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Fishery Bulletin 1 14(1) 
shi, 1987) and the blue king crab (Stevens, 2006) have 
been described in detail, but little attention has been 
given to the golden king crab up to this point. It is 
likely that, given the asynchronous reproductive cycle 
and the lecithotrophic development of larvae, golden 
king crab embryos are substantially different from 
those of the other 2 species. The asynchronous cycle 
could lead to greater differences among females, and 
lecithotrophic larval development could result in differ- 
ences in embryo morphology, particularly in yolk size, 
at hatching. In this study, we examined and measured 
the embryos of golden king crab from time of extrusion 
though hatching and describe their development. 
Materials and methods 
Golden king crab were caught in commercial pots 
along the Aleutian Islands, Alaska, in the fall of 2005 
and 2006 and transported to the Kodiak Laboratory 
of the NOAA Alaska Fisheries Science Center in air 
cargo. Crab were identified according to the methods 
of Donaldson and Byersdorfer (2005). Crab were held 
in 2000-L tanks with flow-through seawater chilled 
to 3-4°C, a range that reflects the temperatures ex- 
perienced by female golden king crab in the Aleu- 
tian Islands (Blau et al., 1996; Stabeno et ah, 2005) 
and were fed chopped frozen fish and squid to excess. 
Tanks were covered with opaque sheets of foam both 
to provide insulation and to keep the females in most- 
ly dark conditions. 
Six females, 4 captured in 2005 and 2 caught in 
2006, were used in this study. Females were either 
late-stage ovigerous, as evinced by eyed embryos, or 
they were hatched out, as evinced by empty egg cases 
found when collected. They were between 120 and 141 
mm CL. Six mature males, 128-132 mm CL, were kept 
with pre-mating females in a holding tank because fe- 
males may molt and mate anywhere from 5 to 464 days 
after they finish hatching larvae (Paul and Paul, 2001). 
When pre-mating grasping occurred, a crab pair was 
moved to a separate tank to ensure that the female 
would not be eaten after molting. After the females 
molted, they mated and extruded a new clutch of eggs. 
At this point, they were placed in another tank where 
all the postmating females were held together with no 
males. The day of extrusion was considered day 1 of 
brooding and embryo development. 
Embryos were collected regularly throughout de- 
velopment from a random location within the clutch. 
Throughout development for each female, time be- 
tween samples varied with the stage of development 
but averaged once every 9 days or a mean of 48 times 
(range: 42-54 times). At sampling, embryos were ex- 
amined and photographed under a stereomicroscope. 
Uneyed embryos were stained for 5 min in Bouin’s so- 
lution to enable staging (Stevens, 2006). In addition, 
for image analysis, photographs were taken of up to 
10 unstained embryos at 90° to the sagittal plane un- 
der a stereomicroscope. These images were calibrated 
each day with a micrometer because the scope had 
an adjustable zoom and this calibration ensured that 
measurements were accurate. A total of 1241 embryos 
were measured. On a number of occasions, the cali- 
bration procedure was not followed, and we did not 
perform image analysis on the photographs, although 
stage data were still collected and used. Measure- 
ments were made with Image-Pro Plus 1 , vers. 7.0 (Me- 
dia Cybernetics Inc., Rockville, MD). 
In this study, the term egg refers to the entire em- 
bryo (i.e., the entire contents of the fertilized egg), the 
term embryo refers to the differentiated part of the egg 
as distinct from the yolk, and the term yolk refers to 
the undifferentiated deutoplasm. For each egg, the area 
and the mean, minimum, and maximum diameter were 
measured. The mean, minimum, and maximum diam- 
eters were determined from 180 measurements of the 
diameter at 2°-intervals around the entire egg. When 
the embryo became visible, the yolk area also was mea- 
sured by tracing the yolk in Image-Pro Plus, and the 
percentage of egg area that was yolk (hereafter percent 
area of yolk, calculated as yolk areax 100 /egg area; be- 
fore the embryo becomes visible, the yolk area equals 
the egg area) and the embryo area (calculated as egg 
area - yolk area) were determined. Finally, when the 
eyes became visible, the eye area and the mean, mini- 
mum, and maximum diameter were measured with 
same techniques as above. All measurements were 
made at 90° to the sagittal plane. 
Stages were described by visual examination of the 
eggs as well as on the basis of the changes observed in 
the measured parameters, and these descriptions were 
based, in part, on staging systems previously developed 
for embryos of the blue king crab (Stevens, 2006) and 
snow crab ( Chionoecetes opilio ) (Moriyasu and Lan- 
teigne, 1998). The median stage of development (see the 
Results section for descriptions) was determined for each 
female on each sampling day. The data for developmental 
stages were fitted to a model of multiple-transitions be- 
tween stages (MT model, Long, 2016). In brief, each stage 
transition was modeled as a logistic regression: 
.*50 , 
where t = the time in days; 
£50 = the time at which half of the embryos have 
transitioned to the next stage; and 
s = a parameter that is proportional to the slope 
at the transition. 
The data were fitted by using maximum like-lihood in 
R, vers. 2.14.0 (R Development Core Team., 2011). 
Morphometric analysis was used to visualize differ- 
ences among the developmental stages and to examine 
whether embryo measurements can be used to distin- 
1 Mention of trade names or commercial companies is for iden- 
tification purposes only and does not imply endorsement by 
the National Marine Fisheries Service, NOAA. 
