The authors would like to correct an error in J. Exp. Biol. 201, 1799-1808.

In this paper, supporting evidence for the presence of an NPR-C/D type receptor used a partial sequence of putative lamprey (Geotria australis) NPR-C/D obtained by sequencing a PCR-generated fragment that was subsequently cloned for sequencing.

In subsequent work on rainbow trout (Oncorhynchus mykiss) in her laboratory, Dr Toop and colleagues have obtained the identical cDNA sequence several times from rainbow trout gill but have been unable to repeat the amplification with lamprey cDNA. In addition, comparisons with the now available expressed sequence tag (GenBank accession number DY697355) from the Atlantic salmon, Salmo salar, a close relative of the trout, show 90%identity with the sequence in question. This information leads them to conclude that the published sequence is not from lamprey but from rainbow trout, tissue of which was present in the laboratory at the time. They conclude that, owing to the sensitive nature of the PCR reaction, the reagents or the lamprey mRNA/cDNA were contaminated with trout nucleic acid, which was amplified instead of the lamprey cDNA.

In the paper, the cDNA sequence and deduced amino acid sequence are presented in Figs 7 and 8, detailed in the Results section entitled `Molecular Cloning' on p. 1805 and discussed in the fourth paragraph of the Discussion on pp. 1806-1807.

The authors apologise to readers for this error.

Publisher's note: we would like to reassure readers that expert opinion has confirmed that this error does not affect any of the other experiments presented in the paper or the conclusions drawn from this study.