Rosa Rubicondior: Malevolent Design - We COULD Have Been Designed To Re-Grow Lost Or Damaged Eyes

This Snail’s Eyes Grow Back: Could They Help Humans do the Same? | UC Davis

First, we had the example of Australian lizards which, unlike humans, have been endowed with immunity to snake venom through a simple mutation — the kind of change that creationists like William A. Dembski of the Discovery Institute would insist is the result of "intelligent design" because it is both complex and specified.

Now we have the example of the aquatic golden apple snail, Pomacea canaliculata, which — again, unlike humans — can regenerate a lost or damaged eye. The snail’s eye is genetically and structurally similar to the mammalian eye, so there appears to be no reason why an omnibenevolent, omniscient intelligent designer could not have endowed humans and other animals with that ability too. And of course, according to William A. Dembski and Michael J. Behe, the irreducibly complex eye and the complex, specified genetic information are both evidence for intelligent design by the same intelligent designer that designed the mammalian eye and it genetic underpinning.

Creationists, of course, believe that humans are the pinnacle of their putative intelligent designer’s work. So, from their viewpoint, the only reasons it didn't grant us the ability to regenerate eyes — or to resist snake venom — must be that it either didn’t want to, didn’t think to, or didn’t know how to. Yet all of those options are inconsistent with the claimed attributes of being omnipotent, omniscient, and omnibenevolent.

Which leaves us with only one other explanation: that it wants us to suffer when we damage or lose an eye.

All rather strange, really — especially considering that, according to the Bible, God views blemishes such as blindness as a form of profanity:

And the Lord spake unto Moses, saying, Speak unto Aaron, saying, Whosoever he be of thy seed in their generations that hath any blemish, let him not approach to offer the bread of his God.

For whatsoever man he be that hath a blemish, he shall not approach: a blind man, or a lame, or he that hath a flat nose, or any thing superfluous, Or a man that is brokenfooted, or brokenhanded, Or crookbackt, or a dwarf, or that hath a blemish in his eye, or be scurvy, or scabbed, or hath his stones broken;

No man that hath a blemish of the seed of Aaron the priest shall come nigh to offer the offerings of the Lord made by fire: he hath a blemish; he shall not come nigh to offer the bread of his God.

He shall eat the bread of his God, both of the most holy, and of the holy. Only he shall not go in unto the vail, nor come nigh unto the altar, because he hath a blemish; that he profane not my sanctuaries: for I the Lord do sanctify them.

And Moses told it unto Aaron, and to his sons, and unto all the children of Israel.

Leviticus 21:16-24

Almost as an added insult to the humans it denied this regenerative ability to, while giving it to golden apple snails, the golden apple snail is a major invasive agricultural pest which causes widespread damage to rice crops, when it gets into paddy fields.

Golden Apple Snail (Pomacea canaliculata): The golden apple snail is a large freshwater gastropod native to South America, particularly the river systems of the Amazon Basin. It belongs to the family Ampullariidae, commonly known as apple snails, and has become infamous as an aggressive invasive species in many parts of Asia and elsewhere.

Habitat and Invasive Status

Originally introduced to Asia in the 1980s as a potential food source, Pomacea canaliculata quickly established itself in rice paddies, wetlands, and irrigation canals. With few natural predators and voracious feeding habits, it caused severe damage to crops, especially rice, earning it the status of a major agricultural pest.

Its tolerance for a wide range of environmental conditions — including low oxygen levels and periodic droughts — has aided its spread. It can survive out of water for extended periods by sealing itself inside its shell with a protective operculum.

Nervous System and Eye Regeneration

Pomacea canaliculata has attracted scientific interest due to its remarkable regenerative abilities, particularly its capacity to regrow a lost or damaged eye — a rare trait among animals with complex camera-type eyes. These eyes are structurally and genetically comparable to those of vertebrates, making the snail a valuable model organism in neurobiology and regenerative medicine.

Its regenerative ability is believed to involve the activation of stem-cell-like cells and the reactivation of genes normally used during embryonic development. This raises intriguing evolutionary and biomedical questions about why such traits have been lost or suppressed in other lineages, such as mammals.

