Biology subjects

Hensley, N. M.

Publications and source records attributed to Hensley, N. M..

8 recordsLinked to original sources

bioRxiv2026

Diel metabolic variation and the energetic demands of courtship in bioluminescent Photeros ostracods

The energetic demands of courtship are central to sexual selection, but their magnitude and temporal variation remain poorly quantified in many signalling systems. We used closed-chamber respirometry and low-light video analysis to estimate courtship-associated metabolic rates in males of the bioluminescent ostracod Photeros sp. "EGD." Low-activity metabolic rate varied strongly across the diel cycle: in small vessels that constrained movement, individually measured males consumed significantly more oxygen at night than during the day. We then compared oxygen consumption across vessels that differed in opportunities for movement and courtship. Metabolic rates were highest in large vessels that permitted bioluminescent courtship displays, intermediate in medium vessels that allowed swimming but not full displays, and lowest in small vessels that constrained movement. Oxygen consumption in large vessels at night was approximately 500% of small-vessel daytime rates, 280% of small-vessel nighttime rates, and 160% of medium-vessel nighttime rates. Because measurements integrated oxygen use over multi-hour intervals, these values represent time-averaged metabolic demand rather than instantaneous costs of individual light pulses or display trains. Video analyses suggested a positive association between signalling rate and oxygen consumption, although this relationship was not statistically supported in our large-vessel dataset, which had low statistical power. Together, these results show that male Photeros undergo strong diel shifts in metabolic state and that the whole-animal performance required to construct bioluminescent courtship displays may often impose substantial energetic demands. Summary statementMale sea fireflies show higher nighttime metabolic rates and increased oxygen consumption during courtship-associated activities, highlighting the physiological demands of producing complex bioluminescent displays.

physiology↗

bioRxiv2026

Aposematic signals are dynamic over time in bioluminescent ostracods

Aposematic signals convey information about prey unpalatability to potential predators. Such signals are defined as advertisements, with prey usually signalling unpalatability before an attack. Overlooked, however, is whether signals presented after an attack can function as aposematic warnings and influence the efficacy of defense. Here, we test if post-attack signals can be aposematic by observing fish predators responding to prey (Ostracoda, Cypridinidae) that produce bioluminescence following an attack. By manipulating potential chemical defenses of prey, and by comparing feeding responses to both bioluminescent and nonluminescent prey, we provide multiple lines of evidence to show bioluminescent prey are unpalatable and use post-attack bioluminescence as an aposematic signal. First, live, bioluminescent prey secrete bioluminescence only after being attacked. Second, predatory fishes rarely consumed bioluminescent prey, especially compared to nonluminescent alternatives. Third, because fishes readily ate bioluminescent prey that had been treated (frozen or boiled), which should remove defenses, bioluminescent species likely possess some unidentified defense over nonluminescent relatives. Finally, over the course of four experimental trials, predators were less likely to consume bioluminescent prey as their cumulative exposure to bioluminescent displays increased, indicative of learning. Post-attack aposematic signals, like bioluminescence, may be as common and effective a defensive strategy as pre-attack signals.

animal behavior and cognition↗

bioRxiv2026

Revised genomic resources for the swordtail cricket, Laupala kohalensis Otte 1994

Advances in genetic tools such as next and third generation sequencing, paired with a focus on representative clades, provide insight into how processes including adaptation, admixture, and genome structure shape the evolution and maintenance of species. However, our understanding of the genomics of speciation is dominated by systems where ecological adaptations are thought to cause initial barriers to gene exchange. In contrast to other model systems, the 38 species of the genus Laupala constitute a very rapid radiation, where evolution of reproductive barriers and speciation is thought to be driven by sexual selection. Here, with novel PacBio HiFi reads and RNA- and Iso-Seq data, we provide a highly contiguous, chromosome-level genome and markedly improved annotation of the endemic Hawaiian cricket, Laupala kohalensis Otte, 1994. Our new resources advance previous efforts, placing 99% of 47 scaffolds on 7 autosomes and 1 sex chromosome in the 1.67 Gb assembly, with a 98.8% BUSCO score (insecta_db10), N50 of [~]268 Mb, and L50 of 3. Using a custom repeat library, we estimate the genome to have 46.09% repeat content, and the new annotation includes an increased estimate of 17,670 genes, which coincides with that known from other Orthopterans. Notably, we find a large nuclear DNA segment of mitochondrial origin on chromosome 7. This new resource provides a powerful tool to identify and compare genomic causes of phenotypic diversification in a system characterized by strong signatures of sexual differentiation, representing an underappreciated but potentially widespread cause of speciation.

