Immature Period Research Articles

A novel method to develop an animal model of depression using a small mobile robot

Robotics is contributing to studies on animal behavior. Mobile robots are actually used as devices to give external stimulus to animals in several experiments. We consider that this approach can be applied to studies in psychic medicine. In psychic medicine, all new drugs are evaluated in experiments using animal models of mental disorder before using it in clinical practice. However, conventional animal models have some problems in the construct validity. The animal models should be developed through the method which is consistently associated with the theory of the mental disorders while many of conventional models had been developed by genetic manipulations or surgical operations on nerve system. We considered that a novel animal model could be developed by stress exposure using a small mobile robot. We then implemented this method to the experimental system which had been developed in our past study. An experiment was conducted using the system, and the method was then verified. Therefore, we conclude that the animal model of depression developed by proposed method, exposing continuous attack by the robot in immature period and interactive attack in mature period, can be a novel animal model of depression.

Urodynamic and morphometric characteristics of the lower urogenital tracts of female Beagle littermates during the sexually immature period and first and second estrous cycles

To compare values of lower urogenital tract urodynamic and morphometric variables determined during the prepubertal (sexually immature) period and first and second estrous cycles in healthy female Beagle littermates to determine functional and anatomic changes of the lower urogenital tract during those periods. 5 female Beagle littermates. Urethral pressure profilometry, diuresis cystometry, and vaginourethrography were performed when dogs were 3.5, 4.5, 5, 6, 7, 8, 8.5, and 9 months old and during proestrus; estrus; early, middle, and late diestrus; and early and late anestrus of the first and second estrous cycles. At the end of the prepubertal period, values of urodynamic and morphometric variables increased significantly, compared with values at earlier times. Maximum bladder capacity developed when dogs were 9 months old. In all dogs, the bladder was intermittently located in an intrapelvic position during the prepubertal period; the bladder was intra-abdominal from the time dogs were 9 months old until the end of the study. Urethral pressure decreased significantly during estrus and early diestrus of the first and second estrous cycles. Bladder capacity increased significantly during diestrus of both estrous cycles. Urethral and vaginal lengths were significantly longer during proestrus and estrus than they were during anestrus. Values of lower urogenital tract urodynamic and morphometric variables were influenced by age and phases of the estrous cycle of immature and young adult Beagles in this study. Age of dog and phase of estrous cycle should be considered when interpreting urodynamic and vaginourethrography data.

The power of possibility: causal learning, counterfactual reasoning, and pretend play.

We argue for a theoretical link between the development of an extended period of immaturity in human evolution and the emergence of powerful and wide-ranging causal learning mechanisms, specifically the use of causal models and Bayesian learning. We suggest that exploratory childhood learning, childhood play in particular, and causal cognition are closely connected. We report an empirical study demonstrating one such connection--a link between pretend play and counterfactual causal reasoning. Preschool children given new information about a causal system made very similar inferences both when they considered counterfactuals about the system and when they engaged in pretend play about it. Counterfactual cognition and causally coherent pretence were also significantly correlated even when age, general cognitive development and executive function were controlled for. These findings link a distinctive human form of childhood play and an equally distinctive human form of causal inference. We speculate that, during human evolution, computations that were initially reserved for solving particularly important ecological problems came to be used much more widely and extensively during the long period of protected immaturity.

Gender Differences in Transcriptional Signature of Developing Rat Testes and Ovaries following Embryonic Exposure to 2,3,7,8-TCDD

