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Fishery Bulletin 105(1) 



Figure 3 



(A-El Microphotographs of postovulatory follicles (POFs) at consecutive phases of 

 deterioration in the Iberian sardine Sardina pilchardus, showing the degeneration 

 of POF size and shape, and the state of the granulosa (same scale for all images). 

 Scale bar = 0.1 mm. 



(P<0.001), indicating that POF resorption in the Iberian 

 sardine is not isometric, i.e., the shape of POFs changes 

 throughout degeneration. More specifically, b was esti- 

 mated to be 1.5 (standard error=0.13), indicating that 

 the diameter of POFs along the lamellar epithelium 

 diminishes at a lower rate than that for the overall 

 POF area. This allometric pattern of POF resorption 

 confirms the shape differences along POF degeneration 

 described above and shown in Figure 3. 



The differences in the dimensional characteristics 

 and the morphological state of the granulosa (Table 1) 

 were used to assign POFs from all surveys into four 

 daily classes. The reliability of these aging criteria was 

 confirmed by a very good relationship between POF 

 age and POF size in all years of the study (Table 2; 

 Fig. 5A). The rate of resorption, i.e., the relationship of 



0.01 - 



0.00 



0.05 



0.15 0.2 0.25 



POF diameter (mm) 



0.3 



Figure 4 



Allometric relationship between postovulatory follicle 

 (POF) diameter and POF cross-sectional area for the 

 Iberian sardine Sardina pilchardus. 



the slope of the POF cross-sectional area to POF age 

 was not found to differ significantly between the three 

 years, indicating that estimates of resorption rate are 

 not biased either by the preservation medium (AFA or 

 formalin) or by the embedding material (paraffin or 

 resin). In all study years, POFs were shown to shrink 

 exponentially with time in a way that their cross-sec- 

 tional area decreased daily by almost 50% (Fig. 5A). 



The relationship of the intercept of the POF cross- 

 sectional area on POF age in the GLM was similar for 

 the two preservation mediums (no significant difference 

 between 1997 and 2005), but differed significantly be- 

 tween the two embedding materials (significant differ- 

 ence between 1999 and the other two years) (Table 2). 

 POF area at any given time was significantly higher for 

 resin (Fig. 5A), indicating that processing in paraffin 

 wax leads to a higher shrinkage of all cellular struc- 

 tures in the gonad. This higher rate of shrinkage was 

 also evident by differences in the histological appear- 

 ance of POFs between the two embedding materials, 

 especially at earlier phases of degeneration (Fig. 6). The 

 structure of POFs in resin was more compact and the 

 cellular organization of the granulosa was clearly vis- 

 ible (Fig. 6A). On the other hand, in paraffin sections, 

 the cells of the granulosa layer were hardly detectable 

 and the follicular folds were usually detached from the 

 surrounding theca (Fig. 6B). 



During the entire survey period, sea surface tempera- 

 ture ranged between 11.6° and 19.3°C, and there were 

 marked interannual differences (2005 being the coldest 

 [mean SST: 14°C ±2.1] and 1997 being the warmest 

 year [mean SST: 16.2°C ±2.2°]). The fitted GLM showed 

 that ambient temperature had a significant effect on the 

 rate of POF degradation (Table 2; Fig. 5B). However, 

 this effect appeared to be limited because an increase 

 of 1°C in ambient temperature accelerated the rate of 

 POF resorption by only 3% (compared to the reduction 

 of POF area by almost 50% per day since spawning; 

 Table 2). This finding indicates that the maximum dif- 



