We have decided to organize a series of monthly online meetings to help foster exchange in our dynamic biotremology community and to fill the gap during the time when a live conference is not possible. They are primarily geared towards PhD students and early-career researchers, but ‘seniors’ are warmly welcomed as well. These meetings will take place from April 2021 onwards.
The format for these meetings is less formal and not fixed, and the committee is also accepting ideas and proposals for other kinds of online gatherings, such as round tables, plenary lectures from established researchers, etc. on any related topic. Guest organizers are welcome too; the online platform will be provided by the National Institute of Biology.
The organizing committee consists of members of the biotremology group at the National Institute of Biology: Rok Janža, dr. Anka Kuhelj, Juan Jose Lopez Diez, dr. Jernej Polajnar, dr. Nataša Stritih-Peljhan, Rok Šturm, and dr. Meta Virant-Doberlet.
We would appreciate comments, ideas, etc. by way of a message to firstname.lastname@example.org – that will help us gauge interest in the community.
BioTremoTalks are on hold because of the planned “real-life” conference this year. We are accepting proposals to take over organization and continue with regular online meetings if there is interest.
January 2022 meeting
The seventh BioTremoTalks meeting took place on 13 January 2022, with one presentation:
- Dr. Louise Roberts (Cornell University, USA): Investigating the lawn-destroyers: how do meso-mammals locate their below-ground prey?
In turfgrasses, damage from root-feeding pests (such as white grubs) is compounded by the destruction to turf caused by their vertebrate predators when foraging or “grubbing” in soil. The striped skunk (Mephitis mephitis) and North American raccoon (Procyon lotor), are the most common species visibly uprooting and overturning sod during foraging activity. Whilst the turf damage caused by vertebrate foraging is a useful marker for soil insect infestations, the vertebrate damage itself leads to costly sod repair making the management of the predators as important as the below-ground pests. Current management strategies involve wildlife trapping and removal which is costly and often requires professional expertise, and only provides a temporary solution as more foragers will recolonize the newly vacated range. Meso-mammals may utilise acoustic, vibratory, olfactory, and tactile cues to locate subterranean prey, and both skunks and raccoons exhibit a high degree of accuracy to their foraging bouts. Improving understanding of these cues may allow managers to disrupt the localisation process, potentially providing a management option for reducing vertebrate damage. Here we present this project, in its infancy, which will consist of vibratory playbacks to wild skunks and raccoons in the field; and we will encourage a broader discussion about the work, and playbacks, with the group.
November 2021 meeting
The sixth BioTremoTalks meeting took place on 25 November 2021, with one presentation:
- Juan José López Díez (National Institute of Biology, Slovenia): Boléro by leafhoppers: The complex reproductive strategy of Orientus ishidae
Orientus ishidae (Matsumura) (Hemiptera, Cicadellidae) is an invasive leafhopper from eastern Asia. Since it has a capacity to transmit Flavescence Dorée phytoplasma, this insect is a potential pest in vineyards. We studied vibrational communication in O. ishidae in order to understand the reproductive behaviour of this species and obtain necessary information needed to design potential control measures. Vibrational repertoire of O. ishidae was found to be rich and complex. Mating behaviour sequence can be divided into three phases, (1) recognition duet, (2) courtship phase that includes early and late courtship and (3) wing phase. Each phase was characterized by different types of male and female vibrational signals and duet structure. Each phase consisted of several cycles in which signals and phrases were repeated in a stereotyped pattern and progressively changed throughout the phase. Males had to complete all stages in order to obtain copulation. Male competitive behaviour was expressed in emission of high-amplitude rivalry signals emitted in the female reply window within the duet with another male, as well as in satellite behaviour.
Like a finally crafted symphony, we will listen to the repertoire of this little insect and compare it with one of the most notorious classical music pieces: Boléro, by Maurice Ravel
October 2021 meeting
The fifth BioTremoTalks meeting took place on 21 October 2021, with one presentation:
- Dr. Rachele Nieri (University of Trento, Italy): Biotremology of social wasps: A neglected communication channel
The social life of social wasps is considered to be based on chemical communication and only recently has some attention been focused on visual signals but vibrational communication is still largely neglected in this group. Nonetheless, it has been confirmed that behaviors, inducing vibrations, are present in all six subfamilies of social wasps and that in some species, vibrations mediate crucial aspects of their life. For instance, specific vibrations transmitted to the nest by the females of the paper wasp, Polistes dominula, have been demonstrated to be involved in adult-larvae communication. To better understand the role of vibrations in P. dominula social life, we used an electro-magnetic shaker to investigate how the intensity, the frequency, and the rhythm of vibrations propagate into the nest structure. This study represents a conceptual and methodological framework to promote future studies on this rather neglected communication channel in social insects.
