1. Osmoregulation in fish
Martin G Greenwell, DVM, Johanna Sherrill, DVM, MS, Leigh A Clayton, DVM 
Veterinary Clinics: Exotic Animal Practice 
Volume 6, Issue 1, Pages (January 2003)
DOI: /S (02)00021-X

2. Fig. 1
Electrolyte fluxes in a typical marine fish. (From Stoskopf MK. Clinical physiology. In: Stoskopf MK, editor. Fish medicine. Philadelphia: W.B. Saunders; p. 48–61.)
Veterinary Clinics: Exotic Animal Practice 2003 6, DOI: ( /S (02)00021-X)

3. Fig. 2
Electrolyte fluxes in a typical freshwater fish. (From Stoskopf MK. Clinical physiology. In: Stoskopf MK, editor. Fish medicine. Philadelphia: W.B. Saunders; p. 48–61.)
Veterinary Clinics: Exotic Animal Practice 2003 6, DOI: ( /S (02)00021-X)

4. Fig. 3
The rectal gland of sharks. (From Stoskopf MK. Clinical physiology. In: Stoskopf MK, editor. Fish medicine. Philadelphia: W.B. Saunders; p. 48–61.)
Veterinary Clinics: Exotic Animal Practice 2003 6, DOI: ( /S (02)00021-X)