Effects of lethal levels of environmental hypercapnia on cardiovascular and blood-gas status in yellowtail, Seriola quinqueradiata.
The cardiorespiratory responses were examined in yellowtail, Seriola quinqueradiata exposed to two levels of hypercapnia (seawater equilibrated with a gas mixture containing 1% CO(2) (water PCO(2) = 7 mmHg) or 5% CO(2) (38 mmHg)) for 72 hr at 20 degrees C. Mortality was 100% within 8 hr at 5% CO(2), while no fish died at 1% CO(2). No cardiovascular variables (cardiac output, Q; heart rate, HR; stroke volume, SV and arterial blood pressure, BP) significantly changed from pre-exposure values during exposure to 1% CO(2). Arterial CO(2) partial pressure (PaCO(2)) significantly increased (P < 0.05), reaching a new steady-state level after 3 hr. Arterial blood pH (pHa) decreased initially (P < 0.05), but was subsequently restored by elevation of plasma bicarbonate ([HCO(3)(-)]). Arterial O(2) partial pressure (PaO(2)), oxygen content (CaO(2)), and hematocrit (Hct) were maintained throughout the exposure period. In contrast, exposure to 5% CO(2) dramatically reduced Q (P < 0.05) through decreasing SV (P < 0.05), although HR did not change. BP was transiently elevated (P < 0.05), followed by a precipitous fall before death. The pHa was restored incompletely despite a significant increase in [HCO(3)(-)]. PaO(2) decreased only shortly before death, whereas CaO(2) kept elevated due to a large increase in Hct (P < 0.05). We tentatively conclude that cardiac failure is a primary physiological disorder that would lead to death of fish subjected to high environmental CO(2) pressures.
Marine Research Institute, Nagasaki University, Japan.
Kyoung-Seon
KS
Lee
Jun
J
Kita
Atsushi
A
Ishimatsu
D000818:Animals; D002245:Carbon Dioxide / Q000009:adverse effects* / Q000032:analysis / Q000097:blood; D002319:Cardiovascular System / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005399:Fishes / Q000097:blood* / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects; D006935:Hypercapnia / Q000097:blood*; D010313:Partial Pressure; D012623:Seawater / Q000737:chemistry*; D013997:Time Factors
D002245:Carbon Dioxide