Opisthoteuthis agassizii

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Opisthoteuthis agassizii
Dumbo Octopus (49203817176).jpg
Specimen photographed on a NOAA expedition off the southeastern USA, 2019. [1]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Family: Opisthoteuthidae
Genus: Opisthoteuthis
Species:
O. agassizii
Binomial name
Opisthoteuthis agassizii
Verrill, 1883 [3] [4]

Opisthoteuthis agassizii is a lesser-known, deep-sea octopus first described in 1883 by Addison E. Verrill. [5]

Contents

Like all cirrate octopuses, O. agassizii has fleshy fins to aid in swimming and a small internal shell. Males are up to four times heavier than females, [6] and their suckers are proportionally larger. Both sexes are small.

This species is found in the north-west, and western Atlantic coasts, over depths of 277 to 1,935 meters (historic records from east Atlantic coasts were likely misidentifications with other Opisthoteuthis). [5] [7] Like other opisthoteuthids, they occupy the benthic zone, living on or near the seafloor. [2]

These octopuses most likely prey on polychaete worms and crustaceans that live on or just above the seafloor. [8]

All females of O. agassizii become sexually mature when they reach approximately 190 grams (6.7 ounces) and all males are sexually mature once they reach approximately 95 g (3.4 oz). However, both sexes continue to grow after they reach maturity.

While O. agassizii exists across a wide depth range, heavier octopuses generally live 700 meters or more from the ocean's surface. As age and sexual maturity correlate with weight in this species, this means octopuses at a greater depth are more likely to be sexually mature. [6]

Anatomy and physiology

Size

Opisthoteuthis agassizzi octopuses are small compared to most octopuses; males weigh up to four times more than females, and have a mantle length from 1 up to 2+1⁄2 inches. Males suckers are also much larger. The largest specimen, a male, had a mantle (the body not including the octopus' arms) reaching 63 mm, a little under two and a half inches. The largest mantle length for a female was recorded at 56mm. [5] Body size correlates with age and sexual maturity, so octopuses found at 700 meters or more from the surface are almost always sexually mature. [6]

External and internal characteristics

Fins curl around the mantle of the octopus and aid in swimming and balance, supported by cartilage. A study in a sister species, Opisthoteuthis grimaldii, observed them using the fins to maintain a vertical position in the water relative to the mantle and sea floor. [9] They have eight arms lined with a single line of suckers. Like other octopuses, they use their arms to move about, and their suckers aid in gripping rocks or other objects along their path. Most specimens have been observed having 58-80 suckers per arm. [10] O. agassizii do not have mechanoreceptors lining their suckers like non-cirrate octopuses, nor do they have cilia; instead there are microvilli structures that appear to be used for olfaction. There are two eyes visible within the mantle, but the optic system is much reduced compared to other species within the order Otcopoda. [8] They have a very small shell, like most octopuses do, and have cirri along the undersides of their tentacles.

Oral view of arms and leg, as well as leg webbing Opsithoteuthis Agassizii.jpg
Oral view of arms and leg, as well as leg webbing

Lifecycle

Opisthoteuthis agassizii exhibit extended spawning, and the number of egg cells in a female does not appear to correlate with body mass like in most octopus species. One study found that the total weight of a female didn't correlate with the number of oocytes in her body, implying that females continue to produce and lose eggs over the course of their lives. In other words, an octopus of this species might breed multiple times in its life. This is markedly different from most octopuses; the majority only reproduce once in a lifetime. [6] The species appears to continue to grow well after reaching the age of reproduction; one study found that males weighing anywhere from 95 to 5400g were sexually mature, while females from weights of 190g onward to 1650g were sexually mature, further indicating that O. agasizzi has a reproductive cycle differing from that of other octopus species. The exact details on egg development and their reproductive cycle, however, is largely unknown; indeed, only a few octopus species have been studied extensively with regards to reproduction and mating.

Opisthoteuthis agassizii are free-swimming, and spend much of their life just above and on the seafloor (usually below 700 meters). [8] Their weight corresponds with how deep in the ocean they live, however, with some found at depths as shallow as 227 meters. [2] Most are found at much lower depths, up to 1,935 meters below sea level, hence their classification as a deep-sea octopus. [5]

Distribution

Opisthoteuthis agassizii has historically been recorded from both the eastern and western sides of the Atlantic, including along the coasts of the Caribbean, south of Ireland down to the Mediterranean, [8] [11] as well as the Gulf of Guinea, Namibia and most of the rest of the West African coast. [12]

However, a revision of the Atlantic Opisthoteuthis published in 2002, [7] indicated that O. agassizii is restricted to the western Atlantic, occurring from the east coast of the US and down as far south as Brazil. The species occurs over depths ranging from 227 to 1935 m. Records from the eastern Atlantic (Mediterranean, Ireland, Western Africa etc.) were likely misidentifications with species O. calypso , O. massyae , and O. grimaldii. [7]

Behavior and ecology

Feeding

Opisthoteuthis agassizii are predacious and tend to eat benthic prey, such as amphipods and polychaetes, but their diet frequently expands to include copepods, decapods, crustaceans, and even microbivalves and microgastropods. There is a slight shift in primary prey as they grow in size; a study found that O. agassizzi under 500g fed mainly on amphipods, while those above 500g ate more polychaetes. [8] They will hunt at any time of day, and most of their preferred prey is slow-swimming. As they are a cirrate octopod, they do not possess a radula, and thus consume prey whole. [10]

Movement

Most of their time is spent along the seafloor, hunting prey and crawling using their eight arms, but O. agassizii can swim like all octopuses are capable of doing. They use their two fins along the mantle for stabilizing themselves, having control over direction, and staying oriented in the water. A study on a related species also showed similar fins being used to aid in buoyancy and ballooning, a common defense mechanism in octopoda. [9] Cirrate octopods cannot, however, swim via jet propulsion, and thus O. agassizii specimens use their fins to drift or pump their arms in contractions to move in a more controlled fashion. [13]

Etymology and phylogeny

Opisthoteuthis agassizii was first named by Verrill in 1883 as just Opisthoteuthis, [14] though the name was soon changed to the now-accepted Opisthoteuthis agassizii. Some work has been done on organizing the Cirrates, but the group is very understudied and only a few theories have been proposed as to their organization into any sort of phylogenetic tree. The most extensive work has been done by Piertney, who used ribosomal DNA sequencing to place the Opisthoteuthidae as a sister family of Grimpoteuthis, Luteuthis, and Cryptoteuthis. [15]

Related Research Articles

<i>Grimpoteuthis</i> Genus of cephalopods known as the dumbo octopuses

Grimpoteuthis is a genus of pelagic cirrate (finned) octopods known as the dumbo octopuses. The name "dumbo" originates from their resemblance to the title character of Disney's 1941 film Dumbo, having two prominent ear-like fins which extend from the mantle above each eye. There are 17 species recognized in the genus. Prey include crustaceans, bivalves, worms and copepods. The average life span of various Grimpoteuthis species is 3–5 years.

<span class="mw-page-title-main">Umbrella octopus</span> Family of molluscs

Umbrella octopuses are a group of pelagic octopuses. Umbrella octopuses are characterized by a web of skin between the arms, causing them to somewhat resemble an opened umbrella when the arms are spread.

<i>Opisthoteuthis californiana</i> Species of cephalopod known as the flapjack octopus

Opisthoteuthis californiana, also known as the flapjack octopus, or flapjack devilfish is a species of umbrella octopus.

<i>Stauroteuthis syrtensis</i> Species of octopus

Stauroteuthis syrtensis, also known as the glowing sucker octopus or bioluminescent octopus, is a species of small pelagic octopus found at great depths in the north Atlantic Ocean. It is one of a very small number of octopuses to exhibit bioluminescence.

