Fish use sharks as scratching posts
Australian and US scientists have investigated how fish get rid of pesky parasites and found that sharks are the most popular choice of underwater scratching post.
In a study published in PLOS ONE, researchers provided records of “scraping behaviour” in several species of fish spanning offshore waters in three ocean basins.
They extracted data from a global dataset of remote underwater video, captured across 55 expeditions to 36 global locations between 2012 and 2019. When scraping behaviour was noted, the video was analysed to gather information on the species and individuals involved.
They found that fish prefer to scratch theirheads, eyes, gills, and sides – where parasites are commonly found. And though preferences for scratching methods varied, including members of their own species, sharks were the most popular.
Smaller fish were also less likely to use a shark than a larger fish, potentially due to the risk of predation.
Because parasite removal due to scraping behaviour likely has positive health benefits for the fish, the authors suggest that the decline in shark numbers in our oceans could have negative effects on other vulnerable fish species.
Citizen science helping create global maps of plant traits
Scientists need extensive global maps of the characteristics of vegetation – information on leaf surface size, tissue properties and plant height – to study our terrestrial biosphere. But it is a painstaking and time-consuming process for professional scientists to collect this data manually, so the available worldwide plant trait data is scarce and only covers certain regions.
Up until now, global maps of plant traits have been created by estimating beyond the original observation range in the comprehensive (but still geographically limited) TRY Plant Trait database. However, the resulting maps are not particularly reliable.
Now, researchers have found they can fill in large data gaps by linking TRY to the vast dataset from the citizen science project iNaturalist where citizen scientists share their observations of nature by providing species names, photos, and geolocation.
“That the new maps, based on the citizen science data, seem to be even more precise than the extrapolations, was both surprising and impressive,” says first author Dr Sophie Wolf, a PhD researcher at Leipzig University, Germany.
“Our study convincingly demonstrates the potential for research into voluntary data,” says last author Dr Teja Kattenborn from Leipzig University and the German Centre for Integrative Biodiversity Research.
“It is encouraging to make increasing use of the synergies between the combined data from thousands of citizens and professional scientists.”
The research has been published in Nature Ecology & Evolution.
The Black Death made our immune systems what they are today
The Black Death – caused by the bacterium Yersinia pestis – spread through Europe, the Middle East, and North America from 1346 to 1350 ACE, and caused the death of between 30-50% of the population.
There were subsequent plague outbreaks in the following 400 years, but mortality rates decreased. This may have been due to changing cultural practices, pathogen evolution, or potentially human genetic adaption to the bacterium.
To explore this, researchers analysed ancient DNA samples extracted from 516 individuals who died before, during or soon after Black Death outbreaks in London, UK and across Denmark. They identified 245 genetic variants that were very different when comparing pre- and post- Black Death samples.
They found one genetic variant is associated with control of Y. pestis in laboratory experiments with blood cells (macrophages), suggesting that it may have contributed to resistance to Y. pestis.
“We show that protective variants overlap with alleles (a variant form of a gene) that are today associated with increased susceptibility to autoimmune diseases, providing empirical evidence for the role played by past pandemics in shaping present-day susceptibility to disease,” the authors write.
Alcohol increases our appetite for savoury foods
Researchers analysed data on 9,341 adults who took part in the Australian National Nutrition and Physical Activity Survey, 40% of whom had drunk alcohol in the previous 24 hours.The data included information on the food and drink each participant consumed over a 24-hour period, the total amount of energy consumed during that period and how much of that energy came from protein, fat, carbohydrate and other nutrients.
They found that participants who drank alcohol consumed more savoury foods than those who didn’t have any alcohol, but this was was associated with decreased energy intake in some consumers of alcohol, but increased energy intake in others.
Around two-thirds chose foods high in protein but low in carbohydrate and fat, while the other third chose “protein decoys” – savoury snacks that have the umami (savoury or meaty) taste of high-protein foods but are low in protein and high in fat.
“When consuming alcohol and your appetite is elevated, make sure you select healthier lean protein sources such as lean red meat, chicken, fish, seafood or legumes and avoid the urge to snack on low-protein, savoury snack foods,” recommends co-author Dr Amanda Grech, accredited practicing dietitian and nutrition epidemiologist at the University of Sydney, Australia.
Imma Perfetto is a science journalist at Cosmos. She has a Bachelor of Science with Honours in Science Communication from the University of Adelaide.
Read science facts, not fiction...
There’s never been a more important time to explain the facts, cherish evidence-based knowledge and to showcase the latest scientific, technological and engineering breakthroughs. Cosmos is published by The Royal Institution of Australia, a charity dedicated to connecting people with the world of science. Financial contributions, however big or small, help us provide access to trusted science information at a time when the world needs it most. Please support us by making a donation or purchasing a subscription today.