Spinocalanus elongatus — The depth range of S. 

 elongatus was 300-2,500 m. Adults were found from 

 350 to 2.500 m, juveniles from 300 to 2,000 m. The 

 highest average concentrations occurred between 

 1,500 and 2,500 m, with uniformly low numbers up 

 to 300 m (Table 2). 



Brodsky (1957) reported that this species was 

 found in low numbers from 25 to 200 m, but that it 

 was the most numerous of all copepods between 800 

 and 3,000 m, where it comprised over lO'c of the 

 numbers of copepods. Dunbar and Harding (1968) 

 reported no S. elongatus above 175 m, greatest 

 numbers from 900 to 2,000 m, and none below 2, OCX) 

 m. 



Spinocalanus elongatus is apparently the only 

 species of Spinocalanidae limited to the Arctic. Its 

 rarity in the outflowing Arctic Water would 

 definitely reduce its opportunities to enter the 

 Atlantic. Possibly S. elongatus occurs in the North 

 Atlantic in small numbers; it could be confused 

 with the superficially similar S. brevicaudatus, 

 found in the North Atlantic but apparently not in 

 the Arctic. 



Spinocalanus polaris — The depth range of S. 

 polaris was 1,500-3,000 m. Only adults were found. 

 The highest average concentration occurred 

 between 2,000 and 2,500 m (Table 2). 



Brodsky and Nikitin (1955) reported one juvenile 

 S. polaris between 50 and 100 m and one female 

 between and 265 m, although most records place 

 the bulk of this species below 1,000 m. 

 Spinocalanus polaris is found in the North Atlan- 

 tic, including the Caribbean, below 980 m; if it does 

 not occur above 980 m, it could not be carried into 

 the Arctic. However, the few Arctic S. polaris 

 reported above 265 m provide a possibility for this 

 species to be transported out of the Arctic. 



Mimocalanua era^aus — The depth range of M. 

 crassus was 400-2,500 m, where it was found only in 

 low concentration (Table 2). Only two other records 

 of M. crassus are known: from the Caribbean Sea 

 (Park, 1970) and the Indian Ocean (Grice and 

 Hulsemann, 1967) with a vertical distribution 

 similar to that found in the Arctic. Mimocalanus 

 crassus has not yet been reported from the North 

 Atlantic, but it probably occurs there at times, 

 from where it could enter the Arctic in the Atlantic 

 Water. 



Mimocalanus aulcifrona — The depth range of M. 

 sulcifrons was 100-2,500 m. Adults were found from 

 350 to 2,500 m, juveniles from 100 to 2,500 m, all in 

 low concentration (Table 2). 



Only a few other specimens of this species have 

 been reported from the Arctic, in each case as M. 

 distinctocephalus. Hughes (1968) found only 

 juveniles, in two samples from 80 and 90 m. Other 

 records are based on sample intervals of 0-2,000 m 



(Johnson, 1963a; Dunbar and Harding, 1968) and 

 0-520 m (Minoda, 1967). Johnson, and later Dun- 

 bar and Harding, in spite of the absence of this 

 species in strictly near-surface samples, suggested 

 that it is brought into the Arctic from the Pacific. 

 However, M. distinctocephalus (= M. nudus) in 

 the North Pacific has not been reported with cer- 

 tainty above 200 m (see systematic review); 

 therefore, it probably can not enter the Arctic by 

 this route. Mimocalanus nudus has not been 

 reported from the Arctic. 



Only a few specimens of M. sulcifrons have been 

 reported from the North Atlantic, and only 

 between 2,000 and 4,000 m. Juveniles might be 

 carried out of the Arctic in low concentration in the 

 Arctic Water. If adults in the Atlantic live only 

 below 2,000 m, there would be no possibility for 

 them to enter the Arctic. 



The most abundant of the seven Arctic species were 

 Spinocalanus longicornis and S. antarcticus. The 

 other species were in about equal, low concentration. 

 None of these species have definitely been reported at 

 the Arctic surface, but most have been taken, though 

 rarely, as shallow as 25 or 50 m. The depth of highest 

 concentration of each species varies: S. longicornis 

 (100-400 m), S. antarcticus (180-400 m), M. sulcifrons 

 (200-400 m), M. crassus (400-2,500 m), S. horridus 

 (500-2,500 m), S. elongatus (900-2,500 m), and S. 

 polaris (1,500-2,500 m). All have been collected at 

 least as deep as 2,500 m. 



The distribution of these species in seas adjacent to 

 the Arctic is of great interest, although in most cases 

 the distributions are not yet well defined. Surface 

 layer copepods are transported from the Pacific into 

 the Arctic (Johnson, 1963a, b) and perhaps inter- 

 mittently in a southward surface flow, but there can 

 be no exchange of strictly deepwater components 

 because of the relatively shallow sill separating the 

 two areas at Bering Strait. 



Both S. longicornis and S. antarcticus have vertical 

 distributions in the Arctic which include relatively 

 high numbers in Arctic and Atlantic Waters, and 

 therefore there appear to be no physical barriers to 

 their movement in and out of the Arctic. However, 

 only ^S. longicornis is reported in the North Atlantic 

 and North Pacific; S\ antarcticus may yet be found 

 there since it is known from the Antarctic. 



Spinocalanus horridus has been found only rarely in 

 Arctic Water, and its movement out of the Arctic is 

 probably restricted. It is found in the North Atlantic 

 and undoubtedly enters the Arctic freely in the Atlan- 

 tic Water. 



Spinocalanus elongatus has a vertical distribution 

 similar to S. horridus; its movement out of the Arctic 

 is probably restricted. It has not been reported from 

 the North Atlantic and may be the only species of 

 Spinocalanidae endemic to the Arctic. 



Spinocalanus polaris and Mimocalanus sulcifrons 



12 



