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Ram's Horn Squid
Spirula Spirula
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Spirulida
Family: Spirulidae
Genus: Spirula
Species: S. spirula
Description:
S. spirula is a species of deep-water squid-like cephalopod mollusk. It is the only extant member of the order. It is between 35-45mm longs with eight arms and two longer tentacles, all of which have suckers. It is called the ram’s horn squid because it has an internal shell. Live specimens are rare to be seen but the shells of S. spirula are very common. The shells are very light weight, very buoyant, and shockingly durable.
Habitats/Range:
During the day S. spirula lives in the deep ocean at depths of about 1,000m. By night it rises to the 100-300m. It prefers temperatures around 10C (Price). Tends to live in the tropics and there have been many observed in the seas near the Canary Islands. Many of the shells have been found along the west coast of South Africa and New Zealand.
Adaptions:
As mentioned above the S. spirula’s shell is a great adaptation for deep sea living. The shell is shaped in a flat spiral where none of the spirals touch each other. The shell functions to osmotically control the buoyancy of S. spirula, and keep it in a vertical attitude (Denton). Due to the shape of the shell it allows the squid to pull up inside the mantle when threatened. One of the most interesting adaptations S. spirula has is the ability to emit a green light from an organ called photophore, at the tip of its mantle (Herring).
Feeding:
Hunts for food during the night. Mostly surviving on small fish and crustaceans.The feeding apparatus is like a normal squid, containing a beaked mouth and a radula. Thought to consume up to 20-40% of their body weight per day (Fletcher).
Development/Reproduction:
Not much is know about S. spirula development or reproduction. They are thought to spawn in winter in deep water, however no spawnlings have been seen directly. There are separate sexes but the sex determination process has yet to be determined. They have internal fertilization and after hatching there is no parental involvement. Sexual maturation is reached around the 12-15 month mark when they are roughly 30mm in size. The average life span is 1.5-2 years (Clarke).
Work Cited:
Clarke, M. R. “Growth and Development of Spirula Spirula | Journal of the Marine Biological Association of the United Kingdom.” Cambridge Core, Cambridge University Press, 1 May 2009, www.cambridge.org/core/journals/journal-of-the-marine-biological-association-of-the-united- kingdom/article/growth-and-development-of-spirula-spirula/FF9145093CC733FACA8CFC7930C595D3.
Denton, E. J., et al. “On the Buoyancy of Spirula Spirula | Journal of the Marine Biological Association of the United Kingdom.” Cambridge Core, Cambridge University Press, 1 May 2009, www.cambridge.org/core/journals/journal-of-the-marine-biological-association-of-the-united- kingdom/article/on-the-buoyancy-of-spirula-spirula/33B5D6470FA4EEE0481DE80007015B4E.
Fletcher, James F. “Page: Tree of Life Spirulidae Owen, 1836. Spirula Spirula Linnaeus, 1758. Ram's-Horn Squid.” Spirula Spirula, 15 June 2016, tolweb.org/Spirula_spirula/148171.
Herring, Peter J., et al. “The Light Organs of Sepiola Atlantica and Spirula Spirula (Mollusca: Cephalopoda): Bacterial and Intrinsic Systems in The Order Sepioidea | Journal of the Marine Biological Association of the United Kingdom.” Cambridge Core, Cambridge University Press, 1 May 2009, www.cambridge.org/core/journals/journal-of-the-marine-biological-association-of-the-united-kingdom/article/the-light-organs-of-sepiola-atlantica- and-spirula-spirula-mollusca-cephalopoda-bacterial-and-intrinsic-systems-in-the-order-sepioidea/8DCD2FF1330796DEAD5D290A088EC840.
Price, Dean G. “Ram's Horn Squid - Spirula Spirula - Details.” Encyclopedia of Life, 6 Sept. 2015, eol.org/pages/450457/details.
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