Morphology of Cycladophora davisiana davisiana from the Atlantic Ocean

• Main Authors: Bjorklund, Kjell R, Ciesielski, Paul F
• Format: Other/Unknown Material
• Language: English
• Published: PANGAEA 1994
• Subjects: 105-646B; 114-704A; 38-336; A3460; B3379; Cleve_stations; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; GC; Glomar Challenger; Gravity corer; Joides Resolution; Labrador Sea; Leg105; Leg114; Leg38; North Atlantic/Norwegian Sea; North Atlantic Ocean; Ocean Drilling Program; ODP; PLA; Plankton net; South Atlantic Ocean; Greenland; Iceland; North Atlantic; Norwegian Sea
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.690418; https://doi.org/10.1594/PANGAEA.690418

In recent years, temporal fluctuations in the abundance of C. d. davisiana have been used frequently as a highresolution stratigraphic and paleoenvironmental tool. The modern ecology and morphologic variation (temporal and geographic) of this radiolarian species is evaluated to ascertain its potential stratigraphic and paleoenvironmental significance. Statistics were obtained on the width and height of all C. d. davisiana segments from Pleistocene populations of differing ages from the Northern Hemisphere (Labrador Sea and Iceland-Faeroe Ridge) and Southern Hemisphere (Namibian shelf and Meteor Rise). Results reveal that segment height variations between and within populations are more conservative than segment width. The mean sizes of the thorax and first abdominal segment have distinguishable differences between C. d. davisiana found in the North and South Atlantic. All populations have no significant difference in first abdominal segment width, however, mean heights of this segment differ greatly between populations of the North and South Atlantic. Second abdominal segment sizes show no clear population grouping. Size differences in post-cephalic segment size of these populations would appear to be related to some isolation of gene pools and possibly unknown paleoenvironmental factors. Temporal changes in the postcephalic size of C. d. davisiana may be used to: (1) identify temporally equivalent peaks in abundance of the species in a given region, (2) possibly evaluate the degree of mixing of water'masses between regions, and (3) trace the initial spread of the species from its area of origin. Cleve's 1887 plankton samples, between Greenland and Spitzsbergen, were studied and used in conjunction with other data to make the following conclusions on the modern ecology of C. d. davisiana in the Arctic and Greenland-Norwegian Seas. (1) It is presently absent in surface water plankton samples, (2) it currently lives at depths below 500 m, where it is rare, (3) it does not live in the upper 200 m under Arctic ice ...