The annual killifish Austrofundulus limnaeus inhabits ephemeral ponds that dry out on a seasonal basis, thereby killing the adult and juvenile forms. Populations persist because diapausing embryos become embedded in the pond sediments. The rate of oxygen consumption of diapause II embryos is depressed by up to 90 % compared with that of developing embryos, and a parallel reduction is observed in heart rate. Developmental arrest was identified by cessation of somite proliferation and blockage of the ontogenetic increase in DNA content. Surprisingly, the arrest of metabolism and development is temporally offset as embryos reach diapause II; metabolic rate begins to decline 12 days prior to arrest of development. Release of embryos from diapause II is facilitated by increasing the light phase of the photoperiod. The rate of oxygen consumption of diapause III embryos is 84 % lower than the value preceding diapause III. The total energy flow of diapause II embryos apparently includes a contribution from anaerobic processes on the basis of calorimetric/respirometric ratios that are above the oxycaloric equivalent. Accumulations of lactate and ethanol at the expense of glycogen reserves are small or undetectable and do not account for the excess heat signal. Diapause II embryos maintain high [ATP]/[ADP] ratios and adenylate energy charge during diapause, consistent with a simultaneous depression of energy use and demand. Levels of AMP increase during early development and diapause II despite the highly charged adenylate pool. High values for [AMP]/[ATP] ratios in diapause II embryos are correlated with decreased rates of oxygen consumption and heat dissipation, which suggests a role for AMP in the depression of metabolism during early development and diapause II.

The bioenergetics of embryonic diapause in an annual killifish, austrofundulus limnaeus

Two ways in which organisms adapt to variable environments are phenotypic plasticity and bet-hedging. Theory suggests that bet-hedging is expected to evolve in unpredictable environments for which reliable cues indicative of future conditions (or season length) are lacking. Alternatively, if reliable cues exist indicating future conditions, organisms will be under selection to produce the most appropriate phenotype -that is, adaptive phenotypic plasticity. Here, we experimentally test which of these modes of adaptation are at play in killifish that have evolved an annual life cycle. These fish persist in ephemeral pools that completely dry each season through the production of eggs that can remain in developmental arrest, or diapause, buried in the soil, until the following rainy season. Consistent with diversified bet-hedging (a risk spreading strategy), we demonstrate that the eggs of the annual killifish Nothobranchius furzeri exhibit variation at multiple levels-whether or not different stages of diapause are entered, for how long diapause is entered, and the timing of hatching-and this variation persists after controlling for both genetic and environmental sources of variation. However, we show that phenotypic plasticity is also present in that the proportion of eggs that enter diapause is influenced by environmental factors (temperature and light level) that vary seasonally. In nature there is typically a large parameter zone where environmental cues are somewhat correlated with seasonality, but not perfectly so, such that it may be advantageous to have a combination of both bet-hedging and plasticity.

Adaptation in a variable environment: Phenotypic plasticity and bet-hedging during egg diapause and hatching in an annual killifish

Phylogenetic relationships within the family Rivulidae (order Cyprinodontiformes) are investigated using 1972 aligned base pairs of mitochondrial DNA (mtDNA) for samples representing 66 species. Genes analyzed include those encoding the 12S ribosomal RNA; transfer RNAs for valine, glutamine, methionine, tryptophan, alanine, asparagine, cysteine, and tyrosine; complete NADH dehydrogenase subunit II; and part of cytochrome oxidase I. Parsimony analysis of the aligned mtDNA sequences results in a single most parsimonious tree. The phylogeny reveals two independent origins of developmental diapause within the family Rivulidae. It is unlikely that diapause evolved de novo in each group, suggesting that the presence or absence of diapause is the result of developmental switches between alternative stabilized pathways. Phylogeny of the family Rivulidae shows high concordance with predictions derived from the geological history of South America and Central America. Basal lineages in the rivulid phylogeny are distributed primarily on geologically old areas, whereas more nested lineages occur in geologically younger areas. However, there is little concordance between the molecular phylogeny and currently available morphological hypotheses and existing taxonomies. Based on the mtDNA phylogeny, the genera Pterolebias, Rivulus, Pituna, and Plesiolebias are considered nonmonophyletic and warrant taxonomic reassessment.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1999.tb04533.x

The evolution of diapause in the killifish family rivulidae (atherinomorpha, cyprinodontiformes): a molecular phylogenetic and biogeographic perspective

Human ageing is a fundamental biological process that leads to functional decay, increased risk for various diseases and, ultimately, death. Some of the basic biological mechanisms underlying human ageing are shared with other organisms; thus, animal models have been invaluable in providing key mechanistic and molecular insights into the common bases of biological ageing. In this Review, we briefly summarise the major applications of the most commonly used model organisms adopted in ageing research and highlight their relevance in understanding human ageing. We compare the strengths and limitations of different model organisms and discuss in detail an emerging ageing model, the short-lived African turquoise killifish. We review the recent progress made in using the turquoise killifish to study the biology of ageing and discuss potential future applications of this promising animal model.

