scholarly journals Sexual selection by female choice prevents speciation reversal in a hybridizing trio of mormyrid fish in southern Africa: evidence from playback experiments of electric organ discharges

Behaviour ◽  
2014 ◽  
Vol 151 (12-13) ◽  
pp. 1703-1734 ◽  
Author(s):  
Daniela Schmid ◽  
Leo Bernd Kramer
Keyword(s):  
Southern Africa ◽  
Female Choice ◽  
Electric Organ ◽  
Hybrid Species ◽  
Main System ◽  
Mormyrid Fish ◽  
Okavango River ◽  
Species Specific ◽  
Electric Organ Discharges ◽  
Kwando River

We studied the question of whether or not female choice among variant forms of species-specific male advertising signals, electric organ discharges (EODs), is a factor in preventing panmixy in a parapatric sibling complex of three species of mormyrid fish, inhabiting three parallel rivers in southern Africa. The three species’ EODs are characteristically differentiated in waveform. The Upper Zambezi River is inhabited by Pollimyrus marianne Kramer, van der Bank, Flint, Sauer-Gürth & Wink, 2003, the Okavango River by P. castelnaui (Boulenger, 1911), and the smaller Kwando River in their middle by P. cuandoensis Kramer, van der Bank & Wink, 2013, which is their hybrid species of unidirectional origin. P. castelnaui females ( out of 5) and P. marianne females ( of 5) responded stronger to playback of the EODs of male conspecifics compared to those of male P. cuandoensis. Pollimyrus castelnaui and P. marianne females neither preferred nor discriminated against the male EODs of each other’s species, respectively (one exception). The single P. cuandoensis female available preferred a P. marianne male EOD over one of its own species, and was neutral in all other tests. This suggests that female resistance in the two main system species to P. cuandoensis male EODs is an evolved one, effectively limiting hybridization to the Kwando. The females of the two main system species, P. castelnaui and P. marianne, thus prevent panmixy in the Okavango and the Zambezi, respectively, thereby keeping up the three-sibling species complex by discriminating female choice against P. cuandoensis males in the Okavango-Kwando-Zambezi system.

scholarly journals Count and spark? The echo response of the weakly electric fish Gnathonemus petersii to series of pulses

2001 ◽  
Vol 204 (8) ◽  
pp. 1401-1412
Author(s):  
S. Schuster
Keyword(s):  
Electric Fish ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Simple Strategy ◽  
Mormyrid Fish ◽  
Pulse Type ◽  
After Effect ◽  
Electric Organ Discharges ◽  
Weakly Electric ◽  
Gnathonemus Petersii

Weakly electric fish of the pulse type electrolocate objects in the dark by emitting discrete electric organ discharges (EODs) separated by intervals of silence. Two neighbouring pulse-type fish often reduce the risk of discharging simultaneously by means of an ‘echo response’: one fish will respond to a neighbour's EOD with a discharge of its own following at a fixed short latency so that its EOD will occur long before the next EOD of its neighbour. Although working elegantly for two partners, this simple strategy should fail in larger groups because two fish could discharge in response to the same EOD of a third fish. Here, I show that the mormyrid fish Gnathonemus petersii could use a simple mechanism to reduce this problem. Individuals were stimulated with two closely spaced pulses, the second following so as to coincide with an echo given in response to the first. All the fish examined were able to respond more to the second pulse so that most of their echoes did not collide with the second pulse. An analysis was made of how echoing more to the second pulse depends on (i) the delay at which the stimulus followed the last spontaneous EOD, (ii) the spontaneous firing rate, (iii) the intensity of the stimulus, (iv) the number of stimulus pulses, (v) the interval between stimulus pulses, and (vi) the level of previous stimulation with double pulses. The results suggest that echoing more in response to the second pulse is probably because the first pulse causes an after-effect whose inferred properties would be compatible with the properties of the mormyromast afferences thought to be involved in the echo response.

