Tomasz Wilk (Poland) notices fountains of water-borne larvae being squirted from the shallows by a thick-shelled river mussel.
Having forgotten their tent on a family camping holiday, Tomasz and his wife got ready to sleep in the open on a sandy bank beside the Nida River in Poland. Had they been in their tent, they might never have noticed the little fountains of water in the shallows. Making the most of the limited equipment he had brought with him, Tomasz got his wife to hold a torch to backlight the scene.
The sprays of water turned out to be how thick-shelled river mussels give their parasitic young a chance to find a host. In spring, mature females migrate to the river’s edge where it’s shallow enough for them to raise one end of their shell above the waterline and release their offspring. Once in the water, the larvae attach to the gills of fish, where they live harmlessly until they become juvenile mussels.
Once common in European rivers, numbers of thick-shelled river mussels have declined by 90 % since the 1970s, mainly due to the degradation of waterways.
Poland
Tomasz has been interested in nature since his early years. He studied the ecology of birds for both his MSc and PhD and has worked for the Polish Society for the Protection of Birds. In recent years, he’s been trying to capture the beauty of nature in his photographs. To do so, he travels a lot, visiting more than 40 countries on five continents.
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