Cuticle
Consists of outer, relatively think epicuticle and an inner, thicker procuticle, found in most protostomes
Class Diplopoda
-Millipedes -Cylindrical bodies with 25-100 segments -Four thoracic segmented bear one pair of legs -Abdominal segments bear 2 pairs of legs -typically herbivorous
Exoskeleton
hardened cuticle that is secreted by underlying epidermis, must be molted (shed) in order to grow, contains chitin proteins
Appendages
uniramous (one tip legs) Biramous (multiple tip legs) Chelicerae (pinchers by mouth) Mandibles (by mouth)
Subphylum Crustacea
-2 pairs of antennae a pair of mandibles and -2 pairs of maxillae one pair of appendages on each segment -All appendages except perhaps first antennae care biramous
Basal protopod, an outer branch called on exopod and an inner branch called endopod
Crustacean Segmentation
-Primitive Crustaceans may have up to 60 segments, derived crustaceans have fewer -Tagmata are usually head, thorax and abdomen -Not homologous across taxa -In most, one or more thoracic segments are fused with the head as a cephalothorax -Dorsal covering is the carapace
May cover most of body or just cephalothorax
Crustacean Appendages
Have wide variety of walking legs, mouthparts, swimmerets from modification of the basic biramous appendages -some have lost 1 branch and are uniramous Crayfish
1st 3 pairs of thoracic appendages are celled maxillipeds -5 pairs walking legs
1st pair of swimmerets in male called monopods used in copulation -Uropods are last pairs of appendages used for backwards movements and protection for eggs or young on swimmerets
Suspension feeders
generate water currents in order to feed
Predators
hunt for their food, consume larvae, worms, crustaceans, snails, and fishes
Scavengers
eat dead animals and plant matter, many have a two-part stomach
crustacean life cycle
Most crustaceans have separate sexes Most crustaceans brood eggs in brood chambers, in eggs sacs attached to abdomen, or attached to abdominal appendages Crayfishes develop directly without a larval form Most crustaceans have a larva unlike the adult in form and undergo metamorphosis Nauplius is a common larval form with unsegmented body, frontal eye, 3 pair of appendages
Branchiopoda
3 orders are recognized -Anostraca: includes fairy shrimp and brine shrimp -Notostraca: includes tadpole shrimp -Diplostraca: Includes water flea and clam shrimp
Brachiopod Anatomy
Flattened leaf-like legs serve as respiratory organs, assist in suspension feeding, and except for cladocerans, locomotion Most are freshwater Important component of freshwater zooplankton
Subclass Copepoda
roup of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic, some are benthic, a number of species have parasitic phases
Epicuticle
outer most layer of arthropods, made of protein and often lipids
Procuticle
Divided into exocuticle (secreted before a molt) and endocuticle (secreted after molting). Both layers contains chitin bound with proteins
Ecdysis
The process of molting ends in the shedding of skin
molting
necessary for an arthropod to increase in size, since exoskeleton does not grow
Segmentation
Typically each arthropod segment has a pair of jointed appendages Arrangement is often modified with both segments and appendages specialized for a range of functions Each section of an appendage functions as a hollow tube moved by muscles, which insert on the inside
Class Pycnogonida
-sea spiders -4 pairs of walking legs -suctorial proboscis -much reduced abdomen -male use ovigers (pair of legs) to carry egg masses -common in the waters
Cephalothorax and abdomen are joined by?
Thin Pedicel
Class Arachnida
-over 100,000 species described -spiders, scorpion, whip scorpions, ticks, mites, harvestmen, etc -cephalothorax and abdomen
Order Araneae
-Spiders -All predaceous -chelicerae function as fangs -web spinning to trap pray -others are cryptic or stalk prey
Trilobite Fossil
-extinct for 250 million -Abundant during Cambrian and Ordovician period -Trilobed shaped body, pair of longitudinal grooves Probably bottom dwellers and scavengers
Class merostomata
Horseshoe Crab- looks like a crab but it closely related to spiders
ancient marine group -carapace, abdomen, telson -their blue blood is harvested and used to test medicine
Spiracles
opening on the outside of the arthropods that connects to the tracheae for breathing
Air piped directly to cells
Most land arthropods have a highly efficient tracheal system of air tubes, which deliver oxygen directly to tissues and cells
Tracheae are not present in aquatic arthropods, which breathe mainly by gills
Pros and Cons of Arthropods
Pros: Important source of products Cons: Cause many diseases and economic losses
Order scorpionida
scorpions, females carry young on their back
Order Acari
ticks and mites that like to eat dead skin cells, common allergy to humans
Lyme disease
occurs when bitten by Ixodes pacificus (blacklegged tick) who are carriers of this disease, can be carried by any in the genus Ixodes Opossums are vital in tick control
Class thecostraca
barnacles, very long penis that can inseminate females, slows ships
Order isopoda
terrestrial crustaceans, decomposers, rollie pollies, some are parasitic
Order euphausiacea
krill, major component of animals diets
Decapoda
crabs, have ten legs in total