1. Electroreception in Fish
The advantages & function of electroreception in various species of fish
Revett Saffo
Molli Simpson
Anthony Baldrica

2. Exploration Use in communication
Patterns of electroreception among fishes
Including variations in differing environments
Electroreception Detection
Conservation

3. Definition
Electroreception: a biological ability to perceive natural electrical stimuli.
Often attributed to aquatic vertebrates

4. Functions of Electroreception
Communication
Predation
Awareness
One example of an aquatic animal using electroreception comes from the Scyliorhinus canicula, more commonly known as small spotted catshark

5. Hammerhead Shark The Hammerhead shark is an electroreceptive species
An example of a far- evolved electroreceptive fish with dense pore abundance

6. Species of Interest Subclass: Elasmobranchii African Electric Catfish
Small Spotted Catshark
African Electric Catfish
Malapterusrus electricus
South African Bulldog
Mormyrid fish: Marcusenius marcolepidotus
Marcusenius altisambesi & Mormyrus rum

7. Support from Literature: Temporal patterning of electric organ discharges in the African electric catfish, Malapterurus electricus (Rankin and Moller 1992)
Showed variations in electric organ discharge (EOD- electric discharge generated by the electric organ) depending on the fish that Malapterurus electricus (electric catfish) was around
Based on previous experience with the other fish, EOD varies in pattern and pulses
Environment, time of exposure, and predator/prey relationships effected the EOD response of M. electricus

8. Carassius auratus (goldfish) and Oreochromis niloticus (tilapia)
Avoided M. electricus
Contact was brief since C. auratus and O. niloticus fled when M. electricus was present
Polypterus palmas (bichir)
Both are bottom dwellers
P. palmas freezes in response to M. electricus
Contact time is longer
Long duration EOD
Brief trains with long-train intervals
Clarias (airbreathing catfishes)
Predator
High EOD
Great number of EOD pulses
High frequency
Accompanied with visual displays

9. EOD Volley Types Disturbance Defensive Feeding
Responses to brief encounters
C. auratus, O. niloticus, and P. palmas
Defensive
Responses to attacks
Clarias
Feeding
High and long frequency when feeding

10. Support from Literature: Electrocommunication behaviour during social interactions in two species of pulse-type weakly electric fishes  (Mormyridae) (Gebhardt et al, 2012)
Electroreception has been adapted for communication behaviors in mormyrids
Resting behaviors:
Mormyrus rume
Decrease EOD
Remain in individual shelters, not visible to others
Marcusenius altisambesi
Found in large groups
Both species exhibited EOD synchronization in resting conditions
Figure 2. Species-specific electric organ discharge (EOD) waveform of (a)Marcusenius altisambesi and (b) Mormyrus rume recorded head-to-tail. Both EODs are biphasic with a positive (P) phase followed by a negative (N) phase. Note shorter duration of the M. altisambesi EOD

11. Echoing
In general, when fishes in groups communicate via electroreception a echo is produced
The echo has various functions including aggressive displays, courtship signals, and jamming avoidance
M. rume and M. altisambesi respond to the echo produced
Echoing is advantageous when EODs are colliding since fishes will respond by not overlapping EODs
A fish produces an EOD right after its neighbor where the EOD occurs during a time when the neighbor will be silent and the other wont produce another EOD and so no overlap occurs
Echo is a kind of vibration
An echo response was given when one fish followed electrically the EODs of another fish with a short time delay of no longer then 30 ms. 
M. altisambesi never showed echo responses during agonistic situations and in M. rume the echoing occurrence was low which may entail that echo responses may serve to co-ordinate group foraging behavior
If none of the fishes were to use the non-overlap technique then only a very small percent of the EODs that M. altisambesi and M. rume conduct will overlap.

12. Synchronization Definition:
“Temporal correlation of electric discharges between individuals of a group is a complex social interaction, which both species displayed during foraging.” (Gebhardt et al., 2012)
M. altisambesi showed positive signaling between group members
M. rume showed similar mechanism where both fishes simultaneously emit similar EOD patterns
In M. rume a similar mechanism happens where both fishes in an agonistic situation simultaneously emit similar EOD patterns with bursts of short increases in duration

13. Fixed-order Signaling
Different than synchronization
Rather then occurring between two fishes (synchronization), this occurs between the whole group
Three or more fish repeat order of their EODs relative to one another more than four times in a row
Further decreases overlap because each fish would have its own time to conduct their EOD
EOD may not be a problem when looking at only two fishes, but looking at groups it is advantageous for fishes to have their own time to eliminate overlap.
M. altisambesi implies that the species has a stronger group cohesion supported by different EOD
Shorter EODs are advantageous because it decreases the probability of EODs overlapping.

