Larval Light Research Articles

An OBP gene highly expressed in non-chemosensory tissues affects the phototaxis and reproduction of Spodoptera frugiperda.

Insect odorant binding proteins (OBPs) were initially regarded as carriers of the odorants involved in chemosensation. However, it had been observed that a growing number of OBP genes exhibited broad expression patterns beyond chemosensory tissues. Here, an OBP gene (OBP31) was found to be highly expressed in the larval ventral nerve cord, adult brain and male reproductive organ of Spodoptera frugiperda. An OBP31 knockout strain (OBP31-/- ) was generated by CRISPR/Cas9 mutagenesis. For OBP31-/- , the larvae needed longer time to pupate, but there was no difference in the pupal weight between OBP31-/- and wild type (WT). OBP31-/- larvae showed stronger phototaxis than the WT larvae, indicating the importance of OBP31 in light perception. For mating rhythm of adults, OBP31-/- moths displayed an earlier second mating peak. In the cross-pairing of OBP31-/- and WT moths, the mating duration was longer, and hatchability was lower in OBP31-/- group and OBP31+/- ♂ group than that in the WT group. These results suggested that OBP31 played a vital role in larval light perception and male reproductive process and could provide valuable insights into understanding the biological functions of OBPs that were not specific in chemosensory tissues.

Potential of Pueraria tuberosa (Willd.) DC. to rescue cognitive decline associated with BACE1 protein of Alzheimer's disease on Drosophila model: An integrated molecular modeling and in vivo approach

The indispensable role of Beta-site amyloid precursor protein cleaving enzyme-1 (BACE1) in Amyloid beta (Aβ) plaques generation and Aβ-mediated synaptic dysfunctions makes it a crucial target for therapeutic intervention in Alzheimer's disease (AD). In order to find out the potential inhibitors of BACE1, the present study focused on five phytochemicals from Pueraria tuberosa, namely, daidzin, genistin, mangiferin, puerarin, and tuberosin. A molecular docking study showed that all five phytochemicals presented the strongest BACE1 inhibition. Integrated molecular dynamics simulations and free energy calculations demonstrated that all five natural compounds have stable and favorable energies causing strong binding with the pocket site of BACE1 on 50 ns. All these molecules also passed Lipinski's rule of five. To validate the molecular modeling based findings, we primarily targeted the cognitive decline associated with BACE1 expression in AD flies with P. tuberosa. Significant improvement in cognitive decline was observed in AD flies in different behavioral assays such as Larval crawling assay (16.38%), Larval light preference assay (26.39%), Climbing assay (32.97%), Cold sensitivity assay (43.6%), and Thermal sensitivity assay (44.42%). The present findings suggest that P. tuberosa may be considered as a promising dietary supplement that can significantly ameliorate cognitive decline caused by BACE1 in Alzheimer's disease (AD).

<i>Drosophila</i> Larval Light Avoidance is Negatively Regulated by Temperature Through Two Pairs of Central Brain Neurons

Animal’s innate avoidance behavior is crucial for its survival. It subjects to modulation by environmental conditions in addition to the commanding sensorimotor transformation pathway. Although much has been known about the commanding neural basis, relatively less is known about how innate avoidance behavior is shaped by external conditions. Here in this paper, we report that Drosophila larvae showed stronger light avoidance at lower temperatures than at higher temperatures. Such negative regulation of light avoidance by temperature was abolished by blocking two pairs of central brain neurons, ACLPR60F09 neurons, that were responsive to both light and temperature change, including cooling and warming. ACLPR60F09 neurons could be excited by pdf-LaN neurons in the visual pathway. On the downstream side, they could inhibit the CLPNR82B09 neurons that command light induced reorientation behavior. Compared with at warm temperature, ACLPR60F09 neurons’ response to light was decreased at cool temperature so that the inhibition on CLPNR82B09 neurons was relieved and the light induced avoidance was enhanced. Our result proposed a neural mechanism underlying cross-modal modulation of animal innate avoidance behavior.

Light Spot-Based Assay for Analysis of Drosophila Larval Phototaxis.

