1. Osmoregulation

2. The problem of osmolarity:
salt water
35 ppt
fresh water
0-5 ppt

3. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic
fishes need to balance their internal osmotic environment
increase/retain solutes, or decrease internal water
- they pee a lot
decrease/shed solutes, or increase internal water
- they drink a lot

4. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic
fishes are either:
stenohaline - tolerant of limited range of osmolarity
euryhaline - tolerant of wide range (where is this useful?)
diadromous – osmo-adaptation changes during lifetime

5. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
maintain isosmotic conditions

6. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
2. salt supplementers (marine elasmobranches and coelacanths)
high urea content and TMAO (trimethylamine oxide)
low permeability to Na+, Cl-
excrete excess Na+, Cl-

7. How fish deal with being osmotic misfits
3. hyposmotics (marine teleosts)
tend to lose water, replace by drinking
gill cells pump in water, not salts

8. How fish deal with being osmotic misfits
4. hyperosmotics (freshwater fishes)
excrete large volumes of water
gill chloride cells pump in salts
often euryhaline (striped bass, tilapia, drum)

9. Diadromous fishes – experience salt and freshwater
environments during their life

10. Diadromous fishes anadromous - Pacific salmon, lamprey, shad
fresh water
salt water

11. Diadromous fishes fresh water salt water
anadromous - Pacific salmon, lamprey, shad
fresh water
salt water
behavioral change (drinking)
changes in kidney function
metamorphosis (smoltification)
– cued to photoperiod, lunar cycle

12. Diadromous fishes anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous, adfluvial)
- reversion of salt-water tolerance
fresh water

13. Diadromous fishes anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous, adfluvial)
catadromous - eels
pre-leptocephalus
larva
mature eel
leptocephalus
silver eel
elver, yellow eel
glass
eel

14. The cost of osmoregulation
Kijewska et al. (2016). Adaptation to salinity in Atlantic cod from different regions of the Baltic Sea. J. Experimental Marine Biology and Ecology, 478, 62–67.

15. The cost of osmoregulation
Birrer et al.(2012). Salinity change impairs pipefish immune defense. Fish and Shellfish Immunology, 33(6), 1238–1248.

16. Chemoreception:
taste and smell

17. Taste and smell: communication
individual recognition, especially of mates
species recognition, esp. schooling species
offspring recognition (cichlids)
scent mark territories (gobies)
dominant-subordinate relationships
aggression-inhibiting pheromone produced by bullheads
living in groups

18. Taste (= chemoreception at close range)
taste organs can reside on exterior surfaces:
barbels of bottom-dwelling fishes
lips of suckers
over much of body of ictalurids

19. Olfaction (= chemoreception at "long" range/gradients)
more sensitive than taste
used for:
food finding
migration, e.g., salmon
intra, interspecific communication

20. Olfaction (= chemoreception at "long" range/gradients)
more sensitive than taste
used for:
food finding
migration, e.g., salmon
intra, interspecific communication
semiochemical – chemical used for communication
pheromone – elicits social response in same species
kairomone – benefits receiver, not emitter – between species
e.g., food, scent, necromone

21. Sea lamprey, Petromyzon marinus
Sea lamprey do not (cannot) home to natal stream; and, only get one chance to spawn, so need a cue to find a good stream for spawning

22. Sea lamprey, Petromyzon marinus
Petromyzonol sulfate
Migratory pheromone emitted by larval lamprey – induces upstream movement of adults

23. Sea lamprey sex pheromone
3kPZS
Sea lamprey sex pheromone
Dr. Weiming Li, Michigan State University

24. Olfaction (= chemoreception at "long" range/gradients)
“Schreckstoff” alarm pheromones (Ostariophysi):
Gonorynchiformes Cypriniformes Characiformes Gymnotiformes Siluriformes
Note: ‘Shreck’ is German word for ‘scary’, thus ‘scary stuff’

25. Olfaction (= chemoreception at "long" range/gradients)
“Schreckstoff” alarm pheromones (Ostariophysi)
- originate in specialized ‘club’ cells in skin,
released when fish is damaged
effect is to alert other conspecifics
- potent
- highly specific (generally species-specific)
- can pass through gut of predators intact, as warning

26. Other cutaneous senses
touch
few detectors – shark fins; head, barbels of bullheads
mating behaviors (use of breeding tubercules)
parent-young communication in catfish, cichlids,
damselfishes

27. Other cutaneous senses
temperature
teleost cutaneous temp. sensitivity to 0.03C change
can distinguish rise from a fall in temperature
elasmobranchs detect temperature change with
ampullae of Lorenzini