Reproduction

Golden apple snails lay distinctive bright pink egg clutches above the waterline, a reproductive strategy that protects the eggs from aquatic predators. A single female can lay hundreds of eggs, contributing to their rapid population growth and invasive potential.

Ecological Impact
The species poses a serious threat to biodiversity by outcompeting native snails and altering aquatic ecosystems. Control measures include mechanical removal, biological controls, and pesticide use, but none have proved entirely effective.

The discovery of this regerative ability was by a team of researchers led by Assistant Professor, Alice Accorsi of the University of California Davis (UC Davis), who have just published their findings, open access, in Nature Communications and announced it in a UC Davis News item.

This Snail’s Eyes Grow Back: Could They Help Humans do the Same?
Human eyes are complex and irreparable, yet they are structurally like those of the freshwater apple snail, which can completely regenerate its eyes. Alice Accorsi, assistant professor of molecular and cellular biology at the University of California, Davis, studies how these snails regrow their eyes — with the goal of eventually helping to restore vision in people with eye injuries.
In a new study published Aug. 6 in Nature Communications, Accorsi shows that apple snail and human eyes share many anatomical and genetic features.

Apple snails are an extraordinary organism. They provide a unique opportunity to study regeneration of complex sensory organs. Before this, we were missing a system for studying full eye regeneration.

Assistant Professor, Alice Accorsi, lead author
formerly, Stowers Institute for Medical Research
Kansas City, MO, USA
Now, Department of Molecular and Cellular Biology
University of California, Davis, CA, USA.

Her team also developed methods for editing the apple snail’s genome, which will allow them to explore the genetic and molecular mechanisms behind eye regeneration.

A not-so-snail’s paced snail

The golden apple snail (Pomacea canaliculata) is a freshwater snail species from South America. It’s now invasive in many places throughout the rest of the world, but Accorsi said the same traits that make apple snails so invasive also make them a good animal to work with in the lab.

Apple snails are resilient, their generation time is very short, and they have a lot of babies.

Assistant Professor, Alice Accorsi.

In addition to being easy to grow in the lab, apple snails have “camera-type” eyes — the same type as humans.

Snails have been known for their regenerative abilities for centuries — in 1766, a researcher noted that decapitated garden snails can regrow their entire heads. However, Accorsi is the first to leverage this feature in regenerative research.

When I started reading about this, I was asking myself, why isn’t anybody already using snails to study regeneration? I think it’s because we just hadn’t found the perfect snail to study, until now. A lot of other snails are difficult or very slow to breed in the lab, and many species also go through metamorphosis, which presents an extra challenge.

Assistant Professor, Alice Accorsi.

Eyes like a camera

There are many types of eyes in the animal kingdom, but camera-types eyes are known for producing particularly high-resolution images. They consist of a protective cornea, a lens for focusing light and a retina that contains millions of light-detecting photoreceptor cells. They are found in all vertebrates, some spiders, squid and octopi, and some snails.

Using a combination of dissections, microscopy and genomic analysis, Accorsi’s team showed that the apple snail’s eyes are anatomically and genetically similar to human eyes.

We did a lot of work to show that many genes that participate in human eye development are also present in the snail. After regeneration, the morphology and gene expression of the new eye is pretty much identical to the original one.

Assistant Professor, Alice Accorsi.

How to regrow an eye

So, how do the snails regrow their eyes after amputation? The researchers showed that the process takes about a month and consists of several phases. First, the wound must heal to prevent infection and fluid loss, which usually takes around 24 hours. Then, unspecialized cells migrate and proliferate in the area. Over the course of about a week and a half, these cells specialize and begin to form eye structures including the lens and retina. By day 15 post-amputation, all of the eye’s structures are present, including the optic nerve, but these structures continue to mature and grow for several more weeks.

We still don't have conclusive evidence that they can see images, but anatomically, they have all the components that are needed to form an image. It would be very interesting to develop a behavioral assay to show that the snails can process stimuli using their new eyes in the same way as they were doing with their original eyes. That’s something we’re working on.

Assistant Professor, Alice Accorsi.

