Mouthparts

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Mouthparts

The mouthparts of arthropod

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
s have evolved

Evolution

In biology, evolution is change in the heritability trait of a population of organisms from one generation to the next. These changes are caused by a combination of three main processes: variation, reproduction, and selection....
into a number of forms, each adapted

Adaptation

Adaptation is the process, which takes place under natural selection, whereby an organism becomes better suited to its habitat. Also, the term may refer to some characteristic which stands out as being especially significant in the organism's survival....
to a different style or mode of feeding. Most mouthparts represent modified, paired appendage

Appendage

An appendage in the broadest sense is an additional or subsidiary part existing on, or added to, something which can generally still function if the appendage has never existed or is later provided or grown, or will still perform a primary function if the appendage is removed....
s, which in ancestral forms would have appeared more like legs than mouthparts. In general, arthropods have mouthparts for cutting and chewing, piercing and sucking, siphoning, and filtering. This article outlines the basic elements of four arthropod groups: insects, myriapods, crustaceans and chelicerates.

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The mouthparts of arthropod

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
s have evolved

Evolution

Adaptation

Appendage

Arthropod

Arthropods are animals belonging to the Scientific classification Arthropoda , and include the insects, arachnids, crustaceans, and others....
of the other arthropods discussed here.

Insects

Insect mouthparts

Insects exhibit a range of mouthparts, adapted to particular modes of feeding. The earliest insects had chewing mouthparts. Specialisation has mostly been for piercing and sucking, although a range of specialisations exist, as these modes of feeding have evolved a number of times , however female mosquitoes feed on animal blood whereas ap...
exhibit a range of forms. The earliest insect

Insect

Insects are the biggest class of arthropods and the only ones with wings. They are the most diverse group of animals on the planet. They are most diverse at the equator and their diversity declines toward the poles....
s had chewing mouthparts. Specialisation includes mouthparts modified for siphoning, piercing, sucking and sponging. These modifications have evolved a number of times. For example, mosquitoes (which are flies) and aphids (which are bugs) both pierce and suck, however female mosquitoes feed on animal blood whereas aphids feed on plant fluids. This section provides an overview of the individual mouthparts of chewing insects.

Labrum

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. It serves to hold food in place during chewing by the mandibles and thus can simply be described as an upper lip.

Mandible

Chewing insects have two mandibles, one on each side of the head. They are typically the largest mouthpart of chewing insects, being used to masticate (cut, tear, crush, chew) food items. They open outwards (to the sides of the head) and come together medially.

Maxilla

Paired maxillae cut food and manipulate it during mastication. Maxillae can have hairs and “teeth” along their inner margins. At the outer margin, the galea is a cupped or scoop-like structure, which sits over the outer edge of the labium. They also have palps, which are used to sense the characteristics of potential foods.

Labium

The labium is a single structure, although it is formed from two fused secondary maxillae. It can be described as the floor of the mouth. With the maxillae, it assists manipulation of food during mastication.

Hypopharynx

The hypopharynx is a somewhat globular structure, arising from the base of the labium. It assists swallowing.

Myriapods

Myriapods comprise four classes

Class (biology)

A class is the taxonomic rank in the biological classification of organisms in biology below phylum and above Order .The orders of taxonomy are life, Domain , kingdom , phylum, class , order , family , genus, and species....
of arthropod, each with a similar morphology

Morphology (biology)

The term morphology in biology refers to form, structure and configuration of an organism. This includes aspects of the outward appearance as well as the form and structure of the internal parts like bones and organs....
: Class Chilopoda (centipedes); Class Diplopoda (millipedes); Class Pauropoda

Pauropoda

Pauropods are small, pale, centipede-like arthropods. They form the order Pauropodina, belonging to the monotypic class Pauropoda....
; and Class Symphyla

Symphyla

Symphylans, also known as garden centipedes or glasshouse symphylans, are soil-dwelling arthropods of the class Symphyla in the subphylum Myriapoda....
. Myriapod mouthparts are similar to those of chewing insects, although there is some variation between the myriapod classes. A labrum is present but sometimes is not obvious and forms an upper lip, often in association with an epistome. The labium is formed by first or second maxillae. The preoral cavity so-formed contains paired mandibles and a hypopharynx.

Forcipules

Centipede

For information about the old arcade game, see Centipede .Centipedes are arthropods belonging to the class Chilopoda and the Subphylum Myriapoda....
s, in addition to their mouthparts, possess a pair of "poison claws" or forcipules. These, like the maxillipeds of crustaceans, are modified legs and not true mouthparts. 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 poison prey.

