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1.
Progenesis is considered to have an important role in evolution because it allows the retention of both a larval body size and shape in an adult morphology. However, the cost caused by the adoption of a progenetic process in both males and females remains to be explored to explain the success of progenesis and particularly its biased prevalence across the sexes and environments. Here, through an experimental approach, we used a facultative progenetic species, the palmate newt (Lissotriton helveticus) that can either mature at a small size and retain gills or mature after metamorphosis, to test three hypotheses for sex‐specific pay‐offs of progenesis in safe versus risky habitats. Goldfish were used because they caused a higher decline in progenetic than metamorphic newts. We determined that progenetic newts have a lower reproductive fitness than metamorphic newts. We also found that, when compared to metamorphs, progenetic males have lower reproductive activity than progenetic females and that predatory risk affects more progenetic than metamorphic newts. By identifying ultimate causes of the female‐biased sex ratios found in nature, these results support the male escape hypothesis, that is the higher metamorphosis rate of progenetic males. They also highlight that although progenesis is advantageous in advancing the age at first reproduction, it also brings an immediate fitness cost and this, particularly, in hostile predatory environments. This means that whereas some environmental constraints could favour facultative progenesis, some others, such as predation, can ultimately counter‐select progenesis. Altogether, these results improve our understanding of how developmental processes can affect the sexes differently and how species invasions can impair the success of alternative developmental phenotypes. 相似文献
2.
Denoël M Joly P Whiteman HH 《Biological reviews of the Cambridge Philosophical Society》2005,80(4):663-671
Facultative paedomorphosis is an environmentally induced polymorphism that results in the coexistence of mature, gilled, and fully aquatic paedomorphic adults and transformed, terrestrial, metamorphic adults in the same population. This polymorphism has been of interest to scientists for decades because it occurs in a large number of caudate amphibian taxa as well as in a large diversity of habitats. Numerous experimental and observational studies have been conducted to explain the proximate and ultimate factors affecting these heterochronic variants in natural populations. The production of each alternative phenotype is based on a genotypexenvironment interaction and research suggests that differences in the environment can produce paedomorphs through several ontogenetic pathways. No single advantage accounts for the maintenance of this polymorphism. Rather, the interplay of different costs and benefits explains the success of the polyphenism across variable environments. Facultative paedomorphosis allows individuals to cope with habitat variation, to take advantage of environmental heterogeneity in the presence of open niches, and to increase their fitness. This process is expected to constitute a first step towards speciation events, and is also an example of biodiversity at the intraspecific level. The facultative paedomorphosis system is thus ripe for future studies encompassing ecology, evolution, behaviour, endocrinology, physiology, and conservation biology. Few other systems have been broad enough to provide varied research opportunities on topics as diverse as phenotypic plasticity, speciation, mating behaviour, and hormonal regulation of morphology. Further research on facultative paedomorphosis will provide needed insight into these and other important questions facing biologists. 相似文献
3.
Adaptive significance of facultative paedomorphosis in Triturus alpestris (Amphibia, Caudata): resource partitioning in an alpine lake 总被引：1，自引：0，他引：1
1. Facultative paedomorphosis is a polymorphism that has important evolutionary implications in promoting morphological differentiation and variation in habitat use. It occurs in several urodele species throughout the world. Several hypotheses based on life-history theory have been proposed to explain the wide range of habitats in which facultative paedomorphosis occurs, suggesting multifactorial causes.
2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro-habitat use and diet of two coexisting morphs in an alpine lake.
3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.
4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.
5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear. 相似文献
2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro-habitat use and diet of two coexisting morphs in an alpine lake.
3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.
4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.
5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear. 相似文献
4.
