Biology subjects

Barrett, M.

Publications and source records attributed to Barrett, M..

26 records · Page 2Linked to original sources

bioRxiv2022

Individual reflectance of solar radiation as a thermoregulatory adaptation to microclimate: A test in dimorphic male bees (Centris pallida)

Incoming solar radiation (wavelengths 290 - 2500 nm) significantly affects an organisms thermal balance via radiative heat gain. Species adapted to different environments can differ in solar reflectance profiles. We hypothesized that conspecific individuals using thermally distinct microhabitats to engage in fitness-relevant behaviors would show intraspecific differences in reflectance: we predicted individuals that use hot microclimates (where radiative heat gain represents a greater thermoregulatory challenge) would be more reflective across the entire solar spectrum than those using cooler microclimates. Differences in near-infrared (NIR) reflectance (700 - 2500 nm) are strongly indicative of thermoregulatory adaptation as, unlike differences in visible reflectance (400 - 700 nm), they are not perceived by ecological or social partners. We tested these predictions in male Centris pallida (Hymenoptera: Apidae) bees from the Sonoran Desert. Male C. pallida use alternative reproductive tactics that are associated with distinct microclimates: Large-morph males, with paler visible coloration, behave in an extremely hot microclimate close to the ground, while small-morph males, with a dark brown dorsal coloration, frequently use cooler microclimates above the ground near vegetation. We found that large-morph males had higher reflectance of solar radiation (UV through NIR) resulting in lower solar absorption coefficients. This thermoregulatory adaptation was specific to the dorsal surface, and produced by differences in hair, not cuticle, characteristics. Our results showed that intraspecific variation in behavior, particular in relation to microclimate use, can generate unique thermal adaptations that changes the reflectance of shortwave radiation among individuals within the same population.

ecology↗

bioRxiv2022

Don't get a big head: Centris pallida (Hymenoptera: Apidae) male head widths decrease across five decades

Historical data suggest that many bee species have declined in body size. Larger-bodied bees with narrow phenological and dietary breadth are most prone to declines in body size over time. This may be especially true in solitary, desert-adapted species that are vulnerable to climate change - such as Centris pallida (Hymenoptera: Apidae). In addition, body size changes in species with size-linked behaviors could threaten the prevalence of certain behavioral phenotypes long-term. C. pallida solitary bees are found in the Sonoran Desert. Males use alternative reproductive tactics (ARTs) and are dimorphic in both morphology and behavior. C. pallida male body size has been studied since the 1970s in the same population. We collected body size data in 2022 and combined it with published records from 1974-2022. We find a persistent decline in the mean head width of patrolling males, and shifts towards smaller body sizes in the populations of males found foraging and hovering. Both morphs declined in average body size, and the proportion of large-morph males in the population decreased by 8%. Mating males did not decline in mean body size over the last five decades. We discuss hypotheses related to the decline in C. pallida male head width. Finally, we advocate for C. pallida as an excellent study system for understanding the stability of ARTs with size-linked behavioral phenotypes.

ecology↗

bioRxiv2022

Impacts of development and adult sex on brain cell numbers in the Black Soldier Fly, Hermetia illucens L. (Diptera: Stratiomyidae)

The Black Soldier Fly (Hermetia illucens, Diptera: Stratiomyidae) has been introduced across the globe, with numerous industry applications predicated on its tremendous growth during the larval stage. However, basic research on H. illucens biology (for example, studies of their central nervous system) are lacking. Despite their small brain volumes, insects are capable of complex behaviors; understanding how these behaviors are completed with such a small amount of neural tissue requires understanding processing power (e.g. number of cells) within the brain. Brain cell counts have been completed in only a few insect species (mostly Hymenoptera), and almost exclusively in adults. This limits the taxonomic breadth of comparative analyses, as well as any conclusions about how development and body size growth may impact brain cell populations. Here, we present the first images and cell counts of the H. illucens brain at four time points across development (early, mid, and late larval stages, and both male and female adults) using immunohistochemistry and isotropic fractionation. To assess sexual dimorphism in adults, we quantified the number of cells in the central brain vs. optic lobes of males and females separately. To assess if increases in body size during development might independently affect different regions of the CNS, we quantified the larval ventral nerve cord and central brain separately at all three stages. Together, these data provide the first description of the nervous system of a popular, farmed invertebrate and the first study of brain cell numbers using IF across developmental stages in any insect.

neuroscience↗

bioRxiv2021

A lineage-specific Exo70 is required for receptor kinase-mediated immunity in barley

In the evolution of land plants, the plant immune system has experienced expansion in immune receptor and signaling pathways. Lineage-specific expansions have been observed in diverse gene families that are potentially involved in immunity, but lack causal association. Here, we show that Rps8-mediated resistance in barley to the fungal pathogen Puccinia striiformis f. sp. tritici (wheat stripe rust) is conferred by a genetic module: LRR-RK and Exo70FX12, which are together necessary and sufficient. The Rps8 LRR-RK is the ortholog of rice extracellular immune receptor Xa21 and Exo70FX12 is a member of the Poales-specific Exo70FX clade. The Exo70FX clade emerged after the divergence of the Bromeliaceae and Poaceae, and comprises from 2 to 75 members in sequenced grasses. These results demonstrate the requirement of a lineage-specific Exo70FX12 in Rps8 LRR-RK immunity and suggest that the Exo70FX clade may have evolved a specialized role in receptor kinase signaling.