The larvae of Drosophila melanogaster show obvious light-avoiding behavior during the foraging stage. Drosophila larval phototaxis can be used as a model to study animal avoidance behavior. This protocol introduces a light-spot assay to investigate larval phototactic behavior. The experimental set-up includes two main parts: a visual stimulation system that generates the light spot, and an infrared light-based imaging system that records the process of larval light avoidance. This assay allows tracking of the behavior of larva before entering, during encountering, and after leaving the light spot. Details of larval movement including deceleration, pause, head casting, and turning can be captured and analyzed using this method.

Wood-Based Cellulose Nanofibrils: Haemocompatibility and Impact on the Development and Behaviour of Drosophila melanogaster.

Wood-based cellulose nanofibrils (CNF) offer an excellent scaffold for drug-delivery formulation development. However, toxicity and haemocompatibility of the drug carrier is always an important issue. In this study, toxicity-related issues of CNF were addressed. Different doses of CNF were orally administered to Drosophila and different tests like the developmental cycle, trypan blue exclusion assay, larva crawling assay, thermal sensitivity assay, cold sensitivity assay, larval light preference test, climbing behaviour, nitroblue tetrazolium (NBT) reduction assay, adult phenotype, and adult weight were conducted to observe the impact on its development and behaviour. A haemocompatibility assay was done on the blood taken from healthy Wistar rats. In Drosophila, the abnormalities in larval development and behaviour were observed in the behavioural assays. However, the cytotoxic effect could not be confirmed by the gut staining and level of reactive oxygen species. The larvae developed into an adult without any abnormality in the phenotype. The CNF did cause loss of weight in the adult flies and did not cause much toxicity within the body since there was no phenotypic defect. Hemolysis data also suggested that CNF was safe at lower doses, as the data was well within acceptable limits. All these results suggest that cellulose nanofibres have no significant cytotoxic effects on Drosophila. However, the developmental and behavioural abnormalities suggest that CNF may act as a behavioural teratogen.

A disinhibitory mechanism biases Drosophila innate light preference

Innate preference toward environmental conditions is crucial for animal survival. Although much is known about the neural processing of sensory information, how the aversive or attractive sensory stimulus is transformed through central brain neurons into avoidance or approaching behavior is largely unclear. Here we show that Drosophila larval light preference behavior is regulated by a disinhibitory mechanism. In the disinhibitory circuit, a pair of GABAergic neurons exerts tonic inhibition on one pair of contralateral projecting neurons that control larval reorientation behavior. When a larva enters the light area, the reorientation-controlling neurons are disinhibited to allow reorientation to occur as the upstream inhibitory neurons are repressed by light. When the larva exits the light area, the inhibition on the downstream neurons is restored to repress further reorientation and thus prevents the larva from re-entering the light area. We suggest that disinhibition may serve as a common neural mechanism for animal innate preference behavior.

Two Pairs of Drosophila Central Brain Neurons Mediate Larval Navigational Strategies Based on Temporal Light Information Processing.

Some animals are attracted by sun light, others are highly repulsed by it. Especially for slowly moving animals, such as Drosophila larvae, direct sunlight may be perceived as noxious stimulus as it increases the risk of desiccation, DNA-damaging by UV-light and exposure to predators. For several reasons, model organisms like Drosophila larvae are well-suited for investigating how light cues are translated into an appropriate behavioral output. First, many of the genetic tools, which were created for use in adult fruit flies, work also in larvae. Second, the lower number of cells in Drosophila larvae compared to adults makes this system adequate for reconstructing neural circuits. Third, the relatively simple behavioral repertoire of larvae facilitates the study of basic functions like navigation with regards to light. Larvae navigate robustly away from a light source by the use of several sophisticated behavioral strategies which are based on temporal or spatial information processing. Two central brain neurons, the NP394-neurons, are highly important for larval light avoidance. It was even reported that these cells seem to play a functional role in a putative larval light preference switch right before pupation. However, the exact function of the NP394-neurons in light navigation remains unknown. We here show that the functional role of NP394-neurons in larval light navigation is restricted to behaviors based on temporal information processing, but not for spatial navigation.

