Flatworm

Chapter 6 Flatworm
 
page 87 various phyla of worms...among the phyla not mentioned in the book is Acanthocephala, the Thorny-headed worms.  Their spikes have inspired better sticky medical tape.

 page 91: parasites. See Carl Zimmer on Blood flukes (parasitic flatworms) and the fountain of youth.  A kind of parasitic flatworm, Ribeiroia, can cause a frog to grow debilitating extra legs.

page 93: death. philosophical tangles and reflections from Jeff McMahan and John Broome and Stephen Cave.  

This is the seventh in a new series of notes and comments on chapters in The Book of Barely Imagined Beings. It appears around the time of the US publication, and adds to an earlier series that appeared around UK publication. 

Regeneration

Imagine that someone cut off your ear and tossed it on the ground, where it promptly grew into a complete copy of yourself–complete with a new brain.

The parasite's fountain of youth by Car Zimmer with image from paper by Daniel Lobo, Wendy S. Beane and Michael Levin.

A many legged beast

Extra legs sprouting on frogs, first observed in North America in the 1990s, were found to be caused by the parasitic flatworm Ribeiroia, writes Carl Zimmer:

Ribeiroia starts out life in snails. It grows and reproduces inside the snails, which it castrates so that they don’t waste time on making eggs or looking for a mate. In its castrated host, the parasite produces a new generation of flatworms that can escape the snail and swim in search of a vertebrate host. They typically infect fish or tadpoles. When they invade tadpoles, the parasites bury themselves in the tiny buds that will eventually grow into legs.

An apparent increase in the rate of these deformities may be due to increased concentrations of pesticides in the ponds in which the frogs live. Pesticides can kill off the parasites but they also lower the defenses of the frogs, which may lead to higher infections.

A paper in Nature suggests another factor in the success of leg-deforming parasites: declining biodiversity. In ponds with 'high' biodiversity – up to six species of amphibians – the parasites do much worse at getting transmitted than in low diversity ponds. This is not a small difference: there is a 78.5% decline in deformed frogs in high-diversity sites.

Day of the dead

Thirteenth in a series of notes and comments on The Book of Barely Imagined Beings

Chapter 6: Flatworm

page 92: Everything that lives is holy. On occasion, Annie Dillard entertains a different view:

I don't know what it is about fecundity that so appalls. I suppose it is the teeming evidence that birth and growth, which we value, are ubiquitous and blind, that life itself is so astonishingly cheap, that nature is as careless as it is bountiful, and that with extravagance goes a crushing waste that will one day include our own cheap lives. Every glistening egg is a memento mori.

page 93: an attitude vaguely adequate in the face of [death].  Michel de Montaigne wrote:

To philosophize is to learn how to die: Where death waits for us is uncertain; let us look for him everywhere. The premeditation of death is the premeditation of liberty; he who has learned to die, has unlearned to serve.  

In The Hit, a 1984 gangster film, Willie Parker (played by Terrence Stamp) seems to be living with this attitude (see this clip) but looses it in the end (see this clip).

page 96: spicy delights of the soil.  See, for example, My mushroom burial suit (TED talk) by Jae Rhim Lee.


P.S. A note from a year ago and some wise words from Christopher Hitchens

A salmagundi of worms

Twelfth in a series of notes and comments on The Book of Barely Imagined Beings

Chapter 6: Flatworm

page 83: Penis worms. A study on the development of priapulids (penis worms)"throws doubt on a feature that has been thought for more than 100 years to define the largest branch of the animal tree of life." For more on deuterostomes see marginal note on page 47.

page 83: Other posts on this blog relating to Ediacaria here.

page 85: other creatures evolved more formidable features for attack and defence. See, for example, Diania cactiformis.

page 87: H mephisto. Here is an image of a "devil worm," the deepest-living animal yet found.

page 87: C. elegans. Here is an image from The Open Worm Project (used to illustrate this article):

page 88: Annelids, the segmented worms, are a large and diverse group. They include scale worms, polychaete worms with an eversible pharynx. Most of the time their jaws are tucked away, but when the worm wants to feed, the entire front of their throat rolls out of their mouth.

Polynoid scale worm

page 88: Christmas tree worms. Shown here:

page 91: tapeworms and other lovelies. Graphic and horrible but fascinating: Brain Parasites, California’s Hidden Health Problem.

Flatworm

Stephen Cave's playful approach to flatworms suggests his forthcoming book will be a good read. Let's hear it for monkey testicle grafts.

There's a chapter on the flatworms (and other worms) in The Book of Barely Imagined Beings. I  signed off final corrections in January but the book doesn't appear until October.

P.S. A striking image of mating terrestrial flatworms

P.P.S. A Cave tweet