The sinking velocities of some halocyprid ostracods

Abstract

The following mean passive sinking velocities were obtained from ≈ 250 individuals belonging to nine species of Conchoecia: 1.00 cm sec −1 (36.0 m h −1), C. imbricata (Brady), C. inermis (Claus), C. elegans Sars; 1.00–1.20 cm sec −1 (36.0–43.2 m h −1), C. ametra Müller, C. loricata Claus, C. rhynchena Müller; 1.20–1.40 cm sec −1 (43.2–50.4 m h −1), C. haddoni Brady & Norman; 1.40–1.60 cm sec −1 (50.4–57.6 m h −1), C. hyalophyllum Claus; 1.80–2.00 cm sec −1 (64.8–72.0 m h −1), C. lophura Müller. Most ostracods were allowed to sink under two conditions: 1. 1) unanaesthetized and 2. 2) after being anaesthetized with a 2.5 % solution of urethane. Sinking rates may vary widely within a species but were not affected by the use of urethane or by the sex, size or orientation of the sinking animals. There is, however, some correlation between the passive sinking velocity and the size of the gut contents and egg mass. Head-first, controlled sinking ( i.e., control of buoyancy) was observed in all the species investigated except C. elegans. No adequate method of buoyancy control in Conchoecia could be suggested.