No abstract

No abstract

Abstract-Oligochaetes (Lumbriculus variegatus) were exposed to sediment spiked with four 14 C-polychlorinated alkanes (PCAs) (C 12 H 20 were readily available to sediment-ingesting oligochaetes, whereas C 16 H 21 Cl 13 had lower bioavailability. Uptake rates of the C 12 -PCAs were greater than the C 16 -PCAs, but half-lives (t 1/2 s) were greater for the C 16 -PCAs (t 1/2 ϭ 30-33 d) than for the C 12 -PCAs (t 1/2 ϭ 12-14 d). Biota-sediment accumulation factors were Ͼ1 for C 12 H 20 Cl 6 , C 12 H 16 Cl 10 , and C 16 H 31 Cl 3 , but Ͻ1 for C 16 H 21 Cl 13 . Comparison of toluene-extractable and -nonextractable 14 C suggest that PCAs were biotransformed in aerobic sediments and by oligochaetes, and that the susceptibility to degradation in sediments decreases with increasing chlorine content. The relative abundance of individual PCAs may differ between sediment and benthic invertebrates because of differences in the bioaccumulation and degradation of PCAs of varying carbon chain length and chlorine content.

Oligochaetes (Lumbriculus variegatus) were exposed to sediment spiked with four 14C‐polychlorinated alkanes (PCAs) (C12H20C16 [56% Cl by weight], C12H16Cl10 [69% Cl], C16H31Cl3 [35% Cl], and C16H21Cl13 [69% Cl]) to measure bioaccumulation parameters and biotransformation. Chlorinated paraffins are industrial products that consist of thousands of different PCAs. Chlorinated paraffins are hydrophobic (log octanol–water partition coefficients [Kows] > 5.0) and are reported to have relatively high concentrations in sediment compared with other persistent organochlorines; however, no data exist on their bioavailability from sediment. The PCAs C12H20Cl6, C12H16Cl10, and C16H31Cl3 were readily available to sediment‐ingesting oligochaetes, whereas C16H21Cl13 had lower bioavailability. Uptake rates of the C12‐PCAs were greater than the C16‐PCAs, but half‐lives (t½s) were greater for the C16‐PCAs (t½ = 30‐33 d) than for the C12‐PCAs (t½ = 12‐14 d). Biota–sediment accumulation factors were >1 for C12H20Cl6, C12H16Cl10, and C16H31Cl3, but <1 for C16H21Cl13. Comparison of toluene‐extractable and ‐nonextractable 14C suggest that PCAs were biotransformed in aerobic sediments and by oligochaetes, and that the susceptibility to degradation in sediments decreases with increasing chlorine content. The relative abundance of individual PCAs may differ between sediment and benthic invertebrates because of differences in the bioaccumulation and degradation of PCAs of varying carbon chain length and chlorine content.

While the reproductive and thyroidal systems are extensively studied in fish, they are largely studied in isolation from one another, but there is evidence supporting cross-regulation between these two systems. To better understand hormone action and the potential cross-regulation between estrogen and thyroid hormones, we examined gene expression changes in estrogen receptor (ER) and thyroid receptor (TR) subtypes and key enzymes responsible for the local synthesis and availability of estrogen and thyroid hormones (aromatase B and deiodinase, respectively) in sexually regressed, adult, male goldfish in response to 3 days waterborne exposures to 17β-estradiol (E2; 1 nM), triiodothyronine (T3; 20 and 100 nM), and co-treatments thereof. Treatments with E2 alone did not effect ER subtype transcripts in the liver, telencephalon, or testis; however, in the testis, 1 nM T3 decreased ERα and ERβ1 and co-treatments of T3 and E2 decreased ERβ1 levels. TRα-1 and TRβ transcripts were not auto-regulated by T3 or cross-regulated by E2. Although deiodinase type I levels were also unaffected, deiodinase type II decreased in response to T3 treatments. Liver deiodinase type III transcripts increased in response to T3 treatments, while E2 exhibited antagonistic effects on this T3-mediated induction. These results provide novel evidence of cross-talk between the reproductive and thyroid endocrine axes in a model teleost.