Acoustic communication and burrow acoustics are reflected in the ear morphology of the coruro (Spalacopus cyanus, Octodontidae), a social fossorial rodent

We studied the middle and inner ears of seven adult coruros (Spalacopus cyanus), subterranean and social rodents from central Chile, using free-hand dissection and routine staining techniques. Middle ear parameters that were focused on here (enlarged bullae and eardrums, ossicles of the "freely mobile type") are believed to enhance hearing sensitivity at lower frequencies. The organ of Corti was of a common mammalian type and revealed three peaks of higher inner hair cell densities. Based on a position frequency map, frequencies were assigned to the respective peaks along the basilar membrane. The first peak at around 300-400 Hz is discussed with respect to the burrow acoustics, while the peak around 10-20 kHz is probably a plesiomorphic feature. The most pronounced peak at around 2 kHz reflects the frequency at which the main energy of vocal communication occurs. The morphology of the ear of the coruro corresponds to the typical pattern seen in subterranean rodents (low frequency and low-sensitivity hearers), yet, at the same time, it also deviates from it in several functionally relevant features.     

Breeding biology of the fossorial rodent Ctenomys talarum (Rodentia: Octodontidae)

The paper describes the breeding biology of the South American herbivorous fossorial rodent Ctenomys talarum (tuco-tuco), covering the following aspects: length of breeding season, prenatal mortality, mean litter size and its correlates, sex ratio and its density-dependence, and late sexual maturity of both sexes. These parameters are compared and contrasted with those of other conspecifics and other subterranean rodents.     

Seasonal acclimation of bank voles and wood mice: nonshivering thermogenesis and thermogenic properties of brown adipose tissue mitochondria

Summary Seasonal acclimation of nonshivering thermogenesis and brown adipose tissue was studied in wild bank voles (Clethrionomys glareolus), yellow necked field mice and wood mice (Apodemus flavicollis, A. sylvaticus). Both, voles and mice increased their capacity for nonshivering thermogenesis during winter. Thermogenic properties of brown fat (cytochrome c oxidase activity, mitochondrial protein content, GDP-binding of brown fat mitochondria) showed similar changes during seasonal acclimation;Clethrionomys andApodemus spp. both showed lowest thermogenic properties in the summer during August, a rapid increase during fall, and highest levels of thermogenic activity in the winter months. With regard to changes in body weight and brown fat mass these species show different strategies for seasonal acclimation. InClethrionomys a reduction of body mass in the winter was found, both in the wild population as well as in individual animals housed in the laboratory.A. flavicollis showed a reduction of body weight during fall, whereasA. sylvaticus maintained a constant body mass throughout the year. Brown fat mass and cellularity increased in theApodemus spp. during winter, in parallel with the thermogenic properties of brown fat, whereas inClethrionomys brown fat mass and cellularity remained seasonally constant. These species live in the same habitat and were trapped in the same area. It is concluded that seasonal improvements of in vivo and in vitro thermogenesis are very similar in these species, although the physiological basis for this improvement is different inClethrionomys andApodemus.Abbreviations BAT brown adipose tissue - BMR basal metabolic rate (resting metabolic rate at thermoneutrality) - BW body weight - COX cytochrome c oxidase - GDP guanosine diphosphate - MP mitochondrial protein - NA noradrenaline - NST nonshivering thermogenesis - NSTcap NST capacity (NST maximum minus BMR) - T _a ambient temperature     

The effects of acclimation on thermal tolerance, desiccation resistance and metabolic rate in Chirodica chalcoptera (Coleoptera: Chrysomelidae)