September 2021 meeting
The fourth BioTremoTalks meeting took place on 23 September 2021, with one presentation:
- Dr. Anka Kuhelj (National Institute of Biology, Slovenia): Vibrational duetting and signal production in Aphrodes makarovi leafhoppers
In the leafhopper Aphrodes makarovi, sexual communication is mediated by reciprocal exchange of vibrational signals. Duet is initiated and maintained by a male to which a sexually receptive female responds. Female reply is essential for her localization. Duetting leafhoppers adjust the length of their signals to the partner’s. The beginning of a female reply overlaps with the last section of the male advertisement call. Males are able to perceive the non-overlapped part of the reply only. Our results suggest that the length of the reply has a great impact on males’ searching behaviour, calling effort and consequently on costs of mating.
Besides, our results show that A. makarovi males use different strategies to increase their mating success when competing with other males. They are able to eavesdrop on male–female duet maintained by the calling male, and they can overlap female replies by emitting masking signals. In the presence of a rival males with greater reproductive success invest more in competitive behaviour than in advertising. Females, however, mate with the first male to locate them what may also be a strategy to mate with the male in better condition.
Respiration rate measurements together with behavioural trials enabled us to assess costs of males and females resulting from emission of vibrational signals. Respiration rate for males when emitting advertisement calls is 1.5 times higher compared to replying females. Higher signalling activity leads to a shorter lifespan in both sexes.
We also investigated the mechanism of signal production in A. makarovi leafhoppers. Pulses in female vibrational signals appear to be associated with bending of both tymbal membranes and they also match with the EMGs from Ia dvm1. In males, tymbal area is more complex and during production of advertisement calls the whole abdomen is vibrating, nevertheless EMGs from Ia dvm1 match the signals. Ultrastructural features of especially male’s Ia dvm1 imply on a fast muscle with huge energy consumption.
June 2021 meeting
The third BioTremoTalks meeting took place on 17 June 2021, with two presentations:
- Rok Šturm (National Institute of Biology, Slovenia): Ecotremology – new insights into hidden ecosystems: a pioneer study in meadow habitats
In 2016, biotremology – study of mechanical communication by surface-borne waves, was defined as an independent scientific discipline. The transmission media (air vs solids) impose different constraints on signal propagation so organisms using different media follow different evolutionary paths.
In our work, we focused on meadow habitats from Slovenia. The vibroscape structure and dynamics were analysed at different temporal scales, from diel variation to seasonal changes. Substrate vibrations were recorded from plant stems using laser vibrometers. Vibrational events were manually assigned to vibrational signal types (VST) according to their temporal and spectral characteristics. Vibrational signals are species- and sex-specific. Due to the lack of verified publicly available library of vibrational signals, only 13 out of 60 registered VSTs could be identified to species level.
The highest abundance of VSTs was observed at the beginning of July, when the vibrational community included 14 species with three VSTs dominating. The overlap of these signals in time and frequency domain was significantly smaller than it would be by chance. This reveal for the first time a partitioning of the vibroscape, which suggests existence of species interaction for communication channel. Diel variation in vibrational signalling activity was correlated with ambient temperature (Pearson r = 0.7). Wind provided nearly constant background vibrational noise but higher wind velocities (> 0.8 m/s) reduced the amount of biological component of vibroscape. Results also revealed differences in vibroscape composition between hairy sedge (Carex hirta) and hedge bedstraw (Galium mollugo) plants growing on the same meadow. The former included a higher VST richness and higher abundance turnover among individual plants, which may be attributed to plant geometry and host specific plant-animal interaction.
In summary, the vibroscape of a meadow revealed a rich and complex vibratory world which is not directly accessible to humans. Vibrational signalling is the most common form of mechanical communication, particularly common in arthropods, and as such, surface-borne mechanical waves are commonly present in environment and offer readily available and reliable source of information on ecological processes in hidden ecosystems.
