Asymmetric ommatidia count and behavioural lateralization in the ant Temnothorax albipennis

Lateralised courtship behaviour and its impact on mating success in Ostrinia furnacalis (Lepidoptera: Crambidae)

Lateralisation is a well-established phenomenon observed in an increasing number of insect species. This study aims to obtain basic details on lateralisation in courtship and mating behaviour in Ostrinia furnacalis, the Asian corn borer. We conducted laboratory investigations to observe lateralisation in courtship and mating behaviours in adult O. furnacalis. Our goal was also to detect lateralised mating behaviour variations during sexual interactions and to elucidate how these variances might influence the mating success of males. Our findings reveal two distinct lateralised traits: male approaches from the right or left side of the female and the direction of male turning displays. Specifically, males approaching females from their right side predominantly exhibited left-biased 180° turning displays, while males approaching females from the left-side primarily displayed right-biased 180° turning displays. Notably, left-biased males, executing a 180° turn for end-to-end genital contact, initiated copulation with fewer attempts and began copulation earlier than their right-biased approaches with left-biased 180° turning displays. Furthermore, mating success was higher when males subsequently approached the right side of females during sexual encounters. Left-biased 180° turning males exhibited a higher number of successful mating interactions. These observations provide the first report on lateralisation in the reproductive behaviour of O. furnacalis under controlled laboratory conditions and hold promise for establishing reliable benchmarks for assessing and monitoring the quality of mass-produced individuals in pest control efforts.

A Meniscus Multifocusing Compound Eye Camera Based on Negative Pressure Forming Technology

To meet the challenge of preparing a high-resolution compound eye, this paper proposes a multi-focal-length meniscus compound eye based on MEMS negative pressure molding technology. The aperture is increased, a large field of view angle of 101.14° is obtained, and the ommatidia radius of each stage is gradually increased from 250 μm to 440 μm. A meniscus structure is used to improve the imaging quality of the marginal compound eye so that its resolution can reach 36.00 lp/mm. The prepared microlenses have a uniform shape and a smooth surface, and both panoramic image stitching and moving object tracking are achieved. This technology has great potential for application in many fields, including automatic driving, machine vision, and medical endoscopy.

Searching Behavior in the Tropical Fire Ant Solenopsis geminata (Hymenoptera: Formicidae)

Social insects have evolved different search strategies to find target objects in unknown environments. In the present study, the searching behavior of the tropical fire ant Solenopsis geminata was investigated in a circular arena. The average time, search path, speed, and search patterns of worker ants in a circular arena were determined. The results showed that fire ant workers followed six major search patterns. The variation in the searching patterns of workers may explain the different levels of exploration. Most workers (56.8%) tended to search in small loops and progressively increase the search area size. These workers mostly turned in one direction, either clockwise or counterclockwise. More workers turned in a consistent pattern than in an inconsistent pattern. Moving speed was also higher in workers that maintained their turning directions than in those that changed directions. We thus propose that following search patterns consisting of loops of increasing size may be an effective strategy. The tropical fire ant S. geminata is a globally invasive species that was introduced to Taiwan 40 years ago and has continued to threaten residents. Based on behavioral studies of S. geminata, we may gain a better understanding of their exploratory behavior in the ecosystem in Taiwan.

Allometry for Eyes and Optic Lobes in Oval Squid (Sepioteuthis lessoniana) with Special Reference to Their Ontogenetic Asymmetry

Eyes develop in relation to body size and brain area for visual processing in some vertebrates. Meanwhile, it is well known that many animals exhibit left–right asymmetry in both morphology and behavior, namely, lateralization. However, it remains unclear whether the eyes and visual processing brain areas synchronously develop for their asymmetry. Oval squid (Sepioteuthis lessoniana) exhibits lateralization of optic lobe volume and left or right eye usage toward specific targets during their ontogeny. We address the question of how left–right asymmetry of the eyes and optic lobes exhibit an allometric pattern. To examine this question, we estimated the left and right volumes of eyes and optic lobes using microcomputed tomography. We found that, for the optic lobe volume, the right enlargement that appeared at ages 45 and 80 days then shifted to the left at age 120 days. In contrast, the volume of eyes did not show any left–right asymmetries from hatching to age 120 days. We also found that the volume of the eyes and optic lobes showed a slower increase than that of the whole-body size. Within these two visually related organs, the eyes grew faster than the optic lobes until age 120 days. These results are discussed in the context of the survival strategy of oval squid that form schools, two months post-hatching.

