Lemurs, the primates native exclusively to Madagascar, possess unique biological features that set them apart from their monkey and ape relatives. Among these features is the question of whether these animals have two tongues. The answer points to a highly specialized anatomical structure often visually mistaken for a secondary tongue. This unique adaptation is an example of how evolution shapes an animal’s body to meet the specific demands of its environment.
The Anatomical Reality: What is the Sublingua?
Lemurs, along with other strepsirrhine primates, do not have a second muscular tongue used for tasting or manipulating food. Instead, they feature a distinct structure located beneath the main tongue called the sublingua, which literally translates to “under-tongue.” This structure is a thin, less mobile, and more rigid flap of tissue, unlike the primary tongue used for eating and vocalization. The sublingua is supported by a stiff internal structure, often a cartilaginous rod, which gives it firmness and shape. It lacks taste buds, confirming its function is not sensory or related to digestion. The structure is often tipped with hardened, keratinized edges that can appear brush-like or serrated.
The Essential Role of the Sublingua in Grooming
The primary purpose of the sublingua is maintenance and hygiene, acting as a specialized oral cleaning tool. Its unique, rigid structure is perfectly adapted to work in conjunction with the lemur’s specialized lower teeth. The sublingua functions like a scraper, ensuring the entire oral grooming apparatus remains free of obstruction.
When a lemur grooms its fur, hair and debris inevitably become lodged between its lower front teeth. The sublingua moves with precision to dislodge and remove the trapped material from the dental structure. The keratinized, serrated tip is particularly effective at raking through the fine spaces between the teeth. This action is paramount for keeping the teeth clean and functional for continuous grooming activities.
The efficiency of this cleaning mechanism ensures that the lemur’s primary grooming tool remains sharp and ready for use. While the cleaning function is the most recognized role, its design is overwhelmingly suited for this maintenance function, making it an indispensable part of the lemur’s self-care routine.
Specialized Dental Structure: The Tooth Comb
The existence of the sublingua is directly linked to the presence of another specialized feature in lemurs: the tooth comb. This dental structure is an adaptation found in nearly all strepsirrhine primates, including lemurs and lorises. The tooth comb consists of a set of lower incisors and canine teeth that are elongated and project forward from the jaw at a sharp angle.
In most lemur species, this arrangement includes six teeth—four incisors and two canines—that are compressed and aligned closely together. They are positioned in a way that makes them highly effective for combing through fur, similar to the action of a human hair comb. The primary use of the tooth comb is not for biting or chewing food, but for personal and social grooming, removing parasites and keeping the coat clean.
The tooth comb’s fine, forward-facing arrangement is what necessitates the specialized cleaning action of the sublingua. Without the sublingua to clear the trapped fur and debris, the tooth comb would quickly become clogged and useless. This demonstrates a co-evolutionary relationship where one highly specialized anatomical feature exists solely to support the function of another.