Slugs’ tunnels reveal early bilateral animals
Bilateral animals or bilaterians – so called because unlike, say, jellyfish, they have left, right, back and front sides – are probably the first animals that could move on their own. Until now, the oldest fossil evidence for bilaterians dated back 555 million years. However, scientists have found fossil burrows of a segmented slug that are about 30 million years older.
The burrows, found in northeastern Uruguay, have fine details that offer hints about the appearance and behaviour of the animals that made them. The slugs were less than four-tenths of an inch long and apparently moved in search of food, grazing on various kinds of organic material found on the sea bottom in shallow water.
They had primitive “feet” that they could extend into the mud to help them slide along. The researchers dated the fossils by measuring uranium decay over time, which allows them to estimate their age quite accurately, geologically speaking: within 6 million years.
“These fossils represent some behaviours that have already evolved,” said the senior author, Murray K Gingras, a professor of paleontology at the University of Alberta, who reported the findings in Science. “So these probably aren’t the oldest trace fossils – there must be something a little older out there still. That gives paleontologists something to do.”
No modest mate for flashy male birds
Everyone knows that male birds are usually the ones with pretty colours and that dull-looking females look for flashy mates. But male blue tits, apparently, judge females by their looks. And new research suggests that the males are more attentive fathers to their babies if the mother is pretty.
Birds of the species, both male and female, have shiny blue feathers on their heads that reflect ultraviolet light. For the study, published online in the journal Frontiers in Zoology, scientists captured females while they were taking care of chicks and assigned them to either an experimental group or a control group, smearing the crests of the first group with UV-blocking chemicals to make the feathers look dull. Then they restored the birds to their nests. The male birds made significantly fewer feeding excursions for the nestlings of females with the UV-blocking chemicals on their feathers.
The reason, the authors say, is that males judged females with poor coloration less likely to produce healthy offspring, and therefore less worthy of energy expended taking care of them – what the researchers call the differential allocation hypothesis.
Providing food is costly, and males do not waste their effort on babies unlikely to reproduce their genes.
Matteo Griggio, a postdoctoral researcher at the University of Veterinary Medicine in Vienna says, “We focused on the females and found that the males, the fathers, change their behaviour according to the females’ appearance.”
Corals rebounded from hostile climate
Increasing sea temperatures caused by global warming are harming coral reefs, but a new study suggests this is not the first time it has happened. Researchers took core samples from reefs off the coast of Panama, estimating their age at different levels using radiocarbon dating and other methods.
They found that the reefs stopped growing about 4,000 years ago and did not recover for 2,500 years.
According to the researchers, whose work was published online in the journal Science, the beginning of that 2,500-year period coincided with the start of a series of extremely strong El Nino effects, elevations of water temperature every three to seven years that cause long-term changes in weather. Then, about 3,800 to 3,200 years ago, there was a cycle of La Nina events – periods of unusually cold ocean temperatures – which could also have affected coral reef health.
Kotwal is one of the team leaders in ATLAS and not ALICE as stated in the article entitled ‘Deep in the boson of the universe’ (July 10). Also, Kotwal is from the Duke University. We regret the error.