The human eye is often regarded as an intricately complex and delicate organ, essential for perceiving the world around us, yet remarkably limited in its capacity to repair itself after injury. Contrasting this, the freshwater golden apple snail, Pomacea canaliculata, possesses camera-type eyes remarkably similar in structure to human eyes but with one extraordinary ability: it can completely regenerate its eyes following damage or amputation. This startling discovery, led by UC Davis biologist Alice Accorsi, opens new horizons in understanding the mechanisms of eye regeneration, potentially paving the way toward innovative therapies to restore vision in humans suffering from eye injuries.
In a groundbreaking study recently published in Nature Communications, Accorsi and her team reveal that apple snail eyes share profound anatomical and genetic similarities with their human counterparts. Camera-type eyes, characterized by a protective cornea, a focusing lens, and a retina densely populated with photoreceptors, are typically a hallmark of vertebrates. However, apple snails join a unique cohort of invertebrates—including certain spiders and cephalopods—in possessing such complex visual organs, underscoring their remarkable evolutionary convergence.
One of the most striking aspects of this research lies in the regenerative prowess of the apple snail. While humans are limited to healing superficial eye injuries, snails can regrow a fully functional eye within a month after removal. This regeneration encompasses all critical components—including the lens, retina, and optic nerve—reestablishing the complex architecture necessary for vision. Accorsi’s research meticulously delineates this process, revealing a sequence of coordinated biological stages beginning with wound closure followed by cellular proliferation, differentiation, and finally maturation of the regenerating eye structures.
Experimentally, the team employed a sophisticated mix of microscopy, dissection, and genomic analyses to map the genetic landscape active during regeneration. Their findings revealed a vast array of gene expression changes—roughly 9,000 genes showing differential expression immediately post-amputation, with over 1,000 genes still dynamically regulated after 28 days. This prolonged genetic activity suggests that although the eye appears structurally complete within a month, molecular maturation and functional integration likely continue beyond this visible endpoint.
Among the pivotal genes identified is pax6, an evolutionarily conserved master regulator of eye development renowned for its role in multiple species, from fruit flies to humans. Through genetic engineering techniques utilizing CRISPR-Cas9 genome editing, Accorsi’s group demonstrated that snails lacking functional pax6 fail to develop eyes initially, mirroring phenotypes seen in other organisms. This discovery not only confirms the fundamental genetic orchestration of eye formation but also sets the stage for probing pax6’s potential role in post-injury eye regeneration—a frontier yet to be explored fully.
The experimental tractability of the apple snail model is another crucial advantage highlighted by Accorsi. Unlike many other snail species that undergo complex metamorphosis or exhibit slow reproductive cycles, golden apple snails are highly resilient, reproduce rapidly, and thrive in laboratory environments. These practical traits make them uniquely suitable for genetic manipulation, chronicling regeneration phases, and ultimately unraveling the molecular underpinnings of sensory organ regeneration in a non-vertebrate system.
Delving deeper into the anatomical parallels, the research illustrates that apple snail eyes recapitulate the human eye’s layered architecture, including a lens capable of focusing incoming light onto a retina rich with photoreceptor cells. This camera-like design is responsible for producing high-resolution images in animals, and the regenerative regeneration of such a complex structure highlights an evolutionary achievement with immense implications for regenerative biology.
Significantly, Accorsi and her colleagues underscore that current evidence confirms the anatomical regeneration of eyes but does not yet definitively demonstrate restored sensory function. Future lines of inquiry include developing behavioral assays to verify whether regenerated eyes can truly perceive and process visual stimuli as intact eyes do. Such assessments will be pivotal to authenticate the functional success of the regeneration process, bridging the gap between morphological regeneration and actual vision restoration.
The temporal dynamics of the regenerative process further reveal intricate biological orchestration. Within the first 24 hours, the snail’s wound heals to prevent infection and fluid loss, followed by a surge in the proliferation of undifferentiated cells that migrate to the injury site. Over approximately ten days, these cells differentiate into the complex constituents of the eye, and by day fifteen, the full complement of eye structures including the optic nerve, though immature, is present. These developmental milestones chart a regenerative timeline that could inspire analogous medical interventions in vertebrates.
Genomic editing techniques developed in this study open the door to targeted mutagenesis to parse the roles of individual genes in regeneration. By selectively knocking out or modulating genes of interest, researchers can dissect biological pathways governing cellular proliferation, differentiation, and morphogenesis during eye regrowth. This systemic approach promises to identify genetic circuits that, if conserved in humans, might be activated to stimulate regenerative processes that are currently dormant or ineffective.
The implications of this research extend far beyond mollusk biology. If mammalian counterparts to the apple snail’s regenerative genes exist—and preliminary genomic analyses suggest many do—therapies could eventually be designed to rekindle regenerative capacities in human eyes. This would represent a revolutionary leap in treating ocular diseases and trauma, which today often lead to irreversible vision loss.
The scientific community has largely overlooked mollusks as models for regeneration research in favor of vertebrates or simpler organisms like planarians. However, Accorsi’s work reshapes this paradigm, positioning the apple snail as a genetically tractable, experimentally convenient organism that offers new insights into the evolution and mechanics of complex organ regeneration. By bridging non-vertebrate anatomy with regenerative genomics, this study urges a reconsideration of animal models used in developmental biology.
While significant challenges remain, including demonstrating functional vision restoration and translating these findings into mammalian systems, the foundational groundwork laid by Accorsi’s team establishes an exciting new avenue of research. It promises to unravel long-standing mysteries about why humans cannot regenerate vital organs such as eyes and, importantly, whether this limitation is surmountable by activating evolutionary conserved genetic machinery.
This research was conducted with support from the Howard Hughes Medical Institute, the Society for Developmental Biology, the American Association for Anatomy, and the Stowers Institute for Medical Research. The cross-disciplinary collaboration involved scientists at UC Davis and the Stowers Institute, demonstrating the power of collaborative science to tackle one of biology’s most fascinating puzzles: the regeneration of complex sensory organs.
Subject of Research: Animals
Article Title: A genetically tractable non-vertebrate system to study complete camera-type eye regeneration
News Publication Date: 6-Aug-2025
Web References: https://www.nature.com/articles/s41467-025-61681-6
References: Accorsi A, Gattamraju A, Pardo B, Ross E, Corbin TJ, McClain M, Weaver K, Delventhal K, Morrison JA, McKinney MC, McKinney SA, Sanchez Alvarado A. A genetically tractable non-vertebrate system to study complete camera-type eye regeneration. Nature Communications. 2025 Aug 6; DOI: 10.1038/s41467-025-61681-6.
Image Credits: Alice Accorsi, UC Davis
Keywords: Regeneration, Developmental biology, Molecular biology, Gastropods, Health and medicine
