Circulation, respiration and fluid dynamics in the gastropod mollusc, Hemifusus tuba (Gmelin)

Abstract

Cardiac activity, respiratory rate, and fluid movements in and out of the shell and tissues of Hemifusus tuba (Gmelin) have been investigated. Estimates of cardiac output (Q̇) were in the range 0.1 to 2.22 ml·min −1 (in individuals of 7.0 to 14.2 cm shell length). Maximum systolic ventricular pressure was between 6.4 to 11.4 cm H 2O, with highest values being recorded from large, partially-retracted specimens. Respiratory rate (V̇ 2) increased with size according to V̇ O2 α dry weight (g) −0.43. This mass exponent is low compared with that for many other species. Perfusion indices ( Q ̇ V ̇ o2 ) increased with size indicating that del was less efficient in larger Hemifusus. During retraction, two phases of fluid expulsion were recognized. The first allowed Hemifusus to retreat rapidly within the confines of its shell. The second, slower phase of retraction drew up the operculum to form a tight, protective seal with the shell. Expelled fluid, particularly from the second phase, contained blood proteins, suggesting that fluid is lost from the blood system during full retraction.