Polychaetes, platyhelminthes, velvet worms, earthworms, peanut worms, pogonophorans and priapulids… one could be forgiven for thinking that there were no more kinds of worms to discuss in the Zoology channel…. but wait! there’s more!
May I pull aside the curtains of ignorance and allow the spotlight to fall on this most humble of worms, the spoon worm, or ‘better known’ scientifically as the echiurid, member of the protostome invertebrate phylum Echiura.
I admit that I have never had a personal encounter with an echiuran, so I would like to quote the venerable Paul A. Meglitsch who wrote the book Invertebrate Zoology in 1966. My copy is the 2nd edition, published in 1972, and is well worn as it is my invertebrate ‘bible’; the first text I turn to when I want information about the minor invertebrate phyla. This is Dr. Meglitsch’s description of the Echiura:
“Echiura is a small phylum of annelid-like, marine worms with a remarkable proboscis. The proboscis has greatly influenced their way of life and so played a big part in molding the evolutionary trends that have affected the adaptation of other body parts. Most Echiura retreat from the world, dwelling in burrows and crevices and thrusting the proboscis out as a periscope and food finder. They show considerable diversity in spite of an over-all sameness. Urechis and Echiurus build U-shaped mucous tubes in soft bottoms. Others live among rocks in convenient crevices or live in the shells or tests of other animals… Most Echiura are sedentary, but some move about considerably in captivity. Bonellia minor, when first put in an aquarium, probes about inquisitively with its sensitive proboscis. When an acceptable nook is found, it attaches and pulls the body into the space, proboscis first. It turns about and extends the proboscis once more , exploring the neighborhood before it begins to feed. The Bonellia proboscis is a remarkable instrument. [It] is only about 7 cm long when contracted, but can be extended to as much as 1.5 meters. When fully extended it is an almost tranparent thread.”
It was descriptions like this that made me want to meet the small invertebrates of the world first hand. I have even been lucky enough to be paid to study one type of marine worm and I found that they were not dull, stupid creatures but actually had interesting little lives and the ability to ‘think’, even though they had no brains. By thinking, I mean that they could investigate their surroundings and act according to their needs. I think Echiurans are the same. The little worm put in the above aquarium could look around ‘inquisitively’ and make decisions about where it went and what it did and it ‘explored the neighborhood’ much like a higher animal does when it is placed in a new environment.
My worms could build burrows to new food sources. They could recognise friend from foe and had different behaviour strategies for each. They even exhibited parental care. I suspect the same is true of spoon worms from Meglitsch’s description. We underestimate the intelligence of almost all creatures on earth. We think because we have language that we are the only thinkers in the world. Obviously there is an order or three of magnitude difference in how a worm ‘thinks’ to how we think but the point is that they are not just mindless robots. They are living beings with decision making powers.
We should remember that intelligence has not yet proved itself as a successful survival strategy. Spoon worms probably first evolved in the Cambrian Period three hundred million years ago and they are still here. We have been around as a species for only a million years or so. When we have survived for three hundred million years then we can talk about superiority!
Reference: P. Meglitsch 1972 Invertebrate Zoology 2nd edition Oxford University Press New York.