“Freshwater habitats in general are getting saltier for a number of reasons, including road salt and agricultural runoff, extraction of coal and natural gas, drought, and sea level rise,” says David Buchwalter, professor of toxicology at NC State and corresponding author of the research. “Freshwater insects and other organisms that live in these systems are used as indicators of the ecosystem’s health. When these systems get saltier, we see that insect diversity decreases, but we aren’t sure why.”

Aquatic animals (including insects and crustaceans) must constantly maintain the correct balance of water and salts within their body — a process called osmoregulation. Theoretically, the most favorable environment for aquatic animals would be one where external salinity levels are close to those inside the animal. That way the animal doesn’t have to work as hard to maintain osmoregulation.

However, the opposite seems to be true for freshwater insects — higher salinity is always associated with increased rates of ion uptake in insects, but it is also associated with developmental delays or death.

“We thought that freshwater insects might be shifting so much of their energy toward osmoregulation in saltier environments that they cannot grow or thrive,” Buchwalter says. “So we measured the metabolic rates of crustaceans and insects in dilute and saline environments to see if metabolic responses to salinity were similar.”

The team looked at three types of freshwater animals — two species of gammarid, or “scud,” which is a small freshwater crustacean; one freshwater snail; and three aquatic insect species.

In the first test, they measured the animals’ metabolism by placing them in waters with different concentrations of salt ions and looking at their rates of oxygen consumption. They observed that more dilute conditions made the crustaceans and snail breathe harder, increasing their metabolism, while insects’ metabolic rates were constant regardless of salinity.

Next, the team looked at whether an increase in breathing rates was linked to the transport of a particular ion. Radioactive isotopes of the salt ions calcium and sodium allowed the researchers to measure how much and how quickly the animals took up different ions.

The researchers found that calcium was the key driver of non-insects’ increased metabolism in lower salinity. In other words, the crustaceans and snail worked harder to transport the calcium ions they required in an environment where calcium was harder to find.

In contrast, the insects’ metabolic rates remained constant in both saline and dilute environments, even though they had a higher calcium ion transport rate in the saline environment. Insects seem to have very little demand for calcium; in fact, previous research has shown that excess calcium is potentially toxic to them.

The researchers think that the animals’ use of internal energy, or active transport, when moving the salts could be the explanation.

“When we see non-insects’ metabolisms increase in dilute environments, it could be due to the fact that they have to work harder to take in more calcium,” Buchwalter says. “And while it seems counterintuitive, the opposite is true for insects who are working harder in a more saline environment to maintain equilibrium, although their respiration rates don’t increase. Instead, they appear to utilize resources that would otherwise be dedicated to growth and development to ‘undo’ excessive ion uptake when things get saltier.

“Moving salt ions has an energy cost to the animal,” Buchwalter says. “So for freshwater insects, the idea that organisms should thrive in environments that are close to their internal salinity is wrong. Additionally, their low demand for calcium may help them thrive in very dilute environments where insects typically dominate the ecology. In contrast, low calcium appears to be stressful for the crustaceans and snail in this study. It is fascinating that species living in the same habitats can have such different physiologies.”

Future work will explore whether these physiological differences are based on the ancestry of the organisms tested, or the use of calcium in their exoskeletons/shells.

The work appears in the Journal of Experimental Biology and was supported by the National Science Foundation under grant IOS 1754884. First author and Ph.D. candidate Jamie Cochran was supported by a Goodnight Doctoral Fellowship. Catelyn Banks, formerly a student at the North Carolina School of Science and Mathematics, also contributed to the work.

The aim of the study was to assess whether fathers’ parental leave influences alcohol-related morbidity and mortality. In order to try to find out if that is the case, the researchers have investigated the effects of parental leave policy that was implemented in Sweden in 1995. The policy encouraged fathers to use parental leave by reserving 30 days of leave for their use alone and resulted in the proportion of fathers using parental leave increasing from 43 percent to 75 percent.

“Our findings were pretty remarkable considering the severity of the studied outcome. Although alcohol-related hospitalizations were rather uncommon, we found that after the policy was implemented there was a 34% decrease in these hospitalizations among fathers in the two years after birth, as well as smaller decreases up to 8 and 18 years after birth,” says Helena Honkaniemi, researcher at the Department of Public Health Sciences, Stockholm University.

“Most changes were found among hospitalizations for alcohol intoxication and alcohol-related mental and behavioral disorders. Additional analyses evaluating actual changes in parental leave use from before to after the policy suggest that these health consequences could be explained by the increase in fathers’ parental leave use, rather than other underlying trends,” says Helena Honkaniemi.

However, no changes were found for alcohol-related mortality.

Co-author Associate Professor Sol Juárez believes that the results of the study could be useful for policymakers.

“Policymakers should consider that fathers’ parental leave not only promotes more gender-equal participation in childcare, but can also reduce alcohol-related harms,” Juárez says.

The study “Alcohol-related morbidity and mortality by fathers’ parental leave: A quasi-experimental study in Sweden” draws on Swedish register data of all fathers of singleton children born from January 1992 to December 1997, three years before and after the policy was implemented.

Planets form in disks of gas and dust, known as protoplanetary disks, around protostars, young stars still in the process of forming. Planet growth is so slow that it’s not possible to watch the evolution as it happens, so astronomers observe many protostars at slightly different stages of planet formation to build up a theoretical understanding.

This time an international research team led by Satoshi Ohashi at the National Astronomical Observatory of Japan (NAOJ) used the Atacama Large Millimeter/submillimeter Array (ALMA) to conduct high-resolution observations of a protoplanetary disk around a relatively young protostar, DG Taurus located 410 light-years away in the direction of the constellation Taurus. The team found that DG Taurus has a smooth protoplanetary disk, without any rings which would indicate that planets are forming. This led the team to believe that DG Taurus system will start forming planets in the future.

The team found that in this pre-planet-formation stage, the dust grains within 40 AU (about twice the size of the orbit of Uranus in the Solar System) of the central protostar are still small, while beyond this radius the dust grains have started to grow in size, the first step in planet formation. This is contrary to theoretical expectations that planet formation starts in the inner part of the disk.

These results provide surprising new information about the dust distribution and other conditions at the start of planet formation. Future studies of more examples will further improve our understanding of planet formation.