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Diptera setae are bristles present throughout the body and function as mechanoreceptors. Crustaceans have mechano- and chemosensory setae. [3] Setae are especially present on the mouthparts of crustaceans [3] and can also be found on grooming limbs. [4] In some cases, setae are modified into scale like structures. [4]
The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon . [1] [2] Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. They are, from head to tail:
Functions may variously include sensing touch, air motion, heat, vibration (sound), and especially smell or taste. [1] [2] Antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate. [2] Larval arthropods have antennae that differ from those of the adult.
The labrum is a flat extension of the head (below the clypeus), covering the mandibles. Unlike other mouthparts, the labrum is a single, fused plate (though it originally was—and embryonically is—two structures). It is the upper-most of the mouthparts and located on the midline.
The median part of the lower head, or face, often bears in its lower corners a pair (or a few pairs) of large seta (bristles) called 'vibrissae' and sometimes several or even a complete series along a ridge extending upward from the vibrissae. The latter setae are in Russian texts also called vibrissal bristles, not facial bristles.
In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch and vibration sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. [33]
Lobster anatomy includes two main body parts: the cephalothorax and the abdomen. The cephalothorax fuses the head and the thorax, both of which are covered by a chitinous carapace. The lobster's head bears antennae, antennules, mandibles, the first and second maxillae. The head also bears the (usually stalked) compound eyes. Because lobsters ...
Cephalization is a characteristic feature of the bilaterians, a large group containing the majority of animal phyla. [3] These have the ability to move, using muscles, and a body plan with a front end that encounters stimuli first as the animal moves forwards, and accordingly has evolved to contain many of the body's sense organs, able to detect light, chemicals, and gravity.