Lampreys

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Although in the recent past they may have been one of the most numerous and widespread inhabitants of our cleaner rivers, it is their mode of life that explains why they are so seldom seen by a casual observer. The chief characteristic and the one that has contributed most to their survival is that 60-80% of their entire lifespan is spent as a distinctive blind, larval stage known as the ammocoete. Even during the adult stage, this is a wholly nocturnal creature, passing its existence burrowed under the banks of mud along the sides and bottoms of rivers.

Lampreys occupy a key position in our evolutionary story and can be grouped with a select number of animal species, commonly referred to as 'living fossils'; among these are the ancient king crab, the coelacanth and the lungfish. All have relatively long evolutionary histories and still show some of the primitive characteristics that are seen in similar and related fossil animals.

In this respect, the lamprey's claim to evolutionary priority is unimpeachable. This rests on the complete absence of the usual hinged vertebrate jaws and the way the mouth is surrounded by a circular disc or sucker. A similar arrangement is found in its closest relation, the strictly marine hagfishes. These, together with the lampreys, are sometimes grouped together as cyclostomes or round mouthed vertebrates. They are the only living vertebrates without true jaws; a condition also shared by the very first fossil fishes, the ostracoderms.

Ranking amongst some of the greatest of animal survivors, the cyclostomes have passed unscathed through all five of the major mass extinctions that throughout the history of life have annihilated vast swathes of animal life. How they achieved this unparalleled immunity, is one of the most intriguing and puzzling features of vertebrate history.

"I wish this book had been available when I was teaching at university ... I recommend it for general readers as well as specialists" - ML Augee, Proceedings of the Linnean Society of New South Wales Volume 128 (2006).

"I never got the chance to meet Martin Hardisty ... Reading this book, with its easy tone and its numerous quotes from early naturalists, made me wish I'd met him. It inspired me to drop the lab reports I was grading (and this review) and take a morning to find brook lampreys spawning. If this book inspires others to appreciate lampreys as well, it will serve its purpose." - Philip A Cochran, ESA, 2007