Deep-sea gigantism

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Examination of a 9 m (30 ft) giant squid, the second largest cephalopod, that washed ashore in Norway. Giant squid Ranheim2.jpg
Examination of a 9 m (30 ft) giant squid, the second largest cephalopod, that washed ashore in Norway.

In zoology, deep-sea gigantism or abyssal gigantism is the tendency for species of deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range. Proposed explanations for this type of gigantism include necessary adaptation to colder temperature, food scarcity, reduced predation pressure and increased dissolved oxygen concentrations in the deep sea. The harsh conditions and inhospitality of the underwater environment in general, as well as the inaccessibility of the abyssal zone for most human-made underwater vehicles, have hindered the study of this topic.

Contents

Taxonomic range

In marine crustaceans, the trend of increasing size with depth has been observed in mysids, euphausiids, decapods, isopods and amphipods. [1] [2] Non-arthropods in which deep-sea gigantism has been observed are cephalopods, cnidarians, and eels from the order Anguilliformes. [3]

Other [animals] attain under them gigantic proportions. It is especially certain crustacea which exhibit this latter peculiarity, but not all crustacea, for the crayfish like forms in the deep sea are of ordinary size. I have already referred to a gigantic Pycnogonid [sea spider] dredged by us. Louis Agassiz dredged a gigantic Isopod 11 inches [28 centimetres] in length. We also dredged a gigantic Ostracod. For over 125 years, scientists have contemplated the extreme size of Bathynomus giganteus . – Henry Nottidge Moseley, 1880 [4]

Notable organisms that exhibit deep-sea gigantism include the big red jellyfish, [5] Stygiomedusa jellyfish, the giant isopod, [4] giant ostracod, [4] the giant sea spider, [4] the giant amphipod, the Japanese spider crab, the giant oarfish, the deepwater stingray, the seven-arm octopus, [6] and a number of squid species: the colossal squid (up to 14 m in length), [7] the giant squid (up to 12 m), [7] Megalocranchia fisheri , robust clubhook squid, Dana octopus squid, cockatoo squid, giant warty squid, and the bigfin squids of the genus Magnapinna.

Deep-sea gigantism is not generally observed in the meiofauna (organisms that pass through a 1 mm mesh), which actually exhibit the reverse trend of decreasing size with depth. [8]

Explanations

Lower temperature

In crustaceans, it has been proposed that the explanation for the increase in size with depth is similar to that for the increase in size with latitude (Bergmann's rule): both trends involve increasing size with decreasing temperature. [1] The trend with latitude has been observed in some of the same groups, both in comparisons of related species, as well as within widely distributed species. [1] Decreasing temperature is thought to result in increased cell size and increased life span (the latter also being associated with delayed sexual maturity [8] ), both of which lead to an increase in maximum body size (continued growth throughout life is characteristic of crustaceans). [1] In Arctic and Antarctic seas where there is a reduced vertical temperature gradient, there is also a reduced trend towards increased body size with depth, arguing against hydrostatic pressure being an important parameter. [1]

Temperature does not appear to have a similar role in influencing the size of giant tube worms. Riftia pachyptila , which lives in hydrothermal vent communities at ambient temperatures of 2–30 °C, [9] reaches lengths of 2.7 m, comparable to those of Lamellibrachia luymesi , which lives in cold seeps. The former, however, has rapid growth rates and short life spans of about 2 years, [10] while the latter is slow growing and may live over 250 years. [11]

Food scarcity

Food scarcity at depths greater than 400 m is also thought to be a factor, since larger body size can improve ability to forage for widely scattered resources. [8] In organisms with planktonic eggs or larvae, another possible advantage is that larger offspring, with greater initial stored food reserves, can drift for greater distances. [8] As an example of adaptations to this situation, giant isopods gorge on food when available, distending their bodies to the point of compromising ability to locomote; [12] they can also survive 5 years without food in captivity. [13] [14]

According to Kleiber's law, [15] the larger an animal gets, the more efficient its metabolism becomes; i.e., an animal's basal metabolic rate scales to roughly the ¾ power of its mass. Under conditions of limited food supply, this may provide additional benefit to large size.

