Visual attention and processing in jumping spiders.

Jumping spiders have extraordinary vision. Using multiple, specialized eyes, these spiders selectively gather and integrate disparate streams of information about motion, color, and spatial detail. The saccadic movements of a forward-facing pair of eyes allow spiders to inspect their surroundings and identify objects. Here, we discuss the jumping spider visual system and how visual information is attended to and processed.

Tiny spies: mosquito antennae are sensitive sensors for eavesdropping on frog calls.

Most mosquito and midge species use hearing during acoustic mating behaviors. For frog-biting species, however, hearing plays an important role beyond mating as females rely on anuran calls to obtain blood meals. Despite the extensive work examining hearing in mosquito species that use sound in mating contexts, our understanding of how mosquitoes hear frog calls is limited. Here, we directly investigated the mechanisms underlying detection of frog calls by a mosquito species specialized on eavesdropping on anuran mating signals: Uranotaenia lowii. Behavioral, biomechanical and neurophysiological analyses revealed that the antenna of this frog-biting species can detect frog calls by relying on neural and mechanical responses comparable to those of non-frog-biting species. Our findings show that in Ur. lowii, contrary to most species, males do not use sound for mating, but females use hearing to locate their anuran host. We also show that the response of the antennae of this frog-biting species resembles that of the antenna of species that use hearing for mating. Finally, we discuss our data considering how mosquitoes may have evolved the ability to tap into the communication system of frogs.

Outsourced hearing in an orb-weaving spider that uses its web as an auditory sensor.

SignificanceThe sense of hearing in all known animals relies on possessing auditory organs that are made up of cellular tissues and constrained by body sizes. We show that hearing in the orb-weaving spider is functionally outsourced to its extended phenotype, the proteinaceous self-manufactured web, and hence processes behavioral controllability. This finding opens new perspectives on animal extended cognition and hearing-the outsourcing and supersizing of auditory function in spiders. This study calls for reinvestigation of the remarkable evolutionary ecology and sensory ecology in spiders-one of the oldest land animals. The sensory modality of outsourced hearing provides a unique model for studying extended and regenerative sensing and presents new design features for inspiring novel acoustic flow detectors.

Quantitative skills in undergraduate neuroscience education in the age of big data.

For over a half-Century, the mathematics requirement for graduation at most undergraduate colleges and universities has been one year of calculus and a semester of statistics. Many universities and colleges offer a neuroscience major that may or may not add additional mathematics, statistics, or data science requirements. Today in the age of Big Data and Systems Neuroscience, many students are ill-equipped for the future without the tools of computational competency that are necessary to tackle the large data sets generated by contemporary neuroscience research. Required courses in statistics still focus on parametric statistics based on the normal distribution and do not provide the computational tools required to analyze big data sets. Undergraduates in STEM fields including neuroscience need to enroll in the Data Science courses that are required in the social sciences (e.g., economics, political science and psychology). Contemporary systems neuroscience is routinely done by interdisciplinary research teams of statisticians, engineers, and physical scientists. Emerging "NeuroX-omics" such as connectomics have emerged along with genomics, proteomics, and transcriptomics, all of which deploy systems analysis techniques based on mathematical graph theory. Connectomics is the 21st Century's functional neuroanatomy. Whole brain connectome research appears almost monthly in the Drosphila, zebra fish, and mouse literature, and human brain connectomics is not far behind. The techniques for connectomics rely on the tools of data science. Undergraduate neuroscience students are already squeezed for credit hours given the high-prescribed science curriculum for biology majors and premedical students, in addition to required courses in social sciences and humanities. However, additional training in mathematics, statistics, computer science, and/or data science is urgently needed for undergraduate neuroscience majors just to understand the contemporary research literature. Undoubtedly, the faculty who teach neuroscience courses are acutely aware of the problem and most of them freely acknowledge the importance of quantitative analytical skills for their students. However, some faculty members may feel that their own math and statistics knowledge or other analytical skills have atrophied beyond recall or were never fulfilled in the first place. In this commentary I suggest that this problem can be ameliorated, though not solved, through organizing workshops, journal clubs, or independent studies courses in which the students and the instructors learn and teach each other in short-course format. In addition, web-available teaching materials such as targeted video clips are plentifully available on the internet. To attract and maintain student interest, qauntitative instruction and learning should occur in neuroscience context.

Attention and distraction in the modular visual system of a jumping spider.

