SCUBA News 238
(ISSN 1476-8011)

SCUBA News (ISSN 1476-8011)
Issue 238 - April 2020

Hello. Thank you for continuing to subscribe in these difficult times. Diving is pretty much cancelled around the world but the dive operators and liveboards are rising to the challenge and changing their booking conditions to help their customers. For example, pay no deposit and cancel for free for 60 days on liveaboards booked via Divebooker. There are also many great deals around at the moment.

Be very careful though if you have had coronavirus. There may be lasting damage to your lungs so have a diving medical before going back in the water. The good news is, that according to John Hopkins University, your lungs can recover. However, it takes from three months to a year for lung function to return to pre-COVID-19 levels.

Keep safe and well.

What's new at SCUBA Travel?
Creature of the Month: Ragged-Tooth Shark
Diving news from around the World
Download as a pdf file

AquaMarine Diving - Bali

AquaMarine Diving - Bali
10% off published prices, free rental gear and an AquaMarine Goodie-Bundle when you use code ScubaTravelUK2020 at

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What's New at SCUBA Travel?


Greek Island Diving

Scuba diver's guide to the Greek Islands. Which one to choose?


Where to dive in Antigua

The best diving in Antigua is in the south of the island, around English Harbour. The north is shallow and quite sandy, but calm and good for beginners.

Creature of the Month: Marine Flatworm, Pseudocerotidae

Flatworms are very interesting animals. Looking very similar to nudibranchs: they are beautifully coloured, the same shape and may move similarly by muscular propulsion. However, they have thinner bodies than nudibranchs and also move by beating hair-like cilia on their undersides - rippling through the water. Some have short tentacles on their heads.

Polyclad flatworm - Pseudoceros sp. Photo credit: Mike Keggen, taken on the Ghiannis D, Red Sea
Polyclad flatworm. Photo credit: Mike Keggen

Flatworms are bilaterally symmetrical animals. The left and right sides of the animal are the same but the underneath and top are different. This is common in higher animals, but flatworms are one of the most simple creatures to exhibit this.

Their eyes are tiny, comprising just 2 to 3 cells. There are hundreds of eyes along the sides of the body, distinguishing between light and dark and determining the direction of light. They have two other types of sensors. One is sensitive to chemical stimuli, perceiving far-off substances and sensing them on contact (smell and taste). Another is stimulated by the passage of water over the flatworm's body and perceived by rheotactic sensors. The flatworm's simple brain can interpret information and even has the capacity to learn.

Yellow papillae flatworm (Thysanozoon nigropapillosum) swimming at 12 m, Manta Ray Bay, Yap, Federated States of Micronesia
Yellow papillae flatworm (Thysanozoon nigropapillosum). Photo credit: Betty Wills (Atsme), Wikimedia Commons, License CC-BY-SA 4.0

Like nudibranchs, some flatworms utilise nematocysts - the stinging cells they obtain when eating fire coral or other hydroids. These are not digested but passed to the body wall as a form of defense.

Mobile flatworms are carnivorous, and feed on slow-moving, sedentary or dead animals. Many capture living prey by wrapping themselves around it, entangling it in slime and pinning it to the ground. A few species may stab their prey with their penis!

Flatworms have amazing regenerative capabilities. When cut into a number of pieces, each will develop a head, tail and full complement of organs.

Although common, divers rarely see flatworms as they hide under rocks, dead coral or seaweed. When spotted they are often mistaken for nudibranchs. Look carefully at these amazing animals - the nudibranch you've seen may not be a nudibranch at all.

Further Reading
Coral Reef Guide Red Sea, by Robert Myers and Ewald Lieske, ISBN 0-0071-5986-2
Invertebrate Zoology, by Robert D Barnes, Harcourt Publishers Ltd, ISBN 0-0302-6668-8
Great British Marine Animals, by Paul Naylor, Deltor (2011), ISBN 0-9522831-3-1
Jacques Cousteau: The Ocean World, by Jacques Cousteau, Abradale Press, ISBN 0-8109-8068-1
The Red Sea in Egypt Part II, Invertebrates, by Farid S Atiya, Elias Modern Printing House, 1994, ISBN 977-00-6697-4

Read more Creatures of the Month.

Diving News From Around the World

Our round up of the best underwater news stories of the past month. For breaking news see our Twitter page or RSS feed

Scuba full face mask turned into a ventilator

RAID diving agency makes e-learning free to access
SCUBA diving courses now free from RAID. Download all the course materials you need.

Nudibranch photo

Underwater Photography Guide announces Safe Under the Sea Competition
The Underwater Photography Guide is hosting a special underwater photo competition to bring people together, encourage artistic expression, and raise money to help fight Coronavirus.

Tranquil whales

Silence is golden for whales as lockdown reduces ocean noise
Curtailing of shipping due to coronavirus allows scientists to study effects of quieter oceans on marine wildlife

Menhaden fish

With Boats Stuck in Harbour Because of COVID-19, Will Fish Bounce Back?
The pandemic has left many unable to leave harbour, creating a window for fishing grounds to recover from years of overfishing

Whale shark

How old are whale sharks? Nuclear bomb legacy reveals their age
Nuclear bomb tests during the Cold War in the 1950s and 1960s have helped scientists accurately estimate the age of whale sharks, the biggest fish in the seas.

Map of invasive species in the Med

For the Mediterranean, the Suez is a wormhole bringing in alien invaders
An influx of Indo-Pacific species has invaded the Mediterranean Sea via the Suez Canal, changing the sea's ecology and threatening the region's fisheries. Climate change is amplifying the invasion by stressing endemic populations and creating new space for invasive species.

Recovering coral reef

Warming climate undoes decades of knowledge of marine protected areas
Climate change and warming seas are transforming tropical coral reefs and undoing decades of knowledge about how to protect these delicate and vital ecosystems.

Icelandic Whaling Ship

Iceland won't be killing any whales this year
Icelandic whalers cite financial difficulties and stiff competition with Japan.

underwater robot

Enhanced underwater robots can boost ocean discoveries
Underwater robots are regularly used by the oil and gas industry to inspect and maintain offshore structures. The same machines could be adapted to gather extra scientific information, thus boosting both environmental and resource management capabilities.

SCUBA News is licensed under a Creative Commons Attribution 4.0 Unported License. This means we are happy for you to reuse our material for both commercial and non-commercial use as long as you: credit the name of the author, link back to the SCUBA Travel website and say if you have made any changes. Some of the photos though, might be copyright the photographer. If in doubt please get in touch.

Photo credits: Tim Nicholson, Jill Studholme, Kristin Riser, Jianye Sui

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