Small marine creatures swimming in plastic chemicals not reproducing

Plastic waste in the water might be stopping -- or interrupting -- some shrimp-like creatures from reproducing.

In a unique study, the ability of 'shrimp like' creatures to reproduce successfully was found to be compromised by chemicals found in everyday plastics.

Research showed that little critters, known as marine amphipod Echinogammarus marinus, changed their mating behaviour when exposed to toxic plastic additives.

Until now, most research into plastic pollution has focused on visual plastics; what can get trapped in plastics and the dangers of ingesting large particles.

Scientists from the University of Portsmouth have taken a different approach and investigated the chemicals that are used as ingredients in plastics.

Professor Alex Ford, from the Institute of Marine Sciences at the University of Portsmouth, says: "This unsuccessful mating behaviour has serious repercussions, not only for the species being tested but potentially for the population as a whole. These animals form pairs to reproduce. Once they were exposed to a chemical, they would break apart from their mate and take much longer -in some cases days -- to repair, and sometimes not at all.

"These creatures are commonly found on European shores, where they make up a substantial amount of the diet of fish and birds. If they are compromised it will have an effect on the whole food chain."

There are over 350,000 chemicals in use around the world in everyday products.

Ten thousand of these are used to enhance plastics. Chemicals can be used to make plastics more flexible, add colour, give sun protection or make plastic flameproof.

Around one third of these chemicals are known to be toxic to human's immune, nervous or reproductive systems.

The study, published in the journal Environmental Pollution, tested four widely used chemicals found in plastics.

These plastic additives are used in a variety of common products, for example, phthalates (DEHP and DBP) which are found in medical supplies, food packaging and toys.

Triphenyl phosphate (TPHP) is mainly used as a flame retardant in products like nail polish and electronic equipment, including cables, and N-butyl benzenesulfonamide (NBBS) is used in nylon, medical devices, cooking utensils and films.

Bidemi Green-Ojo, lead author and PhD Researcher in Environmental Toxicology at the University of Portsmouth, says: "We chose these four additives because the suspected danger they pose to human health is well documented. Two of the chemicals we investigated (DHP and DEHP) are regulated and not allowed to be used in products in Europe. The other two chemicals have no current restrictions on them and are found in many household products. We wanted to test the effects these chemicals had on aquatic mating behaviour."

The 'shrimp like' creatures which have been studied are known to pair up and typically lock together for two days while mating.

Pairs of them were exposed to each chemical, and researchers monitored their behaviour over four days, measuring the time it took for the creatures to mate.

They found that at best it took much longer for the creatures to re-pair, and at worst they didn't re-pair.

The experiment found that all the plastic additives had the capacity to reduce the overall percentage of animals that formed pairs.

The ones which did form pairs took longer to make contact and re-pair.

Two of the chemicals caused a concentration-dependent effect on shrimps' sperm, resulting in a decline of up to 60 per cent in sperm count of those exposed to elevated levels of the chemicals.

"Although the animals we tested were exposed to much higher concentrations than you would normally find in the environment, the results indicate these chemicals can affect sperm count," explains Professor Ford.

"It is conceivable that if we did the experiment on shrimps that had been exposed for a longer period or during critical stages in their life history, it would affect their sperm levels and quality."

Bidemi Green-Ojo adds: "We must understand more about these chemicals and how they affect behaviour. Many types of behaviour -- such as feeding, fight or flight mode, and reproduction -- are essential in an animal's life, and any abnormal behaviour may reduce the chances of survival.

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Brittle stars can learn just fine -- even without a brain

We humans are fixated on big brains as a proxy for smarts. But headless animals called brittle stars have no brains at all and still manage to learn through experience, new research reveals.

Relatives of starfish, brittle stars spend most of their time hiding under rocks and crevices in the ocean or burrowing in the sand.

These shy marine creatures have no brain to speak of -- just nerve cords running down each of their five wiggly arms, which join to form a nerve ring near their mouth.

"There's no processing center," said lead author Julia Notar, who did the research as part of her biology Ph.D. in professor Sönke Johnsen's lab at Duke University.

"Each of the nerve cords can act independently," Notar said.

"It's like instead of a boss, there's a committee."

In the case of brittle stars, that seems to be enough to learn by association, Notar, Johnsen and former Duke undergraduate Madeline Go report in the journal Behavioral Ecology and Sociobiology.

This type of learning involves associating different stimuli via a process called classical conditioning.

A famous example is Pavlov's dog experiments, which showed that dogs repeatedly fed at the ringing of a bell would eventually start drooling at the mere sound of a bell, even when no food was around.

Humans do this all the time. If you hear the "ding" of a smartphone over and over again with each new alert, eventually the sound starts to have a special meaning.

Just hearing someone's phone ping or buzz with the same chime as yours is enough to make you reflexively reach for your own phone in anticipation of the next text, email, or Instagram post.

Classical conditioning has been demonstrated in a handful of previous studies in starfish.

