top of page

Published Work

Zootaxa 5249 (3) © 2023 Magnolia Press |

Description of three new species of predatory Genus Hexacentrus (Orthoptera: Tettigoniidae) from India, with bioacoustic and morphological characterizations

  • Department of Biology, Ashoka University, Sonipat, India

  • Department of Zoology, Panjab University, Chandigarh, India

  • School of Biological Science, NISER, Orissa, India

  • Department of Psychology, Ashoka University, Sonipat, India

Hexacentrus is a genus of predatory katydids. In India, the genus Hexacentrus is represented by 7 species of which 6 are
morphologically characterized while one is only acoustically characterized. In this study, we describe three new species
under the genus from India based on detailed morphological, stridulatory, and acoustic features.

Front. Ecol. Evol., 30 October 2018 |

Response Mode Choice in a Multimodally Duetting Paleotropical Pseudophylline Bushcricket

  • Centre for Ecological Sciences, Indian Institute of Science, Bangalore, India

  • Department of Biology and Psychology, Ashoka University, Sonipat, India

Females of the pseudophylline bushcricket species Onomarchus uninotatus respond to a conspecific acoustic call with bouts of tremulation, followed by phonotaxis in some cases. This tremulation sends out a vibratory signal that propagates along the branch of the jackfruit trees where these animals are almost always found, and the male is able to localize the signal and perform vibrotaxis toward the female. Males are unable to localize the signal if it emanates from a branch unconnected to their perch, and therefore, female tremulation might not be a productive response when the nearest male is on an adjacent, disconnected tree. We hypothesized that female behavioral response choice between tremulation and phonotaxis might vary with distance from the caller. A semi-naturalistic experiment indicates that if the male and female are 4 m apart on a connected perch, females tremulate, and never perform phonotaxis while males perform vibrotaxis. However, at a distance of 9 m, 4 out of 10 females begin phonotaxis after a period of tremulation. We then hypothesized that features of the male call that indicate caller distance, such as call sound pressure level (SPL), might be responsible for this distance-dependent variation in the choice between phonotaxis and tremulation However, we found that at all SPLs, the female tremulates in response to male calls before attempting phonotaxis and that the probability of phonotaxis and tremulation both increased with calling song SPL. We conclude that our first hypothesis is upheld and that females do behave differently with respect to distance from the male, but that the cue affecting the distance-dependent increase in the probability of initiation of phonotaxis in female response choice is not the SPL of the male's advertisement call.

© 2015. Published by The Company of Biologists Ltd | Journal of Experimental Biology (2015) 00, 1-9 doi:10.1242/jeb.122911

A novel acoustic-vibratory multimodal duet

The communication strategy of most crickets and bushcrickets typically consists of males broadcasting loud acoustic calling songs, while females perform phonotaxis, moving towards the source of the call. Males of the pseudophylline bushcricket species Onomarchus uninotatus produce an unusually low-pitched call, and we found that the immediate and most robust response of females to the male acoustic call was a bodily vibration, or tremulation, following each syllable of the call. We hypothesized that these bodily oscillations might send out a vibrational signal along the substrate on which the female stands, which males could use to localize her position. We quantified these vibrational signals using a laser vibrometer and found a clear phase relationship of alternation between the chirps of the male acoustic call and the female vibrational response. This system therefore constitutes a novel multimodal duet with a reliable temporal structure. We also found that males could localize the source of vibration but only if both the acoustic and vibratory components of the duet were played back. This unique multimodal duetting system may have evolved in response to higher levels of bat predation on searching bushcricket females than calling males, shifting part of the risk associated with partner localization onto the male. This is the first example of bushcricket female tremulation in response to a long-range male acoustic signal and of a multimodal duet among animals.

Read Full Text

The Journal of Experimental Biology 216, 777-787 © 2013. Published by The Company of Biologists Ltd doi:10.1242/jeb.078352

Low-pass filters and differential tympanal tuning in a paleotropical bushcricket with an unusually low frequency call

Low-frequency sounds are advantageous for long-range acoustic signal transmission, but for small animals they constitute a challenge for signal detection and localization. The efficient detection of sound in insects is enhanced by mechanical resonance either in the tracheal or tympanal system before subsequent neuronal amplification. Making small structures resonant at low sound frequencies poses challenges for insects and has not been adequately studied. Similarly, detecting the direction of longwavelength sound using interaural signal amplitude and/or phase differences is difficult for small animals. Pseudophylline bushcrickets predominantly call at high, often ultrasonic frequencies, but a few paleotropical species use lower frequencies. We investigated the mechanical frequency tuning of the tympana of one such species, Onomarchus uninotatus, a large bushcricket that produces a narrow bandwidth call at an unusually low carrier frequency of 3.2kHz. Onomarchus uninotatus, like most bushcrickets, has two large tympanal membranes on each fore-tibia. We found that both these membranes vibrate like hinged flaps anchored at the dorsal wall and do not show higher modes of vibration in the frequency range investigated (1.5–20kHz). The anterior tympanal membrane acts as a low-pass filter, attenuating sounds at frequencies above 3.5kHz, in contrast to the highpass filter characteristic of other bushcricket tympana. Responses to higher frequencies are partitioned to the posterior tympanal membrane, which shows maximal sensitivity at several broad frequency ranges, peaking at 3.1, 7.4 and 14.4kHz. This partitioning between the two tympanal membranes constitutes an unusual feature of peripheral auditory processing in insects. The complex tracheal shape of O. uninotatus also deviates from the known tube or horn shapes associated with simple band-pass or high-pass amplification of tracheal input to the tympana. Interestingly, while the anterior tympanal membrane shows directional sensitivity at conspecific call frequencies, the posterior tympanal membrane is not directional at conspecific frequencies and instead shows directionality at higher frequencies.

Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138

ON Ganglion Cells Are Intrinsically Photosensitive in the Tiger Salamander Retina

Intrinsically photosensitive retinal ganglion cells (ipRGCs) have been well characterized in mammalian systems, both morphologically and electrophysiologically. They show slow, sustained responses to bright light in the absence of photoreceptor-based input, mediated by the photopigment melanopsin. Only one mammalian melanopsin gene is expressed in a small fraction of the retinal ganglion cell population, but there are two genes for melanopsin among nonmammalian vertebrates that are widely expressed in a variety of retinal and extraretinal cell types, along with other photosensitive pigments. The current study provides an electrophysiological study of ipRGCs in the larval tiger salamander (Ambystoma tigrinum), a nonmammalian vertebrate with a well-characterized retina. The results show that the ipRGC population is equivalent to the ON ganglion cell population in the tiger salamander retina. This sheds light on the evolutionary trajectory and functional significance of intrinsic photosensitivity through the vertebrate lineage and also affects our understanding of ON cell activity and development. We have characterized the nature of the intrinsic responses of the ON cell population, compared intrinsic and synaptically based receptive fields, and quantified the spectrum of the intrinsic activity. A wider action spectrum of intrinsic photosensitivity was obtained than would be expected for a single opsin photopigment, suggesting the expression of multiple photopigments in the salamander ipRGC. J. Comp. Neurol. 520:200–210, 2012.

Zootaxa 5249 (3) © 2023 Magnolia Press |

Self-efficacy assessment hinders improvement on a deliberate cricket bowling practice task

  • Department of Psychology, Ashoka University, Sonepat, Haryana, India

  • Wheelock College of Education, Boston University, Boston, MA, United States

Previous research indicates that external focused attention is linked to superior performance on motor tasks. This study examined how attention directed toward one’s self-efficacy affected performance in a cricket bowling task.

Methods: In the pre-test phase, participants attempted to bowl in a designated “good length” zone across 12 trials. Following this, participants were randomly assigned to either an experimental group, where they rated their own general and task-specific self-efficacy, or a control group, where they rated someone else’s ability. They each then bowled 12 more trials. Their performance was measured based on the number of trials that were bowled within the standard “good length” zone.

Decoy effect in shoaling decision making in zebrafish (Danio rerio)

  • Department of Psychology, Ashoka University, Sonepat, Haryana, India

Several organisms, from slime molds to humans, are known to violate normative principles of economic rationality in decision making. In animals, the neural circuitry underlying behaviors that violate or conform to normative rationality is relatively poorly understood. We investigated whether zebrafish, a model organism with a strong suite of functional neuroimaging and genetic manipulation tools, showed a decoy effect with respect to the principle of the Independence of Irrelevant Alternatives (IIA). We examined IIA in social decision-making by measuring revealed preferences from spatial trajectories of freely swimming individual zebrafish in an arena where they could view and perform shoaling behavior near conspecific zebrafish in adjacent display tanks. IIA was tested in terms of the invariance of shoaling choices between binary and ternary sets of various display fish group sizes. We provide the first report of evidence for the decoy effect in male zebrafish, but not in females. This opens up a range of possibilities to study the neural basis of context-dependent decision making.

Symbolic quantitative cognition in wild zebrafish (Danio rerio)

  • Department of Psychology, Ashoka University, Sonepat, Haryana, India

Zebrafish (Danio rerio) constitute an excellent model system to investigate the neural and genetic basis of quantitative cognition because of the single neuron resolution of calcium imaging of awake, behaving fish. While nonsymbolic numerical cognition has been investigated across many taxa, symbolic numerical cognition has not been investigated among fish. We developed a novel quantitative symbolic test for zebrafish using an operant conditioning paradigm in which the number of horizontal lines zebrafish approached in a 2-alternative forced choice task predicted the number of food reward pellets they would receive. Zebrafish did not at the population level learn a preference for the 2-line stimulus predictive of receiving 2 food pellets. However, they performed significantly above chance in a nonsymbolic discrimination task with the same apparatus, in which the 2-line stimulus was associated with the same reward but the choice of the 1-line stimulus was not rewarded. We also explored the explanatory value of alternative spatial learning hypotheses such as a Win-Stay, Lose-Shift (WSLS) strategy at the individual level for fish in navigating these spatially randomised tasks. The implications of this for symbolic versus nonsymbolic quantitative cognition in this model system are discussed relative to reward type and stimulus modality.

Zootaxa Mega-journal for zoological taxonomists in the world | 10.11646/ZOOTAXA.5249.3.2

Description of three new species of predatory Genus Hexacentrus (Orthoptera: Tettigoniidae) from India, with bioacoustic and morphological characterizations

  • Department of Biology, Ashoka University, Sonipat, India

  • India Department of Zoology, Panjab University, Chandigarh, India

  • India School of Biological Science, NISER, Orissa, India

  • India Department of Psychology, Ashoka University, Sonipat, India

Hexacentrus is a genus of predatory katydids. In India, the genus Hexacentrus is represented by 7 species of which 6 are morphologically characterized while one is only acoustically characterized. In this study, we describe three new species under the genus from India based on detailed morphological, stridulatory, and acoustic features.

bottom of page