Susan B. Roberts 《Obesity (Silver Spring, Md.)》1995,3(Z2):155s-163s
The role of energy expenditure in the development of obesity remains unclear. This issue is examined using data from prospective studies of energy expenditure and obesity, the effects of overfeeding and diet composition on energy expenditure, and studies of the relationship between energy expenditure for physical activity and body composition. The combined results from these investigations strongly support the view that low energy expenditure can facilitate rapid weight gain in susceptible individuals. It is speculated that, in susceptible individuals, low energy expenditure for resting energy expenditure as well as physical activity are part of a range of mechanisms available for providing surplus energy for rapid weight gain. In addition, both cross-sectional and intervention studies indicate that there is an equilibration between the level of energy expenditure for physical activity and body fat content. While genetic and other factors clearly play an important role in this relationship, it appears that a modest reduction in body fat content can be achieved by increasing energy expenditure for physical activity in physical exercise programs. 相似文献
5.
Muricid gastropod radulae are more complex than those of most other neogastropods, especially in the number and variety of cusps, denticles, and interlocking mechanisms. How this complexity evolved, however, is unknown. Morphological gaps between higher taxa within the Muricidae are substantial, and there are few unambiguous intermediates. Here, we use developmental data from the Patagonian trophonine muricid Trophon geversianus to investigate the evolution of an unusual condition in which there are two marginal cusps at each end of each central rachidian tooth, rather than one or none as in most muricids. Trophon geversianus begins ontogeny with one marginal cusp (the inner marginal cusp), but a second (the outer marginal cusp) appears later, arising from separation of the rachidian base edge from the radular membrane rather than through bifurcation or lateral migration of pre‐existing cusps. Truncation of development (i.e., paedomorphosis) at this second developmental phase in a trophonine ancestor provides an explanation for the lack of transitional forms between most adult trophonine muricids, which have the plesiomorphic condition of one marginal cusp, and sister group ocenebrine muricids, which have the derived condition of two marginal cusps. 相似文献
6.
Over the past four decades, as the use of the term condition has become more frequent, the meaning of the term has become increasingly vague. This is especially true in evolutionary theory where condition is now equated with reproductive value, genetic quality, or defined as the ‘total pool of resources available for reproduction.’ Condition with the latter meaning is essentially impossible to measure empirically because it is associated with multiple attributes, such as nutritional state, health, experience, foraging success, ability to cope with environmental pressures, and social status, that collectively affect individual fitness. The addition of qualifying terms that often precede condition (e.g., phenotypic, energetic, and nutritional) and the usage of terms that describe an individual's state (e.g., physiological state, energetic state, and nutritional state) add confusion to the issue. It is therefore important to evaluate the meaning of condition, the limits of its usefulness, and how it can be best measured. We suggest using a more narrow definition of condition, amenable to empirical study, would benefit evolutionary and behavioral studies. 相似文献
7.
Organismic diversity, as well as distributional and ecological patterns, can be fully understood in an evolutionary framework only. Reliable phylogenetic trees are required to ‘read history’, but are not yet available for most marine invertebrate groups. Molecular systematics offers an enormous potential, but still fails for ‘all‐species approaches’ on groups with species that are rare or occur in remote areas only, simply because there is no easily collectable material available for sequence analyses. Exploring morphologically aberrant corambid nudibranch gastropods as a case study, we assess whether or not morphology‐based phylogenetic analyses can fill this gap and produce a tree that allows a detailed view on evolutionary history. Morphology‐based parsimony analysis of corambids and potential relatives resulted in a well‐resolved and remarkably robust topology. As an offshoot of kelp‐associated onchidoridid ancestors, and obviously driven by the heterochronic shortening of life cycles and morphological juvenilization in an ephemeral habitat, the ancestor of corambids originated in cool northern Pacific coastal waters. A basal clade (the genus Loy) diverged there, adapting to live on soft bottoms under successive reversals of paedomorphic traits. The more speciose Corambe lineage radiated preying upon short‐lived encrusting bryozoa in a high‐energy kelp environment. Selection favoured transformation of the mantle into a cuticle‐covered shield, and successive paedomorphic translocations of dorid anal gills to the protected ventral side of the body, where compensatory, multiple gills evolved. Corambe species probably first colonized tropical American seas, and then radiated in worldwide temperate waters: this is explained by the excellent long‐distance dispersal abilities afforded by rafting on kelp, with the subsequent divergence of colonizers in allopatry. The competitive coexistence of Corambe pacifica MacFarland & O'Donoghue, 1929 and Corambe steinbergae (Lance, 1962) off California is the result of independent colonization events. The closing of the Isthmus of Panama separated the latter species from a flock that have radiated within warm Atlantic waters since then. Our case study shows that morphological structures, if investigated in depth, bear the potential for an efficient phylogenetic analysis of groups that are still elusive to molecular analyses. Tracing character evolution and integrating a wide range of geographic, biological, and ecological background information allowed us to reconstruct an evolutionary scenario for corambids that is detailed and plausible, and can be tested by future molecular approaches. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163 , 585–604. 相似文献
8.
