Krill, a marine species with a wide distribution and large population, are an important food for many economic fish and baleen whales, and are also the object of fishing in fisheries. Antarctic krill is rich in resources, with an estimated number of hundreds of millions of tons in the Southern Ocean. Known as the "food bank of the world's future", the current annual output is more than 500,000 tons. The largest production in China is the Pacific krill in the Yellow Sea. Krill have obvious clumping and are the main zooplankton that forms a sound scattering layer, and has received great attention in the study of marine hydroacoustic physics.
Organisms with the highest protein content - krill (linxia) (Euphausia) invertebrates, arthropod phylum, crustaceans, krill order, krill family common name. There are about 80 species worldwide. It is shaped like a small shrimp, 1 to 2 cm long, and the largest species is about 5 cm long. The body is transparent, the cephalothorax heals with the entire cephalothorax, but does not extend to the ventral surface, so no gill cavity is formed; the gills are bare and directly immersed in the water. The abdomen has 6 segments with 1 caudal segment at the end. There are 8 pairs of thoraxes, all of which are double-branched, and each has gills at the base, which is suitable for swimming. There is no specialization of the jaw foot in the thorax, and the ventral surface of the stalk, the thorax and the base of the appendage on the abdomen have spherical light emitters that emit phosphorescence. Floating life, all seafood. It is one of the main baits for fish. Can be made with shrimp paste. Commonly found along the Yellow and East Coasts is the Pacific Krill (Euphausiapacifica). The famous Euphausia superba is found in the Antarctic oceans.
Crustaceans of the suborder Euphausiacea or Krill genus Euphausia, sometimes known in English as the E. superba. Krill live in the open ocean, 8 to 60 mm (about 1/4 to 2 inch) long, and 82 species are known. Due to its large numbers and abundance of nutrients, ecologists believe that it is a potential food source for humans, especially providing large amounts of vitamin A.
Euphausiacea is an order of real shrimp. All marine zooplankton. With bifurcated finger-like gills and luminescent apparatus, the thoracic foot does not differentiate into jaw foot and step foot. There are 85 known species worldwide, which can be divided into 2 families and 10 genera, 1 genus of deep krill, and 9 genera of krill family. More than 20 species have been reported offshore China.
Krill resemble small ten-legged shrimps and are 6 to 95 mm long. The body can be divided into cephalothorax and abdomen. Cephalothorax segments are completely covered by cephalothorax, and the lower margins of the cephalothorax are smooth or have lateral teeth. There are 7 segments of the ventral part, and some species have spines on the back of the ventral segments or a pair of flaky spines on either side of the ridge and the end of the caudal segment. There are 19 pairs of appendages, the first antennae double-branched type, the perching section is 3 segments, and the morphology of each segment varies according to the species. The second antennae have well-developed scales. The large jaw is directly connected by the incisort and molar process, and the adults have no moving pieces, but many have tentacles. The first small jaw has 2 segments of the primary limb, the outer part of the 1st segment is enlarged into an outer lobe, and the inner lobe 1 segment is smaller. The second small jaw has 2 segments of the primary limb, the inner limb is not segmented, and the outer limb is smaller, which is significantly different from the decanter order. 8 pairs of thoraxes, basically similar, double-branched, 2 segments of the original limbs, and a branched gill at the base. 5 segments of the inner limbs, the last 2 pairs or 1 pair of degenerate or total deficiency, the genus 2nd or 3rd pair of thorapods in the Nematoscelinae subfamily (Nematoscelinae) has 1 pair of inner limbs with exceptionally large deformation into skimmed limbs. The base plate of the outer limb is thick and the flagella is multi-segmented. Both the inner and outer limbs have pinnate bristles, the swimming ability is strong, and the inner limbs of the 1st and 2nd abdominal limbs of males are deformed into a handover, and their structure is different from species to species, which is one of the important bases for identifying species. The abdominal limbs are developed and double-branched.
The digestive tubes of krill are relatively simple, and the branched liver and pancreas are digestive glands. The heart is polygonal, the heart is 3 pairs, and the blood circulation is open. The excretory organ is the antennal gland. The compound eye is well developed and the stalk is short, and the compound cornea of predatory species often consists of two lobes of varying sizes. In addition to the genus Deep Krill, there are 5 to 10 light emitters. Generally above the stalk, 1 at the base of the 2nd and 7th th thoracic feet, and 1 in the center of the abdominal carapace of the 1st to 4th abdominal segment. Stylochecion has only an eye stalk , with 5 luminescents on the 7th thorax and 1st abdominal segment. The luminescence is made up of luminous cells, reflectors and crystals, all of which are connected by nerves and have different structures on the stalk of the eye. Krill emit a cold blue light.
