Biology subjects

Aichelman, H. E.

Publications and source records attributed to Aichelman, H. E..

10 recordsLinked to original sources

bioRxiv2026

Diel thermal variability does little to mitigate bleaching in two endangered coral holobionts

Research has shown that tropical corals inhabiting warmer, more thermally variable reef environments often exhibit reduced bleaching. However, the influence of diel thermal variation (DTV) is rarely tested experimentally independent of changes in mean temperature, and few studies have explored responses of coral hosts together with their associated microbial consortia (Symbiodiniaceae algae and bacteria). Here, using a common garden approach with two species of endangered reef-building corals (Orbicella franksi & O. faveolata), we show that 90 days of DTV priming (26{degrees}C {+/-} 2.4{degrees}C day-1) elicited little physiological or gene expression plasticity and did not alter Symbiodiniaceae or bacterial compositions relative to corals under stable conditions (26{degrees}C). Critically, when these corals experienced a subsequent heat challenge (32{degrees}C for 15 days), both species exhibited broad physiological and gene expression responses regardless of DTV priming. A systems biology approach linking gene expression with experimental treatments and traits supports the presence of both 1) convergent gene modules associated with homeostasis in both host species and 2) divergent gene modules showcasing enrichment of catabolism in O. faveolata and classic protein folding functions in O. franksi under thermal challenge. Together, these data highlight that while congeneric coral species exhibit divergent gene expression responses to thermal challenges, DTV priming did not facilitate thermal stress resistance. These findings suggest that other environmental parameters that co-vary with DTV on a reef may play a more influential role in bleaching mitigation.

evolutionary biology↗

bioRxiv2024

De Novo Genome Assembly and Annotation for the Webbing Clothes Moth (Tineola bisselliella): A Globally Distributed, Economically Important Pest

Tineola bisselliella, the webbing clothes moth, is an economically important, globally distributed synanthropic pest species and member of the basal moth lineage Tineidae. Tineola bisselliella is facultatively keratinophagous. Therefore, their larvae can cause extensive damage, particularly to clothing, textiles, and museum specimens. Despite the economic and phylogenetic importance of Tineola bisselliella, there is a lack of quality genomic resources for this species, or for others within the Tineidae family. The Tineola bisselliella genome presented here consists of 30 pseudochromosomes (29 autosomes and 1 Z chromosome) produced using synteny alignment to a closely related species, Tinea pellionella. The resulting final pseudochromosome-level assembly is 243.630 Mb and has an N50 length of 8.708 Mb. The assembly is highly contiguous and has similar or improved quality compared to other available Tineidae genomes, with 93.1% of lepidopteran orthologs complete and present. Annotation of the pseudochromosome-level genome assembly with the transcriptome we produced ultimately yielded 11,267 annotated genes. Synteny alignments between the Tineola bisselliella genome assembly and other Tineidae genomes found evidence for numerous small rearrangements with high synteny conservation. In contrast, synteny alignments performed between Tineola bisselliella and the more distantly related Bombyx mori and Melitea cinxia revealed more frequent small and large rearrangements as predicted by their evolutionary divergence. The reference quality annotated genome for Tineola bisselliella presented here will advance our understanding of the evolution of the lepidopteran karyotype by providing a chromosome-level genome for this basal moth lineage and provide future insights into the mechanisms underlying keratin digestion in Tineola bisselliella. Significance StatementTineola bisselliella, the webbing clothes moth, is a globally distributed synanthropic pest species that feeds on both keratin-based materials and detritus. This dietary habit can cause substantial damage to clothing, textiles, rugs, taxidermy, and museum specimens. In fact, keratinophagous organisms cause an estimated $1 billion worth of damage annually in the United States. However, the lack of a high-quality annotated reference genome for this basal moth species has thus far limited our understanding of the mechanisms underlying keratin digestion relevant to pest control efforts and has hampered efforts to investigate the broader phylogenetic relationships the Tineidae family necessary to reveal patterns of lepidopteran chromosome evolution. Here, we present the first reference quality genome for Tineola bisselliella and the first annotated genome for any member of the Tineidae family, providing a critical resource for the lepidopteran genomics and pest management communities.

genomics↗

bioRxiv2024

Cryptic diversity shapes coral symbioses, physiology, and response to thermal challenge

