How does the smallscale smooth-head see?
The smallscale smooth-head (Bathytroctes microlepis) is a fish in the order Osmeriformes. Its eyes belong to the vision type Shallow-water fish tetrachromat.
Measured in this species: sharpness. Measured colour or sharpness: a measured receptor set or acuity in this species; other dials come from relatives or group defaults. Every value below carries its evidence level and sources; nothing is typed by hand.
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What stands out
- It has 4 colour receptor classes, including ultraviolet; people have 3.
- Its sharpest vision resolves 13.5 cycles per degree: the finest stripe pattern it can tell apart from grey.
- Both eyes see the same 32.85° in front of it (binocular overlap), where depth is judged best.
- It stops seeing flicker at 50 Hz, against 60 Hz for people in this dataset, so fast motion looks choppier to it.[12][13]
- Activity pattern: diurnal.
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.
| Dial | Value | Evidence | Sources |
|---|---|---|---|
| Colour | Colour receptors 4 receptor classes: 369 nm (UVS), 461 nm (SWS (blue)), 522 nm (MWS (green)), 570 nm (LWS (long)) receptor set of nearest measured relative Hypomesus pretiosus (same order Osmeriformes) | Group default | [1][2] |
| Ultraviolet yes: at least one receptor peaks in the ultraviolet | Group default | ||
| Sharpness | Acuity 13.5 cycles per degree median of 1 anatomical-ganglion rows (method priority rule) | Measured | [3] |
| Field of view | Binocular overlap 32.85° group default: median of tier-A values in vision type V18 within phylum Chordata (2 species: Danio rerio, Notemigonus crysoleucas) | Group default | [4] |
| Sharp zones (foveas) | Number of foveas 0 group default: mode of tier-A values in vision type V18 within phylum Chordata (2 species: Toxotes jaculatrix, Anableps anableps) | Group default | [5][6] |
| Fovea type ventrotemporal area (high rgc density) | Group default | [5][6] | |
| Night vision | Activity pattern diurnal group default: mode of tier-A values in vision type V18 within phylum Chordata (224 species: Amphiprion ocellaris, Acanthochromis polyacanthus, Acanthurus bahianus, Acanthurus chirurgus, Acanthurus coeruleus… | Group default | [7][8] |
| Rods vs cones cone-dominated | Group default | [7][8] | |
| Motion (flicker fusion) | Flicker fusion frequency 50 Hz group default: median of tier-A values in vision type V18 within phylum Chordata (45 species: Carassius auratus, Danio rerio, Poecilia reticulata, Oncorhynchus mykiss, Acanthochromis polyacanthus, Anguilla anguilla) | Group default | [9][10][11][12][13][14][15] |
Related animals
- Bigscale deep-sea smelt same vision type
- Abyssal smooth-head same vision type
- Baird's smooth head same vision type
- Barreleye (Monacoa grimaldii) same vision type
- Barreleye (Opisthoproctus soleatus) same vision type
- Binocular fish same vision type
More fish: all fish with measured vision data.
Sources
- Schweikert LE, Fitak RR, Caves EM, Sutton TT, Johnsen S. 2018. Spectral sensitivity in ray-finned fishes: diversity, ecology and shared descent. J Exp Biol 221:jeb189761. Table S1. doi.org/10.1242/jeb.189761
- VPOD in-vivo (MSP / single-cell) lambda max compendium, file scp_cleaned.csv, VPOD GitHub (Frazer et al. 2025 bioRxiv 10.1101/2025.08.22.671864). github.com/VisualPhysiologyDB/visual-physiology-opsin-db/tree/main/scripts_n_notebooks/vpod_ML_workflows/mine_n_match/data_sources/lmax/vpod
- Caves EM, Sutton TT, Johnsen S (2017) Visual acuity in ray-finned fishes correlates with eye size and habitat. J Exp Biol 220:1586-1596. Table S1.. doi.org/10.1242/jeb.151183
- Pita D, Moore BA, Tyrrell LP, Fernandez-Juricic E. 2015. Vision in two cyprinid fish: implications for collective behavior. PeerJ 3:e1113.. doi.org/10.7717/peerj.1113
- species_v1:Schwab et al. 2001
- species_v1:Temple et al. 2010
- Froese R. & Pauly D. (eds). FishBase, snapshot v25.04 (morphmet, morphdat, species, families tables), distributed as parquet by C. Boettiger for rfishbase.. fishbase.org
- 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
- Horodysky A, Brill R, Crawford K et al. (2013) Comparative visual ecophysiology of mid-Atlantic temperate reef fishes. Biology Open
- Fogg LG, Chung W-S, Marshall NJ, Cortesi F, de Busserolles F. 2023. Multiple rod layers increase the speed and sensitivity of vision in nocturnal reef fishes. Proc R Soc B 290 (doi:10.1098/rspb.2023.1749). Data: Dryad doi:10.5061/dryad.280gb5mtf, mirrored on Zenodo 7636493. doi.org/10.5061/dryad.280gb5mtf
- 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
- 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
- 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
- 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
- species_v1:Patterson et al. 2002 (via Lafitte et al. 2022)
Every value cites its sources (all sources). Data: catalogue-v1, built 2026-09-29. Accuracy notes: how accurate is this?