Dioxins are persistent organic pollutants interfering with endocrine systems and causing reproductive and developmental disorders. The objective of our project was to determine the impact of an in utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on reproductive function of male and female offspring in the rat with a special emphasis on the immature period. We used a low dose of TCDD (unique exposure by oral gavage of 200 ng/kg at 15.5 days of gestation) in order to mirror a response to an environmental dose of TCDD not altering fertility of the progeny. We choose a global gene expression approach using Affymetrix microarray analysis, and testes of 5 days and ovaries of 14 days of age. Less than 1% of the expressed genes in gonads were altered following embryonic TCDD exposure; specifically, 113 genes in ovaries and 56 in testes with 7 genes common to both sex gonads. It included the repressor of the aryl hydrocarbon receptor (Ahrr), the chemokines Ccl5 and Cxcl4 previously shown to be regulated by dioxin in testis, Pgds2/Hpgds and 3 others uncharacterized. To validate and extend the microarray data we realized real-time PCR on gonads at various developmental periods of interest (from 3 to 25 days for ovaries, from 5 to the adult age for testes). Overall, our results evidenced that both sex gonads responded differently to TCDD exposure. For example, we observed induction of the canonic battery of TCDD-induced genes coding enzymes of the detoxifying machinery in ovaries aged of 3–14 days of age (except Cyp1a1 induced at 3–10 days) but not in testes of 5 days (except Ahrr). We also illustrated that inflammatory pathway is one pathway activated by TCDD in gonads. Finally, we identified several new genes targeted by TCDD including Fgf13 in testis and one gene, Ptgds2/Hpgds regulated in the two sex gonads.

Visual Loss in Orbitofacial Neurofibromatosis Type 1

On occasion, neurofibromas in neurofibromatosis type 1 may be present on the lid, brow, or face of an infant or child, a circumstance commonly referred to as "orbitofacial neurofibromatosis" (OFNF). The present study evaluates the causes and extent of visual loss in a group of patients with OFNF. Case series. Fifty-five patients with OFNF. Retrospective medical record review and reexamination of selected patients from one institution. Visual acuity and identification of underlying cause of reduced vision. Fifty patients with unilateral OFNF (23 male, 27 female, aged 4-48 years at last visit) and 5 patients with bilateral OFNF (2 male, 3 female, aged 15-43 years) had adequate information available to assess afferent visual functioning. Nine patients (4 male, 5 female, aged 4-28 years) had optic pathway glioma (OPG) in addition to OFNF. Patients were followed as long as 27 years (mean 8.4 years). Thirty-nine patients (71% of total) had visual acuity of ≤20/60 on the side of OFNF involvement (or the side of worse OFNF involvement in patients with bilateral disease). One or more causes of amblyopia were present in 29 of these patients, 19 patients had organic disease of the eye (e.g., glaucoma or retinal detachment) or the afferent system (e.g., OPG), and 12 patients had correctable refractive errors. Visual loss in this OFNF cohort was common, typically profound, and usually multifactorial. Some causes of visual loss (including congenital glaucoma with buphthalmos and retinal detachment, disconjugate gaze due in part to distorted skull development causing strabismic amblyopia, and OPG) were difficult to treat adequately and tended to cause progressive, profound visual loss. Therefore, careful observation should be made during the period of visual immaturity for possible causes of amblyopia that might be treatable, such as refractive changes, occlusion of the visual axis, or congenital glaucoma. As affected individuals get older, physicians must be vigilant for the progression of optic nerve disease due to glaucoma or OPG and to the possibility that vision might be improved by refraction.

Neonatal pain in relation to postnatal growth in infants born very preterm

Procedural pain is associated with poorer neurodevelopment in infants born very preterm (⩽32weeks gestational age), however, the etiology is unclear. Animal studies have demonstrated that early environmental stress leads to slower postnatal growth; however, it is unknown whether neonatal pain-related stress affects postnatal growth in infants born very preterm. The aim of this study was to examine whether greater neonatal pain (number of skin-breaking procedures adjusted for medical confounders) is related to decreased postnatal growth (weight and head circumference [HC] percentiles) early in life and at term-equivalent age in infants born very preterm. Participants were n=78 preterm infants born ⩽32weeks gestational age, followed prospectively since birth. Infants were weighed and HC measured at birth, early in life (median: 32weeks [interquartile range 30.7–33.6]) and at term-equivalent age (40weeks [interquartile range 38.6–42.6]). Weight and HC percentiles were computed from sex-specific British Columbia population-based data. Greater neonatal pain predicted lower body weight (Wald χ2=7.36, P=0.01) and HC (Wald χ2=4.36, P=0.04) percentiles at 32weeks postconceptional age, after adjusting for birth weight percentile and postnatal risk factors of illness severity, duration of mechanical ventilation, infection, and morphine and corticosteroid exposure. However, later neonatal infection predicted lower weight percentile at term (Wald χ2=5.09, P=0.02). Infants born very preterm undergo repetitive procedural pain during a period of physiological immaturity that appears to impact postnatal growth, and may activate a downstream cascade of stress signaling that affects later growth in the neonatal intensive care unit.

