VALENTINE and SOU LE: EFFECT OF p. p'-DDT ON GRUNION 



specimens were placed in a 10% Formalin^ solu- 

 tion. The fish died with their pectoral fins 

 spread. After a minimum of 24 h in the fixative, 

 specimens were rinsed in fresh water and stained 

 for several hours in a 5% KOH-alizarin red solu- 

 tion. Pectoral fin rays were scored using a bino- 

 cular dissecting microscope. The standard length 

 of each specimen was determined by placing 

 individuals on a flat plastic ruler. 



We have chosen to use the variance, V^, of the 

 right (/?) minus left (L) values to quantify the 

 amount of asymmetry. This statistic is simply 

 !,((} - d)-IN - 1, where d is an individual's asym- 

 metry (right minus left value), d is the mean of 

 the asymmetry distribution, and A^ is the sample 

 size. In our previous paper we used a similar 

 statistic, the squared coefficient of asymmetry 

 variation. 



where the scale correction, x^ + j^^ is the mean 

 value of the character itself. In contrast to the 

 earlier study, we found that the amount of asym- 

 metry was uncorrelated with the mean character 

 state, probably because the fins of the grunion in 

 this study were still developing. Even though 



'* Reference to trade names does not imply endorsement 

 by the National Marine Fisheries Service, NOAA. 



smaller grunion fry had fewer fin rays, they 

 were not less asymmetrical in an absolute sense. 

 The use of CV'^ would, in fact, give misleading 

 results. For example, examination of Table 1 will 

 show that fry in untreated tanks have pectoral 

 fin ray means varying from a low of 13.491 

 (Control) to a high of 23.220 (Del Mar). The Vq 

 values are 0.554 and 0.596, respectively. The 

 corresponding CV^ values are 30.5 and 11.0. 



RESULTS 



One-half of the replicates were killed at 38 

 days after hatching because we were uncertain 

 how long the fry would live. The remaining 

 replicates were terminated 51 days after hatch- 

 ing. This latter time period was chosen because 

 examination of grunion fry from Bahia San 

 Quintin at that age (this experiment was started 

 2 wk before the others) indicated that the num- 

 ber of pectoral fin rays was near the same mean 

 as was found in wild adults. Mortality, due to an 

 unknown cause, was also reducing the numbers 

 of fry in some tanks. The 38-day experiments 

 were terminated too early to yield useful data 

 as many fish had not yet begun to develop ossi- 

 fied pectoral fin rays. 



Grunion fry receiving the largest dose of p, p'- 

 DDT, 500 ppb. began showing signs of neuro- 

 muscular dysfunction the day after the experi- 



TablE 1. — Grunion statistical information. 



Asymmetry variance. 



Control for the flowing water experiments. 



923 