genomics↗

bioRxiv2025

Sexual isolation maintains species boundaries between Hawaiian crickets in sympatry despite weak habitat isolation

Understanding the relative importance of different reproductive isolating barriers in maintaining species boundaries is fundamental to understanding how closely related species coexist without hybridizing. Habitat isolation and sexual isolation are often the first barriers between closely related species, yet they are rarely studied together, making their relative contributions to reproductive isolation unclear. We conducted the first comprehensive study of both barriers in Hawaiian swordtail crickets (Laupala), focusing on the recently diverged, sympatric species pair Laupala kona and Laupala hualalai. Using genomic data, we confirmed that the two species are genetically distinct, which can only be achieved by strong reproductive isolation through a prolonged time period. Through field surveys, we quantified microhabitat use, spatial distribution, and diets, and found extensive ecological overlap. Both species occupied similar substrates, elevations, and microclimates, and occurred in mixed-species aggregations. They only differ in their diets (inferred from stable isotopes), which might have some implications in reducing encounter rates. Despite this weak habitat isolation, they have divergent sexual traits and exhibit strong sexual isolation in lab assays. The species differ significantly in male pulse rate and cuticular hydrocarbon profiles, and females consistently preferred conspecific song stimuli. Mating trials showed almost complete sexual incompatibility between heterospecific pairs, with very rare interspecies copulations. Together, these results demonstrate that sexual isolation, rather than habitat partitioning, maintains species boundaries between L. hualalai and L. kona in sympatry. Our findings highlight the sufficiency of sexual isolation to prevent hybridization even in the absence of strong ecological divergence, providing rare empirical evidence that sexual barriers alone can maintain reproductive isolation in natural populations.

evolutionary biology↗

bioRxiv2024

Functional characterization of luciferase in a brittle star indicates parallel evolution influenced by genomic availability of haloalkane dehalogenase

Determining why convergent traits use distinct versus shared genetic components is crucial for understanding how evolutionary processes generate and sustain biodiversity. However, the factors dictating the genetic underpinnings of convergent traits remain incompletely understood. Here, we use heterologous protein expression, biochemical assays, and phylogenetic analyses to confirm the origin of a luciferase gene from haloalkane dehalogenases in the brittle star Amphiura filiformis. Through database searches and gene tree analyses, we also show a complex pattern of presence and absence of haloalkane dehalogenases across organismal genomes. These results first confirm parallel evolution across a vast phylogenetic distance, because octocorals like Renilla also use luciferase derived from haloalkane dehalogenases. This parallel evolution is surprising, even though previously hypothesized, because many organisms that also use coelenterazine as the bioluminescence substrate evolved completely distinct luciferases. The inability to detect haloalkane dehalogenases in the genomes of several bioluminescent groups suggests that the distribution of this gene family influences its recruitment as a luciferase. Together, our findings highlight how biochemical function and genomic availability help determine whether distinct or shared genetic components are used during the convergent evolution of traits like bioluminescence.

evolutionary biology↗

bioRxiv2023

Collective synchrony of mating signals modulated by ecological cues and social signals in bioluminescent sea fireflies

