Biology subjects

Luehrmann, M.

Publications and source records attributed to Luehrmann, M..

4 recordsLinked to original sources

bioRxiv2026

A Deep Phylogenetic Split Between Short- and Long-Wavelength-Tuned Visual Systems in Surgeonfishes (Acanthuridae)

The light environment, coupled with ecology, is widely thought to drive visual adaptation, creating species-specific visual niches. However, coral reef ecosystems experience continuous spatiotemporal variations in light conditions, and mechanisms such as phenotypic plasticity may be essential for coral reef animals to adjust to such changing sensory requirements. It remains unclear how widespread colour vision plasticity is, or the extent to which ecology and phylogeny drive plasticity in coral reef fishes. Using a comparative transcriptomic approach across 22 species, we aimed to investigate visual plasticity within a prominent coral reef fish family, surgeonfishes (Acanthuridae), in response to changes in the light environment throughout development and across seasons in adults. Surprisingly, we uncovered a deep phylogenetic split (~42 mya) in visual opsin gene expression profiles, with Nasinae expressing a shorter-shifted palette than Acanthurinae, which coincides with the divide between water-column and benthic-feeding modalities during the speciation of their last common ancestor. However, opsin gene expression showed little variation in response to seasonal or ontogenetic shifts in the light environment, nor in the broad functional feeding groups extant species from both subfamilies fall under. Thus, the invariable visual gene expression observed in present-day surgeonfishes appears to be dictated by phylogenetic inertia, despite rapid diversification into a range of ecological niches. This suggests that spectral tuning into two main modalities, short and long, reduces the need for visual plasticity, allowing larger and more mobile coral reef fishes to conduct visually guided behaviours across the entire range of light environments they encounter.

evolutionary biology↗

bioRxiv2021

Multiple ancestral duplications of the red-sensitive opsin gene (LWS) in teleost fishes and convergent spectral shifts to green vision in gobies

Photopigments, formed by an opsin protein bound to a light-sensitive chromophore, underlie vertebrate vision. Long-wavelength-sensitive (LWS) opsins mediate red-light detection, and most teleosts retain a single functional LWS1. A shorter-shifted green-sensitive paralog (LWS2) is found only in a few lineages. By mining teleost genomes and sequencing retinal transcriptomes, we identify elopomorphs as an additional lineage retaining LWS2 (alongside characins and osteoglossomorphs), and we reveal a previously overlooked shorter-shifted paralog, LWS3, restricted to gobies (Percomorpha) and arising from an ancient duplication. Structural modeling of twelve LWS opsins reveals convergent evolution at four key amino acid sites (214, 259, 261, 269) in the retinal-binding pocket, indicating convergent substitutions in human MWS, teleost LWS2, and goby LWS3 relative to red-sensitive counterparts, consistent with repeated spectral shifts toward green wavelengths. In several lineages--including characins, mormyrids, gobies, and primates--these shorter-shifted LWS opsins have functionally replaced the canonical green-sensitive RH2 opsin. Retinal transcriptomes and in situ hybridization demonstrate variable lws3 expression across gobies, with localization to a distinct double-cone member in Amblygobius phalaena, analogous to rh2 expression in other fish species. Together, these results show that repeated convergent evolution toward green sensitivity over 500 million years involves coordinated changes at the molecular, regulatory, and functional levels, providing a striking example of multilevel sensory adaptation. Significance statementVertebrate vision depends on opsins, which detect specific wavelengths of light. Most teleosts retain a single long-wavelength-sensitive opsin (LWS1), while a green-sensitive paralog (LWS2) occurs only in a few lineages. We identify a previously overlooked green-shifted opsin, LWS3, which is restricted to gobies, and show that LWS2 and LWS3 have repeatedly evolved green sensitivity through convergent amino acid changes. In parallel to the primate MWS/LWS evolution, these shorter-shifted opsins have functionally replaced the canonical green-sensitive RH2 opsin in multiple teleost lineages. By integrating genomic, structural, and expression data, we reveal how multilevel convergent evolution--from molecular tuning to photoreceptor specialization--has repeatedly shaped green-light vision over the past 500 million years of evolution, illustrating the remarkable flexibility of vertebrate visual systems.

