9 research outputs found
The âpush-upâ as a calling posture in Nectophrynoides tornieri (Anura: Bufonidae) in the Amani Nature Reserve, Tanzania
Bei mÀnnlichen Individuen der in den Usambara - Bergen endemischen Kröte
Nectophrynoides tornieri wurde eine eigentĂŒmliche Körperhaltung beim Rufen beobachtet:
Die Tiere erhoben sich vom Untergrund (in allen beobachteten FĂ€llen eine Pflanze) indem sie
zuerst die Vorderbeine ausstreckten wodurch sie eine sitzende Haltung (engl.: sit-up)
einnahmen. Nach einiger Zeit wurden ĂŒberlicherweise auch die Hinterbeine völlig
ausgestreckt, was zu der hier beschriebenen âLiegestĂŒtz-Haltungâ (engl.: push-up) fĂŒhrte.
Mögliche Funktionen dieser bislang unbeschriebenen Körperhaltung wurden mit Hilfe von
Verhaltensexperimenten im Freiland untersucht. Hierbei wurden den untersuchten MĂ€nnchen
auf einem Podest entweder ein arteigenes MÀnnchen, ein Weibchen oder ein TonbandgerÀt
mit dem Anzeigeruf prĂ€sentiert und die Reaktion auf den jeweiligen Stimulus fĂŒr 10 Minuten
beobachtet und notiert. Eine Kontrollgruppe wurde unter den selben Bedingungen mit einem
leeren Podest konfrontiert. Bei dem GroĂteil der getesteten Individuen fĂŒhrte das
PrÀsentieren eines arteigenen MÀnnchens nur zum Einnehmen der sitzenden Haltung. Auf das
Vorspielen eines arteigenen Anzeigerufes reagierten hingegen mehrere MĂ€nnchen mit der
âLiegestĂŒtz-Haltungâ, die in den meisten FĂ€llen von Anzeigerufen begleitet wurde. Die
Anwesenheit eines Weibchens nahe der Rufwarte eines MĂ€nnchens schien keine Auswirkung
auf dessen Körperhaltung zu haben. Die Ergebnisse dieser Studie legen nahe, dass die
âLiegestĂŒtz-Haltungâ als Reaktion auf rufende MĂ€nnchen im nĂ€heren Umfeld eingenommen
wird. Obwohl sie die ĂŒbliche Körperhaltung beim Rufen zu sein scheint, wĂ€re eine Funktion
als visuelles Signal an andere MÀnnchen denkbar. ZusÀtzlich wird der Anzeigeruf und seine
Parameter zum ersten Mal beschrieben. Rufende MÀnnchen wurden an höheren Rufwarten gefunden als bisher angenommen. Die untersuchten Rufwarten wiesen keine signifikant
Ă€hnlichen Mikrohabitateigenschaften auf.Males of Tornierâs forest toad, Nectophrynoides tornieri, were observed to perform a peculiar
display posture, the âpush-upâ: the males raised themselves from a substrate (always a plant
structure) by first stretching their forelegs into a âsit-upâ and then their hind legs to assume
the position. We examined possible functions for the push-up position in manipulative
behavioral experiments. In a majority of the tested males, the introduction of a conspecific
male only evoked the less conspicuous sit-up display, whereas a playback of male
vocalization more often triggered the full push-up position, usually followed by a vocal
response. We found no association between the sit-up and the push-up display and the
presence of a female N. tornieri near a maleâs calling perch. Our findings support the
hypothesis that the push-up posture is a display in response to other calling males; whilst
being the usual calling posture, it might also be important in visual communication. We
describe in detail the characteristics of the call for the first time; vocalizing males were found
at more elevated positions than previously reported and there were no common distinctive
microhabitat features between calling sites
Multimodal signaling in the Small Torrent Frog (Micrixalus saxicola) in a complex acoustic environment.
