CHUPA SANGRE – The blood-sucking fiend

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Throughout my youth my family loved to spend summers on Catalan Bay beach. In those days the beach was couched between two rocky outcrops and I loved exploring the rock pools which formed during low tides. It was during this young and impressionable period that I was confronted with a horrifying organism called the ‘chupa sangre’, or blood sucker.

This fiend lived on the underside of rocks and sat waiting for unsuspecting children to brush up against it so it could suck their blood. I remember being told about this and even being challenged to touch one if I dared to question the perceived wisdom. Besides, the organism was a deep dark red colour and what else is like that other than blood?

This fearsome reputation encouraged hordes of young gullible children armed with wooden ice-cream sticks to carefully pick the horrors off the rocks, altruistically making the area safe for others. We were real life heroes and it felt great. Imagine my shock when I first learnt that the deadly chupa sangre was in fact a beadlet anemone.

As part of the phyla Cnidaria, beadlets are in fact animals which are closely related to corals and jellyfish. Anemones are non-calcifying solitary polyps with tentacles covered in stinging cells called nematocysts. Zoomed in, a nematocyst is like a spear on a spring and all Cnidarians have them which is why the phyla name translates to “stinging nettle”. The reason that some of these animals sting us and some don’t is fairly easy to explain; they ALL sting us. The difference is in the length of the spear in the nematocyst. If the length of the spear is longer than the depth of our skin then it can deliver its poison, we get stung and it swells and hurts. If the spear is shorter than the depth of our skin then we cannot be ‘stung’ and consequently you don’t feel anything at all. In all cases the tentacles stick to our skin because they are attempting to sting us. A beadlet’s sting cannot hurt us!

Beadlet anemones are veracious predators which will eat pretty much anything they can put their 192 tentacles on. They are known to take on more than they can consume, eventually being forced to spit out oversized food items. Typically though, their favourite food items include mussels, shrimps and crabs when they can get them. Otherwise they just waft their tentacles in the water column and capture any zooplankton which comes into contact with them.

Although they are considered sessile, anemones actually move around the rock surface to secure the best spot for feeding and for protection against constant wave action. Indeed, if they find themselves on an overcrowded rock they have the ability to drop off and reattach themselves at another less crowded site. They are also known to be highly territorial animals. Should their tentacle come into contact with another anemone which is not a direct relation, they embark on an assault which can last for weeks. The invader has no choice but to drop off the rock and find a less hostile spot.

Beadlets can reproduce sexually or asexually and are hermaphrodites. A lesser known fact is that beadlet anemones are viviparous, they give birth to live young. Their embryos develop inside their bodies until they are ready to be released into the water column. This gives the tiny embryos a head-start as they grow within the protection of their parent. Once ready to be released, the young are ejected from the mouth into the water column. The young will settle close to their parent creating a familial territory although they do not form colonies.

The opening and closing of the anemone is highly dominated by tidal cycles. When beadlets are caught from the wild and brought into aquarium environments, they continue to display synchronicity with the tidal area they were originally caught in, for a few days after. This opening and closing is used to prevent the animal from desiccation when exposed by the falling of the tide. In fact, they can survive out of the water in this state for many hours even if exposed to direct sunlight for much of it.

Typically, the closed state of the anemone looks like a blob of red stuck to the rock. However, they can be green, brown and yellow too. Conventional wisdom has always suggested that the various colour morphs form part of the same species, Actinia equina. However, the latest genetic work now implies that these colour morphs might actually be subspecies or even different species altogether!

So, what important ecological role do these animals play? Beadlets occupy an important niche in the ecosystem making them vital for conservational efforts in general. As predators they exert top-down control on the populations of crabs, shrimps and mussels that habituate the rocky shoreline. This makes them a key player in maintaining ecosystem balance with respect to the stated species.

They also produce an antibacterial substance which is different to lysozyme present in most other animals. Lysozyme is an antibacterial agent found in humans in our tear drops, saliva, human milk and mucus. This means they have a strong research possibility towards developing new antibacterial formulas which could help us fight all sorts of infections. So, who might be the heroes now?

So next time you are walking along the beach and you see children attacking a chupa sangre it might be worth mentioning that they are not blood suckers but a species important to the health of the ecology of the Gibraltar coastline. Together, conservationally speaking, we can provide a winning sting!