And then on the other side of the spectrum you have orders like Cypridontiformes. This is an evolutionarily prolific group of species that includes both oviparious and viviparous (live young-bearing) species, with many oviparous species that appear to have arisen from viviparous species and thus must have evolved egg-laying independently; species that tolerate hot temperatures and both very high salinity and very low salinity; species with wide-ranging diets that include everything from tiny phytoplankton to mosquito algae; and species that can survive above water for hours. The over 1200 species of egg-laying Cypridontiformes are collectively known by the common name of killifish.
From a cool BBC Extreme Life page on killifish:
Killifish don't like to grow old – well, not old in the conventional sense. They don't mature like other fish, and many killifish species will live and die within a year. One species survives for less than three months, making it one of the shortest-lived of all known vertebrates.
They have other ways of breathing, apart from using their gills.
And swimming isn't really their thing. They prefer to live in puddles and pools, and have evolved their whole life strategy to cope without water, rather than with it.
Some species can survive out of water for more than two months. They will leave it to go for a walk and they even hunt on land.
During the wet season, when pools are full, the fish hatch. They quickly grow to maturity and start spawning, which they keep doing until the pools start to dry. At that point all the fish perish.
This cycle of life can be so quick that one species, the turquoise killifish (Nothobranchius furzeri) of equatorial Africa, lives for an average of just 10 weeks.
But they leave behind eggs in the soil, and these eggs represent the entire surviving populations of killifish.
These eggs survive the dry season in a dormant state, or diapause, buried in the soil until the following rainy season. The return of the rains causes eggs to hatch and the cycle begins anew, says [UC-Riverside professor Andrew Furness].
To do this, different killifish are able to stopping growing as embryos, and then start again when conditions are right. And they can stop at different times during their development, delaying the growth of major organs, such their skulls, hearts and circulatory systems. They can then delay hatching for days, weeks or months.
The ability to generate a large amount of data using the killifish, especially compared to mice, could make it useful for both academia and industry, Brunet said, "especially since we have the genome and the genome editing tools."
The Cell publication demonstrates the usefulness of this platform, showing how changes in the fish's genome could reproduce one of the nine hallmarks of aging, telomere erosion. The TERT gene encodes for an enzymatic component of telomerase, a complex that ensures that chromosome ends stay intact. When TERT was deleted from the killifish genome, both male and female fishes became sterile and tissues that are quickly regenerated, like in the gut and in the blood, showed defects. "It really mimics some of the features of the disease dyskeratosis congenita," a human disorder characterized by short telomeres, Brunet said.
Brunet has already thought of several experiments she wants to try with the fish, including studies on aging-related genes, testing drugs that could affect aging, and even the interactions between genes and drugs.
Brunet said her lab has already made other lines of the fish exhibiting other aging and age-associated disease traits, which she wants to share with the research community.
The fish already has attracted the attention of top scientists in the field of aging and age-associated diseases.
"I think the fish are great," Cynthia Kenyon, a leading aging researcher at the University of California, San Francisco, told GenomeWeb. Kenyon's lab is currently collaborating with Brunet's lab to evaluate the effect of certain molecules on lifespan in the killifish. "It needs a little more validation to become totally widely accepted," she said, "but I think it fills a real gap in our ability to assess the relevance of various biological pathways and networks in a vertebrate, economically and on a large scale."
The payoffs of specialization are exemplified by recent events in south-central Illinois’s Lake Mattoon, where an unidentified strain of virus that apparently specializes in carp really hit the jackpot, killing dozens of carp over a period of several days.
From Mattoon’s Journal Gazette and Times-Courier:
[Lake Supervisor Joel Pittman] said he and his crew have removed some of the dead carp from public recreation areas and moved the carcasses into city woodland to decompose there. He said they do not have the resources to collect all of the dead carp, but the carcasses should completely decompose in coming days.
The recent death of the carp has been the biggest fish kill he has seen during his 20 years of working at Lake Mattoon, Pittman said.
Lake Mattoon resident Frank Jarvis said he has found several dead carp every day recently at his dock and has seen, and smelled, approximately 30 carcasses in a nearby cove. He said all of the dead fish he has encountered have been carp.
Doug Burtcheard of Mattoon was also out fishing at the marina. Burtcheard said he has spent many years fishing and chumming along the Gulf Coast, so the odor of the dead carp does not bother him.
Burtcheard said the fish kill does not seem to be affecting other fish in Lake Mattoon, adding that he has caught crappie, walleye and more recently.
Killfish, as we know, are very diverse and evolutionarily prolific, and so it’s no surprise that discovery of killifish fossils could spark new insights into evolutionary processes. Already some of the similarities and differences between Kenyaichthys and other killifish species (both extinct and currently extant) are prompting new lines of thinking about their past.
"Our fossils exhibit morphological traits that are found in extant African species of killifish. But they also possess one specific trait that is typical for contemporary rivulids from South America. This combination is very unusual, and may indicate that Kenyaichthys is closely related to forms that are now restricted to South America. Alternatively, this particular character may have been lost in the lineage that gave rise to modern African aprocheiloids," Altner explains.
Furthermore, many features of the new fossils – including elements of the tailfin and the dorsal fins, and the relative sizes of the different body parts – vary markedly from one individual to the next. As the closest surviving relatives of Kenyaichthys do not display such a wide range of variability, the fossil material from the Tugen Hills appears to document a particularly fascinating evolutionary process – the diversification of a so-called species flock. The term 'species flock' refers to a group of closely related species that have evolved from a single progenitor species in an isolated population and developed distinct specializations that enable them to coexist. Darwin's finches, which occupy different ecological niches on the Galapagos, are perhaps the best known example of a species flock. "So, this is an exciting find in many respects, which provides wholly new insights into the evolutionary history of the killifishes and their relatives," says Reichenbacher.
[Symbiodinium trenchii] lives in the cells of corals and provides them with food, by harnessing the sun’s energy to make sugars. It typically does this in its native waters in the Indo-Pacific Ocean. But somehow, it recently found its way to the Caribbean, on the other side of the world. And there, it displays all the characteristics of an invasive species.
Tye Pettay from Pennsylvania State University has shown that S.trenchii has spread through a large number of Caribbean corals. It provides its hosts with nutrients but is less generous than the native coral-associated algae that is has displaced. It is especially common in populations that have been ravaged by heat or pollution or disease. It looks for all the world like an opportunistic infection, of the kind that takes hold in people whose immune systems have been weakened. “It’s all over the Caribbean and it’s not going away,” says Todd LaJeunesse, who led the study.
To avoid a significantly changed and warmer climate, as well as the other impacts of rising levels of CO2, the world needs to achieve roughly an 80% reduction in emissions of CO2. The authors outline a number of ways in which this might be done. All of these strategies to reduce the concentration of CO2 in the atmosphere are relatively slow (decades to centuries) and expensive (perhaps 0.5% to 5% of world GDP).
In contrast, if the fraction of sunlight reflected by the earth back into space (the albedo) is slightly increased, then the amount of sunlight that is absorbed by the earth system is slightly reduced and the planet is cooled. This can occur very rapidly – requiring only days to months. Large explosive volcanic eruptions clearly demonstrate this when they add large amounts of fine reflective particles to the stratosphere. Humans could do similar things to increase albedo, perhaps at a cost that is 1/100th or less of the cost of reducing the level of CO2 in the atmosphere.