significant extent, determine the character of its distribution in 

 various developmental stages. The early larval stages of this species, 

 in contrast to the mature stages, occur in a rather limited water area, 

 including the East Wind Drift and the Weddell Sea circulation. No other 

 of the numerous species of the Antarctic have such distribution. All 

 other biologic boundaries in the pelagic zone coincide with the zones of 

 physical boundaries or are parallel to them. The picture of the Quantita- 

 tive distribution of £. superba , however, shows clear asymmetry and 

 brings up the question: What prevents the development of the larvae 

 over the broad aquatorium of the West Wind Drift in the Indian and Pacific 

 Ocean sectors, the ecologic conditions in which are practically the same 

 as those in the Atlantic? At the present time, this factor has but one 

 explanation. Obviously, the depth of submergence of the eggs and, con- 

 sequently, the distances which the larvae must travel as they rise to 

 the phytoplankton-rich waters, are different in different regions and 

 are inversely dependent upon the density of the water. In the shelf 

 zone, filled with cold water, submergence occurs more slowly, and even 

 if the eggs fall to the bottom, the larvae emerge in lesser depths and 

 come to the surface in earlier stages than in the oceanic zone (Marr, 

 1962). We can assume that there is a depth limit which the nonfeeding 

 larvae can travel on their return path upward, and that individuals which 

 descend to greater depths die without reaching the layer of photosynthesis 

 (Voronina, 1974). 



Obviously, the vertical structure of the water has a very significant 

 influence on the depth of submergence of the eggs; in particular, the 

 transition from the deep water mass to the denser bottom water should be 

 accompanied by a slowing or complete stoppage of movement, as is observed 

 in the sinking diatoms (Wood, Walsh, 1968). A comparison of the topography 

 of the upper boundary of the bottom water mass and the quantitative dis- 

 tribution of the calyptopes of E^. superba has yielded interesting results. 

 The Antarctic bottom water mass is formed as a result of cooling and 

 freezing of shelf water with its subsequent mixing with the deep water and 

 sliding downward along the slope (Mosby, 1934). therefore, the depth 

 of its upper boundary increases rapidly from the continent to the north. 

 Only in the Weddell Sea is there a dome-shaped elevation of this water, 

 caused by the cyclonic circulation (Klepikov, 1963). It has been found 

 that the location of the calyptopes practically coincides with the zone 

 where the denser water lies at a comparatively shallow depth--around 

 1800 m. This depth corresponds approximately to the maximum depth of 

 winter sinking of the interzonal copepoda and, probably, is close to the 

 maximum distance which many interzonal organisms can travel in their 

 seasonal vertical migrations. This gives us reason to believe that the 

 breeding of E^. superba can be truly successful only in regions where the 

 upper boundary of the bottom water mass is located relatively high. In 

 this area there are two large circulations (the East Wind Drift and 

 the Weddell Sea circulation), holding most of the rising crustaceans 

 within their boundaries. Therefore, the maximum population of all stages 

 is found in these waters, and only a portion of the population is carried 

 out beyond them. The process of gradual expansion of the habitat as 

 the generation develops has been clearly traced (Fig. 16) in larvae 

 living in the surface layer: The boundaries of their distribution shift 

 to the east from month to month (Marr, 1962). 



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