STRl'HSAKKR: EFFECTS OF BENZENE ON SPAWNING HERRING 



significant difference (P>0.25) between con- 

 centrations or days or interaction was found. Tests 

 between slopes (b) and elevations (a) of the re- 

 gression lines of weights on lengths of females and 

 weights on lengths of ovaries (Snedecor and 

 Cochran 1967:432-436) showed no significant 

 differences (P>0.10) between and 800 ppb 

 concentrations (Table 2). 



Microscopic examination of the ovaries, 

 however, revealed the presence of dead eggs in 

 ovaries of exposed fish by the second day of expo- 

 sure (Table 1). No dead eggs were found in control 

 fish until day 4, and then only a few (15-20 eggs) in 

 one female, the rest of the ovary appearing nor- 

 mal. Ovaries of exposed fish contained sig- 

 nificantly larger numbers of opaque dead eggs 

 (more than 10%) and were generally paler yellow 

 and deliquescent. By the end of 6 days, 67% (100 

 ppb) and 54% (800 ppb) of exposed females were 

 found with ovaries containing dead or dying eggs. 



The uptake and depuration of benzene in 

 ovaries of females exposed to a static initial 

 concentration of 100 nl/liter (ppb) 14 C-labeled 

 benzene is shown in Figure 1, together with data 

 determined from other larval studies for later 

 stages (Eldridge, Struhsaker, and Echeverria 5 ). 

 Uptake was rapid, so that a maximum accumu- 

 lation (1.4 /u.l/g; ppm) was reached in 24 h. This 

 level was maintained through the 48-h exposure 

 period. After open flow was reestablished and 

 exposure ended, benzene and/or metabolites were 

 depurated until they reached an undetectable 

 level in 96 h. The figure shows that levels ac- 

 cumulated in ovarian eggs were higher and 

 sustained longer than in later egg and larval 

 stages from other experiments with comparable 

 exposure conditions. 



Results of rearing experiments with eggs from 

 females exposed to and 800 ppb unlabeled 

 benzene are summarized in Tables 4 and 5. 

 Survival was also reduced in eggs and larvae from 

 females exposed to an initial concentration of 100 

 ppb labeled benzene. However, results were 

 obscured by an additional variable. Eggs taken 

 from the static exposure tank were covered by 

 filamentous bacterial growth early in develop- 

 ment and many eggs died as a result. In the other 

 treatment with open flow and in controls, eggs did 

 not undergo this mortality due to epifloral growth. 



i.o 



09 



Q- 8 



Cl 



^ 7 



3. 



~ 06 

 oj 



6 



5 05 



o 



0) 



to 



3 04 

 Cl 

 a. 



O 03 

 O 



E 

 o 



f 0.2 



Q. 



3 



c 



(V 



CD 



Eggs In Ovary 



6 12 18 24 



48 



Time (h) 



72 



96 



s Eldridge, M. B., J. W. Struhsaker, and T. Echeverria. 

 Manuscr. in prep. The uptake, accumulation and depuration of 

 14 C-labeled benzene in embryos and larvae of Pacific herring 

 (Clupea harengus pallasi). 



FIGURE 1. — Accumulation of 14 C-labeled benzene in different 

 early Pacific herring developmental stages exposed to an initial 

 concentration of 100 nl/liter (ppb) in a static system. Concentra- 

 tions shown on y-axis were calculated from total radioactivity 

 and may include metabolites derived from benzene as well as 

 benzene. Spawned eggs were in a stage just prior to blastopore 

 closure; post yolk-sac larvae were fed the rotifer, Brachionus 

 plicatilis, containing high accumulated levels of labeled ben- 

 zene. ND = not detectable. 



The 100 ppb treatment, therefore, was not in- 

 cluded in the analysis. Analysis of variance 

 showed survival at hatching and survival of lar- 

 vae through yolk absorption were significantly 

 less in exposed eggs (800 ppb) than in control eggs 

 (P<0.1; Table 5). Exposure to ppb benzene levels 

 for only 48 h reduced survival by about 43% 

 through yolk absorption to larval day 7 (Table 4). 



DISCUSSION 



When female herring were briefly exposed to 

 low levels of benzene for 48 h just prior to 

 spawning, a significant reduction occurred in 

 survival of eggs and resultant larvae from the 

 ovary through yolk absorption. It is probable that 

 further mortality would have occurred in later 

 larval stages if the experiments were continued. 

 When this result is compared with that from 

 exposing other life history stages after spawning 

 (Struhsaker et al. 1974; Eldridge et al. see footnote 

 5) where survival is not affected except at ppm 

 levels, it appears that the spawning female and 

 ovarian eggs are the most sensitive stages. 



47 



