Ocean Giants: Giant Squid

Last week we talked about the Kraken, that it's a squid-like sea monster and that its identity can be either of the two known largest extant squids. First was the heaviest, the colossal squid Mesonychoteuthis hamiltoni (read article here). The second is the longest, the giant squid Architeuthis dux with a cosmopolitan distribution.

Photo taken by Tsunemi Kubodera from Ogasawara Islands, off Tokyo on December 4, 2006 [1].

There are many different species listed under the genus Architeuthis, 21 nominal species in total. But based on a genetic study conducted by Guerra et al (2013), all species are synonyms of A. dux; thus, there is only one giant squid. Furthermore, like the majority of deep sea species, little is known of its biology. Obviously it's a predator; it feeds on fishes and other cephalopods. It has a short life cycle; spawning occurs only once and the females die after bearing their eggs. The largest recorded species measured 12 m in length, unfortunately there was no record of its weight. Studies on its growth and mortality were very limited since getting a sample population from the ocean was tough. Thus, if you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

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[1] Accessed from http://animals.nationalgeographic.com/animals/invertebrates/giant-squid/
[2] McClain CR et al (2015) Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[3] Guerra A et al (2013) Architeuthis dux: única especie de calamar gigante en el mundo. MOL. Revista de la Sociedad de Ciencias de Galicia 53:46-53.
[4] Bolstad KS et al (2004) Gut contents of a giant squid Architeuthis dux (Cephalopoda: Oegopsida) from New Zealand waters. New Zealand Journal of Zoology 31(1):15-21.


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Ocean Giants: Colossal Squid

Who here have watched the movie "Clash of the Titans"? Remember the scene when Zeus shouted "Release the Kraken!" to his men? Kraken actually refers to a squid-like sea monster and among the family of squids, there are two known largest species. First is the heaviest - the colossal squid Mesonychoteuthis hamiltoni commonly found in the Antartic.

The short clip above presents the largest specimen ever caught, it weighed 495 kg and measured 4.2 m in length [1]; but the measurements stated are underrated. Experiments conducted by the Te Papa staff from the Museum of New Zealand showed that fresh specimens can shrink up to 22% when preserved and the specimen above was believed to have shrunk by 14%. Unfortunately, only 9 adult specimens have been recorded and were not enough to fully study their biology [2]. Thus, if you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

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[1] McClain CR et al (2015) Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[2] The Museum of New Zealand Te Papa Tongarewa. The Squid Files. Accessed from http://squid.tepapa.govt.nz/the-squid-files


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Ocean Giants: Australian Trumpet

If the largest bivalve is the giant clam Tridacna gigas (read article here), the largest gastropod on the other hand is the Australian trumpet Syrinx aruanus.

Photo from the Queensland Museum.

It is found from northern Australia and extends through the Indonesian Papua New Guinea. The largest recorded size measured 72.2 cm in shell length [1]. Based on its size, it can be deduced that this species is a predator. It hunts and feeds on polychaete worms, such as Polyodontes australiensis, Loimia ochracea, L. ingens and Diopatra sp. [2]. Apparently, this species is popularly used as an ornament and the demand for its shell increased over the past decades. Thus, the Australian government limited the amount of its catch for both commercial and recreational fishers [3]. Knowledge on its biology would be a help develop a way to prevent the decline of wild stocks. Unfortunately, little is known on the biology of  the Australian trumpet (to view the information we have, you may visit SeaLifeBase). Thus, if you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

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[1] McClain CR et al (2015) Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[2] Taylor JD and Glover EA (20030 Food of giants - field observations on the diet of Syrinx aruanus (Linnaeus, 1758) (Turbinellidae) the largest living gastropod. pp. 217-224. In Wells FE, Walker DI, and Jones DS (eds) The Marine Flora and Fauna of Dampier, Western Australia. Western Australian Museum, Perth.
[3] Weis A et al (2004) Ecological assessment of Queensland's marine specimen shell collection fishery. Report to the Australian Government Department of the Environment and Heritage on the ecologically sustainable development management of a small scale, highly selective hand and shell dredge collection fishery. Accessed from http://155.187.2.69/coasts/fisheries/qld/marine-specimen-shell/pubs/marine-specimen-shell-submission.pdf


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Ocean Giants: Giant Clam

You don't have to look too deep in the ocean for exotic beauty because the vast coral reefs already offer some of the most spectacular underwater sights. Coral reefs, the marine counterpart of rainforests, serve as habitat to various species ranging from invertebrates such as mollusks to mammals such as sea turtles. And among the species of mollusks is the largest known bivalve, the giant clam Tridacna gigas. It is found in the Indo-West Pacific, from the intertidal zone to depths of 35 m (Bernard et al 1993) [1]. The largest known individual measured 137 cm in length and weighed 250 kg [2]. 

Giant clam on reef, photo from www.arkive.org

Giant clams are known for their unique ability to ‘self-feed’. How do they do it? During an early stage in their life cycle, they ingest dinoflagellate algae. The algae are not digested but rather propagate in the gut. Basically, the clam is dependent on this algae and filters sea water for it to grow at such length. Giant clam meat, i.e., from its adductor muscle, is in high demand. Unregulated harvesting of wild stocks posed and continues to threaten native populations throughout the Indo-Pacific. This led to attempts to develop harvestable cultured populations [3]. Because of this, information on the biology and ecology of giant clams were rendered available in the scientific literature. You may visit SeaLifeBase to view this information.

