Invertebrate Lecture 5 PDF

# Causes for great diversity and abundance of Arthropods - The exoskeleton (highly protective). - Segmentation and appendages (more efficient locomotion). - Air piped directly to cells (respiratory system more efficient). - Highly developed sensory organs. - Reduced competition through metamorphosi...

# Causes for great diversity and abundance of Arthropods - The exoskeleton (highly protective). - Segmentation and appendages (more efficient locomotion). - Air piped directly to cells (respiratory system more efficient). - Highly developed sensory organs. - Reduced competition through metamorphosis. # Economic Importance of Arthropods - Arthropoda as food: Lobsters, crabs, and shrimps - Honey from bees. - Plankton as food for fish. - Insects as food for birds and animals. - They are important vectors for carrying diseases. - The stings and bites of arthropods may be irritating or painful, but very few inject dangerous toxins. - Silk is produced by larvae of silk-worms. # Classification of Phylum Arthropoda (Mind Map) | Phylum Arthropoda | Sub-Phylum | Class | |---|---|---| | | Trilobitomorpha | Trilobita: (extinct) | | | Chelicerata | Arachnida: Spiders, Scorpions | | | | Merostomata: Horseshow crabs | | | | Pycnogonida: Sea spiders | | | Myriapoda | Chilopoda: Centipedes | | | | Diplopoda: Millipeder | | | | Pauropoda: | | | | Symphyla | | | Crustacea | Branchiopoda: brine shrimp | | | | Remipedia: Bind crustaceans | | | | Chephlocarida: horseshoe shrimp | | | | Maxillopoda: Barnacles | | | | Ostracoda: Seed shrimps | | | | Malacostraca: lobsters, crabs, shrimp | | | Hexapoda | Insecta: Insects (Winged Insects) | | | | Entognatha (Wingless Insects) | # Sub-Phylum: Trilobita - Characteristics: - Gr., tri, three +lobos, lobe + morphe, form - All marine, all extinct. - Body divided into 3 longitudinal lobes. - Body divided into three tagmata - Head- feeding & sensory. - Thorax- locomotion. - Abdomen- visceral organ. - One pair of antennae. - Uniramous appendages. # Subphylum: Onychophora (G., *onychos*= claw + *phoros*= bearing) - General Characters: - Commonly called "velvet worms," or "walking worms." - They compose approximately 70 species of caterpillar-like animals, - Ranging from 1.4 to 15 cm in length - They live in rain forests and other moist, leafy habitats in tropical and subtropical regions and in some temperate regions of the Southern Hemisphere. - Terrestrial, primitive, worm-like and un-segmented animals. - Single pairs of antennae, eyes and jaws. - Numerous short, un-jointed clawed legs. - Characters: - Body is elongated, cylindrical (few cms long caterpillar-like) without external segmentation. - Head is not distinct (formed of 3 segments), and bears a pair of antennae, a pair of jaws, a pair of oral papillae and a pair of simple eyes. - The ventral mouth has a pair of claw-like mandibles and is surrounded by a pair of oral papillae which can expel a defensive secretion. - Trunk bears a series of paired short appendages, which vary in number 14-42. - Most velvet worms are predaceous, feeding on caterpillars, insects, snails, and worms. - Peripatus crawls by means of the legs and by extension and contraction of the body - Anus lies at the hind end. - Slime glands discharge glue from oralpapillae. - Attack prey by shooting glue from a distance through oral papillae. - Sexes are separate and gonads are paired. - Mostly viviparous, while some are oviparous. - They are nocturnal. # Peripatus is a connecting link between Annelida and Arthropoda - Annelid like: - Segmentation. - Musculature – circular/ longitudinal. - excretory system - nepluridia. -Cilia and flagella are present - Arthropod like: - Respiratory tree of trachea, - Haemocoelic body cavity, - Chitin excoskeleton (non waxy), - Mouth parts with jaws. # Subphylum: Onychophora (Body Wall