8 Things You Probably Didn't Know About the Seadevil Anglerfish

By now, you've probably seen the awesome footage of a Black Seadevil anglerfish captured by scientists with the Monterey Bay Aquarium Research Institute (if not, you can watch it above). The video, shot at 1900 feet below the surface by a remotely operated vehicle, is believed to be the first footage of a live Seadevil in its natural habitat. Because the creatures live at such great depths, they're rarely seen alive—and, because of that, we don't know a whole lot about them. We asked John Sparks, a curator in the American Museum of Natural History's Department of Ichthyology, to tell us a few things scientists do know about this weird fish.

1. There are six species in the Melanocetidae, or Black Seadevil, family. This one is a female, "probably the Humpback Anglerfish," Sparks says. The fish was first described by Albert Günther, keeper of zoology at the British Museum in London, in 1864. He had obtained it from English naturalist James Yates Johnson, who had gotten the fish from Madeira [PDF]—hence its scientific name, Melanocetus johnsonii.

2. You may have heard how some anglerfish reproduce via the males fusing their bodies to the females' until they essentially become one; the male loses his eyes, fins, teeth, and some internal organs and, from that point forward, lives off of the female, providing sperm when she's ready to spawn. Those fish "are members of the suborder Ceratioidei, [or] deep sea anglerfishes, in which some species are known to reproduce by that means," Sparks says. Still, that's not the norm for those fish—scientists have so far only found parasitic males in 5 of 11 ceratioid families, according to Sparks—and it's probably not what happens when humpback anglerfish mate, either. "That has not been found—yet—in this species," Sparks says. "In the family this species belongs to, only loosely attached, non-parasitic, males have been found on females—they still retain their teeth, etc."

3. The females are much bigger than the males. Typically, Sparks says, this species is "3 to 3 1/2 inches [long]. The largest male known is under 3 centimeters (1.18 inches), whereas the largest female is 18 centimeters (7.08 inches)."

A sketch of the Humpback Anglerfish from the 1896 book Oceanic ichthyology : a treatise on the deep-sea and pelagic fishes of the world, based chiefly upon the collections made by the steamers "Blake," "Albatross," and "Fishhawk" in the northwestern Atlantic. Photo courtesy the Biodiversity Library on Flickr.

4. The tip of the pole-looking thing protruding from the fish's head is called the esca, and its bioluminescence is produced by symbiotic bacteria. This is key in getting the anglerfish fed, because it isn't built for giving chase. "[It's] just swimming slowly, as their body shape—globular—dictates," Sparks says. So in dark environments, the fish uses the glowing esca, which it can move to emulate prey, to attract its own prey, and—in a classic case of the hunter becoming the hunted—chomps down on whatever gets too close...

5. ... with those crazy-looking teeth. "They are sharp and [are] used to impale prey items," Sparks says. "They have large mouths and can eat quite large prey items." Günther, in his description of Melanocetus johnsonii, notes that

The gape is enormous; and although the lower jaw is vertical when the mouth is closed, it can be moved downwards at more than a right angle ... the prey which can be received within the cavity of the mouth actually may exceed the size of the fish itself.

When the specimen was brought to him, Günther said, "the belly was much distended, and contained, rolled up spirally into a ball, a Scopeline fish, which measured 7 1/2 inches in length, and 1 inch in depth."

6. The video mentions the dots on the anglerfish's face, which are organs that allow it to sense movement in the water. These, Sparks says, are called neuromasts, and they're "part of the lateral line system. Agnathans, or jawless fishes, up through amphibians have them. They are for sensing pressure (water movement)—in some species, such as cavefishes, they are quite numerous and well developed."

7. AMNH has the Humpback Anglerfish in its Ichthyology collection. "It's probably the most commonly captured member of Melanocetidae," Sparks says. "It has a wide distribution and is found in all oceans."

8. Though this probably wasn't the anglerfish seen in Finding Nemo—"If I remember correctly the 'species' depicted in Nemo was far more elongate; [it] seemed to me to be an amalgam of different species," Sparks says—the humpback anglerfish is still a star: It once appeared on the cover of Time.

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.
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There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

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