Promoting Intertidal Sciences, Conservation & Education Studies | blog | 4th July | Dr Mike Kent

One of the joys of walking along the Polzeath shore at low tide is that you never know what you will discover. It might be something dramatic like a stranded seal. A few years ago I came across Jeremy Clarkson covered from head to foot in neoprene for a seaside episode of Top Gear; he only looked like a stranded seal.

I discovered nothing dramatic on my foray across the sands on Tuesday July 3rd. But I did come across a shell which got me thinking that appearances can be deceptive.

The shell was that of a long-legged spider crab (Hyas sp.), distinguished from common shore crabs by its shell being longer than it is wide, and by having a carapace with many small but sharp spines. In addition to the spines deterring predatory fish and birds, they have a less obvious function. A spider crab uses pincers at the end of its long legs to grab and detach seaweeds, sponges and other immobile living things from their surroundings. Then by amazing acts of contortion plants them onto all parts of its back.

When fully adorned with items from its living landscape, a spider crab is so beautifully camouflaged that on first appearance it is indistinguishable from its surroundings. This masking has offensive as well as defensive purposes, hiding the crab from the wary eyes of prey as well as the prying eyes of predators. It is not uncommon when searching for life in rock pools to tread unwittingly on the spiny crab. For anybody with bare feet, this can be quite painful.

Back in mid-June, searching for crabs at Baby Bay, I found what looked like a solid mass of mobile weed. It was not until I turned it over that I could see a spider crab hidden beneath the weed. My encounter brought to mind the phrase “Things are not always what they seem”. Googling the derivation of these words, I found that they are part of a quotation in Phaedrus, Plato’s socratic dialogue written around 370BC. The full quotation is

” Things are not always what they seem;

the first appearance deceives many;

the intelligence of a few perceives

what has been carefully hidden.”

It could be summarized as

“He who has eyes, let him see!”.

The quotation reflects the belief held by many philosophers in ancient Greece that the world is very different from how we perceive it through our senses.

Jesus said something very similar to a large crowd gathered around him on the shores of Galilee. After telling the parable of the sower, he exclaimed

“He who has ears, let him hear!”

Matthew 13:9

Tom Wright, in Matthew for Everyone, explains that Jesus said these words to alert his listeners to the fact that, because the story wasn’t exactly what they were expecting, they would probably have to think carefully to understand its meaning. To quote Wright “It wasn’t a story about God sowing Israel in its own land at last, restoring its fortunes to the sort of greatness they had always dreamed of. It was a story of both success and failure. It is cryptic.” Like the clues in a Times crossword or a moving mass of seaweed, the parable requires thoughtful investigation to reveal what is hidden.