Damage effect of two storage mites (Acari: Acaridida) and their biology on the Shiitake mushroom (Lentinula edodes) at three constant temperatures

This study aims to estimate the influence of three constant temperatures (20, 25 and 30°C) on the damage effect, population growth, life cycle and longevity of two stored-product mites (Tyrophagus putrescentiae and Aleuroglyphus ovatus) reared on the dried Shiitake mushroom (Lentinula edodes) at 80% relative humidity (r.h.) and 14:10 (L:D) h (light: dark) photoperiod. The weight loss of the Shiitake mushroom caused by T. putrescentiae and A. ovatus increased with increasing temperature. The increase in the count of T. putrescentiae and A. ovatus in the rearing cells led to noticeable decrease in the weight of the Shiitake mushroom. The results indicated that T. putrescentiae was more harmful than A. ovatus on the Shiitake mushroom. The r-values of both mite species increased with increase in temperature up to 25°C, whereas the value of r decreased when the temperature increased to 30°C. At 20, 25 and 30°C, the values of r were 0.167, 0.182 and 0.159 for T. putrescentiae and 0.126, 0.140 and 0.115 for A. ovatus, respectively. The developmental time of immature stages, reproductive periods and female longevity of T. putrescentiae and A. ovatus were adversely affected by the increase in temperature. The life cycle of T. putrescentiae varied from 9.26 to 20.64 days and that of A. ovatus ranged from 11.65 to 25.21 days when the temperature increased from 20 to 30°C. The longest longevity of T. putrescentiae and A. ovatus (38.37 and 48.18 days) was recorded at 20°C, whereas the shortest (20.38 and 28.40 days) was found at 30°C. The results showed that T. putrescentiae had lower developmental time and reproductive periods than A. ovatus when reared on the Shiitake mushroom at all the studied temperatures.

Impact of different cotton (Gossypium spp.) cultivars, as host plant, on development and fertility life-table parameters of Tetranychus urticae (Acari: Tetranychidae)

The effect of five cotton cultivars (Varamin, Mehr, Bakhtegan, Sahel, Saiokra) on the fitness of Tetranychus urticae was assessed by determining the developmental time and fertility life-table parameters for mites on leaf discs at 25 ± 1°C, 70 ± 10% relative humidity and 16:8 hours light:dark photoperiod. To investigate this effect, the duration of each life stage, longevity, reproduction rate and fertility life-table parameters including intrinsic rate of natural increase (r m), net reproductive rate (R 0), mean generation time (T), doubling time (DT) and finite rate of increase (λ) of the two-spotted spider mite on different cotton cultivars were calculated. The results indicated that the Varamin cultivar was the most suitable one for two-spotted spider mite among the tested plants because of its shorter immature developmental period and higher reproduction and intrinsic rate of natural increase, whereas Bakhtegan was the least suitable cultivar because of the longer immature developmental time and the lowest reproduction rate and intrinsic rate of natural increase. The lowest r m value suggests an antibiosis resistance in this cultivar in comparison with other cultivars.

The neural bases of social pain: evidence for shared representations with physical pain.

Experiences of social rejection or loss have been described as some of the most "painful" experiences that we, as humans, face and perhaps for good reason. Because of our prolonged period of immaturity, the social attachment system may have co-opted the pain system, borrowing the pain signal to prevent the detrimental consequences of social separation. This review summarizes a program of research that has explored the idea that experiences of physical pain and social pain rely on shared neural substrates. First, evidence showing that social pain activates pain-related neural regions is reviewed. Then, studies exploring some of the expected consequences of such a physical pain-social pain overlap are summarized. These studies demonstrate that a) individuals who are more sensitive to one kind of pain are also more sensitive to the other and b) factors that increase or decrease one kind of pain alter the other in a similar manner. Finally, what these shared neural substrates mean for our understanding of socially painful experience is discussed.

