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The three basic segments of the typical insect antenna are the scape or scapus (base), the pedicel or pedicellus (stem), and finally the flagellum, which often comprises many units known as flagellomeres. [10] The pedicel (the second segment) contains the Johnston's organ which is a collection of sensory cells. [11]
A tripartite structure is recorded from near the antennae, consisting of elevated walls arranged in a semicircle (likely to enlarge the surface for an excretory organ as in modern crustaceans), a pore representing an opening of the “antennal gland” (the purpose of which is unknown) and a sickle-shaped furrow surrounding this pore.
Coxal gland and its components. The coxal gland is a gland found in some arthropods, for collecting and excreting urine. They are found in all arachnids (with the exception of some Acari), and in other chelicerates, such as horseshoe crabs. [1] The coxal gland is thought to be homologous with the antennal gland of crustaceans.
In Crustacea, the saccate metanephridia are associated with the antennae and form the antennal gland. In freshwater crustacea, the saccate metanephridia are especially large due to their role in osmoregulation; crustacea must remove large amounts of water from the tissues, as the cells are hypertonic to the surrounding water.
A notable number of species have developed special glands that produce chemicals for deterring predators (see Defense and predation). The Ground beetle's (of Carabidae) defensive glands, located at the posterior, produce a variety of hydrocarbons, aldehydes, phenols, quinones, esters, and acids released from an opening at the end of the abdomen.
A shed carapace of a lady crab, part of the hard exoskeleton Body structure of a typical crustacean – krill. The body of a crustacean is composed of segments, which are grouped into three regions: the cephalon or head, [5] the pereon or thorax, [6] and the pleon or abdomen. [7]
These, like the maxillipeds of crustaceans, are modified legs and not true mouthparts. [2] The forcipules arise from the first body segment, curving forward and to the midline. The tip is a pointed fang, which has an opening from a venom gland. The forcipules are used to capture and envenomate prey.
Its innervation from the rear of the brain has suggested to some workers that, if an appendage, it is the appendage of the tritocerebral segment; a point disputed by others who argue that the presence of a well-developed appendage in at least crustaceans in this segment (i.e., the second antenna, corresponding to the intercalary segment of ...