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(1) The narrowed anterior part of the body of invertebrates that performs a sensory function (in some turbellarians) or serves to gather food particles (in echiurids). In priapulids and sipunculids the proboscis retracts into the body. The term “proboscis” is also used to designate the sharply differentiated anterior section of Enteropneusta that serves for digging in the bottom.
(2) A special movable anterior organ in nemertinoids and some turbellarians that is used to capture prey. The proboscis is especially well developed in nemertinoids.
(3) A tubelike organ of attachment in parasitic worms, for example, thorny-headed worms and tapeworms. The proboscis is armed with hooks and is often retractile.
(4) The externally protruding tubular pharynx of some annelid worms, for example, polychaetes and leeches.
(5) In certain arthropods, mouth apparatus in the form of an elongate tube adapted for sucking liquid food. The proboscis may be a sucking organ (as in trichopterons, lepidopterons, hymenopterons, and some dipterons) or a stinging and sucking organ capable of piercing animal or plant integuments (as in ticks, Homoptera, hemipterons, thrips, lice, fleas, and certain dipterons).
A. V. IVANOV
in certain reptiles (soft river tortoises) and mammals (most insectivores, tapirs, male elephant seals, elephants) the movable elongate nasal part of the snout with nostrils at its tip. The proboscis usually performs respiratory, olfactory, and tactile functions. Its degree of mobility and development varies in different animals. It is especially well developed in elephants, where it is formed by the concrescence of the elongated nose and the upper lip. The tip of the elephant’s proboscis, or trunk, is equipped with a movable fingerlike projection, which enables the animal to pick up even very small objects from the ground. The trunk serves to grasp food and to touch and hold objects. Water is sucked up into the trunk and then discharged into the mouth.
In certain invertebrates the modified, usually retractile, anterior part of the body or an outgrowth of it is also called a proboscis.