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• Important Characteristics of Arthropods

  • They possess an exoskeleton
  • They have jointed appendages
  • Their body is segmented
  • They are bilaterally symmetrical
  • They possess an open circulatory system
• Tagmatization

  The segmentation of Arthropod bodies is different from that of Annelids in that they consist of subsections composed of fused segments referred to as tagmatization.

  • Metamerism: Localized body movements and body functions.
  • Tagmatization: You have a division of labor. Not all segments have the same set of organs.
  • Tagmata are the specific sections (i.e. Head, Thorax, Abdomen), which may vary from species to species.
  • The division-of-labor principle has even been assumed to be one of the major factors for the evolutionary success of this animal lineage.
• Chitinous Exoskeleton


  • Composed of the head, thorax, and abdomen
  • Unlike worms which use a hydrostatic skeleton to distribute the fluid pressure for it to move, arthropods have rigid structures which makes them harder to move
  • Their skin is their framework to move (like armor and muscles are able to control it)
  • This shell provides protection for the animals, and gives support for the attachment of the arthropod's muscles
  • Although arthropods grow, their exoskeletons do not grow with them. Instead, arthropods must go through the delicate process of shedding the old exoskeleton and expanding to a larger size before the new exoskeleton hardens.
• Ecdysis


  Molting (shedding or ecdysis) of the outer cuticular layer of the body is a process vital to arthropods, including insects and crustaceans. They have a cuticle layer. Epicuticle is waxy and lipid waste. Procuticle is made of chitin, fats, and proteins. Proteins in procuticle form cross-linkages (for sclerotization) which hardens the exoskeletons of newly molted cuticle of nearly all insects. If they want it to make harder, they impregnate themselves with Calcium Carbonate.
• Arthropods lack locomotory cilia, even in the larval stages, probably because of the presence of the exoskeleton.
• "Joint Foot"


  • They have jointed appendages
  • Taxonomy also relies on this characteristic
  • At the junction, or joints, between the plates and cylinders the exoskeleton is thin and flexible because it lacks the exocuticle and because it is folded
  • No cross linkages in appendages, but they are still covered with a cuticle
  • Arthropods appendages can be classified as uniramous and biramous. A uniramous limb comprises a single series of segments attached end-to-end. Biramous appendages are branched in two that come out in basal segment
  • Basic leg structure: coxa, trochanter, femur, tibia, and tarsus.
• There are also appendages (that are not legs), mainly used for eating, walking, sensory, swimming, etc. It can be present or not in different groups.
• Tarsal Haller's organ


  Presumed to function like the insect antennae in chemosensation but morphologically very different
• Advantage of Jointed Appendages


  • Appendages allow organisms, such as arthropods, to have greater flexibility and range in movement
  • Provides organisms with a greater capacity for locomotion, feeding, and for defending themselves from damage
• Hard outer layer


  • Provides protection, water retention, structural support (especially when exposed to land), and resistance to movement and balance
• Subphylum Mandibulata: Mandibles, Their 3rd head appendage are modified to form mandibles for processing food
• Superclass Myriapoda: Many feet, Recent taxonomy, Myriapods are more closely related to chelicerates and form their own clade Paradoxipoda, Appendages are uniramous
• Class Diplopoda (Millipedes)


  • Have 2 pair walking legs per segment, Slower moving, have more tubular bodies, and they are clean up crew, Found in garden, soil, They curl up when bothered to defend themselves, Many species have defense glands (called ozopores) which discharge a smelly and disgusting-tasting liquid
• Class Chilopoda (Centipedes)


  • Have 1 pair walking legs per segment, Flatter bodies, move faster and many of them are predatory, Cuticle is not really waxy, Usually at night or moist places (like bathroom) to not dry up, First pair of walking legs (maxillipeds) modified to subdue prey, Forcipules: modified walking legs
• Superclass Crustacea


  • 5 pairs of head appendages (2 pairs are antennae), Nauplius larvae, Biramous appendages, Chelipeds: Defense or securing the prey, Tagmata are more defined, Myriapods and insects are uniramous while crustaceans are biramous, Endopodites are closer to the middle
• Class Branchiopoda


  • "Gill foot" (epipodite as a respiratory structure), Water fleas - maintain ecological balance, filter healthy waterways and act as a food source for amphibians, insects and fish
• Class Copepoda


  • Oar foot, 6 Thoracic (1st fused to head) 5 abdominal segments, No gills, No abdominal appendages, No compound eyes, Prosome and urosome (fancy names for cephalothorax and abdomen) same tagmata
• Class Cirripedia


  • Hairy foot, Thoracic limbs 'cirri' (modified), Reduced head, No abdomen, Adapted to stick to surfaces, They are adapted to sedentary lifestyle (so if may predator, you're fucked up)
• Plates in Barnacles


