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



53 



100- 



80- 



60- 



40- 



20- 



100- 



80- 



60- 



40- 



20- 



-I — I — I — r- 



-2.1 °h 



o - earoao BO 



T — I — I — I — I — I — I — I — I — I — I — I — I — I — I — I — T 



100 



~r 



110 



r 



120 



T 

 130 



100 



1 I ' ' 

 110 



T" 1 " 

 120 



Julian day 



-4.3 "h 



-4.9 °h 



130 



Figure 9 



Zoeal production (number of zoeae per gram female Chionoecetes bairdi) 

 as a function of time. Curves were fit with smoothing techniques (4253HI 

 (Velleman and Hoaglin, 1981). Units are in °h. 



sence of weight changes in the adults is puzzling 

 because feeding rates were significantly depressed 

 by exposure. Growth of adult western rock lobsters 

 was reduced by exposure (Brown and Caputi, 1985). 

 Body size, shape, and volume may be important 

 factors in predicting crab response to cold-air expo- 

 sure. Results of the present experiment support this 

 hypothesis: smaller crabs (juveniles) were more sen- 

 sitive to exposure than were larger crabs (adults). 

 Additionally, adult Tanner crabs were more sensi- 

 tive to exposure than were larger king crabs (Carls 

 and O'Clair, 1990), but unknown interspecific fac- 

 tors may have influenced this difference. An experi- 

 ment involving a broad size range of conspecific in- 

 dividuals is needed to test whether sensitivity to ex- 

 posure is size-dependent in crabs. 



Surprisingly, aerial exposure did not measurably af- 

 fect the developing larvae of exposed females unless 

 the female died. Surviving crabs produced normal 

 zoeae. Moreover, the timing of larval release, larval 

 swimming ability, and viability were not affected by 

 exposure. Longer-term larval responses, such as sur- 

 vival past the first molt and zoeal growth, were not 

 examined. Exposure may have reduced hatching suc- 

 cess (by <1%) of the Tanner crab larvae and possibly 

 may have affected the timing of egg extrusion, but these 

 responses did not vary strongly. Schlieder (1980) re- 

 ported a 13% reduction in hatching success in the stone 

 crab, Menippe mercenaria, compared with controls 

 when the crabs were exposed to air at 27-33°C for two 

 hours. Hatching success was reduced further by a five- 

 hour exposure and by autospasy (Schlieder, 1980). 