Many animals rely on fat reserves, to keep them alive through extended periods of food shortage, such as the winter, and to provide additional energy for reproduction. Fat reserves, measured relative to an animal's size, are often referred to as the animal's body condition. The present study investigated how different levels of grazing by domestic stock in native grassland habitat affect the body condition of the pygmy bluetongue lizard (Tiliqua adelaidensis), and if these effects are related to changes in the abundance and size of grasshoppers which are the lizards primary source of food. The initial hypothesis was that lizards would have the highest body condition in moderately grazed paddocks, because those paddocks would have more grasshoppers than heavily grazed paddocks, and better visual conditions for lizards to catch those grasshoppers than in ungrazed paddocks. The results, however, showed that both lizard body condition and the abundance of grasshoppers increased with decreasing grazing intensity. The connection between lizard body condition and abundance of grasshoppers was complex. Within an activity season, lizard body condition generally declined from spring to summer, while the number of grasshoppers grew. The mean size of grasshoppers seemed to be more important, as lizard body condition was higher in spring, the time of year with the largest grasshoppers. These results show that the intensity of grazing by domestic stock influences the body condition of pygmy bluetongue lizards, but that this effect is not entirely due to the reduction in the number of grasshoppers resulting from grazing. 相似文献
9.
D. Fredrik K. Söderblom Alejandro Blanco Albert Prieto-Márquez Nicolás E. Campione 《Palaeontology》2023,66(5):e12674
The near-global distribution of hadrosaurid dinosaurs during the Cretaceous has been attributed to mastication, a behaviour commonly recognized as a mammalian adaptation. Its occurrence in a non-mammalian lineage should be accompanied by the evolution of several morphological modifications associated with food acquisition and processing. This study investigated morphological variation in the dentary, a major element of the hadrosauroid lower jaw. Eighty-four hadrosauroid dentaries were subjected to geometric morphometric and statistical analyses to investigate their taxonomic, ontogenetic, and individual variation. Results suggest increased food acquisition and processing efficiency in saurolophids through a complex pattern of evolutionary and growth-related changes. The edentulous region grew longer relative to dentary length, allowing for food acquisition specialization anteriorly and processing posteriorly, and became ventrally directed, possibly associated with foraging low-growing vegetation, especially in younger individuals. The saurolophid coronoid process became anteriorly directed and relatively more elongate, with an expanded apex, increasing moment arm length, with muscles pulling the jaw more posteriorly, increasing mechanical advantage. During growth, all hadrosauroids underwent anteroposterior dental battery elongation by the addition of teeth, and edentulous region ventralization decreased. The dental battery became deeper in saurolophids by increasing the number of teeth per tooth family. The increased coronoid process anterior inclination and relative edentulous region elongation in saurolophids are hypothesized to have evolved through hypermorphosis and/or acceleration, peramorphic heterochronic processes; the development of an anteroposteriorly shorter but dorsoventrally taller saurolophid dentary, is probably due to post-displacement in dental battery elongation and edentulous region decreased ventral orientation, a paedomorphic heterochronic process. 相似文献
10.
