Friday, October 8, 2010

Cephalopods of South Georgia. 2010

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The Cephalopods have many species, around 650 species. The waters of South Georgia are home to 13 species of squid and 6 species of octopus. Cephalopods are most intelligent of the invertebrates, having well-developed senses and large brains. Most cephalopods have three ways to protect against the predator, the first way is to change colour for camouflage since they possess chromatophores, the second way is expel a cloud dark ink through the funnel in the water so make confuse predators, and the last action is move by jet propulsion for escaping possible predators. Squid and cirrate octopods use their tail fins for more routine swimming. Cephalopods usually eat small fish and crustaceans. Most cephalopods have short lives, growing rapidly, reproducing once and then dying.

South Georgia Post has issued the stamp series depicted Cephalopods on April 2010. The stamp series comprised of one set stamp of 4 pieces stamps, one souvenir sheet and 2 pieces of First day Cover.The Cephalopods species which depicted are Galiteuthis glacialis, Psychroteuthis glacialis, Thaumeledone gunteri and Stauroteuthis gilchristi.

Galiteuthis glacialis (27p value) is one of the most abundant and widely distributed of the Antarctic squids. It is a delicate mid-water (pelagic) species that lives from the surface down to around 1 km deep. The stamp depicts a juvenile squid (around 5 cm). Galiteuthis glacialis is eaten by many predators including light mantled sooty albatross, grey-headed albatross and white-chinned petrels.

Psychroteuthis glacialis (65p value)is an active glacial squid, muscular species, which reaches a moderate size of 40 cm body length. The glacial squid is abundant throughout Antarctic waters and South Georgia is at the northern end of its range. Psychroteuthis glacialis is an important prey for many predators including elephant and Weddell seals, wandering and grey-headed albatross and emperor penguins.

Thaumeledone gunteri (90p value) is a small species (less than 10 cm) as one of the incirrate octopods which living between 400 and 700 m all around South Georgia.

Stauroteuthis gilchristi (£1.10p value) is a mid-water species, living at depths of 700-1000 m around South Georgia. The arms of Stauroteuthis gilchristi are connected by thin membranous tissue to form a web and the stamp depicts the octopus expanding the arms and web. This maybe a defensive posture, which makes the octopus appear bigger to possible predators.

Cephalopods ss

The souvenir sheet depicted one stamp of £ 2.0 value depicted the Sperm whale is catching the Colossal squid.

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