The team also investigated which genes were active during the regeneration process. They showed that immediately after amputation, the snails had about 9,000 genes that were expressed at different rates compared to normal adult snail eyes. After 28 days, 1,175 genes were still expressed differently in the regenerated eye, which suggests that although the eyes look fully developed after a month, complete maturation might take longer.

Genes for regeneration

To better understand how genes regulate regeneration, Accorsi developed methods to edit the snails’ genome using CRISPR-Cas9.

The idea is that we mutate specific genes and then see what effect it has on the animal, which can help us understand the function of different parts of the genome.

Assistant Professor, Alice Accorsi.

As a first test, the team used CRISPR/Cas9 to mutate a gene called pax6 in snail embryos. Pax6 is known to control the development and organization of brain and eye in humans, mice and fruit flies. Like humans, snails have two copies of each gene — one from each parent. The researchers showed that when apple snails have two non-functional versions of pax6, they develop without eyes, which shows that pax6 is also essential for initial eye development in apple snails.

Accorsi is working on the next step: testing whether pax6 also plays a role in eye regeneration. To determine this, researchers will need to mutate or turn off pax6 in adult snails and then test their regenerative ability.

She is also investigating other eye-related genes, including genes that encode specific parts of the eye, like the lens or retina, and genes that control pax6.

If we find a set of genes that are important for eye regeneration, and these genes are also present in vertebrates, in theory we could activate them to enable eye regeneration in humans.

Assistant Professor, Alice Accorsi.

Additional authors on the study are Asmita Gattamraju of UC Davis, and Brenda Pardo, Eric Ross, Timothy J. Corbin, Melainia McClain, Kyle Weaver, Kym Delventhal, Jason A. Morrison, Mary Cathleen McKinney, Sean A. McKinney and Alejandro Sanchez Alvarado of the Stowers Institute for Medical Research. Accorsi performed most of the research for this study at Stowers Institute for Medical Research, where she worked as a postdoctoral fellow before joining UC Davis in 2024.

Publication:
Accorsi, A., Pardo, B., Ross, E. et al.
A genetically tractable non-vertebrate system to study complete camera-type eye regeneration. Nat Commun 16, 6698 (2025). https://doi.org/10.1038/s41467-025-61681-6

Abstract
Camera-type eyes are complex sensory organs susceptible to irreversible damage. Their repair is difficult to study due to the paucity of camera-type eye regeneration models. Identifying a genetically tractable organism with the ability to fully regenerate complete camera-type eyes would help overcome this difficulty. Here, we introduce the apple snail Pomacea canaliculata, capable of full regeneration of camera-type eyes even after complete resection. We defined anatomical components of P. canaliculata eyes and genes expressed during crucial steps of their regeneration. By exploiting the unique features of this organism, we successfully established stable mutant lines in apple snails. Our studies reveal that, akin to humans, pax6 is indispensable for eye development in apple snails, establishing this as a research organism to unravel the mechanisms of camera-type eye regeneration. This work expands our understanding of complex sensory organ regeneration and offers a way to explore this process.

Introduction
The proper functioning of organs is intricately tied to their embryonic development, a complex and stereotypical multi-step process involving tissue organization and cell differentiation in the context of whole-body development. Post-embryogenesis, many animals lose the ability to fully regenerate new organs, some retain regenerative capacities within certain tissue or age and others exhibit remarkable abilities, regenerating entire organisms from small body portions^1,2. Regeneration involves steps such as wound healing, detection of missing structures, activation of cell proliferation, determination of anatomical patterning, growth and integration of new tissues into the existing body^1,2. Despite numerous studies on mechanisms driving regeneration in different organisms and tissues, many questions persist about the key features of a regeneration-permissive environment.

Eyes serve as fundamental sensory organs for numerous species, enabling exploration and interaction with their environments. The camera-type eye stands out as a complex and highly specialized organ, seemingly eluding complete regeneration after full resection resulting in irreversible loss of this organ after injury or damage. Camera-type eyes are capable of high-resolution image formation and are characterized by a single closed chamber, a lens, a cornea and a retina housing numerous photoreceptor cells equipped with molecular machinery for light detection. Examples of these can be found in human and more broadly in vertebrates, and among spiders and mollusks^3,4,5. Camera-type eyes are just one of the eye types present among metazoans. The pigmented cup is a non-image-forming eye type, featured by planarians and distinguished by a cup housing photoreceptors and filled with dark pigments^3,4,5. Bivalves, insects and decapods are examples of organisms with compound eyes, which result from several smaller units known as ocelli organized into a larger organ^3,4,5.

