EEOB Publications March 1 - March 31

March 24, 2021

EEOB Publications March 1 - March 31

Image
EEOB graphic
Description

Rapid stress hardening in the Antarctic midge improves male fertility by increasing courtship success and preventing the decline of accessory gland proteins following cold exposure

Oluwaseun M. Ajayi, J. D. Gantz, Geoffrey Finch, Richard E. Lee Jr., David L. Denlinger, Joshua B. Benoit. 2021. doi: https://doi.org/10.1101/2021.02.27.432016

Abstract

Rapid hardening is a process that quickly improves an animal’s performance following exposure to a potentially damaging stress. Features of reproduction can be improved by rapid hardening, but little is known about how rapid hardening may contribute to physiological responses in the cold environment of Antarctica. In this study of the Antarctic midge, Belgica antarctica (Diptera, Chironomidae), we examine how rapid hardening in response to dehydration (RDH) or cold (RCH) improves male pre- and post-copulatory function related to fertility when the insects are subsequently subjected to a damaging cold exposure. Neither RDH nor RCH improved survival in response to lethal cold stress, but male activity following sublethal cold exposure was enhanced. Both RCH and RDH improved mating success of males compared to those subjected directly to a sublethal bout of cold. Egg viability decreased following direct exposure to sublethal cold, but improved following RCH and RDH. Sublethal cold exposure reduced expression of four accessory gland proteins, while expression remained high in males exposed to RCH. Though rapid hardening may be cryptic in males, this study shows that it can be revealed by pre- and post-copulatory interactions with females.


DNA methylation predicts age and provides insight into exceptional longevity of bats

Gerald S. Wilkinson, Danielle M. Adams, Amin Haghani, Ake T. Lu, Joseph Zoller, Charles E. Breeze, Bryan D. Arnold, Hope C. Ball, Gerald G. Carter, Lisa Noelle Cooper, Dina K. N. Dechmann, Paolo Devanna, Nicolas J. Fasel, Alexander V. Galazyuk, Linus Günther, Edward Hurme, Gareth Jones, Mirjam Knörnschild, Ella Z. Lattenkamp, Caesar Z. Li, Frieder Mayer, Josephine A. Reinhardt, Rodrigo A. Medellin, Martina Nagy, Brian Pope, Megan L. Power, Roger D. Ransome, Emma C. Teeling, Sonja C. Vernes, Daniel Zamora-Mejías, Joshua Zhang, Paul A. Faure, Lucas J. Greville & Steve Horvath. Nat Commun 12, 1615 (2021). https://doi.org/10.1038/s41467-021-21900-2

Abstract

Exceptionally long-lived species, including many bats, rarely show overt signs of aging, making it difficult to determine why species differ in lifespan. Here, we use DNA methylation (DNAm) profiles from 712 known-age bats, representing 26 species, to identify epigenetic changes associated with age and longevity. We demonstrate that DNAm accurately predicts chronological age. Across species, longevity is negatively associated with the rate of DNAm change at age-associated sites. Furthermore, analysis of several bat genomes reveals that hypermethylated age- and longevity-associated sites are disproportionately located in promoter regions of key transcription factors (TF) and enriched for histone and chromatin features associated with transcriptional regulation. Predicted TF binding site motifs and enrichment analyses indicate that age-related methylation change is influenced by developmental processes, while longevity-related DNAm change is associated with innate immunity or tumorigenesis genes, suggesting that bat longevity results from augmented immune response and cancer suppression.


Changes to the spermatozoa glycocalyx and its role in fertilization in Sauger (Sander canadensis)

Bryan Blawut, Barbara Wolfe, Christa R. Moraes, Christopher Premanandan, Stuart A. Ludsin, Gustavo Schuenemann, Marco A. Coutinho da Silva. Aquaculture, Volume 539, 2021, 736635, ISSN 0044-8486, https://doi.org/10.1016/j.aquaculture.2021.736635.

