The deep sea is a very difficult environment to live in for a variety of reasons – not a lot of food, lots of predators, and the crushing weight of all the water above these animals. But one of the main problems with living in the deep sea is that below 200m of water there is very little natural sunlight getting that deep and after about 1000m there is no natural light at all! The abyssal grenadier lives all the way down to 4000/5000m where there is no natural light so it is hard for them to see anything. (Although some other deep sea animals produce their own light using bioluminescence!) Because it’s very dark the abyssal grenadier relies more heavily on its sense of smell to detect food.
I know your question was not addressed to the Baltic clam, but you might be interested to know that some bivalves have eyes! (not the Baltic clam, sadly). Scallops, for example, have better vision than cats!
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Baltic clam commented on :
I know your question was not addressed to the Baltic clam, but you might be interested to know that some bivalves have eyes! (not the Baltic clam, sadly). Scallops, for example, have better vision than cats!
Common starfish commented on :
and starfish have 5 eyes … one at the end of each arm.