Cuttlebone – provides lift for the Cuttlefish, allowing it to hover in the water without expending energy swimming.
A few interesting natural history finds amidst the litter on the the July Beach Clean at Half Moon Bay, Heysham. These included a dead porpoise, two adult cuttlebones and some wireweed (Sargassum muticum).
Cuttlebones are the internalised shells of cuttlefish, formed of delicate lemellae and filled with gas, the organ holds the live cuttlefish at a fixed height in the water column, without them having to expend energy swimming. They also limit the maximum depth this animal can attain, as below 50m or so the cuttlebone would implode. A mating pair of cuttlefish were seen by group members at Roa Island some years ago.
The porpoise was a rather sad sight, there are not many reports of these animals in Morecambe Bay, with its shallow waters and treacherous tides. The state of decomposition suggested that the corpse may have drifted in from elsewhere…
Wireweed is not native to British waters, having been introduced accidentally with Pacific Oysters, which are bred around the coastline.