In the past, research on eye regeneration has predominantly concentrated on complete regrowth of simpler planarian pigmented cups⁶ and on partial regeneration of camera-type eyes in vertebrates with robust regenerative abilities, such as fishes, newts and frogs^7,8,9,10. These remarkable animals can repair specific components following minor injuries, such as lens or retinal cell ablations, through the activation of the ciliary marginal zone or of Müller glial cells residing in the mature retina^7,9,10. While these studies have significantly enhanced our understanding of eye regeneration, a mechanistic comprehension of complete adult camera-type eye regeneration remains elusive.

To overcome the existing limitation and expand our understanding of visual system regeneration, an organism characterized by camera-type eyes, robust regenerative potential and amenability to genome manipulation would be highly advantageous. The prevalence of camera-type eyes spans various animal phyla, including cnidarians, annelids, mollusks, crustaceans, arthropods and vertebrates^3,4,5. In 1766, Spallanzani described the remarkable regenerative potential of garden snails following head amputations11. More recently, reports indicated the ability of certain gastropods to regenerate their visual systems^12,13,14. These initial findings suggest gastropods could be useful organisms for investigating complete camera-type eye regeneration. Thus, we focused on developing a gastropod model amenable to genome manipulation¹⁵. Pomacea canaliculata, also known as the golden apple snail, is an amphibious freshwater gastropod native to South America and belonging to the Ampullariidae taxon¹⁶. These organisms exhibit resilience to diverse environmental conditions, breed throughout the year and have successfully completed their life cycle in captivity, making them an ideal organism for laboratory maintenance¹⁶. P. canaliculata is diploid¹⁷ and both its nuclear (440 Mb) and mitochondrial genomes have been sequenced, assembled and annotated^18,19,20.

Here, we characterize the camera-type eye of P. canaliculata and describe the complete regeneration of this sensory organ after complete amputation. We also report on methods for collecting and micro-injecting zygotes and for culturing embryos. These protocols allowed us to introduce CRISPR-Cas9 technology to edit the apple snail genome and obtain stable mutant lines in P. canaliculata. Finally, we show that pax6 function in eye development has been conserved in apple snails by developing the first pax6^−/− lophotrochozoan. This work opens the door to studying the function of genes potentially involved in camera-type eye regeneration in this, now genetically tractable, organism.

A Adult P. canaliculata. B Eye bulb and eye stalk with cornea (dashed line). C Isolated optic nerve and retina with the lens enclosed in it. D Isolated lens held with tweezers in front of a paper with the letter F printed in font size 5. E Hematoxylin and eosin (H&E) staining of P. canaliculata2 eye longitudinal sections. Cornea (dashed line on the left), anterior chamber (red arrow), lens (orange arrow), posterior chamber, retina, optic nerve and surrounding connective tissue, muscle tissue and extracellular matrix (ECM) can be distinguished. The 2 insets highlight the cornea and the anterior part of the lens (blue dashed line) and a portion of the retina (black dashed line). In the latter, a photoreceptor (white dashed line), the photoreceptor outer segments (yellow arrow), pigment granules (green arrow), photoreceptor inner segments (blue arrow) and neuropile (purple arrow) are shown. Arrows in (E) and images in (F–K) have the same color-code. TEM images of (F) anterior chamber filled with ECM; G lens with a densely packed structure; H outer segment of rhabdomeric photoreceptors characterized by microvilli; I pigment granules; J densely packed photic vesicles occupy an extensive portion of the photoreceptor cytoplasm together with rare mitochondria (white arrowhead) and ribosomes (black arrowheads), n nucleus; K neuropile, or bundle of axons forming the optic nerve, filled with heterogeneous vesicles. The images showed in (E–K) are representative of data collected through three independent experiments. L Schematic representation of eye anatomy for human (Hs), apple snail (Pc) and Drosophila (Dm). M Gene Ontology (GO) enrichment analysis of P. canaliculata (Pc) genes bioinformatically defined as orthologs of human (Hs) and/or fly (Dm) genes. For this analysis only GO terms related to eye development and function were taken into consideration. The plot shows the number of genes for each GO term that can be found in both snail and human but not in fly (first row), in snail, human and fly (middle row), or in snail and fly but not in human (last row). Adjusted p value cutoff of 1e−5. Manually selected representative terms (see Supplementary Fig. 1 and Supplementary Data 1).

