WAKNEK: KKFKUUUCTIVE BIOLOGY OF PIMEWMETOPON PULCHRUM 



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 AGE (YEARS) 



Figure 3.-Mean standard length versus age in the Catalina 

 population of Pimelometopon pulchrum. Sample sizes are shown 

 for each interval, and 95% confidence limits for the mean are 

 drawn on either side of each point. Means for back-calculated 

 lengths are shown for comparison. 



is smaller and more variable than that from Cat- 

 alina, a marked tendency towards dwarfing is 

 clear. Judging from the mean lengths of each age 

 class, the Guadalupe California sheephead 

 complete their first year of growth at a standard 

 length about 20 mm shorter than those at Catalina. 

 For each of the next 3 yr they fall behind an addi- 

 tional 10 mm, after which relative growth slows 

 even more. By the eighth year, the mean standard 

 length of Guadalupe California sheephead is a full 

 100 mm less than that found at Catalina. 



In spite of the dwarfing, the Guadalupe popula- 

 tion shows some interesting parallels with Cat- 

 alina. The slowing of the average rate of growth 

 at the time of maturity (age four) is more striking 

 here, and growth appears to pick up again after 

 the sixth year, by which time at Guadalupe most 

 individuals are males (see below). This suggests 

 that an increase in the growth rate is associated 

 with sex changes, a topic covered more fully in the 



discussion. In the Catalina population, both the 

 increase in growth rate and the maximum number 

 of sex changes occur about a year later than in the 

 Guadalupe population. 



Anatomical Features of the Gonad 

 and Sexual Transformation 



The gonad of P. pulchrum consists of two hollow 

 sacs in the extreme dorsal part of the body cavity. 

 Grenital arteries and veins run through the dorsal 

 part of each lobe, giving off segmental branches. 

 The wall of each lobe consists of connective tissue 

 and smooth muscle. 



The internal structure is made up of germinal 

 epithelium in a series of folds or ridges, the 

 gonadal lamellae. These are numerous in the 

 female, but few in the male. There is a small 



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AGE (YEARS) 



Figure 4.— Mean standard length versus age in the Guadalupe 

 Island population of Pimelometopon pulchrum. Sample sizes are 

 shown for each age, and 95% confidence limits are drawn on 

 either side of each point. 



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