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排序方式: 共有171条查询结果,搜索用时 15 毫秒
1.
Sinlan Poo Ana Karen Candia Kristina L. Cohen Francesca T. Erickson Sara A. Mason Bradley D. Nissen Adair F. McNear Jonathon J. Reinig Joseph S. Sherrock Ashley R. Aguiluz Letitia L. Jacques Hanna E. R. Jenkins Anne Devan-Song 《Biotropica》2023,55(4):806-815
Environmentally cued hatching has been well-documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub-Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence-induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade-off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding-induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg-stage threats may be an indicator of species' ability to flexibly navigate a changing environment. 相似文献
2.
We have previously reported that the isolated frog corneal epithelium (a Cl–-secreting epithelium) has a large diffusional water permeability (Pdw 1.8×10–4 cm/s). We now report that the presence of Cl– in the apical-side bathing solution increases the diffusional water flux, Jdw (in both directions) by 63% from 11.3 to 18.4 l min–1 · cm–2 with 60 mm [Cl] exerting the maximum effect. The presence of Cl– in the basolateral-side bathing solution had no effect on the water flux. In Cl–-free solutions amphotericin B increased Jdw by 29% but only by 3% in Cl–-rich apical-side bathing solution, suggesting that in Cl–-rich apical side bathing solution, the apical barrier is no longer rate limiting. Apical Br– (75 mm) also increased Jdw by 68%. The effect of Cl– on Jdw was observed within 1 min after its addition to the apicalside bathing solution. HgCl2 (0.5 mm) reduced the Cl–-increased Pdw by 31%. The osmotic permeability (Pf) was also measured under an osmotic gradient yielding values of 0.34 and 2.88 (x 10–3 cm/s) in Cl–-free and Cl–-rich apical-side bathing solutions respectively. It seems that apical Cl–, or Cl– secretion into the apical bath could activate normally present but inactive water channels. In the absence of Cl–, water permeability of the apical membrane seems to be limited to the permeability of the lipid bilayer.This work was supported by National Eye Institute grants EY-00160 and EY-01867. 相似文献
3.
Summary Transepithelial Li+ influx was studied in the isolated epithelium from abdominal skin ofRana catesbeiana. With Na+-Ringer's as inside medium and Li+-Ringer's as outside medium, the Li+ influx across the epithelium was 15.6 A/cm2. This influx was considerably reduced by removal of either Na+ or K+ from the inside bath or by the addition of ouabain or amiloride. Epithelial K+ or Na+ concentration was respectively lower in epithelia bathed in K+-free Ringer's or Na+-free Ringer's. In conditions of negligible Na+ transport, a 20mm Li+ gradient (outin) produced across the short-circuited epithelium a Li+ influx of 11.8 A/cm2 and a mean short-circuit current of 10.2 A/cm2. The same Li+ gradient in the opposite direction produced a Li+ outflux of only 1.9 A/cm2. With equal Li+ concentration (10.3 and 20.6mm) on both sides of the epithelium, plus Na+ in the inside solution only, a stable Li+-dependent short-circuit current was observed. Net Li+ movement (outin) was also indirectly determined in the presence of an opposing Li+ gradient. Although Li+ does not substitute for Na+ as an activator of the (Na++K+)-ATPase from frog skin epithelium, Li+ influx appears to be related to Na+–K+ pump activity. It is proposed that the permeability of the outer barrier to Na+ and Li+ is regulated by the electrical gradient produced by electrogenic Na+–K+ pumps located in the membrane of the deeper epithelial cells. 相似文献
4.
Regular sea–urchins, as a rule, prepare and process their food as pellets in their buccal cavity before ingesting them. This is obtained through the synergistic interaction of the five teeth with five fleshy protuberances (paradental tongues) which extend into the oral cavity and work like tongues. Each of these structures consists of two anatomically distinct parts: the outer component is a deep pouch of the terminal tract of the pharynx and shows a histological organization similar to that usually shown by the pharyngeal wall itself. The deeper component (paradental axis) is represented by a supporting rod and shows a peculiar histological structure, which consists of glycogen containing vesiculate cells mixed to slim muscle fibres and held together by a thin fibrillar stroma. The paradental axes are very problematic structures in terms of comparative anatomy and phylogenetic aspects. Their microscopic and submicroscopic organization is unusual for an echinoderm and recalls that of different types of chordoid organs commonly found in other invertebrates (Protostomata and Deuterostomata). 相似文献
5.
Antonio de Candia Alessandro Sarracino Ilenia Apicella Lucilla de Arcangelis 《PLoS computational biology》2021,17(8)
Spontaneous brain activity is characterized by bursts and avalanche-like dynamics, with scale-free features typical of critical behaviour. The stochastic version of the celebrated Wilson-Cowan model has been widely studied as a system of spiking neurons reproducing non-trivial features of the neural activity, from avalanche dynamics to oscillatory behaviours. However, to what extent such phenomena are related to the presence of a genuine critical point remains elusive. Here we address this central issue, providing analytical results in the linear approximation and extensive numerical analysis. In particular, we present results supporting the existence of a bona fide critical point, where a second-order-like phase transition occurs, characterized by scale-free avalanche dynamics, scaling with the system size and a diverging relaxation time-scale. Moreover, our study shows that the observed critical behaviour falls within the universality class of the mean-field branching process, where the exponents of the avalanche size and duration distributions are, respectively, 3/2 and 2. We also provide an accurate analysis of the system behaviour as a function of the total number of neurons, focusing on the time correlation functions of the firing rate in a wide range of the parameter space. 相似文献
6.
