NOTES 



HEART AND GILL VENTILATORY ACTIVITY IN 



THE LOBSTER, HOMARUS AMERICANUS, AT 



VARIOUS TEMPERATURES 



Heart rate and gill ventilatory activity have been 

 suggested as useful measures of the physiological 

 condition of decapod crustaceans and their re- 

 sponse to various environmental conditions. Sev- 

 eral authors have described altered ventilatory 

 and heart rates in response to such variables as 

 temperature, salinity, and dissolved oxygen 

 (Uglow 1973; Cumberlidge and Uglow 1977; Tay- 

 lor 1977; Hagerman and Uglow 1979). Price and 

 Uglow (1980) also discussed the applicability of 

 these measures in studies of pollutant stress 

 where they described the effects of copper, cad- 

 mium, and zinc on the heart and ventilatory rates 

 of Crangon crangon . The mechanics of ventila- 

 tory reversals of decapod crustaceans have also 

 been described; for example, the reverse ventila- 

 tory pulses (coughs) produced by the American 

 lobster, Homarus americanus , during a muscular 

 compression of the branchial chamber probably 

 provide irrigation to the posterior area of the gills 

 or help to clear detritus from gill surfaces 

 (Wilkins and McMahon 1972; Bill and Thurberg 

 1985). The frequency of the lobster cough re- 

 sponse increases after exposure to a variety of 

 waterborne chemicals, and it has been suggested 

 that this response might be a useful measure for 

 detecting aquatic pollutants (Bill and Thurberg 

 1983, 19851. Before these heart and ventilatory 

 measures can be employed as monitoring tools, 

 however, baseline information should be collected 

 on their seasonal variability under normal, un- 

 polluted conditions, against which to interpret 

 any stress-induced change. This study addresses 

 the relationship between heart, gill-bailer, cough 

 rate, and seasonal water temperature. 



Methods 



Adult American lobsters (61.4-91.2 cm cara- 

 pace length) were trawl-collected in Long Island 

 Sound off Milford, CT, and held in running sea- 

 water at ambient temperature. Seawater for this 

 building is taken from Milford Harbor, a harbor 

 with good tidal flushing and no industrial devel- 

 opment. The pollutant content here is very low; 



for example, seawater cadmium is <0.5 ppb, mer- 

 cury <1 ppb, lead <5 ppb, and copper 2-4 ppb. The 

 PCB levels (0.67 ppm, wet weight) in blue mus- 

 sels, Mytilus edulis, from Milford Harbor are typ- 

 ical of levels found in molluscs along the U.S. east 

 coast (Farrington et al. 1983; Greig and Sen- 

 nefelder 1985). Although no area of Long Island 

 Sound can be considered "pristine", this area has 

 excellent water quality for holding and rearing 

 marine animals as evidenced by a 50-yr labora- 

 tory history of marine invertebrate culture. The 

 salinity range is 26-28 ppt with occasional brief 

 low salinity episodes during extreme rains (not 

 during this study, however) and the dissolved 

 oxygen levels remain at or near saturation at the 

 temperatures in this study. The lobsters were fed 

 chopped clams, fish, or crabs daily. Heart, gill- 

 bailer, and cough rates were monitored with 

 6 mm silver disc electrodes, an impedance con- 

 verter, and an amplified polygraph recorder, fol- 

 lowing the methods described in Bill and 

 Thurberg (1985). Measurements were made at 2°, 

 6°, 10°, 14°, and 18°C over a 1-yr period. Each 

 lobster was allowed to acclimate to temperature 

 for at least 2 weeks befoi'e testing. Between 9 and 

 23 lobsters were monitored at each temperature 

 for a 1-h period. Rates were calculated on a per- 

 minute basis. 



Results and Discussion 



Crustacean metabolism varies with tempera- 

 ture (Wolvekamp and Waterman 1960; Taylor et 

 al. 1977, 1973). Aiken (1980) observed that ele- 

 vated temperatures accelerate the metabolic 

 processes in lobsters, although the parameters 

 were not defined. The data presented here con- 

 firm this increase in metabolism using three 

 physiological parameters. Figure 1 shows the in- 

 creasing frequency of heart and gill-bailer rates 

 as the temperature rose from 2° to 18°C. Cough 

 rate also increased with increasing temperatures 

 (Fig. 2). Bill and Thurberg (1983) reported a 

 cough rate of 0.4 coughs/minute at 10°C in this 

 species, a rate similar to that reported in this 

 study at 10°C (0.32 coughs/minute). The data re- 

 ported here present a full seasonal profile of three 

 important metabolic measures. They provide a 



FISHERY BULLETIN: VOL. 8.5. NO. 3, 1987. 



643 