Coral persistence in the Anthropocene is shaped by interactions among holobiont partners (coral animals, microbial symbionts) and their environment. Cryptic coral lineages-genetically distinct yet morphologically similar groups-are critically important as they often exhibit functional diversity relevant to thermal tolerance. Additionally, environmental parameters such as thermal variability may promote tolerance, but how variability interacts with holobiont partners to shape responses to thermal challenge remains unclear. Here, we identified three cryptic lineages of Siderastrea siderea in Bocas del Toro, Panama that differ in distributions across inshore and offshore reefs, microbial associations, holobiont phenomes, and skeleton morphologies. A thermal variability experiment failed to increase thermal tolerance, but subsequent thermal challenge and recovery revealed one lineage maintained elevated energetic reserves, photochemical efficiency, and growth. Lastly, coral cores highlighted that this lineage also exhibited faster growth historically. Functional variation among cryptic lineages highlights their importance in predicting coral reef responses to climate change. TeaserCryptic host diversity drives coral phenotypes relevant to climate change.

evolutionary biology↗

bioRxiv2024

Distinct modes of holobiont specialization among cryptic coral lineages

As ocean warming threatens reefs worldwide, identifying corals with adaptations to higher temperatures is critical for conservation. Genetically distinct but morphologically similar (i.e., cryptic) coral populations can be specialized to extreme habitats and thrive under stressful conditions. These corals often associate with locally beneficial microbiota (Symbiodiniaceae photobionts and bacteria), clouding interpretation of the drivers of thermal tolerance. Here, we leverage a holobiont (massive Porites) with high host-partner fidelity to investigate adaptive variation across classic ("typical" conditions) and extreme reefs characterized by higher temperatures and light attenuation. We uncovered three cryptic lineages that exhibit limited micro-morphological variation; one lineage dominated classic reefs (L1), one had more even distributions (L2), and a third was restricted to extreme reefs (L3). Two lineages were more closely related to populations [~]4300 km away, suggesting that these lineages are widespread. All corals harbored Cladocopium C15 photobionts, but strain-level compositions differed among lineages and reef types. L1 associated with distinct photobionts and bacteria in each reef type, whereas L2 had relatively stable associations. L3 hosted unique photobiont strains, signaling high host-photobiont fidelity. Analysis of light harvesting capacity and thermal tolerance revealed key adaptive variation underpinning survival in distinct habitats. L1 had the highest light absorption efficiency and lowest thermal tolerance, suggesting it is a classic reef specialist. L3 had the lowest light absorption efficiency and the highest thermal tolerance, showing that it is an extreme reef specialist. L2 had intermediate light absorption efficiency and thermal tolerance, signaling habitat generalism, potentially explaining how it survives well in both habitat types. These findings reveal diverging holobiont strategies to cope with extreme conditions. Resolving coral lineages is key to understanding variation in thermal tolerance among coral populations; uncovering thermally-tolerant holobionts can strengthen our understanding of coral evolution and symbiosis, and support global conservation and restoration efforts.

ecology↗

bioRxiv2023

Symbiosis modulates gene expression of symbionts, but not hosts, under thermal challenge

Increasing ocean temperatures are causing dysbiosis between coral hosts and their symbionts. Previous work suggests that coral host gene expression responds more strongly to environmental stress compared to their intracellular symbionts; however, the causes and consequences of this phenomenon remain untested. We hypothesized that symbionts are less responsive because hosts modulate symbiont environments to buffer stress. To test this hypothesis, we leveraged the facultative symbiosis between the scleractinian coral Oculina arbuscula and its symbiont Breviolum psygmophilum to characterize gene expression responses of both symbiotic partners in and ex hospite under thermal challenges. To characterize host and in hospite symbiont responses, symbiotic and aposymbiotic O. arbuscula were exposed to three treatments: 1) control (18{degrees}C), 2) heat (32{degrees}C), and 3) cold (6{degrees}C). This experiment was replicated with B. psygmophilum cultured from O. arbuscula to characterize ex hospite symbiont responses. Both thermal challenges elicited classic environmental stress responses (ESRs) in O. arbuscula regardless of symbiotic state, with hosts responding more strongly to cold challenge. Hosts also exhibited stronger responses than in hospite symbionts. In and ex hospite B. psygmophilum both downregulated genes associated with photosynthesis under thermal challenge; however, ex hospite symbionts exhibited greater gene expression plasticity and differential expression of genes associated with ESRs. Taken together, these findings suggest that O. arbuscula hosts may buffer environments of B. psygmophilum symbionts; however, we outline the future work needed to confirm this hypothesis.

