Vocal coselection in rat pup ultrasonic vocalizations

Abstract

Selective breeding and natural selection that select for one trait often bring along other correlated traits via coselection. Selective breeding for an infantile trait, high or low call rates of isolation‐induced ultrasonic vocalization of rat pups, also alters functions of some brain systems and emotional behaviors throughout life. We examined the effect of breeding for call rate on acoustic parameters that are of communicative significance. Selecting for higher call rate produced calls of significantly increased amplitude and bandwidth relative to a randomly bred line. Selecting for lower rate produced calls of decreased duration. These nonmorphological, functional trait changes demonstrate enhanced communicatory potential and energy expenditure for the High line and the opposite for the Low line. This demonstration of coselection in a communicatory system suggests an underlying heritable suite of linked acoustic vocalization characteristics that in noisy environments could enhance dam–pup communication and lead to selection of emotionality traits with beneficial responses to stress.

Selection on ultrasonic call rate in neonatal rats affects low frequency, but not ultrasonic, vocalizations in adults

“…Therefore, we hypothesized that selection pressure for increased pup USV production would also select for ability to sustain a higher level of communicative effort in adults. Second, in an earlier study, pup line USVs were reported to differ in call duration and range (Spence et al., 2016); our second hypothesis predicts that this will remain true for the adult rat line USVs. Finally, selection for USV rate in pups potentially influences the development and structure of the larynx, which in turn could impact the production of other calls.…”

“…In earlier work, variations in acoustical features other than call rate were also found to be by‐products of the selective breeding on these two lines. These unselected, pleiotropic by‐products include longer call duration, louder relative amplitude and broader frequency bandwidth in the high‐production line (Spence, Aslam, Hofer, Brunelli, & Shair, 2016). Studies of the behaviour of these high and low lines at later ages have documented the concurrent divergence of the lines into two “affective temperaments”.…”

Born to Cry: A Genetic Dissection of Infant Vocalization

“…A dystonic rat model shows a close association between an overall slower breathing rate and different vocal characteristics compared to wild-type ( Riede et al, 2015 ). Interestingly, rat pups that were selectively bred for high call rates of isolation-induced vocalization, produced calls of significantly increased amplitude but those pup with lower vocal rates also produced calls shorter in duration ( Spence et al, 2016 ), suggesting that these vocal parameters are highly interrelated. A detailed study of the relationship between lung pressure, glottal configuration and rodent USV is necessary, and future studies should include respiratory measurements in the B6 and D2 strain and their hybrids in order to understand how differences in breathing control may translate into vocal differences.…”

“…The brain is not only essential for controlling the breathing characterizes described above, but also for the ability to vocalize in response to appropriate stimuli. Selective breeding for certain traits, for example high call rates, also alters functions of brain systems and emotional behaviors throughout life ( Spence et al, 2016 ). Candidate brain areas include the cerebellum, which plays an important role in vocalization and articulation.…”

“…A low heritability usually indicates intense neutralizing selection, whereas high heritabilities are often associated with phenotypes that either do not greatly affect fitness (relaxed selection) or that are controlled by balancing selection ( Walsh and Lynch, 2018 ) that increases variability, perhaps in order to enhance kin and litter recognition ( Forstmeier et al, 2009 ; Blumstein et al, 2013 ). Hahn et al (1997) hypothesized that rates of calling has undergone more intense selection than other characters ( Hahn et al, 1997 ), however Spence et al (2016) have shown that acoustic characteristics usually do not change in isolation but are highly interrelated ( Spence et al, 2016 ). Here, we have expanded the analysis of USVs in order to comprehensively evaluate heritability of spectral, temporal, and sound amplitude characteristics.…”