Bugs: The Land-Dwelling Relatives of Shrimp

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A recent study suggests that insects branched out from crustaceans on the tree of life

Riley Black – Science Correspondent

April 9, 2025 8:00 a.m.

A species of remipede known from the Caicos Islands. The photograph was taken by a member of a multinational team looking for rare species. Remipedes are crustaceans that are close relatives to insects.

It’s easy to see how shrimp might remind us of insects. Both groups feature exoskeletons, jointed legs, and compound eyes, leading to the occasional playful comparison. Terms like “mudbugs” for crawfish illustrate this resemblance, while the meme “shrimps is bugs” humorously reinforces it. Yet, this popular notion is misleading; insects qualify as a specialized form of crustacean rather than mere bugs.

Within biology, the discipline of systematics is crucial for categorizing life forms. Through extensive analysis, both living and extinct species are evaluated to continually refine our understanding of the evolutionary tree. Recent analytical advancements have provoked significant shifts in classification, impacting entire branches of the tree. For instance, research has established that birds are classified as dinosaurs, whales are pinpointed as artiodactyls (hooved mammals), and a pivotal 2023 study identified insects as members of the pancrustacea group alongside shrimp and crabs.

The linkage between insects and crustaceans emerged after nearly a century of scientific exploration. Paleontologist Joanna Wolfe from Harvard University, a contributor to the 2023 study, highlighted how previous observations uncovered shared features in the eyes and nervous systems of certain insects and crustaceans. Initial skepticism about whether these similarities indicated a close relationship lingered, attributed to the possibility of convergent evolution where unrelated species evolve similar traits independently.

In 2013, Wolfe and her team discovered that insects are the nearest evolutionary kin to remipedes, a unique crustacean species residing in underwater caves and noted for their venom. Previously viewed as oddities, remipedes emerged as the closest relatives to familiar insects like flies and bees. Wolfe’s surprise at these findings later gave way to robust evidence reinforcing the evolutionary connection. The 2023 genetic analysis placed insects among a wider crustacean group called allotriocarida, which encompasses remipedes and other peculiar crustaceans. This revelation reframes insects similarly to how bats relate to mammals; they belong to a broader classification despite their apparent differences.

Redefining relationships within the tree of life transcends mere taxonomy. “Systematics provide a framework to navigate the complexity of life,” explains Advait Jukar, a paleontologist at the Smithsonian National Museum of Natural History. “By regrouping species, we gain insight into patterns of diversification influenced by various environmental conditions.”

The recognition of birds as dinosaurs had far-reaching implications beyond reordering their evolutionary hierarchy. This connection revealed that traits traditionally associated with birds, such as feathers and specialized respiratory systems, were common across a range of dinosaur species. Following this reassessment, numerous feathered dinosaur fossils exhibiting these features were discovered, shedding light on the survival advantages that enabled certain bird lineages to endure the mass extinction event 66 million years ago.

Additionally, the classification of whales as artiodactyls prompted a transformative approach among paleontologists in understanding cetacean evolution. Once thought to have descended from carnivores like mesonychids, emerging genetic evidence suggested a closer affinity with hippos and related mammals. The 2001 discovery of specific ankle bones exhibited characteristics unique to artiodactyls further solidified this connection, leading researchers to reevaluate the ancestry of whales and trace their origins back to small, deer-like creatures.

Regarding insects, the acknowledgment of their relationship with remipedes prompts a reassessment of their origins. Wolfe emphasizes that this connection indicates insects may not stem from a terrestrial ancestor as previously thought, but rather from marine crustaceans. While this does not confirm that remipedes are direct ancestors of insects, it does inform biologists about potential evolutionary pathways and lays the groundwork for future research. “There’s a complicated history and still pieces missing,” Wolfe reflects, yet the new understanding offers a clearer framework for discovery. In essence, as insects are repositioned within the crustacean lineage, the curiosity about their evolutionary journey can deepen.

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