plant biology↗

bioRxiv2021

Transcriptional shift and metabolic adaptations during Leishmania quiescence using stationary-phase and drug pressure as models

Microorganisms can adopt a quiescent physiological condition which acts as a survival strategy under unfavourable conditions. Quiescent cells are characterized by slow or non-proliferation and deep down-regulation of processes related to biosynthesis. Although quiescence has been described mostly in bacteria, this survival skill is widespread, including in eukaryotic microorganisms. In Leishmania, a digenetic parasitic protozoan that causes a major infectious disease, quiescence has been demonstrated, but molecular and metabolic features enabling its maintenance are unknown. Here we quantified the transcriptome and metabolome of Leishmania promastigotes and amastigotes where quiescence was induced in vitro either through drug pressure or by stationary phase. Quiescent cells have a global and coordinated reduction in overall transcription, with levels dropping to as low as 0.4% of those in proliferating cells. However, a subset of transcripts did not follow this trend and were relatively upregulated in quiescent populations, including those encoding membrane components such as amastins and GP63 or processes like autophagy. The metabolome followed a similar trend of overall downregulation albeit to a lesser magnitude than the transcriptome. Noteworthy, among the commonly upregulated metabolites were those involved in carbon sources as an alternative to glucose. This first integrated two omics layers affords novel insights into cell regulation and shows commonly modulated features across stimuli and stages.

bioinformatics↗

bioRxiv2021

Soldier neural architecture is temporarily modality-specialized but poorly predicted by repertoire size in the stingless bee Tetragonisca angustula

Individual heterogeneity within societies provides opportunities to test hypotheses about adaptive neural investment in the context of group cooperation. Here we explore neural investment in defense specialist soldiers of the eusocial stingless bee (Tetragonisca angustula) which are age sub-specialized on distinct defense tasks, and have an overall higher lifetime task repertoire than other sterile workers within the colony. Consistent with predicted behavioral demands, soldiers had higher relative visual (optic lobe) investment than non-soldiers but only during the period when they were performing the most visually demanding defense task (hovering guarding). As soldiers aged into the less visually demanding task of standing guarding this difference disappeared. Neural investment was otherwise similar across all colony members. Despite having larger task repertoires, soldiers had similar absolute brain size and smaller relative brain size compared to other workers, meaning that lifetime task repertoire size was a poor predictor of brain size. Together, our results are consistent with the specialized but flexible defense strategies of this species, broadening our understanding of how neurobiology mediates age and morphological task specialization in highly cooperative societies.

neuroscience↗

bioRxiv2019

Larval mannitol diets increase mortality, prolong development, and decrease adult body sizes in fruit flies (Drosophila melanogaster).

Ingestion of the polyol mannitol caused sex-biased mortality in adult Drosophila melanogaster, but larval mortality was not sex-biased. High-sugar diets prolong development and generate smaller adult body sizes in D. melanogaster. We hypothesized that mannitol ingestion would generate similar developmental phenotypes as other high-carbohydrate diets. We predicted concentration-dependent effects on development similar to high-sugar diets when D. melanogaster larvae are fed mannitol, as well as a concentration-dependent amelioration of developmental effects if introduction to mannitol media is delayed past the third instar. Both male and female larvae had prolonged development and smaller adult body sizes when fed increasing concentrations of mannitol. Mannitol-induced increases in mortality were concentration dependent in 0 M to 0.8 M treatments beginning as early as 48 hours post-hatching. Larval survival, and pupation and eclosion times, were normal in 0.4 M mannitol treatments when larvae were first introduced to mannitol 72 hours post-hatching (the beginning of the third-instar); the adverse mannitol effects occurred in 0.8 M mannitol treatments, but at a lower magnitude. Female D. melanogaster adults prefer laying eggs on diets with high sugar concentrations, despite the negative effects on offspring performance. However, when given a choice, female D. melanogaster avoided laying eggs on mannitol-containing media that was otherwise identical to the control media, suggesting females perceived and avoided mannitol. In conclusion, the developmental effects of a larval mannitol diet closely resemble those of high-sugar diets, but adult female oviposition responses to mannitol in laying substrates are distinct from responses to other carbohydrates.

zoology↗

bioRxiv2019

Mannitol ingestion causes concentration-dependent, sex-specific mortality in adults of the fruit fly (Drosophila melanogaster).

Mannitol, a sugar alcohol used in commercial food products, induced sex-specific mortality in the fruit fly Drosophila melanogaster when ingested at a single concentration (1M), and female mortality was greater than male mortality. We hypothesized that sex differences in energy needs, related to reproductive costs, contribute to increased mortality in females compared to males. To test for the effects of reproductive costs, we compared longevity to 21 days of actively mating and non-mating flies fed various concentrations of mannitol. We also asked whether mannitol-induced mortality was concentration-dependent for both males and females, and if mannitols sex-specific effects were consistent across concentrations. Females and males both showed concentration-dependent increases in mortality, but female mortality was consistently higher at all concentrations above 0.75M. Fly longevity to 21 days decreased further for both sexes when housed in mixed sex vials (as compared to single sex vials), suggesting the increased energetic demands of reproduction for both sexes may increase ingestion of mannitol. Mannitol fed to larvae did not alter emerging adult sex ratios, suggesting that sex-specific mortality due to mannitol occurs only in adults.

zoology↗