Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lecture -17 Phylum Arthropoda Arthropods "arthropod" = arthros - jointed, podes - feet. Arthropod Diversity • Arthropods make up over 75% of all living organisms. • Over 1 million species have been described. • They are distributed aa over, in a range from the shallow sea to mountain peaks. • They are the most successful animals on the earth. Arthropods - Size range from microscopic insects and crustaceans to the king crab(12 feet) Parasites Feed on plants Predators • They have an external skeleton (exoskeleton) secreted by epidermis. It is made up of protein (chitin) and lipids Cilia are not present. • Exoskeleton: - Provides protection - Support and locomotion. - Prevents water loss. • So, arthropods can live in too wet, too dry, too hot, even too cold habitats. • Arthropods are recognized by their jointed appendages. • Individual appendages have modified into antennae, mouthparts, or legs. - Jointed legs for more efficient locomotion • Arthropod bodies are segmented. 1. Many segments. 2. Segments are fused together into functional groups (tagmata) - Eg. head or thorax of an insect This fusing process is known as tagmatization. • All arthropods have a distinct head, • sometimes fused with the thorax to form a tagma called the cephalothorax. Muscular system includes smooth muscles and striated muscles as in chordates. Movement of appendages is controlled by these muscles. Striated muscle For quick action Arthropods have a pair of compound eyes and one to several simple eyes (ocelli); A compound eye consists of hundreds or thousands of lenses. So, they can see a very wide angle of vision; (can see even right behind them). But are very short sighted. • Arthropods are eucoelomate, - coelom is much reduced. •The body cavity is an open "hemocoel," (a space filled loosely with tissue, sinuses, and blood). • The circulatory system is open and consists of a heart, arteries, and the open spaces of the haemocoel. • Respiration takes place through the body surface, gills, tracheae, or book lungs. • The nervous system is annelid-like. - A brain and a double ventral nerve cord • Most arthropods are dioecious (monosexual) and have paired reproductive organs (ovaries, testes). • Fertilization is internal. • Most lay eggs (oviparous). • Arthropods grow by moulting their exoskeleton (ecdysis). • Development proceeds with some form of metamorphosis. (Atelocerata) Class Symphyla Sub phylum Chelicerata • Examples; Scorpions, Spiders, Ticks, and Mites, Horseshoe crabs, “Sea spiders" Characteristics of Subphylum Chelicerata 1. Their body is divided into two regions (tagmata) - cephalothorax (prosoma) and - abdomen (opisthosoma). 2. They do not have a distinct head 3. Cephalothorax contains six pairs of appendages 4. Chelicerae are adapted for feeding - to pierce the prey - to tear apart the prey 5. Feeding habit – sucking liquid food from their prey Class Merostomata Diversity of Class Merostomata •Only 5 species and 3 genera exist today. Eg. Horseshoe crab, Limulus •They are marine – burrow in mud near the shore. • Feed on small invertebrates. • They are nocturnal. •Their geographical distribution is limited. N. America SE Asia Indonesia Characteristics of Class Merostomata 4. The pedipalps, resemble walking legs. Function - walking Mouth Gnathobase (to grind food) Chilaria (to crush food) Last pair of walking legs (to clean book gills) 5. Abdomen is broad. It bears; 1. Genital operculum 2. Gill flaps (5 pairs) (about 150 book gills inside them) for respiration Anus Class Arachnida Includes over 70,000 described species . Examples ; Spiders, scorpions, Ticks and mites •Arachnids are generally: - aggressive, - predatory, - preying on small arthropods. • Nearly all species are terrestrial. • The prosoma is dorsally covered with a carapace. Pedipalps are modified into grabbing & killing prey. •They have simple eyes (Ocelli) . Spiders Spiders include 36,000 described species. 1. Cephalothorax and abdomen are divided by a narrow stalk (pedicel). 2. Chelicerae bear poisonous fangs. Pedipalp 3. Coxal glands for excretion Walking legs 5. Spinnerets (silk glands) for spinning silk 4. Abdominal appendages are book lungs (for respiration) Do not show external segmentation Mites and ticks • Around 10,000 species described. Ticks are bigger but mites are microscopic. • No external segmentation • Cephalothorax and abdomen are fused (Dorsally covered by carapace) • Ticks have a false head( capitulum), carrying mouth-parts. Scorpions (1200 species): The pedipalps are modified into large claws Chelicerae are small. Sting Post-abdomen Pre-abdomen Pedipalp Pseudoscorpions (2000 species), Lecture 18, 19 Arthropods III, IV Learning Outcomes • Characteristic features and diversity of Subphylum Crustacea Subphylum Crustacea Diversity Approximately 45,000 species. Crustaceans are the fourth most species group of metazoans on earth, behind Insects, Mollusks, and Chelicerates. • Most are aquatic - majority are marine - some are found in fresh water • Few on land. • Crustaceans are the only arthropod group that has primarily aquatic forms. Crustaceans include; • Lobsters • crabs • crayfish • shrimp And several other groups of organisms. • Most crustaceans are free-living; but some are sessile – Eg. Barnacles A few are parasitic. Suculina • Crustaceans are: – filter feeders –active predators –scavengers Characteristics of Subphylum Crustacea 1. Body comprises of two tagmata. - cephalothorax - abdomen 2. Crustacean appendages are branched (biramous). (primitive) 3. Crustaceans have 2 pairs of antennae. a pair of antennule a pair of antennae •4. Crustaceans develop through a larval stage called a nauplius larva. 