/pdf/the-short-lived-african-turquoise-killifish-an-emerging-19ub06r7pk.pdf

The short-lived African turquoise killifish: an emerging experimental model for ageing

The African killifish Nothobranchius furzeri is the shortest-lived vertebrate that can be bred in captivity. N. furzeri comprises several wild-derived strains with striking differences in longevity ranging from 3 to 9 months, which makes it a powerful vertebrate model for aging research. The short life cycle of N. furzeri should also facilitate studies on adult traits that are specific to vertebrates. Although progress has been made to generate a genetic linkage map and to start sequencing the genome of N. furzeri, tools to genetically manipulate this species of fish have not yet been developed. Here, we report the first establishment of transgenesis in N. furzeri. We use the Tol2 transposase system to generate transgenic N. furzeri that express green fluorescent protein driven by the Xenopus cytoskeletal actin promoter or the zebrafish heat-shock protein 70 promoter. We successfully generate stable transgenic lines of N. furzeri with germline transmission of integrated transgene. The development of transgenesis in N. furzeri provides a powerful tool to investigate the mechanisms underlying aging and longevity in a short-lived vertebrate model. Transgenesis in this fish will also facilitate the study of other phenotypes, including adult tissue regeneration and cognitive behavior.

/pdf/transposon-mediated-transgenesis-in-the-short-lived-african-4arm78yuws.pdf

Transposon-Mediated Transgenesis in the Short-Lived African Killifish Nothobranchius furzeri, a Vertebrate Model for Aging

Annual fish are found in temporary bodies of water in habitats of alternating rainy and dry seasons. The populations survive the dry seasons in the form of embryos encased in the bottom mud. Several genera of annual fish have been reported to exhibit diapause (developmental arrest) at three specific stages of development and it has been proposed that through this adaptation the populations are able to survive the variable durations of the dry seasons. The effects of incubation ans spawning temperatures, and season of collection on the onset and duration of diapause in laboratory populations of the annual fish, Nothobranchius guentheri, were studied. At low incubation and spawning temperatures there was a prolongation of Diapause I and Diapause II. In addition, fish spawned at 25 degrees C during the short days of winter produced embryos that entered a prolonged duration of Diapause II, whereas embryos produced during the long days of summer bypassed Diapause II.

The effects of temperature and season of collection on the onset and duration of diapause in embryos of the annual fish Nothobranchius guentheri.

Nothobranchius guentheri is an East African annual fish found in temporary bodies of water in areas of alternating rainy and dry seasons. During the dry season the embryos may be exposed to temperature extremes. Embryos have been reported to undergo diapause (developmental arrest), and are thus able to withstand the variable durations of the dry seasons. Since the embryos appear to endure long durations in diapause, and since in diapause they may be exposed to large variations in temperature, we have attempted to determine the thermal tolerance and responsiveness of embryos at diapause and at stages exclusive of diapause. Embryos were exposed to temperatures ranging from −8-40°C for variable durations of time, and survival, abnormalities and developmental rates determined. Both Diapause I and Diapause II embryos were much less sensitive to temperature extremes than were the other stages, and Diapause II was much less sensitive than Diapause I. Abnormalities only occurred under certain temperature exposures but showed the highest frequency at the early stages of development. Short exposure of Diapause I embryos to −8 and 3.4°C eliminated Diapause II, while short exposure to 40°C enhanced its duration. Although it has been proposed that the onset and duration of the diapauses are denendent on the oxygen concentration of the water, we propose that temper ature may also be another imposrant factor.

The survival of embryos of the annual fish Nothobranchius guentheri exposed to temperature extremes and the subsequent effects on embryonic Diapause

Nothobranchius guentheri, an annual fish from East Africa, is found in temporary ponds, pools, and streams that dry seasonally. The populations survive the dry seasons in the form of thickly chorionated embryos encased in the muddy substrates. When N. guentheri adults are allowed to spawn in the laboratory at 24.0 +/- 1 degree C and the fertilized eggs are collected shortly afterwards, formation of the embryonic axis normally occurs within 5 to 11 days. However, examination of embryo populations obtained from unaerated aquaria after uninterrupted spawning periods of up to 2 or 3 months revealed only rare instances of embryogenesis. The overwhelming majority of embryos proceeded no further than the dispersed cell phase (diapause I, stage 20). Spawning was found to be continuous throughout these prolonged periods and the possibility of adult predation was eliminated. While low PO2 has been determined to be a factor contributing to the duration of diapause I, determinations of PO2, PCO2, pH, free ammonia and bacterial flora indicated that aquarium conditions could support embryogenesis. Only embryos at stages 20 and 32, both being stages of naturally occurring diapause, could be inhibited. The inhibitory effect was dependent on the adult density and was diminished with aeration. It is proposed that, in nature, the adult-produced inhibitory factor may be useful in the conservation and augmentation of the embryonic reserve which is the mainstay of annual fish populations in tropical areas of alternating rainy and dry seasons.

Reversible stage-specific embryonic inhibition mediated by the presence of adults in the annual fish Nothobranchius guentheri†

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Jules Markofsky

Author Tools

Chat about Author

Papers

The effects of temperature and season of collection on the onset and duration of diapause in embryos of the annual fish Nothobranchius guentheri.

The survival of embryos of the annual fish Nothobranchius guentheri exposed to temperature extremes and the subsequent effects on embryonic Diapause

Reversible stage-specific embryonic inhibition mediated by the presence of adults in the annual fish Nothobranchius guentheri†