Marine Science Faculty Publications

Coiling Direction in Amphistegina

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In material from 67 geographically widespread tropical and subtropical localities, Amphistegina lessonii and A. bicirculata were predominantly sinistrally coiling, while A. gibbosa, A. papillosa and A. radiata were predominantly dextral. A. lobifera was predominantly sinistral in the Indo-Western Pacific material, with dextrality increasing eastward across the Pacific to a maximum of over 90% in the Hawaiian Islands. Isoclines of dextrality for A. lobifera in the central Pacific showed a pattern apparently influenced by the equatorial current system.

Populations of A. lessonii and A. lobifera from Palau and Hawaii showed age-specific changes in the coiling proportions: the proportions of dextrals (sinistral in A. lobifera from Hawaii) increased in adult size classes. Temporal changes in coiling proportions of both species were observed in Hawaii and the Gulf of Elat. Raised temperatures off a power plant coincided with coiling direction deviations. In the laboratory, coiling proportions in clones were independent of coiling direction of individual clone parents.

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Marine Micropaleontology, v. 4, p. 33-44