Despite much focus on species responses to environmental variation through space and time, many higher taxa and geographic areas remain poorly studied. We report the effects of temperature acclimation on thermal tolerance, desiccation rate and metabolic rate for adult Chirodica chalcoptera (Coleoptera: Chrysomelidae) collected from Protea nerifolia inflorescences in the Fynbos Biome in South Africa. After 7 days of acclimation at 12, 19 and 25 degrees C, critical thermal maxima (mean+/-s.e.: 41.8+/-0.2 degrees C in field-fresh beetles) showed less response (<1 degrees C change) to temperature acclimation than did the onset of the critical thermal minima (0.1+/-0.2, 1.0+/-0.2 and 2.3+/-0.2 degrees C, respectively). Freezing was lethal in C. chalcoptera (field-fresh SCP -14.6 degrees C) and these beetles also showed pre-freeze mortality. Survival of 2 h at -10.1 degrees C increased from 20% to 76% after a 2 h pre-exposure to -2 degrees C, indicating rapid cold hardening. Metabolic rate, measured at 25 degrees C and adjusted by ANCOVA for mass variation, did not differ between males and females (2.772+/-0.471 and 2.517+/-0.560 ml CO2 h(-1), respectively), but was higher in 25 degrees C-acclimated beetles relative to the field-fresh and 12 degrees C-acclimated beetles. Body water content and desiccation rate did not differ between males and females and did not respond significantly to acclimation. We place these data in the context of measured inflorescence and ambient temperatures, and predict that climate change for the region could have effects on this species, in turn possibly affecting local ecosystem functioning.     

Impact of developmental temperatures on thermal plasticity and repeatability of metabolic rate

Evolutionary Ecology - Phenotypic plasticity is an important mechanism that allows populations to adjust to changing environments. Early life experiences can have lasting impacts on how individuals...     

Contribution of shivering and nonshivering thermogenesis to thermogenic capacity for the deer mouse (Peromyscus maniculatus)

Small mammals that are active all year must develop ways to survive the cold winters. Endotherms that experience prolonged cold exposure often increase their thermogenic capacity. Thermogenic capacity incorporates basal metabolic rate (BMR), nonshivering thermogenesis (NST), and shivering thermogenesis (ST). Increasing the capacity of any of these components will result in increased thermogenic capacity. It is often thought that NST should be the most plastic component of thermogenic capacity and as such is the most likely to increase with cold acclimation. We used deer mice to test this hypothesis by acclimating 27 animals to one of two temperatures (5 degrees or 22 degrees C) for 8 wk. We then measured and compared values for thermogenic capacity--BMR, ST, and NST--between the two groups. Thermogenic capacity and NST increased by 21% and 42%, respectively, after cold acclimation. Neither BMR nor ST showed any change after acclimation. Therefore, it appears that deer mice raise their thermogenic capacity in response to prolonged cold by altering NST only.     

Two daily melatonin injections differentially induce nonshivering thermogenesis and gonadal regression in the mouse (Peromyscus leucopus)

Female white-footed mice (Peromyscus leucopus) were injected twice daily with 5, 10, 50, 100 micrograms melatonin (MEL) or saline. Injections were given for 7 weeks at 2 and 12 hours after lights-on under a long day (LD 16:8) photoperiod. Afternoon administration of MEL induced gonadal regression, although a dose of 50 micrograms or more was necessary to obtain a maximal response. A 5 micrograms MEL injection in the afternoon resulted in intermediate reproductive tract weights. In white-footed mice a morning MEL injection did not abolish the reproductive regression induced by an afternoon injection. Mice receiving 10, 50 or 100 micrograms MEL daily exhibited increased nonshivering thermogenesis (NST), irrespective of the timing of the injection. Daily injections of 5 micrograms MEL had little effect on NST. These observations suggest that "up and down regulation" of MEL receptors may not be important in P. leucopus. Further, the mechanism by which MEL controls reproduction is different from that for NST.     

Seasonal regulations of resting metabolic rate and thermogenesis in striped hamster (Cricetulus barabensis)

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Resting metabolic rate (RMR), nonshivering thermogenesis (NST) and mitochondria cytochrome c oxydase (COX) activity of brown adipose tissue (BAT), as well as weight of skin and fur were measured in striped hamsters (Cricetulus barabensis) that were live-trapped in the summer, autumn, winter and spring.     

The effect of acute warming and thermal acclimation on maximum heart rate of the common killifish Fundulus heteroclitus

Common killifish Fundulus heteroclitus were acclimated to ecologically relevant temperatures (5, 15 and 33°C) and their maximum heart rate (f_Hmax) was measured at each acclimation temperature during an acute warming protocol. Acclimation to 33°C increased peak f_Hmax by up to 32% and allowed the heart to beat rhythmically at a temperature 10°C higher when compared with acclimation to 5°C. Independent of acclimation temperature, peak f_Hmax occurred about 3°C cooler than the temperature that first produced cardiac arrhythmias. Thus, when compared with previously published values for the critical thermal maximum of F. heteroclitus, the temperature for peak f_Hmax was cooler and the temperature that first produced cardiac arrhythmias was similar to these critical thermal maxima. The considerable thermal plasticity of f_Hmax demonstrated in the present study is entirely consistent with eurythermal ecology of killifish, as shown previously for another eurythermal fish Gillichthys mirabilis.     