Reduced predation pressure

An additional possible influence is reduced predation pressure in deeper waters. [16] A study of brachiopods found that predation was nearly an order of magnitude less frequent at the greatest depths than in shallow waters. [16]

Increased dissolved oxygen

Dissolved oxygen levels are also thought to play a role in deep-sea gigantism. A 1999 study of benthic amphipod crustaceans found that maximum potential organism size directly correlates with increased dissolved oxygen levels of deeper waters. [17] The solubility of dissolved oxygen in the oceans is known to increase with depth because of increasing pressure, decreasing salinity levels and temperature. [17]

The proposed theory behind this trend is that deep-sea gigantism could be an adaptive trait to combat asphyxiation in ocean waters. [18] Larger organisms are able to intake more dissolved oxygen within the ocean, allowing for sufficient respiration. However, this increased absorption of oxygen runs the risk of toxicity poisoning where an organism can have oxygen levels that are so high that they become harmful and poisonous. [18]

See also

Related Research Articles

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Plankton are the diverse collection of organisms that drift in water but are unable to actively propel themselves against currents. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales.

<span class="mw-page-title-main">Zooplankton</span> Heterotrophic protistan or metazoan members of the plankton ecosystem

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Aurelia aurita is a species of the family Ulmaridae. All species in the genus are very similar, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus.

<span class="mw-page-title-main">Bergmann's rule</span> Biological rule stating that larger size organisms are found in colder environments

Bergmann's rule is an ecogeographical rule that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, while populations and species of smaller size are found in warmer regions. The rule derives from the relationship between size in linear dimensions meaning that both height and volume will increase in colder environments. Bergmann's rule only describes the overall size of the animals, but does not include body proportions like Allen's rule does.

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<span class="mw-page-title-main">Isopoda</span> Order of arthropods

Isopoda is an order of crustaceans. Members of this group are called Isopods and include both terrestrial and aquatic species such as woodlice. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.

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<i>Bathynomus giganteus</i> Species of crustacean

Bathynomus giganteus is a species of aquatic crustacean, of the order Isopoda. It is a member of the giant isopods (Bathynomus), and as such it is related—albeit distantly—to shrimps and crabs. It was the first Bathynomus species ever documented and was described in 1879 by French zoologist Alphonse Milne Edwards after the isopod was found in fishermen's nets off the coast of the Dry Tortugas in the Gulf of Mexico.

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<i>Phacellophora camtschatica</i> Species of jellyfish

Phacellophora camtschatica, commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the family Phacellophoridae. This species can be easily identified by the yellow coloration in the center of its body which closely resembles an egg yolk, hence its common name. Some individuals can have a bell close to 60 cm (2 ft) in diameter, and most individuals have 16 clusters of up to a few dozen tentacles, each up to 6 m (20 ft) long. A smaller jellyfish, Cotylorhiza tuberculata, typically found in warmer water, particularly in the Mediterranean Sea, is also popularly called a fried egg jellyfish. Also, P. camtschatica is sometimes confused with the Lion's mane jellyfish.

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<span class="mw-page-title-main">Atolla jellyfish</span> Species of jellyfish

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<span class="mw-page-title-main">Colossal squid</span> Species of squid

The colossal squid is the largest member of its family Cranchiidae, the cockatoo or glass squids, with its second largest member being Megalocranchia fisheri. It is sometimes called the Antarctic cranch squid or giant squid and is believed to be the largest squid species in terms of mass. It is the only recognized member of the genus Mesonychoteuthis and is known from only a small number of specimens. The species is confirmed to reach a mass of at least 495 kilograms (1,091 lb), though the largest specimens—known only from beaks found in sperm whale stomachs—may perhaps weigh as much as 600–700 kilograms (1,300–1,500 lb), making it the largest known invertebrate. Maximum total length has been estimated between 10 metres (33 ft) and 14 metres (46 ft) but the former estimate is more likely. The colossal squid has the largest eyes of any known creature ever to exist, with an estimated diameter of 27–30 cm (11–12 in) to 40 cm (16 in) for the largest collected specimen.

<span class="mw-page-title-main">Giant isopod</span> Genus of crustaceans

A giant isopod is any of the almost 20 species of large isopods in the genus Bathynomus. They are abundant in the cold, deep waters of the Atlantic, Pacific, and Indian Oceans. Bathynomus giganteus, the species upon which the generitype is based, is often considered the largest isopod in the world, though other comparably poorly known species of Bathynomus may reach a similar size. The giant isopods are noted for their resemblance to the much smaller common woodlouse, to which they are related.

