Tuesday, 31 October 2017

A Heteropod as art work?

Puerto Profundo has been the divesite in Chile we most wanted to return to. So far, on our two dives, it has not disappointed us - we've been able to see and photograph nearly all of our favourite species from 2007 and 2009.

The amazing-looking sea creature pictured is in the jellyfish family. It comes to us directly from the Pacific Ocean which is not far away. It seems to be a heteropod. We only know this because nearly 20 years ago we bought a book entitled 'Pacific Coast Pelagic Invertebrates' (Wrobel and Smith). From photos in the book we decided that the animal most closely resembles a carinaria cristata.

Jellyfish have come to have an undeservedly bad name - partly through TV programs like the 'Friends' episode in which Joey has to pee on Rachel when she gets stung by an un-named species of jellyfish. In 1998 when this book was published, it included photos of well over 100 different species and the authors stated 'we could not include all of the gelatinous animals from this region' (California up to Alaska). The authors address Rachel's problem: 'Jellies are often treated as a scourge, deadly creatures that should be avoided due to their venomous sting. In reality, gelatinous animals are among the most beautiful and stunning animals of the sea. Although a few types may present some danger to people, most are harmless.'
The most common jellyfish we terrestrial animals see are the moon jellyfish … hydromedusa. You can see them when they float into Bay areas - seemingly in their thousands - at the whim of currents bringing them in from the open sea.

We have also often seen hordes of physalia (Portuguese Man of War) offshore. They CAN sting you - and they do sometimes arrive on beaches. Usually warnings are posted by authorities, as in Australia where beaches with warnings about the dangerous 'Box' jellyfish (whose venom could kill you) should be avoided.
When you see moon or other jellyfish, you're advised to avoid picking them up especially if you notice red cells - these only occur during the breeding season. If you do feel a sting, you should avoid itching the area or apply some ice wrapped in a towel. Rubbing alcohol, fresh water and pee are not useful solutions as they will just encourage the activation of more nematocysts. A nematocyst is a tiny barb which can be affected by mechanical or chemical stimuli to fire into the epidermis of the prey. Divers in cold water (the water here is at 8C, 48F) are wearing divesuits of some kind (we have drysuits) so we would never feel the effects unless they touch some uncovered area of our faces.

Gelatinous animals can be beautiful to watch in the proper setting. If you're able to see an aquarium containing moon jellyfish, there are often crowds watching - mesmerized by the graceful movements of these animals as they're carried along by invisible currents. There's a story that in Japan, instead of having artwork or a television, some people have aquariums full of moon jellyfish. If true, we could all learn from this - it would be soothing to watch these harmless and beautiful creatures instead of worrying about North Korea and watching TV News.

It's impossible for us to collect specimens of this very rarely seen animal which Larry has photographed. I doubt that even Japanese millionaires could keep them as pets or replacements for artwork. That's because they cannot survive in standard aquariums. At the Vancouver Aquarium, a special system continuously brings fresh seawater directly in and out plus more machinery is needed to simulate water motion without also sucking the jellyfish out of the tank. The animals are delicate and consist of 95% water. Even if we had permission and the right equipment for collecting them, we could fatally injure them trying to scoop them up and out of the water.

Our book has taught us about the parts of the animal. At the very top of the creature is its mouth. It's been feeding on a sea whip - a 'convexella magelhaenica'. You can see that the lower part has been completely eaten away. This is another cannibalistic action as both animals belong to the class Cnidaria - but although the whip also has stinging cells, it can't fight back with its largely ineffectual nematocysts. Supposedly there are eyes, sucker, radula (a tooth-like apparatus which it's using to scrape away at the sea whip) and tentacle up near the mouth - none of which I could make out in the photo. The gorgeous long swooping diaphanous part is the tail, and the yellowish structures within it are the guts, gills, the penis and a vestigial shell - all of which I find difficult to identify individually. Perhaps with a higher resolution photo, you'll be able to see these parts.

**Please note that we have appreciated comments on our blog, but we're not able to respond to them while we're away on this trip.

At 2017-10-31 11:07 (utc) our position was 52°40.45'S 073°45.74'W

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