14. Fixed-order Signaling
a. Marcusenius altisambesi
Fixed-order signalling of (a) four Marcusenius altisambesi and (b) four Mormyrus rume (b) during a 250 ms interval. Electric oragan discharges (EOD) are colour coded with each colour representing the occurrence of an EOD of one individual. Each repetition event is marked by a bracket. (a) Marcusenius altisambesi repeated the fixed order of EODs 19 times, while (b) M. rume repeated their fixed order six times.
b. Mormyrus rume

15. Relationship to Ecology
M. rume used a discharge behavior that functioned as an agonistic signal.
M. altisambesi are more social and less aggressive then M. rume evident by the lack of EOD aggressiveness pattern.
M. altisambesi sociality may be related to its ecology which live in streams where floods increase the amount of potential habitat area.
Thus, this entails that competition for spawning sites may decrease which decreases aggressive interactions. M. rume has not adapted this type of behavior which means that aggressiveness increases in the species for territories and mates.

16. Applications and Value to current research

17. How is electroreception related to biodiversity?
Conservation efforts exist in fishes that possess electroreception
Gymnotiform knife fishes
Elasmobrachii
Sea Lamprey
Electro-receptive fish important to biodiversity

18. Gymnotidae (electroreceptive fish)
Use electrosensory organs to detect prey within close range (Maclver, 2001)
Implications
water conductivity affects prey capture via electrosensory organs
Food web relies on predator-prey interaction
Maclver

19. Sea Lamprey control Sea Lamprey (petromyzonmarinus)
Highly predatory, invasive species of Great Lakes
Important species in conservation management

20. Elasmobranchii

21. Elasmobranchii K-selected
Slow grow, long gestation, late maturity, and low fecundity
Highly trophic
A study done by R.A Martin, 2005 suggests some species susceptible to endangerment or extinction
Species with limited geographic ranges prone to extinction
Species who breed in sea at risk to be endangered
“As K-selected creatures that compete for aquatic resources against humans who widely regard them to be dangerous vermin, freshwater and euryhalineelasmobranchs present significant challenges to conservation biologists” (Martin, 2005).

22. Tools for Conservation in Electroreceptive fish
ERA’s (ecological risk assessment) (Gallagher et al., 2012)
Behavior
Movement
Migration
Fishing efforts and exploitation
Molecular tools (Dudgeon et al., 2012)
Genetic applications
Help understand needed conservation management with use of molecular genetics
Dudgeon

23. Summary Increased capabilities due to electroreception
Communication & Awareness
Synchronization
Echoing
Fixed-order Signaling
Predation
Environment & time of exposure effect EOD
EOD types: Disturbance, Defense, & Feeding
Conservation efforts exist
Important to biodiversity
Important to food web 23

24. Future Research M. altisambesi and M. rume’s echoing techniquie
Not properly explained
(May decrease amount of EOD collision)
Elasmobranch’s pore abundance
Correlation to feeding ecology and predator avoidance not fully understood
Conservation of Elasmobranchii
Electroreceptive behavior’s relationship to life strategies and thus, conservation

25. References
Dudgeon, C. L., Blower, D. C., Broderick, D., Giles, J. L., Holmes, B. J., Kashiwagi, T., Krück, N. C., Morgan, J. A. T., Tillett, B. J. and Ovenden, J. R A review of the application of molecular genetics for fisheries management and conservation of sharks and rays. Journal of Fish Biology, 80: 1789–1843.
Gallagher, A. J., Kyne, P. M. and Hammerschlag, N Ecological risk assessment and its application to elasmobranch conservation and management. Journal of Fish Biology, 80: 1727– 1748.
Gebhardt, K., Böhme, M. and von der Emde, G. (2012), Electrocommunication behaviour during social interactions in two species of pulse-type weakly electric fishes (Mormyridae). Journal of Fish Biology. doi:  /j x
Maclver, M.A Prey-capture behavior in gymnotid electric fish: motion analysis and effects of water conductivity. Journal of experimental biology, 204: 543.
Martin, R. A Conservation of freshwater and euryhalineelasmobranchs: a review.Journal of the Marine Biological Association of the United Kingdom, 85:
Rankin, C. H. and Moller, P. (1992), Temporal patterning of electric organ discharges in the African electric catfish, Malapterurus electricus (Gmelin). Journal of Fish Biology, 40: 49–58. doi:  /j tb02553.x

26. Any Questions?