36 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



The ranges of environmental conditions in situ for 

 the species at all stations were as follows: temperature, 

 13.°8 to 28.°2 C; salinity, 33.9 to 36 per mille; pH, 8.47 

 to 7.80; phosphate, 4 to 150 mg P04/m3. 



Thirty of the eighty-eight records were from water 

 containing less than 10 mg P04/m3. 



The total number of sample records for the species 

 was eighty-eight, of which eighty-five were rare and 

 three occasional. There was a large proportion of pump 

 records owing to the small size of the species (thirty- 

 nine pump records and forty-nine net records). 



Ceratium limulus apparently lives at various depths 

 but is found somewhat more frequently in the upper lev- 

 els. Bohm (1931) found it in the Adriatic as deep as 200 

 meters. Nielsen (1934) found it predominantly in the 50- 

 to 0-meter samples. In the Carnegie collection the spe- 

 cies was found with decreasing frequency with increase 

 in depth to 100 meters (table 35), although the frequency 

 at 100 meters (in percentage) was more than half that at 

 the surface. 



Table 35. 



Records of occurrence of C. 

 at three levels 



limulus 



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

 samples collected at that depth. 



43. Ceratium paradoxides Cleve 

 Figure 19B, chart 34, appendix table 39 



This is a rare Intolerant tropical species. Peters 

 (1934) found it in both oligotrophic and eutrophlc water 

 in the South Atlantic. Nielsen (1934) found it scattered 

 over the region traversed by the Dana from Panama to 

 Australia. It is never common and its distributional rec- 

 ords are discontinuous for this reason. 



In the Carnegie collection the species was found at 

 sixty-four stations- -thirteen in the Atlantic and fifty-one 

 in the Pacific. In the Atlantic the stations were confined 

 to the warm Atlantic region. In the Pacific they were 

 restricted to the warm Pacific region and the southeast 

 Pacific region (see chart 34). 



There were ninety-one records of occurrence, of 

 which eighty were rare and eleven occasional. Sixty-six 

 of these records were from net samples and twenty-five 

 were from pump samples. 



Nielsen (1934) stated that C. paradoxides is a shade 

 species, and this is corroborated by the Carnegie obser- 

 vations. In fact, its vertical distribution is most decid- 

 edly stratified. As shown in table 36, there were only 

 six records for the surface samples (representing only 

 1.6 per cent of the samples), whereas the species was 

 found in 22.8 per cent of the 100-meter samples. 



The surface temperatures at the stations where C. 

 paradoxides occurred In the Atlantic varied from 20.° 5 to 

 27.°6 C; in the Pacific from 19° to 29.°5 C. The environ- 

 mental conditions in situ were as follows: temperature, 

 12.°1 to 29.°3 C; salinity, 33.4 to 37.0 permUle; pH, 7.17 



to 8.39; phosphate, 4 to 123 mg P04/m3. It was found 

 in both eutrophlc and oligotrophic water. Thirty -four of 

 the ninety-one records were in water containing less than 

 10 mg P04/m3. 



Table 36. Records of occurrence of C. paradoxides 

 at three levels 



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

 samples collected at that depth. 



44. Ceratium platycorne Daday 

 Figures 19C-H, chart 35, appendix table 40 



This is a rare, slightly tolerant tropical species. 

 Varieties of the species have been described, but these 

 are of no particular importance. Variety cuneatxmi Jor- 

 gensen is not distinguishable from the main species. Its 

 shorter truncated antaplcal horns probably are owing to 

 autotomy or accidental breaking of the distal part of the 

 horns. It is probable that the jagged edges of these 

 horns never represent the original condition. Figure 

 19D shows a specimen with broken (truncate) right ant- 

 aplcal which is shorter than the left. The right is nor- 

 mally longer than the left. Variety lamelllccrne is some- 

 what more distinct. Nielsen (1934) found it quite distinct 

 in the Dana collections. It is, however, simply a narrow- 

 horned variant and Intergrades are not absent (fig. 19G). 



Ceratium platycorne is widespread over the tropi- 

 cal waters of the world and is sometimes displaced by 

 currents. It has been found by others in the northern 

 waters of the Atlantic (Paulsen, 1908; Lebour, 1925). In 

 the Carnegie collection it occurred off Iceland, with a 

 surface temperature of 12.°44 C. Otherwise, in the At- 

 lantic it was confined to the warm Atlantic region, with 

 surface temperatures above 20° C. In the Pacific it was 

 limited to the warm Pacific and southeast Pacific re- 

 gions, with surface temperatures ranging from 19.°27 to 

 28.°74 C. The ranges of environmental conditions in situ 

 were: temperature, 12.°4 to 27.°6 C; salinity, 34.1 to 

 37.0 per mille; pH, 7.87 to 8.39; phosphate, 4 to 152 

 mg P04/m3. 



Peters (1934) found C. platycorne widespread in 

 oligotrophic water in the South Atlantic, and Nielsen 

 (1934) found it in the entire region between Panama and 

 Australia. In the Carnegie collection it did not show any 

 preference for one type of water. Eighteen of the fifty- 

 three records of occurrence were from water containing 

 less than 10 mg P04/m3. 



The species is not common. There were onlyforty- 

 tliree stations at which It was found, of which fourteen 

 were in the Atlantic and twenty-nine in the Pacific. The 

 total number of records (fifty-three) is relatively small. 

 Of these, forty-four were rare, eight occasional, and 

 one common. There were thirty-eight net records, and 

 fifteen pump records. 



Ceratium platycorne is distinctly a shade species. 

 The records indicate this even more definitely than in 



