HgO 



AIR INPUT INFLOW poQD INPUT 



HgO OUTFLOW 



PETRIE DISH COVER 



SPRING 



WATER LEVEL 



GLASS OUTER SLEEVE 



GLASS INNER SLEEVE 



NYLON MESH 



SILASTIC TUBING 



CLAMP 



Figure 14-1. The 2 C Flow-Through Beaker System. 



NOTE: Designed by Dr. W. B. Vernberg under E.P.A. Grant R 802071 and 

 modified for use in the culture of larval and juvenile Palaemonetes vulgaris. 



All surviving juvenile P. vulgaris (about 140) were transferred on day 22 

 (post-hatch) to the 20 C "hatching jar" commonly used in hatching and 

 rearing larval fish (Figure 14-2). This 30 cm diameter, clear acrylic tank, was 

 modified from the manufacturer's design by placing a 400 )um nylon mesh 

 across the outflow ramp, thereby eliminating the need for a mesh over the top 

 of the entire system. This smaller outflow area effectively decreased the 

 chances of impinging larvae on the mesh. Gentle aeration and a water flow of 

 50 ml/min created a satisfactory circulation pattern. This hatching jar system 



^Midland Plastics Co., Brookfield, WI. 



208 



