BIOL 3454 1nd Edition Lecture 18 i Nutrition 1 Most are scavengers decaying vegetation and animal matter 2 Food drawn in by muscular pharynx 3 Food stored in crop 4 Moved to gizzard where it is ground 5 Digestion and absorption in intestine folded into a typlosole 6 Have yellowish chloragogen tissue to synthesize glycogen and fat 7 When cells are full they are released into coelom as exeocytes ii Circulation and respiration 1 Double transport system coelomic lfuid and circulatory fluid 2 5 main blood trunks through body 3 Dorsal vessel above the alimentary canal from pharynx to anus 4 Aortic arches maintain steady blood pressure in dorsal vessel 5 Single ventral vessel serves as aorta 6 Blood contains hemoglobin to carry o2 7 Gas exchange occurs over moist skin 8 Earthworm closed circulatory system iii Excretion 1 Almost all segments have metanephridia each on occupies parts of 2 separate segments 2 Ciliated funnel called a nephrostome leads to loops and then an opening called the nephridiophore which acts as a bladder 3 Wastes discharged to the outside through another nephridiophore 4 Aquatic species secrete waste as ammonia terrestrial species sometime use urea but can use a combo of both 5 Salts and water can pass across integument iv Nervous and sensory systems 1 Pair of cerebral ganglia act as brain 2 Double ventral nerve cord 3 Neurosecretory cells in brain perform endocrine function s 4 Posses giant axons in nerve cord very efficient signal transmission 5 Have some learning ability v Reproduction and development 1 Monoecious usually simultaneous hermaphrodites 2 Multiple sets of gonads 3 Clituellum secretes mucus that holds mating individuals together 4 Sperm travel by seminal grooves 5 Chitinlike cocoon forms around clitellum collects eggs sperm and albumin and where fertilization occurs 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 6 Cocoon slips off worm and seals young worms hatch out look like baby worms b Class Hirudinea leeches i True leeches ii 34 segments no setae anterior and posterior suckers iii Order Acathobdellida 27 segments setae on first 5 only a posterior sucker iv Order Branchiobdellida 14 segments no setae and an anterior sucker commensal or parasitic on crayfish v Most freshwater but there are plenty that are terrestrial in rainforest vi Hermaphroditic with a clitelliumm only during breeding season vii Form and function 1 Many individual leech segments marked by transverse grooves to make smaller rings 2 Septa in coelom reduced or absent spaces called lancunae 3 Crawl by pushing loops or body forward or swim by undulation 4 Many blood parasites but many eat decay 5 Gas exchange occurs through skin a few species have gills 6 10 17 pairs of nephridia plus coelomocytes 7 2 brains one anterior and with 6 pairs of ganglia the other posterior with 7 pairs of ganglia 8 21 pairs of segmental ganglia 9 Sensillae in the center of each ring for multiple types of sensation 10 Hermaphroditic cross fertilization sperm transferred by penis or hypodermic impregnation stab and trx sperm 11 Make cocoon for eggs like an oligochaete 12 Some have a true circulatory system but most use coelomic sinuses as blood vascular system 13 Leeches are used in medicine to suck bad blood out c Phylum Echiura i Echis viper or serpent oura tail ii 140 species of marine worms that burrow in mud sand or live in holes and crevices iii Found worldwide shallow to very deep iv Form and function 1 Sausage shaped body flattened extensible proboscis sometimes called spoon worms for 2 Ciliated groove leading to mouth 3 Used for extending out and searching for food most eat detritus 4 Cuticle and epithelium covered body wall 5 Coelom large digestive tract long coiled and complete 6 Gas exchange mostly in hindgut through cloacal irrigation breath through butt 7 Sexes separate fertilization external trochophore larval stage d Phylum Sipuncula i Sipunculus little siphon ii Peanut worms can contract into a peanut shape iii 250 species of marine benthic worms iv Shallow to very deep v Same habitats as echiurans some sipunculans make their own burrows by chemical and mechanical means vi Form and function 1 No segmentation or setae 2 Slender retractile introverted proboscis 3 Mouth at tip of crown of ciliated tentacles 4 Little known about feeding some detritivores and some deposit feeders 5 Walls of trunk muscular 6 Large fluid filled coelom 7 Digestive tract complete u shaped 8 One pair of large nephridia 9 Lacking Circulatory and respiratory system 10 Separate sexes sex cells released through nephridia sometimes asexual reproduction by fission e Origins or metaerism and the coelom i Ceolum evolved 1 Hydrostatic skeleton 2 Primitive circulatory fluid 3 Gamete storage for synchronous release 4 Thin large body to fit into small spaces ii Repeated segmentation metamerism 1 Everyone has own food digestive 2 Segmentation probably arose multiple times