Heterochrony, as a means of evolution in which the rate or timing of developmental events of the descendant is altered compared with that of the ancestor, is of significance because it suggests that rapid and dramatic morphological changes are possible with few genetic changes. The putative origin of plant taxa by this means of evolution is becoming increasingly frequent in the literature but there is little evidence of the extent of the genetic change necessary to alter the timing of developmental events to produce such changes. This study shows that the onset of flowering can be altered independently from the vegetative transition in leaf form in at least one genotype of Pisum in response to different environments. Further, it identifies 9 mutations that act in a heterochronic manner to produce dramatic morphological changes that can be described as progenesis, neoteny, hypermorphosis or acceleration. In addition, it is demonstrated that the same heterochronic process (e.g. progenesis) may be caused by genes controlling distinctly different physiological processes. It is suggested that Pisum is an ideal model species for studies of heterochrony and that few genetic changes are necessary to bring about dramatic heterochronic changes. 相似文献
11.
Food intake rate has previously been derived from observation of eating behavior in laboratory settings or in public eating establishments. Although it has been suggested that obese individuals eat faster than lean individuals, observations of such an “obese eating style” have yielded mixed results. In the present study, the relationship between ad-libitum food intake rate and obesity was evaluated over 4 days on a metabolic ward in 28 healthy Pima Indian men (Mean ± SD; 29 ± 7 y, 100.4 ± 27.1 kg, 33 ± 10% body fat) using an automated food selection system containing a large variety of foods . Total energy intake averaged 18829 ± 3299 kJ/d consisting of 47 ± 4,40 ± 3, and 13 ± 1 percent of carbohydrate, fat and protein, respectively. The average meal duration was 25 ± 7 min. Food intake rate was 68 ± 21 g/min while carbohydrate, fat and protein intake rates were 23 ± 6, 9 ± 3 and 6 ± 2 g/min, respectively. Food intake rate correlated negatively with %body fat (1=0.61, P<0.01). Similar relationships were found between the intake rates of carbohydrate, fat and protein and body fatness. Only prospective studies will indicate whether a slow food intake rate may contribute to the etiology of obesity by possibly reducing satiety . 相似文献
12.
Janine M. Ziermann Alice M. Clement Rolf Ericsson Lennart Olsson 《Journal of morphology》2018,279(4):494-516
Lungfishes are the extant sister group of tetrapods. As such, they are important for the study of evolutionary processes involved in the water to land transition of vertebrates. The evolution of a true neck, that is, the complete separation of the pectoral girdle from the cranium, is one of the most intriguing morphological transitions known among vertebrates. Other salient changes involve new adaptations for terrestrial feeding, which involves both the cranium and its associated musculature. Historically, the cranium has been extensively investigated, but the development of the cranial muscles much less so. Here, we present a detailed study of cephalic muscle development in the Australian lungfish, Neoceratodus forsteri, which is considered to be the sister taxon to all other extant lungfishes. Neoceratodus shows several developmental patterns previously described in other taxa; the tendency of muscles to develop from anterior to posterior, from their region of origin toward insertion, and from lateral to ventral/medial (outside‐in), at least in the branchial arches. The m.protractor pectoralis appears to develop as an extension of the most posterior m.levatores arcuum branchialium, supporting the hypothesis that the m.cucullaris and its derivatives (protractor pectoralis, levatores arcuum branchialium) are branchial muscles. We present a new hypothesis regarding the homology of the ventral branchial arch muscles (subarcualis recti and obliqui, transversi ventrales) in lungfishes and amphibians. Moreover, the morphology and development of the cephalic muscles confirms that extant lungfishes are neotenic and have been strongly influenced via paedomorphosis during their evolutionary history. 相似文献
13.
