Xenobiotic activation of the aryl hydrocarbon receptor (AHR) by 2,3,7,8-tetrachlorodibenzo--dioxin (TCDD) prevents the proper formation of craniofacial cartilage and the heart in developing zebrafish. Downstream molecular targets responsible for AHR-dependent adverse effects remain largely unknown; however, in zebrafish has been identified as one of the most-reduced transcripts in several target organs and is hypothesized to have a causal role in TCDD-induced toxicity. The reduction of expression in TCDD-exposed zebrafish embryos has been shown to contribute to heart and jaw malformation phenotypes. The mechanisms by which AHR2 (functional ortholog of mammalian AHR) activation leads to reduced expression levels and subsequent target organ toxicity are unknown. We have identified a novel long noncoding RNA () that is upregulated by strong AHR ligands and is located adjacent to the gene. We hypothesize that is regulated by AHR2 and transcriptionally represses The transcript functions as an RNA macromolecule, and expression is AHR2 dependent. Antisense knockdown of results in an increase in expression during both normal development and AHR2 activation, which suggests relief in repression. During development, was expressed in tissues with essential functions, including the jaw/snout region, otic vesicle, eye, and brain. Reducing the levels of resulted in altered neurologic and/or locomotor behavioral responses. Our results place as an intermediate between AHR2 activation and the reduction of mRNA in the AHR2 signaling pathway.