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

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

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

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

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

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

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

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

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

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

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.

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

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.

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

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.

Applications and Value to current research

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

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

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

Elasmobranchii

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).

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

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

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

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. 2012. 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. 2012. 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: 10.1111/j.1095-8649.2012.03448.x Maclver, M.A. 2001. Prey-capture behavior in gymnotid electric fish: motion analysis and effects of water conductivity. Journal of experimental biology, 204: 543. Martin, R. A. 2005. Conservation of freshwater and euryhalineelasmobranchs: a review.Journal of the Marine Biological Association of the United Kingdom, 85: 1049- 1073. 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: 10.1111/j.1095-8649.1992.tb02553.x

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