Macrobenthos 325 



Despite the fact that the total number of developing eggs carried internally 

 is linearly related to total length of the organism (Figure 7-12), even the 

 smallest animal has enough developing eggs to continue production at the 

 maximum rate until the freeze in mid-September. 



Accurate counting of the Lepidurus population was difficult because 

 of their low numbers and because of the benthic stage of their life cycle. 

 The planktonic larvae, in contrast, were quite easy to collect with a large 

 net (10x50 cm). Both core and Ekman dredge samples were examined for 

 the benthic forms but only a few were found. In contrast, when the adults 

 moved into the surficial sediments in mid-August, the active animals could 

 be easily seen and picked out with a small scoop-net. However, on cloudy 

 and cool days they became inactive and could not be collected. To test the 

 estimates, three 2.25-m'^ circular chambers were constructed and their 

 edges pressed into the sediments on 3 July when the larvae were still 

 planktonic. In August, an average of 1.33 adults m"" were collected from 

 these enclosures, which is close to the 1 .3 given in Table 7-4. 



Lepidurus were sampled in three other bodies of water (Table 7-4) 

 and in the largest, North Meadow Lake, the animals were the most 

 abundant but smallest in size. The largest animals were found in a pond 

 even shallower and smaller than Pond A. It appeared that the animals in 

 North Meadow Lake were concentrated along the lee shore in small, 

 protected embayments. 



15 20 25 30 35 



Organism Totol Length, mm 



FIGURE 7-12. Number of eggs carried inter- 

 nally by Lepidurus of various lengths. 



