Introduction to Phylum Annelida 2021-2022 PDF

Invertebrates  ‫جامعة األزهر‬ "‫كلية العلوم "بنين‬ ‫بأسيوط‬ Invertebrates Course: Invertebrates Code No: 232A & 221 No. of Unit: L...

Invertebrates  ‫جامعة األزهر‬ "‫كلية العلوم "بنين‬ ‫بأسيوط‬ Invertebrates Course: Invertebrates Code No: 232A & 221 No. of Unit: Lectures 4, Practical 4 Academic year: 2nd year Biology & BioChemistry First term ‫توزيع الدرجات‬ Final exam Practical exam Mid-term Oral exam exam 100 60 28 12 Aim of Course 1) Familiarity with the major invertebrate phyla ( Annelida, Arthropoda, Mollusca, and Echinodermata); 2) Invertebrate morphology, anatomy, and life history; 3) Evolution of Invertebrates; 4) Invertebrate behavior; 5) Collection methods  Contents Study of the characteristics and classification of phylum Annelida with description of functional morphology of examples for each class. Study of the characteristics and classification of phylum Arthropoda with description of functional morphology of examples for each class. Study of the characteristics and classification of phylum Mollusca with description of functional morphology of examples for each class. Study of the characteristics and classification of phylum Echinodermata with description of functional morphology of examples for each class. Basic characteristics of animal classification 1. Number of body cells 2. Organization 3. Germ layers 4. Symmetry 5. Coelom 6. Origin of mouth  1- Number of body cells Cellular A cellular  2- Organization Protozoa Parazoa Metazoa  3- Germ layers Diploblastic Triploblastic 1. Ectoderm- outermost germ layer (forms skin, nerves ) 2. Mesoderm- middle germ layer ( forms muscle, kidney, liver etc.) 3. Endoderm- innermost germ layer ( forms digestive and reproductive tract )  ectoderm endoderm Mesoderm forms as an out pocketing from endoderm  4- Symmetry ( a ) radial- can be divided along any plane, through a central axis into roughly equal halves ( b ) bilateral- can be divided down it’s length Asymmetrical only one way into similar right and left halves (not shown asymmetry- irregular in shape  5- Coelom Coelomate- has a true coelom CAVITY WITHIN A BODY Acoelomate- lacks a true coelom Pseudocoelomate- false body cavity ( no mesodermal connection ) 6- Origin of mouth Protozoa Parazoa  Metazoa Phylum: Cnidaria  Phylum Platyhelminthes Exhibit bilateral symmetry, acoelomate, and triploblastic Phylum: Nematoda Roundworms  Annelids Have round worm like bodies Have bodies divided into segments  Arthropods Have lots of legs and segmented bodies. There are four group of arthropods: – Arachnids – Centipedes & Millipedes – Crustaceans – Insects  Arthropods - Arachnid Have four pairs of legs. Have bodies divided into two sections  Arthropods – Centipedes & Millipedes Have long thin bodies and pairs of legs on each of their many body sections  Arthropods - Crustacean Have five-seven pairs of legs First pair often used as pincers Bodies covered in shell  Arthropods - Insects Have three pairs of legs Bodies divided into three sections Often have wings  Molluscs Crawl on a single fleshy pad. Can have a shell  Echinoderms Have bodies divided into five parts Have spiny outer covering  Phylum Annelida (Segmented worms, Ring worms, Bristle worms)  Phylum Annelida ✓General characteristics ❖Large successful phylum in water & on land 15,000 species Include earth worms, sand worms, fan worms, leeches Worldwide distribution: marine, brakish, fresh water and terrestrial. ❖Elongated worm like body ❖Can range in size from less than 3mm to more than 3m! ❖Mesoderm on inside of body wall and outside of digestive system  Phylum Annelida ✓General characteristics The body of an annelid usually consists of a two- part head (prostomium and peristomium) ▪ Prostomium is defined as the region of the head of annelids that is present in front of their mouth region. ▪ Peristomium is defined as the segment that is present in the front which surrounds the mouth.  