Animals must selectively attend to relevant stimuli and avoid being distracted by unimportant stimuli. Jumping spiders (Salticidae) do this by coordinating eyes with different capabilities. Objects are examined by a pair of high-acuity principal eyes, whose narrow field of view is compensated for by retinal movements. The principal eyes overlap in field of view with motion-sensitive anterior-lateral eyes (ALEs), which direct their gaze to new stimuli. Using a salticid-specific eyetracker, we monitored the gaze direction of the principal eyes as they examined a primary stimulus. We then presented a distractor stimulus visible only to the ALEs and observed whether the principal eyes reflexively shifted their gaze to it or whether this response was flexible. Whether spiders redirected their gaze to the distractor depended on properties of both the primary and distractor stimuli. This flexibility suggests that higher-order processing occurs in the management of the attention of the principal eyes.

Ogre-Faced, Net-Casting Spiders Use Auditory Cues to Detect Airborne Prey.

Prey capture behavior among spiders varies greatly from passive entrapment in webs to running down prey items on foot. Somewhere in the middle are the ogre-faced, net-casting spiders [1] (Deinopidae: Deinopis) that actively capture prey while being suspended within a frame web [2-5]. Using a net held between their front four legs, these spiders lunge downward to ensnare prey from off the ground beneath them. This "forward strike" is sensorially mediated by a massive pair of hypersensitive, night-vision eyes [5-7]. Deinopids can also intercept flying insects with a "backward strike," a ballistically rapid, overhead back-twist, that seems not to rely on visual cues [4, 5, 8]. Past reports have hypothesized a role of acoustic detection in backward strike behavior [4, 5, 8]. Here, we report that the net-casting spider, Deinopis spinosa, can detect auditory stimuli from at least 2 m from the sound source, at or above 60 dB SPL, and that this acoustic sensitivity is sufficient to trigger backward strike behavior. We present neurophysiological recordings in response to acoustic stimulation, both from sound-sensitive areas in the brain and isolated forelegs, which demonstrate a broad range of auditory sensitivity (100-10,000 Hz). Moreover, we conducted behavioral assays of acoustic stimulation that confirm acoustic triggering of backward net-casting by frequencies in harmony with flight tones of known prey. However, acoustic stimulation using higher frequency sounds did not elicit predatory responses in D. spinosa. We hypothesize higher frequencies are emitted by avian predators and that detecting these auditory cues may aid in anti-predator behavior. VIDEO ABSTRACT.

The Long and Short of Hearing in the Mosquito Aedes aegypti.

Mating behavior in Aedes aegypti mosquitoes occurs mid-air and involves the exchange of auditory signals at close range (millimeters to centimeters) [1-6]. It is widely assumed that this intimate signaling distance reflects short-range auditory sensitivity of their antennal hearing organs to faint flight tones [7, 8]. To the contrary, we show here that male mosquitoes can hear the female's flight tone at surprisingly long distances-from several meters to up to 10 m-and that unrestrained, resting Ae. aegypti males leap off their perches and take flight when they hear female flight tones. Moreover, auditory sensitivity tests of Ae. aegypti's hearing organ, made from neurophysiological recordings of the auditory nerve in response to pure-tone stimuli played from a loudspeaker, support the behavioral experiments. This demonstration of long-range hearing in mosquitoes overturns the common assumption that the thread-like antennal hearing organs of tiny insects are strictly close-range ears. The effective range of a hearing organ depends ultimately on its sensitivity [9-13]. Here, a mosquito's antennal ear is shown to be sensitive to sound levels down to 31 dB sound pressure level (SPL), translating to air particle velocity at nanometer dimensions. We note that the peak of energy of the first formant of the vowels of the human speech spectrum range from about 200-1,000 Hz and is typically spoken at 45-70 dB SPL; together, they lie in the sweet spot of mosquito hearing. VIDEO ABSTRACT.

Reducing the Cost of Electrophysiology in the Teaching Laboratory.

Electrophysiology is a fundamental part of neuroscience and there are many published laboratory exercises suitable for undergraduates. However, the cost of equipping a lab is often a barrier to implementing these exercises. In this paper, we outline lab needs, suggest strategies for building a lab incrementally by adding equipment as budgets permit, and suggest specific areas for cost-cutting. We also point out instances in which it makes most sense to purchase or borrow research-grade equipment. A linked Google document lists specific items, prices, and purchase links.

Extending julius seizure, a bang-sensitive gene, as a model for studying epileptogenesis: Cold shock, and a new insertional mutation.

