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Fishery Bulletin 115(1) 
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Figure 3 
Histological sections (B-pm thickness), stained with 
Masson’s trichrome, of the eyestalk of a spot shrimp 
(Pandalus platyceros) collected in Alaska in 2014, show- 
ing (A) the entire eyestalk and (B) the cuticular layer- 
ing, as seen in the inset in the smaller, lower small 
box in panel A, including the epicuticle (Ep), exocuticle 
(Ex), endocuticle (En), and membranous layer (Ml). The 
larger box indicates the location within the structure 
where growth bands were observed in Figure 4C. 
terization of the mesocardiac ossicles of the crab spe- 
cies and of the eyestalk of the spot shrimp defined the 
boundaries between cuticular layers — boundaries that 
are critical for developing band counting criteria. As 
with results from studies of other species (e.g., Kilada 
et ah, 2012; Leland et ah, 2015), there was prelimi- 
nary evidence that a portion of the mesocardiac ossicle, 
where band patterns are observed in the endocuticle, is 
either retained or replaced during molting. A structure 
that is retained through ecdysis would be useful for 
evaluating band information. 
The cuticle layers of the mesocardiac ossicles of red 
king and southern Tanner crabs and the eyestalks of 
spot shrimp were similar to those observed in other 
studies of decapod crustaceans (see Roer and Dillaman, 
1984, and references therein; Vatcher et ah, 2015). 
Differences in staining results may be due to differ- 
ences in the specific calcium compound involved in the 
biomineralization within each region (Vatcher et al., 
2015). As in results for blue crab (Callinectes sapidus) 
with the use of acridine orange (a different histological 
stain) (Vatcher et ah, 2015), the medial tooth of the 
urocardiac stained similarly and was continuously con- 
nected to the epicuticle in both crab species examined 
in this study (Fig. 2A). This result further supports the 
hypothesis that the hardened cusp of the tooth is of 
epicuticular rather than exocuticular origin (Vatcher et 
ah, 2015). 
Bipartite patterns were readily visible in the me- 
socardiac ossicles of red king and southern Tanner 
crabs and in the eyestalks of spot shrimp. Recurrence 
of this pattern in multiple individuals indicates that 
band counts may be promising as indicators of growth 
variability through the lifetime of these species. Before 
this experiment, bands were observed in eyestalks of 
snow crab (C. opilio), which is a congener of the south- 
ern Tanner crab (Kilada et ah, 2012). We evaluated the 
mesocardiac of the southern Tanner crab because of the 
possibility that this structure may be retained through 
ecdysis (Kilada et al., 2012; Leland et ah, 2015; but 
also see Vatcher et al., 2015). To our knowledge, de- 
scription of growth bands in red king crabs is a first for 
the family Lithodidae. The appearance of bands in spot 
shrimp was very similar to that observed in the eye- 
stalks of a congener, the northern shrimp (P. borealis) 
(Kilada et al., 2012). Finally, most notably for the red 
king crab, a high proportion of the structures evaluated 
for growth bands were damaged during embedding or 
preparing thin sections. Structures were, by necessity, 
shipped dry before they were embedded in resin, and 
this condition likely contributed to their fragility and 
high fracture rate during the embedding and sectioning 
processes. Embedding structures before shipping could 
effectively mitigate this problem. 
The absence of the basal region of the mesocardiac 
(where band patterns are observed in thin sections) in 
exuviae of southern Tanner and red king crabs indicat- 
ed that this portion of the ossicle was either retained or 
replaced within 1 week after molting (Fig. 5, A and C). 
Recently it has been hypothesized that the endocuticle 
region of the pterocardiac and mesocardiac ossicles is 
retained through molting (Kilada et al., 2012; Leland et 
al., 2015). Calcein marks in the endocuticle were visi- 
ble after several molts and portions of the ossicles were 
absent in the exuviae of lobster and crayfish species. 
However, for the blue crab, histological characteriza- 
tion of the cuticular layers of the dorsal ossicle (dor- 
somedial tooth) indicated that the dorsal cuticle (Roer 
and Dillaman, 1984), like the endocuticle, is resorbed 
during the premolt stage and resynthesized during the 
postmolt stage (Vatcher et al., 2015). As with brachy- 
uran crabs (Brosing, 2014), the gastric teeth differed 