1st antenna 2nd antenna Mandible Classification of Sub phylum Crustacea Class Malacostraca Class Branchiopoda Class Ostracoda Class Copepoda Maxillopoda Class Branchiura Class Cirripedia Class Malacostraca (Soft shell) • Comprises about 24,000 described species. • All body segments bear appendages Typical malacostracan Class - Malacostrata Order Decapoda Isopoda Amphipoda Order Decapoda (Ten foot) • This is the largest order of crustaceans (10,000 species). • First pair of walking legs are modified to form pincers =Chelae (Cheliped). Cheliped: help capture prey (modified first walking leg) •The eggs are retained by the females until they hatch into free-swimming larvae. Lobster Crabs Decapoda • Crabs have a broader carapace. • and a much reduced abdomen. Hermit crabs They have adapted to live in snail shell. Their abdomen lacks a hard exoskeleton. King crab Order Isopoda (Equal foot) • They have no carapace. • They are dorsoventrally flat. Armadillidium Some are found on Land In moist places, – pill bugs Armadillidium Terrestrial wood louse Some are parasitic on fish Freshwater isopod -Sow bug • Marine shallow-water isopods Order Amphipoda (both side foot) Beach hoppers Gammarus Similar to Isopods but laterally compressed. Caprella - Amphipoda Class Branchiopoda • Small to moderate-size crustaceans • Primitive, aquatic, mainly freshwater crustaceans: • water flea - Daphnia • Brine shimp - Artemia Water flea Daphnia branched antenna • Minute freshwater crustacean, common in temporary freshwater ponds. • They move about like a flea by means of hairy branched second antennae. • The head is bent down towards the body. • The rest of the body is covered by a laterally compressed bivalve-like carapace (transparent – large shield). • Legs are paddle like (respiratory gills) Brine shrimp Artemia salina No carapace. The thorax consists 11pairs of appendages. Theyare filtratory; By beating they propel the animal forward and draw food particles toward it. They swim with their ventral surface uppermost. Telson Salt water crustacean • The eggs (cysts) are produced when their lake is drying out (in high salinity). • These eggs contain a "sleeping" embryo which scientists believe survive up to 1000 years. Cyst (egg) Nauplius larva Artemia live on Earth for 100 million years, so they are colleagues of the dinosaurs. • Artemia cysts - a commercial fish food Class Ostracoda (shell, mussel shrimp) - Cypris They are tiny marine and freshwater crustaceans enclosed in a bivalve shell (carapace) • They are zooplankton, living on the sea floor. •Thoracic appendages reduced to two or none. •They are mostly head. Class Copepoda - Cyclops - minute - marine (majority) and freshwater crustaceans. They have an elongated transparent body; - large antennae - Single median eye (nauplius eye) - armoured exoskeleton (but no carapace) - a forked tail Elongate body, tapers towards posterior end. No carapace. Four pairs of thoracic appendages-for swimming. They are the dominant zooplanktons. Class Branchiura They are ecto-parasites of freshwater fishes. Broad shield like carapace. No gills. Compound eyes are present Four pairs of thoracic appendages. Abdomen reduced. Mouth appendages modified as Sucking cups. Argulus (fish louse) Class Cirripedia Barnacle- (900) species • Adult forms a hard calcareous shell. • They remain attached to submerged surfaces, - rocks , ships’ or boat’s bottoms Acorn Barnacles (Balanus) Tiny particles of food trap by cirri. Cirri - feathery retractable organs (thoracic appendages) Cirri emerge from openings between the shell plates. Adult barnacles are hermaphrodites. Parasitic barnacles - Saculina Saculina - branches through the tissues of its host (the common shore crab) . It produces only large brood-sac externally under the host's abdomen, containing its many eggs. Pill bugs Armadillidium Gammarus Caprella Cyclops Lecture - 20 Arthropods V Subphylum Uniramia (Atelocerata) • The largest and most varied arthropod group. • Uniramians are characterized by; 1. Presence of modified appendages located at the edge of the mouth - (mandibles) - Mandibles are used as jaws. 2. Presence of one pair of antennae. 