Fig. 2.

Phototransduction cascade gene expression in the retina of five deep-sea fish species. (A) Heat map of the expression of individual phototransduction cascade genes for each sample, based on normalized numbers of reads (FPKM). (B) Pie charts comparing mean values of relative expression of the opsin genes (rod RH1 and cone RH2), photoreceptor-specific cascade transducin genes (rod-type GNAT1 and cone-type GNAT2), and all cascade genes excluding opsins (photoreceptor-specific transducins, arrestins and phosphodiesterases) summarized. The green rectangles highlight the two aulopiform species with the discordance between the opsin type (rod-specific) and phototransduction cascade genes (cone-specific) in adults. (C) Focus on the common fangtooth (Anoplogaster cornuta) transitional phase shown as a sequence for seven larval and one adult sample. Size given as standard length (SL). Note that all fangtooth larvae expressed both RH1 and RH2, with an increasing proportion of RH1 to RH2 as the larvae grew in size (with the exception of the largest larva where RH1:RH2 was 28:72). Smaller larvae also expressed the SWS2 gene. Except for the adult, all other individuals had traits of larval phenotypes (dorsal and ventral horns and small teeth; fig. 1) and were collected relatively shallow between 0 and 300 m using plankton trawls.