122 



Fishery Bulletin 104(1) 







N 



cl^^l*^^. 



*5> 



100 |jm E 



'- v>^l^li\- 



Figure 5 



Observations associated with Philometra saltatrix infection in bluefish (Pomatomus saltatrix) ovaries. 

 (A) Gross, bisected ovary from infected bluefish, showing heavy infection with Philometra (B) Low 

 power view of transverse section (approximately 1.5 cm in diameter) of heavily-infected bluefish ovary. 

 M=muscular capsule, F=ovarian follicles. W=nematodes in lumen of ovary, displacing oocytes. (C) 

 Histological section of healthy ovarian tissue showing dense packing of healthy oocytes in various 

 developmental stages, little connective tissue, and no cellular infiltrates. (D) Histological section of 

 infected bluefish ovary, showing relatively fewer oocytes (Ol and the presence oi Philometra (P). In 

 addition, there is severe interstitial hemorrhage (H) and necrosis (N) of ovarian tissue, with heavy 

 cellular infiltration and atresia (A) of ovarian follicles. 



and Philometra spp. (Williams and Jones, 1994), we 

 speculate that nematode larvae are released at spawn- 

 ing time, pass through the copepod intermediate stage, 

 and a second perhaps paratenic intermediate host (or 

 perhaps pass through only one intermediate host), and 

 infect YOY bluefish. It is important to note that most 

 YOY bluefish larger than approximately 40 mm TL 

 are piscivorous (Marks and Conover 1993); thus, it is 

 possible that the infected YOY bluefish observed in 

 this study were infected through a second intermedi- 

 ate host. The existence of a second intermediate fish 

 host is supported by the observed positive relationship 

 between host body size and parasite intensity. After ini- 

 tial infection, these worms reside in non-ovarian sites 

 such as the pericardial cavity (as we observed), where 

 they may remain quiescent until maturation of the host. 

 At that time, worms may migrate through the tissues 



to the ovary for spawning and the completion of their 

 life-cycle. This proposed life history would explain the 

 ontogenetic and seasonal patterns of worm distribution 

 that we observed and explain the rapid appearance of 

 well-developed worms in the ovary at the onset of the 

 spawning season. 



The prevalence and intensity of infections we ob- 

 served in bluefish were significantly higher than those 

 reported in most other fish species. For example, inten- 

 sity of infection in Glaucosoma hebraicum by Philometra 

 lateolabracis ranged from 1 to 7 nematodes (mean of 

 2 nematodes) (Hesp et al., 2002), whereas prevalence 

 of Philometra margolisi in the gonads of red grouper, 

 Epinephelus morio, ranged from 14 to 28% depending on 

 locality (Moravec et al., 1995) and prevalence of Philo- 

 metra lateolabracis in Parupeneus indicus was 5.3% 

 (intensity of 1-2 nematodes) (Moravec et al., 1988). 



