Simultaneous observations of haemolymph flow and ventilation in marine spider crabs at different temperatures: a flow weighted MRI study

In vivo magnetic resonance imaging (MRI) and angiography were applied to th e marine spider crab Maja squinado for a study of temperature effects and t hermal tolerance. Ventilation and haemolymph circulation were investigated during progressive cooling from 12 degreesC to 2 degreesC. The anatomical r esolution of MR images from Maja squinado obtained with a standard spin ech o sequence were suitable to resolve the structures of various internal orga ns. The heart of the animal could be depicted without movement artifacts. T he use of a flow compensated gradient echo sequence allowed simultaneous, o bservations of ventilation, reflected by water flow through the gill chambe rs as well as of haemolymph flow. Simultaneous investigation, of various ar teries was possible by use of flow weighted MRI. In addition to those acces sible by standard invasive flow sensitive doppler sensors, flow changes in gill, leg arteries and the venous return could be observed. Both ventilatio n and haemolymph flow decreased during progressive cooling and changes in h aemolymph flow varied between arteries. Haemolymph flow through the Arteria sternalis, some gill and leg arteries was maintained at low temperatures i ndicating a reduced thermal sensitivity of flow in selected vessels. In sup port of previous invasive studies of haemolymph flow as well as heart and v entilation rates, the results demonstrate that the operation of gills and t he maintenance of locomotor activity are critical for cold tolerance. A shi ft in haemolymph flow between arteries likely occurs to ensure the function ing of locomotion and ventilation in the cold. (C) 2001 Elsevier Science In c. All rights reserved.