Dolphins use a 'fat taste' system to get their mother’s milk

Hokkaido University

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The suckling behavior of a wild Indo-Pacific bottlenose dolphin. (Photo provided by Takashi Hayakawa, © Mikurashia Tourism Association)

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Credit: © Mikurashima Tourism Association

Juvenile dolphins were found to have specialized receptors for fatty acids on their tongues, offering new insights into their growth and feeding habits.

Scientists have discovered that juvenile bottlenose dolphins have specialized receptors for detecting the fatty acids in their mother’s milk. These findings, published in the journal Marine Mammal Science, offer important insights into how these marine mammals grow, feed, and communicate.

The new findings challenge previous assumptions about cetacean sensory systems. Unlike land mammals, dolphins and other marine mammals have limited olfactory capabilities – their sense of smell is largely nonfunctional in aquatic environments. Researchers have therefore speculated that dolphins had other ways of sensing their surroundings and detecting food.

Fat plays an essential role in providing energy and supporting brain development in dolphin calves, which are entirely dependent on their mother’s milk during their early stages of life.

"We looked at the tongue of a young Indo-Pacific bottlenose dolphin and confirmed special structures that may help it detect fat," says the study’s first author Hinako Katsushima of the Graduate School of Environmental Science at Japan’s Hokkaido University. "At the back of the tongue, there's a V-shaped row of taste receptors that are specifically tuned to pick up fatty acids. These receptors also have enzymes that help break down the fat, making it easier for the dolphin to sense and process it."

In a second experiment, the team gave young dolphins a choice between two liquids: one containing milk and the other a cloudy solution. The dolphin showed an unexpected preference for the cloudy solution. This reinforces the finding that dolphins can distinguish between the two liquids, but the researchers are unsure why they avoided the milk. One possibility is that they found the milk unfamiliar – it was a mixture of milk from two females – and so avoided it from a fear of new foods, a habit called neophobia.

“Our findings suggest that the ability to detect fatty acids in their mother's milk is part of a specialized ‘fat taste’ system that could help dolphins assess the nutritional value of their food,” says Assistant Professor Takashi Hayakawa from the Faculty of Environmental Earth Science at Hokkaido University, who led the study. “In the wild, where fat-rich diets are critical for survival, this capability may provide dolphins with an evolutionary advantage, allowing them to select high-quality milk from their mothers and later evaluate the nutritional content of their prey.”

The new study opens new avenues for understanding how marine mammals perceive and interact with their environment, as well as how they communicate and forage in the wild. Further research will be necessary to explore the full scope of this "fat taste" system and how it functions in other marine species.

The V-shaped row and marginal papillae of the tongue were analyzed in this study. (Illustration: Takashi Hayakawa)

Hinako Katsushima (left), first author, and Takashi Hayakawa (right), corresponding author of the study. (Photo: Takashi Hayakawa)

Credit

Takashi Hayakawa

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Journal

Marine Mammal Science

DOI

10.1111/mms.13195 

Method of Research

Experimental study

Subject of Research

Animals

Article Title

Fat taste receptors and fatty milk in dolphins

 

Curious blue rings in trees and shrubs reveal cold summers of the past — potentially caused by volcanic eruptions

Blue growth rings found in woody plant stems represent years when cells did not lignify properly because of summers too cold for growth

Frontiers

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A blue ring formed in 1902 in a tree in northern Norway. Image by Pawel Matulewski and Liliana Siekacz.

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Credit: Image by Pawel Matulewski and Liliana Siekacz.

When the going gets cold, even tough trees struggle with growing. Trees need a certain number of warm days in their growing seasons to grow properly; otherwise, the cell walls of new growth don’t lignify properly, creating ‘blue rings’ that appear when wood samples are dyed. Since trees and shrubs can live for hundreds of years, identifying these blue rings allows us to spot cold summers in the past. By looking at pine trees and juniper shrubs from northern Norway, scientists identified two extremely cold summers in 1902 and 1877, possibly caused by the eruptions of Mount Pelée on the island of Martinique and Cotopaxi in Ecuador.  

“Blue rings look like unfinished growth rings, and are associated with cold conditions during the growing season,” said Dr Agata Buchwal of Adam Mickiewicz University, Poland, lead author of the article in Frontiers in Plant Science. “In general, we found more blue rings in trees than in shrubs. Shrubs seem to be more adapted to cooling events than trees, which is probably why shrubs are found further north. That is why I love to study shrubs; they seem to be the true heroes of the north.” 