Turns with multiple and single head cast mediate Drosophila larval light avoidance.

Drosophila larvae exhibit klinotaxis when placed in a gradient of temperature, chemicals, or light. The larva samples environmental stimuli by casting its head from side to side. By comparing the results of two consecutive samples, it decides the direction of movement, appearing as a turn proceeded by one or more head casts. Here by analyzing larval behavior in a light-spot-based phototaxis assay, we showed that, in addition to turns with a single cast (1-cast), turns with multiple head casts (n-cast) helped to improve the success of light avoidance. Upon entering the light spot, the probability of escape from light after the first head cast was only ~30%. As the number of head casts increased, the chance of successful light avoidance increased and the overall chance of escaping from light increased to >70%. The amplitudes of first head casts that failed in light avoidance were significantly smaller in n-cast turns than those in 1-cast events, indicating that n-cast turns might be planned before completion of the first head cast. In n-casts, the amplitude of the second head cast was generally larger than that of the first head cast, suggesting that larvae tried harder in later attempts to improve the efficacy of light avoidance. We propose that both 1-cast turns and n-cast turns contribute to successful larval light avoidance, and both can be initiated at the first head cast.

First direct confirmation of grass carp spawning in a Great Lakes tributary

Abstract Grass carp (Ctenopharyngodon idella), an invasive species of Asian carp, has been stocked for many decades in the United States for vegetation control. Adult individuals have been found in all of the Great Lakes except Lake Superior, but no self-sustaining populations have yet been identified in Great Lakes tributaries. In 2012, a commercial fisherman caught four juvenile diploid grass carp in the Sandusky River, a major tributary to Lake Erie. Otolith microchemistry and the capture location of these fish permitted the conclusion that they were most likely produced in the Sandusky River. Due to this finding, we sampled ichthyoplankton using paired bongo net tows and larval light traps during June–August of 2014 and 2015 to determine if grass carp are spawning in the Sandusky River. From the samples collected in 2015, we identified and staged eight eggs that were morphologically consistent with grass carp. Five eggs were confirmed as grass carp using quantitative Polymerase Chain Reaction for a grass carp-specific marker, while the remaining three were retained for future analysis. Our finding confirms that grass carp are naturally spawning in this Great Lakes tributary. All eggs were collected during high-flow events, either on the day of peak flow or 1–2 days following peak flow, supporting an earlier suggestion that high flow conditions favor grass carp spawning. The next principal goal is to identify the spawning and hatch location(s) for the Sandusky River. Predicting locations and conditions where grass carp spawning is most probable may aid targeted management efforts.

Searching behaviour of Dolichogenidea tasmanica in response to susceptible instars of Epiphyas postvittana

Dolichogenidea tasmanica (Hymenoptera: Braconidae) is the most commonly reared parasitoid from larval light brown apple moth (LBAM), Epiphyas postvittana (Lepidoptera: Tortricidae), feeding on grapevines in Australia. In order to evaluate the efficiency of searching behaviour of D. tasmanica, a laboratory study was undertaken to determine how this wasp responds to the susceptible stages of larval LBAM. Observations of searching behaviour were made in a wind tunnel, which allowed the wasp to express its full range of behaviour. The behaviour of D. tasmanica and susceptibility of LBAM to parasitism varies significantly among instars. The wasp most readily parasitises newly hatched larvae, but can parasitise the first three of the six instars. The first instars cause less damage and also produce less faeces and silk than later instars, so they are associated with less volatile cues that may be detected by the parasitoid. Flight initiation to an infested leaf was lower in the presence of first instars compared with second and third instars. The flight duration was shortest when females were exposed to plants infested by third instars. An analysis of the sequence and timing of searching behaviour indicated that females respond differently to each of the instars of LBAM.

