824 NATUEAL HISTOEY OF AQUATIC ANIMALS. 



228. THE AMPHIPODS. 



THE BEACH PLEAS, OR SAND FLEAS ORCHESTIA AGILIS, Smith; SCUDS GAMMARUS LOOUSTA, 



Gould; AND ALLIED FORMS. 



The exteusive group of Amphipoda, to which these species belong, consists entirely of small 

 aquatic animals which, although not of direct importance from an economical point of view, still 

 serve an important purpose in the general economy of nature, and deserve at least some mention 

 here. Besides serving as food for fish, many of the species act as scavengers on the sea-shore, 

 and, despite their small size, are, from their great numbers, able to dispose of a large quantity of 

 dead refuse matter. Some of the species live entirely in the water, while others are exposed to 

 the air during low tide, or even most of the time. The experiment of utilizing these small creat- 

 ures in the preparation of skeletons for anatomical purposes has been tried with much success. 

 Fish, cleaned of the bulk of their flesh, have been fastened to boards and anchored just below the 

 surface of the water, near the docks in Eastport Harbor, and within the space of a few hours 

 nothing but the bones remained, being cleaned as completely as by any other process, and with 

 but little expenditure of time on the part of the naturalist. Several species upon our coast are 

 abundant enough to act in unison in this way. Some of the deep-water species are as destructive 

 to dead animal matter as are those which live near the shore. The cod and halibut fishermen 

 often suffer from their depredations, as several of the deep-water Amphipods quickly attack the 

 fish which die after being caught on the trawl lines before they are hauled up. The gills of the 

 fish appear to be first devoured, but within a few hours they are able to eat out the entire 

 muscular and visceral matter, leaving only the bones and skin. Cod and hake frequently die 

 upon the trawls, and are thus destroyed, but halibut are more hardy and are seldom much 

 injured. 



The number of species of Amphipods upon our coast is very large, but we need refer here to 

 only two or three species to illustrate their principal characteristics. 



" These small Crustacea are of great importance in connection with our fisheries, for we have 

 found that they, together with the Shrimps, constitute a very large part of the food of most of our 

 more valuable edible fishes, both of the fresh and salt water. The Amphipods, though mostly of 

 small size, occur in such immense numbers in their favorite localities that they can nearly always 

 be easily obtained by the fishes that eat them, and no doubt they furnish excellent and nutritious 

 food, for even the smallest of them are by no means despised or overlooked even by large and 

 powerful fishes that could easily capture larger game. Even the voracious bluefish will feed 

 upon these small Crustacea where they can be easily obtained, even when menhadeii and other 

 fishes are plenty in the same localities. They are also the favorite food of trout, lake white-fish, 

 shad, flounders, scup, etc., as will be seen from the lists of the animals fouud in the stomachs of 

 fishes. One species, which occurs in countless numbers beneath the masses of decaying seaweeds 

 thrown up at high-water mark on all the shores by the waves, is the Orchestia agilis Smith, which 

 has received this name in allusion to the extreme agility which it displays in leaping when 

 disturbed. The common name given to it is 'Beach-flea,' which refers to the same habit. Its 

 color is dark olive green or brown, and much resembles that of the decaying weeds among which 

 it lives, and upon which it probably feeds. It also constructs burrows in the sand beneath the 

 vegetable Mbris. It leaps b.v means of the appendages at the posterior end of the body. 



"A much larger species, and one of the largest of all the Amphipods, is the Gammarus 

 locwtn, which occurs in great numbers beneath the stones and among the rock-weed near low- 



