Early Life-Stage Mortalities of Japanese Medaka (Oryzias Latipes) Exposed to Polychlorinated Diphenyl Ethers

Abstract

Polychlorinated diphenyl ethers (PCDEs) are a group of compounds that resemble polychlorinated dibenzofurans in structure that have been detected at ppb concentrations in fish from the Great Lakes. The objective of this project was to determine the toxicological significance of PCDE residues in fish. PCDE congener 77 (3,3Ј,4,4Ј-tetrachlorodiphenyl ether), congener 71 (2,3Ј,4Ј,6-tetrachlorodiphenyl ether), congener 118 (2,3Ј,4,4Ј,5-pentachlorodiphenyl ether), and congener 105 (2,3,3Ј,4,4Ј-pentachlorodiphenyl) were tested for toxicity with early life stages (ELS) of Japanese medaka, Oryzias latipes. These embryotoxicity data showed that the mono-ortho congeners 105 and 118 and the non-ortho congener 77 were embryotoxic to medaka. However, the toxic equivalency factors (TEFs) estimated for congeners 105, 77, and 118 relative to 2,3,7, 8-TCDD were relatively low at 0.00056, 0.00003, and 0.00001, respectively. PCDE compounds were isolated in a fraction prepared from a bulk extract of Lake Ontario lake trout. In this fraction, congeners 99 (2,2Ј,4,4Ј,5-pentaCDE), 153 (2,2Ј,4,4Ј,5,5Ј-hexaCDE), 154 (2,2Ј,4,4Ј,5,6Ј-hexaCDE), and 163 (2,3,3Ј,4Ј,5, 6-hexaCDE) comprised 81.3% of total PCDEs, while congeners 77, 71, 118, and 105 comprised only 1.1% of total PCDEs. The LC50 for embryotoxicity of this fraction was equivalent to 15.5 ng/ml of total PCDEs. Toxicopathic lesions noted in medaka embryos exposed to either individual PCDEs or the lake trout extract included vascular hemorrhage but no edematous lesions. Medaka fry did not exhibit symptoms of hyperexcitability prior to death, as has been noted for ELS of lake trout exhibiting ''swim-up syndrome.'' These data indicate that PCDEs in Lake Ontario lake trout have the potential to induce toxic effects in early life stages of fish. However, the medaka mortalities were not consistent with observations of either ''blue-sac disease'' or swim-up syndrome observed in some natural populations of Great Lakes salmonids.

Toxicity of C10-, C11-, C12-, and C14-Polychlorinated Alkanes to Japanese Medaka (Oryzias Latipes) Embryos

“…The LC50 values for the PCAs are at least three to six orders of magnitude higher than those observed for chlorinated dioxin and furan congeners, polychlorinated biphenyl congeners, or polychlorinated diphenyl ether congeners using Japanese medaka eggs ( Table 6). The LC50 determined for TCDD in this study is in the range reported in other studies for TCDD using Japanese medaka eggs [24][25][26][27][28]. As well, Wisk and Cooper [24] reported an ED 50 of 0.24 ng/g for TCDD equivalents in larvae, which is similar to the concentration in eggs at the LOEC in tissue in this study ( Table 5).…”

“…Hatching success (by day 20) was low for many of the treatments and was well below the hatching success reported in other studies on Japanese medaka eggs [24][25][26][27][28]. The average time of hatching (Ͼ15 d) was also longer than what is normally [32] and assuming the chemical is a narcotic.…”

“…The partitioning ratios of the three 14 C-PCAs, at three concentrations (n ϭ 3), between rearing solution and glass were determined and used for establishing the amount of PCA needed to achieve the desired rearing solution concentrations. The TCDD concentrations were based on past Japanese medaka embryo toxicity results [24,28].…”

“…Polychlorinated n-alkanes (PCAs) with carbon chain lengths between 10 and 30 are used for a variety of industrial applications, including lubricating additives, flame retardants, adhesives, sealants, and a number of other miscellaneous applications [1][2][3]. Commercial PCA formulations, also known as chlorinated paraffins, are classified as short (C [10][11][12][13], medium (C [14][15][16][17], and long (C [18][19][20][21][22][23][24][25][26][27][28][29][30] ) with varying amounts of chlorination (ϳ35-70% by weight). Annual world production of PCAs is estimated at greater than 300 kilotonnes, and they remain one of the last high molecular weight organochlorines in production and use in North America and western Europe [4].…”

“…These PCAs were chosen because synthesis and analytical methods were available for these compounds and short-chain PCAs (C 10-13 ) are currently being evaluated for regulation in Canada. The Japanese medaka assay has been used to assess the toxicity of a number of hydrophobic organochlorines, such as chlorinated dioxins and polychlorinated biphenyls [24][25][26][27][28], allowing a relative comparison of PCA toxicity.…”