Arachnids may not be a majority favorite, but the tiny creatures have accomplished some massive feats. Recent studies have shed light on a particular species⎯the Moggridgea rainbowi spiders from Kangaroo Island. These tiny creatures are proven to have crossed the giant span of the Indian Ocean, eventually reaching their destination off the south coast of Australia. Of course, spiders had already proven their expertise on the waters before with the help of surface tension, but floating across an entire ocean?
Scientists studied the probability of this occurrence and presented the shocking research to the public. One theory explains that “spiders became split from their South African relations with the separation of Africa” (Sophie Harrison). This would have happened around 95 million years ago, which limits the extent of the data covered to support this hypothesis. Researchers then took a more quantitative route and decided to explore the spider’s genes. They turned to six genes that have been well-studied by spider biologists and examined the relationships between species. After comparing evidence, they built a spider family tree and noticed something glaringly different than what they had concluded before: the Moggridgea spiders split off from their common ancestor some 2 million to 16 million years ago.
The timing of the divergence was long after Gondwana, a supercontinent that included Africa. With this new revelation, it eliminated another potential theory as well: human transportation. The spiders’ arrival in Australia was far before humans set foot in the land. With two hypotheses down, the scientists started considering the “impossible”: long-distance ocean travel.
The Moggridgea rainbowi spider is not an exceptionally huge creature. In fact, its whole body can be covered by a quarter. Now consider the width of the Indian Ocean: 10,000 kilometers. Scientists had a hard time digesting the fact that a quarter-sized arachnid could travel such a long distance and safely arrive as colony. Nonetheless, it was the only possible method of transportation that fit within the timeline of the Moggridgea ancestry.
After more studying and heated debate about this spider, the alternative theory became more conclusive. Though the Moggridgea rainbowi species are miniscule in size compared to the Indian Ocean, “there are precedents of such ocean travel” (Professor Andrew Austin). The Moggridgea are also found on the Comoros volcanic islands, which are about 340 kilometers from where they originated, mainland Africa.
Protective evolutionary traits make the Moggridgea rainbowi especially well-suited to ocean travel. For instance, if a large swatch of land washes into the sea, the spiders may be able to hide out in their own buried nests for the journey. They effectively ration their food and sustain energy without consuming too much. Even more surprisingly, they have an oxygen bank they can survive on during periods of temporary flooding. Their abilities to resist drowning and maximize their resources make them the perfect candidates for ocean travel.
The Moggridgea species demonstrates the magnitude of their capabilities in seemingly uninhabitable conditions. This impressive feat has still yet to be explored in other spider species, but scientists are looking forward to uncovering more talents that these rather small arachnids have to offer.