Episode 496 Two Mystery Invertebrates

**Further reading:** How did a tiny bee get to French Polynesia? Eight new species help solve a scientific mystery Secrets in the canopy: Scientists discover 8 striking new bee species in the Pacific Canopy specialist Hylaeus bees highlight sampling biases and resolve Michener’s mystery Scientists discover endoparasitic marine tapeworm trapped in Cretaceous amber **Show transcript:** Welcome to the Patreon bonus episode of Strange Animals Podcast for August 2024! It’s the start of Invertebrate August, so we have two invertebrate mysteries to discuss today, one mostly solved and one not. Let’s start with the solved mystery, about a tiny bee. In 1934, three tiny bee specimens were collected in French Polynesia, specifically on a particular type of flower in the Tuamotu Archipelago. The bees really were tiny, only 4 mm long. They weren’t described until 1965, when they were placed in the genus Hylaeus. This is a really big genus with over 500 species that live throughout the world, but the species most closely related to the newly described Tuamotu’s masked bee lives in Australia, New Guinea, and New Zealand. In case you’re kind of hazy on geography, like me, Australia, New Guinea, and New Zealand are part of what’s called Oceania, a giant chunk of the Pacific Ocean where there’s not a whole lot of land. I mean, except for Australia, which is big. The Tuamotu Archipelago is also part of Oceania, and part of French Polynesia, but it’s really remote. It consists of a spread-out collection of 78 low islands, many of them too tiny to support humans, none of them with a source of fresh water except for rain. They’re tropical and quite beautiful, with many unique animals and plants living on and around them. They’re also almost 2,500 miles, or 4,000 km away from the places where the tiny bee’s closest relatives live. Even in 1965, scientists had questions about the tiny bee. How did 4mm bees *get* to such remote islands, and were they even still around? The bees hadn’t been seen in the wild since 1934. Since the Tuamotu Archipelago has suffered from European explorers and missionaries bringing invasive species to some islands, colonization by France, and nuclear weapons testing, scientists worried the bee had gone extinct and that they would never solve the mystery of how it got there in the first place. Bees are attracted to flowers, and the three 1934 specimens were discovered on flowers, so naturally scientists had been looking for the bees on flowers. But it turns out that in the Polynesian islands, bees mostly hang out in the treetops. Once scientists figured this out, they began discovering new species of bee—eight of them in fact, collected between 2014 and 2019 from various islands in Fiji, Micronesia, and French Polynesia. All eight species are closely related to Tuamotu’s masked bee, so scientists now have a pretty good idea of how it traveled thousands of miles to get to its French Polynesian home. Its ancestors island-hopped. There are more than 1,700 islands in the Pacific Ocean, many of them barely known to humans. Researchers think there are probably a lot more species of bee to be discovered in the treetops of Pacific islands, now that they know where to look. With luck, they’ll be able to find Tuamotu’s masked bee too, quietly living out its bee life above the scientists’ heads. Next, let’s discuss our unsolved mystery. Amber, which is fossilized tree resin, is the gift that just keeps on giving to the scientific world, and our mystery involves a flatworm found in amber. The amber comes from Myanmar and dates to about 99 million years ago. In addition to bits of inorganic matter like tiny pebbles and sand grains, most organisms found in amber from this site are insects and roundworms, animals you’d expect to find on and around trees. The team examining this particular piece of amber found lots of interesting things, but then they discovered this one. The flatworm is about 10mm long and it’s beautifully preserved, which means the scientists were able to compare it to modern flatworms to see what it might be most closely related to. It’s most similar to a parasitic flatworm found in shark intestines. You know, an animal not typically found in trees. (I stole that joke from paleontologist Kenneth De Baets, by the way. Credit where credit’s due.) It isn’t a complete worm but a partial one, basically a tentacle with little hooks to keep it in place in the host animal’s digestive system. The modern worm is classified as a type of tapeworm, and tapeworms are distressingly common parasites. If you’ve ever adopted a rescue cat or dog, you’ve probably had to have it treated for a tapeworm infestation. Luckily, tapeworms are also very specific about which species they parasitize, so you can’t get tapeworms from a pet. (It’s still icky.) Fish get tapeworms too, after eating marine invertebrates carrying various kinds of tapeworm larvae. The question is, how did a parasitic worm found in fish end up in amber? Occasionally there is rare amber found that fell into water and trapped water organisms, but this particular amber wasn’t associated with water. Other items found in the same piece of amber included sand grains, tiny hairlike structures found on some ferns, and the nymph of a scale insect. The team suggests that the tree where the amber came from grew near a beach and that a dead shark washed ashore. While scavengers were picking through the carcass, a piece of worm somehow got separated from the body and ended up in a tree. Possibly a scavenger grabbed a big yummy mouthful of rotting shark guts and either climbed or flew up into a tree to eat it, and part of the worm fell out and landed in a blob of amber. Because tapeworms are endoparasites, meaning they live inside their hosts, and because they’re soft-bodied and fragile, it’s very rare that one is preserved. Pretty much the only other preserved tapeworm specimen we have isn’t a tapeworm itself but some eggs found in fossilized shark dung, dated to 270 million year ago. Scientists aren’t even completely sure the eggs are from a flatworm since they’re not that well preserved. So it’s fantastic that this particular specimen was so well preserved, and that it made its way into the hands of scientists! Thanks for your support, and thanks for listening!