Frugal strategy as a base of mole-vole (Ellobius talpinus: Rodentia) adaptations to the fossorial way of life

Interspecies comparison of rodents (Rodentia, Cricetidae) of different ecological specialization has revealed dramatic differences in the most essential physiological life history traits between social fossorial mole vole (Ellobius talpinus) and terrestrial rodents. dwarf hamsters (Phodopus) and voles (Clethrionomys). Mole voles have decreased standard and maximal metabolic rates, reduced ability to maintain constant body temperature. lower rates of growth and sexual maturation, lower reproductive output, declined immune and stress response. These life history traits, shaped by the unique peculiarities of the soil environment, provide effective resource re-allocation towards the costly burrowing activity. Spatial and temporal variability of ecological conditions inevitable for any species additionally participate in re-allocation of internal resources. In cold seasons of the year mole voles increase their metabolic activity and become homeothermic. In the north-eastern periphery of the species range, mole voles are fare more stressed and differ from the individuals inhabit the central part of the range with decreased longevity and increased reproductive output on the level of the entire population.     

Chromosome plasticity in Ctenomys (Rodentia Octodontidae): chromosome 1 evolution and heterochromatin variation

A chromosome 1 (Cr1) pericentric inversion is described in six of seven species in the genus Ctenomys (tuco-tucos) from Uruguay. The inversion was inferred from G-band analyses of subtelocentric Cr1 hypothesised to be derived from the ancestral metacentric condition. Cr1 varies across species in heterochromatin amount and localisation including a metacentric chromosome without positive C-bands in C. torquatus, a subtelocentric chromosome with heterochromatic short arms in C. rionegrensis, and a subtelocentric chromosome negative after C-banding in five of the species analysed here. Pachytene chromosomes from C. rionegrensis, a species with the highest heterochromatin content, and C. torquatus, one of the species with the lowest heterochromatin content, were analysed in order to assess possible mechanisms of heterochromatin evolution. This analysis revealed the presence of three heterochromatic chromocenters in C. rionegrensis where bivalents converge, while in C. torquatus only one chromocenter was observed. In both species, highly repetitive DNA was observed, localised in chromocenters after “in situ” hybridisation. Heterochromatin associated protein M31 was localised in chromocenters of both species after immuno-detection. The spread of heterochromatin in Ctenomys chromosomes could be produced by chromatin exchanges at the chromocenter level. We propose the exchange of this DNA associated proteins between non-homologous chromosomes in pachytene to be the responsible for the spread of heterochromatin through the karyotypes of species like C. rionegrensis     

北小麝鼩的代谢产热和体温调节特征

为探讨食虫目小型哺乳动物的代谢产热和体温调节特征,本文采用封闭式流体压力呼吸仪测定了北小麝鼩在环境温度5 ～ 30℃下的静止代谢率(RMR),结果显示:在环境温度(Ta)为17 5 ～25℃ 的范围内,北小麝鼩的体温基本维持恒定,平均体温为36.55 ± 0.38℃ ;热中性区(TNZ) 为20 ～ 25℃ ;基础代谢率BMR 为5.46 ±0.23 (mLO₂ /g· h),其中环境温度在25℃ 时静止代谢率最低,为4.84 ± 0.39 (mLO₂ /g· h)。在5 ～ 25℃环境温度范围内,热传导值保持稳定;在此温度范围内,北小麝鼩的热传导率(C) 最低,平均为0.42 ± 0.01mLO₂ / (g·h·℃ )。总之,北小麝鼩的产热和体温调节特征为较高的BMR,中等的热传导率,较低的体温和较宽的热中性区。这些特征可能与该物种体型小、夜行性、主要以无脊椎动物为食等生活习性密切相关。     