Giant clams in spawning tank in mariculture plant, photo from www.arkive.org

If you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

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[1] Bernard FR et al (1993) Catalogue of the Living Marine Bivalve Molluscs in China. Hong Kong University Press, 121 p.
[2] McClain, C.R., et al. 2015. Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[3] Munro JL (1993) Chapter 13: Giant clams. FFA Report 92/75.


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Ocean Giants: Giant Isopod

The deep sea is full of wonders, and many creatures are waiting to be discovered. Technology makes it possible for scientists to go down the depths of our seas to study and identify these creatures. For example, the photo below was posted by a deep-sea technician in 2010 in the social site Reddit where he wrote, "I work for a Sub-sea Survey Company, recently this beast came up attached to one of our ROVs. It measures a wee bit over 2.5 feet head to tail, and we expect it latched onto the ROV at roughly 8,500 m depth. Unfortunately, the e-mail that these pictures were attached to came from a contractor, and the ship he was operating from is unknown, so I can't tell you what part of the earth this beast was living." Readers' responses ranged from curios to horrified [1]. 

Photo from NOAA/OER.

Later on, it was identified as Bathynomus giganteus, the giant isopod. Isopods are crustaceans (not bugs, even if they look like roaches). They dwell in the deep floors of the Atlantic and Pacific Oceans, and can grow up to 50 cm in length. They often figure as bycatch in trawl fisheries [2]. Not only are they the largest isopod, they also have the largest egg (~10 mm) among pericaridans. Egg brooding is trait of the giant isopod, which may take several months, and at which time, females stop to feed. Instead, they burrow in the sediments and remain quiescent throughout the brooding period [3].

To know more about the giant isopod, visit SeaLifeBase.

If you have other information on them, which you wish to include in our information system, please e-mail us at sealifebase@fin.ph or join us as a collaborator.

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[1] Braun, D. 2010. Bathynomus giganteus: terrifying sea beast hauled up. Accessed on 13/02/2015 from http://voices.nationalgeographic.com/2010/03/31/bathynomus_giganteus_terrifying_sea_beast/
[2] McClain, C.R., et al. 2015. Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. PeerJ 2:e715. Accessed from https://peerj.com/articles/715/
[3] Barradas-Ortiz, C., et al. 2003. Seasonal reproduction and feeding ecology of giant isopods Bathynomus giganteus from the continental slope of the Yucatán Peninsula. Deep-Sea Research I 50(4):495-513. Accessed from http://www.sciencedirect.com/science/article/pii/S0967063703000360


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The red rainbow of the deep sea

The most amazing sea creatures can be found in the deep sea. One such species whose name can be a tongue twister is the bloodybelly comb jelly, Lampocteis cruentiventer. 

Photo by Kevin Raskoff/MBARI (c) 1999.

It is the only known species under the genus Lampocteis, first described and identified in 2001 by Harbison, Matusmoto and Robison. It was named as such because of its blood-red stomach. Light is diffracted from its ciliated comb rows that beat continuously to propel it through the water column. This contributes to the sparkling display of colors along its comb rows.

 

In the deep sea, shiny objects can be perceived as prey. However, despite its radiant color, this species is invisible to its predators. And, it also masks the bioluminescent prey it swallows from other potential predators. Taking advantage of the conditions of its environment, it has developed stealth to shield itself from prying predators. Not bad, aye?

If you want to share what you know about this species (e.g. morphology, distribution, life history, etc.) you can help us by becoming a collaborator, just e-mail us at sealifebase@fin.ph.

Visit SeaLifeBase to know more about comb jellies.

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Source: Monterey Bay Aquarium (MBARI). See page link here.


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A squid's human-like pregnancy

Gonatus onyx, commonly known as the black-eyed or clawed armhook squid, is abundantly found in the Atlantic and Pacific oceans. Little has been known about its life history because they spawn at great depths, making it difficult for researchers to study them. But with the recent developments in technology and fishery, Seibel and his colleagues (2005) were able to observe its brooding behavior - a very important insight on the reproduction of this species.

Squids are believed to be non-guarders, that is, they deposit their eggs on the sea floor and let them develop on their own. This species, though, begs to differ. It uses its hooks to hold the egg mass (2,000-3,000 eggs), extending from the mouth to well beyond its arms. Because of low temperatures (this happens at X,XXX m depths) and the relatively large size of their eggs, egg development is prolonged. The female squid can, therefore, carry this egg mass for a maximum of 9 months, much like women of our species. And despite of muscle degeneration at sexual maturation, female squids are able to protect their eggs from the inevitable threat imposed by the deep sea. All mothers have this intuition, regardless of what species they are. As Barbara Kingsolver once said, "Sometimes the strength of motherhood is greater than natural laws."

To know more about the black-eyed squid, visit SeaLifeBase.

If you have other information on them, you can e-mail us at sealifebase@fin.ph or come be a collaborator.

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Seibel, B.A., B.H. Robison, and S.H.D. Haddock. 2005. Post-spawning egg care by a squid. Nature (Brief Communications) vol. 438, 15 December 2005 issue, p.929. See article here.


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