Science Briefs: How ancient fish learned to walk

How ancient fish walked out of the sea

About 400 million years ago, a group of fish began exploring land and evolved into today’s amphibians, reptiles, birds and mammals. But how these ancient fish used their fishy bodies and fins in a terrestrial environment is a scientific mystery.

Researchers at Quebec’s McGill University turned to a living fish – Polypterus to help show what might have happened when fish first attempted to walk out of the water. Polypterus is an African fish that can breathe air, “walk” on land, and looks much like the ancient fishes that evolved into land-living animals. The researchers raised juvenile Polypterus on land for nearly a year, according to their report, published in the journal Nature.

The fish showed significant anatomical and behavioral changes. The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water. “Anatomically, their pectoral skeleton changed to became more elongate with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion,” said Trina Du, a McGill Ph.D. student and study collaborator.

Duke study: How movement affects hearing

When we want to listen carefully to someone, the first thing we do is stop talking. The second thing we do is stop moving altogether. This strategy helps us hear better by preventing unwanted sounds generated by our own movements.

This interplay between movement and hearing also has a counterpart deep in the brain, according to a new Duke University study in Nature. The senior author of the report was Richard Mooney, a professor of neurobiology at Duke University School of Medicine, and a member of the Duke Institute for Brain Sciences.

The project combines cutting-edge methods in electrophysiology, optogenetics and behavioral analysis to reveal exactly how the motor cortex, seemingly in anticipation of movement, can tweak the volume control in the auditory cortex in mice. Whenever the mice moved – walking, grooming or making high-pitched squeaks – neurons in their auditory cortex were dampened in response to tones played to the animals, compared to when they were at rest.

Stiltgrass good for spider, but bad for toads

An invasive grass species frequently found in Southeast forests has created a thriving habitat for wolf spiders, who then feed on American toads, a University of Georgia study has found.

Japanese stiltgrass, accidentally introduced to the U.S. in the early 1900s, is one of the most pervasive invasive species and has spread to more than a dozen states in the past century. Typically found along roads and in forests, it can survive in widely diverse ecosystems and has been found to impact native plant species, invertebrate populations and soil nutrients.

In a new study published in the journal Ecology, UGA researchers found that Japanese stiltgrass also is affecting arachnid predators: Lycosid spiders, commonly known as wolf spiders, thrive in the grass. As their numbers grow, more spiders then feed on young American toads, ultimately reducing the amphibian’s survival wherever this grass grows.