Fish with attitude:

Some like it hot

Coral reef fish can undergo a personality change in warmer water, according to an intriguing new study suggesting that climate change may make some species more aggressive.

Experiments with two species of young damselfish on Australia’s Great Barrier Reef have shown for the first time that some reef fish are either consistently timid, or consistently bold, and that these individual differences are even more marked as water temperatures rise.

A slight lift of just one or two degrees may have only a small effect on some fish, but the behaviour of others can be transformed — leading them to become up to 30 times more active and aggressive.

“The idea that fish have personalities may seem surprising at first, but we now know that personality is common in animal populations, and that this phenomenon may have far-reaching implications for understanding how animals respond to ecological and environmental challenges,” says Dr Peter Biro, of the UNSW School of Biological, Earth and Environmental Sciences, who led the study with colleagues Christa Beckmann and Judy A. Stamps. It is published in the journal Proceedings of the Royal Society B.

“Our results also suggest that temperature variations are much more significant than we thought in the way they affect the behaviours of individual animals. This needs to be taken into account for scientific studies of other cold-blooded animals, or ectotherms, such as reptiles and amphibians.

“For instance, individual variations in activity and boldness can affect food acquisition, encounter rates with predators and even the likelihood of an individual being captured by sampling or harvesting gear.

“We observed that most of the individuals in our experiments were very responsive to changes in temperature, dramatically increasing their levels of activity, boldness and aggressiveness as a function of increases, of only a few degrees of temperature. Fish would experience such temperature fluctuations during the course of a normal day.” The scientists used fish that were captured just as they were ending their larval stage in open water and had not yet settled on to the reef, and so were naive to social hustle and bustle of reef fish life. They then directly manipulated water temperatures in laboratory tanks at Lizard Island Research station.

Placed by themselves in tanks, the fish were free to explore or to take refuge in a short piece of plastic pipe. The scientists observed how far and how often the fish ventured from the pipe. In cooler water, individual fish differed greatly in their activity levels. They all became more active to varying degrees when the water was warmed, with some becoming up to 30 times more active, bold and aggressive.

Courtesy: AP

When did animals move to land?

Fossilised footprints, found in a Polish quarry, of an enigmatic, long-extinct creature have prompted palaeontologists to reopen the file of how life in the sea moved to the land.

A key theory in evolutionary biology is that tetrapods — four-limbed land-loving vertebrates — emerged from fishes with pairs of lobed fins.The intermediate stage in the process was fishes called elpistostegids, whose head and body had a tetrapod-like shape but still retained fins instead of hands and feet, according to this idea.

The star of these “missing link” creatures is Tiktaalik, a large shallow-water fish whose fossilised remains were found in 2006 just 1,000 kilometres (600 miles) short of the North Pole, unearthed from river sediments on Canada’s Ellesmere Island.

Tiktaalik lived around 375 million years ago, although even older elpistostegids, dating back to 385 million years, have been found.

But trackways found at a disused quarry at Zachelmie in the Holy Cross Mountains of southeastern Poland have thrown the timeline and the elpistostegids’ role into question.

In a paper released by the British weekly journal Nature, a team led by tetrapod sleuth Per Ahlberg of Uppsala University, Sweden, report the finding of a dozen distinctive “hand” and “foot” prints from a creature that lived around 395 million years ago.That makes them 18 million years older than the earliest tetrapod fossils found so far and a whopping 10 million years earlier than the first known elpistostegids.The imprints, made in what at the time was the mud of a shallow marine lagoon, are up to 26 centimetres (10.3 inches) wide, which suggest the tetrapod was around 2.5 metres (8.1 feet) long.

There is no sign of body drag, which suggests that the tetrapod must have been floating on the water while walking on the muddy bottom, say the authors.The find is radical, for it implies that tetrapods showed up much earlier than thought.

Instead of living in river deltas and lakes before sliding on to land, they thrived in shallow seas, trampling the mud of balmy, coral-reef lagoons.Just as important, the new theory suggests that the once-coveted elpistostegids — or at least the ones unearthed so far — were just a failed branch rather than part of the stem from which all land vertebrates, including us, evolved.

The prints “force a radical reassessment of the timing, ecology and environmental setting of the fish-tetrapod transition, as well as the completeness of the body fossil record,” says the study.

-Courtesy AFP

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