---
title: "Zebrafish · Animals and other organisms · Entities · Simulation Hypothesis"
url: https://simulation-hypothesis.com/entities/zebrafish
description: "A small fish widely used in neuroscience. Its neurons haven't been fully counted. The adult brain has about 10 million cells."
license: https://creativecommons.org/licenses/by/4.0/
credit: "Ross Allan Dahl, Simulation Hypothesis (simulation-hypothesis.com)"
---

[Entities](https://simulation-hypothesis.com/entities) › Animals and other organisms › Fish and amphibians

# Zebrafish

Danio rerio

A small fish widely used in neuroscience. Its neurons haven't been fully counted. The adult brain has about 10 million cells.

Neurons

No published count

## Evidence

* Fish have nociceptors and change their behaviour in ways linked to pain. This was shown in trout, and it's used here as the reference for fish, not as a result for zebrafish.  
Sneddon LU, Braithwaite VA, Gentle MJ (2003) Do fishes have nociceptors? Evidence for the evolution of a vertebrate sensory system. Proc R Soc Lond B 270(1520):1115-1121\. doi:10.1098/rspb.2003.2349.

The [New York Declaration on Animal Consciousness](https://sites.google.com/nyu.edu/nydeclaration/declaration) (2024) finds at least a realistic possibility of conscious experience in all vertebrates and in many invertebrates, including cephalopods, decapod crustaceans and insects.

Assess it against the published criteria