Hormone-induced and maturational changes in electric organ discharges and electroreceptor tuning in the weakly electric fishApteronotus

Jh, Meyer; Leong, May Ying; Ch, Keller

doi:10.1007/bf00613028

Cited by 103 publications

(71 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast to Sternopygus, Apteronotus leptorhynchus (Meyer et al, 1987;Schaefer and Zakon, 1996) lower their EOD frequency in response to estradiol implantation. Preliminary evidence suggests that Apteronotus albifrons and Eigenmannia sp.…”

Section: Estrogen As a Modulator Of The Eodmentioning

confidence: 76%

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

1997

View full text Add to dashboard Cite

Many species of electric fish emit sexually dimorphic electrical signals that are used in gender recognition. In Sternopygus, mature females produce an electric organ discharge (EOD) that is higher in frequency and shorter in pulse duration than that of mature males. EOD pulse duration is determined by ion currents in the electrocytes, and androgens influence EOD pulse duration by altering the inactivation kinetics of the electrocyte sodium current. We examined whether estrogen modulates the female-specific EOD and, if so, whether it regulates EOD pulse duration by acting on the same androgen-sensitive ion current in the electrocytes. We implanted gonadectomized Sternopygus with either empty SILASTIC capsules (control), one capsule filled with estradiol-17␤ (E 2 ; low dose), or three capsules of E 2 (high dose). Twelve days after implantation, E 2 -treated fish had plasma E 2 levels ϳ3.3-fold (low dose) or ϳ7.1-fold (high dose) higher than controls. After implantation, both E 2 -treated groups had higher EOD frequency and shorter EOD pulse duration than controls and their own preimplantation values. Through immunocytochemistry, we identified immunoreactive estrogen receptors in the nuclei of electrocytes, indicating that these cells are directly responsive to estrogen. In addition, voltage-clamp studies showed that E 2 affected the electrocyte ion currents kinetics: the sodium inactivation time constant was significantly lower in E 2 -treated fish than in controls. Thus, sexual dimorphism in the electrocommunication signal results, at least in part, from estrogens and androgens acting in opposite directions on the same ion current in the electrocytes. Key words: estrogen; sodium current; electric fish; estrogen receptor; electric organ; SternopygusIn most vertebrates, steroids have potent influences on the expression of sexually dimorphic reproductive behaviors such as courtship and mating (Kelley, 1988). Many studies have shown that regions of the nervous system and the effector organs that control reproductive behaviors have specific receptors for sex steroids, and more recently researchers have found that steroids can induce changes in the overall extracellular electrical activity in brain nuclei (Becker et al., 1992). Our understanding, however, of how steroids alter the electrical properties in specific, behaviorally relevant cells is still limited.Recent studies on the sexually dimorphic electrocommunication signal of a weakly electric fish, Sternopygus, have demonstrated that androgens alter specific ionic conductances in excitable cells involved in reproductive behavior (Ferrari and Zakon, 1993;Zakon, 1993;Ferrari et al., 1995). This has been possible because the neural circuits and effector cells underlying this behavior are relatively simple and discrete (Bullock and Heiligenberg, 1986), and some cells, the electrocytes of the electric organ, are large and accessible for recording changes in membrane properties by voltage clamp (Ferrari and Zakon, 1993;Ferrari et al., 1995;McAnelly and Zakon, 1996).In ...

show abstract

Section: Estrogen As a Modulator Of The Eodmentioning

confidence: 76%

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

1997

View full text Add to dashboard Cite

show abstract

“…Even though EOD frequency of wave-type fish can be extremely stable on time scales of hours, it can be modulated rapidly and transiently under the control of pre-pacemaker nuclei for purposes of communication (Metzner, 1999;Zakon et al, 2002). Slower changes on the time scale of development and sexual maturation have been shown to be under the control of steroid hormones (Meyer et al, 1983;Meyer et al, 1987;Zakon et al, 1991;Dunlap and Zakon, 1998), affecting voltage-gated sodium and potassium channels in the electrocytes (Ferrari et al, 1995;McAnelly and Zakon, 2007). Given that the kinetics of sodium and potassium Zakon, 2007), it appears likely that the kinetics are matched for a given EOD frequency to minimize sodium waste current (Hasenstaub et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

Energetic constraints on electric signalling in wave-type weakly electric fishes

Reardon

Parisi

Krahe

et al. 2011

Journal of Experimental Biology

View full text Add to dashboard Cite

SUMMARY Gymnotiform weakly electric fishes generate electric organ discharges (EODs) and sense perturbations of the resulting electric field for purposes of orientation, prey detection and communication. Some species produce oscillatory (‘wave-type’) EODs at very high frequencies (up to 2 kHz) that have been proposed to be energetically expensive. If high-frequency EODs are expensive, then fish may modulate their EOD frequency and/or amplitude in response to low-oxygen (hypoxic) stress and/or compensate for costs of signalling through other adaptations that maximize oxygen uptake efficiency. To test for evidence of an energetic cost of signalling, we recorded EOD in conjunction with metabolic rates, critical oxygen tension and aquatic surface respiration (ASR90) thresholds in Apteronotus leptorhynchus, a species found in high-oxygen habitats, and Eigenmannia virescens, a species more typically found in low-oxygen waters. Eigenmannia virescens had a lower mean ASR90 threshold and critical oxygen tension compared with A. leptorhynchus, consistent with field distributions. Within each species, there was no evidence for a relationship between metabolic rate and either EOD frequency or amplitude under normoxia, suggesting that there is no significant direct metabolic cost associated with producing a higher frequency EOD. However, when exposed to progressive hypoxia, fish generally responded by reducing EOD amplitude, which may reduce energetic costs. The threshold at which fish reduced EOD amplitude tended to be lower in E. virescens, a pattern consistent with higher tolerance to hypoxic stress. The results of this study suggest that wave-type fish reduce their EOD amplitude to reduce direct energetic costs without reducing metabolic rate under hypoxia.

show abstract

“…Apteronotid species vary in both the magnitude and direction of sexual dimorphism in EODf. The brown ghost knifefish (Apteronotus leptorhynchus) has a robust sex difference in EODf in the opposite direction to that of other knifefishes; males have higher EODf than females Hagedorn and Heiligenberg, 1985;Meyer et al, 1987). In contrast, male black ghost knifefish (Apteronotus albifrons) have lower EODfs than females .…”

Section: Sex Differences In Eod Frequencymentioning

confidence: 99%

Evolution and hormonal regulation of sex differences in the electrocommunication behavior of ghost knifefishes (Apteronotidae)

2013

Journal of Experimental Biology

View full text Add to dashboard Cite

SummaryThe ghost knifefishes (family Apteronotidae) are one of the most successful and diverse families of electric fish. Like other weakly electric fish, apteronotids produce electric organ discharges (EODs) that function in electrolocation and communication. This review highlights the diversity in the structure, function and sexual dimorphism of electrocommunication signals within and across apteronotid species. EOD frequency (EODf) and waveform vary as a function of species, sex and/or social rank. Sex differences in EODf are evolutionarily labile; apteronotid species express every pattern of sexual dimorphism in EODf (males>females; males

show abstract

Hormone-induced and maturational changes in electric organ discharges and electroreceptor tuning in the weakly electric fishApteronotus

Cited by 103 publications

References 30 publications

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Energetic constraints on electric signalling in wave-type weakly electric fishes

Evolution and hormonal regulation of sex differences in the electrocommunication behavior of ghost knifefishes (Apteronotidae)

Contact Info

Product

Resources

About