<i>Cirroteuthis</i> Genus of octopuses

Cirroteuthis muelleri, also known as the big-finned jellyhead, was the first cirrate octopus species to be scientifically described. It is closely related to the genus Cirrothauma within the family Cirroteuthidae. At present the genus contains a single recognized species restricted to the Arctic Ocean and northern basins of the Atlantic and Pacific, but other species may be present in the southern hemisphere.

Stauroteuthis gilchristi is a species of small pelagic octopus found at great depths in the south Atlantic Ocean. It is believed to be one of a very small number of octopuses to exhibit bioluminescence, like its sister taxon Stauroteuthis syrtensis.

<i>Opisthoteuthis</i> Genus of octopuses

Opisthoteuthis is a genus of cirrate octopuses, sometimes known as flapjack octopuses, which are found in all the world's oceans.

<i>Opisthoteuthis chathamensis</i> Species of octopus

Opisthoteuthis chathamensis, commonly known as the roughy umbrella octopus, is a species of cirrate octopus restricted to demersal habitats surrounding the Chatham Rise in New Zealand. It is commonly known as the roughy umbrella octopus.

Opisthoteuthis calypso or calypso flapjack octopus is a species of genus Opisthoteuthis, which are known as the cirrate octopuses. Octopuses in this genus are known as the flapjack octopuses and can be found in a variety of oceans across the world.

Opisthoteuthis borealis is a lesser-known species of octopus found near Greenland and Iceland, especially in the Davis Strait. The species was described from 9 specimens, and is one of the most recent Opisthoteuthis species described. Not much is known about it besides its anatomy and habitat.

Opisthoteuthis bruuni is a species of finned cirrate octopus found along the western coast of South America. Their tissue is almost jelly-like, and they have short, round bodies.

<i>Opisthoteuthis depressa</i> Species of octopus

Opisthoteuthis depressa, also known as the Japanese flapjack octopus, is an octopus found in waters near Japan.

<i>Opisthoteuthis extensa</i> Species of octopus

Opisthoteuthis extensa is a species of octopus found off the west coast of Sumatra, an Indonesian island. It lives at a recorded depth of 768 m (2,520 ft). O. extensa lives in a benthic habitat, like many other cirrate octopuses. It occupies a deep part of the ocean where little sunlight penetrates.

<i>Opisthoteuthis grimaldii</i> Species of octopus

Opisthoteuthis grimaldii is an octopus found near the Azores.

Opisthoteuths hardyi is a lesser-known octopus species. It was described in 2002 from a male caught off the Shag Rocks, which are far south in the Atlantic Ocean near the Falkland Islands.

Opisthoteuthis massyae is an octopus living in the eastern Atlantic Ocean.

Opisthoteuthis persephone is a cirrate octopus living south of Australia. In particular, it lives in waters off Tasmania, Victoria, New South Wales, and South Australia. The octopus has been found 270–540 m (885.8–1,771.7 ft) deep. It lives near and directly above the seafloor. S. Stillman Berry was the first to scientifically describe this species after capturing eight specimens while aboard the F.I.S. Endeavour in the early 1910s. In describing O. persephone, Berry called it an "exceedingly interesting octopod".

Opisthoteuthis philipii is an octopus of the Indian Ocean. It lives off the coast of Kerala, India. Known specimens were found between 275–365 m (902–1,198 ft) deep in the Arabian Sea near Alappuzha.

Opisthoteuthis pluto is a deep-sea cirrate octopus found in the Great Australian Bight south of Australia. They live 270–810 m (890–2,660 ft) below the surface in the bathyal zone. Although their habitat is threatened, it is unclear how the species is affected, if at all. O. pluto is named for the Greek and Roman god of the Underworld.

Opisthoteuthis robsoni, also known as the deep-water umbrella octopus, is a deep-sea octopus living off New Zealand on the Chatham Rise. It has been found from 1,178–1,723 m (3,865–5,653 ft) below the surface. Not much is known about the octopus' habitat or life cycle, as only four specimens have been found. It occupies the benthic zone, or the seafloor and the water directly above it. O. robsoni eats large amphipods.