Cold acclimation increases basal heart rate but decreases its thermal tolerance in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss, Walbaum) were acclimated to 4 degrees C and 17 degrees C for more than 4 weeks and heart rate was determined in the absence and presence of adrenaline to see how thermal adaptation influences basal heart rate and its beta-adrenergic control in a eurythermal fish species. The basal heart rate in vitro was higher in cold-acclimated than warm-acclimated rainbow trout at temperatures below 17 degrees C. On the other hand, adaptation to cold decreased thermal tolerance of heart rate so that the maximal heart rates were achieved at 17 degrees C (75 +/- 4 bpm) and 24 degrees C (88 +/- 2 bpm) in cold-acclimated and warm-acclimated trout, respectively. Beta-adrenergic response of the heart was enhanced by cold-adaptation, since adrenaline (100 nmol l(-1)) caused stronger stimulation of heart rate in cold-acclimated (29 +/- 14%) than in warm-acclimated fish (10 +/- 1%; P = 0.03). Furthermore, adrenaline strongly opposed the temperature-dependent deterioration of force production in cold-acclimated trout but not in warm-acclimated trout. The results indicate that adaptation to cold increases basal heart rate but decreases its thermal tolerance in rainbow trout. Cold acclimation up-regulates the beta-adrenergic system, and beta-adrenoceptor activation seems to provide cardioprotection against high temperatures in the cold-adapted rainbow trout.     

When two equals three: developmental osteology and homology of the caudal skeleton in carangid fishes (Perciformes: Carangidae)

Ontogeny often provides the most compelling evidence for primary homology in evolutionary developmental studies and is critical to interpreting complex structures in a phylogenetic context. As an example of this, we document the ontogenetic development of the caudal skeleton of Caranx crysos by examining a series of cleared and stained larval and postlarval specimens. By studying ontogeny, we are able to more accurately identify some elements of the adult caudal skeleton than is possible when studying the adult stage alone. The presence of two epurals has been used as a synapomorphy of Caranginae (homoplastically present in the scomberoidine genera Scomberoides and Oligoplites). Here we find that three epurals (ep) are present in larvae and small postlarval juveniles (i.e.,<25 mm standard length [SL]) of C. crysos and other carangines, but ep2 never ossifies and does not develop beyond its initial presence. Ep2 was last observed in a 33.6 mm SL specimen as a small nodule of very lightly stained cartilage cells and eventually disappears completely. Therefore, the two epurals present in the adult are ep1 and ep3. In other carangines examined (e.g., Selene, Selar), the rudimentary ep2 ossifies and appears to fuse to the proximal tip of ep1. In these taxa, therefore, the two epurals of the adult appear to be ep1+2 and ep3. We found no indication of three epurals at any stage in the development of Oligoplites (developmental material of Scomberoides was unavailable). We discuss the osteology of the caudal skeleton of carangoid fishes generally and emphasize the power and importance of ontogeny in the identification of primary homology.     

The expression of andromonoecy in Solanum hirtum (Solanaceae): phenotypic plasticity and ontogenetic contingency

Sex expression (the proportions of staminate and hermaphrodite flowers produced) in andromonoecious Solarium hirtum is phenotypically plastic, and there is genetic variation for sex expression plasticity. Changes in sex expression phenotype are inherently the result of altered development. However, the underlying developmental components of sex expression plasticity and of differences in plasticity among genotypes are unknown. This study takes an explicitly genetic and developmental approach to the study of phenotypic plasticity and examines changes in sex expression of ten clonally replicated genotypes at three levels of organization: among inflorescences, within inflorescences, and at the level of developing floral meristems. Changes in sex expression of individuals and differences among individuals are the result of a predictable interplay of resource, architectural, and floral level response within the hierarchical construction of the shoot system. Phenotypic plasticity of whole plant sex expression is ultimately due to sexual lability of individual developing flowers: floral sex is not determined until a primordium size of 9–10 mm. Until that time, sex expression remains labile and developing floral primordia can respond to changes in plant resource status. This flower level developmental lability, however, is expressed within the constraints set by the architecture and ontogenetic history of the organism. Only those floral primordia produced in distal portions of each inflorescence are labile, capable of developing into either a staminate or hermaphrodite flower, whereas those primordia in basal positions invariably develop as hermaphrodite flowers. The genotypes differ with respect to the architectural components of phenotypic plasticity and it is this architectural variation that results in differences in plasticity among genotypes. The phenomenon, in which the developmental fate of a primordium depends upon where and when it is produced within the architecture of an organism and what events have preceded it during ontogeny, can be termed “ontogenetic contingency.”