Table 1. Characteristics summary (morphology, opsin, phototransduction cascade, and electrophysiology) of the transmuted photoreceptors of different species compared to true rods and true cones.

Lizard data are for the genus Anolis. Lamprey is the sea lamprey Petromyzon marinus. Salamander is the tiger salamander Ambystoma tigrinum. Pearlside is the Mueller’s pearlside M. muelleri. The snake with the cone-like rods is the diurnal garter snake Thamnophis proximus. The snake with the rod-like cones data are for the nocturnal genus Hypsiglena. The gecko is the nocturnal Tokay gecko Gekko gekko. The skate is the genus Raja. R, true rod; C, true cone; n.a., not available; poly, polysynaptic.

Photoreceptor characteristics	True rod (1, 19)	True cone (1, 19)	Cone-like rod				Rod-like cone
			Snake (7, 78)	Skate (10, 45, 79)	Lizard (5, 80, 81)	Lamprey (9, 82, 83)	Gecko (6, 84–86)	Snake (4, 35)	Salamander (8, 87)	Pearlside (this study)
Outer segment shape	Long, rod- shaped (cylindrical)	Short, cone- shaped (distally tapering)	C	R	C	R	R	R	R	R
Outer segment discs	Individual sealed disc, separated from the plasma membrane	Discs continuous with the plasma membrane (open)	R	R	n.a.	R C	R C	n.a.	n.a.	R
Incisure	Present	Absent	n.a.	n.a.	C	C	R	n.a.	R	R
Paraboloid	Absent	Present					C	R	R	R
Oil droplet	Absent	Sometimes present	R	n.a.	C	n.a.	R	R	R	R
Synaptic ending	Small, spherical, oligosynaptic	Large, conical, flat-end base, polysynaptic	n.a.	C	n.a.	R C Small poly	C	n.a.	R C Small poly	R C Small poly
Opsin	rh1	sws1, sws2, lws, rh2	R	R	R	R	C rh2	C sws1 lws	C sws2	C rh2-1 rh2-2
Spectral sensitivity (nm)	480–510	rh2, 450–530 sws1, 360–440 sws2, 400–450 m/lws, 510–560	R 482	R 500	R 491	n.a.	C 521	C 358, 536	C 432	C 441 (both pigments)
Phototransduction cascade	Rod-like	Cone-like	R	n.a.	n.a.	n.a.	C(R)	n.a.	R	C
Cell physiology	Rod properties (high sensitivity)	Cone properties (fast, never saturate)	n.a.	R C	n.a.	R	R	n.a.	n.a.	n.a.