Growing pains 

The scientists sampled cores from 25 Scots pine trees and stem-base discs from 54 common juniper shrubs at a site high on the treeline of Mount Iškoras in northern Norway. The team cross-sectioned and stained these samples, then photographed them under a microscope so that growth ring widths could be measured and cross-dated, and blue rings identified.  

“Blue ring studies require a much longer protocol than classical dendrochronological studies,” Buchwal noted. “We are grateful to work with dedicated, highly-qualified lab technicians. Only together we can explore the blue ring world in high resolution using microscope slides!” 

Overall, only 2.1% of the pine trees’ rings and 1.3% of the juniper shrubs’ rings were blue; the cells which hadn’t lignified properly were mainly found at the end of growth rings, in latewood. Blue rings occurred most frequently in 1902 — 96% of pine trees and 68% of juniper shrubs — followed by 1877 — 84% of pine trees and 36% of juniper shrubs. Pine trees seemed to be more vulnerable to blue ring formation than juniper shrubs, which could make them a more sensitive indicator of cold summers. 

“In the case of pine trees in boreal regions, blue rings have the potential to weaken the tree, making it more susceptible to mechanical damage or disease,” explained Dr Pawel Matulewski of Adam Mickiewicz University, second author of the article. “If this phenomenon persists over several years, it can impede the tree's recovery in following years.” 

Comparing this data with local weather records showed that 1902 and 1877 were characterized by very low summer temperatures. In 1902 the coldest June ever recorded delayed the growing season, so a low total number of days in that year were warm enough for tree growth. This could explain why earlywood formed almost normally in 1902, but latewood didn’t, creating many blue latewood cells: the growing season was too short, so the latewood didn’t have time to develop properly.  

Comparing the cooling events — the 1902 event fell in June, when the growth season usually begins, and the 1877 event in August — suggests it may even be possible to differentiate between cooling at different times. Late cooling events may lead to more lignified cell walls and a ‘less blue’ ring. 

Volcanoes’ long shadow 

Other studies have linked blue rings to global climatic events, such as cooling after large volcanic eruptions. 1902’s cold June could be related to the eruption of Mount Pelée in May. Similarly, the late June eruption of Cotopaxi aligns with 1877’s cold August — but there is no other reported evidence for related cooling in northern Norway after this eruption. This blue ring could also be due to another, as-yet unidentified, factor.  

Looking at other blue rings, the scientists identified more potential cold summer periods — but the weather seems to have been less cold, and some temperature data were missing, preventing analysis. The scientists also cautioned that temperatures among the trees might have been different to those recorded at the Mount Iškoras weather station: future research will need in-situ weather data.  

“We hope to inspire other research groups to look for the blue rings in their material,” said Buchwal. “It would be great to establish a blue ring network based on trees and shrubs to reconstruct cooling events at the northern treeline over long timescales.” 

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Journal

Frontiers in Plant Science

DOI

10.3389/fpls.2024.1487099 

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Blue rings in trees and shrubs as indicators of early and late summer cooling events at the northern treeline

Article Publication Date

22-Jan-2025

SPAGYRIC HERBALISM

New frontiers in organic chemistry: Synthesis of a promising mushroom-derived compound

Researchers report the first-ever total synthesis of inaoside A, a chemical isolated from fungus with medical and dietary potential

Shinshu University

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Researchers from Japan have now proposed a novel strategy for synthesizing inaoside A from two major compounds: a ribofuranosyl trichloroacetimidate (left) and an aglycone (right). 

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Credit: Dr. Atsushi Kawamura from Shinshu University, Japan

Natural compounds from plants and animals have long been used in drug development, but mushrooms remain underexplored despite their rich chemical potential. Now, researchers from Japan have successfully developed the first method to synthesize inaoside A, a compound derived from the edible mushroom Laetiporus cremeiporus. This achievement will help better understand more of its bioactive properties and pave the way for similar mushroom-derived compounds in pharmaceuticals and functional foods.

Natural compounds derived from plants and animals have long been a source of inspiration when developing drugs and dietary supplements. Many well-established medical substances were derived from compounds isolated from plants, with morphine, aspirin, and paclitaxel being prime examples. Unfortunately, despite their long history of human consumption for their beneficial properties, mushrooms, and their varied chemical repertoire have received much less attention from biochemists.

