Long and Van Sant: Embryo development in golden king crab ( Lithodes aequispmus ) 
71 
0 100 200 300 400 500 
Days after extrusion 
Figure 2 
Average (among females) developmental stage of gold- 
en king crab ( Lithodes aequispinus) embryos plotted 
against days from extrusion, for each 10-day increment 
of embryo development. The line represents the best 
fitting multiple-stage transition model. Error bars indi- 
cate ±1 standard deviation of the mean. See Table 1 for 
parameter estimates. r 2 =coeficcient of determination. 
marked the midpoint in embryo development, beginning 
on day 213 and lasting for about 33 days (Table 1). 
Stage 9 (chromatophore formation) 
The beginning of this stage was marked by chro- 
matophores becoming visible in unstained embryos 
(Fig. II). Chromatophores increased in size and num- 
ber throughout this stage. Growth of the embryo and 
shrinking of the yolk accelerated from the previous 
stage (Figs. 3 and 4). The eyes grew rapidly, both in 
length and width. Because width increased much faster 
than length, the eyes progressed from a crescent shape 
to a nearly spherical one (Fig. 5B). From this stage on- 
ward in development, egg area began to increase as 
well (Fig. 3), although during this stage the increase 
was slight. The yolk became separated into 2 halves 
when the egg was viewed dorsally. This stage began on 
day 246 and lasted for 54 days. 
Stage 10 (rapid growth) 
This stage, which lasted about 41 days and began on 
day 300 (Table 1), was marked by a rapid increase in 
the size of the egg, embryo, and eyes, and a slight de- 
crease in the yolk area and percent area of yolk (Figs. 
3, 4, and 5). The shape of the eye did not change dur- 
ing this period and remained nearly spherical (Fig. 5B). 
When viewed on the sagittal plane, the yolk developed 
a partial anterior-posterior bifurcation (Fig. 1J). We 
marked the beginning of this stage with the beginning 
of this bifurcation and marked the completion of this 
stage with the completion of this bifurcation. 
Stage 1 1 (prehatching) 
At the beginning of this stage, the yolk was completely 
bifurcated (Fig. IK). Growth of the eye and embryo 
were at their maximum rates during this stage (Figs. 
3 and 5). Yolk area and percent area of yolk dropped 
rapidly, with the percent area of yolk dropping from 
70% to less than 50% (Fig. 4). The eyes continued to 
lengthen and increase in area, but the width did not 
Table 1 
Timing and duration of each stage of embryo development of golden king crab (Lithodes aequispinus). 
Mean values, with standard errors in parentheses, are provided for t$ o (the time in days at which 50% 
of the embryos transitioned to a given stage), and for s, a slope parameter for the transition to the next 
stage. Length is the average length (in days) of each stage, and -s/t^q is a measure of the rapidity of 
the transition to the next stage. 
Stage 
Description 
^50 (d) 
Length (d) 
s 
-s/t 50 
0 
Precleavage 
_ 
10.00 
-509.76 (SE 1660.70) 
50.98 
1 
Cleavage and blastula 
10.00 (SE 0.03) 
49.47 
-22.76 (SE 0.37) 
0.38 
2 
Gastrula 
59.47 (SE 0.20) 
32.02 
-278.22 (SE 71.06) 
3.04 
3 
V-shaped embryo 
91.49 (SE 0.16) 
23.53 
-31.24 (SE 3.74) 
0.27 
4 
Prenauplius 
115.02 (SE 1.35) 
27.18 
-42.08 (SE 2.39) 
0.30 
5 
Nauplius 
142.20 (SE 0.73) 
17.75 
-577.71 (SE 233.35) 
3.61 
6 
Maxilliped formation 
159.95 (SE 0.80) 
14.58 
2006.63 (SE 8853.47) 
11.50 
7 
Metanauplius 
174.53 (SE 6.47) 
38.18 
-314.76 (SE 27.35) 
1.48 
8 
Eye formation 
212.71 (SE 0.19) 
33.32 
-420.90 (SE 67.60) 
1.71 
9 
Chromatophore formation 
246.03 (SE 0.25) 
53.79 
-65.52 (SE 0.37) 
0.22 
10 
Rapid growth 
299.82 (SE 0.39) 
40.96 
-99.09 (SE 0.05) 
0.29 
11 
Prehatching 
340.78 (SE 0.29) 
95.25 
1266.33 (SE 36.33) 
2.90 
12 
Hatching 
436.03 (SE 0.08) 
25.67 
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