![]() ![]() Īccording to Kleiber's law, 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. 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 they can also survive 5 years without food in captivity. 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. Food scarcity įood 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. The former, however, has rapid growth rates and short life spans of about 2 years, while the latter is slow growing and may live over 250 years. Riftia pachyptila, which lives in hydrothermal vent communities at ambient temperatures of 2–30 ☌, reaches lengths of 2.7 m, comparable to those of Lamellibrachia luymesi, which lives in cold seeps. Temperature does not appear to have a similar role in influencing the size of giant tube worms. 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. Decreasing temperature is thought to result in increased cell size and increased life span (the latter also being associated with delayed sexual maturity ), both of which lead to an increase in maximum body size (continued growth throughout life is characteristic of crustaceans). 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. 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. – Henry Nottidge Moseley, 1880 Įxamples of deep-sea gigantism include the big red jellyfish, the giant isopod, giant ostracod, the giant sea spider, the giant amphipod, the Japanese spider crab, the giant oarfish, the deepwater stingray, the seven-arm octopus, and a number of squid species: the colossal squid (up to 14 m in length), the giant squid (up to 12 m), Onykia robusta, Taningia danae, Galiteuthis phyllura, Kondakovia longimana, and the bigfin squid.ĭeep-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. For over 125 years, scientists have contemplated the extreme size of Bathynomus giganteus. Louis Agassiz dredged a gigantic Isopod 11 inches in length. I have already referred to a gigantic Pycnogonid dredged by us. 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. Other attain under them gigantic proportions. Non-arthropods in which deep-sea gigantism has been observed are cephalopods, cnidarians, and eels from the order Anguilliformes. In marine crustaceans, the trend of increasing size with depth has been observed in mysids, euphausiids, decapods, isopods and amphipods. The inaccessibility of abyssal habitats has hindered the study of this topic. Proposed explanations for this type of gigantism include colder temperature, food scarcity, reduced predation pressure and increased dissolved oxygen concentrations in the deep sea. ![]() ![]() In zoology, deep-sea gigantism or abyssal gigantism is the tendency for species of invertebrates and other deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range. Tendency for deep-sea species to be larger than their shallower-water relativesĮxamination of a 9 m (30 ft) giant squid, the second largest cephalopod, that washed ashore in Norway. ![]()
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