Cool critter of the month: Pelagic Gooseneck Barnacles

Phylum: Arthropoda Family: Lepadidae

Where do they live?

These guys can be found on pretty much in any ocean in the world.  As long as there is something solid (a substrate) they can attach themselves to, these guys are happy.  Which is a good thing because (as the name suggests) these guys are pelagic – living in the water column so being fussy would not be a very good move.  They have been found living on piles and piers along coastlines, but in the ocean anything will do – the hull of a boat (much to seafarers’ dismay), a buoy, some driftwood, and (as you can just make out in my photo below) the sole of a shoe.  There has even been a report of these guys attaching themselves to turtles.

Why are they awesome?

Don’t let looks fool you.  These critter may look a little dull but like all life on this planet they are amazing.  Here’s a few examples of why the pelagic gooseneck barnacle is one awesome critter

What have they got to do with geese?

To understand this, we need to go back in time to around the 13th century and look at another species - Branta leucopsis - the barnacle goose.  These geese are a migratory species, many of them wintering across the UK, and breeding up in the Arctic.  Now back in the 13th century, the guys in the UK didn’t know about this migratory behaviour so where they came from was a mystery…until someone spotted a resemblance between the barnacles and the head of the geese.  And so the story was born.  The barnacles were given their scientific name - meaning bearer of ducklings.  It was said that the barnacles came from wood and then turned into the geese.  If your curious about the apparent resemblance check out this photo on the Arkive website.

My what a long… stalky thing you have!

You can probably tell from the photo below that these guys aren’t exactly huge.  Their shell (called the capitulum) is made up of plates, and averages a total of 4 – 5 cm in length when fully grown.  But that long black stalky looking thing (called the peduncle)…well that can get up to a whopping 85 cm long.  These peduncles are strong and flexible.  Once the barnacle attached itself to a substrate it stays there, only dislodged by some tremendous force.  It sticks there by using a ‘cement’ – a substance that is generated in a cement secreting gland located in the peduncle.  The substance travels from the gland to the foot via some canals, and hardens on contact with a substrate.

Getting down to business: How do the mate?

These critters are hermaphrodites – possessing both male and female organs.  When it comes to mating, these barnacles don’t hang around.  Within 2 weeks of settling they are sexually mature, and considered fully grown within 6 weeks.  As far as we can tell, they won’t self- fertilize, but are quite happy to play with their neighbours…. a lot.  This gregarious species does have some boundaries to when they spread their love – temperature.  If it’s too hot (ideally not above 25 Celsius but no higher than 30 Celsius) or too cold (ideally not below 19 Celsius but certainly no lower than 15 Celsius) then they just aren’t interested.  This has to with their sexual organs.  The ovaries apparently ‘disappear’ below 15 Celsius and above 25 Celsius.  The penis has an even narrower temperature range, becoming inactive below 19 Celsius and above 25 Celsius.  Like many marine species, their offspring is a type of zooplankton, drifting on currents until they are large enough and fortunate enough to find a substrate to attach themselves to.

Image: My own photo (taken with an old phone camera).  We found these little guys whilst doing a beach clean.  It seems that one man’s litter is another species handy substrate.