44 



CERATIUM m THE PACIFIC AND NORTH ATLANTIC OCEANS 



to the international rules of botanical nomenclature the 

 name for this Inclusive species must be C. arctlcum. as 

 it was used as a specific name earlier than C. longlpes 

 (see Jorgensen, 1911, pp. 84-85). The longlpes form, 

 however, is sufficiently distinct to be separated as ava- 

 riety. Variety ventricostmi Ostenf eld is a robust, heav- 

 Uy armored form, with swollen body (fig. 26E). It is 

 apparently limited to the northern Atlantic waters. In 

 the Carnegie collection it occurred only in the cold At- 

 lantic region, with the single exception of station 14, 

 where the surface temperature was 21.°2. At the other 

 record stations the temperatures were under 11° C. 



Variety arcticimi probably is more characteristic of 

 colder water than is longlpes . although not so much so 

 as the name would indicate. Variety longlpes is found 

 more frequently over a wider range than var. arcticum . 

 but the latter strays far from its northern home. Cleve 

 (1900) found it as far south as the Azores and the Straits 

 of Glbralter. In the Carnegie collection it was found as 

 far south as 20° north in the central Atlantic (station 20) 

 and at one station in the Caribbean (station 33). It was 

 never found at the surface in these warm regions, how- 

 ever, although the temperatures In situ were quite high; 

 namely, 25.°8 C at station 20 and 28.°2 C at station 33. 

 This is a curious distribution for a species of Ceratiimi. 

 Its center of abundance unquestionably is in the cold 

 waters where the temperatures are less than 10° C at 

 the surface in the summer; yet isolated specimens find 

 their way into the heart of the tropics. 



Apparently a similar situation exists in the North 

 Pacific. The main distribution of arcticum is to the 

 north in cold water ( Carnegie stations 120 to 121, sur- 

 face temperatures less than 8° C), yet a specimen was 

 foimd at station 146 between Hawaii and the United States, 

 where the surface temperature was 22.°4 C. To be sure, 

 the record was for the 100-meter sample, but even here 

 the temperature was 19.°7 C. 



Variety longlpes . on the other hand, although it oc- 

 curs abundantly over a wider range than var. arcticum . 

 is not found so far from its centers of abundance as var. 

 arcticum. 



The inclusive species was foiind at a total of thirty- 

 one stations, of which twenty-one were in the Atlantic 

 and ten in the Pacific. The total number of sample rec- 

 ords was eighty-four, with thirty-seven rare, twenty- 

 seven occasional, eleven common, and nine abundant. 

 Net samples predominated with fifty-nine records, as 

 compared with twenty-five pump sample records. 



The total ranges of environmental conditions in situ 

 V'ere: temperature, -l.°2 to 28.°2 C; salinity, 32.7 to 

 37.1 per mille; pH, 7.64 to 8.29; phosphate, 3 to 228 mg 

 P04/m3. 



No one has reported anything regarding the depth at 

 which the species normally lives since Nielsen (1934) did 

 not find the species. The Carnegie records (table 49) 

 show an Increase in frequency with increase in depth to 

 100 meters. The increase is not great, however, with 

 the species occurring in 8.1 per cent of the surface sam- 

 ples and 10.6 per cent of the 100-meter samples. Is it 

 possible that C. arcticum . which is characteristic of arc- 

 tic waters, is a shade species adapted for life under the 

 polar Ice cap where the intensity of illumination cannot 

 be great? The Carnegie data alone cannot be conclusive 

 regarding the vertical distribution of this species. Many 

 of the station records are from cold northern waters 

 where the plankton In the upper layers is comparatively 

 dense so there is much greater chance of contamination 



of the open nets dxiring hauling in. On the other hand. It 

 should be noted that the records for the species in the 

 warm oligotrophlc water of the Atlantic are predominant- 

 ly subsurface records. This occurrence may be owing to 

 the lower temperatures obtaining there rather than to the 

 preference for, or superior survival in, levels of weak 

 illumination so the species may not be a shade species 

 In the true sense of the term. 



Table 49. 



Records of occurrence of C. arcticum 

 at three levels 



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

 samples collected at that depth. 



57. Ceratium hexacanthum Gourret 

 Figures 27F-G, chart 48, appendix table 53 



This is a common, very tolerant tropical species. 

 The antapical horns tend to be extremely thin and atten- 

 uated, and to curl so that various modifications of these 

 horns occur. There seems to be no justification for cre- 

 ating varieties such as var. spiralis Kofoid, on the basis 

 of such characters as the curl of the horns. 



In the Pacific the species was confined to the warm 

 tropical waters. The surface temperatures at the Pacif- 

 ic record stations were all above 20° except at two sta- 

 tions in the southeastern Pacific (stations 57 and 62), 

 where the surface temperatures were 19.°0 and 19.°2 C. 

 In the Atlantic, on the other hand, the species is appar- 

 ently carried by the North Atlantic Drift to the British 

 Isles and as far as Iceland (see chart 48) Into water with 

 surface temperatiu-es as low as 8.°9 C. Morpholgically 

 no separation could be made between the Atlantic and 

 Pacific forms. The form carried into the cold waters of 

 the North Atlantic, however, probably is a particular sub- 

 species, at present indistinguishable from the tropical 

 form because the tropical form does not invade cold 

 water elsewhere. Peters (1934) stated that it was no- 

 ticeably absent from the South Atlantic south of about 33° 

 south. It dropped out at about this latitude at the Carne - 

 gie stations in the southeastern Pacific, and at the Dana 

 stations in the southeastern Pacific (Nielsen, 1934). 

 Thus, it kept within the 20° isotherm in the North Pacif- 

 ic, which indicates that the race of the Pacific is at least 

 physiologically different from that in the North Atlantic. 



The ranges of environmental conditions in situ for 

 the species as a whole were: temperatiure, 8.°2 to 29.°3 

 C; salinity, 30.7 to 37.1 per mille; pH, 7.17 to 8.47; 

 phosphate, 2 to 198 mg P04/m3. 



The total number of station records was 124- -28 in 

 the Atlantic and 96 in the Pacific. There were 327 rec- 

 ords of occurrence, of which 169 were rare, 129 occa- 

 sional, and 29 common. The net records numbered 267; 

 the pump records, 60. 



Nielsen (1934) classified C. hexacanthum as a shade 



