Welcome!

So, you've found my blog. Congrats! And...I'm thinking you like squid.
I'm right, aren't I?
Crazy, eh? I know, I'm a little psychic. Don't worry, I get it all the time.

Anyway, you're interested in squid and I won't delay any longer. Welcome to my blog about my favourite animal taxon, Octopoteuthidae. I hope that after you've poked around for a bit you'll have a better understanding of this amazing family, and of squid in general.

To start with I thought I'd just give you an idea as to where in the 'tree of life' you can find these guys. They're animals, clearly - and molluscs as well (most people know that, but it is still counterintuitive when you compare them to other mollucs: slugs, clams, chitons, etc.).
Squid are a major group in the Cephalopoda, the 'head-foot'-ed in Greek. Then we get into some abstract groupings, and emerge at the Decapodiformes. These are all the 10 armed cephalopods (deca = 10) two of which have been modified into tentacles. These include the squid, cuttlefish, sepiolids, Spirula, and their relatives. This group is to the exclusion of 8 armed cephalopods, the Octopodiformes, which are the octopus and Vampyroteuthis infernalis. Order Teuthida are the squid - pretty straightforward. Oegopsids are squids without a cornea covering the eye. They are a major group of cephalopods, dominating pelagic and open ocean environments.

And finally, here we are, we have arrived at the Octopoteuthidae. Please keep all arms, legs, and tentacles inside the cart until the ride has come to a complete stop. Actually, the ride has just begun...

Adult Taningia danae attacking
a baited line at 200 m depth
(Kubodera et al., 2007).

Morphology

Octopoteuthids are generally large squid with a conical mantle up to 170 cm in length. Bordering the mantle are two very large rhomboidal fins. These are the main source of propulsion for octopoteuthid squid; they relying less heavily on jet propulsion than other taxa.

Octopoeuthis deletron and Taningia danae (Tolweb.org).

At the center of the arm crown are two large chitinous beaks that are used to chew up food. These are indigestible, and the recovery of them from predator stomachs has become a very important source of distribution data for the family.

Series of lower Octopoteuthis spp. beaks (Jesse Kelly).

Arms are what really characterize the family. Some important features include:

• Only 8 arms, no tentacles in adults. Young have two tentacles but they're lost with growth.
• Two rows of hooks on all arms pointing down-arm towards mouth.
• Photophores borne on armtips. Believed to occur in species-specific patterns. Important in species identification.
• Fragile arm tips, often breaking off before examination. Believed to be defensive mechanism: following severance tips twist violently and flash brightly to distract predator. Makes species identifications difficult.

Hooks of O. deletron and a young T. danae in an aquarium (Tolweb.org).

Photophores are also borne on the ventral surface of the mantle and on the visceral mass. Ventral photophore numbers and positions are also used in species identifications.

Tolweb.org

An incredible advancement on the armtip photophores is found in Taningia danae. Borne at the tips of arm pair II are the largest photophores known in the animal kingdom! Equipped with an eye-lid mechanism, T. danae can control the length of flashes simply by opening and closing it. They have been observed to emit light in short flashes or long glows Kubodera et al., 2007. The former is associated with prey capture, and is believed to be a final illumination of the target before seizure. Long glows are thought to be a form of intra-specific communication, such as a means for locating mates.

T. danae terminal photophores (Tolweb.org).

(TONMO.com).

Meet the Family

Below we have the species that have been attributed to the family Octpoteuthidae. Much revision has taken place, though much more is needed to get a real sense of which species are valid and their relationship to each other.

In the genus Octopoteuthis, so far we have O. longiptera being designated nomen dubium (invalid), so we’ll just cross that one off the list. Following its description, O. persica was found to actually just be a paralarva of Taningia, so we’ll cross that one off as well. That leaves us with 7 nominal species of Octopoteuthis: danae, deletron, indica, megaptera, neilseni, rugosa, and sicula (with sicula also being the type species of the genus). The genus Taningia comprises one species, Taningia danae, making it necessarily the type of the genus. T. danae is also known as the “world’s biggest flasher” (*snicker*) due to its large photophores borne on arm pair II.

Distribution

And where do all these amazing species live? Well, the short answer is that we don't really know for sure. As will be the case for most of these posts, the majority of data available is on Taningia danae though there is limited information on some Octopoteuthis species.

Taningia is unique among the cephalopods in that it appears to have an almost worldwide distribution encompassing a variety of habitats. Most distribution data comes from stomach content analysis of sperm whales, once a highly exploited species. Beaks of T. danae have been recovered from the whales in the western North Atlantic, off Bermuda, Hawaii, South Georgia, South Africa, Japan, Australia, New Zealand, and the Azores. Thus, its geographical distribution can be described as cosmopolitan to the exclusion of polar regions (they tend to prefer warm, temperate, and sub-boreal waters).

Beaks in the stomach of a sperm whale (Source).

Taningia is typically a mesopelagic squid though they will venture into deeper bathypelagic waters, especially for spawning. Kubodera et al. (2007) found adult individuals over a range of depths from 240 to 940 m. The squid were observed to frequent deeper waters during the day. At night, squid were found in shallower waters (240 - 650 m), having completed a vertical migration to follow their migrating mesopelagic prey. Taningia can be found in all major ocean basins, in central waters, near oceanic islands, and near continental slopes.

Distribution map for T. danae (Cephbase.org).

Specimens of most Octopoteuthis species are pretty scarce, and thus distribution maps yield few patterns. The distribution of O. deletron has been described as confined to temperate Pacific Ocean habitats. This species tends to be found in the Eastern North Pacific, from off Baja California to Alaska and off northern Peru and possibly off eastern Honshu. Members of Octopoteuthis are all thought to be mesopelagic residents, undergoing vertical migration similar to T. danae.

Distribution map for O. megaptera (Cephbase.org).

"So honey, what looks good?"

"So, just what is on the menu for our friendly octopoteuthids," I hear you ask. Well, generally it consists of prey items ranging from mesopelagic fish, to crustaceans, to fellow squid! Octopoteuthids are squid after all, and they tend not to be prone towards the veggies.

Stomach content analysis on Taningia danae specimens has repeatedly identified the remains of blue whiting, Micromesistius poutassou, while also finding crustacean exoskeleton fragments and hooks and beaks of Gonatus species (González et al., 2003). The diet of Octopoteuthis species remains a mystery though is also likely composed of a mixture of fish, crustaceans, and cephalopods.








What is better understood is who the octopoteuthids feed. Beaks attributed to the family have been found in the stomachs of many large marine mammals, including sperm whales, Cuvier's beaked whales, bottlenose whales, Risso's dolphins, and northern elephant seals. They are also taken by active pelagic fish species, such as blue sharks and swordfish, and oceanic birds such as albatross. That these birds are able to catch such deep dwelling squid is striking, though they may catch them at night when the squid migrate vertically towards the surface.
Images:
Blue whiting Shrimp Gonatus sp. Sperm whale Albatross Blue shark

♪Let's talk about sex, baby!♫

If only Salt-N-Pepa knew...

In fact, not many of us do, for most of the reproductive cycle of octopoteuthids, and even the systems involved, remains a mystery. What scant information we do have is largely limited to Taningia danae, and thus the majority of this post will relate to them. Age at maturity is unknown, though two females with maturing eggs were aged at 21 and 33 months (González et al., 2003). While it appear T. danae is sexually dimorphic in terms of size, only one mature male specimen has ever been examined and information on females is almost as scarce. What is know is that instead of having a hectocotylus (a modified arm for spermatophore transfer) mature males have a large penis that can actually protrude greatly from the mantle cavity (González et al., 2003). This is also true of Octopoteuthis deletron, and likely other members of the genus. Males use this to hydraulically implant mature spermatophores into a females mantle and arm tissue. Presumably, following copulation she manipulates these into her mantle cavity with her arms.

While unconfirmed, it is believed that octopoteuthids spawn in deep water (400-600m) and in association with the bottom. Variable egg maturity was observed in two immature or maturing female T. danae specimens, and a broad size range at maturity has also been noted. These lines of evidence lend support to the theory that they are multiple spawners, not terminal. This life history style has traditionally been considered atypical of cephalopods, though is increasinly believed true for deep-water species. While the number of eggs laid at a time remains unknown, one maturing female's fecundity was estimated at 5 X 10⁶ oocytes (González et al., 2003). Mature eggs of O. deletron are usually around 2 mm in diameter. The paralarvae (young squid following hatching) of Octopoteuthis have not been formally described.

Descriptions of T. danae paralarvae are available, and they are characterized by enlarged suckers on the thick tentacles (remember they will lose these appendages) and enlarged armtips on a pair of arms due to the growing photophores. Paralarvae are presumably pelagic and predatory on small crustaceans and other zooplankton.

Juvenile T. danae in an aquarium (Tolweb.org).

Multimedia

Here are some really amazing videos of adult Taningia danae at depth in the wild. All videos are from Kubodera et al., 2007.

An adult attacking the baited line.

T. danae attacking the rig lights!

Short flashes of bioluminescent light from the large photophores.

Annotated Bibliography

Here is just a selection of the papers out there on this fascinating family of squid.

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Santos, M.B., G.J. Pierce, A.F. González, F. Santos, M.A. Vázquez, M.A. Santos, and M.A. Collins. 2001. First records of Taningia danae (Cephalopoda: Octopoteuthidae) in Galician waters (north-west Spain) and in Scottish waters (UK). Journal of the Marine Biological Association of the United Kingdom 81:355-356.

Taningia danae is a large squid that inhabits the deep ocean worldwide, though mainly tropical to subtropical water. There is evidence that paralarvae and juveniles are present in the mid North Atlantic from captured specimens and sperm whale stomach contents. However, are any post-juvenile or reproductively active individuals present in these waters as well?

Santos et al. report on the first records of specimens of Taningia danae from Galician and Scottish waters. A mature or maturing female was caught at 400 m from Galician waters, while a juvenile was caught at 800 m from the waters around Scotland. Both specimens were caught independently in trawls. Statoliths from the female were ground and examined to estimate age, and the contents of her stomach were inspected.

Estimates placed the female at 542 days old, and with a mantle length of 1.6 m and a weight of 61.4 kg. The juvenile was a mere 32 mm mantle length. From examination of the stomach contents it appears that the female was feeding on blue whiting, Micromesistius poutassou.

The positive identification of a post-juvenile Taningia danae, the mature or maturing female, is a first for these waters. These deep-water squid are rarely seen, making every opportunity to examine them valuable and insightful.
Link

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González, A.F., A. Guerra, and F. Rocha. 2003. New data on the life history and ecology of the deep-sea hooked squid Taningia danae. Sarsia 88:297–301.

As a deep-water squid, most of Taningia danae’s habits remain a mystery. What does it eat? How or even where does it reproduce? The capture of three individuals in northern Spanish waters shed much light on their species and themselves.

Specimens were caught on the Carrandi fishing grounds of Spain between depths of 400 and 600 m by the pair trawler Boer. Full morphometric measurements were taken, statoliths were ground for aging, and the stomach contents and reproductive systems were examined.

González et al. describe the heaviest recorded female and the first mature male of T. danae, with the third specimen being another female. As the heaviest individual, the first female weighed 124 kg and measured 132.0 cm mantle length, with an estimated fecundity of 5 x 10⁶ oocytes. Both females appeared to have eggs at various stages of development. Strikingly, the male’s penis extended 23 cm outside of its mantle cavity, giving it a total length of 73 cm, and contained mature spermatophores. Two of the three stomachs contained food items, and comprised blue whiting, Micromesistius poutassou, crustacean exoskeleton, and hooks and beaks from squid of the genus Gonatus.

The capture of these squid supports the idea that post-juvenile and adult individuals are present this far north. The variable egg maturation demonstrated in both females is indicative of multiple spawning, which is not typical of shallow cephalopod species but is increasingly believed true for deep-water species. Additionally, capture at depths of 400 to 600 m is not contrary to the hypothesis that this is a bottom spawning species. Due to the presence of a large penis in males, González et al. concluded that males implant spermatophores in the mantle and arms of females as demonstrated in other similarly equipped squid species.

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Kubodera, T., Y. Koyama, and K. Mori. 2007. Observations of wild hunting behaviour and bioluminescence of a large deep-sea, eight-armed squid, Taningia danae. Proceedings of the Royal Society B 274:1029–1034.

Taningia danae is a large mesopelagic squid that is believed to occur commonly throughout tropical and subtropical waters, yet a living adult specimen has never been observed. The species is characterized by the presence of two large photophores borne on the tips of two of its arms. Given its preference for deeper water, what would this large predatory squid look like in the wild and how does it use its large photophores?

Kubodera et al. investigated this by deploying a high definition underwater camera system. The camera was baited with a bag of shrimp chum and a fresh Japanese common squid, Todarodes pacificus, and bore lights for illumination. The system was deployed at depths ranging between 240 and 940 m.

The resulting video footage showed individuals demonstrating attacking and bioluminescent behaviours. Consistent with its predatory nature, T. danae was shown to be an active swimmer, capable of speed bursts and quick direction changes. Light from photophores appeared in two forms: short flashes associated with a final attack sequence on the bait, and disjointed long glows suggestive of courtship behaviour.

Kubodera et al. provided the first footage of live adult T. danae in the wild. The footage showed that T. danae is an active predator and employs its photophores in a number of different behaviours. Flapping the large lateral fins provided most of the propulsion necessary, and its flexible body accommodated sharp direction changes.
Link

The Links

For some more information on octopoteuthids and other cephalopods checkout some of these great links:

TolWeb.org - Specifically here
CephBase.org - Specifically here
The Octopus News Magazine Online (TONMO)
Wikipedia
The Cephalopod Page - Specifically the "Batttle of the Giants" chapter from "The Search for the Giant Squid" by Richard Ellis

T. danae (Source).