This Slug Should Be Impossible

Sacoglossan sea slugs, including species like Costasiella kuroshimae (leaf sheep) and Elysia chlorotica, steal chloroplasts from algae and incorporate them into their own digestive cells to perform photosynthesis.

Sacoglossan sea slugs use specialized mouthparts called radulae to pierce algal cells and selectively extract chloroplasts while digesting other cellular components.

Sacoglossan sea slugs maintain functional stolen chloroplasts for months within animal cells despite lacking the algal nuclear DNA that normally provides essential regulatory proteins and protective enzymes.

Sacoglossan sea slugs employ multiple behavioral, structural, and selective strategies to protect stolen chloroplasts from light-induced oxidative damage without plant nuclear regulatory systems.

Scientists initially hypothesized that sacoglossan sea slugs incorporated algal nuclear genes into their genomes through horizontal gene transfer to maintain stolen chloroplasts, but rigorous genomic sequencing studies disproved this theory.

Certain sacoglossan species voluntarily sever their entire bodies at a specialized neck breakage plane, retaining only their heads which subsequently regenerate complete bodies including hearts and digestive systems within approximately seventeen days.

Sacoglossans, commonly called sap-sucking sea slugs, constitute a group of small marine gastropods distinguished by vibrant coloration, leaf-like body shapes, and chloroplast theft capabilities that vary dramatically in scale across species.

Some sacoglossan sea slugs perform voluntary autotomy - intentionally severing their own heads from their bodies - then regenerating entire new bodies from just the severed head, an ability no other animal on Earth demonstrates to this extreme degree.

For years, scientists doubted chloroplasts could function in animal cells without algal nuclear genes, hypothesizing horizontal gene transfer - cross-kingdom incorporation of algal genes into slug genomes - must explain kleptoplasty’s success.

Sacoglossan sea slugs steal chloroplasts from algae using specialized radula mouthparts to pierce algal cells, selectively retain chloroplasts while digesting other contents, and store these “kleptoplasts” in digestive tubules (diverticula) branching throughout their bodies.

Sacoglossan slugs maintain functional stolen chloroplasts for months without the algal nucleus that typically produces regulatory proteins and enzymes needed to manage reactive oxygen species (ROS) - dangerous molecules like superoxide and hydrogen peroxide that form when excess light energy damages photosynthetic machinery.