Euphausia crystallorophias
Encyclopedia
Euphausia crystallorophias is a species
of krill
, sometimes called ice krill, crystal krill, or Antarctic coastal krill. It lives in the coastal waters around Antarctica, further south than any other species of krill. The specimens for the species' original description were collected through holes cut in the ice by Robert Falcon Scott's
Discovery Expedition
, several thousand having been donated by Thomas Vere Hodgson
.
, reaching a length of 23–35 mm (0.905511811023622–1.4 ); they can be distinguished from young E. superba by the large size of the eyes, and by the long, sharply-pointed rostrum
.
at latitudes above 74° south
. It is usually found at depths of up to 350–600 m (1,148.3–1,968.5 ), but has occasionally been found as deep as 4000 metres (13,123.4 ft).
, diatom
s, detritus
and other microorganisms, including the algae
that form on the underside of sea ice
, and is in turn an important food source for fish
, whale
s and penguin
s, especially minke whale
s, Weddell seals
, Adelie penguins, and the Antarctic silverfish
. This makes it arguably the most important link in the coastal Antarctic food chain
between the primary producers
and the macrofauna. Unlike most other krill species, the eggs
of E. crystallorophias are neutrally buoyant
, meaning that the eggs do not sink, and the hatchling larva
e do not have to swim back to the more productive, shallower waters; however, since this means both life stages inhabit the same depths, it is not known how the larvae avoid being eaten by the adults.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, sometimes called ice krill, crystal krill, or Antarctic coastal krill. It lives in the coastal waters around Antarctica, further south than any other species of krill. The specimens for the species' original description were collected through holes cut in the ice by Robert Falcon Scott's
Robert Falcon Scott
Captain Robert Falcon Scott, CVO was a Royal Navy officer and explorer who led two expeditions to the Antarctic regions: the Discovery Expedition, 1901–04, and the ill-fated Terra Nova Expedition, 1910–13...
Discovery Expedition
Discovery Expedition
The British National Antarctic Expedition, 1901–04, generally known as the Discovery Expedition, was the first official British exploration of the Antarctic regions since James Clark Ross's voyage sixty years earlier...
, several thousand having been donated by Thomas Vere Hodgson
Thomas Vere Hodgson
Thomas Vere Hodgson was a biologist aboard the H.M.S. Discovery during the Discovery Expedition of 1901–1904, known by the nickname Muggins. He pursued his interest in marine biology initially in his spare time, but eventually found work at the Marine Biological Station in Plymouth...
.
Description
Adults of Euphausia crystallorophias are smaller than those of Euphausia superbaAntarctic krill
Antarctic krill, Euphausia superba, is a species of krill found in the Antarctic waters of the Southern Ocean. It is a shrimp-like crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 individual animals per cubic metre...
, reaching a length of 23–35 mm (0.905511811023622–1.4 ); they can be distinguished from young E. superba by the large size of the eyes, and by the long, sharply-pointed rostrum
Rostrum (anatomy)
The term rostrum is used for a number of unrelated structures in different groups of animals:*In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes....
.
Distribution
E. crystallorophias is found around the coasts of Antarctica, replacing the more oceanic Euphausia superbaAntarctic krill
Antarctic krill, Euphausia superba, is a species of krill found in the Antarctic waters of the Southern Ocean. It is a shrimp-like crustacean that lives in large schools, called swarms, sometimes reaching densities of 10,000–30,000 individual animals per cubic metre...
at latitudes above 74° south
74th parallel south
The 74th parallel south is a circle of latitude that is 74 degrees south of the Earth's equatorial plane in the Antarctic. The parallel passes through the Southern Ocean and Antarctica....
. It is usually found at depths of up to 350–600 m (1,148.3–1,968.5 ), but has occasionally been found as deep as 4000 metres (13,123.4 ft).
Ecology
E. crystallorophias feeds on bacteriaBacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s, detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
and other microorganisms, including the algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
that form on the underside of sea ice
Sea ice
Sea ice is largely formed from seawater that freezes. Because the oceans consist of saltwater, this occurs below the freezing point of pure water, at about -1.8 °C ....
, and is in turn an important food source for fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
, whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s and penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...
s, especially minke whale
Minke Whale
Minke whale , or lesser rorqual, is a name given to two species of marine mammal belonging to a clade within the suborder of baleen whales. The minke whale was given its official designation by Lacepède in 1804, who described a dwarf form of Balænoptera acuto-rostrata...
s, Weddell seals
Weddell Seal
The Weddell seal , is a relatively large and abundant true seal with a circumpolar distribution surrounding Antarctica. Weddell seals have the most southerly distribution of any mammal, with a habitat that extends as far south as McMurdo Sound...
, Adelie penguins, and the Antarctic silverfish
Antarctic silverfish
The Antarctic Silverfish, Pleuragramma antarcticum is a member of the suborder Notothenioidei of the Perciform fishes.Pleuragramma antarcticum is a keystone species in the ecosystem of the Southern Ocean....
. This makes it arguably the most important link in the coastal Antarctic food chain
Food chain
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
between the primary producers
Primary producers
Primary producers are those organisms in an ecosystem that produce biomass from inorganic compounds . In almost all cases these are photosynthetically active organisms...
and the macrofauna. Unlike most other krill species, the eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
of E. crystallorophias are neutrally buoyant
Neutral buoyancy
Neutral buoyancy is a condition in which a physical body's mass equals the mass it displaces in a surrounding medium. This offsets the force of gravity that would otherwise cause the object to sink...
, meaning that the eggs do not sink, and the hatchling larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e do not have to swim back to the more productive, shallower waters; however, since this means both life stages inhabit the same depths, it is not known how the larvae avoid being eaten by the adults.