�첥��Ƶ prof fills gaps in current understanding of opsins responsible for circadian rhythms

TORONTO, June 17, 2024 — This Thursday marks the first day of summer in the Northern hemisphere, the longest day of the year. Living beings have evolved over many millennia to react to varying amounts of sunlight exposure, governing everything from sleep-wake cycles, seasonal changes and more, but the proteins responsible for responding to different light environments for non-visual purposes are an under explored area of science.  , led by a �첥��Ƶ Faculty of Science professor and a former York researcher, found that frogs have maintained a shocking number, and diversity, of these light-sensing proteins, called opsins, over evolutionary time.

“We, and other animals, have many different types of nonvisual opsins and they can be present in different parts of the body including the eyes, brain, and skin. Right now, the days are getting longer as we approach summer and nonvisual opsins are involved in how our bodies respond to those differences,” says in the Department of Biology & Centre for Vision Research. “We found that frogs, despite being a largely nocturnal group, actually maintain more of these nonvisual opsin genes than any other group that is ancestrally nocturnal.”

Nonvisual opsins are found throughout the animal kingdom. In humans and other mammals, information about lighting conditions enters through the eye and is sent to the pineal gland, which will respond to light by suppressing or secreting hormones. This is an indirect process, but frogs still have a directly light sensing “third eye” that others in the animal kingdom lost long ago.

“There are several nonvisual opsins present in that organ in the top of the head, and that is going to help them regulate their day and night cycles,” says Schott. “Something interesting we found though was that most of these opsins are also still expressed in the eye, so the eye is still having a large role to play in light detection functions that aren't directly related to vision.”

Frogs, the researchers said, provide an opportunity to study the proteins under diverse ecological conditions. To investigate this diversity in frogs, the researchers combined genetic data from transcriptomes — the genetic sequences of all genes expressed in an organ — from the eyes of 81 frog species with publicly available genomes and multi-tissue transcriptome data from 21 additional species. These 102 species provided a broad sampling of frogs with different ecological adaptations.

“Frogs are cool because different species can live in the water, on land, in trees, or even underground,” says former Schott and Bell lab researcher Jack Boyette, lead author on the paper and current doctoral student at Penn State. “This gets further complicated by things like activity period — a lot of frog species are active at night, but some are active during the daytime. As you can imagine, all these different habitats have very distinct light environments, which has implications for the evolution and the function of sensory systems.”

The researchers say several groups, including mammals and snakes, have lost many opsin genes through the course of evolution, which might be explained by going through an evolutionary period where they lived nocturnally and the ability to sense light was not as important.  

Frogs are also an ancestrally nocturnal group, so the researchers expected to find reduced nonvisual opsin diversity in frogs. Remarkably, the frog genomes assessed in this study contained all 18 ancestral vertebrate nonvisual opsins. This surprising finding may result from complex life histories. 

“Within the lifetime of a single animal, many frog species transition between drastically different light environments,” Boyette said. “Even though a lot of adult frogs are nocturnal, that's not necessarily true of the larval tadpoles.”  

Additionally, the researchers identified genetic differences in opsins between groups with differing ecologies, life histories, and body types. This could potentially indicate that frog nonvisual opsins have adapted to specific lifestyles or environments, similar to findings in Schott’s last study which looked at the visual opsins in frogs’ eyes.

Other members of the research team include Rayna C Bell, California Academy of Sciences and National Museum of Natural History, Smithsonian Institution; Matthew K Fujita and Kate N Thomas, University of Texas at Arlington; Jeffrey W Stretcher and David J Gower, Natural History Museum of London.

The findings were published today in the journal Molecular Biology and Evolution.

Schott says this study has given first hints about how opsin genes whose functions are currently unknown might operate in frogs and they’ve identified a candidate gene that may be involved in regulating seasonal breeding in frogs.

“We still need a better understanding of the specific functions of each type of nonvisual opsin and how those functions have evolved and adapted in different animals, like the frogs in our study, to meet their specific needs,” says Schott. “It's a really exciting step towards a better understanding these seasonal patterns and how frogs and other animals use light in different ways to regulate their biological functions.”

About �첥��Ƶ

�첥��Ƶ is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change, and prepare our students for success. York’s fully bilingual Glendon Campus is home to Southern Ontario’s Centre of Excellence for French Language and Bilingual Postsecondary Education. York’s campuses in Costa Rica and India offer students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

Media Contacts: Emina Gamulin, �첥��Ƶ Media Relations and External Communications, 437-217-6362, egamulin@yorku.ca

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Ancestral legacy and continued present-day advantages may explain why diurnal frog species kept genes adapted to night vision

April 4, 2024, Toronto – Frogs display a remarkable diversity of species as a whole, but does the same hold true for their visual abilities? led by York’s Faculty of Science sought to answer this question by collaborating with researchers in Australia, Belgium, Brazil, Cameroon, Ecuador, Equatorial Guinea, French Guiana, Gabon, Seychelles, Sweden, United Kingdom and the United States, to get a sample of a diverse array of frogs to study the visual pigments found in their eyes.

“Through this large international collaborative effort, we were able to study the pigments of frogs from all over the world who have adapted to myriad environments, and for the most part, we found this diversity is ‘reflected’ in the pigments in frogs’ eyes,” says research lead and Assistant Professor in the Department of Biology Ryan Schott.

“We saw this pattern of visual evolution being driven by differences in species that are either aquatic as adults, or that are living on the ground, or trees. On the other hand, we didn’t find much of a difference with the small groups of frogs that have adapted to daytime conditions as opposed to their nocturnal cousins.”

The study, published today in Molecular Biology and Evolution, examined the frog visual system by looking at the visual pigments and other genes in the eyes of a diverse selection of frogs living in vastly different light environments. Visual pigments are the molecules in the photoreceptor cells of the retina that are responsible for detecting light and then sending signals to the brain to perceive that light.

“We humans, as well as many animals, have these pigments in our eyes that actually absorb and respond to light,” explains Schott, also with the Centre for Vision Research at York and former research associate with the National Museum of Natural History at the Smithsonian Institution in Washington, D.C. “It's the differences in these pigments that allow us to see at night versus in the day, and allow us to perceive colour differences. So, we were interested in how these pigments have evolved in these frogs in different light environments.”

Schott, who studies the visual system of vertebrates in his lab located at York’s Keele Campus, has previously looked at vision changes of southern leopard frogs as they metamorphose from aquatic tadpoles to frogs living on land, and found a lot of differences. However, the lack of difference between the diurnal and nocturnal frogs came as a surprise. While it is possible that differences were not captured in the method of research, Schott says their evolutionary heritage may provide an alternate explanation.

“Most frogs are nocturnal, and so ancestrally, they really have this visual system that's adapted to these nocturnal environments,” he says. “This is probably suggesting that even the diurnal animals need these adaptations to survive because of course, they could say, get woken up in the night by a predator and then need to use their visual system to escape.” 

About �첥��Ƶ

�첥��Ƶ is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change, and prepare our students for success. York’s fully bilingual Glendon Campus is home to Southern Ontario’s Centre of Excellence for French Language and Bilingual Postsecondary Education. York’s campuses in Costa Rica and India offer students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

Media Contacts: Emina Gamulin, �첥��Ƶ Media Relations and External Communications, 437-217-6362, egamulin@yorku.ca

The post The life aquatic: a game changer for frog vision, but little difference between night and day, York-led study finds appeared first on News@York.