Cnidarians: Diversity and Evolution of Cnidarian Visual Systems

Birch, Sydney; Picciani, Natasha; Oakley, Todd H.; Plachetzki, David C.

doi:10.1007/978-3-031-23216-9_2

Cited by 5 publications

(4 citation statements)

References 178 publications

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“…4). This pattern is echoed at macroevolutionary scales across cnidarian species in which neuropeptide (e.g., glutamate), light (e.g., solar insolation and moonlight) and temperature variations (e.g., diel-light cycles) regulate reproductive physiology and phenology [75][76][77][78][79][80] .…”

Section: Discussionmentioning

confidence: 99%

“…Coral planulae detect changes in light wavelengths 79,97 , showing preferences for substrate color during settlement 97,98 , and are more likely to settle where crustose coralline algae are adapted to similar light environments as those of their coral parents 99 . Together, these cues act as a depth gauge, creating habitat choice patterns between environments with suitable irradiances that create ecological partitioning from an early life stage 80,99 . Moreover, the long interval from juvenile to adult stages typical of many broadcast-spawning corals further lends itself to long pre-reproductive selection and the extirpation of mismatched habitat-genotype individuals via immigrant inviability 44 .…”

Section: Light As a Driver Of Diversity On Reefsmentioning

confidence: 99%

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Speciation across depth gradients in reef corals

Prada,

Gómez-Corrales,

González

et al. 2024

Preprint

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Ecological speciation through adaptation to different habitats has been proposed for a variety of terrestrial, freshwater, and marine species. Such divergence of lineages in the absence of strong geographic isolation occurs most readily when the same traits are involved in both adaptation to different ecologies and reproductive isolation. In corals with photosynthetic symbionts and environment-mediated spawning events, adaptation to different light regimes associated with varying depths could provide opportunities for this kind of speciation. Here we show that differences in depth distribution are common in sister lineages of corals from a variety of taxonomic groups and locations. We then explore in detail the molecular drivers behind depth-associated adaptive divergence by documenting patterns of sequence divergence for proteins related to environmental sensing in depth-segregated and light-dependent lineages in the Orbicella species complex. Specifically, we analyzed 1) two ecotypes of Orbicella faveolata that exhibit genetic divergence across a depth gradient that may reflect an incipient recent (~200 Kyr; < 6K generations) speciation event, and 2) two depth-segregated sister species (~500 Kyr), O. annularis and O. franksi, that have been monitored for over two decades and spawn at different times following sunset. Genome-wide variation suggests divergence across depth occurred by adaptation via positive selection on rhodopsin-like G-protein-coupled receptors (GPCRs). These molecules are known to serve as chemo/photo/thermo-receptors mediating environmental transduction signals to enhance physiological adaptation across different environments, while also involved in reproductive isolation via differences in time of spawning in corals. Our study posits a molecular mechanism for the origin of depth-segregated coral species, common across the anthozoan tree of life, in systems in which ecological divergence operates at spatial scales smaller (< 1 km) than their larval dispersal potential, and highlights avenues contributing to generating biodiversity in the sea.

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Section: Discussionmentioning

confidence: 99%

Section: Light As a Driver Of Diversity On Reefsmentioning

confidence: 99%

Speciation across depth gradients in reef corals

Prada,

Gómez-Corrales,

González

et al. 2024

Preprint

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“…Larval phototaxis is widespread in the marine environment and has been implicated as a strategy for predator avoidance, dispersal, diel vertical migrations, and larval settlement (1, [53][54][55][56]. H. symbiolongicarpus planulae are phototactic and neuropeptides including RFamide play a role in relaying photosensory stimuli to epithelial muscular cells, directing the movement of the photoresponse (6,7).…”

Section: Phototaxis and Dispersal In Cnidarian Planulaementioning

confidence: 99%

“…The activation of PDE6 by Gt G-proteins involves the displacement of its subunit, PDE6 gamma (PDE6G), an intrinsically disordered protein that remains bound to PDE6 while inactive. The rapid release of inhibition of PDE6 by PDE6G is thought to provide the fast cascade dynamics required for image-forming vision in the mammalian retina (99), but this is an unlikely requirement of most cnidarian photosystems including H. symbiolongicarpus planulae (53,100). In fact, cnidops-mediated phototransduction bears similarity to olfactory transduction in mammals, where cascade dynamics are much slower than ciliary photoreceptor dynamics (39).…”

Section: Developmental Transcriptomics Implicate Photosensation and S...mentioning

confidence: 99%

Phototactic preference and its genetic basis in the planulae of the colonial Hydrozoan Hydractinia symbiolongicarpus

Birch,

McGee,

Provencher

et al. 2024

Preprint

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Background Marine organisms with sessile adults commonly possess motile larval stages that make settlement decisions based on integrating environmental sensory cues. Phototaxis, the movement toward or away from light, is a common behavioral characteristic of aquatic and marine metazoan larvae, as well as of algae, protists, and fungi. In cnidarians, behavioral genomic investigations of motile planulae larvae have been conducted in anthozoans (corals and sea anemones) and scyphozoans (true jellyfish), but such studies are presently lacking in hydrozoans. Here, we examined the behavioral genomics of phototaxis in planulae of the hydrozoan Hydractinia symbiolongicarpus. Results A behavioral phototaxis study of day 3 planulae indicated preferential phototaxis to green (523 nm) and blue (470 nm) wavelengths of light, but not red (625 nm) wavelengths. A developmental transcriptome study where planula larvae were collected from four developmental time points for RNA-seq revealed that many genes critical to the physiology and development of ciliary photosensory systems are dynamically expressed in planula development and correspond to the expression of phototactic behavior. Microscopical investigations using immunohistochemistry and in situ hybridization demonstrated that several transcripts with predicted function in photoreceptors, including cnidops class opsin, CNG ion channel, and CRX-like transcription factor, localize to ciliated bipolar sensory neurons of the aboral sensory neural plexus, which is associated with the direction of phototaxis and the site of settlement. Conclusions The phototactic preference displayed by planulae is consistent with the shallow sandy marine habitats they experience in nature. Our genomic investigations add further evidence of similarities between cnidops-mediated photoreceptors of hydrozoans and other cnidarians and ciliary photoreceptors as found in the eyes of humans and other bilaterians, suggesting aspects of their shared evolutionary history.

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