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The term deep sea creature refers to animals that live below the
photic zone The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological pro ...
of the ocean. These creatures must survive in extremely harsh conditions, such as hundreds of bars of pressure, small amounts of oxygen, very little food, no sunlight, and constant, extreme cold. Most creatures have to depend on food floating down from above. These creatures live in very demanding environments, such as the
abyssal The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. "Abyss" derives from the Greek word , meaning bottomless. At depths of , this zone remains in perpetual darkness. It covers 83% of the total area of the ocean an ...
or
hadal The hadal zone, also known as the hadopelagic zone, is the deepest region of the ocean, lying within oceanic trenches. The hadal zone ranges from around below sea level, and exists in long, narrow, topographic V-shaped depressions. The cumula ...
zones, which, being thousands of meters below the surface, are almost completely devoid of light. The water is between 3 and 10 degrees Celsius and has low oxygen levels. Due to the depth, the pressure is between 20 and 1,000
bar Bar or BAR may refer to: Food and drink * Bar (establishment), selling alcoholic beverages * Candy bar * Chocolate bar Science and technology * Bar (river morphology), a deposit of sediment * Bar (tropical cyclone), a layer of cloud * Bar (un ...
. Creatures that live hundreds or even thousands of meters deep in the ocean have adapted to the high pressure, lack of light, and other factors.


Evolutionary adaptations of deep-sea creatures


Lack of light

The lack of light requires creatures to have special adaptations to find food, avoid predators, and find mates by creating their own light or having an ability to see in the dark.


Lack of resources

At this depth, there is not enough light for photosynthesis to occur and not enough oxygen to support animals with a high metabolism. To survive, creatures have slower metabolisms which require less oxygen; they can live for long periods without food. Most food either comes from organic material that falls from above or from eating other creatures that have derived their food through the process of
chemosynthesis In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules (usually carbon dioxide or methane) and nutrients into organic matter using the oxidation of inorganic compounds (e.g., hydrogen gas, hydrog ...
(the process of changing chemical energy into food energy). Because of the sparse distributions of creatures, there is always at least some oxygen and food. Also, instead of using energy to search for food, these creatures use particular adaptations to ambush prey. In turn, these creatures rely on large food particles, such as fragments of dead fish or other marine mammals, to fall from the surface. Although the falling food can support the population of the deep sea creatures, there can still be a lack of resources due to a middle population of fish consuming the fragments before making it to the bottom. Deep-sea vertebrates also have less muscle and less
ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...
bone. This lack of ossification was adapted to save energy when food is scarce.


Bioluminescence

Bioluminescence Bioluminescence is the production and emission of light by living organisms. It is a form of chemiluminescence. Bioluminescence occurs widely in marine vertebrates and invertebrates, as well as in some fungi, microorganisms including some ...
is the ability of an organism to create light through chemical reactions. Creatures use bioluminescence in many ways: to light their way, attract prey, or seduce a mate. Many underwater animals are bioluminescent—from the
viper fish A viperfish is any species of marine fish in the genus ''Chauliodus''. Viperfishes are mostly found in the mesopelagic zone and are characterized by long, needle-like teeth and hinged lower jaws. A typical viperfish grows to lengths of . Viper ...
to the various species of flashlight fish, named for their light. Some creatures, such as the
angler fish The anglerfish are fish of the teleost order Lophiiformes (). They are bony fish named for their characteristic mode of predation, in which a modified luminescent fin ray (the esca or illicium) acts as a lure for other fish. The luminescence c ...
, have a concentration of
photophores A photophore is a glandular organ that appears as luminous spots on various marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye; equipped with lenses, shutters, color filters and reflectors, h ...
in a small limb that protrudes from their bodies, which they use as a lure to catch curious fish. Bioluminescence can also confuse enemies. The chemical process of bioluminescence requires at least two chemicals: the light producing chemical called luciferin and the reaction causing chemical called luciferase.BL Web: Chemistry
/ref> The luciferase catalyzes the oxidation of the luciferin causing light and resulting in an inactive oxyluciferin. Fresh luciferin must be brought in through the diet or through internal synthesis.BL Web: Chemistry
/ref>


Chemosynthesis

Since, at such deep levels, there is little to no sunlight,
photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
is not a possible means of energy production, leaving some creatures with the quandary of how to produce food for themselves. For the
giant tube worm ''Riftia pachyptila'', commonly known as the giant tube worm and less commonly known as the Giant beardworm, is a marine invertebrate in the phylum Annelida (formerly grouped in phylum Pogonophora and Vestimentifera) related to tube worms ...
, this answer comes in the form of bacteria. These bacteria are capable of chemosynthesis and live inside the giant tube worm, which lives on hydrothermal vents. These vents spew forth very large amounts of chemicals, which these bacteria can transform into energy. These bacteria can also grow free of a host and create mats of bacteria on the sea floor around hydrothermal vents, where they serve as food for other creatures. Bacteria are a key energy source in the food chain. This source of energy creates large populations in areas around hydrothermal vents, which provides scientists with an easy stop for research. Organisms can also use chemosynthesis to attract prey or to attract a mate.Chemosynthesis
/ref>


