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How does the spineback hairy crab see?

Pilumnus sayi · order Decapoda · Crustaceans

The spineback hairy crab has one cone type, so no colour vision in daylight.[1] Its sharpest vision resolves 0.15 cycles per degree, against 63.75 for people in this dataset.[6][7][8] The spineback hairy crab stops seeing flicker at 22.5 Hz, against 60 Hz for people.[26][27][28]

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  • 1colour receptor classMeasured
  • 0.15cycles per degree (sharpness)Estimated
  • 22.5hertz flicker fusion (motion)Estimated

The spineback hairy crab (Pilumnus sayi) is a crustacean in the order Decapoda. Its eyes belong to the vision type Crustacean (mantis shrimp, crab): compound eyes whose colour classes, ultraviolet and polarisation vision vary widely between species. Measured in this species: colour. Measured colour or sharpness: a measured receptor set or acuity in this species; other dials come from relatives or group defaults.

This is a simulation built from published eye measurements, not what the animal experiences.

Method: How we know what animals see (the See Like Animals vision engine) · Sources · Last updated . Every value below carries its evidence level and sources; nothing is typed by hand.

What the spineback hairy crab sees: colour receptors

Spineback hairy crab colour receptor peaks, 300 to 700 nmSpineback hairy crab: 1 receptor peak at 489 nm; you: 3 at 421.5, 532, 558.4 nm. ultraviolet300400500600700
Spineback hairy crab: 489 nmPeople: 421.5, 532, 558.4 nmWavelength in nanometres

What does a spineback hairy crab's vision look like?

The spineback hairy crab has one cone type, so no colour vision in daylight.[1] Fine detail is blurred to what 0.15 cycles per degree can resolve.

Can the spineback hairy crab see colour?

Not in daylight: the spineback hairy crab has one cone type, so it sees brightness but no hue.[1]

How far can the spineback hairy crab see?

Distance depends on the size of what is seen, so sharpness is the measure. The spineback hairy crab resolves 0.15 cycles per degree, against 63.75 for people in this dataset, so a detail must be about 425 times larger, or that much closer, for it to make it out as well as a person.[6][7][8]

Can the spineback hairy crab see in the dark?

The catalogue records activity pattern: nocturnal and rods vs cones: no rods (invertebrate photoreceptors). Night mode in the tool uses these traits by a stated engine rule, not a measured sensitivity.[2]

Does the spineback hairy crab see in slow motion?

The spineback hairy crab stops seeing flicker at 22.5 Hz, against 60 Hz for people in this dataset. So fast motion looks choppier to it than to people, not slower.[26][27][28]

What stands out

  • It has one receptor class for colour, so it sees brightness but no hue.
  • Its sharpest vision resolves 0.15 cycles per degree: the finest stripe pattern it can tell apart from grey.
  • It stops seeing flicker at 22.5 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[29][27]
  • Activity pattern: nocturnal.

The six dials

Evidence levels: how the tiers work. "Measured" means a value measured in this species; "Estimated" values come from a close relative or an eye-size formula. The last column gives the values for people from the same catalogue.