Communication signals and sound production mechanisms of mormyrid electric fish

1999 ◽  
Vol 202 (10) ◽  
pp. 1417-1426 ◽  
Author(s):  
J.D. Crawford ◽  
X. Huang
Keyword(s):  
Sound Production ◽  
Electric Organ ◽  
Trunk Muscles ◽  
Sexually Dimorphic ◽  
Behavioral Experiments ◽  
Communication Signals ◽  
Species Specific ◽  
Electric Organ Discharges ◽  
Electrical Stimuli ◽  
Weakly Electric

The African weakly electric fishes Pollimyrus isidori and Pollimyrus adspersus (Mormyridae) produce elaborate acoustic displays during social communication in addition to their electric organ discharges (EODs). In this paper, we provide new data on the EODs of these sound-producing mormyrids and on the mechanisms they use to generate species-typical sounds. Although it is known that the EODs are usually species-specific and sexually dimorphic, the EODs of closely related sound-producing mormyrids have not previously been compared. The data presented demonstrate that there is a clear sexual dimorphism in the EOD waveform of P. isidori. Females have a multi-phasic EOD that is more complex than the male's biphasic EOD. In this respect, P. isidori is similar to its more thoroughly studied congener P. adspersus, which has a sexually dimorphic EOD. The new data also reveal that the EODs of these two species are distinct, thus showing for the first time that species-specificity in EODs is characteristic of these fishes, which also generate species-specific courtship sounds. The sound-generating mechanism is based on a drumming muscle coupled to the swimbladder. Transverse sections through decalcified male and female P. adspersus revealed a muscle that envelops the caudal pole of the swimbladder and that is composed of dorso-ventrally oriented fibers. The muscle is five times larger in males (14.5+/−4.4 microl, mean +/− s.d.) than in females (3.2+/−1.8 microl). The fibers are also of significantly larger diameter in males than in females. Males generate courtship sounds and females do not. The function of the swimbladder muscle was tested using behavioral experiments. Male P. adspersus normally produce acoustic courtship displays when presented with female-like electrical stimuli. However, local anesthesia of the swimbladder muscle muted males. In control trials, males continued to produce sounds after injection of either lidocaine in the trunk muscles or saline in the swimbladder muscles.

scholarly journals Sound production to electric discharge: sonic muscle evolution in progress in Synodontis spp. catfishes (Mochokidae)

2014 ◽  
Vol 281 (1791) ◽  
pp. 20141197 ◽  
Author(s):  
Kelly S. Boyle ◽  
Orphal Colleye ◽  
Eric Parmentier
Keyword(s):  
Sound Production ◽  
Electric Organ ◽  
Species Level ◽  
Electric Discharges ◽  
Swim Bladder ◽  
Auditory Thresholds ◽  
Sonic Muscle ◽  
Species Specific ◽  
Electric Organ Discharges ◽  
Muscle Evolution

Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. Within vertebrates, the capacity to produce regular coordinated electric organ discharges (EODs) has evolved independently in different fish lineages. Intermediate stages, however, are not known. We show that, within a single catfish genus, some species are able to produce sounds, electric discharges or both signals (though not simultaneously). We highlight that both acoustic and electric communication result from actions of the same muscle. In parallel to their abilities, the studied species show different degrees of myofibril development in the sonic and electric muscle. The lowest myofibril density was observed in Synodontis nigriventris , which produced EODs but no swim bladder sounds, whereas the greatest myofibril density was observed in Synodontis grandiops , the species that produced the longest sound trains but did not emit EODs. Additionally, S. grandiops exhibited the lowest auditory thresholds. Swim bladder sounds were similar among species, while EODs were distinctive at the species level. We hypothesize that communication with conspecifics favoured the development of species-specific EOD signals and suggest an evolutionary explanation for the transition from a fast sonic muscle to electrocytes.

scholarly journals The transcriptional correlates of divergent electric organ discharges in Paramormyrops electric fish

2019 ◽  
Author(s):  
Mauricio Losilla ◽  
Jason R. Gallant
Keyword(s):  
Gene Expression ◽  
Electric Fish ◽  
Phenotypic Diversity ◽  
Electric Organ ◽  
Mate Recognition ◽  
Species Group ◽  
Differentially Expressed ◽  
Cation Homeostasis ◽  
Species Specific ◽  
Electric Organ Discharges

