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Fig. 5 | BMC Evolutionary Biology

Fig. 5

From: Structural differences and differential expression among rhabdomeric opsins reveal functional change after gene duplication in the bay scallop, Argopecten irradians (Pectinidae)

Fig. 5

An evolutionary hypothesis describing Gq-opsin duplications in Pectinioidea. Circles represent duplication events. At least five bivalve families (Ostreidae, Pteriidae, Pectinidae, Spondylidae, Limidae) in three Pteriomorphia orders (Ostreida, Pterioida, Pectinoida [49]) possess a Gq-opsin gene homologous to opn-Gq1. One possible scenario is a whole genome duplication (WGD) event unique to the Pectinoida lineage [82] generated a second Gq-opsin copy (opn-Gq1’ to opn-Gq4). Opn-Gq4 under went a tandem duplication (TD), opn-Gq4’. A final round of duplication generated opn-Gq3 and opn-Gq2. The opn-Gq2 copy was subsequently translocated (D&T) to another chromosome. While taxonomic sampling is not dense enough to determine whether these duplications are only in the family Pectinidae or in the order Pectinoida, current evidence supports the latter scenario as the Spondylidae and Limidae possess opn-Gq2 homologs [49]. The other opsin paralogs (opn-Gq3, opn-Gq4) are either unsampled or may have been lost from these two families

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