Top ten facts you probably didn’t know about barnacles.
Blistering Barnacles! The bane of many a seafarer, the humble barnacle is responsible for a multi-billion dollar biofoul industry. Here are some unusual facts about this tenacious crustacean.
- There are over 1400 species of barnacle around the world. Classed as a crustacean they are related to crabs and lobsters. The barnacle that commonly inhabits the bottom of yachts is the acorn barnacle.
- Acorn barnacles attach themselves to rock, sealife and boats by secreting a quick-setting cement. This cement is one of the strongest natural glues science has yet discovered. It has a tensile strength of 5,000 pounds per square inch and adhesive strength of 22-60 pounds per square inch.
- Barnacles have a life expectancy of between 8 and 20 years. Their main predators are the whelk and of course the pressure washer!
- Barnacles do grow the more they eat. It is not known how they enlarge their shell. Most probably they use a chemical to dissolve the inner layers whilst new layers are added to the outer shell.
- In Spain and Portugal, the Goose barnacle is considered a great delicacy. Prices can reach up to 200 Euros per kilo for this Galician crustacean. Apparently they taste better than they look!
- Barnacles are hermaphrodites having both male and female reproductive organs. However, they must cross-fertilize in order to produce offspring. They have a long, retractable tube which can reach eight times their body length. This is the longest reproductive organ length relative to body size in the animal kingdom. At the end of a mating season, this organ dissolves and a new one is grown for the next season.
- The acorn barnacle’s shell is made up of six calcium plates surrounding the barnacle in a circle. Then there are four plates that act as doors and slide across the top of the barnacle to protect the barnacle from moisture loss and predators.
- Barnacles have no heart. They do, however, have a sinus which performs a similar function with muscles pushing blood through.
- Barnacles have no gills. Instead, they absorb oxygen through their legs or cirri which wave around in the water.
- American poet A E Stallings wrote a poem about a barnacle:
The barnacle is rather odd —
It’s not related to the clam
Or limpet. It’s an arthropod,
Though one that doesn’t give a damn.
Cousin to the crab and shrimp,
When larval, it can twitch and swim,
And make decisions — tiny imp
That flits according to its whim.
Once grown, with nothing more to prove
It hunkers down, and will remain
Stuck fast. And once it does not move,
Has no more purpose for a brain.
Its one boast is, it will not budge,
Cemented where it chanced to sink,
Sclerotic, stubborn as a grudge.
Settled, it does not need to think.
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