34 



CERATIUM IN THE PACIFIC AND NORTH ATLANTIC OCEANS 



represents the anterior cell of a chain, whereas f . brachv - 

 ceros represents the remaining cells in the chain. It is 

 inconsistent to name the two elements of a chain in this 

 species alone as similar differences occur in the anteri- 

 or and following cells of the other species as well. 



In the Atlantic the species is distributed over the 

 warm Atlantic region, extending to latitude 39° north, 

 but it is absent from the cold North Atlantic region. 



The distribution of C. lunula at Carnegie stations in 

 the Pacific is unique among the Ceratium species (chart 

 31). It is similar to that of C. breve but even more re- 

 stricted (see p. 27). It is definitely a tropical species 

 and its distribution within the limits of 17° south and 20° 

 north latitude is fairly continuous. It was not found out- 

 side these limits except In the western Pacific, where it 

 extended in a continuous line to about 38 ° north off Japan 

 (station 115). It was conspicuously absent in the loop of 

 stations between the United States and Hawaii. It was 

 also notably absent from all the stations in the south- 

 eastern Pacific south of 20° south. An explanation for 

 this peculiar distribution is difficult to find. Certainly 

 it has no relation to temperature as many of the stations 

 where it does not occur have much higher temperatures 

 than many of the stations where it was found. The nutri- 

 ent content of the water cannot be a determining factor 

 either. The area north and east of the Hawaiian Islands 

 is extremely oligotrophic but so also is the region be- 

 tween Japan and Guam in the western Pacific, where the 

 species was foimd in large nimibers. Conversely, many 

 stations in the southeast Pacific region are in eutrophlc 

 water and yet did not support this species. Is it possible 

 that this species normally is confined within 20° of the 

 equator in the Pacific except off Japan where it is dis- 

 placed by the Kuroshio, or are the Carnegie records not 

 representative? 



Peters (1934) did not find C. lunula south of 30° south 

 latitude in the South Atlantic. The records of the Dana 

 (Nielsen, 1934) for the South Pacific fit in well with the 

 distribution compiled from Carnegie data. Most of the 

 Dana records duplicate records of the Carnegie between 

 Panama and Samoa but its records extend somewhat west 

 of Samoa. Nielsen, however, did not find the species 

 south of 20° south. Thus, It is probable that the Carne- 

 gie records are representative and that the species nor- 

 mally is as restricted as these records indicate. Since 

 the species Is displaced northward off Japan, it is sur- 

 prising that it is not also displaced southward in the 

 region of Easter Island. 



The total number of station records for the species 

 In the Carnegie collection was sixty-eight, of which twelve 

 were from the Atlantic and fifty-six from the Pacific. The 

 total number of sample records was 144, of which 88 were 

 rare, 52 occasional, and 4 common. The species was 

 found much more frequently In the net samples, with 121 

 net records and only 23 pump records. Thirty of the 144 

 records were in water containing less than 10mgPO4/m3. 



Ceratium lunula was always foimd in water of high 

 temperature. In the Atlantic the surface temperatures at 

 its stations were all above 24° C, except one which was 

 20.°5 C. In the Pacific the surface temperatures were 

 above 20° except at one station off Japan, where it was 

 19.°9 and at the Galapagos where it was 18.°7 C. The 

 ranges of environmental conditions in situ were: temper- 

 ature, ll.°4 to 29.°3 C; salinity, 29.7 to 37.0 per mllle; 

 pH, 7.71 to 8.47; phosphate 3 to 220 mg P04/m3. 



Ceratium' limula Is probably a shade species which 

 comes to the surface in waters rich in plankton. Nielsen 



(1934) found it in the deeper hatils in the stations poor in 

 plankton. Jorgensen (1920) found it at greater depths in 

 the Mediterranean during the summer months. The Car- 

 negie records, not segregated according to richness of 

 plankton, show the highest percentage of records at 50 

 meters and a greater percentage at 100 meters than at 

 the surface (table 33). These records thus corroborate 

 the classification of this species as a shade form. 



Table 33. 



Records of occurrence of C. lunula 

 at three levels 



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

 samples collected at that depth. 



40. Ceratium carnegiei n. 

 Figures 18A-C 



sp. 



Transdiameter 92.5 (90 to 100) microns (six speci- 

 mens measured). Curvature of antapical horns similar 

 to that in C. lunula . Apical horn long and straight or 

 slightly curved to right. Body of epitheca slightly to 

 greatly inflated. In extreme cases the walls are parallel 

 for about one transdiameter from the girdle, at which 

 point they may be expanded to greater than girdle diam- 

 eter. Body walls thick and covered with numerous lists 

 as In the heavy specimens of C. lunula . 



The species was foimd at four stations, all in the 

 Pacific. At one of these, station 71 off Peru, the body 

 was not much inflated. The most extreme cases were 

 found at the warmer stations, stations 151, 152, and 158. 

 It occurred at the surface at station 71, but at 50- and 

 100-meter depths at the other stations. The surface tem- 

 peratures at the stations where it was found, varied from 

 23.°5 to 28.°2C. The environmental conditions in situ were: 

 temperature, 12.°5 to 27.°6C; salinity, 35.9 to 34.0 per 

 mille; pH, 7.87 to 8.39; phosphate, 48 to 58 mg P04/m3. 



41. Ceratium contortum Cleve 

 Figures 18D-N, chart 32, appendix table 37 



There has been much confusion in the literal re- 

 garding of the taxonomy of both C. contortum Cleve and 

 C. karstenli Pavlllard ( C. arcuatum Cleve). After a 

 thorough study of the extensive material of the Carnegie 

 collection, the writers came to the conclusion that these 

 two species represent variants of a single species. The 

 difficulties of previous workers probably have been owing 

 in large part to the fact that they were attempting to dif- 

 ferentiate between these two forms when in fact they do 

 not exist and the separation is an artifical one. 



Thus, Jorgensen (1911) In his monograph gives C. 

 karstenli . C. longlnum . and C. contortum as distinct spe- 

 cies. Ceratium contortvun is characterized by slightly 

 distorted body and slightly inward-bent right antapical 

 horn, except in var. saltans Schroder, which has a v'ry 



