Marb 435 1st Edition Lecture 8 Outline of Current Lecture Bilateria part 2 and Platyhelminthes 1 Current Lecture All about urine Most aquatic invertebrates are ammonoletic i e produce ammonia Toxic Soluble in water Mammals amphibians some fish and some molluscs are ureoletic i e produce urea Non toxic Soluble in water Reptiles insects some molluscs and some mammals are uricotelic i e produce uric acid Non toxic Crystallizes Nephridia specialized organs that produce urine are like little kidneys Apart from nitrogenous wastes urine can contain other metabolic wastes excess ions spent hormones and toxins ingested with food Steps of Excretion 1 Ultrafiltration These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Filtration of body fluids blood coelomic or interstitial fluids through a macromolecular filter Results in primary urine Requires two adjacent fluid filled compartments 2 Modification Re absorption of useful metabolites from primary urine Secretion of specific wastes into primary urine 3 Release Discharge of Secondary urine final urine through a nephridiopore Excretory organs in Bilateria 1 Protonephridia Occur in animals without a blood vascular system coelom or both Usually small bodied animals with a single body cavity 2 Metanephridia Occur in animals with a blood vascular system and a coelom Platyhelminthes flat worms Soft bodied no cuticle or skeleton No circulatory system Acoelomate triploblastic and bilaterally symmetrical Hermaphrodites Spermatozoa with two tails No anus has gastrovascular cavity neoblasts stem cells that can develop into other cell types Classes of platyhelminthes that you need to know and things about them Class Turbellaria flatworms size range from 1 mm to 60 cm marine freshwater or humid terrestrial habitats although most are marine mostly benthic few pelagic species use cilia as legs to glide over surfaces but also has body wall musculature for looping or swimming Diet o Mostly predators o Some detritivores dead animals that sink to the bottom o Some herbivores algae diatoms Feeding strategies o Wrapping around prey and covering it with toxic mucus o Pinning prey down to substrate with adhesive organs o Many species have protrusible pharynx or proboscis o Stabbing of prey with penis has stylet and projects from the mouth Class Trematoda flukes Class Cestoda tapeworms Terms to know 1 2 3 4 Trichladida has three branches of gastrovascular cavity Polycladida has many branches of gastrovascular cavity Parenchyma spongy mesodermal tissue between the gut and epidermis Gastrovascular cavity has only one opening no anus 5 Tetrodotoxin TTX a highly toxic chemical that some flatworms can use to poison and consume their prey Can also be used by blue ringed octopus pufferfish and poison dart frog this is important to know Asexual reproduction Freshwater planarians have extraordinary regeneration capabilities If head or tail are bisected longitudinally each half grows a complete new head Even 1 300th of an animal can grow into a complete new worm Totipotent Neoblasts stem cells are responsible for regeneration of new tissue Gene responsible for regeneration was recently identified Same gene might have similar functions in other animals Sexual reproduction They are all hermaphrodites meaning they have both male and female structures Male reproductive structures Paired testes Vas deferens Seminal vesicle Penis Female reproductive structures Ovaries Oviduct Vitellaria Copulatory bursa Many polyclads use hypodermic insemination and try to stab each other with their penis without getting stabbed themselves This is known as penis fencing and it increases benefits of sperm donation over costs of sperm receipt Both organisms involved would rather be the male than the female because carrying and producing eggs takes much more work than just inseminating with sperm which leads to the fighting