Biesiot et al.: Ovarian development in Rachycentron canadum 



691 



Biochemistry 



Biochemical analyses were performed on about one 

 third of the fish sampled for the histological study 

 (rc=43). Protein was the major biochemical compo- 

 nent (Fig. 5A), representing from 49 to 55% of the 

 ovary total dry weight (507.5-550.5 ug/mg dry 

 weight). There were no statistically significant dif- 





ferences in protein concentration among ovarian de- 

 velopmental stages (Kruskal-Wallis, a>0.05). 



Lipid concentration ranged from 209.3 to 412.5 ug/ 

 mg dry weight (21-41% dry weight) during ovarian 

 development, increasing from stage 1 through stage 

 3 (Fig. 5B). The increase was likely due to the for- 

 mation of lipid yolk during oocyte maturation. Lipid 

 concentrations then decreased after ovulation but not 

 to the low level of stage 1, probably reflecting the 

 residual lipid that had not been resorbed during 

 stage 4. The only statistically significant differ- 

 ence in lipid concentration during the course of 

 ovarian development was between stages 1 and 3 

 (Tukey-type multiple comparison test, a<0.05). 



Carbohydrate concentration was very low dur- 

 ing all stages of oogenesis in cobia, ranging from 

 27.2 to 45.2 ug/mg dry weight (3^% dry weight) 

 (Fig. 5C). It decreased from stage 1 to 2, increased 

 from stages 3 through 1', and declined slightly in 

 stage 2'. Almost all of the pairwise comparisons of 

 carbohydrate concentration were significant 

 (Tukey-type multiple comparison test, a<0.05) 

 except that stage 1 was not significantly different 

 from stages 4 and 2' nor was stage 2 significantly 

 different from stage 3. 



Ash concentration decreased from a high of 

 196.3 ug/mg dry weight to a low of 55.3 ug/mg dry 

 weight (6-20% dry weight) (Fig. 5D); it increased 

 in stage 4 and stage 1' but declined again in stage 

 2'. Stage-1 ash concentration was significantly 

 different from stages 3, 4, and 2'; whereas stage 2 

 was significantly different from stage 3 (Tukey- 

 type multiple comparison test, a<0.05). All of the 

 other pairwise comparisons were not significant. 



Discussion 



Protein was the major constituent of cobia ova- 

 ries and its contribution remained fairly constant 

 (49-55%) throughout all stages of gonadal devel- 



Figure 3 



(A) Stage-4 ovary, postovulation. Resorption of unspent 

 stage-3 oocytes (RO) into ovarian tissue (OT); oocytes 

 are distorted and compacted. There is residual lipid in 

 the resorbing oocytes. Stage-1' oocytes (St 1) occur. (B) 

 Stage-1' ovary, second previtellogenesis. Early previ- 

 tellogenic (EP), middle previtellogenic (MP), and late 

 previtellogenic (LP) stage-1' oocytes develop. Resorb- 

 ing oocyte (RO) and resorbing postovulatory follicle 

 (POF) are remnants from stage 4. (C) Stage-2' ovary, 

 second vitellogenesis (early). Formation of second round 

 of vitellogenic oocytes (St 2'). Note resorbing oocytes 

 (RO), postovulatory follicles (POF), and stage-1' oocytes 

 (St 1'). Scale bars=250 urn. 