- Dr. Aline Moreira Dias Martinez (Semiochemicals Laboratory – Embrapa Genetic Resources and Biotechnology, Brazil): Multimodal communication in the Neotropical brown stink bug Euschistus heros, interaction between chemical and vibratory signals
Interaction between signals from different modalities could be decisive for satisfactory information interchange in insect communication. During the reproductive behavior stink bugs communicate by chemical, physical and visual signals as male sex pheromone, chemical traces, from cuticular hydrocarbons left on substrate by insects tarsus, and substrate-bone vibrations. Although several aspects regarding communication with these signals are known, the interaction between them and how they can influence the communication, behavior and reproductive success of stink bugs is still poorly understood. To increase this knowledge, we evaluated how chemical and vibratory signals interact during reproductive behavior of Euschistus heros. We conduct experiments in artificial arenas, glass Petri dishes, and natural arenas, bean plants, to study the chemical traces effect of males and females in the vibratory communication and mating behavior. We evaluate the influence of sex pheromone in vibratory communication, in experiments using plants and a paper treated with 5µL of male pheromone extract, and control were plants with paper with 5 µL of n-hexane. To evaluate if vibrational signals can interfere on male pheromone released rate, were made experiments with SPME fiber to capture the volatiles and inject on CGMS to quantified the pheromonal compound. Our results show a clear influence of chemical signals on the vibrational communication of E. heros. The presence of chemical traces of their conspecific stimulate the insects to emit vibrational signals, in addition couples in presence of female traces increase successful mattings, that may be a consequence of higher emission of male mating song (MS3) by males when in presence of female traces. Male sex pheromone near the plants stimulates the E. heros females to emit vibrational signals and inhibits the males. In turn, the vibrational signals modulate the emission of chemical signals since it was observed that males stimulated with the vibrational signals of females emit higher quantities of sexual pheromone. It was also observed changes in temporal and spectral structure of vibratory signals when insects were exposed to conspecific chemical signals. Our results show that there is an interaction of chemical and vibrational signals with consequences both on the modulation of the emission of the vibrational signals and on their structure. This interaction increases emission of signals directly related with sexual communication that may result in greater reproductive success of individuals.
May 2021 meeting
The second BioTremoTalks meeting took place on 20 May 2021, with two presentations:
- Dr. Erin Brandt (University of Western Ontario, Canada): Males like it hot, females do not: temperature effects on courtship behaviour in Habronattus clypeatus
Environmental context is a crucial factor that influences sexual communication systems. Particularly in ectotherms, which cannot metabolicallyregulate their body temperature, temperature has an outsized effect on these intraspecific interactions. Using the desert-dwelling jumping spider Habronattus clypeatus, we assessed how temperature impacts various parts of the male signal and female mate choice for the signal. These spiders have multimodal, temporally structured courtship displays that begin with visual-only ‘sidling’ displays and proceed to multimodal visual and vibratory displays.
We first measured temperature and apparent activity of individuals across the day. We found that H. clypeatus are active across a wide range of temperatures (11–56 °C) and are most active at times of day when temperature ranges from 13 to 46 °C. Next, we performed two different mating experiments across behaviourally relevant temperatures. We first tested whether key intersexual behaviours would change with temperature in similar, predictable ways across males and females. Male visual and vibratory courtship behaviours generally became faster, higher-pitched, and lower in amplitude at higher temperatures. This relationship between temperature and signal aspects attained a roughly curvilinear shape, with an asymptote around 40 °C. Females were more likely to allow males to progress to later stages of courtship and had higher mating rates at higher temperatures. Intriguingly, mating rates in the lab were highest at temperatures potentially above those during peak spider activity in the field. In a second experiment, we specifically focused on female preferences for male signals at room temperature and high temperature. We found that the only aspect of male courtship that females expressed preference for was sidling courtship, but only at the higher temperature. Specifically, females preferred to mate with males that performed shorter sidling displays at the higher temperature. Our results highlight the importance of understanding environmental context in studies of animal communication. We also stress how a holistic, rather than reductive, approach to complex communication systems is vital to understand how selection acts upon them.
