"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift
April 24, 2010
April 24 - Halocercus delphini
Living in the respiratory tract of a whale presents certain challenges that are not faced by those inhabiting the respiratory tract of a terrestrial mammal. Whales and other cetaceans are well-known for their dramatic expiration when they surface to take take a breath, so if you are going to be a parasite that lives in the respiratory tract of a cetacean, you better have a way to hold on tight! Fortunately for the whale lungworms (and unfortunately for the whales), there are some parasites that can do just that. Halocercus delphini is a parasitic nematode which lives in the lung of dolphins. To ensure that it won't be dislodged and expelled when its host takes a breath, the worm plunges its anterior end into the host tissue, forming a capsule which acts an anchor that holds the worm firmly in place. Halocercus delphini is just one species of many from a family of parasitic nematodes (Pseudaliidae) that infect the respiratory, circulatory, and auditory systems of cetaceans.
Contributed by Tommy Leung.