Carls and O'Clair Responses of Chionoecetes bairdi to cold air 



49 



to cold air frequently lost pereiopods during ecdysis; 

 losses increased from to — 4°h. The only crab ex- 

 posed to -8°h that attempted to molt lost no limbs, 

 but died during ecdysis (Fig. 6). 



Feeding rates 



Feeding rates of adult female Tanner crabs were sig- 

 nificantly depressed by exposure to cold air 

 (P ANOVA <0.001). In general, adult females exposed to 

 <— 2.7°h (62% of the median lethal exposure) ate sig- 

 nificantly less than did controls (Tukey test). Feed- 

 ing rates measured shortly before zoeal hatching (41 

 to 60 days after exposure) were significantly less 

 (P<0.05) for all crabs than feeding rates after zoeal 

 hatching (85-98 days after exposure), but the slopes 

 (feeding rate/exposure) before and after hatching did 

 not differ (multivariate regression, P>0.50; Fig. 7). 

 The frequency of feeding also increased significantly 

 after zoeal hatching (P<0.001) and was significantly 

 related to aerial exposure before and after larval 

 hatching (P /mrar <0.001). The most severely treated 

 crabs (-4.9°h) did not eat before zoeal release but 

 ate 57% of the time after release. 



Weight change 



Change in weight of juvenile crabs was reduced by 

 exposure to cold air. Wet weights of juvenile crabs 

 that did not molt declined with increasing exposure 

 severity (P=0.002, r 2 =0.42, n=20; Fig. 8). The weight 



increment of juvenile crabs that molted also declined 

 with decreasing exposure (Fig. 8). This trend was not 

 significant until an outlier at -2.0°h was removed 

 (P=0.021, r 2 =0.56, n=9). Pereiopod autotomy prob- 

 ably influenced these weight outcomes. The weight 

 changes of juvenile crabs that did not molt were cor- 

 related with righting response measured immedi- 

 ately after exposure (P=0.018, r 2 =0.88, «=5, Y=a + 

 bx 3 ). Changes in weight of adult crabs were not cor- 

 related with exposure (P>0.07, r 2 =0.08, rc=44). 



Reproduction 



Exposure of ovigerous female crabs to cold air gen- 

 erally did not affect the eggs or subsequently released 

 zoeae unless the female died; all eggs died if the fe- 

 male died. Timing of initial zoeal release (20 April ± 

 1 day), duration of release (11+1 day), and median 

 release date (26 April ± 1 day) did not vary with ex- 

 posure (r 2 =0.04, n=44; Fig. 9). Zoeae placed in sepa- 

 rate containers for two days were not significantly 

 affected by exposure prior to hatching (P=0.425, 

 r 2 =0.02, «=43), and 87 ±3% continued swimming 

 through the test period. Larval mortality, measured 

 as the percentage of zoeae that sank to tank bottoms 

 and died (0.4 ±0.2%), did not vary with exposure 

 (^=0.03, n=44). Zoeal mortality (2 ±2%) during swim- 

 ming tests was not correlated with exposure (r 2 =0.09). 