호박꽃과실파리 온도 발육모형

The striped fruit fly, Bactrocera scutellata, damages pumpkin and other cucurbitaceous plants. The developmental period of each stage was measured at seven constant temperatures (15, 18, 21, 24, 27, 30, and ). The developmental time of eggs ranged from 4.2 days at to 0.9 days at . The developmental period of larvae was 4.2 days at , and slowed in temperatures above . The developmental period of pupa was 21.5 days at and 7.6 days at . The mortality of eggs was 17.1% at and 22.9% at , Larval mortalities (1st, 2nd, 3rd) were 24.1, 27.3 and 18.2%, respectively, at , Pupal mortalities were 18.2% at and 23.1% at . The relationship between developmental rate and temperature fit both a linear model and a nonlinear model. The lower threshold temperatures of eggs, larvae, and pupae were 12.5, 10.7, and , respectively, and threshold temperature of the total immature period was . The thermal constants required to complete the egg, larval, and pupal stages were 33.2, 118.3, and 181.2 DD, respectively. The distribution of each development stages was described by a 3-parameter Weibull function.

THE WATER RELATIONS OF RUBBER (HEVEA BRASILIENSIS): A REVIEW

SUMMARYThe results of research done on water relations of rubber are collated and summarised in an attempt to link fundamental studies on crop physiology to crop management practices. Background information is given on the centres of origin (Amazon Basin) and production of rubber (humid tropics; south-east Asia), but the crop is now being grown in drier regions. The effects of water stress on the development processes of the crop are summarised, followed by reviews of its water relations, water requirements and water productivity. The majority of the recent research published in the international literature has been conducted in south-east Asia. The rubber tree has a single straight trunk, the growth of which is restricted by ‘tapping’ for latex. Increase in stem height is discontinuous, a period of elongation being followed by a ‘rest’ period during which emergence of leaves takes place. Leaves are produced in tiers separated by lengths of bare stem. Trees older than three to four years shed senescent leaves (a process known as ‘wintering’). ‘Wintering’ is induced by dry, or less wet, weather; trees may remain (nearly) leafless for up to four weeks. The more pronounced the dry season the shorter the period of defoliation. Re-foliation begins before the rains start. The supply of latex is dependent on the pressure potential in the latex vessels, whereas the rate of flow is negatively correlated with the saturation deficit of the air. Radial growth of the stem declines in tapped trees relative to untapped trees within two weeks of the start of tapping. Roots can extend in depth to more than 4 m and laterally more than 9 m from the trunk. The majority of roots are found within 0.3 m of the soil surface. Root elongation is depressed during leaf growth, while root branching is enhanced. Stomata are only found on the lower surface of the leaf, at densities from 280 to 700 mm−2. The xylem vessels of rubber trees under drought stress are vulnerable to cavitation, particularly in the leaf petiole. By closing, the stomata play an essential role in limiting cavitation. Clones differ in their susceptibility to cavitation, which occurs at xylem water potentials in the range of −1.8 to −2.0 MPa. Clone RRII 105 is capable of maintaining higher leaf water potentials than other clones because of stomatal closure, supporting its reputation for drought tolerance. Clones differ in their photosynthetic rates. Light inhibition of photosynthesis can occur, particularly in young plants, when shade can be beneficial. Girth measurements have been used to identify drought-tolerant clones. Very little research on the water requirements of rubber has been reported, and it is difficult to judge the validity of the assumptions made in some of the methodologies described. The actual evapotranspiration rates reported are generally lower than might be expected for a tree crop growing in the tropics (<3 mm d−1). Virtually no research on the yield responses to water has been reported and, with the crop now being grown in drier regions, this is surprising. In these areas, irrigation can reduce the immaturity period from more than 10 years to six years. The important role that rubber plays in the livelihoods of smallholders, and in the integrated farming systems practised in south-east Asia, is summarized.

