Lefebvre and Denson: Inshore spawning of Rachycentron canadum in South Carolina 
405 
Figure 3 
Micrographs of late-stage hatchery-reared cobia (Rachycentron canadum) eggs from the egg-development study 
conducted in 2008. Scale bars = 500 pm. (A) 21-hr-old eggs before preservation. IU=intact oil droplet (OD), 
unpigmented; IP=intact OD, pigmented. (B) The same eggs after 2 months in 10% neutral buffered formalin. 
OS = oil separating from pigmented portion; M = multiple OD. 
Table 3 
Descriptions of cobia ( Rachycentron canadum ) eggs from hatchery-reared eggs, eggs collected in plankton samples in 2008, and 
from Ditty (2006). Asterisks (*) indicate that only eggs with a single oil droplet were measured. 
Hatchery 
Plankton samples 
Parameter 
Live 
Preserved* 
Preserved* 
Literature 
Diameter 
1.21-1.38 mm 
(mean: 1.30 mm) 
1.18-1.37 mm 
(mean: 1.29 mm) 
1.15-1.39 mm 
(mean: 1.28 mm) 
1.15-1.42 mm 
(mean: 1.24 mm) 
Number of oil droplets 
1 
1 to several, often 
irregular in shape 
1 to several, often 
irregular in shape 
1 
Oil-droplet diameter 
0.34-0.42 mm 
(mean: 0.38 mm) 
0.32-0.42 mm 
(mean: 0.38 mm) 
0.28-0.42 mm 
(mean: 0.36 mm) 
0.34-0.65 mm 
(mean: 0.45 mm) 
Oil-droplet pigment 
present 
present; in some eggs, 
pigment separated 
from oil 
present; in some eggs, 
pigment separated 
from oil 
present 
Perivitelline space 
narrow 
narrow 
narrow 
narrow 
Embryonic pigment 
heavy, except on 
caudal peduncle 
heavy, except on 
caudal peduncle 
heavy, except on 
caudal peduncle 
heavy, except on 
caudal peduncle 
of the yolk. The embryo began to move, as evidenced 
by flexion of the body. Stage IV ended when the tail 
was visibly detached from the yolk and the embryo was 
approximately three-quarters the internal circumfer- 
ence of the egg. 
Stage V (21-29 hr; Fig. 4F): the embryo continued to 
become more heavily pigmented. More movement of the 
embryo was evident. The embryo was greater than 100% 
the internal circumference of the egg before hatching, 
with the tail extending beyond the head. 
