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Behavioral ecology, endocrinology and signal reliability of electric communication.

ABSTRACT: The balance between the costs and benefits of conspicuous animal communication signals ensures that signal expression relates to the quality of the bearer. Signal plasticity enables males to enhance conspicuous signals to impress mates and competitors and to reduce signal expression to lower energetic and predation-related signaling costs when competition is low. While signal plasticity may benefit the signaler, it can compromise the reliability of the information conveyed by the signals. In this paper we review the effect of signal plasticity on the reliability of the electrocommunication signal of the gymnotiform fish Brachyhypopomus gauderio. We (1) summarize the endocrine regulation of signal plasticity, (2) explore the regulation of signal plasticity in females, (3) examine the information conveyed by the signal, (4) show how that information changes when the signal changes, and (5) consider the energetic strategies used to sustain expensive signaling. The electric organ discharge (EOD) of B. gauderio changes in response to social environment on two time scales. Two hormone classes, melanocortins and androgens, underlie the short-term and long-term modulation of signal amplitude and duration observed during social interaction. Population density drives signal amplitude enhancement, unexpectedly improving the reliability with which the signal predicts the signaler's size. The signal's second phase elongation predicts androgen levels and male reproductive condition. Males sustain signal enhancement with dietary intake, but when food is limited, they 'go for broke' and put extra energy into electric signals. Cortisol diminishes EOD parameters, but energy-limited males offset cortisol effects by boosting androgen levels. While physiological constraints are sufficient to maintain signal amplitude reliability, phenotypic integration and signaling costs maintain reliability of signal duration, consistent with theory of honest signaling.

SUBMITTER: Gavassa S

PROVIDER: S-EPMC3680505 | biostudies-other | 2013 Jul

REPOSITORIES: biostudies-other

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Behavioral ecology, endocrinology and signal reliability of electric communication.

Gavassa Sat S Goldina Anna A Silva Ana C AC Stoddard Philip K PK

The Journal of experimental biology 20130701 Pt 13

The balance between the costs and benefits of conspicuous animal communication signals ensures that signal expression relates to the quality of the bearer. Signal plasticity enables males to enhance conspicuous signals to impress mates and competitors and to reduce signal expression to lower energetic and predation-related signaling costs when competition is low. While signal plasticity may benefit the signaler, it can compromise the reliability of the information conveyed by the signals. In thi ...[more]

PMID: 23761465

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Project description:Electric fishes have independently evolved six times. Most of these fish are weakly electric and they use their discharge mainly for orientation and communication. In the African weakly electric fish genus Campylomormyrus, electric organ discharge (EOD) signals are strikingly different in shape and duration among closely related species, they contribute to pre-zygotic isolation and may have triggered an adaptive radiation. We performed mRNA sequencing on electric organs (EOs) and skeletal muscle (SMs; from which the EOs derive) from three species with short (0.4 ms), medium (5 ms), and long (40 ms) EODs and two different cross-species hybrids. Using pairwise comparison of differential gene expression between EOs and SMs, we identified 1,444 up regulated genes in EO shared by all five species/hybrids cohorts, rendering them candidate genes for EO-specific properties in Campylomormyrus. To understand how gene expression contributes to the variation in EOD duration, we made cross species comparisons among species and tissue. We identified three types of EOD-duration-related expression patterns and several candidate genes, including KCNJ2, KLF5 and SLC24a2, their upregulation may contribute to increased EOD duration, along with a down-regulated gene KCNK6. Hybrids between a short (C. compressirostris) and a long (C. rhynchophorus) discharging species exhibit EODs of intermediate duration and showed imbalanced expression of KCNJ2 alleles. The preferential expression of the C. rhynchophorus allele is in line with a higher expression level in that parental species and points towards a cis-regulatory difference at this locus, relative to EOD duration. A further candidate gene, KLF5, is a transcription factor potentially balancing potassium channel gene expression, a crucial process for the formation of an EOD. Unraveling the genetic basis of the species-specific modulation of the EOD in Campylomormyrus is crucial for understanding the adaptive radiation of this emerging model taxon of ecological (perhaps even sympatric) speciation.

Project description:A species-level phylogenetic reconstruction of the Neotropical bluntnose knifefish genus Brachyhypopomus (Gymnotiformes, Hypopomidae) is presented, based on 60 morphological characters, approximately 1100 base pairs of the mitochondrial cytb gene, and approximately 1000 base pairs of the nuclear rag2 gene. The phylogeny includes 28 species of Brachyhypopomus and nine outgroup species from nine other gymnotiform genera, including seven in the superfamily Rhamphichthyoidea (Hypopomidae and Rhamphichthyidae). Parsimony and Bayesian total evidence phylogenetic analyses confirm the monophyly of the genus, and identify nine robust species groups. Homoplastic osteological characters associated with diminutive body size and occurrence in small stream habitats, including loss of squamation and simplifications of the skeleton, appear to mislead a phylogenetic analysis based on morphological characters alone-resulting in the incorrect placing of Microsternarchus + Racenisia in a position deeply nested within Brachyhypopomus. Consideration of geographical distribution in light of the total evidence phylogeny indicates an origin for Brachyhypopomus in Greater Amazonia (the superbasin comprising the Amazon, Orinoco and major Guiana drainages), with subsequent dispersal and vicariance in peripheral basins, including the La Plata, the São Francisco, and trans-Andean basins of northwest South America and Central America. The ancestral habitat of Brachyhypopomus likely resembled the normoxic, low-conductivity terra firme stream system occupied by many extant species, and the genus has subsequently occupied a wide range of terra firme and floodplain habitats including low- and high-conductivity systems, and normoxic and hypoxic systems. Adaptations for impedance matching to high conductivity, and/or for air breathing in hypoxic systems have attended these habitat transitions. Several species of Brachyhypopomus are eurytopic with respect to habitat occupancy and these generally exhibit wider geographical ranges than stenotopic species.

Project description:Reliability of data has become a major concern in the course of the reproducibility crisis. Especially when studying animal behavior, confounding factors such as novelty of the test apparatus can lead to a wide variability of data which may mask treatment effects and consequently lead to misinterpretation. Habituation to the test situation is a common practice to circumvent novelty induced increases in variance and to improve the reliability of the respective measurements. However, there is a lack of published empirical knowledge regarding reasonable habituation procedures and a method validation seems to be overdue. This study aimed at setting up a simple strategy to increase reliability of behavioral data measured in a familiar test apparatus. Therefore, exemplary data from mice tested in an Open Field (OF) arena were used to elucidate the potential of habituation and how reliability of measures can be confirmed by means of a repeatability analysis using the software R. On seven consecutive days, male C57BL/6J, BALB/cJ and 129S1/SvImJ mice were tested in an OF arena once daily and individual mouse behavior was recorded. A repeatability analysis was conducted with regard to repeated trials of habituation. Our data analysis revealed that monitoring animal behavior during habituation is important to determine when individual differences of the measurements are stable. Repeatability values from distance travelled and average activity increased over the habituation period, revealing that around 60% of the variance of the data can be explained by individual differences between mice. The first day of habituation was significantly different from the following 6 days. A three-day habituation period appeared to be sufficient in this study. Overall, these results emphasize the importance of habituation and in depth analysis of habituation data to define the correct starting point of the experiment for improving the reliability and reproducibility of experimental data.

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Behavioral ecology, endocrinology and signal reliability of electric communication.

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Behavioral ecology, endocrinology and signal reliability of electric communication.

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