γ‐glutamyl transpeptidase 1 specifically suppresses green‐light avoidance via GABAA receptors in Drosophila

Drosophila larvae innately show light avoidance behavior. Compared with robust blue-light avoidance, larvae exhibit relatively weaker green-light responses. In our previous screening for genes involved in larval light avoidance, compared with control w(1118) larvae, larvae with γ-glutamyl transpeptidase 1 (Ggt-1) knockdown or Ggt-1 mutation were found to exhibit higher percentage of green-light avoidance which was mediated by Rhodopsin6 (Rh6) photoreceptors. However, their responses to blue light did not change significantly. By adjusting the expression level of Ggt-1 in different tissues, we found that Ggt-1 in malpighian tubules was both necessary and sufficient for green-light avoidance. Our results showed that glutamate levels were lower in Ggt-1 null mutants compared with controls. Feeding Ggt-1 null mutants glutamate can normalize green-light avoidance, indicating that high glutamate concentrations suppressed larval green-light avoidance. However, rather than directly, glutamate affected green-light avoidance indirectly through GABA, the level of which was also lower in Ggt-1 mutants compared with controls. Mutants in glutamate decarboxylase 1, which encodes GABA synthase, and knockdown lines of the GABAA receptor, both exhibit elevated levels of green-light avoidance. Thus, our results elucidate the neurobiological mechanisms mediating green-light avoidance, which was inhibited in wild-type larvae.

Fleeing heat and light

Fleeing heat and light

Selective mortality during the larval and juvenile stages of snappers (Lutjanidae) and great barracuda Sphyraena barracuda

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 474:227-242 (2013) - DOI: https://doi.org/10.3354/meps10114 Selective mortality during the larval and juvenile stages of snappers (Lutjanidae) and great barracuda Sphyraena barracuda E. K. D’Alessandro*, S. Sponaugle, R. K. Cowen Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Causeway, Miami, Florida 33149, USA *Email: edalessa@rsmas.miami.edu ABSTRACT: Selective mortality during the early life stages in marine organisms can affect the magnitude and composition of recruitment, yet these processes have not been examined in economically important predatory coral reef fishes. Utilizing 3 different stage-specific sampling techniques (shipboard plankton tows, larval light traps, juvenile surveys/seines), we repeatedly sampled multiple cohorts of 3 lutjanid (Ocyurus chrysurus, Lutjanus synagris, and L. griseus) and 1 sphyraenid (Sphyraena barracuda) species through time in the Florida Keys (USA). Comparisons of daily growth and size-at-age (from otolith microstructure analysis) for early- and late-stage larvae and young and older juveniles revealed that size- and growth-selective processes operate during the larval stage, while after settlement, growth-selective mortality occurred in the absence of significant size differences. In all 3 lutjanid species, larvae and juveniles that were larger at hatch preferentially survived. In O. chrysurus and L. synagris, selective mortality of smaller, slower-growing individuals during the larval stage reduced variability in these traits such that larvae were of similar sizes at settlement. Following settlement, patterns of growth-selective mortality were initially opposite (favoring faster juvenile growth in L. synagris, and slower growth in O. chrysurus), but ultimately survivors of both species grew faster, leading eventually to a size advantage. In contrast, patterns of selective mortality were not evident until settlement in L. griseus and S. barracuda, and favored larger and smaller sizes-at-settlement, respectively. Overall, our results reveal important patterns of selective mortality and variability between even closely related species. KEY WORDS: Ocyurus chrysurus · Lutjanus synagris · Lutjanus griseus · Growth-mortality hypothesis · Coral reef fishes Full text in pdf format Supplementary material PreviousNextCite this article as: D’Alessandro EK, Sponaugle S, Cowen RK (2013) Selective mortality during the larval and juvenile stages of snappers (Lutjanidae) and great barracuda Sphyraena barracuda . Mar Ecol Prog Ser 474:227-242. https://doi.org/10.3354/meps10114 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 474. Online publication date: January 31, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

