40 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



Carnegie collection many intergradations were found 

 between these and still other variants so they have not 

 been recorded. Some of the variants are similar to 

 modifications of C. massiliense. Indeed, these two spe- 

 cies may be identical. They have been kept separate in 

 this report on the basis of the origin of the left antapical 

 horn which in C. carriense starts in a posterior direc- 

 tion before curving laterally, so at its proximal end it 

 does not form a straight line with the posterior edge of 

 the body. The demarcation was indefinite, however, with 

 numerous inter grades. 



The distribution of the species as considered here Is 

 similar to that of C. massiliense . except that it does not 

 extend as far outside the tropical regions. In the Carne- 

 gie collection in the Atlantic there is only one station 

 outside the warm Atlantic region, station 13a. In the 

 Pacific it has about the same distribution as C. massili- 

 ense in the north, but was not well represented in the 

 southeastern part of the Pacific (chart 40). Nielsen 

 (1934) found it in the Pacific from Panama to Australia, 

 and Peters (1934) found it widely distributed in the warm 

 water of the South Atlantic. 



The total number of Carnegie stations at which it was 

 found, was 111, 12 of which were in the Atlantic and 99 in 

 the Pacific. The total number of sample records for the 

 species was 281, with 138 rare, 124 occasional, and 19 

 common. The net records numbered 219; the pump rec- 

 ords, 62. 



The range of environmental conditions in which the 

 species was found was similar to that of C. massiliense . 

 though somewhat more restricted. The surface temper- 

 atures at its record stations in the Atlantic ranged from 

 21.°2 to 28.°5 C and in the Pacific from 16.°3 to 29.°5 C. 

 Of the 281 records, 98 were from water containing less 

 than 10 mg P04/m3. The complete ranges of environ- 

 mental conditions in situ were: temperature, 12.°5 to 

 29.°4 C; salinity, 29.7 to 35.9 per mille; pH, 7.82 to 8.47; 

 phosphate, 3 to 153 mg P04/m3. 



Ceratixim carriense is a surface species (Nielsen, 

 1934). In the Carnegie collection It was found with de- 

 creasing frequency with increase in depth (table 42). 



Table 42. 



Records of occurrence of C. carriense 

 at three levels 



Occur- 

 rence 



Rare 



Occasional 



Common 



Total 



Depth in meters 



B 



50 



B 



100 



58 

 51 

 13 



13.5 



13.0 



3.4 



47 

 43 



14.4 



14.2 



2.2 



33 

 30 







12.0 

 11.9 



122 29.9 96 30.8 63 23.9 



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

 samples collected at that depth. 



50. Ceratium contrarlum (Gourret) Pavlllard 

 Figures 22E, 24A-B, chart 41, appendix table 46 



This species Is rather distinctive, and fairly con- 

 stant in its body shape and origin of horns. There is one 

 variation of the species, however, which has club-shaped 

 ends on the antapical horns, var. claviceps Schroder (fig. 

 24B). In this variant the apical horn also maybe expand- 

 ed, but only gradually toward the tip. It was found rather 



frequently in both the Atlantic and Pacific. It apparently 

 does not represent a response to shade conditions, as it 

 was found frequently at the surface. 



The species as a whole is one of the most common 

 of the genus. Peters (1934) found it commonly in the 

 South Atlantic to about 33° south latitude generally and 

 to almost 40° south, south of the Cape of Good Hope. 

 Nielsen found it at all oceanic stations in the South Pa- 

 cific with surface temperatures over 19° C. In the 

 Carnegie collection it occurred at almost all the stations 

 in the warm Atlantic region, warm Pacific, and southeast 

 Pacific region as well as at one station in the cold North 

 Pacific region (chart 41). The total number of station 

 records was 138, of which 20 were in the Atlantic and 

 118 in the Pacific. The total nimiber of sample records 

 was 467, of which 167 were rare, 172 occasional, and 

 128 common. The net records numbered 298; the pump 

 records, 169. 



The distribution of the species at Carnegie stations 

 indicated a greater tolerance for lower temperatures in 

 the Pacific than in the Atlantic. In the Atlantic it did not 

 occur in the North Atlantic Drift but stopped abruptly at 

 the 20° isotherm. In the Pacific, on the other hand, it 

 occurred to surface temperatures of 16.°4 off the United 

 States, and 15° C at 40° south in the southeastern Pacific. 

 It showed no regard for the nutrient content of the water, 

 being foimd as much in oligotrophic as eutrophic water. 

 Of the 467 records of occurrence, 154 were in water con- 

 taining less than 10 mg P04/m3. The environmental 

 conditions in situ were as follows: temperature, 10.°2 

 to 29.°5 C; salinity, 30.7 to 37.1 per mille; pH, 7.76 to 

 8.47; phosphate, 2 to 178 mg P04/m3. 



Ceratium contrarlum is a surface species. Nielsen 

 (1934) always found it more common in the 50- to 0-meter 

 samples than in the deeper samples. In the Carnegie col- 

 lection it was found with decreasing frequency with in- 

 crease in depth (table 43). For example, it was found In 

 57.2 per cent of the surface samples, but only 37.4 per 

 cent of the 100-meter samples. 



Table 43. 



Records of occurrence of C. contrarlum 

 at three levels 



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

 samples collected at that depth. 



51. Ceratium trichoceros (Ehrenberg) Kofoid 

 Figure 22B, chart 42, appendix table 47 



This Is a widespread intolerant tropical species 

 characterized by widespread horns which lie parallel in 

 their distal parts. It is fairly constant in its shape, al- 

 though Nielsen (1934) has noted a tendency for an increase 

 in diameter in colder or neritic waters. 



In the Carnegie collection the species was found wide- 

 ly distributed in the warm regions, although not so com- 

 monly as such species as C. massiliense. Ceratlxim 



