SCUBA News 236
22 February 2020
SCUBA News (ISSN 1476-8011)
Issue 236 - February 2020
Welcome to SCUBA News. You can download a pdf version of the newsletter here.
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.
Discover the best scuba diving in Costa Rica, including the stunning Cocos Islands - guide to dive sites, operators and liveaboards.
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.
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.
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.
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.
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.
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
Save up to 25% on trips to the Cayman Islands
For sharks, turtles, stingrays, as well as famous Cayman wrecks like the Kittiwake and Doc Polson.
Urgently needed protection granted to Oceanic Whitetip Shark.
Coronavirus Impacts Pacific Island Divers
Asia Dive Expo Postponed
Sex-changing fish recover more slowly from over-fishing
Grey seals discovered clapping underwater to communicate
Earthquakes can make it harder for whales to find food, first-ever study says
Study connects marine heat wave with spike in whale entanglements
New study shows Deepwater Horizon oil spill larger than previously thought
Mini device analyses ocean microbes
Microbes reflect the health of coral reefs
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
Previous editions of SCUBA News are archived at https://www.scubatravel.co.uk/news.html
SUBSCRIBING AND UNSUBSCRIBING
Visit [UNSUBSCRIBE] and add or remove your e-mail address. To change whether your receive the newsletter in text or HTML (with pictures) format visit [PREFERENCES]
Should you wish to advertise in SCUBA News, please see the special offers at
Other advertising opportunities are at
CONTACTING THE EDITOR
Please send your letters or press releases to:
SCUBA Travel Ltd, 5 Loxford Court, Hulme, Manchester, M15 6AF, UK
Subscribe To SCUBA News
Our newsletter, SCUBA News (ISSN 1476-8011), is absolutely free. It is a monthly publication, delivered by e-mail. To receive your copy fill in your details below. We will never pass your e-mail address to any third parties, or send you unsolicited e-mail.
You will receive an e-mail confirming your subscription. If you don't receive this you may have entered your e-mail address incorrectly - revisit this page and re-subscribe.