Individuals often employ simple rules that can emergently synchronise behaviour. Some collective behaviours are intuitively beneficial, but others like mate signalling in leks occur across taxa despite theoretical individual costs. Whether disparate instances of synchronous signalling are similarly organised is unknown, largely due to challenges observing many individuals simultaneously. Recording field collectives and ex situ playback experiments, we describe principles of synchronous bioluminescent signals produced by marine ostracods (Crustacea; Luxorina) that seem behaviorally convergent with terrestrial fireflies, and with whom they last shared a common ancestor over 500 mya. Like synchronous fireflies, groups of signalling males use visual cues (intensity and duration of light) to decide when to signal. Individual ostracods also modulate their signal based on the distance to nearest neighbours. During peak darkness, luminescent "waves" of synchronous displays emerge and ripple across the sea floor every [~]60 seconds, but such periodicity decays within and between nights after the full moon. Our data reveal these bioluminescent aggregations are sensitive to both ecological and social light sources. Because the function of collective signals is difficult to dissect, evolutionary convergence, like in the synchronous visual displays of diverse arthropods, provides natural replicates to understand the generalities that produce emergent group behaviour.

animal behavior and cognition↗

bioRxiv2021

Transcriptome phylogenies support ancient evolutionary transitions in bioluminescence traits of cypridinid ostracods

Although the the diversity, beauty, and intricacy of sexually selected courtship displays command the attention of evolutionists, the longevity of these traits in deep time is poorly understood. Population-based theory suggests sexual selection could either lower or raise extinction risk, resulting in high or low persistence of lineages with sexually selected traits. Furthermore, empirical studies that directly estimate longevity of sexually selected traits are uncommon. Sexually selected signals - including bioluminescent courtship - originated multiple times during evolution, allowing empirical study of their longevity after careful phylogenetic and divergence time analyses. Here, we estimate the first transcriptome-based molecular phylogeny and divergence times of Cypridinidae. We report extreme longevity of bioluminescent courtship, a trait important in mate choice and probably under sexual selection. Our relaxed-clock estimates of divergence times coupled with stochastic character mapping show luminous courtship evolved only once in Cypridinidae in a Sub-Tribe we name Luxorina at least 151 Million Years Ago (Ma) from cypridinid ancestors that used bioluminescence only in anti-predator displays, defining a Tribe we name Luminini. This time-calibrated molecular phylogeny of cypridinids will serve as a foundation for integrative and comparative studies on the biochemistry, molecular evolution, courtship, diversification, and ecology of cypridinid bioluminescence. The persistence of luminous courtship for hundreds of millions of years indicates that rates of speciation within the group exceeded extinction risk, allowing for the persistence of a diverse clade of signalling species and that sexual selection did not cause rapid loss of associated traits.

evolutionary biology↗

bioRxiv2020

Molecular evolution of luciferase diversified bioluminescent signals in sea fireflies (Crustacea:Ostracoda:Cypridinidae)

Understanding the genetic causes of evolutionary diversification is challenging because differences across species are complex, often involving many genes. However, cases where single or few genetic loci affect a feature that varies dramatically across a radiation of species would provide tractable opportunities to understand the genetics of diversification. Here, we show the diversification of bioluminescent signals in cypridinid ostracods ("sea fireflies") to be strongly influenced by a single gene, cypridinid-luciferase. We find different evolutionary processes, including selection, drift, and constraint, each acted on c-luciferase at different times during evolutionary history and impacted different phenotypes, diversifying behavioral signals across species. In particular, some amino acid sites in c-luciferase evolved under episodic diversifying selection, and are associated significantly with phenotypic changes in both enzyme kinetics and color, which impact signals directly. We also find that multiple other amino acid positions in c-luciferase evolved neutrally or under purifying selection and may have impacted the variation of color of bioluminescent signals across genera. This work provides a rare glimpse into the genetic basis of diversification across many species, showing how multiple evolutionary processes may act at different times during a radiation of species to diversify phenotypes. These results indicate not only selection but also drift and constraint may be important evolutionary drivers of species diversification. Significance statementA hallmark of life is its astounding diversity. While we are beginning to understand the drivers of biodiversity, uncovering the genetic basis remains challenging. As such, how different molecular evolutionary processes act to diversify phenotypes is a major question in biology. Here we show a single gene to be important in a riotous diversity of fantastical behaviors - the bioluminescent signals of sea fireflies - allowing us to demonstrate multiple evolutionary forces including selection, drift, and constraint contributed to diversification. Our work highlights that not only selection but also neutral processes and constraint have each worked at different times to shape phenotypic diversity.

evolutionary biology↗