<span class="mw-page-title-main">Deep-sea community</span> Groups of organisms living deep below the sea surface, sharing a habitat

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<span class="mw-page-title-main">Wildlife of Antarctica</span> Antarctic wildlife

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<span class="mw-page-title-main">Jellyfish bloom</span>

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References

  1. 1 2 3 4 5 Timofeev, S. F. (2001). "Bergmann's Principle and Deep-Water Gigantism in Marine Crustaceans". Biology Bulletin of the Russian Academy of Sciences. 28 (6): 646–650. doi:10.1023/A:1012336823275. S2CID   28016098.
  2. ↑ C., McClain; M., Rex (1 October 2001). "The relationship between dissolved oxygen concentration and maximum size in deep-sea turrid gastropods: an application of quantile regression". Marine Biology. 139 (4): 681–685. Bibcode:2001MarBi.139..681C. doi:10.1007/s002270100617. ISSN   0025-3162. S2CID   83747571.
  3. ↑ Hanks, Micah. "Deep Sea Gigantism: Curious Cases of Mystery Giant Eels". MysteriousUniverse. Retrieved 5 May 2019.
  4. 1 2 3 4 McClain, Craig (14 January 2015). "Why isn't the Giant Isopod larger?". Deep Sea News. Retrieved 1 March 2018.
  5. ↑ Smithsonian Oceans. "Big Red Jellyfish". Smithsonian Oceans. Retrieved 5 May 2019.
  6. ↑ Hoving, H. J. T.; Haddock, S. H. D. (27 March 2017). "The giant deep-sea octopus Haliphron atlanticus forages on gelatinous fauna". Scientific Reports. 7: 44952. Bibcode:2017NatSR...744952H. doi:10.1038/srep44952. PMC   5366804 . PMID   28344325.
  7. 1 2 Anderton, Jim (22 February 2007). "Amazing specimen of world's largest squid in NZ". New Zealand Government. Archived from the original on 23 May 2010.
  8. 1 2 3 4 Gad, G. (2005). "Giant Higgins-larvae with paedogenetic reproduction from the deep sea of the Angola Basin? Evidence for a new life cycle and for abyssal gigantism in Loricifera?". Organisms Diversity & Evolution. 5: 59–75. doi:10.1016/j.ode.2004.10.005.
  9. ↑ Bright, M.; Lallier, F. H. (2010). The biology of vestimentiferan tubeworms (PDF). Oceanography and Marine Biology - an Annual Review. Vol. 48. Taylor & Francis. pp. 213–266. doi:10.1201/ebk1439821169. ISBN   978-1-4398-2116-9. Archived from the original (PDF) on 31 October 2013. Retrieved 30 October 2013.
  10. ↑ Lutz, R. A.; Shank, T. M.; Fornari, D. J.; Haymon, R. M.; Lilley, M. D.; Von Damm, K. L.; Desbruyeres, D. (1994). "Rapid growth at deep-sea vents". Nature. 371 (6499): 663. Bibcode:1994Natur.371..663L. doi:10.1038/371663a0. S2CID   4357672.
  11. ↑ MacDonald, Ian R. (2002). "Stability and Change in Gulf of Mexico Chemosynthetic Communities" (PDF). MMS. Archived from the original (PDF) on 1 February 2017. Retrieved 30 October 2013.
  12. ↑ Briones-Fourzán, Patricia; Lozano-Alvarez, Enrique (1991). "Aspects of the biology of the giant isopod Bathynomus giganteus A. Milne Edwards, 1879 (Flabellifera: Cirolanidae), off the Yucatan Peninsula". Journal of Crustacean Biology . 11 (3): 375–385. doi: 10.2307/1548464 . JSTOR   1548464.
  13. ↑ Gallagher, Jack (26 February 2013). "Aquarium's deep-sea isopod hasn't eaten for over four years". The Japan Times. Retrieved 21 May 2013.
  14. ↑ "I Won't Eat, You Can't Make Me! (And They Couldn't)". NPR. 22 February 2014. Retrieved 23 February 2014.
  15. ↑ Kleiber, M. (1947). "Body Size and Metabolic Rate". Physiological Reviews. 27 (4): 511–541. doi:10.1152/physrev.1947.27.4.511. PMID   20267758.
  16. 1 2 Harper, E. M.; Peck, L. S. (2016). "Latitudinal and depth gradients in marine predation pressure". Global Ecology and Biogeography. 25 (6): 670–678. Bibcode:2016GloEB..25..670H. doi: 10.1111/geb.12444 .
  17. 1 2 Chapelle, Gauthier; Peck, Lloyd S. (1999). "Polar gigantism dictated by oxygen availability". Nature. 399 (6732): 114–115. Bibcode:1999Natur.399..114C. doi:10.1038/20099. ISSN   0028-0836. S2CID   4308425.
  18. 1 2 Verberk, Wilco C. E. P.; Atkinson, David (2013). "Why polar gigantism and Palaeozoic gigantism are not equivalent: effects of oxygen and temperature on the body size of ectotherms". Functional Ecology. 27 (6): 1275–1285. Bibcode:2013FuEco..27.1275V. doi:10.1111/1365-2435.12152. hdl: 2066/123399 . ISSN   0269-8463. JSTOR   24033996. S2CID   5636563.
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