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Lecture

Arthropoda


Department
Biology
Course Code
BIOL 2030
Professor
Scott Kelly

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Arthropoda
Abdomen
The posterior part of the body, behind the head and thoracic regions
Arachnida
Class of mainly terrestrial, carniverious arthropods, included in the subphylum
Chelicerata, comprising spiders (order Araneae), scorpions (Scorpiones), mites and
ticks (Acari), false scorpions (Pseudoscorpiones), palpigrades, solifugids, and
harvestmen. They have a body usually divided itno a prosoma of eight fused segments
and a posterior opisthoma of 13 fused segments. The prosoma is not differentiated
into a head and thorax and bears the clawed and prehensile chelicerae, the pedipalps,
and four pairs of walking legs
Arthropods
Very large phylum of segmented invertebrate animals with heads, jointed
appendages (fellers, mouthparts, and legs), and a thickened chitonous cuticle forming
an exoskeleton. The main body cavity is a haemocoel. The phylum is generally divided
into several different groups, most commonly the Chelicerata, Atelocerata, Crustacea,
and the extinct Trilobita. In this classification, the Chelicerata inclues the spiders,
ticks, mites, scorpions, pycnogonids, horseshoe crabs, and the extinct eurypterids, the
Atelocerata (sometimes known as the Uniramia) includes the insects and myriapods
(centipedes and millipedes), and the Crustacea includes the crustaceans (crabs,
shrimps, barnacles, etc.). The velvet worms (Onychophora) are sometimes placed in
separate phylum
Articular membrane
A flexible region of the cuticle between sclerotized areas of the exoskeleton of an
arthropod; functions as a joint
Branchiopoda
The water fleas, brine shrimps, and their allies, a subclass mainly freshwater
crustaceans whose carapace, if present, forms a dorsal shield or bivalve shell, and
which have broad lobed trunk appendages fringed with hairs
Chelicerata
A class of subphylum of arthropods with a body generally in two parts, a prosoma
bearing the paired chelicerae (poison jaws) and sensory pedipalps, and a posterior
opisthsoma bearing usually four pairs of walking legs. The Chelicerata include the
arachnids (spiders ticks, mites, scorpions), pycnogonids (sea spiders), horseshoe crabs
and the extinct eurypterids
Chilopoda
A class of arthropods comprising the centipedes, which have numerous and similar
body segments each with one pair of walking legs, except the first segment which
bears a pair of poison claws. Considered as a subclass or order of class Myriapoda in
some classifications
Crustacea
Subphylum of arthropods, considered as a class in older classifications. They are
mainly aquatic, gill-breathing animals, such as crabs, lobsters, and shrimps. The body
is divided into a head bearing five pairs of appendages (two pairs of pre-oral sensory
ffeelers and three pairs of post-oral feeding appendages) and a trunk and abdomen
bearing a variable number of often biramous appendages which serve as walking legs
and gills. Crustacea often have a hard carapace/shell
Cuticle
An outer protective layer of material, of various composition, produced by the
epidermal cells, that covers the body of many invertebrates
Diplopoda
A class of arthropods commonly called millipedes, having numerous similar apparent
segments each in fact made up of two segments and therefore bearing two pairs of
legs. In some classifications, it is considered as a subclass or order of class Myriapoda
Epicuticle
Outer waxy layer of the exoskeleton of arthropods

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Exocuticle
The main layer of the cuticle of arthropods, which in crustaceans often contains
calcium salts
Exoskeleton
A hard supporting structure secreted by and external to the epidermis, such as the
calcareous exoskeletons of some sponges and the chitinous exoskeleton of arthropods
Extrinsic muscles
Muscles not entirely within the part or organ on which they act
Haemocoel
Blood-filled cavity consisting of spaces between organs, which is the main body cavity
in molluscs
Haemolymph
Fluid in the coelom of some invertebrates, regarded as equivalent to the blood and
lymph of vetebrates
Hexapoda
Subphylum containing insecta
Insecta
Very large class of arthropods, found as fossils from the Devonian onwards,
containing some three quarters of all known extant species of animal. The insects
include flies, bees, and wasps, andts, butterflies, and moths, beetles, dragonflies,
grasshoppers, and crickets, and many other orders. The segmented body is divided
into distinct head, thorax, and abdomen. The head bears on epair of antennae and
paired mouthparts, and the thorax bears three pairs of walking legs and usually one
or two pairs of wings. Other types of appendage may be present on the abdomen. The
life history usuallyu includes metamorphosis
Intrinsic muscles
Inner muscles of a part or organ
Malacostraca
A subclass of crustaceans containing the crabs, lobsters, crayfish, shrimps, and
woodlice, all of which have some form of hard carapace covering part of the body
Maxillopoda
Class of crustaceans including barnacles, copepods, and a number of related animals
Merostomata
Class of aquatic arthropods, the horseshoe crabs, which breathe by gills and have
chelicerae (claws) and walking legs on the prosoma, and an opisthosoma with some
segments lacking appendages
Metamorphosis
Transformation of one structure into another, most commonly referring to a radical
change in form and structure, as in caterpillar turning into a butterfly
Myriapoda
Centipedes and millipedes and their relatives, terrestrial arthropods characterized by
possession of a distinct head with a pair of antennae followed by numerous similar
segments each bearing legs
Ostia
Pores in the epidermis
Procuticle
The colourless cuticle of insects, composed of protein and chitin, before differentiation
into endocuticle and exocuticle
Pycnogonida
Class of chelicerate marine arthropods commonly known as sea spiders. They have a
slong slender body consisting of an anterior cephalon, a trunk with four pairs of long
walking legs, and a short segmented abdomen. Some species bear chelicerae and
feelers, others have neither
Sclerotization
Process of hardening and darkening of a new exoskeleton occurring in insects after
moulting
Sinus
Cavity, depression, recess, or dilatation
Spiracle
Hole in the sides of thoracic and abdominal segments of insects, and of myriapods,
through which the tracheal respiratory system connects with the exterior, and which
can be opened and closed
Sternotergal muscles
Taenia
Band, as of nerve or muscle
Tagmatization
The specialization of groups of body segments ot form different functional regions of
the body, as in arthropods

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Tergal
Dorsal part of typical arthropod segment
Thorax
Region behind the head, specifically first three segments behind head bearing the
wings in insects
Trachea
One of the air-filled tubules of the respiratory system, which ones to the exterior
through openings (spiracles) in the sides of thorax and abdomen
Tracheoles
Fine branch of the tracheal or respiratory system in insects and other arthropods,
directly supplying the tissues
Trilobita
Fossil group of extinct marine arthropods
Endocuticle
Innermost layer of the cuticle (exoskeleton) of arthropods
Arthropoda ~75% of animal species described (1.1M spp) 5 Subphyla
Only 4 subphyla alive, mostly class INSECTA (subphylum Hexapoda)
Each phyla various degrees of tagmatization (segments merging together) divergent body
plans
Trilobita 500 MYA, though not the ancesotor
Living Phyla
Chelicerata head & thorax merged
cephalothorax
Merostomata (horseshoe crabs) 200-250mya, blood used for endotoxicity testing (lysed
amoebocytes)
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