evolutionary biology↗

bioRxiv2020

The visual ecology of Holocentridae, a nocturnal coral reef fish family with a deep-sea-like multibank retina

The visual systems of teleost fishes usually match their habitats and lifestyles. Since coral reefs are bright and colourful environments, the visual systems of their diurnal inhabitants have been more extensively studied than those of nocturnal species. In order to fill this knowledge gap, we conducted a detailed investigation of the visual systems of the coral reef fish family Holocentridae (squirrelfish and soldierfish). In addition to their nocturnality, this family is particularly interesting for dim-light vision studies due to its ecological and evolutionary connection to deeper habitats. Results showed that the visual system of holocentrids is well adapted to their nocturnal lifestyle with a rod-dominated retina. Surprisingly, rods in all species were arranged into 6-17 well-defined banks, a feature most commonly found in deep-sea fishes, that may increase the light sensitivity of the eye and/or allow colour discrimination in dim-light. Holocentrids also have the potential for dichromatic colour vision during the day with the presence of at least two spectrally different cone types: single cones expressing the blue-sensitive SWS2A gene, and double cones expressing one or two green-sensitive RH2 genes. Some differences were observed between the two subfamilies, with Holocentrinae having a slightly more developed photopic visual system than Myripristinae. Moreover, retinal topography of both ganglion cells and cone photoreceptors showed specific patterns for each cell type, likely highlighting different visual demands at different times of the day, such as feeding. Overall, their well-developed scotopic visual systems and the ease of catching and maintaining holocentrids in aquaria, make them ideal models to investigate teleost dim-light vision and more particularly shed light on the function of multibank retina and its potential for dim-light colour vision.

neuroscience↗

bioRxiv2019

Microhabitat partitioning correlates with opsin geneexpression in coral reef cardinalfishes (Apogonidae)

O_LIVertebrates exhibit diverse visual systems that vary in terms of morphology, number and distribution of spectrally distinct photoreceptor types, visual opsin genes and gene expression levels.\nC_LIO_LIIn fish, such adaptations are driven by two main factors: differences in the light environment and behavioural tasks, including foraging, predator avoidance and mate selection. Whether visual systems also adapt to small-scale spectral differences in light, between microhabitats, is less clear.\nC_LIO_LIWe suggest that differences in microhabitat use by cardinalfishes (Apogonidae) on coral reefs drive morphological and molecular adaptations in their visual systems. To test this, we investigated diurnal microhabitat use in 17 cardinalfish species and assessed whether this correlated with differences in visual opsin gene expression and eye morphology.\nC_LIO_LIWe found that cardinalfishes display six types of partitioning behaviours during the day, ranging from specialists found exclusively in the water column to species that are always hidden inside the reef matrix.\nC_LIO_LIUsing data on visual opsin gene expression previously characterized in this family, it was discovered that species in exposed habitats had increased expression of the short-wavelength sensitive violet opsin (SWS2B) and decreased expression of the dim-light active rod opsin (RH1). Species of intermediate exposure, on the other hand, expressed opsins that are mostly sensitive to the blue-green central part of the light spectrum (SWS2As and RH2s), while fishes entirely hidden in the reef substrate had an increased expression of the long-wavelength sensitive red opsin (LWS).\nC_LIO_LIWe found that eye size relative to body size significantly differed between cardinalfish species, and relative eye size decreased with an increase in habitat exposure.\nC_LIO_LIRetinal topography did not show co-adaptation with microhabitat use, but instead with feeding mode.\nC_LIO_LIWe suggest that, although most cardinalfishes are nocturnal foragers, their visual systems are also adapted to both the light intensity and the light spectrum of their preferred diurnal microhabitat.\nC_LI

ecology↗