Phylum Annelida What are the Similarities Between Prostomium and Peristomium? ❑ Both Prostomium and Peristomium are segments of the annelids body ❑ Both are present in the anterior region of the body.  Phylum Annelida What is the difference Between Prostomium and Peristomium? Prostomium Peristomium Contains a mouth region and Does not contain any organs sensory organs It assists the annelids body Does not possess any unique to be pushed into the soil functions due to the absence of organs Prostomium is located in the Peristomium is located in the head region. first part of the body in the front region.  Phylum Annelida ✓Metamerism ⚫ A series of body segments (metameres), and a terminal segment called the pygidium with anus. ⚫ The body segments are separated internally by walls of tissue called septa (Singular ~ septum), and each segment is called a metamere.  Phylum Annelida ✓General characteristics ⚫ Most annelids have paired appendages on most segments = parapodia - Used for locomotion - respiration ❖ In some, parapodia modified into fans and mucous bags for feeding or to create water currents  Phylum Annelida ✓General characteristics ⚫ Annelids have both longitudinal and circular muscles, which create waves of expansion and contraction called peristalsis. Annelids also have a true coelom like us, meaning that the entire body cavity is lined with mesoderm tissue. Platyhelminthes Nematoda Annelida This is of course a simplified diagram.  Body wall Epidermis is a single layer of cells (columnar epithelium) Epidermis secretes a thin flexible cuticle and setae  Body wall Setae – small chitinous bristles Most annelids have setae repeated on each segment ✓ Used as anchors while burrowing ✓ to prevent capture ✓ some used for swimming ✓ or as protection or camouflage  Body wall ❖ Behind epidermis is two layers of muscle tissue ▪ Thin layer of circular muscle ▪ Thick layer of longitudinal muscle ( obliquely striated)  Body wall ❑ Body cavity of true coelom Lined with peritoneum (squamous epithelium) Lined inside of body wall & outside of digestive tract ❖Peritoneum also forms mesenteries that hold blood vessels and the septa between segments  Movement Coelom is filled with fluid (except leeches) which serves as hydrostatic skeleton ▪ Annelids have 3 general types of movements: 1) Burrowing, 2) Crawling, 3) Swimming.  Movement ▪ Annelids have two major kinds of body muscles: longitudinal muscles move from the front to the back and make the worm shorten circular muscles wrap around each statement and can make the worm longer ▪ The worm alternates contracting and relaxing these to move. ❑ Marine worms have appendages that help them swim.  ✓ Feeding & digestion ❑ Complete digestive tract with mouth & anus ❑ Muscle layers allow modification of tract into various structures: Pharynx with teeth Esophagus Crop (food storage area) Gizzard (thick and muscular helps physically break up food)  ✓ Feeding & digestion Intestine ❑ In some the first part of intestine is used for digestion by secretion of digestive enzymes. ❑ Most of intestine is used for absorption - On dorsal surface is infoldings = typhlosole (increases surface area for absorption) Lining intestine are yellowish chloragogen cells ▪ Equivalent to our liver, synthesizes glycogen and fats ▪ They also travel through coelom to repair wounds ▪ Function in excretion: convert amino acids to urea & ammonia  Respiration Respiration mostly occur through skin (body wall) ▪ This type of respiration is called CUTANEOUS RESPIRATION Some through parapodia A few have gills Setae or Chetae (made of chitin)  Circulation ✓Closed circulatory system have 2 main vessels: ▪ Dorsal and ventral vessels connected by capillary network Blood vessel ❖Dorsal vessels pumps blood anteriorly ❖Ventral vessels pumps blood posteriorly ✓Several hearts (5 in earthworms) are used to pump blood through the closed circuit.  