Krill hermaphroditic, indirect development. Sperm are discharged in the sperm pod. The fertilized eggs of the freely spawning species hatch into an arthropod, which molt twice and become a late arthomeric; the egg-holding species is already a late nodal larvae when it first hatches; it molts into the ganghorax larvae and begins to ingestion, also divided into 3 stages, the 3rd stage of the thoracic larva molt is a forked larvae, which can be divided into 4 stages; and then develop into a ganglion larvae, which is basically similar to the adult, but the individual is small and sexually immature, and this stage is actually the late stage of juvenile.
The feeding habits of krill vary by age, with juveniles filtering on diatoms and organic detritus, and adults preying on copepods and other small zooplankton. Filter feeding species consist of spiny hairs on the thorax. When omnivorous species change from filtered to predatory, the filtration rate is greatly reduced. Predatory species are generally particularly developed on the 2nd or 3rd thoracic limbs. The respiration rate of a krill is usually proportional to the surface area of its body. Cold-water krill have a longer life cycle. In the Sea of Okhotsk, krill grow faster in year 1 and gradually slow down later. The growth period of krill is consistent with the spring and autumn peak of diatoms. But when the ovaries mature, growth almost stops. The amount of reproduction increases with age (body length), and after a certain age, the amount of eggs produced decreases. Development rates vary by species, such as Norwegian krill 3 to 4 days for arthropods, 7 to 9 days for trilled krill, and 25 months for female Antarctic krill to reach sexual maturity (22 months for males). Krill often flock in large numbers, and have a diurnal vertical movement habit in water bodies, rising to the surface at night and descending in the early morning.
The Southern Ocean has a cold current that surrounds the Antarctic continent, which sinks as it flows northward, while the warm currents from the Pacific, Atlantic, and Indian Oceans form an upwelling current when they encounter this sinking cold current when they go south. This upwelling current is rich in nutrients, and combined with plumbing, it makes microorganisms multiply and become an ideal place for krill to feed and roost. The life cycle of Antarctic krill is adapted to the seasons of the Southern Ocean.
The esophagus of Antarctic krill can be seen from its transparent shell that it is green, which shows that they mainly feed on phytoplankton, especially tiny diatoms (about 20 microns). Diatoms are ground up by its gastric gums and digested in the liver and pancreas. Antarctic krill can also prey on copepods, endpods, and other small zooplankton. Its esophagus is always tube, and its digestive efficiency is not too high, so its feces still have a lot of carbon.
In aquariums, it has been found that Antarctic krill will eat each other. When they are not fed in the aquarium, they shed their hull and shrink in size, which other animals do not have. This may be their adaptation to the food supply restrictions in winter.
Antarctica is rich in krill resources, krill mainly live in the Southern Ocean not far from the Antarctic continent, especially in the Weddell Sea is more dense. Interestingly, sometimes krill swarms form teams hundreds of meters long and wide, with more than 30,000 krill per cubic meter of water, which changes the color of the sea: a light brown color on the surface during the day and a fluorescent patch at night.
They mate in the spring, from October to November, and each female lays eggs several times in the summer, up to thousands of grains at a time. Once these shrimp eggs leave the mother, they sink to the bottom of the sea hundreds of meters deep, where they hatch into larvae, and after continuing to grow for a period of time, the yolk stored in the yolk sac is finally exhausted, at which point they float up to the surface of the sea to ingest the phytoplankton. They grow slowly in icy waters, and the juvenile shrimp have to go through 5 stages and molt multiple times to grow into 6 cm long adult shrimp, with a growth period of 3 to 4 years. During this time, they have been living in groups, migrating around under the ice, looking for food and hiding from predators.
Krill are all marine species, widely distributed and abundant, and are an important food for many economic fish and baleen whales, as well as fishing for fisheries. Antarctic krill is rich in resources, with an estimated number of hundreds of millions of tons in the Southern Ocean. Known as the "food bank of the world's future", the annual output is more than 500,000 tons. The largest production in China is the Pacific krill in the Yellow Sea. Krill have obvious clumping and are the main zooplankton that forms a sound scattering layer, and has received great attention in the study of marine hydroacoustic physics. In addition, the distribution of some krill is related to certain water masses and currents, which also has certain significance in oceanographic research.
Krill is extremely rich in resources, and there is no doubt that it is a potential food resource for humans. The existing problem is that countries have already fished for krill in large quantities in the Antarctic ocean, and if the krill fishing industry continues to expand, it is bound to endanger the survival of Antarctic cetaceans, and they will die not from whaling forks, but from starvation. Overfishing would have disastrous consequences for Antarctica's fragile ecosystems, where almost all animals depend directly or indirectly on krill for their survival. Further exploitation of krill is inevitable, but their catch should be kept within the maximum sustainable catch to protect the ecological balance of Antarctica.