molecular biology↗

bioRxiv2023

Photosymbiosis reduces the environmental stress response under a heat challenge in a facultatively symbiotic coral

The symbiosis between corals of the order Scleractinia and dinoflagellates of the family Symbiodiniaceae is sensitive to environmental stress. The oxidative bleaching hypothesis posits that extreme temperatures lead to accumulation of photobiont-derived reactive oxygen species ROS, which exacerbates the coral environmental stress response (ESR). To understand how photosymbiosis modulates coral ESRs, these responses must be explored in hosts in and out of symbiosis. We leveraged the facultatively symbiotic coral Astrangia poculata, which offers an opportunity to uncouple the ESR across its two symbiotic states (symbiotic, aposymbiotic). Colonies of both symbiotic states were exposed to three temperature treatments for 15 days: i) control (static 18{degrees}C), ii) heat challenge (increasing from 18 to 32{degrees}C), and iii) cold challenge (decreasing from 18 to 6{degrees}C) after which host gene expression was profiled. Cold challenged corals elicited widespread differential expression, however, there were no differences between symbiotic states. In contrast, symbiotic colonies exhibited greater gene expression plasticity under heat challenge, including enrichment of cell cycle pathways involved in controlling photobiont growth. Counter to the oxidative bleaching hypothesis, this plasticity did not include signatures of stress, and rather a dampened ESR under heat challenge was observed, suggesting that photobionts reduce the hosts ESR under elevated temperatures in A. poculata.

ecology↗

bioRxiv2020

Phenotypic variation in two widespread Caribbean corals, Porites astreoides and P. divaricata, between mangrove and lagoon habitats

ABSTRACTAs coral reefs experience dramatic declines in coral cover throughout the tropics, there is an urgent need to understand the role that non-reef habitats such as mangroves play in the ecological niche of corals. Mangrove habitats present a challenge to reef-dwelling corals as they can differ dramatically from adjacent reef habitats with respect to key environmental parameters such as temperature and light. As variation in temperature and light within reef habitats is known to drive intraspecific differences in coral phenotype, we hypothesized that coral species which can exploit both reef and mangrove habitats will exhibit predictable differences in phenotype between habitats. To investigate how intraspecific variation, driven by either local adaptation or phenotypic plasticity, might enable particular coral species to exploit these two qualitatively different habitat types, we compared the phenotypes of two widespread Caribbean corals — Porites divaricata and P. astreoides— in mangrove versus lagoon habitats on Turneffe Atoll, Belize. We document significant differences in colony size, color, structural complexity, and corallite morphology between habitats. In every instance, the difference between mangrove and lagoon corals was consistent in P. divaricata and P. astreoides. This study is the first to document intraspecific phenotypic diversity in corals occupying mangrove versus patch-reef habitats, and it provides a foundation for understanding why some “reef coral” species can exploit mangroves, while others cannot.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

Exposure duration modulates the response of Caribbean corals to global change stressors

Global change is threatening coral reefs, with rising temperatures leading to repeat bleaching events (dysbiosis of coral hosts and their symbiotic algae) and ocean acidification reducing net coral calcification. Although global-scale mass bleaching events are revealing fine-scale patterns of coral resistance and resilience, traits that lead to persistence under environmental stress remain elusive. Here, we conducted a 95-day controlled-laboratory experiment to investigate how duration of exposure to ocean warming (28, 31{degrees}C), acidification (pCO2 = 400-2800 atm), and their interaction influence the physiological responses of two Caribbean reef-building coral species (Siderastrea siderea, Pseudodiploria strigosa) from two reef zones of the Belize Mesoamerican Barrier Reef System. Every 30 days, calcification rate, total host protein and carbohydrate, chlorophyll a pigment concentration, and symbiont cell density were quantified for the same coral colony to characterize acclimatory responses of each genotype. Physiologies of the two species were differentially affected by these stressors, with exposure duration modulating responses. Siderastrea siderea was most affected by extreme pCO2 (~2800 atm), which resulted in reduced calcification rate, symbiont density, and chlorophyll a concentration. Siderastrea siderea calcification rate initially declined under extreme pCO2 but recovered by the final time point, and overall demonstrated resistance to next-century pCO2 and temperature stress. In contrast, P. strigosa was more negatively impacted by elevated temperature (31{degrees}C). Reductions in P. strigosa calcification rate and total carbohydrates were consistently observed over time regardless of pCO2 treatment, with the greatest reductions observed under elevated temperature. However, nearshore colonies of P. strigosa maintained calcification rates under elevated temperature throughout all exposure durations, suggesting individuals from this environment may be locally adapted to the warmer temperatures characterizing their natal reef zone. This experiment highlights how tracking individual coral colony physiology across broad exposure durations can capture acclimatory responses of corals to global change stressors.

