Dose-dependent effects of developmental mercury exposure on C-start escape responses of larval zebrafish Danio rerio

Autor: D. N. Weber
Rok vydání: 2006
Předmět:
Zdroj: Journal of Fish Biology. 69:75-94
ISSN: 1095-8649
0022-1112
DOI: 10.1111/j.1095-8649.2006.01068.x
Popis: Zebrafish Danio rerio embryos were exposed to 0, 25, 50 or 75 ppb Hg 2+ from 0 to 24 h post-fertilization (hpf) then placed into Hg 2+ -free water. Inductively coupled plasma-mass spectrophotometer analysis of whole embryo Hg 2+ content at 24 hpf showed a positive correlation with exposure regime (Pearson's one-tailed, r 2 = 0-698, P < 0-01); at 5 days posthatch (dph), whole larval Hg 2+ content was not detectable. Hg 2+ -induced behavioural deficits in larvae were, therefore, due to changes during embcyogenesis and not to residual Hg 2+ in the larvae. At 5 dph, larvae were tested for responses to different frequencies but equal intensities of vibrational stimuli generated by a remotely controlled plastic hammer. Data were recorded by high-speed videography and computer-analysed for latency of response (ms), amplitude of the response as measured by maximum initial velocity [normalized as body (standard) lengths s -1 ; V max ] and duration of behaviour from initial head movement to cessation of caudal tail movement (ms). A single mechanical stimulus resulted in behavioural outcomes that were related to embryonic Hg 2+ uptake. Response latency increased with exposure level and displayed an increase of ×1·5-2·5 over control values (ANOVA, P < 0·01). The V max decreased with exposure level to a low of 71% of control at the highest Hg 2+ concentration (ANOVA, P < 0·01). Duration of behaviour displayed a biphasic response pattern in which exposure to 0, 50 or 75 ppb Hg 2+ did not result in a significantly different response yet exposure to 25 ppb Hg 2+ caused a significantly longer time of active response (ANOVA, P < 0·01). Repeated stimulation (1, 2 or 4 hits s -1 ) resulted in a concentration-dependent increase in response failures. Regardless of stimulation frequency, larvae exposed to 0 or 25 ppb Hg 2+ as embryos maintained higher V max levels for longer intervals during the testing period than those exposed as embryos to either 50 or 75 ppb Hg 2+ .
Databáze: OpenAIRE
Externí odkaz: