198 



MARINE ANIMALS 



is submerged. Its food includes small insects as well as crabs. Sup- 

 ported on its tail and paired fins, it hops about on the mud and may 

 climb the inclined branches of mangrove. A great number of birds, 

 certain reptiles, and a few mammals (monkeys) frequent the man- 

 grove flats for food, but have their residence in the adjoining forest. 

 The mangrove strand has a very similar development of animal life in 

 West Africa, the Indian and Pacific oceans, and in South America. 



Littoral with solid substratum: eroding shores. — -The fauna of 

 solid bottom, especially of rock, stands in sharp contrast with that of 



Fig. 33. — Periophthalmus koelreuteri, the mudskipper, two-thirds natural size. 



After Hickson. 



the loose substratum. This is especially obvious where single shells of 

 mollusks, stones, rock outcrops, or harbor works and breakwaters are 

 juxtaposed to the loose bottom. A quite different community of animals 

 appears immediately on such a foothold. The submarine rocky bosses 

 which project from the ooze of the quiet water in the Bay of Naples 

 support a wholly different population from that of their surroundings. 

 There are a few forms common to the two habitats, especially 

 predaceous starfishes and crabs, and a few adaptable forms, like 

 Mytilus. Altogether, however, the difference is radical and obvious. 



Sessile forms are especially characteristic of the solid bottom. The 

 majority of sponges and of sessile coelenterates are confined to rocks, 

 scarcely requiring other protection against predators than their 



