24 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



19. Ceratium longiro strum Gourret 

 Figures IIT-V, chart 14, appendix table 18 



Total lengtii, 644 (570-730) microns; diameter, 19 

 (15-27) microns; ep/hyp ratio, 1.36 (1.19-1.50). Jorgen- 

 sen (1920) gave the ep/hyp ratio as 1.38 (1.26-1.45). 

 Thus, there is close agreement between the world mate- 

 rial of the Carnegie and the Mediterranean material of 

 Jorgensen. 



Ceratium longirostrum is a rare, intolerant tropi- 

 cal species with a distribution similar to that of C. in- 

 f latum (see chart 14). In the Carnegie collection it was 

 found at sixteen stations — two in the Atlantic and four- 

 teen in the Pacific. There were twenty-six records of 

 occurrence — twenty-one rare and five occasional. 

 Eighteen records were from net samples and eight were 

 from pump samples. 



The surface temperatures at the stations where it 

 occurred, varied from 22.°3 to 29.°3 C, except at one 

 station (station 2) in the North Atlantic Drift where the 

 temperature was 20f 5 C. The environmental conditions 

 in situ were: temperature, 21.°6 to 28.°5 C; salinity, 34.4 

 to 36.6 per mille; pH, 8.14 to 8.37; phosphate, 5 to 36mg 

 P04/m3. 



Not only is C. longirostrum found in warm water 

 remote from land, but it is often in water poor in nutri- 

 ents. Fourteen of the twenty-six records of occurrence 

 were in water containing less than 10 mg P04/m3. 



Nielsen (1934) listed C. longirostrum as a surface 

 species. In the Carnepie collection there were insuffi- 

 cient records to draw any conclusions in this regard. It 

 was found least often at 50 meters, but more frequently 

 at 100 meters than at the surface (table 15). 



Table 15. Records of occurrence of C. longirostrum 

 at three levels 



A=Number of records B=Per cent of total number of 

 samples collected at that depth. 



20. Ceratium falcatum (Kofoid) Jorgensen 

 Figures IIW-AA, chart 15, appendix table 19 



Total length, 513 (350-750) microns; diameter, 23 

 (15-35) microns; ep/hyp ratio, 1.38 (1.00-0.72). Jorgen- 

 sen (1920) gave the ep/hyp ratios for C. falcatum as 1.56 

 (1.38-1.70) and for C. falcatiforme . 1.13 to 1.20. The 

 Carnegie range thus includes both of these. It was im- 

 possible to separate in the Carnegie material a small 

 form answering to C. falcatiforme Jorgensen. Jorgensen 

 stated that the length of this form was about 280 microns 

 which is smaller than any Carnegie specimen measured. 

 Many specimens were found, however, which had the 

 shape of the species in question, although larger than 

 this. These inter graded into the typical C. falcatum (figs. 

 IIW-AA). It is probable that C. falcatiforme is simply 

 an extreme of the species C. falcatum. Nielsen (1934) 

 considered it a well-defined species, but presented no 



measurements, ratios, or other evidence which might 

 indicate that it is distinct in the Pacific. He simply 

 stated that it is "small." 



Ceratium falcatum is a rare, intolerant tropical 

 species with a distribution similar to that of C. inflatxmi 

 and C. longirostrum (see chart 15). In the Carnegie 

 collection it was found at thirty stations- -one in the At- 

 lantic and twenty-nine in the Pacific. There were forty- 

 seven records of occurrence--forty-slx rape and one 

 occasional. Thirty-four records were from net sam- 

 ples and thirteen were from pump samples. 



The surface temperatures at the stations where it 

 occurred, varied from 19.°0 to 28.°4 C. The environ- 

 mental conditions in situ were: temperature, 14.°2 to 

 28.°5 C; salinity, 34.5 to 36.4 per mille; pH, 7.86 to 8.39; 

 phosphate, 4 to 198 mg P04/m3. 



Although this species was found mostly in oiigotroph- 

 ic water, this was not so evident as in the case of C. in- 

 flatum and C. longirostrum. Only ten of the forty-seven 

 records were in water containing less than 10 mg 

 P04/m3. 



Nielsen (1934) listed C. falr.ahim and C. falcatiforme 

 as surface species. This is borne out by the Carnegie 

 data (see table 16). 



Table 16. 



Records of occurrence of C. falcatum 

 at three levels 



Rare 

 Occasional 



Total 



26 

 1 



5.7 

 0.3 



10 

 



2.8 



10 

 



3.9 



27 6.0 



10 2.8 



10 3.9 



A=Number of records. B=Per cent of total number of 

 samples collected at that depth. 



21. Ceratiimi extensum (Gourret) Cleve 

 Figures IIBB-DD, chart 16, appendix table 20 



This species includes C. strictum (Okamura and 

 Nishikawa) Kofoid, which is characterized by the pres- 

 ence of a well-formed right antapical horn. Since the 

 presence of this horn is not a reliable character, and 

 since it is the only one separating C. strictum from C. 

 extensum . it is no longer considered a separate species 

 (see Jorgensen, 1920; Peters, 1934; and Nielsen, 1934). 



The species is a widespread very tolerant tropical 

 form. In the Carnegie collection it occurred at 104 sta- 

 tions--14 in the Atlantic and 90 in the Pacific. These 

 were distributed in the various regions as follows: 3 in 

 the cold North AUantic (in the North Atlantic Drift), 11 

 in the warm Atlantic, 1 in the cold North Pacific (off 

 California), 79 in the warm Pacific, and 10 in the south- 

 east Pacific. There were 234 records of occurrence — 

 136 rare, 81 occasional, and 17 common. Of the total 

 number, 144 were from net samples and 90 were from 

 pump samples. 



The surface temperatures at the stations where it 

 occurred, varied from 12.°4 to 29.°4 C. In the northeast- 

 ern Pacific and in the southeastern Pacific it extended 

 into water with surface temperatures of 16.°4 and 14.°97 

 respectively. In the North Atlantic Drift it extended close 



