24 October 2013

Getting to know our Singapore sotong

Thanks to Tay Ywee Chieh, I've learnt more about some of the cuttlefishes and squids (locally called 'sotong') commonly seen on our shores!
Knowing their identities has helped me learn more about the fascinating behaviour of these cephalopods!

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.
Glittering cuttlefish (Sepiella inermis)
Females, which are usually bigger than males, lay a single black globular egg capsule, attaching it to a hard surface. Hmm... I must look out for this kind of egg capsule.

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 (Sepia latimanus)
Thanks to Ywee Chieh, I learn that it is Sepia latimanus or the 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.
It is distinguished by a yellow ring around lower edge of the eye. The volunteer divers with the Hantu Blog often encounter humungous cuttlefishes like this one the size of a football. Perhaps those are the adults?

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?
Cephalopod egg capsules in Montipora coral (Montipora sp.)

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.
Oil-slicked Tanah Merah: Bigfin reef squid (Sepioteuthis lessoniana)
Bigfin reef squids of similar size often school together, apparently for safety from larger Bigfin reef squids which might eat them!
Bigfin reef squids (Sepioteuthis lessoniana)
Adults may grow to 40cm and weigh 2kgs! Indeed, at Tanah Merah I have seen some up to 30cm long! These squids eat mainly prawns and fishes, occasionally mantis shrimps and crabs.
Bigfin reef squid (Sepioteuthis lessoniana)
During breeding, males and females perform elaborate courtship displays. Females lay lumpy sausage-like egg capsules in clusters attached to hard surfaces. Each sausage contains about 13 eggs in a row. Perhaps these egg capsules that I've seen attached to sponges, seaweeds and other hard surfaces were laid by these squids?
Cephalopod egg capsules on Sargassum sp.

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.
Indian squid (Uroteuthis duvaucelii)
It too can grow to 30cm long and weigh 1.5kg.  It feeds on fishes, crustaceans and other squids, even other Indian squids. Eggs are laid in masses called egg mops, made up of many capsules, each capsule containing many eggs (100-300 eggs).

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 (Sepia recurvirostra)
Thanks to Ywee Chieh, I learn that it is Sepia recurvirostra or the 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.
Cuttlebone - internal skeleton of a cuttlefish
Squid and cuttlefishes also squirt ink, that often resembles the squirter in shape and size which distracts the predator while the cuttlefish or squid zooms away.
Bigfin reef squid (Sepioteuthis lessoniana)
Like many other marine creatures, humans love to eat 'sotong' too. Indeed, all these species are harvested both by coastal dwellers for subsistence as well as commercially by trawling and nets. In some areas, they are sadly overfished. So make sure you don't waste the lives that are on your plate. Take only what you need, and eat up all that you take.
Our favourite sea creatures: Baby squid
Grateful thanks to Ywee Chieh who spent time painstakingly identifying my sotong photos on flickr one by one, many months ago. I'm sorry it took so long for me to consolidate her IDs.

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