AbstractBackgroundUnderstanding the genomic basis of phenotypic diversity can be greatly facilitated by examining adaptive radiations with hypervariable traits. In this study, we focus on a rapidly diverged species group of mormyrid electric fish in the genus Paramormyrops, which are characterized by extensive phenotypic variation in electric organ discharges (EODs). The main components of EOD diversity are waveform duration, complexity and polarity. Using an RNA-sequencing based approach, we sought to identify gene expression correlates for each of these EOD waveform features by comparing 11 specimens of Paramormyrops that exhibit variation in these features.ResultsPatterns of gene expression among Paramormyrops are highly correlated, and 3,274 genes (16%) were differentially expressed. Using our most restrictive criteria, we detected 71-144 differentially expressed genes correlated with each EOD feature, with little overlap between them. The predicted functions of several of these genes are related to extracellular matrix, cation homeostasis, lipid metabolism, and cytoskeletal and sarcomeric proteins. These genes are of significant interest given the known morphological differences between electric organs that underlie differences in the EOD waveform features studied.ConclusionsIn this study, we identified plausible candidate genes that may contribute to phenotypic differences in EOD waveforms among a rapidly diverged group of mormyrid electric fish. These genes may be important targets of selection in the evolution of species-specific differences in mate-recognition signals.

scholarly journals Evidence for mutual allocation of social attention through interactive signaling in a mormyrid weakly electric fish

2018 ◽  
Vol 115 (26) ◽  
pp. 6852-6857 ◽  
Author(s):  
Martin Worm ◽  
Tim Landgraf ◽  
Julia Prume ◽  
Hai Nguyen ◽  
Frank Kirschbaum ◽  
...  
Keyword(s):  
Cognitive Abilities ◽  
Electric Fish ◽  
Electric Organ ◽  
Social Attention ◽  
Weakly Electric Fish ◽  
Vertebrate Lineage ◽  
Discharge Patterns ◽  
Species Specific ◽  
Electric Organ Discharges ◽  
Weakly Electric

Mormyrid weakly electric fish produce electric organ discharges (EODs) for active electrolocation and electrocommunication. These pulses are emitted with variable interdischarge intervals (IDIs) resulting in temporal discharge patterns and interactive signaling episodes with nearby conspecifics. However, unequivocal assignment of interactive signaling to a specific behavioral context has proven to be challenging. Using an ethorobotical approach, we confronted single individuals of weakly electricMormyrus rume proboscirostriswith a mobile fish robot capable of interacting both physically, on arbitrary trajectories, as well as electrically, by generating echo responses through playback of species-specific EODs, thus synchronizing signals with the fish. Interactive signaling by the fish was more pronounced in response to a dynamic echo playback generated by the robot than in response to playback of static random IDI sequences. Such synchronizations were particularly strong at a distance corresponding to the outer limit of active electrolocation, and when fish oriented toward the fish replica. We therefore argue that interactive signaling through echoing of a conspecific’s EODs provides a simple mechanism by which weakly electric fish can specifically address nearby individuals during electrocommunication. Echoing may thus enable mormyrids to mutually allocate social attention and constitute a foundation for complex social behavior and relatively advanced cognitive abilities in a basal vertebrate lineage.

scholarly journals The transcriptional correlates of divergent electric organ discharges in Paramormyrops electric fish

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Mauricio Losilla ◽  
David Michael Luecke ◽  
Jason R. Gallant
Keyword(s):  
Gene Expression ◽  
Electric Fish ◽  
Phenotypic Diversity ◽  
Electric Organ ◽  
Mate Recognition ◽  
Species Group ◽  
Differentially Expressed ◽  
Cation Homeostasis ◽  
Species Specific ◽  
Electric Organ Discharges

Abstract Background Understanding the genomic basis of phenotypic diversity can be greatly facilitated by examining adaptive radiations with hypervariable traits. In this study, we focus on a rapidly diverged species group of mormyrid electric fish in the genus Paramormyrops, which are characterized by extensive phenotypic variation in electric organ discharges (EODs). The main components of EOD diversity are waveform duration, complexity and polarity. Using an RNA-sequencing based approach, we sought to identify gene expression correlates for each of these EOD waveform features by comparing 11 specimens of Paramormyrops that exhibit variation in these features. Results Patterns of gene expression among Paramormyrops are highly correlated, and 3274 genes (16%) were differentially expressed. Using our most restrictive criteria, we detected 145–183 differentially expressed genes correlated with each EOD feature, with little overlap between them. The predicted functions of several of these genes are related to extracellular matrix, cation homeostasis, lipid metabolism, and cytoskeletal and sarcomeric proteins. These genes are of significant interest given the known morphological differences between electric organs that underlie differences in the EOD waveform features studied. Conclusions In this study, we identified plausible candidate genes that may contribute to phenotypic differences in EOD waveforms among a rapidly diverged group of mormyrid electric fish. These genes may be important targets of selection in the evolution of species-specific differences in mate-recognition signals.

