Cuttlefish are not fish! They are molluscs (Phylum Mollusca) like snails, slugs and clams; and cephalopods (Class Cephalopoda) which include squids and octopuses.
This small stout cuttlefish edged with iridescent glittering spots around its fins is commonly seen on among seagrasses at Changi. Thanks to Ywee Chieh, I learn that it is Sepiella inermis, which I shall call the Glittering cuttlefish. Elsewhere, it is called the Spineless cuttlefish because its cuttlebone lacks a spine at the tip that many other cuttlefishes have.
This plump cuttlefish is sometimes seen near reefy areas, hovering slowly close to the ground. It is apparently a juvenile that mimics mangrove leaves in colour (brown or yellow) and pattern (complete with stem, ribs and scattered spots) as well as floating movement in the water!
Broadclub cuttlefish. It is considered among the most common cuttlefishes in reefs to 30m deep, and also among the largest of cuttlefishes, growing up to 50cm long and weighing up to 10kgs. Ywee Chieh says the humungous cuttlefish found during the recent Mega Marine Survey's Southern Expedition is the Broadclub cuttlefish!
|Photo by Jiaxin.|
I read that it has an intriguing way of catching prey! Apparently, it mesmerises or distracts fishes and crustaceans by producing a rapid rhythmic pulsation of dark bands along the body and arms. Here's another clip from the Hantu Blog with cuttlefishes talking!
This cuttlefish lays its egg capsules deep inside branching corals such as Pore hard corals (Porites sp.). A male cuttlefish establishes a territory over coral colonies suitable for egg laying. The female approaches the male, mates with him, then lays the eggs deep among the coral branches where they harden and are hard to remove. The eggs hatch in 4-6 weeks. Perhaps these white egg masses that I saw tucked among hard coral were laid by such a cuttlefish?
We often see these squids on the intertidal near reefs. Thanks to Ywee Chieh, I learn that it is Sepioteuthis lessoniana or the Bigfin reef squid. It has indeed wide fins that extend along the entire body length, and is thus sometimes mistaken for a cuttlefish. The fins oval or somewhat pear-shaped with the widest part near the rear end of the body.
This more streamlined squid with a triangular tail is not often seen on the intertidal. Thanks to Ywee Chieh, I learn that it is Uroteuthis duvaucelii or the Indian squid.
Like other cephalopods, cuttlefishes and squids can rapidly change their body colour, and some also their body texture! This chubby little cuttlefish can change colours and patterns rapidly, and turn from smooth to bumpy! It is sometimes seen on Changi beach among seagrasses.
Curvespine cuttlefish. 'Recurvirostra' means 'curved spine' referring the shape of the spine on its cuttlebone, not visible in a living animal. Relying on speed, cuttlefishes do not have a thick, heavy outer shell. Their shells are reduced to lightweight internal bones. In cuttlefishes, these are flat surfboards riddled with tiny gas-filled chambers. By controlling the amount of gas in the cuttlebone, the cuttlefish can control its bouyancy. The features of the cuttlebone are often vital in identifying the cuttlefish.