Vision values for the spineback hairy crab (Pilumnus sayi), catalogue-v1
DialValueEvidenceSourcesPeople
ColourColour receptors
1 receptor class: 489 nm (MWS (green))
measured in this species
Measured[1]Colour receptors: 3 receptor classes: 421.5 nm (VS/SWS (violet)), 532 nm (MWS (green)), 558.4 nm (LWS (long)) Measured (not re-verified)[2][3][4][5]
SharpnessAcuity
0.15 cycles per degree
median of 94 relatives in order Decapoda: Anchistus custos, Ancylomenes holthuisi, Ancylomenes pedersoni, Ancylomenes venustus, Austruca lactea, Brucecaris tenuis
Group default[6][7][8]Acuity: 63.75 cycles per degree Measured[9][10]
Angle between facets
1.6°
median of 1 relatives in class Malacostraca: Phronima sedentaria
Group default[11]
Eye type
compound eye
Field of viewNo value in the catalogue.Binocular overlap: 122.5° Measured[12][13]
Total field of view: 200° Measured (not re-verified)[14]
Blind area behind the head: 160° Derived[14]
Eye placement: frontal Derived[12][13]
Sharp zones (foveas)No value in the catalogue.Number of foveas: 1 Measured[15]
Fovea type: fovea Measured[15]
Night visionActivity pattern
nocturnal
group default: mode of tier-A values in vision type the "Crustacean (mantis shrimp, crab)" type within phylum Arthropoda (1 species: Ligia exotica)
Group default[2]Activity pattern: diurnal Measured (not re-verified)[16][17][18][2][19][20][21][22]
Pupil shape: vertical Group default[23][24]
Reflective layer (tapetum): no Measured[25]
Rods vs cones: cone-dominated Derived[16][17][18][2][19][20][21][22]
Rods vs cones
no rods (invertebrate photoreceptors)		Group default[2]
Motion (flicker fusion)Flicker fusion frequency
22.5 Hz
median of 24 relatives in order Decapoda: Eugonatonotus crassus, Eumunida picta, Gastroptychus spinifer, Funchalia villosa, Janicella spinicauda, Oplophorus gracilirostris
Group default[26][27][28]Flicker fusion frequency: 60 Hz Measured[29][27]

Other senses

  • polarisation vision: optional overlay of degree/angle of linear polarisation (Group default)

Related animals

More crustaceans: all crustaceans with measured vision data. Same eye type: Crustacean (mantis shrimp, crab).

