Lateral Line Organs

LATERAL LINE ORGANS, sensory organs located in the trunk of animals. In invertebrate animals, lateral line organs are called sensory organs that perceive water vibrations (for example, in the trunk of annelid worms - Capitellidae), as well as chemical sense organs in mollusks (Diotocardiae), located on their foot. In vertebrates, lateral line organs are called the organs of the lateral line or organs of the sixth sense (Leuckart), found only in aquatic vertebrates (cyclostomes, fish, aquatic amphibians, and amphibian larvae). Structurally, they belong to the type of sensory papillae, where the sensory (perceiving) cells are embedded in the surrounding supporting cells. The position of lateral line organs varies: in some, they lie freely in the skin or are slightly immersed in the skin (cyclostomes, some bony fishes, amphibians); in others, they are in open grooves (sharks, rays); in most bony fishes, they lie in channels filled with mucus, above the scales (or piercing through the scales and cranial bones). Among the modifications in sharks are the sacs of Savie and Lorenzinian ampullae. Lateral line organs are most typically arranged in fish as a lateral line on the trunk (1-2 rows); they are innervated by the vagus nerve (n. vagus); in the head, however, lateral line organs form a series of channels (supraorbital, infraorbital, occipital, hyomandibular), innervated by the facial nerve (n. facialis). Lateral line organs serve to perceive irritation caused by water currents, i.e., mass oscillations of the aquatic medium of moderate frequency (about 6 per second). Genetically, the origin of hearing organs, which perceive oscillations of higher frequency, is connected with the lateral line organs.