Against this backdrop, a research team led by Assistant Professor Atsushi Kawamura from the Department of Biomolecular Innovation, Shinshu University, Japan, along with Mr. Tomoya Takao from the Department of Agriculture, Shinshu University, and Dr. Hidefumi Makabe from the Department of Biomolecular Innovation, Shinshu University, set their sights on inaoside A, an α-D-ribofuranoside-type compound they had previously isolated from the edible mushroom Laetiporus cremeiporus. Their study was made available online on October 31, 2024, and was published in Volume 13 Issue 12 of the Asian Journal of Organic Chemistry on December 13, 2024.

The motivation behind this study was twofold. “Although the α-D-ribofuranoside structure is frequently found in natural products, there have been fewer reports of the synthesis of α-D-ribofuranosides than of the β-anomers. Thus, the synthesis of α-D-ribofuranosides has attracted much attention from organic chemists,” says Dr. Kawamura. He further adds, “Moreover, the total synthesis of inaoside A is an important objective because its varied bioactivities need to be investigated.”

To achieve their goal, the research team used an α-selective Schmidt glycosylation as a key reaction. This reaction involves the attachment of a glycoside to another molecule in a specific position and orientation, known as an “α” position. The two molecules that would have to partake in Schmidt glycosylation were determined through retrosynthetic chemistry—an approach where chemists work backward from the desired final product to figure out the necessary starting materials and reactions.

This strategy led the team to two key compounds: an aglycone they could obtain from vanillin and a ribofuranosyl trichloroacetimidate. However, there was a problem: most reported syntheses of ribofuranosides following the general Schmidt glycosylation procedure tend to produce β-ribofuranosides rather than their α versions preferentially.

To overcome this hurdle, the researchers employed a different substrate for the reaction, namely a 2,3,5-tri-O-(tert-butyldimethylsilyl)-protected ribofuranoside substrate. Using this compound, which was easy to prepare and deprotect after the glycosylation reaction, the team successfully produced α-ribofuranoside with remarkable selectivity, attaining an α/β ratio ranging from 4:1 to 5:1.

Being able to synthesize recently discovered naturally occurring compounds is essential to uncover their properties and functionalities. “By elucidating the chemical structures and biological activities of natural products derived from mushrooms, we aim to discover the potential of edible mushrooms as functional foods. These natural products could contribute to advancing pharmaceutical science by serving as pharmaceutical leads,” highlights Dr. Kawamura. 

Now that it can be readily synthesized, the research team has high hopes for inaoside A. “Further studies on inaoside A, including more detailed investigation of its bioactivities, the synthesis of derivatives, and structure–activity relationship studies, are in progress. We would like to develop this chemical into a socially meaningful compound,” concludes Dr. Kawamura.

Overall, this synthetic chemistry breakthrough not only paves the way for further research into inaoside A’s qualities but also underlines the untapped potential of mushroom-derived compounds. As scientists continue to unlock the secrets of these natural products, the doors will open to novel therapeutic and dietary applications that could benefit human health.

 

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About Shinshu University

Shinshu University is a national university founded in 1949 and located nestling under the Japanese Alps in Nagano known for its stunning natural landscapes. Our motto, "Powered by Nature - strengthening our network with society and applying nature to create innovative solutions for a better tomorrow" reflects the mission of fostering promising creative professionals and deepening the collaborative relationship with local communities, which leads to our contribution to regional development by innovation in various fields. We’re working on providing solutions for building a sustainable society through interdisciplinary research fields: material science (carbon, fiber and composites), biomedical science (for intractable diseases and preventive medicine) and mountain science, and aiming to boost research and innovation capability through collaborative projects with distinguished researchers from the world. For more information visit https://www.shinshu-u.ac.jp/english/ or follow us on X (Twitter) @ShinshuUni for our latest news.

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Journal

Asian Journal of Organic Chemistry

DOI

10.1002/ajoc.202400547 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

First Total Synthesis of Inaoside A

 

Dining out with San Francisco’s coyotes

How a city reshapes what a native predator eats

Peer-Reviewed Publication

University of California - Davis

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A coyote in San Francisco takes in a view of the city.

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Credit: Tali Caspi, UC Davis

As their traditional dining options dwindle and natural areas give way to restaurants, homes and sidewalks, the coyotes of San Francisco are shifting what they eat.

