Table 1.
Mechanism of polarized skylight detections in various animals. RD–rhabdom, PR–photoreceptor, MV–microvilli.
| Animals | Organ | Mechanism |
|---|---|---|
| Honey bees(Apis mellifera, Apis cerana) [54,60] | Compound eyes, ommatidia of the dorsal rim area (DRA) | RD: two populations of orthogonally arranged rhabdomeres; not twistedPR: UV receptor absorbing photopigments for polarization detection, maximum sensitivity for skylight polarized parallel to the microvilliMV: aligned in parallel along the length of each photoreceptor cell; microvilli orientation in a fan-like pattern |
| Desert ants(Cataglypis bicolor, C. fortis)[52,54,58,61] | Compound eyes, ommatidia of the DRA | RD: distal tips are dumb-bell shape and fused rhabdomPR: Polarization vision is mediated by UV receptor cells only; mutually perpendicular microvilliMV: aligned in parallel along the longitudinal axes of cells; microvilli orientation in a fan-like pattern |
| Cricket(Gryllus campestris) [18,58] | Compound eyes, ommatidia of the DRA | RD: fused and an elongated triangle rhabdom, contains two orthogonal microvilli orientationsPR: come in two sets that have their microvilli oriented perpendicularly oriented to each otherMV: strictly aligned along the rhadomeres |
| Beetle (Scarabaeus zambesianus)[15] | Compound eyes, ommatidia of the DRA | RD: heart-shaped with orthogonal microvilliPR: seven photoreceptor rhabdomeresMV: the microvilli of photoreceptor 1 are parallel but perpendicular to photoreceptor 2-7 |
| Monarch butterfly(Danaus plexippus)[21,55] | Compound eyes, ommatidia of the DRA | RD: wide and short rhabdomsPR: two types of photoreceptor with mutually orthogonal microvilli orientation and well-aligned microvilli in each receptorMV: aligned in different planes to optimize skylight reception at all angles for more global photoreceptor activities |
| Butterflies(Pieris rapae, Papilio crucivora, Colias erate) [46,47] | Compound eyes, ommatidia | RD: fused rhabdomRhabdomere: rhabdomere consists of microvilli containing the rhodopsinPhotoreceptor: nine photoreceptors in three groups according to the position of their rhabdomere and specialized for polarization visionMV: microvilli contain rhodopsin |
| Flies (Calliphora erythrocephala, Musca domestica, Drosophila melanogaster)[14,41,62] | Compound eyes, ommatidia of the DRA | RD: open rhabdomPR: have eight photoreceptor cells, with six of them arranged in a trapezoidal pattern around the tiered rhadom and R7 and R8 specialized for detection of polarized skylight and high polarization sensitivityMV: orthogonally arranged |
| Spider(Drassodes cupreus) [63] | Secondary eyes, tapetum | Tapetum: acts as a polarizer, canoe-shaped tapeta; microvilli inside tapetumPR: sensitive to the plane of polarization of skylight, orthogonally arranged microvilli |
| Mantis shrimp(Odontodactylus scyllarus)[64] | Compound eyes, ommatidia of the DRA | Ommatidia: form 6 parallel rows, called midbandPR: specialized for UV (linearly polarized), for colour (blue-green) or polarization vision. Cells respond to skylight with an e-vector oriented parallel to the mid-band and with an e-vector oriented perpendicular to mid-band. Orthogonal arrangement of UV-sensitive photoreceptor cells; quarter-wave retarders.MV: parallel microvilli for polarization sensitivity |
| Locust (Schistocerca gregaria)[13,20] | Compound eyes, ommatidia of the DRA | RD: fused rhabdomPR: largely photoreceptors for blue with high polarization sensitivityMV: microvilli of photoreceptor cell 7 are oriented perpendicularly to microvilli of photoreceptors 1, 2, 5, 6 and 8; microvilli photoreceptor 3 and 4 are irregular; microvilli orientation are arranged in a fan-like pattern |
| Cephalopods (squid, cuttlefish and octopus) [64,65] | Complex skin with pigmented chromatophore organs and structural light reflectors (iridophores) | PR: detect linearly polarized skylight by reflectionMV: orthogonal arrangement of microvilliIridophores: contain stacks of protein plates interspersed by cytoplasm spaces, produce colorful linearly polarized reflective patterns |