Deep-sea gigantism

The term ''
deep-sea gigantism 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. Proposed explanations for thi ...
'' describes an effect that living at such depths has on some creatures' sizes, compared to the size of relatives that live in different environments. These creatures are generally many times bigger than their counterparts. The
giant isopod A giant isopod is any of the almost 20 species of large isopods, crustaceans distantly related to shrimp and crabs, which are decapods, in the genus ''Bathynomus''. They are abundant in the cold, deep waters of the Atlantic, Pacific, and Indian ...
(related to the common
pill bug Armadillidiidae is a family of woodlice, a terrestrial crustacean group in the order Isopoda. Unlike members of some other woodlice families, members of this family can roll into a ball, an ability they share with the outwardly similar but unre ...
) exemplifies this. To date, scientists have only been able to explain deep-sea gigantism in the case of the
giant tube worm ''Riftia pachyptila'', commonly known as the giant tube worm and less commonly known as the Giant beardworm, is a marine invertebrate in the phylum Annelida (formerly grouped in phylum Pogonophora and Vestimentifera) related to tube worms ...
. Scientists believe these creatures are much larger than shallower-water tube worms because they live on hydrothermal vents that expel huge amounts of resources. They believe that, since the creatures don't have to expend energy regulating body temperature and have a smaller need for activity, they can allocate more resources to bodily processes. There are also cases of deep-sea creatures being abnormally small, such as the lantern shark, which fits in an adult
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
's mouth.Video: 12ft Crabs, Walking Fish and Mini Sharks: Deep Sea Creatures - Science - WeShow (US Edition)
/ref>


Deep sea research

Humans have explored less than 4% of the ocean floor, and dozens of new species of deep sea creatures are discovered with every dive. The submarine
DSV Alvin ''Alvin'' (DSV-2) is a crewed deep-ocean research submersible owned by the United States Navy and operated by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts. The vehicle was built by General Mills' Electronics Grou ...
—owned by the US Navy and operated by the
Woods Hole Oceanographic Institution The Woods Hole Oceanographic Institution (WHOI, acronym pronounced ) is a private, nonprofit research and higher education facility dedicated to the study of marine science and engineering. Established in 1930 in Woods Hole, Massachusetts, i ...
(WHOI) in
Woods Hole, Massachusetts Woods Hole is a census-designated place in the town of Falmouth in Barnstable County, Massachusetts, United States. It lies at the extreme southwest corner of Cape Cod, near Martha's Vineyard and the Elizabeth Islands. The population was 781 ...
—exemplifies the type of craft used to explore deep water. This 16 ton submarine can withstand extreme pressure and is easily manoeuvrable despite its weight and size. The extreme difference in pressure between the sea floor and the surface makes the creature's survival on the surface near impossible; this makes in-depth research difficult because most useful information can only be found while the creatures are alive. Recent developments have allowed scientists to look at these creatures more closely, and for a longer time. Marine biologist Jeffery Drazen has explored a solution: a pressurized fish trap. This captures a deep-water creature, and adjusts its internal pressure slowly to surface level as the creature is brought to the surface, in the hope that the creature can adjust.New Trap May Take Deep-Sea Fish Safely Out of the Dark
/ref> Another scientific team, from the Université Pierre-et-Marie-Curie, has developed a capture device known as the PERISCOP, which maintains water pressure as it surfaces, thus keeping the samples in a pressurized environment during the ascent. This permits close study on the surface without any pressure disturbances affecting the sample.


See also

* Abyss Box *
Deep sea fish Deep-sea fish are fish that live in the darkness below the sunlit surface waters, that is below the epipelagic or photic zone of the sea. The lanternfish is, by far, the most common deep-sea fish. Other deep sea fishes include the flashlight f ...


References


External links


Deep Ocean Diversity Slideshow - Smithsonian Ocean Portal


- Details about specific creatures
Monterey Bay Aquarium: Online Field Guide
- Details about specific creatures
The Bioluminescence Web Page
- Good resource on bioluminescence

- Good resource on chemosynthesis
Undersea Wonders
- slideshow by ''
Life magazine ''Life'' was an American magazine published weekly from 1883 to 1972, as an intermittent "special" until 1978, and as a monthly from 1978 until 2000. During its golden age from 1936 to 1972, ''Life'' was a wide-ranging weekly general-interest ma ...
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