Kilada et al.: An age-determination method for 3 commercially important crustaceans 
47 
Figure 4 
Bipartite growth band patterns in the endocuticle of the arch of the mesocardiac ossicle of the 
gastric mill (for reference, see Fig. 2) of (A) a red king crab (Paralithodes camtschaticus) collected 
in Bristol Bay, Alaska, in June 2013; (B) a southern Tanner crab (Chionoecetes bairdi) collected in 
Marmot Bay, Alaska, in June 2014; and (C) in the proximal portion of the eyestalk of a spot shrimp 
{Pandalus platyceros) collected in Seymour Canal, Alaska, in May 2014, all under transmitted light. 
The endocuticle (En), exocuticle, (Ex), and membranous layer (Ml) are labeled for orientation. 
in biomineralization from other portions of the gastric 
mill (Vatcher et al., 2015) and remained in the exuviae 
of both crab species examined in this study. 
Our results are an initial step toward developing 
and further evaluating growth bands as a possible in- 
dicator of age for commercially valuable crustaceans in 
Alaska. Key areas for further research include evalua- 
tions of variability (precision) in band count and clar- 
ity among the primary ossicles (pterocardiac, zygocar- 
diac, and mesocardiac) of the gastric mill (Leland et 
al., 2011; Leland et al., 2015; Sheridan et al., 2015), 
innovation in preparation techniques for thin sections 
(Sheridan et ah, 2015), definitions of criteria for iden- 
tifying bands (e.g., Leland et al. 2015), determination 
of the fate (retention or replacement) of the endocuticle 
during molting (Vatcher et ah, 2015), and corroboration 
of band counts with current understanding of species- 
specific growth, life history, and longevity based on in- 
direct methods. Ultimately, hypotheses should also be 
developed regarding the mechanism by which growth 
bands are formed and retained in structures that are 
molted (shrimp eyestalk) or possibly retained (e.g., gas- 
tric mill ossicles) (Kilada et ah, 2012; Leland et ah, 
2015; Vatcher et ah, 2015). 
Rigorous validation of bands as indices of age will 
also be necessary before their application in stock 
assessment and fisheries management (Beamish 
and McFarlane, 1983; Campana, 2001; Leland et ah, 
2011). Validation techniques potentially applicable to 
the species investigated in this study include the use 
of autofluorescent stains and the use of specimens 
with known ages. Autofluorescent stains, such as cal- 
cein, can create discrete marks in calcified hard parts 
that can be used to examine band deposition with 
