Bipolar variation inClione, a gymnosomatous pteropod

The gymnosome Clione inhabits waters of the Arctic, North Pacific, North Atlantic, South Atlantic
and Antarctic Oceans. This study reexamines bipolarity in this genus, utilizing new morphological techniques
as well as observations of living animals in all locales. Differences in exernal anatomy are readily
apparent in both larval and adult Clione from northern and southern areas, and scanning electron
microscopy has revealed differences in the number and size of hooks in animals from different regions.
The configuration of the radula differs between specimens from the northern and southern hemispheres,
and Clione from the Antarctic lacks median radular teeth, in contrast to the well developed, sickleshaped
median teeth present in C/ione from northern areas. Clione acts as a food specialist throughout
its range, feeding either on the bipolar thecosome species Limacina helicina (Phipps) in cold waters
or L. retroversa (Fleming) in temperate waters. Differences in maximum adult size of Clione can be
related to the size of available prey. Although there do not appear to be differences in the feeding
behavior of Clione from different areas, there are slight differences in swimming and escape behavior,
particularly between specimens of Clione from northern and southern regions. The results of these
anatomical and behavioral observations support the validity of recognizing two species of Clione, C.
limacina (Phipps) in the northern hemisphere and C. antarctica (Smith) in the Antarctic and South Atlantic oceans.

Florida Atlantic University. Harbor Branch Oceanographic Institute contribution 749

This manuscript is an author version with the final
publication available and may be cited as: Gilmer, R. W., & Lalli, C. M. (1990). Bipolar variation in
Clione, a gymnosomatous pteropod. American Malacological Bulletin, 8(1), 67-75.