I.L.Y. Spierts

Bird song: Superfast muscles control dove's trill

Bird songs frequently contain trilling sounds that demand extremely fast vocalization control. Here we show that doves control their syrinx, a vocal organ that is unique to birds, by using superfast muscles. These muscles, which are similar to those that operate highly specialist acoustic organs such as the rattle of the rattlesnake, are among the fastest vertebrate muscles known and could be much more widespread than previously thought if they are the principal muscle type used to control bird songs.

Superfast muscles control dove's trill

Bird songs frequently contain trilling sounds that demand extremely fast vocalization control. Here we show that doves control their syrinx, a vocal organ that is unique to birds, by using superfast muscles. These muscles, which are similar to those that operate highly specialist acoustic organs such as the rattle of the rattlesnake, are among the fastest vertebrate muscles known and could be much more widespread than previously thought if they are the principal muscle type used to control bird songs.

Syringeal muscles fit the trill in ring doves (Streptopelia risoria L.)

SUMMARY In contrast to human phonation, the virtuoso vocalizations of most birds are modulated at the level of the sound generator, the syrinx. We address the hypothesis that syringeal muscles are physiologically capable of controlling the sound-generating syringeal membranes in the ring dove (Streptopelia risoria) syrinx. We establish the role of the tracheolateralis muscle and propose a new function for the sternotrachealis muscle. The tracheolateralis and sternotrachealis muscles have an antagonistic mechanical effect on the syringeal aperture. Here, we show that both syringeal muscles can dynamically control the full syringeal aperture. The tracheolateralis muscle is thought to directly alter position and tension of the vibrating syringeal membranes that determine the gating and the frequency of sound elements. Our measurements of the muscles contractile properties, combined with existing electromyographic and endoscopic evidence, establish its modulating role during the doves trill. The muscle delivers the highest power output at cycle frequencies that closely match the repetition rates of the fastest sound elements in the coo. We show that the two syringeal muscles share nearly identical contraction characteristics, and that sternotrachealis activity does not clearly modulate during the rapid trill. We propose that the sternotrachealis muscle acts as a damper that stabilizes longitudinal movements of the sound-generating system induced by tracheolateralis muscle contraction. The extreme performance of both syringeal muscles implies that they play an important role in fine-tuning membrane position and tension, which determines the quality of the sound for a conspecific mate.

Titin isoforms and kinematics of fast swimming carp larvae (Cyprinus carpio L.)

Titin, a striated-muscle specific protein spanning the distance between Z- and M-lines of sarcomeres, is held responsible for developing passive tension and for maintaining the central position of thick filaments in contracting sarcomeres. Different muscles express titin isoforms of different molecular mass. To improve the insight in the relation between titin isoforms and kinematics of fast swimming at different ages the presence of carp larval muscle titin (Cyprinus carpio L.) was investigated and compared with data of adult carp. Gel-electrophoresis revealed that titin isoforms were larger in adult than in larval muscle. Apparently the molecular structure of titin changed during ontogeny. A previous study showed that the size of titin is correlated with the functioning of different muscles during swimming. Fish larvae (6.5-8 mm total length), subjected to low Reynolds-number regimes during swimming (Re < 500), require special features to overcome frictional effects. Fibres with smaller titin isoforms require more passive tension when being stretched. During fast swimming of larvae, passively stretched fibres at the convex side of the body axis absorb energy, generated by activity of fibres at the concave side, that is released in the successive opposite bending.

Muscle activation and strain patterns of the m. hyohyoideus of the carp (Cyprinus carpio L.) during opercular movements

We investigated the function of the m. hyohyoideus superior (MHS) and inferior (MHI) in the head of three carp (Cyprinus carpio L., 29.7 ± 2.1 cm FL ) during three movements (normal breathing, stressed movements and food uptake). Both muscle parts are located ventrally at the inner side of the operculum and branchiostegal rays and consist of red (mainly in MHI) and white (mainly in MHS) fibres. Contrasting views exist about the functional role of these muscles during ventilation and food uptake. Therefore, we analysed muscle activities of the MHS and MHI using electromyography (EMG) and measured the strain pattern of the MHS using sonomicrometry. Carp were also filmed from a ventral viewpoint using high-speed video at 250 frames s-1. EMG and sonomicrometry data showed an increase in muscle strain amplitudes, cycle frequency and (relative) stimulus duration while stimulus on- and off-times occurred earlier in the strain cycle from normal breathing to stressed movements to food uptake. The MHS and MHI were always simultaneously active. We concluded that: 1) the MHI is not responsible for high frequency movements (i.e. stressed movements and food uptake); 2) both muscle parts assist in the onset of opercular closing, and 3) the MHS and MHI do not act as antagonists in carp.

Superfast muscles control dove's trill: Bird song

Bird songs frequently contain trilling sounds that demand extremely fast vocalization control. Here we show that doves control their syrinx, a vocal organ that is unique to birds, by using superfast muscles. These muscles, which are similar to those that operate highly specialist acoustic organs such as the rattle of the rattlesnake, are among the fastest vertebrate muscles known and could be much more widespread than previously thought if they are the principal muscle type used to control bird songs.

Fish axial muscle : structure-function relationships on a micro-level

This paper discusses some examples of strong correlations between functions and structures in axial fish muscle on a micro-level. Muscle tissue needs a certain elasticity to cope with the diverse functional requirements necessary for swimming. During fast-starts of carp, muscles can be stretched up to 40% above their resting length. These muscles need to be designed such that they can endure these strains and simultaneously provide the required force. Posterior fibres of adult carp have a longer phase of eccentric activity (active while being stretched) than anterior ones and will therefore develop greater forces. Posterior and red fibres are subjected to larger strains during continuous swimming and have special adaptations on a microscopical level to meet these functional demands. A linear correlation was found between surface areas of myotendinous junctions (MTJs), connections between muscle fibres and collagen fibres (measure for strength) and the size and duration of load on a junction. Fibres with larger surface areas consequently can bear larger loads. Exactly those fibres subjected to larger loads during swimming, posterior and red fibres, possessed stronger MTJs. Titin and intermediate filaments are important elastic structures in muscle. Titin acts as a dual spring developing passive tension upon sarcomere stretching and shortening. Less passive tension was needed to stretch red posterior fibres, with larger titin isoforms, compared to the less elastic red anterior fibres. Intermediate filaments act as safety devices protecting muscles from permanent damage due to too high strains. Anterior fibres possessed smaller intermediate filaments, thus protecting them at shorter sarcomere lengths from being torn apart due to too large strains. This study corroborates the idea that (small) differences in muscle function during swimming, turning and escaping can be used to predict and possibly explain structural differences between muscle types and at different locations.