A tongue, a muscular organ found on the floor of the mouth in most vertebrates, serves several functions including manipulating food for chewing and swallowing, tasting, and in some animals, even grooming or capturing prey. This organ is fundamental to how many creatures interact with their environment and process nutrients. However, many organisms thrive without this common anatomical feature, employing different strategies for survival and feeding.
Animals Without Tongues
Many creatures across various phyla have evolved to subsist without a traditional tongue. Sponges, belonging to the phylum Porifera, are among the simplest multicellular animals and entirely lack a tongue or any complex organ systems. Their bodies are porous, designed for a stationary existence in aquatic environments. Jellyfish, members of the phylum Cnidaria, also do not possess tongues, relying instead on their characteristic stinging tentacles.
Sea stars, commonly known as starfish, are echinoderms that lack a tongue. Sea urchins, also echinoderms and relatives of sea stars, do not have a tongue, despite having a complex chewing apparatus. Certain types of worms, such as earthworms and leeches, also lack a tongue in the conventional sense.
How They Feed
Animals without tongues have developed specialized and effective feeding mechanisms adapted to their specific lifestyles. Sponges are filter feeders, drawing water through tiny pores in their body walls. Specialized cells called choanocytes capture microscopic food particles, such as bacteria and other microorganisms, from the water. Jellyfish are carnivorous, utilizing their tentacles, armed with stinging cells (cnidocytes), to immobilize prey like plankton, crustaceans, and small fish. Once captured, their oral arms guide the food into their mouth, where digestion occurs.
Sea stars evert their stomach outside their body to digest prey. They use their tube feet to pry open the shells of mollusks like mussels and clams, then extend their cardiac stomach into the shell to release digestive enzymes, liquefying the prey before absorbing the nutrients. Sea urchins use a chewing apparatus called Aristotle’s lantern, composed of five hard, self-sharpening teeth. This structure allows them to scrape algae off rocks and grind other organic matter, with their mouth located on their underside.
Earthworms ingest soil as they burrow, extracting nutrients from decaying organic matter like leaves and roots. Their muscular pharynx helps pull food into their digestive system, where it is ground in a gizzard and nutrients are absorbed in the intestine. Leeches attach to hosts using suckers and use three sharp jaws to slice the skin. They then secrete an anticoagulant to prevent blood clotting, allowing them to feed on blood.
The Evolutionary Story
The absence of a tongue in these diverse animals reflects adaptation, as well as their unique ecological niches and evolutionary paths. For sessile filter feeders like sponges, a tongue is unnecessary; their entire body structure is optimized for drawing water and filtering food particles directly from their aquatic environment. Their ancient lineage suggests that complex feeding appendages like tongues did not evolve as a necessary component of their survival.
Jellyfish, with their radial symmetry and passive, stinging-tentacle feeding method, do not require a tongue to manipulate prey. Their simple body plan and reliance on water currents for movement and food delivery make a complex muscular organ redundant. Echinoderms such as sea stars and sea urchins evolved distinct digestive adaptations, like the eversible stomach or Aristotle’s lantern, which are effective for their predatory or herbivorous diets on the seafloor. These specialized structures fulfill the functions a tongue might otherwise provide, allowing them to process food efficiently in their marine habitats.
The subterranean lifestyle of earthworms, where they consume soil directly, and the parasitic or predatory habits of leeches, which involve piercing and sucking, led to the development of alternative feeding mechanisms that do not involve a tongue. These diverse adaptations highlight how evolution tailors organisms to their environments, leading to successful survival without structures common in many other animal groups.