PERRIN ET AL.: GROWTH AND REPRODUCTION OF SPOTTED PORPOISE 



range of to 6 (Table 3). This number is tightly 

 correlated with the number of Type 1 corpora 

 (Figure 28), indicating that there may be some 

 overlap in the classification criteria for these 

 categories. 



Typed. Surface usually not raised; scar usually 

 smaller than Type 2 and heavily wrinkled. May 

 be pedunculate and flattened. May be flattened 

 against the surface or may run deep into the ova- 

 ry. Interior consists of white connective tissue. 

 May have yellow "stains" around the white 

 center. When many corpora are present, some of 

 this type may be present but not apparent at the 

 surface. Diameter 2.0 to 8.5 mm, average 3.5 mm. 

 This is a catch-all category for all small compact 

 corpora with surface scars and internal structure. 

 It probably includes both regressed corpora lutea 

 and corpora representing ovulation and other 

 events. We found 1,999 corpora of this type 

 (57.1% ). The number increases steadily with total 

 corpora number (Table 3, Figure 28), while the 

 numbers of Types 1 and 2 corpora remain con- 

 stant, indicating that Types 1 and 2 corpora re- 

 gress into and accumulate as Type 3 corpora. This 

 is assuming, of course, that total corpora count is 

 related to age (see below). 



Type 4. Thin, flattened against the surface of a 

 new corpus luteum. Two to 15 mm in diameter. 

 These are Types 2 and 3 corpora that cannot be 

 allocated to those categories because of distortion 

 caused by the corpus luteum. One hundred were 

 encountered (2.9%). 



Type 5. Surface trace very slight or apparently 

 absent. Interior deep yellow or orange, with no 

 concentrated connective tissue or apparent inter- 

 nal structure. Diameter 0.5 to 5.5 mm, average 2 

 mm. Harrison et al. (1972) have suggested that 

 this type of corpus is the end result of regression 

 of an atretic lutealized follicle. We encountered 

 149 (4.3%). 



Type 6. A small surface scar with no discernible 

 internal structure. Two to 5 mm in diameter. 

 Only 11 corpora of this type were encountered 

 (0.3%). They may represent extremely regressed 

 corpora of other types or may originate from dif- 

 ferent ovarian events. 



Types 1, 2, and 3 comprise a series of increasing 

 regression and/or decreasing complexity of origi- 



nal structure, and it is probable that regressing 

 corpora lutea pass through these types or stages. 

 The shapes of the diameter frequency distribu- 

 tions (Figure 29) suggest that corpora albicantia 

 regress to an average size of about 3 mm in 

 diameter and then persist and accumulate at that 

 size for at least part of the remainder of the life of 

 the female. The skewness of the aggregate dis- 

 tribution (sum Types 1, 2, and 3 in Figure 29) 

 becomes even more significant when one consid- 

 ers that the volume of the corpus decreases as the 

 cube of the diameter. On a volume scale, the left 



100 



TYPE I 

 (n=456) 



< 



100 



50 





 440 



T 400 

 0) 



E 



c 350 



300 - 



Q. 

 (T 



O 



O 250 



200 



150 - 



100 



50 



J\^ 



TYPE 2 

 (n=787) 



TYPE 3 

 (n = 1,999) 



5 10 



DIAMETER (mm) 



15 17 



Figure 29. — Frequency distribution of diameter of Types 1,2,3, 

 and 5 corpora albicantia in Stenella attenuata. 



255 



