degree of toxicity and is approved for food contact 

 applications and as an additive to some foods 

 (Smyth et al. 1970). Palaemonetes shrimp were 

 chosen for this study because of their importance 

 in estuarine food chains (Hedgpeth 1947; Welsh 

 1973), the ease with which their larvae may be 

 cultured in the laboratory, the general similarity 

 of their larvae to those of Macrobrachium shrimp 

 being evaluated for commercial culture, and the 

 known sensitivity of these carideans to a variety 

 of toxic agents (Lowe et al. 1971; Hansen et al. 

 1973; Redmann 1973; Sandifer and Shealy 1974^). 



Methods and Materials 



Two experiments were conducted with P. vul- 

 garis, one with P. pugio. Effects of three 

 polyethylene oxide concentrations (25, 50, and 100 

 wppm— weight parts per million) were tested ver- 

 sus controls in all experiments. Forty 

 Palaemonetes vulgaris larvae were reared at each 

 condition in experiments I (10 replicates of 4 

 animals each in 10.5-cm finger bowls) and II (4 

 replicates of 10 animals each in 19.1-cm bowls), 

 while 72 P. pugio zoeae (4 replicates of 18 each) 

 were maintained at each concentration in 

 experiment III. The P. pugio larvae were isolated 

 in compartments of covered plastic boxes. The 

 culture containers were placed in a Percival Model 

 I-35VL incubator* (Percival Manufacturing Co., 

 Boone, Iowa) where temperature was held at 

 approximately 25°C in experiment I and 28°C in 

 the subse quent trials. A 14-h light - 10-h dark 

 schedule was maintained in all studies. All animals 

 were transferred to clean containers with fresh, 

 filtered sea water (30°/ oo salinity) and fed newly 

 hatched nauplii of Artemia salina daily. 



Fresh stock solutions (200 wppm) of 

 polyethylene oxide (Polyox Coagulant, molecular 

 weight approximately 5x10^ [Union Carbide 

 Corp.]) in sea water were prepared every 3 or 4 

 days. Test solutions were prepared by diluting the 

 stock with appropriate volumes of seawater. 



Results and Discussion 

 Addition of small amounts of polyethylene oxide 



^Sandifer, P. A., and M. H. Shealy, Jr. 1974. Some effects of 

 mercury on survival and development of larval grass shrimp, 

 Palaemonetes vulgaris (Say). (Unpubl. manuscr.) 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA; NOAA Office of Sea 

 Grant; or the State of South Carolina. 



to the culture water significantly enhanced the 

 survival of grass shrimp larvae in static water 

 culture (Figure 1). The polymer affected neither 

 the number of molts to the postlarval stage nor the 

 size of postlarvae produced. However, a slight but 

 definite trend toward increasing development 

 time with increasing polyethylene oxide concen- 

 tration was apparent in all experiments (Table 1). 

 Stranding of larvae above the waterline on the 

 walls of the culture containers was a significant 

 cause of mortality in all control cultures, but addi- 

 tion of >25-wppm polyethylene oxide virtually 

 eliminated stranding deaths (Figure 1). This ef- 

 fect was probably the result of the reduced surface 

 tension and increased viscosity, lubricity, and 

 stringiness of the treatment solutions. Of course, 

 this type of effect would not be manifested in 



100 

 90- 

 80- 



70- 

 60- 

 50- 

 40 

 30 

 20- 

 10- 

 



i 



I I Survival to Postlarva 

 lijJH First Doy Mortolity 

 ^ Stranding Mortality 

 Other Mortality 



lOO-i 

 SO- 

 SO 

 70-1 

 60 



c 



S 50- 

 " 40 

 30-1 

 20 



25 50 100 

 Polyethylene Oxide 

 Concentratlon(wppm) 



b 



I 



25 50 100 

 Polyethylene Oxide 

 Concentration (wppm) 



100 

 90-1 

 80 

 70 

 60- 

 50- 

 40 

 30H 

 20 

 10 

 



I 



M. 



25 50 100 



Polyethylene Oxide 

 Concentration (wppm) 



Figure l.-Percentage survival and mortality of Palaemonetes 

 larvae reared in polymer and control solutions, (a) P. vulgaris 

 experiment I, (b) P. vulgaris experiment II, (c) P. pugio. 



679 