ecology↗

bioRxiv2019

Eukaryotic plankton community stability across reef environments in Bocas del Toro Archipelago (Panama)

Variation in light and temperature can influence the genetic diversity and structure of marine plankton communities. While open ocean plankton communities receive much scientific attention, little is known about how environmental variation affects tropical coral reef plankton communities. Here, we characterize eukaryotic plankton communities on coral reefs across the Bocas del Toro Archipelago in Panama. Temperature loggers were deployed for one year and mid-day light levels were measured to quantify environmental differences across reef zones at four inner and four outer reef sites: Inner: Punta Donato, Smithsonian Tropical Research Institute (STRI) Point, Cristobal, Punta Laurel and Outer: Drago Mar, Bastimentos North, Bastimentos South, and Popa Island. Triplicate vertical plankton tows were collected mid-day and high-throughput 18S ribosomal DNA metabarcoding was leveraged to investigate the relationship between eukaryotic plankton community structure and reef zones. Plankton communities from STRI Point were additionally characterized in the morning ([~]08:00), mid-day ([~]12:00), and evening ([~]16:00) to quantify diel variation within a single site. We found that inshore reefs experienced higher average seawater temperatures, while offshore sites offered higher light levels, presumably associated with reduced water turbidity on reefs further from shore. However, these significant reef zone-specific environmental differences did not correlate with overall plankton community differences or changes in plankton genetic diversity. Instead, we found that time of day within a site and diel vertical migration played structuring roles within these plankton communities, and therefore conclude that the time of community sampling is an important consideration for future studies. Overall, plankton communities in the Bocas del Toro Archipelago appear relatively well mixed across space; however, follow-up studies focusing on more intensive sampling efforts across space and time coupled with techniques that can detect more subtle genetic differences between and within communities will more fully capture plankton dynamics in this region.

ecology↗

bioRxiv2017

Coral Symbiodinium community composition across the Belize Mesoamerican Barrier Reef System is driven by host species and environmental variability

Reef-building corals maintain a symbiotic relationship with dinoflagellate algae of the genus Symbiodinium and this symbiosis is vital for the survival of the coral holobiont. Symbiodinium community composition within the coral host has been shown to influence a corals ability to resist and recover from stress. A multitude of stressors including ocean warming, ocean acidification, and eutrophication have been linked to global scale decline in coral health and cover in recent decades. Three distinct thermal regimes (highTP, modTP, and lowTP) following an inshore-offshore gradient of declining average temperatures and thermal variation were identified on the Belize Mesoamerican Barrier Reef System (MBRS). Quantitative metabarcoding of the ITS-2 locus was employed to investigate differences and similarities in Symbiodinium genetic diversity of the Caribbean corals Siderastrea siderea, S. radians, and Pseudodiploria strigosa between the three thermal regimes. A total of ten Symbiodinium lineages were identified across the three coral host species. Siderastrea siderea associated with distinct Symbiodinium communities, however Symbiodinium communities of its congener, S. radians, and P. strigosa, were more similar to one another. Thermal regime played a role in defining Symbiodinium communities in S. siderea but not S. radians or P. strigosa. Against expectations, Symbiodinium trenchii, a symbiont known to confer thermal tolerance, was dominant only in S. siderea at one sampled offshore site and was rare inshore, suggesting that coral thermal tolerance in more thermally variable inshore habitats is achieved through alternative mechanisms. Overall, thermal parameters alone were likely not the only primary drivers of Symbiodinium community composition, suggesting that environmental variables unrelated to temperature (i.e., light availability, or nutrients) may play key roles in structuring coral-algal communities in Belize and that the relative importance of these environmental variables may vary by coral host species.

molecular biology↗