Marine Life & Conservation
Seahorses stalk their prey by stealth
Photo: Brad Gemmell
Seahorses may appear slow and awkward but they are ferocious and ingenious predators, according to a new study.
The beautiful creatures are famously bad swimmers, but they have a secret weapon to sneak up on their prey.
Their peculiar snouts are shaped to create very few ripples in the water, effectively cloaking them as they creep up and pounce on tiny crustaceans.
To their victims, seahorses are more like sea monsters, say scientists from the University of Texas at Austin.
“The seahorse is one the slowest swimming fish we know of, but it’s able to capture prey that swim at incredible speeds,” said Brad Gemmell, author of the study in Nature Communications.
The prey, in this case, are copepods – extremely small crustaceans that are a favoured meal of seahorses, pipefish and sea dragons (Syngnathidae).
When copepods detect waves from predators, they jolt away at speeds of more than 500 body lengths per second – the equivalent of a 6-foot human swimming at 2,000 mph.
“Seahorses can overcome one of the most talented escape artists in the aquatic world,” said Dr Gemmell.
“In calm conditions, they catch their intended prey 90% of the time. That’s extremely high, and we wanted to know why.”
Seahorses dine by a method known as pivot feeding. Their arched necks act as a spring – allowing them to rapidly rotate their heads and suck their prey in.
But this suction only works at short distances. The effective strike range for seahorses is about 1mm. And a strike happens in less than 1 millisecond.
Until now, it was a mystery how such apparently docile creatures managed to get close enough to their prey without being spotted.
To find out, Dr Gemmell and his colleagues studied the dwarf seahorse, Hippocampus zosterae, which is native to the Bahamas and the US.
They filmed the movement of water around the fish in 3D using holography – a technique where a microscope is fitted with a laser and a high-speed digital camera.
They found that the seahorse’s snout is shaped to minimise the disturbance of water in front of its mouth before it strikes.
Above and in front of its nostrils is a “no wake zone” and it angles its head precisely to attack its prey.
Other small fish with blunter heads, such as the three-spine stickleback, have no such advantage, the researchers found.
“It’s like an arms race between predator and prey, and the seahorse has developed a good method for getting close enough so that their striking distance is very short,” said Dr Gemmell.
“People don’t often think of seahorses as amazing predators, but they really are.”
Source: www.bbc.co.uk/news
Into the Great Wide Ocean: Life in the Least Known Habitat on Earth by Sonke Johnsen
What an unexpected surprise! A book that combines a clear passion for the ocean with humour and the deft touch of a true storyteller. Johnsen gives a wonderful insight into the life of a deep sea marine biologist , the weird and wonderful animals encountered in this mysterious world, the trials and tribulations, in a way that makes you feel you have been sat at a table chatting about his work over a pint or cup of tea.
Even for divers, the deep blue open ocean can feel inaccessible. It is one of the least studied places in the universe. In this book that deep blue ocean and its inhabitants is brought to you with warmth and wit. And even the most well-read will come away with new facts and information. Johnsen’s goal is one that resonates throughout: Before we as scientists can ask people to preserve this important and fragile habitat, we need to show them that it’s there and the beauty of what lives in it. He does just that.
This is a book that combines the scientific with a deeply personal story. You feel what it is like to work out in the open ocean and get to know the animals that reside there. With descriptions that allow you to really imagine what it feels like being out there in the blue.
What the publisher says:
The open ocean, far from the shore and miles above the seafloor, is a vast and formidable habitat that is home to the most abundant life on our planet, from giant squid and jellyfish to anglerfish with bioluminescent lures that draw prey into their toothy mouths. Into the Great Wide Ocean takes readers inside the peculiar world of the seagoing scientists who are providing tantalizing new insights into how the animals of the open ocean solve the problems of their existence.
Sönke Johnsen vividly describes how life in the water column of the open sea contends with a host of environmental challenges, such as gravity, movement, the absence of light, pressure that could crush a truck, catching food while not becoming food, finding a mate, raising young, and forming communities. He interweaves stories about the joys and hardships of the scientists who explore this beautiful and mysterious realm, which is under threat from human activity and rapidly changing before our eyes.
Into the Great Wide Ocean presents the sea and its inhabitants as you have never seen them before and reminds us that the rules of survival in the open ocean, though they may seem strange to us, are the primary rules of life on Earth.
About the Author:
Sönke Johnsen is professor of biology at Duke University. He is the author of The Optics of Life: A Biologist’s Guide to Light in Nature and the coauthor of Visual Ecology (both Princeton). Marlin Peterson, who created original illustrations for this book, is an illustrator and muralist who teaches and illustrates in many styles and media. He also specializes in giant optical illusions such as his harvestmen mural below the Space Needle in Seattle, and his full portfolio can be found at marlinpeterson.com.
Book Details
Publisher: Princeton University Press
Hardcover
Price: £20.00
ISBN: 9780691181745
Published: 7th January, 2025
This week only – your donation to the Shark Trust will be doubled – at no extra cost to you!
This week only – your donation to the Shark Trust will be doubled – at no extra cost to you!The Shark Trust are raising vital funds for their Community Engagement Programme: empowering people to learn about sharks and rays, assisting the scientific community take action for elasmobranchs, and bring communities together to become ambassadors for change.
Every £1 you give = £2 for shark conservation. A donation of £10 becomes £20, £50 becomes £100! Help us reach our target of £10,000, if successful, this will be doubled to £20,000 by the Big Give.
Every donation makes DOUBLE the impact!
Monty Halls is backing this week of fundraising “Cousteau called sharks the “splendid savage of the sea”, and even through the more benign lens of modern shark interactions it remains a good description. The reefs I dived thirty years ago teemed with sharks, the perfect result of 450 million years of evolution. Today those same reefs are silent, the blue water empty of those elegant shadows. But hope remains that if one generation has created such devastation, so the next can reverse the damage that has been done. The Shark Trust are at the forefront of that fight.“
To find out more about the work of the Shark Trust visit their website here.
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