and summer generations of Copepoda. The temperature plasticity of the 

 eggs of the Copepoda is tremendous (Corkett, McLaren, 1970), which, in 

 addition to the relative eurybiontity of mature individuals, makes the 

 disappearance of any species during a single annual cycle in any actual 

 natural situation impossible. 



The regulatory mechanisms guaranteeing the maximum enrichment of the 

 population during the short period of abundant food also include the 

 seasonal change in the relationship of the sexes. In the winter, females 

 predominate among the sexually mature Copepoda, the fraction of males 

 falling possibly as low as a few thousandths of one percent. The number of 

 males increases as the mating season approaches, at which time they rapidly 

 metamorphize from the fourth stage. Another reserve for optimization of 

 numbers lies in the variability of the number of eggs (McLaren, 1966; 

 Corkett, McLaren, 1970). It is manifested as seasonal variation of the 

 number of eggs in the laying and, depending on the number and size of 

 layings, on the current and previous degree of nutrition of the crustaceans. 

 A decrease in fertility due to a shortage of food for the Copepoda is thus 

 reversible. If the deficiency lasts longer, the fertility is decreased 

 for a long period of time, thus decreasing the nonselective elimination. 

 Selection by change of the fertility norm touches not only upon the phase 

 of egg production, but all of ontogenesis. If the population density of 

 C yclops is too high, the number of females laying fertilized eggs decreases, 

 while the period of postembryonal development increases (A. L. Zelickman, 

 1946; A. L. Zelickman, Heinrich, 1959). The lower the population density 

 (greater the supply of food), the more closely spaced the emergence of 

 the nauplii and the higher their survival rate. This is possibly one means 

 by which the minimal wintering number of Copepoda after a year of low 

 productivity provides a tremendous population peak during the next spring 

 cycle (Zelickman, 1960b; Zelickman, Kamshilov, 1960). It cannot be 

 excluded that when population density is low, exocrine regulation of the 

 numbers is eliminated. 



However, for benthic and interzonal species of Copepoda in the Arctic 

 community, other adaptations are characteristic, similar to those of the 

 deep-sea pelagic species, the conditions of existence of which are more 

 stable (Matthews, 1964; Vinogradov, 1968). It is characteristic for them 

 that there are no sharp fluctuations in number ( Chiridius armatus , 

 Bradyidius bradyi , Aetideus a rmatus , X anthocalanus m inor , etc.); the 

 number of eggs (falling to the bottom") is less than that of the epipelagic 

 species; the number of layings per year is less; the high amount of vitellus 

 in the eggs, and, correspondingly, the lecithotrophy of the nauplii; a 

 decrease in the number of nauplial stages; year-round fertilization of 

 females; longer duration of the fifth copepodite stage. In the community, 

 these species "collect the trash," and the period of their relative abun- 

 dance coincides with the phase of summer decrease of zooplankton in the 

 upper layer. The temperature regulates the sequence of breeding of the 

 benthic species and allows them to be spread in terms of times of the 

 beginning of breeding, providing their progeny with relative regularity of 

 food supply. In the interzonal dominant species in the high Arctic 

 waters (C. glacial is , £. hyperboreus , Pareuchaeta spp., Metridia longa ), 

 adaptations are in part similar to those mentioned above; the copepodites 



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