Individual and sex specificity in the electric organ discharges of breeding mormyrid fish (Pollimyrus isidori)

1992 ◽  
Vol 164 (1) ◽  
pp. 79-102 ◽  
Author(s):  
J. D. Crawford
Keyword(s):  
Function Analysis ◽  
Electric Organ ◽  
Sampling Period ◽  
Relative Amplitude ◽  
Spectral Cues ◽  
Mormyrid Fish ◽  
Sex Specificity ◽  
The Stability ◽  
Electric Organ Discharges ◽  
Multivariate Discriminant

I monitored the electric organ discharges (EODs) of 14 Pollimyrus isidori, (Cuvier and Valenciennes) during an artificially induced breeding season, to examine sex and individual differences in reproductive fish. EODs were repeatedly recorded over an 11-day period to ascertain the stability of each individual's EOD and to make a quantitative assessment of sex differences. Within days, I found the individual's EOD to be constant from one EOD to the next. Over the 11-day sampling period, individuals were also quite stable and exhibited only slight changes in EOD duration and relative amplitude of the phases of the waveform. I found that the differences between individuals of the same sex were highly significant in measures of EOD duration and in measures of the relative amplitude of the phases. Differences between the sexes were also highly significant in relative amplitude but were not significant in duration. In a multivariate discriminant function analysis, I have found that individual fish can be correctly classified on the basis of temporal, relative amplitude and spectral cues in the EOD, despite slight changes in these parameters with time. The EOD exhibits characteristics of a good signature in the context of an information system.

scholarly journals THE SENSING OF ELECTRICAL CAPACITANCES BY WEAKLY ELECTRIC MORMYRID FISH: EFFECTS OF WATER CONDUCTIVITY

1993 ◽  
Vol 181 (1) ◽  
pp. 157-173 ◽  
Author(s):  
G. Von Der Emde
Keyword(s):  
Detection Threshold ◽  
Electric Organ ◽  
Weakly Electric Fish ◽  
Water Conductivity ◽  
Capacitance Detection ◽  
Mormyrid Fish ◽  
Electric Organ Discharges ◽  
Weakly Electric ◽  
Gnathonemus Petersii ◽  
A And B Cells

Weakly electric fish can perceive electric properties of objects by monitoring the responses of their epidermal electroreceptors (mormyromasts) to their own electric organ discharges (EOD), a process known as active electrolocation. Mormyrid fish can distinguish capacitative from resistive properties of objects. It is mainly animate objects that possess capacitative properties. Water conductivity is a critical environmental factor that varies widely from season to season and has strong effects on the emitted EOD. The two goals of this study were: (1) to investigate the ability of Gnathonemus petersii to detect the properties of capacitative objects in waters of different ion content and (2) to test a recently formulated hypothesis which states that the detection of the features of a capacitative object depends on a comparison of the inputs from the two types of mormyromast primary afferents. Individuals of G. petersii were tested in a conditioned electrolocation procedure. With increasing water conductivities from 50 to 1100 muS cm-1, EOD amplitude decreased and the detection threshold for small capacitances increased. At 50 muS cm-1, the smallest detectable capacitative value was below 0.5 nF; this increased to about 20 nF at 800 muS cm-1. When conductivity approached about 1000 muS cm-1, fish were no longer able to electrolocate, probably because of the reduction in EOD amplitude at high conductivities. The fish's ability to discriminate a capacitative object unequivocally from every resistive object was also tested at different conductivities. Below about 800 muS cm-1, all fish could do so. Above that conductivity, however, fish could no longer discriminate between capacitative and resistive objects of similar impedance, although they could still discriminate between objects of different impedances. The two types of receptor afferents (from the ‘A’ and ‘B’ cells) of mormyromast electroreceptor organs have different thresholds, with the B afferents being more sensitive. I suggest that only the B receptor cells remain active at about 800 muS cm-1, when the EOD amplitude is much reduced. With input from B afferents only, an unambiguous capacitance detection was no longer possible. This supports the hypothesis that capacitance detection is achieved by comparing inputs of A and B electroreceptor cells.

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