Lorraine Ghibaudi John Cook Constance Farley Margaret van Heek Joyce J. Hwa 《Obesity (Silver Spring, Md.)》2002,10(9):956-963
Objective: Childhood obesity is an emerging health problem. This study assesses the effects of three levels of dietary fat (10%, 32%, and 45% measured by kilocalories) on weight gain, body composition, energy metabolism, and comorbidity factors in rats from weaning through maturation. Research Methods and Procedures: The role of dietary fat on the susceptibility to obesity was assessed by feeding diets containing three levels of dietary fat to rats from weaning through 7 months of age. Body composition was analyzed by DXA after 6 and 12 weeks of dietary treatment. Energy metabolism was measured by indirect calorimetry. Results: Energy intake, weight gain, fat mass, and plasma glucose, cholesterol, triglyceride, free fatty acid, leptin, and insulin levels increased dose‐dependently with increased dietary fat. No difference in absolute lean mass among the three groups was observed. Therefore, the differences in weight gain are accounted for primarily by increased fat accretion. Compared with rats that were relatively resistant to obesity when on a 45% fat diet, diet‐induced obesity‐prone rats were in positive energy balance and had an elevated respiratory quotient, indicating a switch in energy substrate use from fat to carbohydrate, which promotes body‐fat accretion. Discussion: Our data support the hypothesis that administration of increasing amount of dietary fat to very young rats enhances susceptibility to diet‐induced obesity and its comorbidities. 相似文献
14.
HOWARD H. WHITEMAN RAYMOND D. SEMLITSCH 《Biological journal of the Linnean Society. Linnean Society of London》2005,86(2):265-281
The study of reproductive isolation (RI) as a prerequisite to sympatric speciation has been limited by a focus on species that have already experienced isolation. However, a complete understanding of speciation depends on observing taxa before they complete the speciation process. We estimated RI in field populations of the polyphenic mole salamander, Ambystoma talpoideum, by capturing paedomorphic (aquatic) and metamorphic (terrestrial) adults during the breeding season from two natural populations. We found evidence for asymmetric RI between morphs, such that paedomorphic males and metamorphic females had functionally zero RI, whereas metamorphic males and paedomorphic females had substantial RI. Evidence suggests that ecological factors such as the abundance of each morph, timing of rainfall, and water depth of the breeding habitat play a large role in the production of these asymmetries. Spatial aspects of RI had a greater relative impact on overall isolation than temporal differences, in part because metamorphic adults were often captured in shallower water than paedomorphic adults. However, morph separation varied across populations and year, suggesting that environmental heterogeneity likely plays a large role in the potential for RI, particularly between metamorphic males and paedomorphic females. In addition, body‐size variation and behavioural differences could also influence the RI estimates presented here. Although facultative paedomorphosis appears to have played a large role in macroevolutionary change via allopatric speciation in some taxa, our results suggest that there is little potential for sympatric speciation in the future within these populations. However, asymmetric RI creates the opportunity for fitness differences between morphs and sexes that would directly affect the maintenance of this polymorphism. Our results suggest that further studies on this and other polyphenisms may provide valuable insight into the evolution of RI and the role of environmental heterogeneity in the production and maintenance of biological diversity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 265?281. 相似文献
15.
栖息地丧失和退化严重威胁全球两栖类动物的生存与繁衍,栖息地保护在两栖动物保育中具有高的优先性。大凉螈(Liangshantriton taliangensis)是国内外广泛关注的横断山区特有珍稀有尾类物种。结合大凉螈33个分布位点和9个环境变量数据,本文运用最大熵(MaxEnt)模型预测了大凉螈当前潜在适宜分布区,再根据现有自然保护地(5个国家级和9个省级)分布进行了保护空缺分析,同时,借助比例体重指数法(SMI)衡量了7个种群共218个个体的身体状况,比较了保护区内外种群间的差异,利用归一化植被指数(NDVI)识别了保护区内植被变化,据此对四川栗子坪国家级自然保护区的保护成效进行了评估。结果表明,(1)影响大凉螈分布的最主要环境变量为NDVI(贡献值34.33%)、最干月份降水量(贡献值26.81%)和海拔(贡献值20.92%);(2)大凉螈适宜生境主要集中在小相岭和凉山山系,占研究区域总面积的15.38%,现有自然保护地覆盖了大凉螈23.62%的适宜生境,仍有3760.91km2的保护空缺;(3)栗子坪保护区内雄性个体肥满度指数显著大于保护区外个体(t-tes... 相似文献
16.