Sources

  1. Porter ML. Crustacean photoreceptor lambda max compilation, Table 1-1 (dissertation, "Porter_2005" in VPOD); extracted from PDF by VPOD with tabula. github.com/VisualPhysiologyDB/visual-physiology-opsin-db
  2. Longcore T. 2023. A compendium of photopigment peak sensitivities and visual spectral response curves of terrestrial wildlife to guide design of outdoor nighttime lighting. Basic Appl Ecol 73:40-50. doi:10.1016/j.baae.2023.09.002. doi.org/10.5281/zenodo.8432720
  3. Kirwan J. luxR 0.1.1: Underwater Light Analysis and Visual Ecology (R-universe), data species_sensitivities. github.com/JohnKirwan/luxR
  4. Müller B, Glösmann M, Peichl L, Knop GC, Hagemann C, Ammermüller J (2009) Bat eyes have ultraviolet-sensitive cone photoreceptors. PLoS ONE 4:e6390
  5. Thermal Activation and Photoactivation of Visual Pigments (2004)
  6. AndrewPMeade/FabricTools, sciphy/data_utils/datasets/Arthropod.CompoundEyes.csv (acuity, body length, light, media for 281 arthropods; columns match Feller et al. 2021 Arthropod Struct Dev 60:101002). github.com/AndrewPMeade/FabricTools
  7. Feller KD, Sharkey CR, McDuffee-Altekruse A, Bracken-Grissom HD, Lord NP, Porter ML, Schweikert LE 2021. Surf and turf vision: patterns and predictors of visual acuity in compound eye evolution. Arthropod Structure & Development 60:101002. doi.org/10.1016/j.asd.2020.101002
  8. Schweikert L, Davis A, Johnsen S et al. 2020. Visual perception of light organ patterns in deep‐sea shrimps and implications for conspecific recognition. Ecology and Evolution. doi.org/10.1002/ece3.6643
  9. Kirk EC, Kay RF 2004. The evolution of high visual acuity in the Anthropoidea. In Anthropoid Origins, Table 1 (behavioural acuity). doi.org/10.1007/978-1-4419-8873-7_20
  10. Veilleux CC, Kirk EC 2014. Visual acuity in mammals. Brain Behav Evol 83:43, Supplementary Table 1 (cleaned CSV in Evo-M1-Trait-Data). doi.org/10.1159/000357830
  11. Bagheri Z, Jessop A, Partridge J et al. 2022. A new computational model illuminates the extraordinary eyes of Phronima. PLOS Computational Biology. doi.org/10.1371/journal.pcbi.1010545
  12. Heesy CP 2004. On the relationship between orbit orientation and binocular visual field overlap in mammals. Anat Rec 281A:1104, Table 1. doi.org/10.1002/ar.a.20116
  13. Heffner RS, Heffner HE 1992. Visual factors in sound localization in mammals. J Comp Neurol 317:219, Table 1 (via Evo-M1 sensory merge). doi.org/10.1002/cne.903170302
  14. species_v1:Campbell & Green 1965
  15. Kopania EEK, Clark NL. 2025. Mammalian retinal specializations for high acuity vision evolve in response to both foraging strategies and morphological constraints. Evolution Letters 9: qrae072. Supplementary Tables S1-S2.. doi.org/10.1093/evlett/qrae072
  16. Anderson SR, Wiens JJ. 2017. Out of the dark: 350 million years of conservatism and evolution in diel activity patterns in vertebrates. Evolution 71:1944-1959. Dryad doi:10.5061/dryad.fg700. doi.org/10.5061/dryad.fg700
  17. Borges R, Johnson WE, O'Brien SJ, Gomes C, Heesy CP, Antunes A (2018) Adaptive genomic evolution of opsins reveals that early mammals flourished in nocturnal environments. BMC Genomics 19:121
  18. Wilman et al. 2014 EltonTraits 1.0, MamFuncDat.txt. doi.org/10.6084/m9.figshare.3559887.v1
  19. Maor R, Dayan T, Ferguson-Gow H, Jones KE. 2017. Temporal niche expansion in mammals from a nocturnal ancestor after dinosaur extinction. Nature Ecology & Evolution 1:1889-1895. Supplementary Table 1. doi.org/10.1038/s41559-017-0366-5
  20. Jones KE et al. 2009. PanTHERIA: a species-level database of life history, ecology, and geography of extant and recently extinct mammals. Ecology 90:2648. Ecological Archives E090-184. doi.org/10.1890/08-1494.1
  21. Schmitz L, Motani R. 2011. Science 332:705-708, SOM. doi.org/10.1126/science.1200043
  22. Moura et al. 2024. A phylogeny-informed characterisation of global tetrapod traits addresses data gaps and biases. PLoS Biol 22:e3002658. TetrapodTraits v3.0.1.. doi.org/10.5281/zenodo.22536349
  23. Banks MS, Sprague WW, Schmoll J, Parnell JAQ, Love GD. 2015. Science Advances 1:e1500391. doi.org/10.1126/sciadv.1500391
  24. Cervino NG et al. 2021. A closer look at pupil diversity and evolution in frogs and toads. Proc R Soc B 288:20211402. doi.org/10.6084/m9.figshare.15112050.v1
  25. Guareschi BLV, Sallum JMF, Salles MV, de Moraes JGO, Bortolini M, Cray C, Moore BA, da Rosa CC, Montiani-Ferreira F. 2025. GUCY2D-Associated Retinopathy: A Comparative Study Between Humans and German Spitz Dogs. Veterinary sciences 12(9):879. doi.org/10.3390/vetsci12090879
  26. Haarlem CS, Hynes C, Jackson AL, Mitchell KJ, O'Connell RG, Healy K. 2026. Pace of ecology drives the tempo of visual perception across the animal kingdom. Nature Ecology & Evolution (doi:10.1038/s41559-026-02994-7). Figshare dataset 10.6084/m9.figshare.30556475. doi.org/10.6084/m9.figshare.30556475
  27. Inger R, Bennie J, Davies TW, Gaston KJ. 2014. Potential biological and ecological effects of flickering artificial light. PLoS ONE 9(5): e98631. Table 3. doi.org/10.1371/journal.pone.0098631
  28. Lafitte A, Sordello R, Legrand M, Nicolas V, Obein G, Reyjol Y. 2022. A flashing light may not be that flashy: A systematic review on critical fusion frequencies. PLoS ONE 17(12): e0279718. S10 File (CFF database). doi.org/10.1371/journal.pone.0279718
  29. Healy K, McNally L, Ruxton GD, Cooper N, Jackson AL. 2013. Metabolic rate and body size are linked with perception of temporal information. Animal Behaviour 86:685-696. Table 1. doi.org/10.1016/j.anbehav.2013.06.018

Every value cites its sources (all sources). Values were extracted from these works and converted (units, medians, derived values); changes are ours, and the listed sources do not endorse this site. Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this? Method: how we know.