Temporal and structural neural asymmetries in insects

Neural asymmetries of the bilateral parts of the nervous system are found throughout the animal kingdom. The relative low complexity and experimental accessibility of the insect nervous system makes it well suited for studying the functions of neural asymmetries and their underlying mechanisms. Recent findings in insects reveal hardwired asymmetries in their peripheral and central nervous systems, which affect sensory perception, motor behaviours and cognitive-related tasks. Together, these findings underscore the tendency of the nervous system to segregate between the activities of its right and left sides either transiently or as permanent lateralized specializations.

Biomimetic apposition compound eye fabricated using microfluidic-assisted 3D printing

After half a billion years of evolution, arthropods have developed sophisticated compound eyes with extraordinary visual capabilities that have inspired the development of artificial compound eyes. However, the limited 2D nature of most traditional fabrication techniques makes it challenging to directly replicate these natural systems. Here, we present a biomimetic apposition compound eye fabricated using a microfluidic-assisted 3D-printing technique. Each microlens is connected to the bottom planar surface of the eye via intracorporal, zero-crosstalk refractive-index-matched waveguides to mimic the rhabdoms of a natural eye. Full-colour wide-angle panoramic views and position tracking of a point source are realized by placing the fabricated eye directly on top of a commercial imaging sensor. As a biomimetic analogue to naturally occurring compound eyes, the eye's full-colour 3D to 2D mapping capability has the potential to enable a wide variety of applications from improving endoscopic imaging to enhancing machine vision for facilitating human-robot interactions.

Variability of an Early Developmental Cell Population Underlies Stochastic Laterality Defects

Embryonic development seemingly proceeds with almost perfect precision. However, it is largely unknown how much underlying microscopic variability is compatible with normal development. Here, we quantify embryo-to-embryo variability in vertebrate development by studying cell number variation in the zebrafish endoderm. We notice that the size of a sub-population of the endoderm, the dorsal forerunner cells (DFCs, which later form the left-right organizer), exhibits significantly more embryo-to-embryo variation than the rest of the endoderm. We find that, with incubation of the embryos at elevated temperature, the frequency of left-right laterality defects is increased drastically in embryos with a low number of DFCs. Furthermore, we observe that these fluctuations have a large stochastic component among fish of the same genetic background. Hence, a stochastic variation in early development leads to a remarkably strong macroscopic phenotype. These fluctuations appear to be associated with maternal effects in the specification of the DFCs.

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High embryo-to-embryo variability of dorsal forerunner cell numbers

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Fluctuations of dorsal forerunner cells have a large stochastic component

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Embryos with fewer dorsal forerunner cells frequently develop laterality defects

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Variability of dorsal forerunner cell numbers is associated to maternal effects

Laterality in foraging phalaropes promotes phenotypically assorted groups

Asymmetry of the brain and behavior (lateralization) is widespread in the animal kingdom and could be particularly advantageous for gregarious organisms. Here, we investigate the possibility that lateralized behaviors affect the structure of foraging flocks. Phalaropes (Scolopacidae: Phalaropus) are highly aquatic shorebirds and the only vertebrates that spin on the water to feed, often in large flocks. There is anecdotal evidence that individuals spin in a single direction and that those spinning counter the majority are usually found at the periphery of a flock. Although such phenotypic segregation may reduce interference among socially foraging birds, its extent and underlying mechanism remain unexplored. Using over 900 spinning bouts from freely available video repositories, we find support for individual, but not population, lateralization of spinning in the three phalarope species. Although spinning direction was not determined by the position occupied within a flock (periphery vs. core), nearest neighbors were more likely to spin in the same direction; moreover, they were three times less likely to interfere with each other when aligning spinning direction. Our results indicate that a simple rule (keep foraging with similarly lateralized individuals) can generate self-organized interactions among flockmates, resulting in groups phenotypically assorted.

The Bayesian superorganism: externalized memories facilitate distributed sampling