Secondary sexual traits may evolve under the antagonistic context of sexual and natural selection. In some polymorphic species, these traits are only expressed during the breeding period and are differently expressed in alternative phenotypes. However, it is unknown whether such phenotypes exhibit phenotypic plasticity of seasonal ornamentations in response to environmental pressures such as in the presence of fish (predation risk). This is an important question to understand the evolution of polyphenisms. We used facultative paedomorphosis in newts as a model system because it involves the coexistence of paedomorphs that retain gills in the adult stage with metamorphs that have undergone metamorphosis, but also because newts exhibit seasonal sexual traits. Our aim was therefore to determine the influence of fish on the development of seasonal ornamentation in the two phenotypes of the palmate newt (Lissotriton helveticus). During the entire newt breeding period, we assessed the importance of phenotype and fish presence with an information‐theoretic approach. Our results showed that paedomorphs presented much less developed ornamentation than metamorphs and those ornamentations varied over time. Fish inhibited the development of sexual traits but differently between phenotypes: in contrast to metamorphs, paedomorphs lack the phenotypic plasticity of sexual traits to environmental risk. This study points out that internal and external parameters act in complex ways in the expression of seasonal sexual ornamentations and that similar environmental pressure can induce a contrasted evolution in alternative phenotypes. 相似文献
17.
Lovejoy NR 《Evolution; international journal of organic evolution》2000,54(4):1349-1362
Abstract. As needlefishes (Belonidae) grow, their jaws pass through a \"halfbeak\" stage that resembles the adult jaw condition of the closely related family of halfbeaks (Hemiramphidae). Based on this pattern, some authors have suggested that halfbeaks are \"developmentally arrested\" or paedomorphic needlefish derivatives, whereas others have supported the notion that needlefishes are descended from halfbeak-like ancestors and that needlefish ontogeny thereby recapitulates phylogeny. To test these ideas and to better understand evolutionary changes in jaw ontogeny, phylogenetic relationships among genera of needlefishes, sauries (Scomberesocidae), halfbeaks, and flyingfishes (Exocoetidae) were assessed using mitochondrial (cytochrome b and 16S), nuclear (Tmo-4C4), and morphological characters. The resultant tree provides several novel taxonomic findings: (1) flyingfishes appear to be nested within halfbeaks; (2) sauries appear to be nested within needlefishes; and (3) the Indo-West Pacific freshwater halfbeaks appear to be most closely related to the needlefish/saury clade. The structure of the tree falsifies the idea that halfbeaks are paedomorphic needlefishes. Instead, halfbeaks are basal relative to needlefishes, fitting the pattern predicted by the hypothesis of recapitulation. I discuss limitations to phylogenetic perspectives on recapitulation based on discrete character data by comparing aspects of von Baerian and Haeckelian views of the relation between ontogeny and phylogeny. 相似文献
18.
LEBEL, CARL, AMY BOURDEAU, DAVID LAU, AND PAMELA HUNT. Biologic response to peripheral and central administration of recombinant human leptin in dogs. Obes Res. Objective: Because leptin is believed to act within the central nervous system, the objective of this study was to test that presumption by comparing the biologic responses to recombinant human leptin (rHuLeptin) when delivered either subcutaneously or intrathecally in a large animal species, the beagle dog. Methods and Procedures: Adult beagle dogs were used for all studies (n = 3 to 14). Treatment with rHuLeptin was either as daily subcutaneous or intermittent intrathecal injections. Results: Subcutaneously administered rHuLeptin was absorbed with peak concentrations appearing at 2 to 4 hours. After intrathecal administration, cerebral spinal fluid concentrations declined in a bi-phasic manner with a terminal half-life of ?6 to 8 hours. When lean beagles were given leptin subcutaneously, at 0. 05 to 5 gkglday for up to 6 months, reductions in body weight (up to 30%) and food intake (up to 75%) were observed. Body fat loss was observed in both lean and obese dogs, and confirmed by dual energy X-ray absorptiometry and histology of adipose tissue. When rHuleptin was delivered intrathecally at 4 to 1000 μg/dose for up to 3 months, the primary effects observed were reductions in body weight and food intake. In general all findings reported in the intrathecal studies were consistent with those noted in the subcutaneous studies; however, the required intrathecal dose was substantially lower than that for subcutaneous delivery. Discussion: These studies demonstrate that both subcutaneous and intrathecal treatment of rHuLeptin was associated with effects on body weight, food intake, and body fat in dogs. These results support the concept that the central nervous system is the probable primary site of action for leptin and suggest that rHuLeptin has similar physiologic activities that influence body weight, body fat, and metabolism in large animals to those reported previously in rodents. 相似文献
19.
