FISHERY BULLETIN: VOL. 76. NO. 3 



Figure 19. — Ventral view of pelagic juvenile of Diodon holocanthus, 14.5 mm SL, Hawaiian waters 



(HIMB, uncataloged). Note pelagic spotting. 



clear, unornamented chorion. The diameter of the 

 live eggs is 1.7-1.8 mm {x = 1.74; SD = 0.03; 

 n = 16) and of preserved eggs is 1.6-1.8 mm 

 (X = 1.69; SD = 0.06; n - 191). These means are 

 significantly different at the 57( level (^-test) and a 

 shrinkage of about 49^ upon preservation in 5-10% 

 seawater-Formalin-'^ is indicated. Rearing experi- 

 ments indicate that the eggs are spawned in the 

 early evening and hatch in 4-5 days at about 25°C. 

 In rearing containers, the eggs sink to the bottom 

 12-24 h before hatching. 



Embryonic Development: The development of D. 

 holocanthus eggs is similar to that of Ranzania 

 laevis (see Leis 1977). Development is described 

 here with emphasis on differences between 

 these two species. 



Early stage (preclosure of blastopore, Figure 

 20). The earliest eggs collected were in mid- 

 gastrulation. The oil droplets are tightly clus- 

 tered opposite the embryonic axis. These 

 move with the germ ring to the caudal end of 

 the embryo by blastopore closure where they 

 subsequently start to disperse. The elapsed 

 time between midgastrulation and blastopore 

 closure is 3 h. Some segmentation can be per- 

 ceived on the embryo, but in general little 

 structure is evident. No pigment has formed. 



Middle stage ( blastopore closure to separation of 

 the tail bud from the yolk, Figure 21). The oil 

 droplets remain scattered over the caudal 

 one-fourth of the yolk sac. The eyes, heart, 

 brain lobes, and otic vesicles are formed 

 within 18 h of blastopore closure. The head is 

 broad and no pigment is visible. 



1.00 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Figure 20. — Early stage egg of Diodon holocanthus. After 

 Watson and Leis (1974), scale in millimeters. 



558 



