Title: Sexual Differentiation in the Antarctic Krill Euphausia Superba Dana (Crustacea: Euphausiacea)
Abstract: Young krill (late larvae, juveniles, and subadults) were sampled from the region of Pridz Bay, Antarctica, in January-February 1985, and were observed alive to determine body size, molt stage, and external sexual features. The gonads were subsequently fixed and studied histologically. The undifferentiated gonad contains primary and secondary gonia. Secondary gonia first differentiated into oocytes in young krill at a body length of 24 mm. Maturation of the ovary or testis and development of secondary sexual characters (petasmata and ampullae in males; thelycum in females) occurred during a phase defined as subadult. The ovary became fully mature and spawning occurred in young females at a body size of 33 mm. The smallest mature male was 36 mm long. By differentiating the gonad before the external sexual features, Euphausia superba follows the same developmental pathway as peracarid crustaceans. However, krill are adapted to the Antarctic environment in being able to regress in sexual maturity and in size under extreme winter conditions. The possibility of a sexual regression to an immature or even an undifferentiated state is discussed.
Publication Year: 1987
Publication Date: 1987-07-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 22
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