Fish Scales Under the Microscope
Fish Scales (Whole Mount), Cyprinus carpio
This is a fish scale mounted whole and stained with safranin. Fish scales have growth rings, a bit like tree rings, that scientists use to estimate a fish's age.
This is a whole mount of a fish scale from a common carp (Cyprinus carpio), stained red with safranin. Carp have cycloid scales, which are thin, bony plates with a smooth, rounded edge. Each scale grows outward from a central point called the focus, adding rings as the fish grows. Rings are spaced wider in fast summer growth and closer in slow winter growth, and scientists use these bands to estimate a fish's age. On this slide the stain is dark, so the rings are faint, but the thin, clear edges show where scales overlap like shingles on a roof.
What to look for
- Focus: The small central point where the scale first started growing.
- Circuli: Fine ridges that form rings around the focus.
- Annuli: Bands where the circuli are packed closer together, marking slower growth in winter.
- Radii: Lines or grooves running outward from the focus toward the edge.
- Scale edge: A smooth rounded edge in cycloid scales, or a toothed edge in ctenoid scales.
Questions and answers
How can you tell a fish's age from its scale?
Fish grow faster in summer than in winter, so the ridges on a scale are spread out in summer and crowded together in winter. Each crowded band, called an annulus, usually marks one year.
What is the difference between cycloid and ctenoid fish scales?
Cycloid scales have a smooth, rounded edge, while ctenoid scales have tiny teeth along their rear edge. Carp, the species listed for this slide, have cycloid scales.
- Category
- Vertebrates
- Scan magnification
- 20x
- Stain
- Safranin
Viewing this slide in class
This is a scan of a real prepared slide, not a simulation or a drawing. On StudyScope you can pan from the whole slide down to individual structures, always in focus, and measure them in real micrometers with the calibrated ruler. Present it live and every student screen follows your view and annotations. Students join with a room code on Chromebooks, iPads, or any browser, with no accounts.