FIGURE 2.

(a) Anatomical landmarks (30 points) used to measure the head shape of Arctic charr. Photo from male Dwarf morph, which was a genetically pure individual (q = 0.85). Landmarks used for head shape analysis: 1. Central point of the eye, 2. Dorsal extreme of bony orbit of the eye, 3. Posterior extreme of bony orbit of the eye, 4. Anterior extreme of bony orbit of the eye, 5. Ventral extreme of bony orbit of the eye, 6–7. Perpendicular line following landmarks 1, 2 and 5, 8. Posterior point of the upper jaw, 9. Central point of the closed mouth, 10. Anterior point of the upper jaw, 11. Anterior point of the lower jaw, 12. Ventral extreme of nostril, 13. Dorsal extreme of nostril, 14. Anterior point of nostril, 15. Posterior point of nostril, 16. Central point of nostril, 17. Perpendicular line following landmarks 14, 15 and 16, 18. Starting point of the line of preoperculum, 19. Upper point of the preoperculum, 20. Point of maximum curvature of the preoperculum, 21 Lower point of preoperculum, 22. Upper point of the operculum, 23. Posterior point of the bony operculum, 24. Point of curvature of the operculum, 25. Lower point of operculum, 26. Perpendicular line following landmark 20 to the bottom of the fish, 27. Middle point between landmarks 18 and 28, 28. Starting point of the line of operculum, 29. Socket of the eye, 30. Perpendicular line from landmark 29. (b) Dorsal, (c) lateral and (d) ventral view of the brain, illustrating the five brain regions studied (1: olfactory bulb, 2: telencephalon, 3: optic tectum, 4: cerebellum, 5: hypothalamus). For each brain region, the length (L), height (H), and width (W) were measured. (e) Olfactory lamellae of Arctic charr and illustration of olfactory organs with lamellae and olfactory nerves attached with the olfactory bulb, which is connected with the telencephalon