Biology subjects

Denlinger, D. L.

Publications and source records attributed to Denlinger, D. L..

5 recordsLinked to original sources

bioRxiv2023

Reduced male fertility of an Antarctic mite following extreme heat stress could prompt localized population declines

Climate change is leading to substantial global thermal changes, which are particularly pronounced in polar regions. Few studies have examined the impact of heat stress on reproduction in Antarctic terrestrial arthropods, specifically how brief, extreme events may alter survival. We observed that sublethal heat stress reduces male fecundity in an Antarctic mite, yielding females that produced fewer viable eggs. Females and males collected from microhabitats with high temperatures showed a similar reduction in fertility. This impact is temporary, as indicated by recovery of male fecundity following return to cooler, stable conditions. The diminished fecundity is likely due to a drastic reduction in the expression of male-associated factors that occur in tandem with a substantial increase in the expression of heat shock proteins. Cross mating between mites from different sites confirmed that heat-exposed populations have impaired male fertility. However, the impact on fertility declines with time when the mites are allowed to recover under less stressful conditions, suggesting that the negative effects are transient. Modeling indicated that heat stress is likely to reduce population growth and that short bouts of non-lethal heat stress could have substantial effects on local populations of Antarctic arthropods.

physiology↗

bioRxiv2021

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

Rapid hardening is a process that quickly improves an animals 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.

physiology↗

bioRxiv2020

Brief exposure to a diverse range of environmental stress enhances stress tolerance in the polyextremophilic Antarctic midge, Belgica antarctica

Insects use rapid acclimation to enhance their tolerance of abiotic stresses within minutes to hours. These responses are critical adaptations for insects and other small ectotherms to tolerate drastic changes in temperature, hydration, or other factors that can fluctuate precipitously with ambient conditions or as a result of behavior. Rapid cold-hardening, where insects use brief exposure to modest chilling as a cue to enhance their cold tolerance, is the most thoroughly-studied of these responses and relatively little is known about rapid acclimation that is either triggered by or enhances tolerance of other abiotic stresses. Here, we used larvae of the Antarctic midge, Belgica antarctica, a polar extremophile that routinely experiences numerous stresses in nature, to investigate how 2 h exposure to modest environmental stresses affect stress tolerance in insects. Brief pretreatment by various stresses, including hyperosmotic challenge, hypoosmotic challenge, acidity, basicity, and UV irradiation enhanced stress tolerance in B. antarctica larvae relative to untreated controls. These results indicate that numerous environmental cues can trigger rapid acclimation in insects and that these responses can enhance tolerance of multiple stresses.

physiology↗

bioRxiv2019

Multi-level analysis of reproduction in an Antarctic midge identifies female and male accessory gland products that are altered by larval stress and impact progeny viability

The Antarctic midge, Belgica antarctica, is a wingless, non-biting midge endemic to Antarctica. Larval development requires at least two years, but adult life lasts only two weeks. The nonfeeding adults mate in swarms and females die shortly after oviposition. Eggs are suspended in a gel of unknown composition that is expressed from the female accessory gland. This project characterizes molecular mechanisms underlying reproduction in this midge by examining differential gene expression in whole males, females, and larvae, as well as in male and female accessory glands. Functional studies were used to assess the role of the gel encasing the eggs, as well as the impact of stress on reproductive biology. RNA-seq analyses revealed sex- and development-specific gene sets along with those associated with the accessory glands. Proteomic analyses were used to define the composition of the egg-containing gel, which is generated during multiple developmental stages and derived from both the accessory gland and other female organs. Functional studies indicate the gel provides a larval food source and thermal and dehydration buffer, all of which are critical for viability. Larval dehydration stress directly reduces production of storage proteins and key accessory gland components, a feature that impacts adult reproductive success. Modeling reveals that bouts of dehydration may significantly impact population growth. This work lays a foundation for further examination of reproduction in midges and provides new information related to general reproduction in dipterans. A key aspect is that reproduction and stress dynamics, currently understudied in polar organisms, are likely to prove critical for determining how climate change will alter survivability.

genomics↗

bioRxiv2019

Leveraging targeted sequencing for non-model species: a step-by-step guide to obtain a reduced SNP set and a pipeline to automate data processing in the Antarctic Midge, Belgica antarctica.

The sequencing of whole or partial (e.g. reduced representation) genomes are commonly employed in molecular ecology and conservation genetics studies. However, due to sequencing costs, a trade-off between the number of samples and genome coverage can hinder research for non-model organisms. Furthermore, the processing of raw sequences requires familiarity with coding and bioinformatic tools that are not always available. Here, we present a guide for isolating a set of short, SNP-containing genomic regions for use with targeted amplicon sequencing protocols. We also present a python pipeline--PypeAmplicon-- that facilitates processing of reads to individual genotypes. We demonstrate the applicability of our method by generating an informative set of amplicons for genotyping of the Antarctic midge, Belgica antarctica, an endemic dipteran species of the Antarctic Peninsula. Our pipeline analyzed raw sequences produced by a combination of high-multiplexed PCR and next-generation sequencing. A total of 38 out of 47 (81%) amplicons designed by our panel were recovered, allowing successful genotyping of 42 out of 55 (76%) targeted SNPs. The sequencing of [~]150 bp around the targeted SNPs also uncovered 80 new SNPs, which complemented our analyses. By comparing overall patterns of genetic diversity and population structure of amplicon data with the low-coverage, whole-genome re-sequencing (lcWGR) data used to isolate the informative amplicons, we were able to demonstrate that amplicon sequencing produces information and results similar to that of lcWGR. Our methods will benefit other research programs where rapid development of population genetic data is needed but yet prevented due to high expense and a lack of bioinformatic experience.

evolutionary biology↗