EFFECTS OF AIR EXPOSURE ON DESICCATION RATE, 



HEMOLYMPH CHEMISTRY, AND ESCAPE BEHAVIOR OF 



THE SPINY LOBSTER, PANULIRUS ARGUS 



Gregory K. Vermeer^ 



ABSTRACT 



Desiccation rates and hemolymph pH, lactic acid and ammonia concentrations of spiny lobsters, Panulirus 

 argus, exposed in air for up to 2 hours were measured. Desiccation rates were faster in smaller lobsters. 

 During a 2-hour exposure, hemolymph lactic acid levels increased more than 11 times, pH decreased 

 more than one-half unit, and ammonia concentrations nearly doubled. Ex-posure-induced changes in hemo- 

 IjTiiph parameters occurred most rapidly in the first 30 minutes and began to level off by 2 hours. Lobsters 

 exposed for 2 hours, then reimmersed for 24 hours, survived and had normal hemolymph chemical values. 

 However, 75% of the reimmersed spiny lobsters had a delayed or absent tail-flip escape response; most 

 individuals also exhibited diminished antennal defensive motions. Results suggest that desiccation and 

 hemolymph chemical changes, caused by exposure, do not directly cause mortality, but rather induce 

 secondary physiological damage, manifested as aberrant defensive and escape behavior. 



The South Florida fishery for spiny lobster, Panu- 

 lirus argus (Latreille, 1804), uses sublegal (<76 mm 

 carapace length, CL) lobsters, locally called shorts, 

 as living attractants in traps for legal-sized lobsters. 

 Shorts used in this manner are customarily held in 

 wooden boxes on deck until replaced in traps. Aerial 

 exposure ranges from a few minutes to several 

 hours but is typically about 1 h (Bill Moore-). Hunt 

 et al. (1986) reported an average 26.3% mortality 

 rate after 4 wk for lobsters that had been exposed 

 between V2 and 4 h and estimated that 600,000 to 

 3.7 million shorts die annually as a result of handling 

 and exposure. Because this mortality is incurred by 

 sublegal lobsters which otherwise would soon con- 

 tribute to legal harvest, economic loss to the fishery 

 is considerable, perhaps as high as $9.0 million 

 annually. 



This study examines desiccation rate, hemolymph 

 chemistry, and escape behavior of spiny lobster to 

 document physiological and behavioral changes in- 

 duced by air exposure. The relationship between 

 these changes and mortality is discussed. 



MATERIALS AND METHODS 



One hundred seventy intermolt spiny lobsters, 

 averaging 80.2 mm CL (range, 56.7-120.7 mm), 

 were collected from traps at the Atlantic reefs south 



'Florida Department of Natural Resources, Bureau of Marine 



Research, 100 Eighth Avenue S.E., St. Petersburg, FL 33701. 



^Bill Moore, lobster fisherman, pers. commun. December 1984. 



of Marathon, FL, in the Florida Keys. Approximate- 

 ly 26 lobsters at one time were allowed to acclimate 

 for a minimum of 2 d in a 800 L (179 x 76 x 60 

 cm) outdoor fiberglass tank. The tank was fully 

 shaded by three plywood sections which could be 

 removed individually, allowing easy access while 

 minimizing disturbance. Flow-through water circula- 

 tion was maintained by a pump drawing approx- 

 imately 3,600 L/hour from a clean, well-oxygenated 

 canal. Complete water exchange occurred every 15 

 min. Periodic canal water samples had oxygen con- 

 centrations of 5-7 ppm and no detectable ammonia 

 or lactic acid. There were resident spiny lobsters in 

 the canal. 



Shelter inside the tank was provided by a double 

 layer of two-hole cinder blocks (39.5 x 19.5 x 19.5 

 cm) centered and aligned parallel to the long axis 

 of the tank. This arrangement of blocks allowed for 

 easy removal of spiny lobsters by the antenna-tug 

 technique, described later. In rare instances when 

 a spiny lobster evaded capture on the first attempt, 

 sampling of that animal was postponed for at least 

 24 h. This was necessary because repeated tail- 

 flips depressed hemolymph pH (unpubl. data). 

 Spiny lobsters were not fed during confinement 

 or held longer than 10 d. Both sexes were used 

 equally. 



Desiccation Rate 



Spiny lobsters were randomly selected from the 

 acclimation tank at 10 min intervals, marked for in- 



Manuscript accepted September 1986. 

 FISHERY BULLETIN: VOL. 8.5, NO. 1, 1987. 



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