The bang-sensitive (BS) mutants of Drosophila are an important model for studying epilepsy. We recently identified a novel BS locus, julius seizure (jus), encoding a protein containing two transmembrane domains and an extracellular cysteine-rich loop. We also determined that jussda iso7.8, a previously identified BS mutation, is an allele of jus by recombination, deficiency mapping, complementation testing, and genetic rescue. RNAi knockdown revealed that jus expression is important in cholinergic neurons and that the critical stage of jus expression is the mid-pupa. Finally, we found that a functional, GFP-tagged genomic construct of jus is expressed mostly in axons of the neck connectives and of the thoracic abdominal ganglia. In this Extra View article, we show that a MiMiC GFP-tagged Jus is localized to the same nervous system regions as the GFP-tagged genomic construct, but its expression is mostly confined to cell bodies and it causes bang-sensitivity. The MiMiC GFP-tag lies in the extracellular loop while the genomic construct is tagged at the C-terminus. This suggests that the alternate position of the GFP tag may disrupt Jus protein function by altering its subcellular localization and/or stability. We also show that a small subset of jus-expressing neurons are responsible for the BS phenotype. Finally, extending the utility of the BS seizure model, we show that jus mutants exhibit cold-sensitive paralysis and are partially sensitive to strobe-induced seizures.

Airborne Acoustic Perception by a Jumping Spider.

Jumping spiders (Salticidae) are famous for their visually driven behaviors [1]. Here, however, we present behavioral and neurophysiological evidence that these animals also perceive and respond to airborne acoustic stimuli, even when the distance between the animal and the sound source is relatively large (∼3 m) and with stimulus amplitudes at the position of the spider of ∼65 dB sound pressure level (SPL). Behavioral experiments with the jumping spider Phidippus audax reveal that these animals respond to low-frequency sounds (80 Hz; 65 dB SPL) by freezing-a common anti-predatory behavior characteristic of an acoustic startle response. Neurophysiological recordings from auditory-sensitive neural units in the brains of these jumping spiders showed responses to low-frequency tones (80 Hz at ∼65 dB SPL)-recordings that also represent the first record of acoustically responsive neural units in the jumping spider brain. Responses persisted even when the distances between spider and stimulus source exceeded 3 m and under anechoic conditions. Thus, these spiders appear able to detect airborne sound at distances in the acoustic far-field region, beyond the near-field range often thought to bound acoustic perception in arthropods that lack tympanic ears (e.g., spiders) [2]. Furthermore, direct mechanical stimulation of hairs on the patella of the foreleg was sufficient to generate responses in neural units that also responded to airborne acoustic stimuli-evidence that these hairs likely play a role in the detection of acoustic cues. We suggest that these auditory responses enable the detection of predators and facilitate an acoustic startle response. VIDEO ABSTRACT.

Visual perception in the brain of a jumping spider.

Jumping spiders (Salticidae) are renowned for a behavioral repertoire that can seem more vertebrate, or even mammalian, than spider-like in character. This is made possible by a unique visual system that supports their stalking hunting style and elaborate mating rituals in which the bizarrely marked and colored appendages of males highlight their song-and-dance displays. Salticids perform these tasks with information from four pairs of functionally specialized eyes, providing a near 360° field of view and forward-looking spatial resolution surpassing that of all insects and even some mammals, processed by a brain roughly the size of a poppy seed. Salticid behavior, evolution, and ecology are well documented, but attempts to study the neurophysiological basis of their behavior had been thwarted by the pressurized nature of their internal body fluids, making typical physiological techniques infeasible and restricting all previous neural work in salticids to a few recordings from the eyes. We report the first survey of neurophysiological recordings from the brain of a jumping spider, Phidippus audax (Salticidae). The data include single-unit recordings in response to artificial and naturalistic visual stimuli. The salticid visual system is unique in that high-acuity and motion vision are processed by different pairs of eyes. We found nonlinear interactions between the principal and secondary eyes, which can be inferred from the emergence of spatiotemporal receptive fields. Ecologically relevant images, including prey-like objects such as flies, elicited bursts of excitation from single units.

Mosquito (Aedes aegypti) flight tones: frequency, harmonicity, spherical spreading, and phase relationships.

Mosquito flight produces a tone as a side effect of wing movement; this tone is also a communication signal that is frequency-modulated during courtship. Recordings of tones produced by tethered flying male and female Aedes aegypti were undertaken using pairs of pressure-gradient microphones above and below, ahead and behind, and to the left and right over a range of distances. Fundamental frequencies were close to those previously reported, although amplitudes were lower. The male fundamental frequency was higher than that of the female and males modulated it over a wider range. Analysis of harmonics shows that the first six partials were nearly always within 1 Hz of integer multiples of the fundamental, even when the fundamental was being modulated. Along the front-back axis, amplitude attenuated as a function of distance raised to the power 2.3. Front and back recordings were out of phase, as were above and below, while left and right were in phase. Recordings from ahead and behind showed quadratic phase coupling, while others did not. Finally, two methods are presented for separating simultaneous flight tones in a single recording and enhancing their frequency resolution. Implications for mosquito behavior are discussed.