Abstract

The spermatozoa glycocalyx is a dynamic coating of extracellular glycoproteins known to facilitate the acrosome reaction and fertilization in mammals. Most fish sperm, however, contain no acrosome and are subjected to different stimuli (e.g., osmotic shock in the external environment) prior to fertilization. At present, our understanding of the composition and spatial distribution of sugar moieties and the functional role of the glycocalyx in fish sperm remains incomplete. Moreover, the influence of assisted reproduction techniques (e.g., testicular harvest and cryopreservation) commonly used in aquaculture settings on this structure in fish sperm is unknown. Herein, we describe and compare the composition and characteristics of the glycocalyx among sperm types (stripped, testicular, and cryopreserved) and between activation statuses (inactive vs. activated) using sauger (Sander canadensis) as a model. We also investigated the importance of certain moieties (e.g., N-acetyl-glucosamine [GlcNAc]) to fertilization. Staining distributions, fluorescent intensity, and proportion of cells exhibiting high fluorescence were measured for each treatment using fluorescent microscopy and flow cytometry, respectively. Three lectins, specific to certain glycocalyx sugar moieties (wheat germ agglutinin, WGA [GlcNAc]; concanavalin A, ConA [α-mannose]; and peanut agglutinin, PNA [β-galactose]) were used to monitor these variables in fish sperm. The sauger glycocalyx contained GlcNAc and α-mannose but lacked β-galactose moieties. Testicular sperm exhibited fewer cells (20–40% fewer) with high GlcNAc and α-mannose content than other sperm types. Additionally, the proportion of highly fluorescent cells in testicular sperm were positively correlated with motility (r = 0.80–0.95), suggesting the glycocalyx is affected by post-testicular maturation. Motility activation via hypo-osmotic shock caused a redistribution of GlcNAc to the apical region of the head of 40–50% of stripped and testicular sperm, respectively. Cryopreserved sperm showed significantly reduced apical staining following activation (< 5%) and a 2 to 3-fold increase in α-mannose availability. Further, fertilization was reduced by ~80% compared to a fresh control (i.e., untreated stripped sperm) in both stripped sperm pre-treated block GlcNAc during insemination and cryopreserved sperm. These results indicate that the glycocalyx of sauger sperm is dynamic, as it is modified during post-testicular maturation, motility activation, and that it plays a pivotal role in fertilization. Cryopreservation largely negated these changes, which may partially explain the reduced fertility observed in frozen sperm. Ultimately, our analyses show that the use of lectins (e.g., GA and ConA) as biomarkers for the glycocalyx can help to understand the quality and fertilization potential of fish sperm.


Gizzard Shad Target Strength‐to‐Body Size Equations at Multiple Hydroacoustic Frequencies

Garret R. Johnson, Rebecca A. Dillon, Richard D. Zweifel, Stuart A. Ludsin, Joseph D. Conroy. 2021. https://doi.org/10.1002/tafs.10287

Abstract

Species‐specific target strength (TS)‐to‐length (L) and TS‐to‐weight (W) equations can reduce bias in biomass estimates from hydroacoustic surveys, yet these equations do not exist for most fishes. Equations specific to the Gizzard Shad Dorosoma cepedianum, a wide‐ranging and often highly abundant prey fish in North American reservoirs and rivers, do not exist. Herein, we sought to develop TS–L and TS–W equations for Gizzard Shad by insonifying free‐swimming individuals of known sizes (36–209 mm TL) in a net cage at three transducer frequencies (70, 120, and 200 kHz). We derived TS–size relationships using major‐axis regression (MAR) and least‐squares regression (LSR), comparing our resultant TS–L equations to a commonly used multispecies equation (Love 1971). To determine how our Gizzard Shad‐specific equations affected estimates of prey fish biomass, we conducted mobile hydroacoustic surveys in four small, shallow Midwestern reservoirs and then estimated biomass using each equation. In general, for TS–L equations, MAR produced the highest estimates of biomass, followed by LSR and then the multispecies equation. Similarly, the TS–W equation derived using MAR produced greater biomass estimates than the equation using LSR. Our findings highlight the value of using species‐specific TS–size equations over multispecies equations in ecosystems dominated by a single fish species (e.g., Gizzard Shad in Midwestern reservoirs). They also demonstrate the value of using MAR to develop TS–size equations, owing to its ability to account for fish size measurement error. The use of species‐specific TS–size equations and MAR should lead to robust estimates of biomass in single‐species‐dominated ecosystems, thus benefiting fisheries assessment and decision making.


