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Hierarchies in light sensing and dynamic interactions between ocular and extraocular sensory networks in a flatworm.

ABSTRACT: Light sensing has independently evolved multiple times under diverse selective pressures but has been examined only in a handful among the millions of light-responsive organisms. Unsurprisingly, mechanistic insights into how differential light processing can cause distinct behavioral outputs are limited. We show how an organism can achieve complex light processing with a simple "eye" while also having independent but mutually interacting light sensing networks. Although planarian flatworms lack wavelength-specific eye photoreceptors, a 25 nm change in light wavelength is sufficient to completely switch their phototactic behavior. Quantitative photoassays, eye-brain confocal imaging, and RNA interference/knockdown studies reveal that flatworms are able to compare small differences in the amounts of light absorbed at the eyes through a single eye opsin and convert them into binary behavioral outputs. Because planarians can fully regenerate, eye-brain injury-regeneration studies showed that this acute light intensity sensing and processing are layered on simple light detection. Unlike intact worms, partially regenerated animals with eyes can sense light but cannot sense finer gradients. Planarians also show a "reflex-like," eye-independent (extraocular/whole-body) response to low ultraviolet A light, apart from the "processive" eye-brain-mediated (ocular) response. Competition experiments between ocular and extraocular sensory systems reveal dynamic interchanging hierarchies. In intact worms, cerebral ocular response can override the reflex-like extraocular response. However, injury-regeneration again offers a time window wherein both responses coexist, but the dominance of the ocular response is reversed. Overall, we demonstrate acute light intensity-based behavioral switching and two evolutionarily distinct but interacting light sensing networks in a regenerating organism.

SUBMITTER: Shettigar N

PROVIDER: S-EPMC5533540 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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Hierarchies in light sensing and dynamic interactions between ocular and extraocular sensory networks in a flatworm.

Shettigar Nishan N Joshi Asawari A Dalmeida Rimple R Gopalkrishna Rohini R Chakravarthy Anirudh A Patnaik Siddharth S Mathew Manoj M Palakodeti Dasaradhi D Gulyani Akash A

Science advances 20170728 7

Light sensing has independently evolved multiple times under diverse selective pressures but has been examined only in a handful among the millions of light-responsive organisms. Unsurprisingly, mechanistic insights into how differential light processing can cause distinct behavioral outputs are limited. We show how an organism can achieve complex light processing with a simple "eye" while also having independent but mutually interacting light sensing networks. Although planarian flatworms lack ...[more]

PMID: 28782018

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Project description:BackgroundDue to the variety of clinical presentation, some tumors may be concealed and easily misdiagnosed, leading to delays in management. We report a series of patients who initially presented to an Ophthalmic Clinic with ocular symptoms and were subsequently diagnosed with extraocular tumors.MethodsPatients who presented to the ophthalmic outpatient clinic at the Joint Shantou International Eye Center with ocular symptoms between April 2013 and December 2019 and were subsequently diagnosed with intracranial or systemic tumors were reviewed retrospectively. Clinical data, including ocular symptoms and signs, ophthalmic and systemic imaging examinations, and the results of tumor biopsies were collected and analyzed.ResultsTwenty-three patients were included in this study, of which 16 were female (69.6%) and 7 were male (30.4%). Chief complaints at the first visit included visual loss (n=20), proptosis (n=2), and diplopia (n=1). Ocular examination revealed disc pallor (n=8) and swelling (n=3), choroidal mass with or without chorioretinal detachment (n=5), and proptosis (n=2). Visual field (VF) examination was performed in 11 patients of which hemianopia (n=4) and non-specific field loss (n=7) were noted. Brain CT or MRI, together with histopathological findings from surgical biopsies confirmed the diagnosis of the intracranial tumors in 18 cases, including pituitary adenoma (n=7), meningioma (n=2), oligodendroglioma (n=1), sellar tumor (n=1), suprachiasmatic arteriovenous aneurysm (n=1), orbital glioma (n=1), multiple intracranial tumors (n=1), and sphenoid ossifying fibroma (n=1). Nasopharyngeal carcinoma (NPC) (n=3) was diagnosed with brain MRI and nasal endoscopy. Five patients were confirmed as choroidal metastasis secondary to lung cancer (n=3), hepatoma (n=1), and breast cancer (n=1).ConclusionsPatients with extraocular tumors may present initially to an ophthalmologist with ocular symptoms. It is important to identify and appropriately manage these patients to avoid unnecessary delays in future treatment.

Dataset Information

Hierarchies in light sensing and dynamic interactions between ocular and extraocular sensory networks in a flatworm.

Publications

Hierarchies in light sensing and dynamic interactions between ocular and extraocular sensory networks in a flatworm.

Similar Datasets

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