A Regeneration time course after complete amputation of the eye bulb. B–E Longitudinal sections of the eye stalk during eye regeneration time course stained with either H&E (top images) or anti-BrdU (magenta) and anti-H3P (cyan) (central and bottom row of images). The dashed lines represent where the cut for eye amputation was performed. BrdU and H3P positive cells where counted in the tissue above the dashed lines. F Quantification of BrdU positive cells in the regenerating tissue area during the eye regeneration time course. n = 3 snails for 6 and 12 dpa; n = 4 snails for Intact and 1 dpa; n = 5 snails for 3, 9, 15 and 28 days post amputation (dpa); n = 6 snails for 21 dpa; for each sample 4 sections were analyzed; non-parametric Kruskal−Wallis ANOVA with Dunn’s post hoc multiple comparisons test determined statistical differences between regenerating samples and Intact eye; adjusted p values are <0.0001 for 6 and 9 dpa, 0.0035 for 12 and 21 dpa and 0.0009 for 28 dpa. G Quantification of the eye bulb area during the eye regeneration time course. n = 3 snails/time point, 3 sections each; one-way ANOVA with Tukey’s post hoc multiple comparisons test determined statistical differences between samples; adjusted p values are 0.0046 for 15 vs 12 dpa, 0.0447 for 28 vs 21 dpa and <0.0001 for Intact vs 28 dpa. H Quantification of the relative area of the eye bulb components (lens in red, photoreceptor microvilli in yellow, pigmented layer in green, photoreceptor inner segment in blue and neuropile in purple) during the eye regeneration time course. Data are represented as mean ± SEM. n = 3 snails/time point, 3 sections each. *p value < 0.05, **p value < 0.01, ns non-significant (see Supplementary Fig. 2).

Accorsi, A., Pardo, B., Ross, E. et al.
A genetically tractable non-vertebrate system to study complete camera-type eye regeneration. Nat Commun 16, 6698 (2025). https://doi.org/10.1038/s41467-025-61681-6

Copyright: © 2025 The authors.
Published by Springer Nature Ltd. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The ability of the golden apple snail to regenerate a lost or damaged eye presents a serious challenge to proponents of Intelligent Design, who argue that biological systems are the product of a purposeful, benevolent, and all-powerful designer. The snail’s eye is structurally and genetically similar to the mammalian eye — often cited by creationists as a marvel of design — yet, unlike humans, the snail can regrow its eye if it is injured or removed. This capability raises the obvious question: why would an intelligent designer grant this useful trait to a mollusc but withhold it from the supposed pinnacle of creation — humans?

For ID creationists, the dilemma is twofold. First, the trait itself undermines the notion that complex biological features like the eye must be “irreducibly complex” and therefore incapable of evolving. The snail’s regenerative ability appears to rely on repurposed developmental genes and cellular pathways — a hallmark of **evolutionary tinkering**, not top-down engineering. Second, it calls into question the motivations of the alleged designer. If regeneration is possible within the framework of the eye’s basic design, why is it available to some organisms and not others, especially to species that would benefit from it most?

From a theological or teleological perspective, the inconsistencies are equally glaring. An omnibenevolent, omnipotent designer choosing to endow a freshwater snail with the ability to regrow an eye — while denying the same to humans, who can be traumatically blinded in any number of ways — suggests a level of arbitrariness or even cruelty. For a belief system that holds humanity to be the centrepiece of creation, this seems both illogical and deeply troubling.

In contrast, evolutionary biology offers a coherent explanation. Traits evolve in response to environmental pressures and genetic opportunity, not moral worth or divine favour. The golden apple snail’s regenerative ability likely evolved as an adaptive advantage in its ecological niche — not as a mark of design excellence, but as one more product of natural selection acting on available genetic variation.

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