of Peripatus) - The body wall is consisting of, - Cuticle - Epidermis - Dermis - and muscles # Subphylum: Onychophora (Digestive System) - The digestive system consists of: - Alimentary Canal: - It begins with the mouth and consists of a pharynx and oesophagus (Foregut) - Midgut composed of (stomach intestine) - Hindgut or rectum. - Digestive Glands: - Salivary Glands: A pair of salivary glands opens into a median dorsal groove in the preoral cavity. The salivary secretions are passed into the body of the prey, and the digested tissues are then sucked into the mouth. # Subphylum: Onychophora (Respiratory System) - The respiratory system consists of air tubes called tracheae or tracheal tubes. - The tracheae extend throughout the body and communicate to outside through minute spiracles. # Subphylum: Onychophora (Excretory System) - The excretory organs are nephridia. - A typical nephridium consists of a long ciliated funnel, a coiled duct and a contractile bladder called vesicle # Subphylum: Onychophora (Nervous System) - The nervous system consists of: - a pair of supra-pharyngeal ganglia or brain, - Two circumpharyngeal connectives, - a pair of lateral longitudinal nerve cords connected together by transverse commissures. # Myriapoda ## Classification | Phylum Arthropoda | Sub-Phylum | Class | |---|---|---| | | Myriapoda | | | | | Class 1: Chilopoda: Centipedes | | | | Class 2: Diplopoda: Millipedes | | | | Class 3: Pauropoda: | | | | Class 4: Symphyla | ## Unique and interesting features - Milli means 1000 and centi means 100. - Pede means foot. - Millipedes protect themselves by curling into a ball and spraying hydrocyanic acid. ## Myriapods (The term “myriads" means many footed) or Many pairs of legs - Two body sections (head and trunk) - One pair of antennae on the head - Simple eyes - Mandibles (lower jaw) and maxillae (upper jaw) - Respiratory exchange occurring through a tracheal system - Excretion by 1 or 2 pairs of Malpighian tubules - Sexes separate. # Myriapods are divided into the following taxonomic groups: - **Millipedes (Class Diplopoda)** (millipedes "1000 feet") - two pairs of legs per segment. - one pair of short antennae. - usually harmless vegetarians. - e.g. Iulus - **Centipedes (Class Chilopoda):** (Chilopoda (centipedes "100 feet") - one pair of legs per segment. - poisonous fangs for killing prey. - long antennae. - e.g. Scolopendra # Scolopendra sp. ## Characterestics - Scolopendra is commonly called centipede. - Nocturnal, found in tropical and sub-tropical countries. - Carnivorous, feeding on insects, spiders, worm's slugs, etc. - Commonly lives in soil and beneath stones bark and logs in moist and damp areas and human dwellings. - Body is long, flat and divisible into head and trunk. - Head is distinct, covered dorsally by a cephalic shield and bears a pair of antennae, a pair of mandibles and two pairs of maxillae. ## External Features of Scolopendra - Body is long, flat and divisible into head and trunk. - Head is distinct, covered dorsally by a cephalic shield and bears a pair of antennae, a pair of mandibles and two pairs of maxillae. - Trunk segments numerous, each bearing a single pair of legs. - First pair of trunk appendages or maxillipeds bears a sharp claw connected with the poison gland. - Chitinous exoskeleton is soft and flexible, with very low calcium content - Genital opening situated at the hind end of the body. - Sexes are separate. - Scolopendra is harmful to mankind. # Subphylum Chelicerata - Horseshoe crabs, spiders, ticks, mites, scorpions - Body divided into 2 regions: - Prosoma / Cephalothorax (fused head & thorax). - Abdomen. - Lack jaws. - Have 6 appendages & no antennae. - First pair of preoral chelicerae with claws, followed by postoral pedipalps and 4 pairs of walking legs. ## Class Arachnida: - spiders - Ticks - Scorpions