FISHERY BULLETIN: VOL. 78, NO, 2 



Table l. — Reproductive data on female spinner dolphin stranded in Florida. Epiphyses: = open; 1 = closed; 2 = fused. 

 Sexual maturity: = mature; 1 = maturing; 2 ^ mature. Ages are in number of dentinal growth layer groups with + 

 signifying that the pulp cavity was closed and the age was greater than the number of visible groups. The right and left ovaries 

 were confused on 504437. However, they are presumed to correspond to the relative diameter of the uterine horns. 



though sample size is small, it gives a useful pre- 

 liminary estimate of age at sexual maturity of 

 7-10 growth layer groups (7-10 yr, seePerrin etal. 

 1976, 1977 for discussion of alternative growth 

 layer-age relationships). 



Comparable figures were given by Perrin et al. 

 (1977) for the eastern spinner dolphin from the 

 Pacific. They found a mean length at sexual 

 maturity of 165 cm which is appreciably shorter 

 than the estimate for this sample ( 188 cm). This is 

 due at least in part to the eastern spinner dolphin 

 being a relatively smaller animal (mean length of 

 sexually mature females was 171 cm, whereas it 

 was 197 cm for this sample). Perrin et al. (1977) 

 found that mean age at sexual maturity was 5.5 

 growth layer groups, which may represent a de- 

 crease in age at sexual maturity as a result of 

 fishing pressure on the eastern spinner popula- 

 tion. This also might contribute to the shorter 

 length at sexual maturity in that population. 



As appears to be the case with many delphinids, 

 there was a marked dominance of the left side of 

 the reproductive tract (Harrison et al. 1972). In all 



of the mature or maturing animals, the left ovary 

 was decidedly larger than the right, and only one 

 animal (504441) bore any externally visible cor- 

 pora on the right ovary. There was a correspond- 

 ing asymmetry in the size of the uterine horns, 

 with the left being equal to or larger than the right 

 in all but one animal (504444), indicating that the 

 greater number of pregnancies were carried in the 

 left horn. 



The testes were measured, weighed with the 

 epididymis removed, and a sample taken for his- 

 tological examination. Sections of testis samples 

 were cut at 10 /xm, stained with hematoxylin and 

 eosin, and the diameter of the seminiferous 

 tubules measured with an ocular micrometer. The 

 tubules were randomly selected for examination, 

 but only those approaching a direct rather than an 

 oblique cross section and free from obvious ar- 

 tifacts of sectioning or decomposition were chosen 

 for measurement. The least diameter was mea- 

 sured and the results given in Table 2 are the 

 mean of 10 tubules, at a depth of about 1 cm from 

 the surface of the testis. Tubules were also mea- 



TABLE 2. — Reproductive data on male spinner dolphin stranded in Florida. Epiphyses: = open; 1 = closed; 2 = fused. Sperm in 

 epididymis: = none; 1= present; 2= copious. Testis activity: = no spermatogenesis; 2 = active spermatogenesis. Sexual maturity: = 

 immature; 1 = maturing; 2 = mature. Ages are in number of dentinal growth layer groups, with + signifying that the pulp cavity was 

 closed and the age was greater than the number of visible layers. 



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