Parasitoid Quality of Gronotoma micromorpha Parasitizing Liriomyza huidobrensis on Chinese Cabbage and Soybean

A study with the aim to investigate the quality of Gronotoma micromorpha which attack the immature developmental stages of Liriomyza huidobrensis has been carried out. Such variables as body length measured from caput to the tip of abdomen, wing span and the length of tibia of hind leg were measured to represent parasitoid quality. The immature developmental stage period of the parasitoid was also recorded. The result indicated that a better quality Gronotoma was obtained when it was developed in the Liriomyza larvae fed on chinese cabbage with the average of 123.85 μm for body length, 253.45 μm for wing span, and 42.85 μm for the length of hind tibia, respectively. When Gronotoma was developed in the Liriomyza larvae fed on soy bean, its size became smaller with the average of 97.7 μm for body length, 214.3 μm for wing span, and 37.2 μm for the hind tibia. When it is developed in the Liriomyza on chinese cabbage host plant the immature developmental period of Gronotoma is sligthly shorter with the average of 18.4 and 17.3 days for which developed in the larvae and pupa respectively and on soy bean it become longer with the average of 19.2 days for in eggs, 19.9 days for that in the larvae. On chinese cabbage, Liriomyza tend to have bigger size for both flies and pupae.

Glutamate receptor δ2 is essential for input pathway-dependent regulation of synaptic AMPAR contents in cerebellar Purkinje cells

Thus far the identification and functional characterization of the molecular mechanisms underlying synaptic plasticity, learning, and memory have not been particularly dissociated from the contribution of developmental changes. Brain plasticity mechanisms have been largely identified and studied using in vitro systems mainly derived from early developmental ages, yet they are considered to be general plasticity mechanisms underlying functions -such as long-term memory- that occurs in the adult brain. Although it is possible that part of the plasticity mechanisms recruited during development is then re-recruited in plasticity responses in adulthood, systematic investigations about whether and how activity-dependent molecular responses differ over development are sparse. Notably, hippocampal-dependent memories are expressed relatively late in development, and the hippocampus undergoes and extended developmental post-natal structural and functional maturation, suggesting that the molecular mechanisms underlying hippocampal neuroplasticity may actually significantly change over development. Here we quantified the relative basal expression levels of sets of plasticity, synaptic, glia and connectivity proteins in rat dorsal hippocampus, a region that is critical for the formation of long-term explicit memories, at two developmental ages, postnatal day 17 (PN17) and PN24, which correspond to a period of relative functional immaturity and maturity, respectively, and compared them to adult age. We found that the levels of numerous proteins and/or their phosphorylation, known to be critical for synaptic plasticity underlying memory formation, including immediate early genes (IEGs), kinases, transcription factors and AMPA receptor subunits, peak at PN17 when the hippocampus is not yet able to express long-term memory. It remains to be established if these changes result from developmental basal activity or infantile learning. Conversely, among all markers investigated, the phosphorylation of calcium calmodulin kinase II α (CamKII α and of extracellular signal–regulated kinases 2 (ERK-2), and the levels of GluA1 and GluA2 significantly increase from PN17 to PN24 and then remain similar in adulthood, thus representing correlates paralleling long-term memory expression ability.

Experimental Tests of Endocrine Function in Breeding and Nonbreeding Raptors

Many long-lived avian species defer reproduction for several years, often displaying a "floating" behavior characterized by the lack of mates and exclusive territories. Understanding the proximate mechanisms regulating floating behavior is a relevant topic of research for physiologists, behavioral ecologists, and population biologists because a prolonged period of nonbreeding can negatively affect lifetime fitness and change population dynamics. Here we tested two hypotheses linking endocrine function to floating status: (a) floaters undergo a period of sexual immaturity characterized by lower gonadal function (hypothesis of sexual immaturity), and (b) floating status is socially imposed by dominant conspecifics and revealed by the adrenocortical response to stress (hypothesis of social subordination). The two hypotheses were tested in a population of free-living black kites Milvus migrans in Doñana National Park (southwest Spain), where breeders coexist with young floaters that defer reproduction for 3-7 yr. Hypophysial-gonadal function, estimated as androgen production in response to experimental challenge with gonadotropin-releasing hormone (c-GnRH-I), was similar in magnitude and timing between floating and breeding males. The same treatment was, however, unable to elicit any response in terms of increasing estradiol or total androgen levels in females regardless of their breeding status. Following experimental capture and restraint, the adrenocortical response to stress (estimated as circulating corticosterone levels) was higher in floating than in breeding males, while females showed the opposite pattern (i.e., lower response to stress in young floaters compared with breeders). Contrary to the hypothesis of sexual immaturity, our results suggest that floating males are physiologically capable of reproducing. The reported differences in adrenocortical function support the idea that floaters are socially subordinate to breeders, and corticosterone responses reflect the sex-specific roles during competition in socially monogamous species.