Pitfalls of ignoring trait resolution when drawing conclusions about ecological processes

Brooks A. Kohli  Marta A. Jarzyna. 2021. https://doi.org/10.1111/geb.13275

Abstract

Aim

Understanding how ecological communities are assembled remains a grand challenge in ecology with direct implications for charting the future of biodiversity. Trait‐based methods have emerged as the leading approach for quantifying functional community structure (convergence, divergence) but their potential for inferring assembly processes rests on accurately measuring functional dissimilarity among community members. Here, we argue that trait resolution (from finest‐resolution continuous measurements to coarsest‐resolution binary categories) remains a critically overlooked methodological variable, even though categorical classification is known to mask functional variability and inflate functional redundancy among species or individuals.

Innovation

We present the first detailed predictions of trait resolution biases and demonstrate, with simulations, how the distortion of signal strength by increasingly coarse‐resolution traits can fundamentally alter functional structure patterns and the interpretation of causative ecological processes (e.g. abiotic filters, biotic interactions). We show that coarser trait data impart different impacts on the signals of divergence and convergence, implying that the role of biotic interactions may be underestimated when using coarser traits. Furthermore, in some systems, coarser traits may overestimate the strength of trait convergence, leading to erroneous support for abiotic processes as the primary drivers of community assembly or change.

Main conclusions

Inferences of assembly processes must account for trait resolution to ensure robust conclusions, especially for broad‐scale studies of comparative community assembly and biodiversity change. Despite recent improvements in the collection and availability of trait data, great disparities continue to exist among taxa in the number and availability of continuous traits, which are more difficult to acquire for large numbers of species than coarse categorical assignments. Based on our simulations, we urge the consideration of trait resolution in the design and interpretation of community assembly studies and suggest a suite of practical solutions to address the pitfalls of trait resolution biases.


Nanotechnology-Based Detection and Remediation of Mycotoxins for Food and Agriculture Applications

Manubolu M., Goodla L., Ludsin S.A., Jayakumar T., Fraker M., Pathakoti K. 2021. In: Kumar V., Guleria P., Ranjan S., Dasgupta N., Lichtfouse E. (eds) Nanosensors for Environment, Food and Agriculture Vol. 1. Environmental Chemistry for a Sustainable World, vol 60. Springer, Cham. https://doi.org/10.1007/978-3-030-63245-8_9

Abstract

Mycotoxins are highly toxic secondary metabolites produced by fungi, which may contaminate a large variety of food and feed commodities. Among them, the aflatoxins, deoxynivalenol, zearalenone, fumonisins, and ochratoxins are the most common contaminants posing a serious threat to human and animal health.Given that traditional mycotoxin detection methods have been shown to be laborious and time consuming, interest in developing reliable and rapid mycotoxin detection methods has increased during recent decades. Herein, we review emerging nanotechnology-based methods, including gold nanoparticles, magnetic nanoparticles, and quantum dot-based sensors, which have been developed to reliably and efficiently detecting mycotoxins in food and feed commodities. We also summarize recent technologies used to remove mycotoxins via adsorption and photocatalytic degradation. As our review illustrates, the emerging use of nanotechnology offers a reliable and cost-effective means to prevent mycotoxin contamination in food and feed commodities, which could reduce health risks to consumers.