Invertebrates Other than Insects

Abstract Terrestrial and aquatic invertebrates are the most numerous and ecologically critical animals on the planet. They have long been studied and are indeed model systems for a variety of research fields, yet invertebrate use of sound, including hearing, auditory anatomy, sound production mechanisms, has historically been overlooked (compared to many of their vertebrate counterparts). However, there is an emerging interest and recognition of their vibroacoustic ecology with respect to both basic research and the impacts of increasing anthropogenic stressors. Here we provide an overview of invertebrate bioacoustics (and where relevant, biotremology), excluding insects. In the marine environment, studies often address crustaceans (i.e., aquatic crabs, lobsters, crayfish, shrimp, krill, and barnacles), which are probably the best-known invertebrates (other than insects) for bioacoustic abilities. In terrestrial habitats, our knowledge of sound and substrate-borne production and detection tends to focus on terrestrial crabs, scorpions, and spiders. Sensory structures and signals produced may be as diverse as this group of animals but there are some general trends. Signals produced by invertebrates are often generated through some type of stridulation (i.e., rubbing two hard body parts together), by scraping hard body parts against a substrate, opening and closing a claw, or vibrating the abdomen. In general, non-insect invertebrates have low-frequency hearing and they may receive sounds and vibrations using receptors on the body surface, internal statocyst receptors, chordotonal organs on the appendages, or abdominal sense organs. Terrestrial crabs detect sounds and vibrations using the Barth’s myochordontal organ on each walking leg. Spiders use slit sensilla and a variety of sensory hairs on their body to detect vibrations. Like their vertebrate counterparts, invertebrates use sound for various purposes including to startle prey, recruit conspecifics to a feeding site (e.g., lobsters), find suitable settlement habitat (marine crabs, oysters, and corals), attract females, defend a burrow, express aggression (terrestrial crabs), and detect and identify captured prey (spiders). While vibroacoustic sensitivity may not be as well-developed as in some vertebrates, invertebrates are not immune to the effects of anthropogenic noise. Noise has been shown to impact communication, metamorphosis, and feeding; it may further cause anatomical damage in an array of taxa. Overall, sensory biology and acoustic ecology are nascent fields of knowledge for invertebrates, yet for animals often considered deaf, they show a remarkable affinity for detecting and using sounds and substrate-borne vibrations.