SCUBA News 236
(ISSN 1476-8011)

SCUBA News (ISSN 1476-8011)
Issue 236 - February 2020

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What's new at SCUBA Travel?
Creature of the Month: Flabellina affinis nudibranch
Featured Liveaboard: Cayman Aggressor
Diving news from around the World

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What's New at SCUBA Travel?

Dakota wreck

Turkey from Below

Ten types of whale and dolphin, four seas and hundreds of wrecks - find out more about what Turkey has to offer underwater.

Whale shark in Madagascar

Magical Madagascar

The country is famous for her unique land animals, but her seas are also full of life not found anywhere else. Humpback whales and whale sharks are also regular visitors.


Spectacular Costa Rica

Discover the best scuba diving in Costa Rica, including the stunning Cocos Islands - guide to dive sites, operators and liveaboards.

Creature of the Month: Flabellina affinis Nudibranch

Found in the Mediterranean, on the Atlantic coast of France, Spain and Portugal, and in the Canary Islands. This pretty purple nudibranch grows to 5 cm long and feeds on hydroids. Not just any hydroids but only those in the Eudendrium genus like the ones in the photo.

Flabellina affinis nudibranch feeding on Eudendrium hydroid by Tim Nicholson
Photo credit: Tim Nicholson

Hydroids capture and eat plankton, and the nudibranchs prefer to feed when the hydroids have just captured their prey. This means they get energy both from the hydroid and from their newly captured meal. This could have the result that they need to eat less hydroids to survive, so the hydroid colony lives longer and thus provides more food for the nudibranch.

Flabellina affinis nudibranch by Tim Nicholson
Photo credit: Tim Nicholson

Hydroids have stinging cells. When they fire these nematocysts they should harm the nudibranch. How does F. affinis live and feed on the hydroids without any apparent discomfort? They releases masses of chitin granules which surround the stinging nematocysts and defend the animal from the hydroids tentacles.

Flabellina affinis nudibranch taken in Spain by Tim Nicholson
Photo credit: Tim Nicholson

The nudibranchs take things a stage further. They can incorporate unfired nematocysts into the projections along their skin (called cerata), protecting the nudibranch against predators. An extension of the nudibranch's digestive system, the animals store the nematocysts in sacs at the cerata tips. When irritated or threatened, the Flabellina will curl its body and when in contact with a predator, specialised muscles will squeeze the nematocysts out of the cnidosacs.

These colourful outgrowths also make a big surface area for gas exchange in respiration.

Flabellina affinis nudibranch by Tim Nicholson
Photo credit: Tim Nicholson

If you look closely at the photo above, you can see the nudibranch's eye - the black dot below the rhinophores (the sticky-up tentacles with a corkscrew pattern). They can't see very well though, just discerning light and dark.

Flabellina affinis nudibranch by Tim Nicholson
Photo credit: Tim Nicholson

You can tell Flabellina affinis from other nudibranchs by the colour of its cerata. They have white tips and a violet band just below the tips which is opaque.

Animalia (Kingdom) > Mollusca (Phylum) > Gastropoda (Class) > Heterobranchia (Subclass) > Nudibranchia (Order) > Flabellinidae (Family) > Flabellina (Genus)

References and Further Reading
Trevor J. Willis et al. Kleptopredation: a mechanism to facilitate planktivory in a benthic mollusc. 13 Biol. Lett. 2017
Sea Slug Forum, Flabellina affinis

Photos copyright Tim Nicholson.

Read more Creatures of the Month.

Featured Liveaboard - Cayman Aggressor V

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Cayman Islands liveaboard

For sharks, turtles, stingrays, as well as famous Cayman wrecks like the Kittiwake and Doc Polson.

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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

Oceanic whitetip shark

Urgently needed protection granted to Oceanic Whitetip Shark.
Vital conservation win for the critically endangered Oceanic whitetip shark, Carcharhinus longimanus.

Pacific island beach

Coronavirus Impacts Pacific Island Divers
Diving island destinations are imposing new regulations on divers entering their countries who have visited anywhere else with confirmed incidents of coronavirus in the last fortnight.

Adex dates

Asia Dive Expo Postponed
Underwater360, the organiser of Asia Dive Expo (ADEX), has postponed the exhibition which was scheduled for April 17-19, 2020. This is due to the Coronavirus. New dates are 29-31 May.

Californian Sheephead

Sex-changing fish recover more slowly from over-fishing
People eat a lot of fish. Different sex-changing fish can follow several signals that prompt them to change sex. Some change from female to male at a fixed size or age. Often, fisheries will only harvest fish over a certain size. This means catching more males because they are usually bigger, which then skews the population towards female. Not enough males are then available to fertilise all the eggs produced by the females.

Grey Seal looking

Grey seals discovered clapping underwater to communicate
Marine mammals like whales and seals usually communicate vocally using calls and whistles. But a new study has discovered that wild grey seals can also clap their flippers underwater during the breeding season, as a show of strength that warns off competitors and advertises to potential mates.

Sperm Whales

Earthquakes can make it harder for whales to find food, first-ever study says
Earthquakes can disrupt sperm whales' ability to hunt for up to a year, according to the first-ever study to look at the effects of the tremors on marine mammals.

Humpback whale

Study connects marine heat wave with spike in whale entanglements
Entanglements of humpback whales in fishing gear along the US West Coast increased dramatically during the 2014 to 2016 marine heat wave known as the warm blob

Oil fire

New study shows Deepwater Horizon oil spill larger than previously thought
Toxic and invisible oil spread well beyond the known satellite footprint of the Deepwater Horizon oil spill, according to a new study

Analysing microbes to find health of reefs

Mini device analyses ocean microbes
device that can swiftly analyse microbes in oceans, revealing the health of these organisms.

coral reef

Microbes reflect the health of coral reefs
More microbes are found on healthier Cuban reefs than on human-impacted Florida reefs. Microorganisms play important roles in the health and protection of coral reefs, but exploring these roles can be difficult because of the lack of unspoiled reef systems throughout the global ocean.

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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