Do leeches need exercise?

Biopharm also experiments with tank size to give leeches the optimal amount of exercise. Carl Peters-Bond, who has worked for 24 years with Biopharm, is tank builder, leech grower, and personal trainer: leeches have to be exercised twice a day. It’s not complicated, as training programmes go. “I’ll go and pick one up and put it at the other end of the tank.”

It will swim, and it can lose weight quite quickly. Sometimes it gets more exercise than Carl bargained for. Their most annoying talent, he says, is for escape, even from Biopharm’s tanks. He has often arrived home to find some attached to his ankles. “I’m usually surprised if I don’t find 10 leeches in the footwell of my car.” When leeches swim, they travel fast and beautifully. On land, they move by suction: they suck with the front sucker, then the rear, and that is their locomotion: it is an efficient but not elegant movement. (It is nothing like earthworm locomotion, which is done by peristalsis-style burrowing, in waves.) But in water, they are different. They are sinuous. As Robert Kirk and Neil Pemberton write in their fine book Leech:

“By flattening and manipulating their bodies into wavelike patterns, leeches are capable of swimming at speed and with an elegance few other creatures can rival.”