References

  1. ↑ "Dive 12: "Berg Bits"". Ocean Exploration and Research. NOAA. November 19, 2019. Retrieved 15 August 2020.
  2. 1 2 3 Lyons, G.; Allcock, L. (2014). "Opisthoteuthis agassizii". IUCN Red List of Threatened Species . 2014: e.T163377A1003617. doi: 10.2305/IUCN.UK.2014-3.RLTS.T163377A1003617.en . Retrieved 20 November 2021.
  3. ↑ "Species details". Catalogue of Life. Retrieved 15 August 2020.
  4. ↑ "Opisthoteuthis agassizii". Ocean Biogeographic Information System. Retrieved 28 April 2019.
  5. 1 2 3 4 Vecchione, Michael; Villanueva, Roger; Richard, Young E. "Opisthoteuthis agassizii". Tree of Life Web Project. Retrieved 15 August 2020.
  6. 1 2 3 4 Villanueva, Roger (May 19, 1992). "Continuous spawning in the cirrate octopods Opisthoteuthis agassizii and O. vossi: features of sexual maturation defining a reproductive strategy in cephalopods". Marine Biology. 114 (2). Barcelona, Spain: 265–275. doi:10.1007/BF00349529. S2CID   85085295.
  7. 1 2 3 Villanueva, Roger; Collins, Martin; Sánchez, Pilar; Voss, Nancy (2002). "Systematics, distribution and biology of the cirrate octopods of the genus Opisthoteuthis (Mollusca, Cephalopoda) in the Atlantic Ocean, with description of two new species". Bulletin of Marine Science. 71 (2): 933–985.
  8. 1 2 3 4 5 Villanueva, Roger; Guerra, Angel (September 1991). "Food and Prey Detection in Two Deep-Sea Cephalopods: Opisthoteuthis Agassizi and O. Vossi (Octopoda: Cirrata)". Bulletin of Marine Science. 49. University of Miami - Rosenstiel School of Marine and Atmospheric Science: 288–299.
  9. 1 2 Villanueva, Roger (June 2000). "Observations on the behaviour of the cirrate octopod Opisthoteuthis grimaldii (Cephalopoda)". Journal of the Marine Biological Association of the United Kingdom. 80 (3): 555–556. doi:10.1017/s0025315400002307. ISSN   0025-3154. S2CID   85020724.
  10. 1 2 3 "Opisthoteuthis agassizii". tolweb.org. Retrieved 2020-11-11.
  11. ↑ Villanueva, Roger (1992). "Deep-sea cephalopods of the north-western Mediterranean: indications of up-slope ontogenetic migration in two bathybenthic species". Journal of Zoology. 227 (2): 267–276. doi:10.1111/j.1469-7998.1992.tb04822.x. ISSN   1469-7998.
  12. ↑ Adam, W. (1962). "Céphalopodes de l'archipel du Cap-Vert, de l'Angola et du Mozambique". Memórias da Junta de Investigações do Ultramar.
  13. ↑ Villanueva, R.; Segonzac, M.; Guerra, A. (1997). "Locomotion modes of deep-sea cirrate octopods (Cephalopoda) based on observations from video recordings on the Mid-Atlantic Ridge". Marine Biology . 129: 113–122. doi:10.1007/S002270050152. S2CID   85848021.
  14. ↑ "WoRMS - World Register of Marine Species - Opisthoteuthis Verrill, 1883". www.marinespecies.org. Retrieved 2020-11-09.
  15. ↑ Piertney, Stuart B.; Hudelot, Cendrine; Hochberg, F. G.; Collins, Martin A. (May 2003). "Phylogenetic relationships among cirrate octopods (Mollusca: Cephalopoda) resolved using mitochondrial 16S ribosomal DNA sequences". Molecular Phylogenetics and Evolution. 27 (2): 348–353. doi:10.1016/s1055-7903(02)00420-7. ISSN   1055-7903. PMID   12695097.
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