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Two More Odd Things I Just Learned About Fish

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When I'm not blogging for mental_floss, I can usually be found wearing bright orange rubber pants and gutting, cutting and selling fish at my local Whole Foods (and winning awards for it). Sometimes, my two worlds collide and I find some scientific research involving my ocean-dwelling friends that begs for a blog post. This is one of those times.


1. Dying Zebrafish Give Their Kids a Powerup
Many animals give off biochemical signals when they're frightened or hurt to warn other members of the species of danger and elicit anti-predator and defensive behavior. The effects of these "alarm substances" on juvenile and adult animals have been the subject of many studies, but researchers at the Marine Biology and Ecology Research Center at the University of Plymouth wanted to know how embryos still in the early stages of development would respond to the substances. [1]

Embryos of two species (Danio albolineatus and D. rerio) of zebrafish, tropical freshwater members of the minnow family native to southeastern Himalayan region, were exposed to skin injury-induced alarm substances from adults of the species and filmed during development. The development time of both species was sped up, and alarm substance-exposed embryos reached their first muscular contractions (D. rerio) and their first heartbeats (D. rerio and D. albolineatus) earlier than control embryos.

The exposure to the alarm substance caused the embryos to developed a functional heartbeat almost 10%, or 1.5 to 2 hours, faster than normal. That might seem like a snail's pace to us, but after fertilization, zebrafish develop precursors to all the major organs within 36 hours, hatch within 48 hours and begin swimming and feeding within 72 hours. Speeding up development by even just an hour reduces the time the embryos are vulnerable in their egg case and possibly not under the guard of their parents.

How will these developmental advances affect the fish later in life? The researchers think they could either be a sign of an increased development rate overall (with the fish rushing through all their developmental stages), or they could relate to later physiological or behavioral traits.

2. Stingrays Are Smarter Than They Look
rayFreshwater stingrays, the tropical river-dwelling relatives of ocean-going stingrays, have, like sharks and other cartilaginous fish, long been thought of as reflexive machines without cognitive capacity and ability (in part because they're difficult to study). Well, we owe them an apology, because they recently joined a very special club: the royal order of animals that use tools.


In an experiment, researchers from the Hebrew University of Jerusalem in Israel designed a plastic tube test apparatus with two openings and placed a piece of food in it.[2] All five of their stingray subjects (Potamotrygon castexi) figured out how to get the food out of the tube with a carefully directed jet of water (which meets the basic definition of a tool), the first indication of tool use in the batoid fishes. That's one small step for understanding the evolutionary origins of cognitive function in higher vertebrates and one giant leap for raykind. Congrats, guys.

[1] S. Mourabit, S. D. Rundle, J. I. Spicer and K. A. Sloman. "Alarm substance from adult zebrafish alters early embryonic development in offspring." Biology Letters. DOI:10.1098/rsbl.2009.0944

[2] M. J. Kuba, R. A. Byrne and G. M. Burghardt."A new method for studying problem solving and tool use in stingrays." Animal Cognition. DOI: 10.1007/s10071-009-0301-5

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FRED TANNEAU/AFP/Getty Images
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Animals
Fisherman Catches Rare Blue Lobster, Donates It to Science
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FRED TANNEAU/AFP/Getty Images

Live lobsters caught off the New England coast are typically brown, olive-green, or gray—which is why one New Hampshire fisherman was stunned when he snagged a blue one in mid-July.

As The Independent reports, Greg Ward, from Rye, New Hampshire, discovered the unusual lobster while examining his catch near the New Hampshire-Maine border. Ward initially thought the pale crustacean was an albino lobster, which some experts estimate to be a one-in-100-million discovery. However, a closer inspection revealed that the lobster's hard shell was blue and cream.

"This one was not all the way white and not all the way blue," Ward told The Portsmouth Herald. "I've never seen anything like it."

While not as rare as an albino lobster, blue lobsters are still a famously elusive catch: It's said that the odds of their occurrence are an estimated one in two million, although nobody knows the exact numbers.

Instead of eating the blue lobster, Ward decided to donate it to the Seacoast Science Center in Rye. There, it will be studied and displayed in a lobster tank with other unusually colored critters, including a second blue lobster, a bright orange lobster, and a calico-spotted lobster.

[h/t The Telegraph]

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Courtesy Murdoch University
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Australian Scientists Discover First New Species of Sunfish in 125 Years
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Courtesy Murdoch University

Scientists have pinpointed a whole new species of the largest bony fish in the world, the massive sunfish, as we learned from Smithsonian magazine. It's the first new species of sunfish proposed in more than 125 years.

As the researchers report in the Zoological Journal of the Linnean Society, the genetic differences between the newly named hoodwinker sunfish (Mola tecta) and its other sunfish brethren was confirmed by data on 27 different samples of the species collected over the course of three years. Since sunfish are so massive—the biggest can weigh as much as 5000 pounds—they pose a challenge to preserve and store, even for museums with large research collections. Lead author Marianne Nyegaard of Murdoch University in Australia traveled thousands of miles to find and collected genetic data on sunfish stranded on beaches. At one point, she was asked if she would be bringing her own crane to collect one.

Nyegaard also went back through scientific literature dating back to the 1500s, sorting through descriptions of sea monsters and mermen to see if any of the documentation sounded like observations of the hoodwinker. "We retraced the steps of early naturalists and taxonomists to understand how such a large fish could have evaded discovery all this time," she said in a press statement. "Overall, we felt science had been repeatedly tricked by this cheeky species, which is why we named it the 'hoodwinker.'"

Japanese researchers first detected genetic differences between previously known sunfish and a new, unknown species 10 years ago, and this confirms the existence of a whole different type from species like the Mola mola or Mola ramsayi.

Mola tecta looks a little different from other sunfish, with a more slender body. As it grows, it doesn't develop the protruding snout or bumps that other sunfish exhibit. Similarly to the others, though, it can reach a length of 8 feet or more. 

Based on the stomach contents of some of the specimens studied, the hoodwinker likely feeds on salps, a jellyfish-like creature that it probably chomps on (yes, sunfish have teeth) during deep dives. The species has been found near New Zealand, Australia, South Africa, and southern Chile.

[h/t Smithsonian]

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