3. Presence of Uniramous appendages. • Subphylum Uniramia (Atelocerata) Class Diplopoda Class Chilopoda Myriapoda Class Hexapoda (Insecta) Myriapods • Include; centipedes and millipedes. • Their bodies are made up of many segments. • They live in moist micro-habitats. Class Chilopoda - Centipeds Over 2500 species. Body segments are flattened. Each segment bear a pair of appendages (legs). The appendages of the first body segment modified to poisonous fangs - to capture prey • Centipedes are predatory, feeding on soil invertebrates . • They run fast to escape from danger. •The young ones resemble miniature adults. Class Diplopoda - Millipeds • Body segments are cylindrical. • Each segment bear two pairs of legs. Except first four segments each bear a single pair of legs. • Millipedes lack poisonous fangs and do not bite. • They live on decaying plant and animal matter. • They are slow movers. 10, 000 described species are Millipeds – bio indicators Class Hexapoda - Insecta (insects) Insects include a great majority of the species of animals on earth. - one million named species (100,000) - several millions unnamed. They are the most successful group of animals. • Insects are found in almost all terrestrial and freshwater habitats; - from deserts to freshwater ponds - from tropical rainforest to the arctic wastes - A few marine Their feeding habits are varied. - Phytophagous (herbivores) - Omnivores - Predators - Parasitic • Insects show huge variety in shape and form. - but they do not have very large body size. Characteristics of Insects • Insect body wall is a Chitinous cuticle. • Thin epicuticular layer (wax layer) highly resistant to water and other solvents. • Insect body divides into 3 tagmata; - head, - thorax and - abdomen Each tagmata composed of several smaller segments. Insects (in=into, sect=cut) • Insects are morphologically divided into two groups. – Wingless insects (Subclass Apterigota) – Winged insects (Sub class Pterigota) Most insects have wings. Wings are found on the 2nd and 3rd thoracic segments. (10 segments) Each thoracic segment contains a pair of legs. Abdomen (10 segments)- No appendages Head appendages are modified for feeding (mouthparts). Thoracic appendages Insects have different life cycle patterns It is an important characteristic of insects. 1. Eggs on hatching produce miniature adults. Direct development (Ametabolous) Wingless insects Silverfish 2. Newly hatched young (larva) are completely different in appearance from adults. These larval forms - live in different habitats, - eat different foods, Reduce competition The larva feeds and grows. It molts periodically. Become non-feeding encased pupa. Pupa undergoes a complete transformation to a fully-formed adult emerges ("metamorphosis“) . "holo-metabolous." 3. The newly hatched young (nymphs) are more similar to the adult; but small in size, lack wings, sexually immature. They undergo a more gradual process of development to become adults. "hemi-metabolous." Hemimetabolous Insects Order Odonata Dragonfly Order Orthoptera Cricket Grasshopper Order Isoptera Termites Order Hemiptera Water bug Order Homoptera • Aphid Order Blattodea Cockroach Order Phasmida Walking leaves Stick insect Order Mantodea Praying mantis Adult nymphs Egg case Holometabolous insects Order Coleoptera Beetles Pupa Larva Eggs Order Lepidoptera Butterfly Wings cover with scales Moth Order Diptera Mosquito Housefly Order Hymenoptera Ant Wasp Ant Insect Feeding habits are varied • Insect mouthparts are modified for their feeding habits. • Most of the insects are plant feeders. • Mouthparts are used to grind their food or suck as a juice and move it toward the back of the mouth. Grasshopper – chewing and biting Mouthparts are modified for feeding on plant parts. • Mandible well developed Plant bugs and mosquitoes - Piercing-Sucking • Mouthparts are modified to a needle like stylet. It is used to suck blood/plant juice. • Labium serves also as a food canal. stylet Labium Moths and butterflies - Siphoning When feeding the proboscis is uncoiled and extended. Nectar is sucked up into the mouth or oral cavity. House fly - Sponging Proboscis is the two soft lobes with many small tubules. When feeding saliva are pumped onto the food through the probosis. Mouth opening The dissolved food then moves by capillary action of sponge and ingested. Honeybees - Chewing-Lapping Mouthparts are modified to utilize honey and nectar. - to cut floral tissue to gain access to nectar, - for defense, and -for manipulating wax. Mouthparts forms a flexible and contractile tongue covered with hairs. It draws liquid into the body by slowly moving it back and forth. • The legs of many insects are specially adapted to the insect's mode of life. Grasshopper – Hind leg Jumping Femur enlarged Head louse - Clinging Mole cricket - Digging/burrowing • Mole crickets - front legs - modified for digging in the soil. Resembles a shovel (broaden). Honeybee The first leg notch – clean legs, antennae The hind leg Inside Curved rows of hairs ( pollen basket) Praying mantis - Raptorial/grasping