But most echinoderms -- a group of some 7,000 species that includes brittle stars and similarly brainless starfish, sea urchins and sea cucumbers -- have not been tested.

To find out if brittle stars are capable of learning, the researchers put 16 black brittle stars (Ophiocoma echinata) in individual water tanks and used a video camera to record their behavior.

Half the brittle stars were trained by dimming the lights for 30 minutes whenever the animals were fed.

Every time the lights went out, the researchers would put a morsel of shrimp -- "which they love" -- in the tanks, placed just out of reach.

The other half got just as much shrimp and also experienced a 30-minute dark period, but never at the same time -- the animals were fed under lit conditions.

Whether it was light or dark, the animals spent most of their time hiding behind the filters in their tanks; only coming out at mealtime.

But only the trained brittle stars learned to associate darkness with food.

Early in the 10-month-long experiment, the animals stayed hidden when the lights went out.

But over time, the animals made such a connection between the darkness and mealtime that they reacted as if food was on its way and crept out of hiding whenever the lights went out, even before any food was put in the tanks.

These brittle stars had learned a new association: lights out meant that food was likely to show up. They didn't need to smell or taste the shrimp to react.

Just sensing the lights go dim was enough to make them come when called for dinner.

They still remembered the lesson even after a 13-day 'break' without training, i.e., dimming the lights over and over again without feeding them.

Notar said the results are "exciting" because "classical conditioning hasn't really been shown definitively in this group of animals before."

"Knowing that brittle stars can learn means they're not just robotic scavengers like little Roombas cleaning up the ocean floor," Notar said.

"They're potentially able to expect and avoid predators or anticipate food because they're learning about their environment."

As a next step, Notar hopes to start to tease apart how they manage to learn and remember using a nervous system that is so different from our own.

"People ask me all the time, 'how do they do it?'" Notar said.

Read more at Science Daily

Learning about the first animals on Earth from life at the poles

The amazing survival strategies of polar marine creatures might help to explain how the first animals on Earth could have evolved earlier than the oldest fossils suggest according to new research. These first, simple and now extinct, animals might have lived through some of the most extreme, cold and icy periods the world has ever seen. The study is published in the journal Global Change Biology, published this week (12 October 2022).

The fossil record places the earliest animal life on Earth at 572-602 million years ago, just as the world came out of a huge ice age, whilst molecular studies suggest an earlier origin, up to 850 million years ago. If correct, this means that animals must have survived during a time influenced by multiple global ice ages, when the whole or large parts of the planet were encased in ice (snowball and slushball Earths), far bigger than any seen since. If animal life did arise before, or during, these extreme glacial periods it would have faced conditions like modern marine habitats found in Antarctica and the Arctic today, and required similar survival strategies.

Over millions of years, the expansion and contraction of the ice sheets during cold and warm periods has driven the evolution of Antarctica's thousands of unique animals and plant species. The same could be true for the evolution of animal life on Earth. Whilst to humans the polar regions seem like the most hostile environments to life, they are the perfect place to study the past and the potential for life in the universe beyond our planet, such as on icy moons like Europa.

Marine biologist and lead author, Dr Huw Griffiths of British Antarctic Survey (BAS), says:

"This work highlights how some animals in the polar regions are incredibly adapted to life in and around the ice, and how much they can teach us about the evolution and survival of life in the past or even on other planets.

"Whether it is animals living upside down on the underside of ice instead of the seafloor, sponges living hundreds of kilometres under thick floating ice shelves, organisms that are adapted to live in seawater colder than ?2°C, or whole communities existing in the darkness on food sources that don't require sunlight, Antarctic and Arctic life thrives in conditions that would kill humans and most other animals. But these cold and icy conditions help to drive ocean circulation, carry oxygen into the ocean depths and make these places more suitable for life."

Floating ice covers more than 19 million km2 of the seas around Antarctica and 15 million km2 of the Arctic Ocean during winter. Under possibly the most extreme snowball Earth, lasting 50 to 60 million years during the Cryogenian period (720 to 635?million years ago), the whole world (510 million km²) is believed to have been entombed in ice around a kilometre thick, but there is some evidence that this ice was thin enough at the equator to allow marine algae to survive.

"The fact that there is this huge difference in the timing of the dawn of animal life between the known fossil record and molecular clocks means that there are huge uncertainties about how and where animals evolved" says co-author Dr Emily Mitchell, palaeontologist and ecologist at the University of Cambridge. "But if animals did evolve before or during these global ice ages, they would have to contend with extreme environmental pressures, but ones that may have helped to force life to become more complex to survive."

"Just like in Antarctica during the Last Glacial Maximum (33-14 thousand years ago), the huge amounts of advancing ice would have bulldozed the shallows, making them inhospitable to life, destroying fossil evidence and forcing creatures into the deep sea. This makes the chances of finding fossils from these times less likely and sheltered areas and the deep sea the safest places for life to evolve."

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