Skeletal system ▪ Coelom: fluid-filled cavity that separates gut from body wall ▪ Hydrostatic skeleton Coelom which creates hydrostatic pressure and acts as a hydrostatic skeleton Most primitive skeletal system  Nervous system Consists of brain (a pair of cerebral ganglia),which is connected to a pair of ventral longitudinal nerve cords with a ganglion in each segments (metameric) sense organs include: eyes, taste buds, tactile tentacles, and organs of equilibrium called statocysts.  ✓ Excretory system ❖ Consists of one pair of nephridia (=metanephridia) in each segment (metameric) ❖ Nephric tubule: ▪ Nephrostome = Ciliated funnel (remove wastes from the blood and coelomic fluid) ▪ Coiled ciliated tubule surrounded by capillaries ▪ Bladder like structure ❖Nephridiopore = opening to outside  Life Cycle/Reproduction Most annelids are hermaphroditic, but some do have separate sexes. 1) Two worms attach to each other and exchange sperm, which they store in special sacs. 2) When the eggs are ready, a band of thickened, specialized segments (a clitellum) secretes a ring of mucus into which the egg and sperm are released. 3) The ring them slips off the worm and the eggs hatch a few weeks later.  Ecology of Annelid ⚫ Annelids are Annelids live in a diversity of freshwater, marine, and terrestrial habitats. They vary in what they feed on and how they obtain their food. ⚫ Earthworms are deposit feeders. They burrow through the ground, eating soil and extracting organic matter from it. Earthworm feces, called worm casts, are very rich in plant nutrients. Earthworm burrows help aerate soil, which is also good for plants.  Ecology of Annelid ⚫ Polychaetes live on the ocean floor. They may be sedentary filter feeders, active predators, or scavengers. Active species crawl along the ocean floor in search of food. ⚫ Leeches are either predators or parasites. As predators, they capture and eat other invertebrates. As parasites, they feed off the blood of vertebrate hosts. They have a tubular organ, called a proboscis, for feeding.  Phylum Annelida Class Class Polychaeta Clitellata Sand worms Subclass Subclass Oligochaeta Hirudinae earthworms Leeches  Phylum Annelida Class Class Polychaeta Clitellata Sand worms Subclass Subclass Oligochaeta Hirudinae earthworms Leeches  Class Polychaeta ⚫ Name polychaete means “many + long hairs”. ⚫ About 70% of all annelids (10.000 spp.) ⚫ Many setae per body segment. ⚫ Mostly marine, a few found in fresh water and dioecious with gonads repeated. ⚫ Most segments with parapodia used for crawling, swimming, feeding and respiration. ⚫ They are predaceous animals ⚫ Examples include the sand worms, fireworms Phylum Annelida  ✓Body plan head ❑ Distinct head with mouth and sense organs ❑ Worm like body with repeating segments ❑ Body segments with flaplike parapodia ❑ Clitellum is absent. Body segment ✓Head ▪ Head has retractile pharynx with jaws Anal cirri used to capture prey ▪ Lots of different kinds of sense organs on head 1. Chemoreceptor (nuchal gland) on palps and tentacles 2. Touch receptors also on tentacles for locating food and shelter 3. Eyes  ✓sense organs: ▪ Prostomial tentacles Tactile function ▪ Prostomial palps Organs of touch, taste and smell ▪ Nuchal organs Organs of smell, chemoreception, and help worm in detecting prey ▪ Peristomial cirri Tactile function ▪ Eyes. Eyes are not image-forming but enable the worm to detect changes in light intensity. ✓ Feeding & Digestion ❑Free swimming polychaetes are predators ❑Sedentary polychaetes are deposit feeders ❑Foregut: pharynx and jaws, esophagus lined with cuticle ❑Mid gut: secrete digestive enzymes in posterior section absorbs nutrients ❑Hind gut: anus ✓ Respiration ❑Usually through parapodia ❑Some have paired gills on some segment ❑Some have no special organ and exchange across body surface ✓ Reproduction ❑ Sexes are separate. ❑ Fertilization external, free-swimming larval stage trochophore. ❑ Asexual reproduction by lateral budding ✓ Circulation ❑Closed circulatory system ✓ Excretion ❑Protonephridia and in some metanephridia or both ❑1 pair per segment ❑Opens into coelomic compartments ❑Tubules absorbs any useful materials and concentrates wastes as fluid passes to nephridiopore ✓ Nervous system ❑Dorsal ganglia ❑Double ventral nerve cord with paired ganglia in each segment  Phylum Annelida Class Class Polychaeta Clitellata Sand worms Subclass Subclass Oligochaeta Hirudinae earthworms Leeches  Subclass Oligochaeta (Few setae) ▪ Over 3000 spp. ▪ Mostly terrestrial; night crawlers, earthworms burrow in moist soil and emerge at night to feed on detritus and vegetation. ▪ Prostomium lacks sensory structures ▪ No parapodia and have few setae ▪ No distinct head and have no eyes. ✓Body wall Protective layer of collagenous cuticle secreted by epidermis Segments contains pores for coelomic fluid to leak out and lubricate outer surface of animal Also has numerous mucous gland ✓Excretory system Consists of paired metanephridia (metameric) Excretory tubes with ciliated funnel remove waste from the coelomic fluid; open to the outside via excretory pores ✓Feeding & Digestion ❖Well developed digestive tract Mouth – pharynx- esophagus- gizzard- intestine- anus Pharynx – pump food in crop, Crop – temporary stores food, Gizzard – muscular, lined with cuticle, grinds food, ✓Feeding & Digestion Intestine – most chemical digestion and absorption - Allow them to eat soil then the intestine sorts out the nutrients for absorption ❑Typhlosole in intestine improve absorption of nutrients and increase its surface area ❑Chloragogue cell surround outside of intestine store nutrients ❑Synthesize glycogen and fats ❑Eleminate some metabolic wastes  ✓Respiration ❖No respiratory organs or parapodia like polychaetes ❖Breath through skin, no lung or gills ✓Sense organs ❖ Numerous sensory cells (chemo- and mechano receptors) on skin ❖ Chemoreceptors especially on prostomium ❖ Many free nerve endings – probably tactile ❖ Earth worms have no eyes but do have numerous photoreceptors in epidermis ✓Nervous System A mass of ganglia (neural masses) forms an anterior brain that is usually dorsal to the pharynx. They have either a pair of ventral nerve cords (primitive) or a single ventral nerve cord that runs the length of the body. Each segment has a swelling of the nerve cord called a segmental ganglion.  Body Cavities Mesoderm coelom Eucoelomate- body cavity completely lined with mesoderm gut Ectoderm Endoderm Hydrostatic Skeleton Earthworm Phylum Annelida Closed Versus Open Circulatory Systems Closed Circulatory System  Earthworm Reproduction ⚫ Mating earthworms are held together by mucus secreted by an organ called the clitellum, and they are also held together by ventral setae. ⚫ Sperm are discharged and travel to an opening called the seminal receptacle. ⚫ After sperm exchange, the worms separate. ⚫ Each worm then secretes a protective covering over the clitellum that forms a cocoon.  Earthworm Reproduction ⚫ The cocoon slides forward along the body. ⚫ As it slides forward, it passes over the oviducts. ⚫ Eggs from the oviduct and sperm from the seminal receptacles transfer into the cocoon. ⚫ After fertilization the cocoon slides off the worm. ⚫ The embryos develop in the cocoon and eventually emerge as juvenile worms.  Phylum Annelida Class Class Polychaeta Clitellata Sand worms Subclass Subclass Oligochaeta Hirudinae earthworms Leeches  Subclass Hirudinea 500 spp. Leeches Shape and size ❖ The body is dorso-ventrally flattened.  