Many animals use multimodal (both visual and acoustic) components in courtship signals. The acoustic communication of anuran amphibians can be masked by the presence of environmental background noise, and multimodal displays may enhance receiver detection in complex acoustic environments. In the present study, we measured sound pressure levels of concurrently calling males of the Small Torrent Frog (Micrixalus saxicola) and used acoustic playbacks and an inflatable balloon mimicking a vocal sac to investigate male responses to controlled unimodal (acoustic) and multimodal (acoustic and visual) dynamic stimuli in the frogs' natural habitat. Our results suggest that abiotic noise of the stream does not constrain signal detection, but males are faced with acoustic interference and masking from conspecific chorus noise. Multimodal stimuli elicited greater response from males and triggered significantly more visual signal responses than unimodal stimuli. We suggest that the vocal sac acts as a visual cue and improves detection and discrimination of acoustic signals by making them more salient to receivers amidst complex biotic background noise
The role of the vocal sac in multimodal signalling
Die Schallblase, die bei MÀnnchen fast aller Anurenarten vorhanden ist, wurde meist im Zu-sammenhang mit der Produktion von Anzeigerufen untersucht. Die Funktion der Schallblase jenseits der akustischen Kommunikation wurde lange Zeit kaum beachtet und Attribute, wie etwa Schallblasenbewegung wurden traditionell eher als EpiphÀnomen der Ruferzeugung ge-sehen. Die DiversitÀt von Schallblasenfarbe und -form bei verschiedenen Anurenarten ist be-eindruckend und seit wenigen Jahren wird ihren optischen Eigenschaften und ihrer möglichen Rolle in der visuellen Signalgebung mehr Aufmerksamkeit zuteil.
MĂ€nnliche Riedfrösche (Anura: Hyperoliidae) vieler Arten besitzen einen auffĂ€llig gefĂ€rbten Fleck auf der Schallblase, der besonders hervorsticht wenn die Schallblase mit Luft gefĂŒllt ist. Die Funktion dieses Kehlflecks war gĂ€nzlich unbekannt und ist das zentrale Thema meiner ex-plorativen Dissertation.
Ziel meiner Arbeit ist es, die einzigartige Riedfroschschallblase und ihre mögliche Rolle bei mul-timodaler Signalgebung, sowie ganz allgemein die faszinierende DiversitĂ€t und KomplexitĂ€t mulimodaler Signale bei Anuren zu beleuchten. Um die Rolle der Schallblase und des Kehl-flecks in inter- und intra-spezifischer Kommunikation besser zu verstehen, wurden histologische und biochemische Analysen im Labor durchgefĂŒhrt sowie Messungen von Signalparametern und EmpfĂ€ngerreaktionen auf isolierte und kombinierte Signalkomponenten in Cue-Isolationsexperimenten im Freiland integriert.
Ich konnte zeigen, dass der Kehlfleck ein DrĂŒsenkomplex ist, der artspezifische chemische Cocktails erzeugt, welche höchstwahrscheinlich wĂ€hrend des Rufens ausgestoĂen werden und somit einen bisher unbeschriebenen Signalmodus bei Anuren darstellen. Weiters stellte sich bei Feldversuchen, in denen die Reaktion von EmpfĂ€ngern auf uni- und multimodale Signale getes-tet wurde heraus, dass der farbige Kehlfleck keine Rolle in der Kommunikation zwischen MĂ€nn-chen spielt, aber ein bisher unbeschriebenes Verhalten gezeigt wird, bei dem mit dem FuĂ auf den Untergrund geklopft wird.
In zwei Kapiteln meiner Arbeit, fasse ich den aktuellen Wissensstand zu uni- und multimodalen Signalstrategien bei Riedfröschen, sowie die vielfÀltige Rolle der Schallblase in der Kommunika-tion zusammen.
AbschlieĂend diskutiere ich den Mechanismus und die Funktion der Schallblase in der akusti-schen, visuellen und chemischen Kommunikation von Riedfröschen, um zum VerstĂ€ndnis der Evolution der multimodalen Kommunikation im Tierreich beitragen zu können.The vocal sac present in males of most anuran species is generally associated with its role in advertisement call production. However, its function aside from acoustic commu-nication was neglected for some time and cues such as vocal sac movement, were tra-ditionally seen as an epiphenomon of sound production. The diversity in vocal sac col-ouration and shape found in different species is striking and recently its visual properties were awarded an important role in signalling.
Males of many reed frog species (Anura: Hyperoliidae), have a prominent colourful patch on their vocal sac, which is very conspicuous once the vocal sac is inflated. The function of the gular patch makes up the central objective of this exploratory thesis.
I aim to highlight the unique hyperolid vocal sac and its potential function in multimodal signalling in particular, and the fascinating diversity and complexity of anuran multimod-al signalling in general. To investigate the role of the vocal sac and the hyperolid gular patch in inter- and intra-specific communication, I integrated a literature research, histo-logical and biochemical analyses in the laboratory as well as measurements of signal parameters and associated receiver response to signal components in cue-isolation experiments in the field.