A key challenge for any animal (or sampling technique) is to avoid wasting time by searching for resources (information) in places already found to be unprofitable. In biology, this challenge is particularly strong when the organism is a central place forager—returning to a nest between foraging bouts—because it is destined repeatedly to cover much the same ground. This problem will be particularly acute if many individuals forage from the same central place, as in social insects such as the ants. Foraging (sampling) performance may be greatly enhanced by coordinating movement trajectories such that each ant (walker) visits separate parts of the surrounding (unknown) space. We find experimental evidence for an externalized spatial memory in Temnothorax albipennis ants: chemical markers (either pheromones or cues such as cuticular hydrocarbon footprints) that are used by nest-mates to mark explored space. We show these markers could be used by the ants to scout the space surrounding their nest more efficiently through indirect coordination. We also develop a simple model of this marking behaviour that can be applied in the context of Markov chain Monte Carlo methods (Baddeley et al. 2019 J. R. Soc. Interface16, 20190162 (doi:10.1098/rsif.2019.0162)). This substantially enhances the performance of standard methods like the Metropolis–Hastings algorithm in sampling from sparse probability distributions (such as those confronted by the ants) with only a little additional computational cost. Our Bayesian framework for superorganismal behaviour motivates the evolution of exploratory mechanisms such as trail marking in terms of enhanced collective information processing.

Optimal foraging and the information theory of gambling

At a macroscopic level, part of the ant colony life cycle is simple: a colony collects resources; these resources are converted into more ants, and these ants in turn collect more resources. Because more ants collect more resources, this is a multiplicative process, and the expected logarithm of the amount of resources determines how successful the colony will be in the long run. Over 60 years ago, Kelly showed, using information theoretic techniques, that the rate of growth of resources for such a situation is optimized by a strategy of betting in proportion to the probability of pay-off. Thus, in the case of ants, the fraction of the colony foraging at a given location should be proportional to the probability that resources will be found there, a result widely applied in the mathematics of gambling. This theoretical optimum leads to predictions as to which collective ant movement strategies might have evolved. Here, we show how colony-level optimal foraging behaviour can be achieved by mapping movement to Markov chain Monte Carlo (MCMC) methods, specifically Hamiltonian Monte Carlo (HMC). This can be done by the ants following a (noisy) local measurement of the (logarithm of) resource probability gradient (possibly supplemented with momentum, i.e. a propensity to move in the same direction). This maps the problem of foraging (via the information theory of gambling, stochastic dynamics and techniques employed within Bayesian statistics to efficiently sample from probability distributions) to simple models of ant foraging behaviour. This identification has broad applicability, facilitates the application of information theory approaches to understand movement ecology and unifies insights from existing biomechanical, cognitive, random and optimality movement paradigms. At the cost of requiring ants to obtain (noisy) resource gradient information, we show that this model is both efficient and matches a number of characteristics of real ant exploration.

Complementary Specializations of the Left and Right Sides of the Honeybee Brain

Honeybees show lateral asymmetry in both learning about odors associated with reward and recalling memory of these associations. We have extended this research to show that bees exhibit lateral biases in their initial response to odors: viz., turning toward the source of an odor presented on their right side and turning away from it when presented on their left side. The odors we presented were the main component of the alarm pheromone, isoamyl acetate (IAA), and four floral scents. The significant bias to turn toward IAA odor on the right and away from it on the left is, we argue, a lateralization of the fight-flight response elicited by this pheromone. It contrasts to an absence of any asymmetry in the turning response to an odor of the flowers on which the bees had been feeding prior to testing: to this odor they turned toward when it was presented on either the left or right side. Lemon and orange odors were responded to differently on the left and right sides (toward on the right, away on the left), but no asymmetry was found in responses to rose odor. Our results show that side biases are present even in the initial, orienting response of bees to certain odors.

Innate turning preference of leaf-cutting ants in the absence of external orientation cues

Many ants use a combination of cues for orientation but how do ants find their way when all external cues are suppressed? Do they walk in a random way or are their movements spatially oriented? Here we show for the first time that leaf-cutting ants (Acromyrmex lundii) have an innate preference of turning counter-clockwise (left) when external cues are precluded. We demonstrated this by allowing individual ants to run freely on the water surface of a newly-developed treadmill. The surface tension supported medium-sized workers but effectively prevented ants from reaching the wall of the vessel, important to avoid wall-following behaviour (thigmotaxis). Most ants ran for minutes on the spot but also slowly turned counter-clockwise in the absence of visual cues. Reconstructing the effectively walked path revealed a looping pattern which could be interpreted as a search strategy. A similar turning bias was shown for groups of ants in a symmetrical Y-maze where twice as many ants chose the left branch in the absence of optical cues. Wall-following behaviour was tested by inserting a coiled tube before the Y-fork. When ants traversed a left-coiled tube, more ants chose the left box and vice versa. Adding visual cues in form of vertical black strips either outside the treadmill or on one branch of the Y-maze led to oriented walks towards the strips. It is suggested that both, the turning bias and the wall-following are employed as search strategies for an unknown environment which can be overridden by visual cues.