Subclass Hirudinea 500 spp. Leeches Shape and size ❖ Most 10-15 cm long; some up to 35 cm long ❖ Body is broader near to the posterior end and narrow at the anterior end  Subclass Hirudinea 500 spp. Leeches Coloration ❖ Dorsal surface is yellow green, and ❖ Ventral surface is orange yellow or orange red  Subclass Hirudinea 500 spp. Leeches Segmentation ❖ Body of leech is metamerically divided into Fixed number of true segmented (33 segment), they also called somites ❖ Except the first two and last seven, ❖ Each segment subdivided into rings or annuli ❖ A typical segment possess (5 annuli)  Subclass Hirudinea 500 spp. Leeches Segmentation ❖ A temporary clitellum is formed by (9th, 10th, and 11th) during breeding season.  Subclass Hirudinea 500 spp. Leeches Found in freshwater ponds, marshes, streams and swamps. No parapodia, no setae ▪ Feeds on blood of vertebrates ▪ Locomotion: by swimming, crawling and looped. ▪ Respiration by diffusion through skin. ▪ Excretion by nephridia.  Body Wall Body wall formed of: 1) A thin cuticle, 2) Epidermis, 3) The dermis, 4) Muscles, and 5) Botryoidal Tissue  Body Wall Body wall formed of: ❑ Epidermis - built up of a simple columnar epithelium with modified glandular or mucus secreting cells. ❑ The dermis consists of a matrix containing pigmented cells, muscle fibers and a capillary network. ❑ Muscles: - Formed of an outer layer of circular fibers, crossed by oblique fibers and an inner layer of longitudinal fibers.  Body Wall Body wall formed of: ❑ Botryoidal Tissue ▪ Beneath the longitudinal muscles and immediately surrounding the alimentary canal. ▪ This tissue fills the entire coelom except a few spaces termed the haemocoelomic spaces. ▪ It is probably excretory in function.  Digestive system Buccal region: Three serrated chitinous jaws are present. Pharynx: extends in (segments 4-7), which help in producing the pump-like action for blood sucking. Salivary glands are present and open into the pharynx (secrete hirudin; an enzyme which prevents blood clotting).  Digestive system The crop: extends along 11 segments (8-18 ). Crop and its diverticula are capable to store enormous quantity of blood which can be digested slowly. The stomach: - It is the digestive region, in segment 19. Intestine: - increase its absorptive surface. Rectum: - It runs slightly upwards and opens to the exterior through a small anus placed mid-dorsally on the 26th segment.  Respiration ❑Most exchange gasses through skin A few aquatic forms have gills Excretion ❑Consists of 17 pairs of nephridia lying in segments 7-23. Nervous system ❑consists of a pair of suprapharyngeal ganglia lying above the pharynx ❑connected through a pair of circumpharyngeal commissures to a double ventral nerve cord that runs within the ventral blood sinus.  Reproductive System Hermaphroditic. ▪ Cross fertilization during copulation -Mating process like to earth worm ▪ Have a clitellum. -Produce cocoon that receives eggs and sperm Fertilization - Internal fertilization takes place in the vagina of each individual and the fertilized ova are discharged into a cocoon for further development.  ✓ Male system segments (13-21). - Consists of 9 pairs of testes enclosed in a coelomic sac. A short vas efference A long vas deferens Epididymis or seminal vesicle Prostate gland Ejaculatory duct  Female system segment (12). ❑ Female reproductive system consists of: ovaries enclosed in ovisac. oviducts vagina ❑ The walls of the common oviduct are provided with albumen-secreting cells, hence comprise an albumen gland. ❑ The vagina opens to the outside by the female genital opening (on segment 12).  ✓ Male system segments (13-21). - consists of 9 pairs of testes enclosed in a coelomic sac. - A short vas efferens comes out from every testis. - The 9 vas deferens of each side open into a long vas deferens. - This coils up anteriorly in segment 11 forming an epididymis or seminal vesicle, which lead to ejaculatory duct. - The two ejaculatory duct open into a prostate gland from which a curved muscular penis opens to the exterior by the male genital opening (on segment 11).