Mardi C. Hastings
Dept. of Mech. Eng., Ohio State Univ., Columbus, OH 43210-1107
Acoustic stunning, a complete physiological shutdown of bodily functions, occurs in some marine animals when exposed to intense sound for a short period of time. Anecdotal evidence of acoustic stunning has been reported in the literature [G. E. MacGinitie and N. MacGinitie, Natural History of Marine Animals (McGraw--Hill, New York, 1968); K. S. Norris and B. Mohl, Am. Naturalist 122, 85--104 (1983)], but the physiological mechanisms and threshold values associated with this phenomenon have not been studied. Acoustic stunning of gouramis (Trichogaster trichopterus) was observed in the laboratory when they were exposed to intense pure tones underwater; however, oscars (Atronotus ocellatus) and goldfish (Carassius auratus) exposed to similar tones were not acoustically stunned. This paper examines the characteristics of the sound field that caused the transient stunning. In addition, differences in body size and geometry as well as in structure of the ear and lateral line among the three species are examined in an effort to explain why only the gourami was affected.