Parrish, J.D., Heins, D.C. and Baker, J.A., 1991. Reproductive season, clutch parameters and oocyte size of the johnny darter Etheostoma nigrum from southwestern Mississippi. American Midland Naturalist, pp.180-186.
| Species | Development state | Trait | Primary Data | Secondary Data |
| Etheostoma nigrum | Egg | Egg size after water-hardening | 1.19 | 1.19 mm |