Scientists from the University of California, Davis, wanted to understand what San Francisco’s coyotes are eating, and how their diet is changed and shaped by the city’s landscape, which can vary from block to block.

Their study, published in the journal Ecosphere, found that the number of restaurants and amount of pavement or “impervious surfaces” within the city heavily influenced what the coyotes ate. Coyote consumption of rats was highest where restaurant density was highest, and consumption of human-sourced food was highest in the most heavily paved parts of the city.

The findings can help inform and prioritize management strategies to protect native coyotes and reduce human-wildlife conflicts.

What San Francisco’s coyotes are eating

So what are coyotes eating in San Francisco? 

“A lot of human-provided food,” said lead author Tali Caspi, a Ph.D. candidate with the UC Davis Department of Environmental Science and Policy and with the UC Davis School of Veterinary Medicine’s Mammalian Ecology and Conservation Unit (MECU). “Chicken is a really big diet item; we found it in 72% of the scat samples analyzed in the study.”

However, a natural prey source, pocket gophers, comprised the next most popular food source, found in about 57% of the scats collected, followed by pig (human-sourced) and racoon (natural). While some people have expressed concern about coyotes eating cats, felines were rare in the dietary analysis, detected in 4.5% of samples. 

Scat and DNA analysis

To reach their findings, the authors collected more than 700 coyote scat samples from throughout San Francisco between September 2019 and April 2022. They brought them to UC Davis for lab analyses at MECU, within the Veterinary Genetics Laboratory. Genotyping matched fecal samples to individual coyotes, while DNA metabarcoding quantified diet composition.

Caspi notes that while the analysis reveals food sources, it does not differentiate among, for example, a backyard chicken, takeout from a dumpster, or chicken found in pet food. 

The research also showed that coyotes in more urbanized parts of the city, such as Telegraph Hill near Coit Tower or Bernal Hill, ate more human-sourced food than coyote neighbors with more green space, such as in the Presidio or Golden Gate Park.

The scientists also observed that diets among coyote family groups were highly varied, while diets among members of the same family varied little. 

 “This study highlights the huge range of dietary and habitat affinities of coyotes as a species,” said senior author Ben Sacks, director of the MECU at UC Davis. “ That is a trait for which they are already well-known, but the study also joins a growing body of evidence pointing to relatively narrow proclivities of coyotes as individuals. They tend to stick with what they know.” 

Living among coyotes

Coyotes are native to San Francisco. Extirpated in the early 1900s, they returned in the early 2000s and now share space with more than 870,000 people on 47 square miles — the second-most densely populated major city in the United States — with water on three sides. 

There are many things people can do to respectfully share space with coyotes and reduce human-wildlife conflict. This includes keeping cats indoors, not leaving pet food outside, securely disposing food waste and, perhaps most importantly: “Don’t feed coyotes,” Caspi said. “There’s a misconception that coyotes are starving and need our help finding food in San Francisco, and clearly they don’t.”

Coping with urban life

From song sparrows in Portland, Oregon varying their song frequencies to cockatoos in Australia opening trash cans, the study joins the body of literature showing behavioral differences within cities among the same species.

“There are a lot of different ways to survive city life as an animal,” Caspi said. “It speaks to the plasticity and resilience of these species to see all of these different strategies for coping with urban life.”

Additional coauthors include Monica Serrano and Stevi Vanderzwan of UC Davis, independent researcher Janet Kessler, and Christopher Schell of UC Berkeley.

The study was funded by a Christine Stevens Wildlife Award from the Animal Welfare Institute, the UC Davis Center for Community and Citizen Science, and additional supporting grants from UC Davis and UC Berkeley. Caspi also acknowledged the contributions of community scientists via iNaturalist. The online network helped lead her to fresh scat samples and even helped her trace a rare lab analysis of fin whale in a coyote’s diet to a nearby beached fin whale recorded on the app.

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Coyotes, native to San Francisco, rest and play at a park in the city. 

A coyote sits in the grass in San Francisco.

Credit

Tali Caspi/UC Davis

UC Davis urban ecology Ph.D. Candidate Tali Caspi collects coyote scat in San Francisco. 

Credit

Gayle Laird / California Academy of Sciences

Journal

Ecosphere

DOI

10.1002/ECS2.70152 

Article Title

Impervious surface cover and number of restaurants shape diet variation in an urban carnivore

Article Publication Date

21-Jan-2025