This article is from
Creation 44(3):55, July 2022

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Severed slug’s slick survival system

by Philip Robinson

The sea slug’s head immediately began moving around on its own after becoming separated from its body. This shocked discoverer Sayaka Mitoh, then a doctoral student at Nara Women’s University in Japan. “We thought that it would die soon without a heart and other important organs, but we were surprised again to find that it regenerated the whole body.”¹ After this accidental discovery, Mitoh conducted further research on two species of sea slug, Elysia cf. marginata and Elysia atroviridis.²

Sayaka Mitoh © 2021 Elsevier Inc.

Voluntary shedding of a body part is called autotomy (Greek ‘self-cutting’). It is thought that losing the body is a defensive mechanism in reaction to a build-up of parasites or toxins in the body, which can inhibit reproduction. The sea slugs have a “transverse groove at their neck, which appears to be a predetermined ‘breakage plane’” from which the body breaks away. Mitoh and her colleague, aquatic ecology professor Yoichi Yusa, gently tied a fine nylon string around this groove in six slugs. Five of them autotomized at that groove within a day. The remaining slug took nine days because the string shifted. After autotomy, E. marginata regenerated its entire body in about twenty days. E. atroviridis took only seven.

Both species are sacoglossan or ‘solar-powered’ sea slugs, thanks to chloroplasts that they integrate into their bodies from algae that they eat. (Chloroplasts are tiny factories that plants use to photosynthesize, i.e. make energy-containing sugars from sunlight, water, and air.) This process is known as kleptoplasty (Greek: ‘plast-stealing’). The chloroplasts continue their photosynthesis from light passing through the translucent skin of the slug. The animals can fuel their bodies from the chloroplasts’ photosynthesis, because of the way their digestive systems are spread around their bodies.

Sacoglossan sea slugs are the only multicellular animals known to do this. Mitoh and Yusa suggest that this ability enables them to survive long enough to regenerate another body after shedding the previous one.

The researchers conclude that “autotomy in this study is remarkable in that animals with complex body plans can survive even if they lose the main body.”

Evolutionists must assert that this system evolved by a naturalistic trial-and-error, step-by-step process. Imagine a sea slug that had accumulated accidental DNA changes (mutations) that caused it to cast off its body. Unless it had already evolved all of the machinery and programming required to regenerate its entire cast-off body, it would be dead, and there would be no further offspring, obviously. So those DNA changes would not pass to future generations, and the whole process would have come to an end. In short, it seems that, like for so many other natural marvels, all the components of the system would need to be present together to be of any benefit. Which means it could not have evolved by any Darwinian process in ‘stages’. Such a wonder of nature should rightly be ascribed to the Creator God of Genesis.