A DAPHNID 45 



Class : Crustacea. Division : Entomostraca, Order : Phyllopoda 

 A DAPHNID 



The Daphnidae are a family of small fresh-water crustaceans 

 common in lakes and pools. They should be studied under the 

 microscope and alive if possible. Place one or more on a slide 

 with a few strands of cotton under a cover glass two corners of 

 which are supported by wax, and draw off enough water to keep 

 them quiet ; also observe several in a watch glass. The body of 

 the animal will be seen to differ in shape from those crustaceans 

 already studied. It is but indistinctly segmented, and, except the 

 head, is entirely covered by a bivalve shell. This shell is the 

 cuticular covering of paired folds of the dorsal integument, one 

 fold covering each side of the body. Beneath the opening of the 

 valves of the shell appear the appendages and the abdomen ; on 

 the surface of the shell a meshwork of fine lines can usually be 

 seen. Notice the large, median eye ; it may often be seen to 

 tremble sHghtly. The shell has a deep, ventral indentation near 

 the base of the antennae. 



The first pair of antennae is very small, but may be easily seen 

 projecting downward just back of the eye. The second pair of 

 antennae is very long and biramous, the two branches being the 

 exopodite and endopodite; they are the principal organs of 

 locomotion. Just back of the antennae is a large flap, called the 

 upper lip, and back of this are the large mandibles. There is but 

 a single pair of maxillae, and they are so small that they will 

 probably not be seen. Four to six pairs of thoracic appendages 

 follow, the function of which is probably exclusively respiratory. 

 How many are present in your specimen? Notice the leaflike 

 surface of these appendages (whence the name Phyllopoda) and 

 their complex form. The short abdomen articulates with the 

 thorax and is bent beneath it, where it may be seen often moving 

 rapidly back and forth. 



Exercise 1. Draw an outline of a side view of the animal on a large 

 scale and label the appendages and other parts observed. 