A Mechanism for Circadian Control of Pacemaker Neuron Excitability

Although the intracellular molecular clocks that regulate circadian (~24 h) behavioral rhythms are well understood, it remains unclear how molecular clock information is transduced into rhythmic neuronal activity that in turn drives behavioral rhythms. To identify potential clock outputs, the authors generated expression profiles from a homogeneous population of purified pacemaker neurons (LN(v)s) from wild-type and clock mutant Drosophila. They identified a group of genes with enriched expression in LN(v)s and a second group of genes rhythmically expressed in LN(v)s in a clock-dependent manner. Only 10 genes fell into both groups: 4 core clock genes, including period (per) and timeless (tim), and 6 genes previously unstudied in circadian rhythms. The authors focused on one of these 6 genes, Ir, which encodes an inward rectifier K(+) channel likely to regulate resting membrane potential, whose expression peaks around dusk. Reducing Ir expression in LN(v)s increased larval light avoidance and lengthened the period of adult locomotor rhythms, consistent with increased LN(v) excitability. In contrast, increased Ir expression made many adult flies arrhythmic and dampened PER protein oscillations. The authors propose that rhythmic Ir expression contributes to daily rhythms in LN(v) neuronal activity, which in turn feed back to regulate molecular clock oscillations.

Balance of Activity between LNvs and Glutamatergic Dorsal Clock Neurons Promotes Robust Circadian Rhythms in Drosophila

Circadian rhythms offer an excellent opportunity to dissect the neural circuits underlying innate behavior because the genes and neurons involved are relatively well understood. We first sought to understand how Drosophila clock neurons interact in the simple circuit that generates circadian rhythms in larval light avoidance. We used genetics to manipulate two groups of clock neurons, increasing or reducing excitability, stopping their molecular clocks, and blocking neurotransmitter release and reception. Our results revealed that lateral neurons (LN(v)s) promote and dorsal clock neurons (DN(1)s) inhibit light avoidance, these neurons probably signal at different times of day, and both signals are required for rhythmic behavior. We found that similar principles apply in the more complex adult circadian circuit that generates locomotor rhythms. Thus, the changing balance in activity between clock neurons with opposing behavioral effects generates robust circadian behavior and probably helps organisms transition between discrete behavioral states, such as sleep and wakefulness.

Distinct Visual Pathways MediateDrosophilaLarval Light Avoidance and Circadian Clock Entrainment

Visual organs perceive environmental stimuli required for rapid initiation of behaviors and can also entrain the circadian clock. The larval eye of Drosophila is capable of both functions. Each eye contains only 12 photoreceptors (PRs), which can be subdivided into two subtypes. Four PRs express blue-sensitive rhodopsin5 (rh5) and eight express green-sensitive rhodopsin6 (rh6). We found that either PR-subtype is sufficient to entrain the molecular clock by light, while only the Rh5-PR subtype is essential for light avoidance. Acetylcholine released from PRs confers both functions. Both subtypes of larval PRs innervate the main circadian pacemaker neurons of the larva, the neuropeptide PDF (pigment-dispersing factor)-expressing lateral neurons (LNs), providing sensory input to control circadian rhythms. However, we show that PDF-expressing LNs are dispensable for light avoidance, and a distinct set of three clock neurons is required. Thus we have identified distinct sensory and central circuitry regulating light avoidance behavior and clock entrainment. Our findings provide insights into the coding of sensory information for distinct behavioral functions and the underlying molecular and neuronal circuitry.

NinaB Is Essential for Drosophila Vision but Induces Retinal Degeneration in Opsin-deficient Photoreceptors

In animals, visual pigments are essential for photoreceptor function and survival. These G-protein-coupled receptors consist of a protein moiety (opsin) and a covalently bound 11-cis-retinylidene chromophore. The chromophore is derived from dietary carotenoids by oxidative cleavage and trans-to-cis isomerization of double bonds. In vertebrates, the necessary chemical transformations are catalyzed by two distinct but structurally related enzymes, the carotenoid oxygenase beta-carotenoid-15,15'-monooxygenase and the retinoid isomerase RPE65 (retinal pigment epithelium protein of 65 kDa). Recently, we provided biochemical evidence that these reactions in insects are catalyzed by a single enzyme family member named NinaB. Here we show that in the fly pathway, carotenoids are mandatory precursors of the chromophore. After chromophore formation, the retinoid-binding protein Pinta acts downstream of NinaB and is required to supply photoreceptors with chromophore. Like ninaE encoding the opsin, ninaB expression is eye-dependent and is activated as a downstream target of the eyeless/pax6 and sine oculis master control genes for eye development. The requirement for coordinated synthesis of chromophore and opsin is evidenced by analysis of ninaE mutants. Retinal degeneration in opsin-deficient photoreceptors is caused by the chromophore and can be prevented by restricting its supply as seen in an opsin and chromophore-deficient double mutant. Thus, our study identifies NinaB as a key component for visual pigment production and provides evidence that chromophore in opsin-deficient photoreceptors can elicit retinal degeneration.