  • The barnacle secretes the calcium-hard plates which totally encase them, Barnacles latch on massive stuff like ships and sometimes turtles, Can affect ship resistance and powering, Parasites (food sources for barnacles, nakikiride lang siya sa turtle tapos punta iba lugar din), Turtles loses its hydrodynamic shape, kailangan niya ng maraming energy para buhatin ung mabigat na barnacles attached, The barnacle has no gills — gases are exchanged through cirri (feathery appendages) and body walls, They utilize their modified legs, called cirri, to sweep tiny food particles from the water column and pass them to their mouth parts inside their protective plates
• Class Malacostraca


  • Soft shell, 8 thoracic + 6-7 abdominal segments + telson, With abdominal appendages (pleopoda), Uropod at the last ab. segment, They have abdominal appendages - pleopods, Appendages in posterior part are flattened - uropods, Thoracic appendages are called thoracopods (Types: chelipids, pereopods (depends on function))
• Order Amphipoda


  • Different foot, Sand hoppers, Laterally compressed bodies, 1st 2 thoracic appendages = gnathopods, Gnathopods - pair of pereopods
• Order Isopoda


  • Equal foot, Pill bugs/sow bugs, Often dorsoventrally flattened, Very small 1st pair of antennae 5 abdominal appendages used in respiration
• Order Stomatopoda


  • Mouth foot, Mantis shrimp, Raptorial 2nd Maxilliped, 2nd pair of appendages are raptorial (Do have strong punches, Smashers, spearers, Punchers and piercers)
• Order Decapoda


  • 10-foot pereopods, Lobsters, crabs, shrimp, 1-3 pairs have claws so they are chelipeds
• Importance of Crustaceans: Clean up crew, predator, prey and food
• Superclass Hexapoda (Insecta)


  • Largest and most diversified group under the phylum Arthropoda, Characterized as having three-body sections namely the head, thorax and abdomen, Head: commonly has a pair of antennae and a pair of compound eyes, three ocelli and a variable mouth apparatus adapted for the purposed of either chewing, sucking, piercing or sponging/lapping, Thorax: has a pair of walking legs per tagma, two pairs of wings attached to the metathorax, Abdomen: composed of 11 segments typically terminating with a pair of cerci, Integument: made up of overlapping plates composed of chitin and cuticle, Digestive: complete digestive system with a crop leading to the stomach, Circulatory: open type composed of a dorsally located tubular heart pumping colorless or green blood in the haemocoel, Respiratory: through the spiracles located on the sides of the abdomen and connects to the tracheal system, Excretory: via malphighian tubules forming uric acid, Nervous: composed of one brain and a ventrally fused nerve cord, Reproductive: dioecious with sexual reproduction culminating in internal fertilization, Habitat: found primarily in terrestrial ecosystems
• Defining Characteristics of Insects


  • 6 feet, Labium - The fusion of second pair maxillae, Have evolved in different variations depending on their type of diet, The position of the mouthparts can also vary across different insect groups: prognathous, hypognathous, opisthognathous, Insect wings usually come in pairs of two: front wings/forewings and hind wings
• Metamorphosis in Insects


  • Ametabolous: bigger version of younger self, Little or no metamorphosis, Hemimetabolous: bigger and slightly prettier version of yourself, Incomplete metamorphosis, Holometabolous: completely different from younger self, Complete metamorphosis, For the majority of insects, they will either have an incomplete (hemimetabolous) or complete metamorphosis, Hemimetabolous refers to incomplete metamorphosis where the nymph stage has an aquatic habitat whereas the adult form has a terrestrial habitat, Paurometabolous is the type of incomplete metamorphosis where the baby up to the adult form belongs to the same habitat (usually terrestrial)
• Order Zygentoma


  • Includes species from former order, Thysanura, Do not have wings, Have very long cerci and median caudal filament, Thysanura="bristletail", Development: Ametabolous, Lepisma sp. (Silverfish)
• Clade Palaeoptera


  • "Old wing", Hemimetabolous, Insects are not able to fold their wings neatly above their abdomen, Their wings can move independently, Most recognizable group: order Odonata
• Order Odonata


  • "toothed ones", They have strongly-toothed mandibles, Their wings have a "rectangular patch" called stigma, Anisoptera (dragonflies): Have broader hindwings than forewings, Cannot fold their wings, Some of the fastest fliers among the insects, Zygoptera (damselflies): Can fold their wings along the length of their body axis when at rest
• Clade Neoptera


  • "New wing", Can flex the wings
• Cerci


  Very long median caudal filament
• Lepisma sp.


  • Silverfish
• Taxonomic classification of Lepisma sp.


  • Kingdom: Animalia
  • Phylum: Arthropoda
  • Subphylum: Mandibulata
  • Superclass: Hexapoda
  • Class: Insecta
  • Order: Zygentoma
• Clade Palaeoptera


  Old wing
• Insects are not able to fold their wings neatly above their abdomen
• Their wings can move independently
• Most recognizable group of Palaeoptera


  • Order Odonata
• Order Odonata


  Toothed ones, they have strongly-toothed mandibles