Generational Economics in a Changing World

Across the developed world, generous welfare state programs for the elderly, together with projected doublings or more in the proportion old, have led to political struggles that sometimes pit younger generations against the elderly. The goal of this chapter is to put the current situation in historical and institutional context. We begin with a brief review of research on hunter-gatherer groups, and then turn to substantive results for modern-day countries at different stages of economic development drawn from the National Transfer Accounts project, a large international collaboration. Human hunter-gatherer offspring have an exceptionally long period of immaturity and nutritional dependency, lasting until around age 20 years, judging by studies of contemporary groups (Kaplan 1994; Hill and Hurtado 2009; Howell 2010). Adults at all ages up to around 70 years produced more calories than they consumed on average, contributing their surplus to feed the young. The modern demographic transition began many thousands of years after hunting and gathering had been displaced by agriculture as the dominant form of production technology and social organization. The demographic transition eventually led to a much-reduced proportion of children in the population and a very much increased proportion of elderly. Given the intergenerational transfer patterns of hunter-gatherers just described, including the net productivity of the elderly, one would have expected that population aging would relax the social budget constraint, as the ratio of adults to children soared. But a funny thing happened along the way: societies invented retirement, older people became increasingly dependent on younger adults, and the economic consequences of population aging are now viewed with alarm. We explore the interaction of the transition’s changing population age distributions with the changing organization of the economic life cycle and with differing institutional arrangements. We draw on estimates by 23 country teams participating in the National Transfer Accounts project. (The researchers are identified and more detailed information is available for many countries in working papers on the NTA website: «www.ntaccounts.org».) We show that the direction of intergenerational transfers in the population has shifted from downward to upward, at least in a few leading rich nations. This sea change has resulted in part from the changing economic role of the elderly, which is closely tied to the rise of the welfare state and the increasing importance of assets, and in part from population aging brought about by the demographic transition. Despite the change in the net direction of resource flows, investment in health and education per child has risen relative to incomes, in association with fertility decline. The degree to which these changes have occurred varies across levels of economic development, broad regions of the world, and the idiosyncratic institutions of particular countries. It is well known, however, that the systems of public transfers to the elderly as currently structured will not be fiscally sustainable as populations continue to age rapidly in the first half of the twenty-first century. Structural reforms will occur and in some cases have already been made, and the outcome is likely to be a reversal in the trend toward earlier retirement and related changes.

Dental evidence for ontogenetic differences between modern humans and Neanderthals

Humans have an unusual life history, with an early weaning age, long childhood, late first reproduction, short interbirth intervals, and long lifespan. In contrast, great apes wean later, reproduce earlier, and have longer intervals between births. Despite 80 y of speculation, the origins of these developmental patterns in Homo sapiens remain unknown. Because they record daily growth during formation, teeth provide important insights, revealing that australopithecines and early Homo had more rapid ontogenies than recent humans. Dental development in later Homo species has been intensely debated, most notably the issue of whether Neanderthals and H. sapiens differ. Here we apply synchrotron virtual histology to a geographically and temporally diverse sample of Middle Paleolithic juveniles, including Neanderthals, to assess tooth formation and calculate age at death from dental microstructure. We find that most Neanderthal tooth crowns grew more rapidly than modern human teeth, resulting in significantly faster dental maturation. In contrast, Middle Paleolithic H. sapiens juveniles show greater similarity to recent humans. These findings are consistent with recent cranial and molecular evidence for subtle developmental differences between Neanderthals and H. sapiens. When compared with earlier hominin taxa, both Neanderthals and H. sapiens have extended the duration of dental development. This period of dental immaturity is particularly prolonged in modern humans.

Effects of sublethal concentrations of bifenthrin and deltamethrin on fecundity, growth, and development of the honeybee Apis mellifera ligustica

Bifenthrin and deltamethrin have been widely used as pesticides in agriculture and forestry and are becoming an increasing risk to honeybees. The honeybee, Apis mellifera ligustica, is widely recognized as a beneficial insect of agronomic, ecological, and scientific importance. It is important to understand what effects these chemicals have on bees. Effects of two pesticides at sublethal concentrations on fecundity, growth, and development of honeybees were examined with the feeding method for a three-year period (2006-2008). It was shown that both bifenthrin and deltamethrin significantly reduced bee fecundity, decreased the rate at which bees develop to adulthood, and increased their immature periods. The toxicity of bifenthrin and deltamethrin on workers of Apis mellifera ligustica was also assessed, and the results from the present study showed that the median lethal effects of bifenthrin and deltamethrin were 16.7 and 62.8 mg/L, respectively.