The purpose of this study was to test whether serum testosterone (T) concentrations characteristic of reproductively active, long-day-housed Siberian hamsters are necessary for compensatory increases in nonexcised fat pads following removal of epididy-mal white adipose tissue (EWAT) and/or for the maintenance of seasonally appropriate body weights in these hamsters. Long-day-housed hamsters were castrated or left intact, sham or EWAT lipectomized, and given T or cholesterol (C) implants. All groups had ad libitum food access except for two castrated T-treated groups that were pair-fed to their C-treat-ed counterparts to control for effects of T on food intake. C-treated castrates had decreased body weights compared with all other groups, suggesting a role of T in the maintenance of seasonally appropriate body mass. Since the T-treated hamsters pair-fed to these T-deficient animals exhibited seasonally appropriate body weights and fat pad masses, T does not appear to affect these parameters through the modulation of food intake. All fat pads of C-treated animals were smaller than those of ad libitum- or pair-fed, T-treated castrates; however, EWAT was the only fat pad that was smaller in the C-treated sham-lipectomized group than in gonad-intact sham-lipectomized hamsters. This result may indicate an enhanced sensitivity of EWAT to T. The effects of T on fat pad mass were not associated with proportionate changes in lipoprotein lipase activity, suggesting that the major effect of T on fat accumulation occurs through other mechanisms in this species. C-treated lipectomized hamsters compensated for the body fat deficit 8 weeks after lipectomy via statistically nonsignificant increases in retroperitoneal and inguinal WAT mass. This finding suggests that, whereas T is necessary for maintenance of seasonally-appropriate body weight, it is not necessary for fat pad compensation after EWAT lipectomy. 相似文献
20.
Hastings PA 《Evolution; international journal of organic evolution》2002,56(8):1644-1654
Comparison of ontogenetic trajectories with those inferred for ancestors provides a powerful but underused tool for the study of the evolution of different types of phenotypic characters. This approach was used to study morphological and behavioral evolution of the highly dimorphic chaenopsid genus Coralliozetus (Teleostei: Blennioidei). All sexually dimorphic synapomorphies of Coralliozetus involved evolution in females only; one character evolved via terminal addition (peramorphosis), whereas six evolved via terminal deletion (paedomorphosis). Evolution of the ontogeny of two behavioral characters (microhabitat use and feeding rate), as inferred by focal animal observations of eight species of tube blennies, was also confined to females and conformed to terminal deletion. Both sexes of outgroups and males of all species of Coralliozetus exhibit an ontogenetic shift from the open as juveniles to shelters as adults. However, females of all species of Coralliozetus retain the juvenile behavior of residing in the open. Blennies residing in the open take significantly more feeding bites than conspecifics residing in shelters, consequently, female Coralliozetus retain the high feeding rate of juveniles. Several of the paedomorphic morphological features of Coralliozetus females are plausibly associated with their paedomorphosis in microhabitat use. These include their reduced conspicuousness and reduced robustness compared to conspecific males. In groups such as chaenopsids, which undergo significant ontogenetic changes in microhabitat, paedomorphosis provides a mechanism for rapid coevolution of behavior and morphology. This study, the first to document the evolution of sexual dimorphism via both behavioral and morphological paedomorphosis, demonstrates the unique insights to be gained from a multidimensional analysis of phenotypic evolution. 相似文献