Morphological diversity of mantis shrimp larvae in deep time

Larvae of mantis shrimps (Stomatopoda) exhibit a great morphological diversity, reflecting their numerous ecological roles in the plankton. From hatching from their eggs to their adult stage they develop through numerous stages, each separated by a moult. Due to their long time spent in the plankton, the larvae reach relatively large sizes, up to several tens of millimetres. The larvae play an important role as active predators of smaller plankton animals, but also as prey of immatures of large predatory fishes, such as tuna, therefore occupying a crucial role in the marine food web, possibly even having economical significance. Their strongly pronounced compound eyes and strongly modified major appendages enable them to efficiently catch prey in the pelagic zone, especially smaller soft-skinned organisms, such as small-sized adults or larvae of other crustaceans. As larvae they drift in the planktic realm of the ocean, before continuing in a more benthic existence after metamorphosing. Their presence in the fossil record has been demonstrated by fossil finds since the Jurassic. Still, such larvae are still rare as fossils, while adults and post-metamorphic immatures are much more common and also reach further back in time, into the Carboniferous. We present here a quantitative morphological comparison of feeding structures of mantis shrimp larvae over time, exploring in how far their ecological roles might have changed or been retained through time.