Crustaceans

Crustacean

Crustaceans are a large group of arthropods, comprising almost 52,000 described species , and are usually treated as a subphylum . They include various familiar animals, such as crabs, lobsters, crayfish, shrimp, krill and barnacles....
, with various feeding modes supported by a range of adaptions to the mouthparts. In general, however, crustaceans possess paired mandibles with opposing biting and grinding surfaces. The mandibles are followed by paired first and second maxillae. Both the mandibles and the maxillae have been variously modified in different crustacean groups for filter feeding with the use of setae.

Maxillipeds

Up to the first three pairs of legs are modified to maxillipeds, which assist manipulation of food items, by passing food forward to the mandibles for chewing or to the maxillae for cutting into smaller pieces.

Setae

Filter feeding crustaceans have setae on modified appendages that act as filters. Filter feeding may have developed in association with swimming, with early morphological adaptions occurring on the appendages of the body trunk. Subsequent adaptions appear to have favoured forward filtering appendages. Filtering appendages generate water currents that bring food items into reach for collection by setae. Other setae may be used to brush the filtering setae clean, and yet other setae may transport food items to the mouth.

Cirri

Barnacles have thoracic appendages modified for feeding, the cirri, which filter suspended food particles from water currents and pass the food to the mouth.

Chelicerates

Chelicerates comprise four class

Class (biology)

Xiphosura

Xiphosura is an order of marine Chelicerata which includes a large number of extinct lineages and only four recent species in the family Limulidae, which include the horseshoe crabs....
(horseshoe crabs); Class Eurypterida (the extinct eurypterids); Class Arachnida (spider

Spider

Spiders are air-breathing chelicerate arthropods that have eight legs, and chelicerae modified into fangs that inject venom. In their bodies the usual arthropod segments are fused into two Tagma , the cephalothorax and abdomen, joined by a small, cylindrical pedicel....
s, scorpion

Scorpion

Scorpions are any arachnid of the order Scorpionida. They are members of the order Scorpiones within the class Arachnida. There are about 2,000 species of scorpions, found widely distributed south of about Latitude, except New Zealand and Antarctica....
s, tick

Tick

Tick is the common name for the small arachnids in superfamily Ixodoidea that, along with other mites, constitute the Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and occasionally reptiles and amphibians....
s and mite

Mite

Mites, along with ticks, belong to the subclass Acarina and the class Arachnida. Mites are among the most diverse and successful of all the invertebrate groups....
)s; and Class Pycnogonida (sea spiders). Chelicerates are in part defined by possessing chelicerate appendages, although crustaceans also possess chelate appendages. Chelicerates are more easily distinguished from other arthropods in lacking antennae

Antenna (biology)

Antennae are paired appendages connected to the front-most morphogenesis of arthropods. In crustaceans, they are biramous and present on the first two segments of the head, with the smaller pair known as antennules....
.

Chelicerae

The Chelicerae are mouth parts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have....
are chelate appendages that are used to grasp food. For example, in horseshoe crabs they are like pincers, where-as in spiders they are hollow and contain (or are connected to) venom glands, and are used to inject venom to disable prey prior to feeding. In some spiders, the chelicerae have teeth, which are used to macerate prey items to assist digestion by secreted enzymes. Those spiders without toothed chelicerae inject digestive enzymes directly into their prey. Mites and ticks have a range of chelicerae. Carnivores have chelicerae that tear and crush prey, where-as herbivores can have chelicerae that are modified for piercing and sucking (as do parasitic species). In sea spiders, the chelicerae (also known as chelifores) are short and chelate, and are positioned either side of the base of the proboscis or sometimes vestigial or absent.

Pedipalps

In addition to chelicerae, arachnids also possess a pair of pedipalp

Pedipalp

Pedipalps, are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with Mandible_ in Crustacea and insects, although more recent studies suggest they are probably homologous with the crustacean second antennae....
s. In scorpions, the pedipalps are large and chelate (of the scissor type at Figure 4). They are used to capture and hold prey items for stinging before the chelicerae tear the prey into items for digestion. In spiders, the pedipalps of males are modified and function as secondary sex organs (transmission of sperm to the female). The pedipalps of mites and ticks vary depending on the species’ feeding mode. They are segmented and may be leg-like or chelate, like a second pair of chelicerae.

Proboscis

Sea spiders possess a tubular proboscis forward from the body trunk, at the end of which is the opening to the mouth. In those species that lack chelifores and palps, the proboscis is well developed and more mobile and flexible. In such cases it can be equipped with sensory bristles and strong rasping ridges around the mouth.