CERATIUM SPECIES OF CARNEGIE COLLECTION 



35 



decidedly distorted body and sharply bent right antapical 

 horn. Jorgensen's figure of C. karstenii (fig. 117a), 

 however, shows a specimen with a curled right antapical 

 horn, which is certainly to be considered a double bend- 

 ing and represents a zone of instability in the same po- 

 sition as the bending In the horn of contortum. He rep- 

 resented C. longinum as more slender than C. karstenii 

 and with longer and straight antapical horns. He also 

 separated from C. karstenii . var. robustum . a variety 

 which is more robust than the main species and has 

 shorter and straight antapical horns. This form resem- 

 bles C. tripos. 



Later, Jorgensen (1920) foimd all intergrades between 

 C. karstenii and var. robustimi so he no longer consid- 

 ered it even a good variety. 



Peters (1934) treated C. longinum as a variety of C. 

 karstenii. He apparently considered saltans a distinct 

 variety of C. contortum. but does not give a figure of the 

 mainspecies. His figures of C. karstenii and C. contortum 

 (figs. lOe and g, plate 2) show equally distorted bodies. 

 Nielsen (1934), in his study of the Dana South Pacific 

 material, treated C. karstenii and C. contortimi sepa- 

 rately. He agreed with Peters (1934), however, thatvar- 

 robustum cannot be separated from C. karstenii. He 

 stated that he did not find C. longinum in his collections 

 but his figure of C. contortum f . subcontortum (fig. 52) 

 answers well to this form. He considered it a shade 

 form of C. contorhmi. 



In the Carnegie collections every possible intergrade 

 was found between C. contortum . C. lohginum . and C. 

 karstenii . and the varieties robustum and saltans (see 

 fig. 18). There are heavy forms and light forms; some 

 with long horns and some with short. There are speci- 

 mens with kinked horns, but not much distorted body; 

 and, on the other hand, specimens with regular body, but 

 bent horns. The right antapical may bend in or out, or 

 may trail off in an attenuated manner. The extreme 

 forms were represented by var. saltans and usually were 

 smaller than the others and it was thought for a wMle 

 that a separation of two species could be made on this 

 basis. After measiiring many specimens from all local- 

 ities, however, it was foimd that this was impossible. 

 There is indeed a great variation in size. The transdl- 

 ameters range from 52 microns in the smaller specimens 

 of saltans to 110 microns in the more robust specimens. 

 There was no segregation into size groups, however; the 

 greatest number of specimens had transdiameters rang- 

 ing between 70 and 85 microns. 



Ceratium contortum is a common, slightly tolerant 

 tropical species. It was found at practically all stations 

 in the warm Atlantic, warm Pacific, and southeast Pa- 

 cific regions, but was completely absent from the cold 

 North Atlantic and cold Pacific regions (chart 32). 



Nielsen (1934) listed C. longinum Karsten as an At- 

 lantic form absent from the Pacific. It occurred in the 

 Carnegie collection, however, at many stations in the 

 Pacific. 



The commonness of the species is shown by the 

 large nimiber of sample records, namely, 461, of which 

 194 were rare, 178 occasional, 84 common, and 5 abun- 

 dant. The net records for the species totaled 327; the 

 pump records, 134. 



The range of surface temperatures at the stations 

 where the species occiirred, varied from 16.°3 to 29.°5C. 

 The ranges of environmental conditions in situ were: 

 temperature, ll.°4 to 29.°4 C; salinity, 30.0 to 37.1 per 

 mille; pH, 7.17 to 8.47; phosphate, 2 to 138mgP04/m3. 



Many of the specimens have attenuated and sometimes 

 curved antapical horns which are extremely thin-walled. 

 It is probable that this is an adjustment to shade condi- 

 tions. Nielsen (1934) considered the subcontortum form 

 (longinum ?) a shade form of C. contortum. In the Car- 

 negie material var. saltans showed a greater frequency 

 at greater depths than did the more regularly-shaped 

 forms. Although the more robust forms sometimes oc- 

 curred with thin antapicals, this condition was much 

 more common in the saltans group. In the others the 

 larger specimens were much more predominantly sur- 

 face forms. Among the specimens more than 80 microns 

 in diameter, there were twice as many surface records 

 as 50-meter records and very few at 100 meters. Of the 

 specimens less than 80 microns in diameter, the number 

 of records at the siirface and 50 meters was about equal, 

 although the number at 100 meters was almost negligible. 

 Among saltans , too, the greatest frequency was at the 

 surface. The percentages for the species as a whole 

 show a predominance at the surface (see table 34). 



Table 34. 



Records of occurrence of C. contortttm 

 at three levels 



Rare 



Occasional 

 Common 

 Abundant 



Total 



95 



80 



34 



4 



27.7 



20.7 



8.8 



0.2 



54 

 53 

 33 







19.2 

 18.7 

 11.7 



45 17.7 



45 17.7 



17 6.7 



1 0.4 



213 



57.4 140 49.6 108 42.5 



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

 samples collected at that depth. 



42. Ceratium limulus Gourret 

 Figure 19A, chart 33, appendix table 38 



This is a rather rare intolerant tropical species 

 which Is quite characteristic and not very variable. 

 Peters (1934) considered this species an indicator of 

 warm ollgotrophic water in the South Atlantic; but Niel- 

 sen (1934) foimd it in both oUgotrophic and eutrophic 

 water in the South Pacific, with its greatest abundance in 

 eutrophic water. In the Carnegie collection it was found 

 only in ollgotrophic water in the Atlantic, but in both eu- 

 trophic and oUgotrophic water in the Pacific. Is it pos- 

 sible that the Atlantic form is less adaptable in this re- 

 gard than the Pacific form? 



The species was found at fifty-five stations — nine in 

 the Atlantic and forty-six in the Pacific. The Atlantic 

 stations were confined to the warm Atlantic region where 

 the surface temperatures were high (from 24.°8 to 27.°6 

 C) and the nutrient content of the water was low. The 

 phosphate values for the upper 50 meters were all below 

 11 mg P04/m3. In the Pacific the stations were confined 

 to the warm Pacific region for the most part, although 

 there were six stations in the southeast Pacific region. 

 The range of conditions at the Pacific stations was much 

 greater than those at the Atlantic stations. For instance, 

 the surface temperatures varied from 18.°7 to 29.°3 C, 

 and the mean phosphate value for the upper 50 meters 

 varied from 4 to 83 mg P04/m3. It should be noted, how- 

 ever, that all stations were remote from continents. 



