DAILEY and PERRIN: HELMINTH PARASITES OF PORPOISES 



NEONATALS 



1 I I I I I ' ' ' I I I I I ' ' M ' I M ' ' M 



'EC: 



CALVES (2-1one) 



I I I I I I I I M 



-1=1. 



I I I I ' I ' I I ' I 



Q. lOi- 



5 



CO '*- 



o 



Q. 2 



tr 



2 



SUBADULTS (specKled, mottled, ond fused) 



I I I I I I I I I I I I I I I 



c^ 



I I I I I I I 



6- 

 4 - 

 2- 



ADULTS (mottled ond fused) 



I I ' I I I I I I I I I I I I I ' I ' ' 



JH 



80 1(30 120 140 160 180 260 220 



TOTAL LENGTH (cm) 



Figure 13. — Frequency distributions of total length, by 

 age class, of spotted porpoise, Stenella graffmani, in- 

 cluded in sample examined for parasites. 



of the parasite and/or to possibly differential 

 feeding habits of young and mature porpoise, 

 or heavily infected individuals die before at- 

 taining maturity. 



The case of the Crassicauda-\ike parasite in 

 the air sinuses of S. g raff ma in certainly pro- 

 vides the most dramatic instance of infection 

 varying with age. As stated above, the sinuses 

 were not searched during dissection of most 

 of the porpoise specimens, and only one speci- 

 men of the Crassicauda-iype was recovered. 

 Direct evidence, however, is provided of heavy 

 infection by the areas of bone erosion on the 

 lower surfaces of the skull (as illustrated in 

 Figure 8). Given this circumstance, we ex- 

 panded the series of porpoise specimens exam- 

 ined to include skeletal specimens in various 

 museum collections. In all, 129 skulls of spotted 

 porpoise from the eastern tropical Pacific were 

 examined (see Materials and Methods). Since 

 correlated data on size, reproductive condition, 

 and color pattern were not available for most 

 of the museum specimens examined, it was 

 necessary to use other criteria of age for those 

 specimens. The fetal and neonatal skulls exam- 

 ined were all from specimens we dissected. 



J I I L 



1 5 10 15 20 30 40 



^i- CALVES 



(62% infected) 



NEONATALS 

 (none infected) 



I I I I I I I I I 



50 60 



70 



4 - 

 2- 



J I L 



I I I I I I I I I I I 



— ®r 



o 



3 6- 

 to 



t- 4- 



co 

 o 



I 2- 



5 10 15 20 30 40 



SUBADULTS 

 (76% infected) 



50 



60 



70 







12 



10 

 8- 

 6 - 



J L 



in. 



I I I 



XZL 



5 10 15 20 



2- 



30 40 



ADULTS 

 (83% infected) 



50 



60 



70 



J I L 



J I I I I I I 1 1 i 1 



70 



1 5 10 15 20 30 40 



WORMS (no) 



50 60 



Figure 14. — Frequency distributions of levels of infec- 

 tion by Aiiisakis in four age classes of Sienelhi graffmani. 



Those of the remaining skulls that were mu- 

 seum specimens were relegated to the three 

 categories of calves, subadults, and adults by 

 criteria of cranial features, using the sample 

 of skulls from specimens we dissected to cor- 

 relate these features with total length, sexual 

 maturity, and color pattern. Museum skulls 

 were assigned to the calf class when in con- 

 dylobasal length, telescoping of facial elements, 

 and closure of occipital sutures, they had not 

 reached the adult condition. Skulls exhibiting 

 adult length, telescoping, and occipital closure 

 were divided into adults and subadults by the 

 criterion of presence or absence of distal fusion 

 of the premaxillary and maxillary bones of 

 the rostrum. Rough correlation of the onset 

 of fusion with attainment of sexual maturity 

 was found among the skulls from specimens 

 for which external data were also available 

 (Table 1. Errors in classifying subadult skulls 

 as adult and vice versa are approximately equal. 

 Results of examination of the 129 skulls for 

 bone damage (Table 2) demonstrate clearly that 

 the rate of infection is very much higher in 



465 



