SYSTEMATIC ACCOUNT 



The copepods were stained with methyl blue 

 in lactic acid and dissected in lactic acid. All il- 

 lustrations were made with a camera lucida. 

 The total length was measured from the tip of 

 the forehead to the ends of the caudal rami 

 along a sagittal plane. The uroaome was meas- 

 ured from the anterior margin of the genital 

 segment to the ends of the caudal rami. These 

 measurements excluded the telescoped portions 

 of the segments. The proportional lengths of 

 the urosomal segments, however, included the 

 telescoped portions. 



The anatomical terms used in the de.scrip- 

 tions below are defined as follows: Cephalo- 

 some — the anterior portion of the body includ- 

 ing the first anatomically thoracic segment 

 bearing the maxillipeds. Metasome — the tagma 

 composed of those thoracic segments normally 

 bearing swimming legs; that is, the second to 

 sixth anatomically thoracic segments. Prosome 

 — the cephalosome and metasome, thus, the 

 portion of the body anterior to the major ar- 

 ticulation. Urosome — the portion of the body 

 posterior to the articulation. In conformity 

 with the prevailing convention, the perianal 

 ring is counted as the last segment. The termi- 

 nal urosomal structures may be fused into the 

 so-called caudal furca, a complex composed of 

 the perianal ring and the caudal rami, and 

 sometimes an additional urosomal segment. 



FAMILY CALANIDAE 



Calanus finmarchicus s.l. Jashnov, 1955 

 (Plate 1, figs. 1-4) 

 Occurrence 



Calanus glacialis 



Sta. 5. 3 adult females, 3.45 to 3.84 



mm. 

 Sta. 7. 7 adult females, 3.55 to 3.84 



mm. 

 Sta. 9. 14 adult females, 3.55 to 3.79 



mm.; 1 adult male, 3.10 mm. 

 Sta. 13. 19 adult females, 3.69 to 4.30 



mm. ; 2 adult males, 3.63 to 



3.66 mm. 

 Sta. 15. 13 adult females, 3.40 to 3.84 



mm. ; 7 adult fnales, 3.20 to 3.70 



mm. 



Sta. 16. 1 adult female, 3.40 mm. 

 Calanus pacific us 



Sta. 13. 6 adult females, 2.80 to 3.00 



mm. 

 Sta. 15. 18 adult females, 2.73 to 3.01 



mm. ; 3 adult males, 2.67 to 2. So 



mm. 

 Sta. 16. 18 adult females, 2.62 to 2.97 



mm. ; 8 adult males, 2.64 to 



2.87 mm. 



Rema7-ks 



C. finmarchicus s. 1. has been extensively 

 studied by Ja.shnov (1955, 1957a, 1957b, 1958, 

 1961), Brodsky (1948, 1950, 1959, 1962, 1965), 

 and Grainger (1961). The specimens in the 

 present collections can be divided into two size 

 groups. The large form is identified with C. 

 filacittlis Jashnov, 1955, and the small form is 

 probably referable to C. ])acific}(s Brodsky, 

 1948. 



C. glacialis is an arctic species, widely dis- 

 tributed in the polar basin and marginal seas 

 (Jashnov, 1955; Grainger, 1961). This species 

 has also been reported from the Sea of Okhotsk 

 by Ponomareva (1961) but has not been pre- 

 viously recorded from the open Pacific Ocean. 



The female of C. glacialis has a total length 

 of 3.40 to 4.30 mm. The proportional lengths 

 of the prosome and the urosome are about 3.5- 

 3.7:1. The genital segment is wider than long 

 (53:47), and the caudal ramus is 1.4 times 

 longer than wide (fig. 1). The inner margin of 

 the coxa of the fifth leg has a conspicuous con- 

 cavity and 17 to 29 teeth (fig. 2). The third 

 endopodal segment of the fifth leg has 5 or 6 

 setae. 



The total length of female C. pacificus varies 

 from 2.62 to 3.01 mm. The proportional lengths 

 of the prosome and the urosome are about 3.28- 

 3.47:1. The genital segment is slightly longer 

 than wide (51:49), and the caudal ramus 1.6 

 times as long as wide (fig. 3). The coxa of the 

 fifth leg has a conspicuous concavity and 24 

 to 36 teeth along the inner margin (fig. 4). The 

 distal segment of the endopod of the fifth leg 

 has 5 or 6 setae as does that of C. glacialis. 



The males of the two forms are also readily 

 distinguished from each other by size. Males 

 of C. glacialis are 3.10 to 3.70 mm., those of C. 

 pacificus 2.64 to 2.87 mm. 



530 



U.S. FISH AND WILDLIFE SERVICE 



