Goose Barnacles on Rhossili Beach

There was a lot of excitement this summer (2009) when a pole covered with Goose or Stalked Barnacles (Lepas anatifera Linnaeus) was washed up at Oxwich Bay, in Gower, South Wales. It particularly captured the imaginations of the holiday-makers because the animals were still alive and active – resembling so many tiny alien creatures or monsters.

Although this event was considered to be very rare, it is not really that uncommon an occurrence here or on the south coast of England. In August last year (2008) I spotted a blue fishing crate washed up high on the sandy beach at Rhossili. It too was covered with thousands of living Goose Barnacles and was totally fascinating to watch.

These marine animals are Crustaceans belonging to the Cirripedia or barnacle group. Unlike the barnacles that we normally find securely attached to rocks and other hard objects on the seashore, this species only lives attached to free-floating objects that drift around our oceans and prefers warmer waters.

Goose barnacles are not fixed directly to the substrate by their many plated calcareous shell – as with the acorn barnacles. They have two main parts: the long stalk or peduncle and the body part called the capitulum at the end of the stalk.

The peduncle is soft, solid, and flexible. It contains two organs – the cement gland by the secretions of which it sticks itself to hard objects; and the ovary. At the fixed (proximal) end, the stalk is smoother, glossier, translucent and orange in colour. At the end nearest the capitulum (distal end) the stalk is more wrinkled and leathery-looking with a darker, purple- black colour. The stalk has the ability to contract. Muscles at the point where the stalk  joins the body allow it limited rotation.

The capitulum contains the body or prosoma of the Goose Barnacle. On the outside there are five calcareous plates: a pair of tergae, a pair of scutae and the carina. These plates are translucent white, and generally smooth but showing fine concentric growth lines where they add on more shell around all their borders. The plates are joined to each other by flexible sutures and are attached to the integument which wraps around the body. The integument is brown-black with yellow thickened edges like lips at the  opening through which the animal extends its appendages. 

The shelled integument covers the body of the Goose Barnacle. The body comprises the breathing and feeding apparatus, the gut, and the male organs. Goose Barnacles are hermaphrodite and have both male and female reproductive organs. However, the most obvious features, that intrigued all the beachcombers at Oxwich this year, are the six pairs of forked (biramous)articulated appendages – the cirripedes or thoracic legs.

The cirripedes are setose or fringed with pink hairs. In the past, people thought these appendages looked like feathers. The story was told that geese grew from these feathery marine creatures – giving rise to their naming as Goose Barnacles, and to the naming of Barnacle Geese that were suppose to develop from them. This was a useful myth in the religious medieval days when it was forbidden to eat meat on Fridays or Holy Days. It meant that geese, originating as marine creatures, could be classified as fish and eaten on these special days.

Within the body of the Goose Barnacle, pulsation of the thorax pushes the cirripedes in and out of the integument in a rhythmic fashion. This looks like a fishing net being cast into the sea – and that is exactly what it is. The hairs on the legs trap minute planktonic organisms and debris from the sea water. These particles are scraped from the hairs by jointed mouth-parts when the cirripedes are retracted into the integument, and then passed into the gut . 

The freshly-beached Goose Barnacles in these photographs, and at Oxwich Bay this summer, were still automatically going through the motions of feeding by periodically thrusting out their hairy legs into the air, extending and contracting their stalks, and moving their bodies to and fro.

It is sad to see these creatures cast up on the strandline but it has allowed many people to catch a glimpse of something very special and to imagine the spectacular sight of a colony of these Goose Barnacles floating through the surface waters of warm seas, writhing like snakes on a Medusa’s head  as the bodies trail on long stalks while feeding.

COPYRIGHT JESSICA WINDER 2011

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