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To draw fish gills, show them inside a cutaway just behind the operculum—the bony cover behind the eye. Add a curved gill arch, fine repeated filaments along it, and shorter comb-like rakers on its inner edge. Arrows from the mouth across the gills and out near the cover make the water’s path clear.
Where fish gills go in a drawing
In a typical bony fish, the gills sit behind the operculum, or gill cover. Draw the fish in side view, locate the curved cover behind the eye, then lift or remove part of it in your diagram to reveal the gills underneath. Keeping the cover lightly drawn or using a cutaway avoids making the gills appear to sit on the outside of the fish.
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How to draw fish gills step by step
- Block in the head and operculum. Sketch the fish’s head in side view. Mark the eye and the curved gill cover behind it; keep the cover light if you plan to show the internal anatomy.
- Draw the gill arch. Inside the cutaway, add one firm curved or V-shaped support. The arch holds the gill structures.
- Add the filaments. Draw many short, closely spaced strokes attached along the arch. Let them look feathery and roughly parallel rather than like a single solid mass. Filaments provide the main visible exchange surface; the American Physiological Society review describes them as the basic functional unit of gill tissue (The Multifunctional Fish Gill).
- Place the gill rakers. On the inner edge of the arch, draw shorter comb-like projections and label them “gill rakers.” They are associated with filtering, not the main exchange surface.
- Show water flow. Add arrows entering the mouth, passing across the gills, and leaving near the operculum. Water passes through the mouth, over the gills, and back into the environment, as described in the University of Hawaiʻi’s fish gas-exchange chapter.
- Label the drawing. Use short leader lines for operculum, gill arch, gill filaments, and gill rakers. Keep the lines from crossing one another or obscuring the structures.
How to show lamellae and gas exchange
Filaments carry rows of fine plate-like structures called lamellae, which increase the surface available for exchange. They are too small to represent clearly at the scale of a whole-fish diagram, so use a magnified inset: enlarge one filament, draw several thin plates along it, and label them “lamellae.” The Western Australia fish-gill worksheet uses a labeled diagram with these finer structures and blood-flow details.
If you include blood-flow arrows in the inset, distinguish oxygen-poor from oxygen-rich blood with a clear key or different line styles. The diagram should make clear that gills extract dissolved oxygen from water; avoid suggesting that the lamellae are separate organs or that water flows through the blood vessels.
Simple classroom diagram or detailed observational drawing?
| Approach | What to include | Best suited to |
|---|---|---|
| Simple classroom diagram | Recognizable head, operculum, one arch, repeated filaments, rakers, labels, and water-flow arrows. | Explaining the main parts and the direction water travels. |
| Detailed observational drawing | Preserve the specimen’s shape and proportions; add a magnified lamellae or blood-flow inset if useful, plus a scale or magnification note. | Recording an actual specimen and showing finer anatomical detail. |
Drawing from a specimen
When working from a specimen, prioritize what you can observe: keep the head and gill proportions faithful, and avoid adding details that are not visible unless you clearly present them as a separate explanatory inset. Cambridge International’s practical guidance calls for drawing gills in water and calculating magnification; follow the instructions for your specific practical and record the scale or magnification alongside the drawing (Cambridge International specimen paper mark scheme).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Labels for a fish-gill diagram
- Operculum: the external cover over the gills.
- Gill arch: the curved supporting structure.
- Gill filaments: repeated structures attached to the arch and forming the main exchange surface.
- Gill rakers: shorter comb-like structures along the inner edge of the arch.
- Lamellae: fine plates shown most clearly in a magnified inset.
- Water flow: arrows from the mouth, across the gills, and out near the operculum.
For a labeled anatomy reference, OpenStax’s gas-exchange chapter depicts gills attached to a columnar arch.
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