The Shape of Water

Hello all welcome back to the blog!  In today’s blog I will be talking about mating behaviors in electric fish and how climate change may affect breeding success in these species. Mating behaviors can involve many different types of social interactions: They can include a variable number of mates (Brown and Gordon 2008). Within these mating systems you can have intrasexual and intersexual competition.  Intrasexual competition is when members of the same sex compete from a mate and in intersexual competition is an interaction between different sexes usually defined by mate choice (Brennan 2010). One of my favorite examples of intersexual competition is in peacocks. In peacocks’ females pick their mate by counting the number of  “eyes” on their tail. This is cool because it shows that peacocks have numerical competency, which is a cognitive ability.  Electric fish typically demonstrate intrasexual sexual competition between males.

A study done by Cuddy and colleagues investigated how changing in 11-ketotestosterone (11-KT) levels and electric organ discharge frequency (EODf) are affected by mating behavior in A. leptorhynchus, a weakly electric fish (Cuddy et al. 2012). Cuddy believed that 11-KT levels would give insight on courtship behaviors in electric fish.  They concluded that higher EODf levels in males were strongly correlated to higher 11-KT levels (Cuddy et al. 2012). These findings are important since no one before them have investigated the physiological mechanism behind mating in electric fish.  

Many electric fish like Gymnotiformes breed during the rainy season because water levels are at its highest which results in low water conductivity (Silva et al. 2006). The study done by Silva examined the effect of water temperature on EOD waveform in B. pinnicaudates which showed that when water temperatures are increases EOD transmission slows down thus making communication to possible mates less effective (Silva et al. 2006).  This fact is alarming, since global climate change will inedibility increase the water temperature to levels beyond what these fish are used to.  On the flip side, it is possible that climate change will increase the amount of precipitation which may simulate longer breeding seasons for these fish.  The study by Silva also hinted on the pacemaker nucleus playing a role in modulating hormones in electric fish which complies with the Cuddy study on 11-ketotestrone hormones affecting  the waveform frequency of the EOD (Cuddy et al. 2012).  

Courtship between a male and female Electric Fish

Recorded and analyzed in the Hopkins Lab by Kevin Gardner, Brian Isett, Tom Kraft Garry Harned., Electric fish courtingCC BY-SA 3.0

Territorial aggression is found in many organisms including electric fish. A territory is an area of land that an organism defends against other organisms.  In most cases the territory is not large since it takes a large amount of energy to defend an area. In a study done by Jalabert and colleagues they investigated the effect of territorial aggression in G. omaronrum (Jalabert et al. 2015). They found out that these species of electric fish don’t exhibit a bias toward sex unless it was during the mating season (Jalabert et al. 2019). During the mating season males would have higher K-11 levels and would not aggressively attack female conspecifics (Jalabet et al. 2019).  

Mating in electric fish is an interesting topic and I believe that more work regarding 11-ketotestosterone would be essential in painting the full picture behind mating in electric fish. Next time we will be exploring leaders in electric fish research!

Literature Cited:

1. Brown MJF, Gordon DM. Social Behavior. In: Jørgensen SE, Fath BD, editors. Encyclopedia of Ecology. Oxford: Academic Press; 2008 [accessed 2019 May 10]. p. 3261–3264. doi:10.1016/B978-008045405-4.00029-X

2. Cuddy M, Aubin-Horth N, Krahe R. Electrocommunication behaviour and non invasively-measured androgen changes following induced seasonal breeding in the weakly electric fish, Apteronotus leptorhynchus. Hormones and Behavior. 2012;61(1):4–11. doi:10.1016/j.yhbeh.2011.09.003

3. Jalabert C, Quintana L, Pessina P, Silva A. Extra-gonadal steroids modulate non-breeding territorial aggression in weakly electric fish. Hormones and Behavior. 2015;72:60–67. doi:10.1016/j.yhbeh.2015.05.003

4. Sexual Selection | Learn Science at Scitable. [accessed 2019 May 10].

5. Silva A, Perrone R, Macadar O. Environmental, seasonal, and social modulations of basal activity in a weakly electric fish. Physiology & Behavior. 2007;90(2):525–536. (Includes a Special Section on Chronobiology Aspects of the Sleep–Wake Cycle and Thermoreregulation). doi:10.1016/j.physbeh.2006.11.003

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