time difference of the onset of individual stages may be quite great. For 

 example, in the zone of the Antarctic convergence, the breeding of 

 Calanoides acutus occurs in November, of Rhincalanus g igas --in December, 

 while in the southern latitudes they occur in February and late March, 

 respectively. As a result, as we move along a meridian, we can observe 

 sequential changes in the age and space structure of the populations and 

 their abundance, analogous to their changes with time. 



The duration of the cycle differs for different species. Populations 

 of C^. acutus and C. propinquus follow a single generation almost every- 

 where; R_. gigas in the southern latitudes, with the short vegetation 

 season, does not succeed in completing its development in a single summer, 

 and it is extended over two years (Voronina, 1970). The Subantarctic 

 C. similis and C^. t onsus , apparently, are bicyclic. The specific differ- 

 ences in the development of copepoda primarily concern the time of the 

 spring ascent to the surface and breeding, as well as certain details 

 of the vertical distribution: depth inhabited by the wintering group, 

 absence or presence of daily migrations and their scale. 



Another important group of the pelagic population is the euphausiids. 

 The cycle of the most numerous species of this group, Eupheusia superba , 

 living south of the Antarctic convergence, has been most fully studied. 

 This crustacean, apparently, can breed in any region of the Antarctic 

 where spawning accumulations are formed, even around South Georgia Island 

 (Mackintosh, 1972; Makarov, 1972). The eggs are spawned in the upper 

 layers, then gradually submerge to great depth, as much as 2000-3000 m 

 (Fraser, 1936; Bargmann, 1945; Marr, 1962). During the sinking their 

 cleavage proceeds. As a result the deeper the eggs, the more advanced is their 

 development. The emerging nauplii begin active ascent during which 

 development continues. The larvae usually reach the surface water in the 

 first calyptopis stage. Only here do they begin active feeding. The 

 morphogenesis of £. superba is Mery variable (Fraser, 1936). Five different 

 paths of ontogene?is of the crustaceans have been described. The path 

 followed by development is apparently determined by the environmental con- 

 ditions (Makarov, 1974). 



In the surface water the larvae perform vertical migrations, the 

 amplitudes of which decrease with increasing age (Marr, 1962). However, 

 Simultaneously with this, the entire population tends to rise and is 

 concentrated in the upper 25 or 50 meters of water (Makarov, 1974). The 

 seasonal submergence into the deep water does not occur for this species. 

 The biologic sense of this cycle is obvious: The submergence of the eggs 

 and early larvae below the layer where they can be eaten by mature 

 euphausiids helps to preserve the population (Marr, 1962; Pavlov, 1969). 

 During the first year of life, the crustaceans complete their larval phase 

 of development; ;during the second year the juveniles feed and grow; 

 during the third year, the crustaceans mature and breed. In case of 

 unfavorable conditions, the cycle can extend to four years; this is 

 characteristic of crustaceans in the most southern Antarctic regions 

 (Makarov, 1972). 



Varying their location in the great range of depths, E_. superba is 

 subject to the influence of various hydrologic factors which, to a 



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