- Dr. Valentina Zaffaroni Caorsi (University of Trento/Fondazione Edmund Mach, Italy): Design of ideal vibrational signals for male attraction, through vibrotaxis experiments, to enhance pest control of stinkbugs
Satisfying the increasing world-population demand for safe and sustainably-produced food is a tough challenge that policy makers, stakeholders and scientist will face in the coming decades. One issue of particular concern is the demand for the reduction of external inputs required for pest control, which currently mainly relies on pesticides, which are threatening the environment and human health. Thus, alternative methods to control insect pests are needed to minimize these risks. Innovative methods aim at developing sustainable pest control methods by means of behavioral manipulation of insects, for instance using vibrational signals. This study aimed to explore the use of substrate-borne vibrations for pest control of the brown marmorated stink bug (BMSB), Halyomorpha halys Stål (Heteroptera: Pentatomidae). To this purpose, we first defined the spectral and temporal characteristics that best elicit male responsiveness by means of bioassays conducted with artificially created signals mimicking female vibratory emission. Then, we evaluated male responsiveness to the signals with different features and supposed degree of acceptability by means of a wooden custom-made T stand arena designed to perform single and two choice test experiments. The results from this study showed that males were attracted to female signals along a high range of amplitudes, with higher pulse repetition time and peak of frequency in correspondence to the first harmonic. This allowed us to propose an “optimal” signal to be used to attract males. When exposing males to single and double choice tests in the T arena, males showed a significant orientation towards the “optimal” female signal. Our result brings this signal to elicit searching behavior and attract males of BMSB towards a stimulation point. Furthermore, we confirm the use of vibrational signal as a strong tool for the development of traps for the species and the further management of this pest.
April 2021 meeting
The inaugural BioTremoTalks meeting took place on 22 April 2021, with two presentations:
- Dr. Julie Jung (Boston University, USA): Vibration-cued early hatching in red-eyed treefrog embryos
Arboreal embryos of red-eyed treefrogs, Agalychnis callidryas, hatch prematurely to escape from egg predators, cued by vibrations in attacks. Young embryos modulate hatching based on multiple, non-redundant frequency and temporal properties of vibration cues, reducing the chance of false alarms that unnecessarily expose hatchlings to risk in the water. We used a variety of techniques, including vibration playbacks, to test two hypotheses concerning why hatching responses increase developmentally. First, we tested the hypothesis that sensory development improves cue detection. In ch.1, we assessed the role of vestibular mechanoreception in A. callidryas embryos. We found ontogenetic congruence of vestibular system function and MCH, suggesting that the developing ear plays a role in egg-motion sensing. In ch.2, we tested if lateral line mechanoreceptors contribute to MCH by blocking neuromast function with gentamicin then exposing embryos to vibration cues across ontogeny. We found that the lateral line mediates the earliest onset of MCH, and MCH continues to increase with increasing numbers of neuromasts. Second, we tested the hypothesis that, once sensory capabilities have developed, embryos are able to consider the cues available to them and weigh their costs and benefits in order to make an informed, optimal decision to hatch. Ch.3 explored the ways in which embryo responses could be contextually modulated in complex ways. We showed that second-order temporal pattern elements such as prefixes and long gaps could be threatening in certain contexts and not in others, suggesting that embryos practice a very impressive, highly functioning decision-making process that incorporates multiple vibration properties to distinguish between threatening and non-threatening stimuli. Development had a drastic effect on this decision process because hatchlings face aquatic predators in ponds. Since older and bigger hatchlings were less likely to be killed by this new suite of predators, the costs of false alarms decreased as embryos approach spontaneous hatching and they should decide to hatch more readily compared to their younger and smaller counterparts. In ch.4, we showed that older embryos selectively accept more false alarms in response to ambiguous cues, providing evidence for ontogenetic adaptation in information use for escape-hatching decisions. Overall, this research will help us understand how animals facing different risk trade-offs use information to make crucial behavioral decisions.
- Sabina Avosani (University of Trento/Fondazione Edmund Mach, Italy): Sexual behaviour and vibrational manipulation of insect vectors: the case of the meadow spittlebug Philaenus spumarius
After the introduction of Xylella fastidiosa, Europe was thrown into an arms race aimed at developing control methods against the vector, the meadow spittlebug Philaenus spumarius. A question rose among researchers: may biotremology support the development of vibrational management techniques against the spittlebug? And here we come.
During our explorations, we described the wide vibrational repertoire of P. spumarius and provided evidence that vibrations may interfere with relevant behaviours of the insect. We propose you to join us into a small journey to discover the vibrational communication of this common plant-dwelling insect.
With presenters’ permission, the talks are being recorded and published after each session on the Biotremology YouTube channel.