Associative learning in the dengue vector mosquito, Aedes aegypti: avoidance of a previously attractive odor or surface color that is paired with an aversive stimulus.

Associative learning has been shown in a variety of insects, including the mosquitoes Culex quinquefasciatus and Anopheles gambiae. This study demonstrates associative learning for the first time in Aedes aegypti, an important vector of dengue, yellow fever and chikungunya viruses. This species prefers to rest on dark surfaces and is attracted to the odor of 1-octen-3-ol. After training in which a dark surface alone or a dark surface with odor was paired with electric shock, mosquitoes avoided the previously attractive area. The association was stronger when odor was included in training, was retained for at least 60 min but not for 24 h, and was equal for males and females. These results demonstrate the utility of a bulk-training paradigm for mosquitoes similar to that used with Drosophila melanogaster.

Classical conditioning through auditory stimuli in Drosophila: methods and models.

The role of sound in Drosophila melanogaster courtship, along with its perception via the antennae, is well established, as is the ability of this fly to learn in classical conditioning protocols. Here, we demonstrate that a neutral acoustic stimulus paired with a sucrose reward can be used to condition the proboscis-extension reflex, part of normal feeding behavior. This appetitive conditioning produces results comparable to those obtained with chemical stimuli in aversive conditioning protocols. We applied a logistic model with general estimating equations to predict the dynamics of learning, which successfully predicts the outcome of training and provides a quantitative estimate of the rate of learning. Use of acoustic stimuli with appetitive conditioning provides both an alternative to models most commonly used in studies of learning and memory in Drosophila and a means of testing hearing in both sexes, independently of courtship responsiveness.

Adaptive auditory risk assessment in the dogbane tiger moth when pursued by bats.

Moths and butterflies flying in search of mates risk detection by numerous aerial predators; under the cover of night, the greatest threat will often be from insectivorous bats. During such encounters, the toxic dogbane tiger moth, Cycnia tenera uses the received intensity, duration and emission pattern of the bat's echolocation calls to determine when, and how many, defensive ultrasonic clicks to produce in return. These clicks, which constitute an acoustic startle response, act as warning signals against bats in flight. Using an integrated test of stimulus generalization and dishabituation, here we show that C. tenera is able to discriminate between the echolocation calls characteristic of a bat that has only just detected it versus those of a bat actively in pursuit of it. We also show that C. tenera habituates more profoundly to the former stimulus train ('early attack') than to the latter ('late attack'), even though it was initially equally responsive to both stimuli. Matched sensory and behavioural data indicate that reduced responsiveness reflects habituation and is not merely attributable to sensory adaptation or motor fatigue. In search of mates in the face of bats, C. tenera's ability to discriminate between attacking bats representing different levels of risk, and to habituate less so to those most dangerous, should function as an adaptive cost-benefit trade-off mechanism in nature.

Neural responses to one- and two-tone stimuli in the hearing organ of the dengue vector mosquito.

Recent studies demonstrate that mosquitoes listen to each other's wing beats just prior to mating in flight. Field potentials from sound-transducing neurons in the antennae contain both sustained and oscillatory components to pure and paired tone stimuli. Described here is a direct comparison of these two types of response in the dengue vector mosquito, Aedes aegypti. Across a wide range of frequencies and intensities, sustained responses to one- and two-tone stimuli are about equal in magnitude to oscillatory responses to the beats produced by two-tone stimuli. All of these responses are much larger than the oscillatory responses to one-tone stimuli. Similarly, the frequency range extends up to at least the fifth harmonic of the male flight tone for sustained responses to one- and two-tone stimuli and oscillatory responses at the beat frequency of two-tone stimuli, whereas the range of oscillatory response to a one-tone stimulus is limited to, at most, the third harmonic. Thresholds near the fundamental of the flight tone are lower for oscillatory responses than for sustained deflections, lower for males than for females, and within the behaviorally relevant range. A simple model of the transduction process can qualitatively account for both oscillatory and sustained responses to pure and paired tones. These data leave open the question as to which of several alternative strategies underlie flight tone matching behavior in mosquitoes.