Diet induced modifications of fatty-acid composition in mealworm larvae (Tenebrio molitor)

The diet of Western human societies is characterized by an excess of saturated fatty acids (FAs) and a high concentration of ω-6 relative to ω-3 polyunsaturated FA (PUFA). These unbalanced diets are suspected to trigger diseases and disorders. To alleviate this public health concern, the production of healthier meat with more PUFAs of higher ω-3 concentration could potentially be achieved by modifying livestock diets. The high nutritional value and limited breeding costs of edible insects have brought insect feed into the discussion as a promising fat source for animal and human diets. In this study, we sought to increase the amount of ω-3 PUFAs in mealworm (Tenebrio molitor) larvae. We investigated the effects of diets varying in ω-3/ω-6 ratio and FA concentration but similar in PUFA proportion on larva FA composition. Mealworm larvae showed significant plasticity in lipid composition. High dietary ω-3/ω-6 ratios induced an increase in the proportion of ω-3 and a decrease in ω-6, which resulted in higher larval ω-3/ω-6 ratios, but also in higher larval PUFA proportion. Increasing FA concentrations in larva diets also favored the accumulation of PUFAs to the detriment of monounsaturated and saturated FAs. Providing ω-3-rich seeds to mealworm larvae could allow the production of economical animal fat with healthier PUFA percentages (> 60%) and ω-3/ω-6 ratios (>0.5)

Bat responses to climate change: a systematic review

This is the final version. Available on open access from Wiley via the DOI in this recordUnderstanding how species respond to climate change is key to informing vulnerability assessments and designing effective conservation strategies, yet research efforts on wildlife responses to climate change fail to deliver a representative overview due to inherent biases. Bats are a species-rich, globally distributed group of organisms that are thought to be particularly sensitive to the effects of climate change because of their high surface-to-volume ratios and low reproductive rates. We systematically reviewed the literature on bat responses to climate change to provide an overview of the current state of knowledge, identify research gaps and biases and highlight future research needs. We found that studies are geographically biased towards Europe, North America and Australia, and temperate and Mediterranean biomes, thus missing a substantial proportion of bat diversity and thermal responses. Less than half of the published studies provide concrete evidence for bat responses to climate change. For over a third of studied bat species, response evidence is only based on predictive species distribution models. Consequently, the most frequently reported responses involve range shifts (57% of species) and changes in patterns of species diversity (26%). Bats showed a variety of responses, including both positive (e.g. range expansion and population increase) and negative responses (range contraction and population decrease), although responses to extreme events were always negative or neutral. Spatial responses varied in their outcome and across families, with almost all taxonomic groups featuring both range expansions and contractions, while demographic responses were strongly biased towards negative outcomes, particularly among Pteropodidae and Molossidae. The commonly used correlative modelling approaches can be applied to many species, but do not provide mechanistic insight into behavioural, physiological, phenological or genetic responses. There was a paucity of experimental studies (26%), and only a small proportion of the 396 bat species covered in the examined studies were studied using long-term and/or experimental approaches (11%), even though they are more informative about the effects of climate change. We emphasise the need for more empirical studies to unravel the multifaceted nature of bats' responses to climate change and the need for standardised study designs that will enable synthesis and meta-analysis of the literature. Finally, we stress the importance of overcoming geographic and taxonomic disparities through strengthening research capacity in the Global South to provide a more comprehensive view of terrestrial biodiversity responses to climate change.Natural Environment Research Council (NERC)MUR Rita Levi Montalcini programPortuguese Foundation for Science and TechnologySpanish Ministry of Science, Innovation and UniversitiesJunta de AndalucíaBulgarian National Science FundKaroll Knowledge Foundatio

Listening carefully: increased perceptual acuity for species discrimination in multispecies signalling assemblages

Communication is a fundamental component of evolutionary change because of its role in mate choice and sexual selection. Acoustic signals are a vital element of animal communication and sympatric species may use private frequency bands to facilitate intraspecific communication and identification of conspecifics (acoustic communication hypothesis, ACH). If so, animals should show increasing rates of misclassification with increasing overlap in frequency between their own calls and those used by sympatric heterospecifics. We tested this on the echolocation of the horseshoe bat, Rhinolophus capensis, using a classical habituation-dishabituation experiment in which we exposed R. capensis from two phonetic populations to echolocation calls of sympatric and allopatric horseshoe bat species (Rhinolophus clivosus and Rhinolophus damarensis) and different phonetic populations of R. capensis. As predicted by the ACH, R. capensis from both test populations were able to discriminate between their own calls and calls of the respective sympatric horseshoe bat species. However, only bats from one test population were able to discriminate between calls of allopatric heterospecifics and their own population when both were using the same frequency. The local acoustic signalling assemblages (ensemble of signals from sympatric conspecifics and heterospecifics) of the two populations differed in complexity as a result of contact with other phonetic populations and sympatric heterospecifics. We therefore propose that a hierarchy of discrimination ability has evolved within the same species. Frequency alone may be sufficient to assess species membership in relatively simple acoustic assemblages but the ability to use additional acoustic cues may have evolved in more complex acoustic assemblages to circumvent misidentifications as a result of the use of overlapping signals. When the acoustic signal design is under strong constraints as a result of dual functions and the available acoustic space is limited because of co-occurring species, species discrimination is mediated through improved sensory acuity in the receiver

Hibernation does not affect memory retention in bats

Long-term memory can be critically important for animals in a variety of contexts, and yet the extreme reduction in body temperature in hibernating animals alters neurochemistry and may therefore impair brain function. Behavioural studies on memory impairment associated with hibernation have been almost exclusively conducted on ground squirrels (Rodentia) and provide conflicting results, including clear evidence for memory loss. Here, we for the first time tested memory retention after hibernation for a vertebrate outside rodents—bats (Chiroptera). In the light of the high mobility, ecology and long life of bats, we hypothesized that maintenance of consolidated memory through hibernation is under strong natural selection. We trained bats to find food in one out of three maze arms. After training, the pre-hibernation performance of all individuals was at 100 per cent correct decisions. After this pre-test, one group of bats was kept, with two interruptions, at 7°C for two months, while the other group was kept under conditions that prevented them from going into hibernation. The hibernated bats performed at the same high level as before hibernation and as the non-hibernated controls. Our data suggest that bats benefit from an as yet unknown neuroprotective mechanism to prevent memory loss in the cold brain