I demonstrate that the gular patch is a gland complex producing species-specific chemi-cal cocktails which are most likely expelled during calling - a so far undescribed mode of signalling in frogs. Furthermore, field experiments testing receiver-response to uni- and multimodal signal stimuli showed that the colourful gular patch does not act as a visual signal in male-male communication, but revealed a previously undescribed foot-tapping behaviour.
In two chapters of my thesis I sum up the current knowledge on uni- and multimodal signalling strategies in anurans and review the versatile role of the vocal sac in the anu-ran communication system.
Finally I discuss the mechanism and function of the vocal sac in acoustic, visual and chemical signalling of reed frogs to contribute to our understanding of the evolution of multimodal communication in the animal kingdom
The anuran vocal sac: a tool for multimodal signalling
Although in anurans the predominant mode of intra-and intersexual communication is vocalization, modalities used in addition to or instead of acoustic signals range from seismic and visual to chemical. In some cases, signals of more than one modality are produced through or by the anuran vocal sac. However, its role beyond acoustics has been neglected for some time and nonacoustic cues such as vocal sac movement have traditionally been seen as an epiphenomenon of sound production. The diversity in vocal sac coloration and shape found in different species is striking and recently its visual properties have been given a more important role in signalling. Chemosignals seem to be the dominant communication mode in newts, salamanders and caecilians and certainly play a role in the aquatic life phase of anurans, but airborne chemical signalling has received less attention. There is, however, increasing evidence that at least some terrestrial anuran species integrate acoustic, visual and chemical cues in species recognition and mate choice and a few secondarily mute anuran species seem to fully rely on volatile chemical cues produced in glands on the vocal sac. Within vertebrates, frogs in particular are suitable organisms for investigating multimodal communication by means of experiments, since they are tolerant of disturbance by observers and can be easily manipulated under natural conditions. Thus, the anuran vocal sac might be of great interest not only to herpetologists, but also to behavioural biologists studying communication systems
Take time to smell the frogs: vocal sac glands of reed frogs (Anura: Hyperoliidae) contain species-specific chemical cocktails
Males of all reed frog species (Anura: Hyperoliidae) have a prominent, often colourful, gular patch on their vocal sac, which is particularly conspicuous once the vocal sac is inflated. Although the presence, shape, and form of the gular patch are well-known diagnostic characters for these frogs, its function remains unknown. By integrating biochemical and histological methods, we found strong evidence that the gular patch is a gland producing volatile compounds, which might be emitted while calling. Volatile compounds were confirmed by gas chromatography-mass spectrometry in the gular glands in 11 species of the hyperoliid genera Afrixalus, Heterixalus, Hyperolius, and Phlyctimantis. Comparing the gular gland contents of 17 specimens of four sympatric Hyperolius species yielded a large variety of 65 compounds in species-specific combinations. We suggest that reed frogs might use a complex combination of at least acoustic and chemical signals in species recognition and mate choice.(c) 2013 The Authors. Biological Journal of the Linnean Society published by John Wiley & Sons Ltd on behalf of The Linnean Society of London
Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris
The contents of the gular glands of the male African reed frog Hyperolius cinnamomeoventris consist of a mixture of aliphatic macrolides and sesquiterpenes. While the known macrolide gephyromantolide A was readily identified, the structure of another major component was suggested to be a tetradecen-13-olide. The synthesis of the two candidate compounds (Z)-5- and (Z)-9-tetradecen-13-olide revealed the former to be the naturally occurring compound. The synthesis used ring-closing metathesis as key step. While the HoveydaâGrubbs catalyst furnished a broad range of isomeric products, the (Z)-selective Grubbs catalyst lead to pure (Z)-products. Analysis by chiral GC revealed the natural frog compound to be (5Z,13S)-5-tetradecen-13-olide (1). This compound is also present in the secretion of other hyperoliid frogs as well as in femoral glands of male mantellid frogs such as Spinomantis aglavei. The mass spectra of the synthesized macrolides as well as their rearranged isomers obtained during ring-closing metathesis showed that it is possible to assign the location of the double bond in an unsaturated macrolide on the basis of its EI mass spectrum. The occurrence of characteristic ions can be explained by the fragmentation pathway proposed in the article. In contrast, the localization of a double bond in many aliphatic open-chain compounds like alkenes, alcohols or acetates, important structural classes of pheromones, is usually not possible from an EI mass spectrum. In the article, we present the synthesis and for the first time elucidate the structure of macrolides from the frog family Hyperoliidae