Larval Fish Use of Dike Structures on a Navigable River

AbstractIn rivers, velocity shelters are thought to serve as limiting factors in the retention and recruitment of young fish. Such shelters are formed in backwaters and tributaries; however, these areas are limited in many North American rivers. In response to this concern, several dike sites that serve as low‐velocity zones were placed within the Kanawha River (West Virginia), a sixth‐order tributary of the Ohio River. This study was conducted to evaluate whether the dike sites (finger and zipper dikes) provided velocity shelters that are used by larval fish. Larval fish were sampled during 2002 and 2003 using larval light traps. Larval fishes collected were typical of large river systems; Cyprinidae, Percidae, and Centrarchidae were the most abundant families. Results show that larval abundances peaked during late June in 2002 and early July in 2003. Overall taxonomic composition did not differ between dike sites and reference sites. Throughout the study, larval fish were captured at significantly higher rates (P < 0.001) at dike sites than at high‐ and low‐quality reference areas. Water velocities were significantly lower (P < 0.001) at dike sites than at reference areas, suggesting that the greater larval fish use of dike sites may be attributed to reduced velocity provided by the structures. This study suggests that dike sites can serve as velocity shelters and retention areas for larval fish in navigationally impacted rivers.

Reproduction by June Sucker in a Refuge Population: Successful Spawning in a Lake Habitat

Abstract The June sucker (Chasmistes liorus) is an endangered lake sucker endemic to Utah Lake, Utah. As part of recovery actions, June suckers were introduced into Red Butte Reservoir, Utah, as a wild grow-out site. Since their introduction, June suckers have successfully reproduced in Red Butte Reservoir, producing a large population in this refuge. I used passive egg collectors (egg traps and nets) and observational surveys to determine the location of spawning sites within the reservoir, and larval light trapping to determine successful recruitment (i.e., egg survival through larval swim-up) at these sites. Eggs were collected between 18 June and 15 July at 2 general sites along or near the reservoir's dam, although spawning was only observed at 1 of these sites. Suckers were not observed at, and eggs were not collected in or around, the mouth of Red Butte Creek as expected. At the site where spawning was observed, suckers were spawning over gravel substrates (mean diameter = 32 mm) at depths of 0.5–1...

Florida Current frontal eddies and the settlement of coral reef fishes

We deployed three replicate larval light traps off the upper Florida Keys from June-September 2001 to measure the delivery of settlement-stage fish larvae to the coral reefs. Nightly measures of larval abundance were compared to water temperatures measured across the outer reef, nearby wind records, and the alongshore and cross-shelf components of the currents measured at the seaward edge of the reef. These time series, together with satellitederived sea surface temperature and color fields indicate that a very large multi-taxa larval pulse on 20 July was directly associated with the passage of a Florida Current (FC) sub-mesoscale frontal eddy embedded within the elongated remnant of a mesoscale eddy. A second large pulse of larvae occurred when a similar mesoscale eddy passed the upper Keys in mid-June. Periods of increased tidal bore activity occurred with the passage of these eddies. Semidiurnal internal tides caused near-bottom onshore intrusions of cooler slope waters during periods of onshore meanders of the FC front when the downstream baroclinic flow and stratification increased at the reef margin. The high abundance and similarity in larval ages within taxa on 20 July indicate a Keys shelf origin, although the temporal and spatial scales of entrainment cannot be resolved. The passage of a third mesoscale eddy in September did not result in a larval pulse, possibly because of a mismatch between biological and physical criteria, several of which must be met for larval transport by mesoscale eddies to be successful.