Maternal Effects in Ontogeny and Evolution

Maternal Effects in Mammals is an authoritative volume that provides a comprehensive review of new developments on a topic of importance in evolutionary biology, developmental psychology, and biomedical research. Maternal effects are defined here as effects of the mother’s phenotype on offspring phenotype, separate from the direct effects of genes inherited from the mother. It has been a decade since the publication of Maternal Effects as Adaptations (Mousseau and Fox 1998) brought this topic to the forefront in population biology. This edited volume builds on that earlier work, with a focus on mammals. The features that define the mammalian order, internal gestation, lactation and maternal care, make mammalian mothers particularly good candidates for exhibiting maternal effects on the health and fitness of their offspring. For many mammalian species, these early influences are augmented by an extended period of immaturity and continuing relationships between mothers and offspring into adulthood. As the chapters in this volume demonstrate, maternal effects can be a powerful force influencing individual development and the evolution of populations.

The Expensive Brain: A framework for explaining evolutionary changes in brain size

To explain variation in relative brain size among homoiothermic vertebrates, we propose the Expensive Brain hypothesis as a unifying explanatory framework. It claims that the costs of a relatively large brain must be met by any combination of increased total energy turnover or reduced energy allocation to another expensive function such as digestion, locomotion, or production (growth and reproduction). Focusing on the energetic costs of brain enlargement, a comparative analysis of the largest mammalian sample assembled to date shows that an increase in brain size leads to larger neonates among all mammals and a longer period of immaturity among monotokous precocial species, but not among the polytokous altricial ones, who instead reduce their litter size. Relatively large brained mammals, altricial and precocial, also show reduced annual fertility rates as compared to their smaller brained relatives, but allomaternal energy inputs allow some cooperatively breeding altricial carnivores to produce even more offspring in a shorter time despite having a relatively large brain. Thus, the Expensive Brain framework explains why brain size is linked to life history pace in some, but not all mammalian lineages. This framework encompasses other hypotheses of energetic constraints on brain size variation and is also compatible with the Brain Malnutrition Risk hypothesis, but the absence of a mammal-wide correlation between brain size and immature period argues against the Needing-to-Learn explanation for slower development among large brained mammals.

Novel features of computer-simulated clonal life of Paramecium caudatum

The clone of the ciliated protozoan Paramecium caudatum has the immaturity period of about 60 fissions and the lifespan of about 600 fissions. These life cycle figures have been depicted through laboratory experiments that allow continuous cell divisions for hundreds, which never occur in nature. We here constructed the nature-mimicking model culture that alternated the log- and stationary phases to allow conjugation, and computer-simulated the age structure modifying parameters such as cell distributions to start the culture, fission rates, death rates, immaturity periods, probabilities of conjugation, proportions of transplantation and so on. The average and maximum ages in the culture after thousands of alternations were converged to 43±2 and 140±5 fissions, respectively, when parameters for the immaturity period and the maximum clonal lifespan were set at 60 and 600 fissions. This result explains why cells collected in nature are usually young and vigorous. The average and maximum ages proportionally prolonged as the immaturity period was prolonged, as reported true for species of the ciliate. These results indicate the validity of our simulation. The average and maximum ages remained unchanged when the initial condition for starting the culture was changed from two complementary mating-type cells to a population with a quadratic-function distribution, and when the fission rate at the log-phase and the death rate at the stationary phase were modified for older ages. The average and maximum ages changed slightly when either the conjugation rate or the proportion of transplantation was somewhat lowered. Although they changed considerably when such parameters as the immaturity period, conjugation rate and death rate were extremely modified, no clones with the age over 230 fissions appeared in any simulations. These results indicate the robustness of the model, which provides us with fresh insight into the structural system of the clonal lifespan of P. caudatum in nature.