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Damselfish Can Recognize Each Other’s Faces Using UV Vision

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One fish, two fish, red fish, blue fish; in general, all fish of a species look the same to humans. Surprisingly, however, research shows that the individuals in at least once species of fish have no trouble telling each other apart. According to experiments undertaken by researchers at the University of Queensland, Australia, the Ambon damselfish, or Pomacentrus ambionensis, possesses the capacity for facial recognition—ordinary among humans, but unique and undiscovered in fish until now.

Recently presented at an academic conference in Australia, the research, led by marine scientist Ulrike Siebeck, builds on Siebeck's own prior investigation into the damselfish’s ability to recognize the shape of ultraviolet patterns that distinguish one fish species from another. A 2010 experiment found that the damselfish relied on its ultraviolet (UV) sight to determine which particular species of fish was intruding on its territory, and thereby whether or not that particular fish’s presence necessitated an attack. When the damselfish were prevented from recognizing the intruding fish’s UV facial pattern, they were effectively blinded, unable to identify their preferred prey.

This new study finds that the damselfish is capable of even more nuanced facial recognition than previously thought, involving not just making distinctions between different species, but between individual fish as well. Captive damselfish were trained to recognize a given UV facial pattern, reinforced by a food reward. When presented with the familiar face and a strange new face, the Ambon damselfish were able to identify the correct fish face with 75 percent accuracy, a pattern that held true even when the faces were those of a similar but different species, the lemon damselfish.

The Ambon damselfish was even able to recognize the same face when it was blended with other photographs of fish faces to create totally new images, demonstrating a truly impressive sense of feature recognition—and all based on patterns of UV light invisible to the human eye.

While it may seem like a limitation of the damselfish’s ability that its pattern recognition relies solely on ultraviolet patterns, rather than facial topography or other physical identifying features, it is actually a characteristic that may help them survive in the coral reefs of the Western Pacific Ocean. Just as the human researchers were unable to see the ultraviolet patterns their subjects saw without technological assistance, the damselfish’s predators are UV blind. In this way, the damselfish’s ultraviolet sight functions as a superpower of sorts, so that their facial patterns and the ability to recognize them allow the damselfish to “communicate secretly,” Siebeck theorizes

[h/t National Geographic]

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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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science
Are Sex, Drugs, and Rock 'n' Roll Really Linked? Researchers Investigate
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Around the world, sex, drugs, and rock 'n' roll are said to go hand-in-hand. But do they? As PsyPost reports, a pair of Pennsylvania psychologists recently dove into the empirical evidence tying the three together, asking college students to talk about their drug use, sex lives, and music preferences and talents to suss out whether people who play and enjoy rock music really do have more active sex lives and drug use.

Published in the journal Human Ethnology Bulletin, the study [PDF] of 467 students relied on self-reporting, which isn't typically the most reliable evidence—people are wont to exaggerate how often they've had sex, for instance—but the survey also asked them about their desires, posing questions like "If you could, how frequently would you have sex?" It also asked about how often the students drank and what drugs they had tried in their lifetimes. They also described their musical experience and what kind of music they listened to.

The results were mixed, but the researchers identified a relationship between liking faster, "harder" music and having more sex and doing more drugs. Acoustic indie rock aficionados weren't getting quite as wild as heavy metal fans. High-tempo-music lovers were more likely to have taken hallucinogenic drugs like LSD, for example, and tended to have had more sexual partners in the previous year than people who favored slower types of music. According to the study, previous research has found that attention-seeking people are more likely to enjoy "hard" music.

The study didn't have a diverse enough group either in age or in ethnicity to really begin to make sweeping generalizations about humans, especially since college students (the participants were between 18 and 25) tend to engage in more risky behaviors in general. But this could lay the groundwork for future research into the topic. Until then, it might be more accurate to change the phrase to "sex, drugs, and heavy metal."

[h/t PsyPost]

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