SHALLOW-WATER STARFISHES 3 



No doubt the comparative uniformity of the temperatures at all 

 seasons, and over vast areas, in the deep sea, is the principal cause 

 of the great abundance of starfishes and many other groups of 

 animals in the deep sea and of their wide distribution. 



Constancy of temperature at the breeding season, year after year, 

 is of the greatest importance to nearly all animals, both in the sea 

 and out of it, as the writer pointed out many years ago in the case 

 of birds,* and as has since been confirmed by other investigators for 

 birds and other groups. 



Another very favorable condition, for the multiplication of star- 

 fishes on this coast, is the vast extent and broken condition and rocky 

 character of the coast-line, with innumerable islands, bays, straits, 

 fiords, and inlets, affording every variety of stations and any amount 

 of shelter from severe storms, and at the same time furnishing 

 innumerable suitable stations on the rocky shores, for the growth 

 and increase of all sorts of plant and animal life, on which the star- 

 fishes may feed. It has been stated that the coast-line of Alaska and 

 the adjacent islands exceeds 26,000 miles, or more than the circum- 

 ference of the earth. That of British Columbia is also of vast extent. 



FOOD AND FEEDING HABITS OF THE STARFISHES. 



The littoral and shallow-water starfishes are nearly all carnivorous, 

 by preference, and feed very largely on the barnacles and mollusca 

 that live among, or attached to, the rocks, such as mussels, oysters, 

 limpets, chitons, small spiral gastropods, etc. 



Considering the great numbers and large sizes of many of the 

 starfishes, the wonder is that they have not already entirely exter- 

 minated those mollusca on which they largely feed. 



The vast amount of damage done to the cultivated oyster beds on 

 our Atlantic coast by a single small species of starfish (Asterias 

 forbesi) is well known. What then must be the destruction wrought 

 to the bivalves on the Pacific coast, where there are some forty 

 related species, with similar habits, many of them becoming over 

 two feet across ? 



One of our native starfishes, six inches across, will eat over twenty 

 small oysters in one day. Probably it would take a hundred oysters 

 or mussels to satisfy one of the giant starfishes of Alaska or Puget 

 Sound. 



1 Proceedings Boston Soc. Nat. Hist., vol. x, p. 259, 1866. 



