No bones about it

August 14th 2018

You have possibly heard about cuttlefish and their bones. If you’ve ever had a pet caged bird for example you are very likely to have given it a calcium-rich dietary supplement in the form of a piece of cuttlebone.

The cuttlebone is a chambered, gas-filled internal ‘shell’ which cuttlefish use for buoyancy control.

Cuttlefish, being marine molluscs, are related to snails, etc. and form part of a group known as cephalopods, which means ‘head foot’. All the species in the group have tentacles attached to their head! The largest species of cuttlefish in british waters is the Common Cuttlefish, Sepia officinalis which can grow to a length of about 45cm. The largest species worldwide is the Australian Giant Cuttlefish, Sepia apama and it can exceed one metre in length.

On 24thJuly 2018 Avril and I accompanied about 18 other folk on the Highlife Highland Ranger’s Rock-pooling day at Clashnessie. It’s always a great day out, not sure if the kids or adults have most fun!

I decided to have a go at ‘push-netting’ to see what I could come up with. This involved pushing a small net, mounted on a wooden frame, through the sandy bottom of the shallow sea water. The first push drew a blank, the second push however delivered the ‘catch’ of the day, and a first for everyone there, – a Common Bobtail Cuttlefish, Sepietta oweniana.

After some reading up we found out that although these small animals are closely related to true cuttlefish they in fact have no cuttlebone! This one was an adult and measured c45mm in length, excluding the tentacles.

There are very few records of adults of this species around the coast of Assynt and this one was clearly not happy at being caught. Shortly after we placed it in a plastic tray it produced two clouds of ink, this is a defence mechanism. This ink was, at one time, used by artists and writers, hence the colour sepia. Sepia is reddish-brown and gets it’s name from the rich brown pigment derived from the ink sac of cuttlefish, Sepia spp.

Not that our specimen was simply ‘sepia’ it did give the distinct impression at one point of trying to change its colour to match the small amount of sand in the corner of the tray.

David Haines

Report a Sighting

Recent Sightings

Kittiwake

c100 adult and 1st-winter birds feeding off Clachtoll (DAH) (24/09)

Tufted Duck

two male birds on Loch Drumbeg (DAH) (22/09)

Merlin

single bird near Stoer Village Hall (DAH) (21/09)

UPDATE on colour-ringed Oystercatcher

we have heard back from the Icelandic Wader Group regarding the colour-ringed Oystercatcher spotted at Bay of Culkein on Tuesday. It was ringed, as an adult, near its nest while it was territory-guarding on 19th May this year; the location was Eskifjorour which is on the east coast of Iceland. We will post a short article on the Field Club's website in the next few days regarding other sightings of colour-ringed birds recorded in Assynt (DAH) (20/09)

Pink-footed Goose

c225, in four skeins, heading east over Culkein Drumbeg (DAH). Oh boy, it's autumn! (20/09)

Wigeon

single male in eclipse plumage Loch Inver (DAH) (20/09)

Manx Shearwater

young bird rescued from a garden at Inchnadamph (Chris Rix/Andy Summers). The bird, which was well off-course, was successfully released at Stoer the next day. (18/09)

Oystercatcher

four birds resting on rocks Bay of Culkein (DAH). One of these birds, an adult, had a combination of coloured rings on its legs. The details have been submitted to the appropriate ringing scheme, which appears to be the International Wader Study Group, and we will report back once we hear from them. (18/09)

Map