Previous studies have shown that the two novel genes of southern rock lobster (Jasus edwardsii) named peJK2 and peJK3 are implicated in eyestalk hormonal regulation of the lobster moult cycle. Northern blot, in situ hybridisation studies and sequence analyses showed that their putative products might be transmembrane proteins associated with cell signal transduction of hormonal signals in the eyestalk during the intermoult phase of the moult cycle. The aim of this study was to analyse coexpression of peJK genes in different J. edwardsii tissues. Using reverse transcriptase–polymerase chain reaction (RT-PCR), the expression of peJK genes was analysed in seven different tissues (eyestalk, brain, epidermis, hepatopancreas, gill, muscle and heart) of an intermoult lobster. During RT-PCR analysis, a novel sequence was isolated, and was named peJK4. It shares 88% and 86% sequence identity with peJK2 and peJK3 respectively. The peJK2 and peJK4 genes are expressed in all tested tissues. Sequence analyses of the predicted peJK2 and peJK4 proteins revealed two common signal transduction motifs, transmembrane helices and protein kinase C. These results showed that the peJK genes of J. edwardsii are a complex group of genes and possibly involved in different signal transduction pathways.