González Mariela Montoya Rolando Candia Arturo Gómez Patricia Cisternas Manuel 《Hydrobiologia》1996,326(1):229-234
The extreme phenotypic variability recognized among the species of Gracilaria has highlighted the need for the application of refined methods to help solve taxa identifications. In Chile, there still exists uncertainty about the exact number of Gracilaria species. Our investigations are centered on DNA analyses of morphotypes collected from different geographical locations, namely Lenga and Isla Santa María, Region VIII (36°00 S to 38°00 S), and Maullín, Region X (39°30 S to 43°40 S). These two regions of Chile are considered as areas of confluence of G. chilensis, G. verrucosa, and a species of Gracilariopsis. In this study four morphotypes, from a natural bed located in Maullín, were analyzed for RFLP of plastid DNA and the results compared with data of four morphotypes from a bed in Lenga. The DNA banding patterns from each enzyme digest were identical irrespective of morphotypes and/or locations. In an attempt to unravel the nature of the morphological differences found among Lenga and Maullín morphotypes, RAPD analyses of nuclear DNA were also performed; however, no polymorphism has been found yet. Therefore, the data of this study, as well as concurrent data from preliminary interfertility tests, suggest that all morphotypes belong to a single taxon, Gracilaria chilensis.Departamento de Botánica, Facultad de Ciencias Naturales y Oceanográficas 相似文献
7.
8.
Patruno M McGonnell I Graham A Beesley P Candia Carnevali MD Thorndyke M 《Proceedings. Biological sciences / The Royal Society》2003,270(1522):1341-1347
Invertebrates have frequently been used to help understand the complexities of regulatory gene function and evolution. The bone morphogenetic proteins (BMPs) are a highly conserved group of secreted regulatory factors that play an important part in early embryonic patterning. In the present study we have used the remarkable regenerative potential of crinoid echinoderms to explore the BMPs' site of expression in an adult developmental programme. Our results suggest that a crinoid BMP2/4 homologue is actively involved during the early stages of blastemal regeneration at a time when fundamental patterns are being established. This supports the idea of an evolutionary developmental programme where essential gene families are conserved throughout phylogeny in terms of both expression and function. 相似文献
9.
Changes in Ubiquitin Conjugates and Hsp72 Levels During Arm Regeneration in Echinoderms 总被引:1,自引:0,他引:1
Patruno M Thorndyke MC Candia Carnevali MD Bonasoro F Beesley P 《Marine biotechnology (New York, N.Y.)》2001,3(1):4-15
All organisms show a common defensive mechanism that results in the expression of conserved heat shock proteins (Hsps). These
proteins function in a wide range of stressful conditions. We have monitored their levels in species of regenerating echinoderms
with different mechanisms of regeneration and from different geographical locations. The effect of an artificial higher temperature
on expression of Hsps was also studied. Two stress proteins (Hsp72 and ubiquitin) that are important in processes such as
development and protein degradation were investigated. Using Western blot analysis and immunocytochemistry, we found significant
changes in the level (Hsp72) and pattern of conjugation (ubiquitin) that corresponded with the repair phase (early regenerative
stages) and with the later growth and regeneration of new tissues. Animals from the intertidal environment showed a distinctly
sustained expression pattern of Hsp72 compared with benthic animals which suggests a functionally adaptative and dynamic stress
response program.
Accepted March 1, 2000. 相似文献
10.
Certain components of the jaw apparatus, or lantern, of regular sea-urchins form a ’compass system’ the function of which
has still to be established. This system includes ten compass depressors (CDs) which connect the compass ossicles to the inner
edge of the test. Previous studies focused on the CDs of euechinoid sea-urchins. This paper provides the first detailed account
of the organization and mechanical behaviour of the CDs of a cidaroid sea-urchin, Stylocidaris affinis. The outermost layer of its CDs is a coelothelium comprising apical peritoneocytes, sparse subapical myocytes and two types
of granule-containing cells. The central core of the CD is dominated by longitudinally orientated collagen fibrils arranged
in bundles surrounded by networks of beaded microfibrils. Myocytes are scattered throughout the core and are always surrounded
by a basal lamina which usually encloses the same two types of granule-containing cells observed in the coelothelium. Each
CD is attached to the outer coelomic septum by a mesentery, both the connective tissue and coelothelia of which lack myocytes
and granule-containing cells. From data on the relationship between the vertical position of the lantern and the passive and
active forces developed by intact CD sets, it appears that the CDs resist elevation of the lantern above its ’resting position’
and that they develop a maximal contractile force when their length corresponds to that at the resting position. The connective
tissue of the CDs has the capacity to undergo nervously mediated changes in stretch resistance, although this is expressed
more weakly than in the euechinoid CDs. These results are related to current views on the physiological role of the compass
system.
Accepted: 15 March 1998 相似文献