Hydroxyproline and backbone collagen were found to be sensitive bio- 

 chemical indicators of growth in fathead minnows exposed to toxaphen (Table 

 2). The correlation between hydroxyproline in backbone collagen and fish 

 weight was high, with a coefficient of determination (r?) of 0.982, and the 

 relation between collagen concentration and weight was even higher (r2, 

 0.990). Coefficients of determination were also relatively high for brook 

 trout and channel catfish. The measurement of hydroxyproline has some ad- 

 vantages over the measurement of collagen in that hydroxyproline can be 

 directly determined in eggs and whole fry, whereas collagen is determined 

 indirectly, except in fish large enough to permit analysis of the backbone 

 itself. The impact of toxicants on collagen and hydroxyproline metabolism 

 is probably greatest during early life stages of fish because the young fish 

 are generally more sensitive than older fish to toxicants, and have more 

 rapid developmental rates. However, in a preliminary study with the dime- 

 thylamine salt of 2,4-D and fathead minnows (Mayer and Mehrle, 1974), it was 

 found that hydroxyproline changed little in backbone collagen, but that col- 

 lagen itself decreased significantly (P<0.05). These results indicate that, 

 when possible, both hydroxyproline and collagen in backbone should be mea- 

 sured to facilitate toxicological interpretation. 



The use of collagen and hydroxyproline as predictors of growth effects 

 shows some promise, but has not been fully delineated (Table 3). The reduc- 

 tion of growth caused by toxaphene in brook trout occurred 23 to 30 days 

 after effects were observed in hydroxyproline content. In the first study 

 (Mehrle and Mayer, 1975a), the growth, and the collagen and hydroxyproline 

 concentrations in adult fathead minnows were significantly reduced (PO.05) 

 at all toxaphene concentrations. The hydroxyproline concentration in back- 

 bone collagen of adults was significantly reduced (P<0.05) in toxaphene con- 

 centrations as low as 54 ng/1 , whereas growth was significantly reduced only 

 in the 97 and 173 ng/1 exposures of a second study (Mayer zt al., 1977). In 

 the resulting fry, however, growth was more sensitive than hydroxyproline as 

 an indicator of the effects of toxaphene. Growth of channel catfish fry was 

 not reduced by toxaphene until 30 days after the eggs hatched, but the hy- 

 droxyproline content of eggs from exposed adults was significantly reduced 

 (P<0.05). The effects of toxaphene on hydroxyproline first appeared at ex- 

 posure concentrations of 72 ng/1, whereas effects on growth first appeared 

 at 299 ng/1. However, the reduction in hydroxyproline was related to bone 

 development, and numerous fish in the 72 through the 630 ng/1 exposures had 

 broken backs (Mayer e£al. t 1977; Mehrle and Mayer, 1976). Also, survival 

 was significantly reduced (P<0.05) in concentrations of 792 to 630 ng/1 and 



TABLE 2. RELATION BETWEEN BACKBONE DEVELOPMENT AND WEIGHT 

 IN FISH EXPOSED TO TOXAPHENE 



95 



