367 



Newfoundland; in the eastern part of the ocean it is not found south of 

 Iceland and Nordkapp. In the Pacific Ocean it is numerous in the much 

 colder water regions of the Bering and Okhotsk seas, occupied by the 

 "arctic" plankton complex. In the cold season of the year it is found in 

 small numbers on the oceanic side of the North Kuril Islands and in the 

 eastern coastal regions of Kamchatka. The crustaceans mainly concen- 

 trate in the upper 100 m layer but individuals are found in deeper waters 

 also, up to 500 or even up to 1,000 m. 



Dunbar (1946, 1957) presumes that the life cycle of P. libellula 

 covers two years (the Canadian Arctic). Reproduction takes place in the 

 autumn and winter of the second year of life and the crustaceans die 

 thereafter; however, some of the crustaceans may commence reproduc- 

 tion at the end of the first year of life. 



5. Parathemisto (Euthemisto) gaudichaudi (Guerin, 1825) (Figs. 155, 



156) 



Guerin, 1825: 744 (Themisto); Bovallius, 1889: 299; Barnard, 

 1930: 420; 1932: 280; Stephensen, 1933: 63; 1944: 10; 1947: 76 

 (Themisto); Pirlot, 1939: 39; Hurley, 1955: 161; Bowman, 1960: 

 379; Kane, 1963: 35; Sheader and Evans, 1974: 9\5. —gracilipes, 

 (?) obliva Norman, 1869: 287 (Hyperia). — gracilipes Stephensen, 

 1924: 97 (Themisto). — compressa Stephensen, 1924: 103 (Themisto); 

 Chevreux, 1935: 191 (Euthemisto). — bispinosa Chevreux, 1935: 

 191 (Euthemisto). — antarctica Ealey and Chittleborough, 1956: 22 

 (Euthemisto). 



A highly variable species. Length of sexually mature specimens 

 ranges from 4 to 28 mm. 



Somites VI and VII of the pereon and somites I and II of the pleon 

 bear dorsal denticles developed to a various degree. In females and young 

 males the flagellum of antennae I is conical, with a curved and narrow 

 distal part not divided into segments. In sexually mature males the prox- 

 imal segment of the flagellum is oval-conical and twice the length of the 

 peduncle; the remaining 12-15 segments are thin, virgate. Antennae II 

 are thin and much longer than antennae I; as males mature the flagellum 

 of antennae II becomes segmented, elongates, and in sexually mature 

 specimens consists of 15-20 segments; in females the flagellum is much 

 shorter and not divided into segments. 



The structure of the mouthparts does not differ significandy from 

 other species of the genus. Maxillae I have a small, poorly developed 

 inner lobe. 

 300 The 5th segment of pereopods I is elongated-oval, the 6th conical 



and slightly curved; the distal part of the 6th segment is finely denticulate; 

 the strong curved claw is half the length of the 6th segment and the 



