed by intrinsic and environmental factors in accordance with the male mating strategy. However, whether intraspecific variation of insemination modes can impact sperm longevity remains to be elucidated. In the squid Heterololigo bleekeri, male dimorphism (consort and sneaker) is linked to two discontinuous insemination modes that differ in place and time. Notably, only sneaker male spermatozoa inseminated long before egg spawning can be stored in the seminal receptacle. We found that sneaker spermatozoa exhibited greater persistence in fertilization competence and flagellar motility than consort ones because of a larger amount of flagellar glycogen. Sneaker spermatozoa also showed higher capacities in glucose uptake and lactate efflux. Lactic acidosis was considered to stabilize CO 2 -triggered self-clustering of sneaker spermatozoa, thus establishing hypoxia-induced metabolic changes and sperm survival. These results, together with comparative omics analyses, suggest that postcopulatory reproductive contexts define sperm longevity by modulating the inherent energy levels and metabolic pathways.Sperm traits can evolve through postcopulatory contexts involving sperm competition, cryptic female choice, and insemination/fertilization environments. As consequences of sperm competition (1, 2) and cryptic female choice (3, 4), male individuals of certain species have evolved to produce giant spermatozoa to achieve better fertilization success. Besides morphological traits, the evolutionary forces driven by postcopulatory sexual selection should also favor more effective sperm motility and hence influence their morphological and energetic traits (5), thus facilitating fertilization in polyandrous mating systems. Sperm competition theory predicts that an increased risk of sperm competition (sometimes referred to as female promiscuity) should result in selection for increased sperm swimming velocity. A growing body of evidence has supported this prediction. Thus, a positive relationship between sperm swimming speed and sperm competitiveness was seen not only in external fertilizers such as fish (6 -8) but also in internal fertilizers such as birds (9, 10) and mammals (11). Commonly, polyandrous insemination can occur simultaneously (external fertilization) or sequentially (internal fertilization) toward the same set of eggs. However, in species that employ internal fertilization, female individuals often store spermatozoa in their reproductive tract and use them during multiple ovulation cycles (12-14). Thus, it is possible that spermatozoa with greater longevity might have greater reproductive fitness than those with increased velocity. This implicates that spermatozoa should be able to modulate their energy expenditure adequately depending on the postmating contexts.The coastal squid Heterololigo bleekeri exhibits alternative male mating tactics in which complex polyandrous inseminations occur at different places and...