Effect of carrot supplementation on nutritional value of insects: a case study with Jamaican field cricket (Gryllus assimilis)

The fortification of feed is known to be a useful tool to manipulate the nutritional value of insects. This study aimed to reveal the effect of carrot supplement duration on the basic nutrients, fatty acid profile, carotenes, and tocopherols. Jamaican crickets (Gryllus assimilis) were provided with chicken feed supplemented with carrots ad libitum for 0, 3, 7, 14 and 60 days prior to harvest. The supplementation increased the levels of α-carotene and β-carotene in the insects. The content of carotenoids did not significantly differ between groups fed carrot for 14 (α-carotene = 13.7 μg/g DM; β-carotene = 34.6 μg/g DM) and 60 days (α-carotene = 15.2 μg/g DM; β-carotene = 37.2 μg/g DM), suggesting that the capacity of the insects to store carotenes is limited. Some carotenoids (α-carotene = 5.4 μg/g DM; β-carotene = 12.8 μg/g DM) were found in crickets given carrot supplementation for only 3 days prior to harvest. Carrot supplementation affected the fatty acid profile of the insects. Crickets fed carrot for 60 and 14 days contained lower levels of SFA (32.00 and 32.74% of total fatty acids respectively) and higher levels of PUFA (33.06 and 32.49% of total fatty acids respectively) in comparison with insects fed for 0, 3 or 7 days. No influence of carrot supplementation was observed in feed conversion, tocopherols and basic nutrients (proteins, lipids, ash). Conclusively, the paper showed some beneficial effects of carrot supplementation, when the highest levels of carotenoids were reached by 14 and 60 days of carrot provision. Therefore, the whole life supplementation seems to be not necessary to reach the increased content of carotenoids in crickets.

Transcriptional expression changes during compensatory plasticity in the prothoracic ganglion of the adult cricket Gryllus bimaculatus

Most adult organisms are limited in their capacity to recover from neurological damage. The auditory system of the Mediterranean field cricket, Gryllus bimaculatus, presents a compelling model for investigating neuroplasticity due to its unusual capabilities for structural reorganization into adulthood. Specifically, the dendrites of the central auditory neurons of the prothoracic ganglion sprout in response to the loss of auditory afferents. Deafferented auditory dendrites grow across the midline, a boundary they normally respect, and form functional synapses with the contralateral auditory afferents, restoring tuning-curve specificity. The molecular pathways underlying these changes are entirely unknown. Here, we used a multiple k-mer approach to re-assemble a previously reported prothoracic ganglion transcriptome that included ganglia collected one, three, and seven days after unilateral deafferentation in adult, male animals. We used EdgeR and DESeq2 to perform differential expression analysis and we examined Gene Ontologies to further understand the potential molecular basis of this compensatory anatomical plasticity. Enriched GO terms included those related to protein translation and degradation, enzymatic activity, and Toll signaling. Extracellular space GO terms were also enriched and included the upregulation of several protein yellow family members one day after deafferentation. Investigation of these regulated GO terms help to provide a broader understanding of the types of pathways that might be involved in this compensatory growth and can be used to design hypotheses around identified molecular mechanisms that may be involved in this unique example of adult structural plasticity.

Transcriptional expression changes during compensatory plasticity in the terminal ganglion of the adult cricket Gryllus bimaculatus

Background Damage to the adult central nervous system often leads to long-term disruptions in function due to the limited capacity for neurological recovery. The central nervous system of the Mediterranean field cricket, Gryllus bimaculatus, shows an unusual capacity for compensatory plasticity, most obviously in the auditory system and the cercal escape system. In both systems, unilateral sensory disruption leads the central circuitry to compensate by forming and/or strengthening connections with the contralateral sensory organ. While this compensatory plasticity in the auditory system relies on robust dendritic sprouting and novel synapse formation, the compensatory plasticity in the cercal escape circuitry shows little obvious dendritic sprouting and instead may rely on shifts in excitatory and inhibitory synaptic strength. Results In order to better understand what types of molecular pathways might underlie this compensatory shift in the cercal system, we used a multiple k-mer approach to assemble a terminal ganglion transcriptome that included ganglia collected one, three, and 7 days after unilateral cercal ablation in adult, male animals. We performed differential expression analysis using EdgeR and DESeq2 and examined Gene Ontologies to identify candidates potentially involved in this plasticity. Enriched GO terms included those related to the ubiquitin-proteosome protein degradation system, chromatin-mediated transcriptional pathways, and the GTPase-related signaling system. Conclusion Further exploration of these GO terms will provide a clearer picture of the processes involved in compensatory recovery of the cercal escape system in the cricket and can be compared and contrasted with the distinct pathways that have been identified upon deafferentation of the auditory system in this same animal.

Lifelong exposure to artificial light at night impacts stridulation and locomotion activity patterns in the cricket Gryllus bimaculatus

Living organisms experience a worldwide continuous increase in artificial light at night (ALAN), negatively affecting their behaviour. The field cricket, an established model in physiology and behaviour, can provide insights into the effect of ALAN on insect behaviour. The stridulation and locomotion patterns of adult male crickets reared under different lifelong ALAN intensities were monitored simultaneously for five consecutive days in custom-made anechoic chambers. Daily activity periods and acrophases were compared between the experimental groups. Control crickets exhibited a robust rhythm, stridulating at night and demonstrating locomotor activity during the day. By contrast, ALAN affected both the relative level and timing of the crickets' nocturnal and diurnal activity. ALAN induced free-running patterns, manifested in significant changes in the median and variance of the activity periods, and even arrhythmic behaviour. The magnitude of disruption was light intensity dependent, revealing an increase in the difference between the activity periods calculated for stridulation and locomotion in the same individual. This finding may indicate the existence of two peripheral clocks. Our results demonstrate that ecologically relevant ALAN intensities affect crickets’ behavioural patterns, and may lead to decoupling of locomotion and stridulation behaviours at the individual level, and to loss of synchronization at the population level.