Growth characteristics
According to the classic hypothesis based on data obtained from the British RSS Discovery, the eggs of Antarctic krill grow as follows: 0.6 mm eggs begin gastrulation (the process of egg development into embryo) when they sink to the bottom of the continental shelf or ocean area at a depth of 2000-3000 meters. When the eggs hatch, the first nauplius begins to rise to the surface of the sea with the help of its three pairs of legs. The next two larval stages, called the second nauplius and the post-nauplius, are also fed by yolk. After three weeks, the young krill will complete the ascent. Their number reaches 2 per liter at a depth of 60 meters. When they grow larger, additional larval stages, called the second and third thoracothorax and the first to sixth larvae, are characterized by the increased development of more legs, compound eyes and bristles. At about 15 mm long, Antarctic krill begin to have adult habits. They reach maturity after two to three years. Like other crustaceans, Antarctic krill must shed their shells to grow. About every 13-20 days, Antarctic krill will shed its chitinous exoskeleton. Lifespan is 6 years.
The hatching of Antarctic krill eggs takes place during the sinking process (one or two kilometers or even deeper). Specifically, after the krill spawn, its eggs begin to sink and hatch as they sink. Krill eggs sink very quickly, about 140-320 meters per day. After three to five days, they can sink to a depth of one or two kilometers, at which time the hatching is over. After hatching, the krill metamorphose and slowly move upward. When they reach the 100-meter water layer, they have become young shrimps that can directly and actively feed. The total time from sinking to rising is three or four weeks.
Reproduction method
The main spawning season for Antarctic krill is from January to March, and they spawn on the continental shelf and in the upper areas of the deep sea. For all krill orders, the male will attach sperm to the female's genital pore. To this end, the male's first ventral limbs serve as a copulation tool. Females lay 6,000-10,000 eggs at a time. These eggs are fertilized by sperm from the spermatophore attached to it as they are expelled through the genital opening.
Antarctic krill mating consists of five stages: chasing, probing, embracing, bending, and pushing. First, males (sometimes more than one at a time) chase the pregnant female. Then, a male uses his antennae (specialized structures on the first pair of ventral limbs) to probe the female. The male and female then embrace belly to belly. The spermatophore is transferred as the male bends his body around the female, forming a T-shaped pair. The transfer of the spermatophore is aided by hooks on the antennae. The bending process involves rapid rotation, which lasts about 5 seconds, which helps push the spermatophore into the female's external sperm duct. After the bending, the pair continues to swim together, with the male using his beak and antennae to push against the female's ventral surface. All adult female Antarctic krill spawn during the breeding season, and the eggs are laid regularly and released during several spawning events. Each female krill can produce up to four oocytes.
