Giant Clam

Clams recycle urea for algae, according to reports in Inside JEB 19 April 2018, and Journal of Experimental Biology 14 March 2018, doi: 10.1242/jeb.176313.

Giant clams live in close symbiotic relationship with marine algae known as zooxanthellae, which produce nutrients for the clam by photosynthesis.  The algae can make sugars from carbon dioxide and water, but to make amino acids they need nitrogen, which they obtain from ammonia (NH3) excreted into sea water by fish, then absorbed by the clams who supply it to the algae.

However, there are other sources of nitrogen in sea water, mainly urea, another waste product from sea dwelling animals.  A team of scientists in Singapore have studied the fluted giant clam Tridacna squamosa to see if it could absorb urea.  To do this it needs a protein transporter, i.e. a large protein that pumps urea molecules from the seawater into the clam’s surface cells.  The research team found there was such a protein transporter in the clam’s gills, but were intrigued to find the amount of that transporter protein increased by up to eight-fold during the daylight hours. The urea transport process does not need light, but the algae that use the urea do.

This is a beautiful example of coordination in that the clam absorbs most urea and supplies it the algae when the algae are most active.  The algae then break it down to ammonia to use to make amino acids, and carbon dioxide to use in photosynthesis to make carbohydrates.  These processes supply food for both the algae and the clams.


Editorial Comment: Symbiotic relationships have been known for a long time, but this is a particularly clever example of close cooperation between an animal and a plant.  The clam, which does not photosynthesise, gathers a raw material that is of no use to it, at a time that is most useful to the photosynthetic algae.  This means the clam not only needs to have a urea transport protein, and a method of transporting urea to the algae, but it also needs to a programmed knowledge that the algae need more urea during daylight.  The algae then convert the urea to raw materials for photosynthesis and amino-acid synthesis for the benefit of both it and the clam.

What a good reminder that in the beginning God created a fully functional world that worked by cooperation, without any struggle and competition.  Even now, living things depend on cooperation to live well.  Darwin’s struggle for life and war of nature is the result of degeneration of the world, and had nothing to do with its creation.

What a wonderful re-cycling effort eh? Thumbs down to Darwin and Dawkins, Attenborough and Cox, and a big Thank You Jesus.

This brilliant close symbiosis, which also give clams their beautiful colours, is also a challenge to those so-called Bible believing Christians who claim that God used evolution, i.e. Darwin’s “struggle for life” and “war of nature”, as the process of creation.  These competitive processes are real in today’s world, but they are the result of degeneration of the world following human sin and God’s judgement.  Close symbiosis like the algae and the clam, along with other loser examples of co-operation, proclaim that the world was created “very good” and that should be the starting point for all those who claim to believe God’s Word.

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Evidence News vol. 18, No. 5
30 May 2018
Creation Research Australia