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Vermes Linnaeus – 1st to propose a formal classification of all life on earth most invertebrates were lumped together as “vermes” = worms here we will use the term to refer to an assortment of animals (Many different Phyla) that share a similar wormlike body plan Some Worm Characteristics 1. elongate cylindrical body usually with head and sense organs at one end 2. all are invertebrate animals (doesn’t include snakes, eels, etc) 3. body plan more complex than in the “simple animals” described earlier most have all 4 major kinds of animal tissues most have well developed organ systems including: nervous system with simple ganglia for brain and double nerve cord digestive system Animals - Vermes; Ziser Lecture Notes, 2009 1 complete digestive tract with mouth at one end and anus at the other excretory system reproductive system many with respiratory systems 5. most move using a hydrostatic skeleton hollow body filled with fluid surrounded by muscle layers in body wall some glide on slime trails many different unrelated animal groups have these characteristics in common: Planarians (Platyhelminthes) Ribbon Worms (Nemertea) Gastrotrichs (Gastrotricha) Thread Worms (Nematoda) Horsehair Worms (Nematomorpha) Sand Worms (Polychaetes) Earth Worms (Oligochaetes) Velvet Worms (Onycophora) Peanut Worms (Sipuncula) Spoon Worms (Echiura) Beard Worms (Pogonophora) Priapulids (Priapulida) Horseshoe Worms (Phoronida) Arrow Worms (Chaetognatha) Acorn Worms (Hemichordata) Animals - Vermes; Ziser Lecture Notes, 2009 2 Planarians body is elongated, slender or leaf-like or long and ribbon-like still rely on diffusion for much exchange of gasses, nutrients and wastes range in size from fraction of an inch to almost 1’ long often brightly colored some marine forms have warning coloration poorly known in fossil record but possible trails have been found from 565MY may be first animal to have a head & tail may be first animal to have bilateral symmetry may be first animal to show directed movement mostly bottom dwelling aquatic forms mostly freshwater some are marine a few are even terrestrial (6 sp in US) have true organs each made of several different tissue layers sponges have various specialized cells but no true tissues or organs jellyfish and corals have 2 tissue layers and a Animals - Vermes; Ziser Lecture Notes, 2009 3 few simple organs have distinct head with concentration of sense organs pair of brainlike ganglia no rigid skeleton for muscles to act on two layers around body circular muscle longitudinal muscle epidermis is ciliated secretes mucous trail and uses cilia to glide on it land planarians can glide ~6’/hr Feeding & Digestion are mainly carnivores some are scavengers feed on small crustacea, nematodes, rotifers, insects mouth at the end of a muscular “prehensile” throatlike tube = pharynx Animals - Vermes; Ziser Lecture Notes, 2009 4 is NOT at front of animal some have more than one mouth & more than one pharynx can detect food at a distance by chemoreceptors entangle their prey in mucous wraps its body around prey secretes enzymes to help “predigest” prey sucks up bits of prey incomplete digestive tract in most mouth, no anus in intestine secrete enzymes which further digest prey in some planarians digestive tract is highly branched to distribute food throughout the animal undigested food is egested through mouth Excretion some have very simple respiratory system to remove some some wastes in most takes form of “flame cells” cupshaped area with tuft of flagella Animals - Vermes; Ziser Lecture Notes, 2009 5 beat of flagella resemble candle flame under microscope wastes and excess water diffuse into bulb flagella create current to send wastes through tube which opens to outside of the body Nervous System planarians were probably the first creatures to have a brain but a few primitive members have nerve net like cnidarians have pair of ventral nerve cords connected by ladder like interconnections head with simple brain-like ganglia head with sense organs: no eyes (=ocelli), 2 eyes or 100’s of eyes can’t form images, only detect light auricles for touch and chemical senses Reproduction many reproduce both sexually and asexually Asexual: a. Regeneration Animals - Vermes; Ziser Lecture Notes, 2009 6 turbellarians have considerable powers of regeneration eg. slicing and dicing experiments replacement of lost parts also to recover from long food shortage can survive for months by self digesting up to 90% of their body regenerated worms may be able to retain learning: taught planarian to run a maze cut in half and allowed to regenerate both new worms learned the maze quicker early researchers also reported learning by cannibalism but has never been repeated??? b. Fragmentation when alarmed they can break up into dozens of “blobs of slime” in a few hours each piece will become a new worm c. Fission pinch in half Animals - Vermes; Ziser Lecture Notes, 2009 7 some times produces a chain of zooids superficial resemblance to segmentation Sexual: most are monoecious (hermaphrodites) during breeding season each individual develops both male and female organs cross fertilization not self fertilization some with internal fertilization some with vaginas & penises usually open through common genital pore mating ritual resembles a fight each trying to get penis in genital pore of the other or sometimes just impales the other some without vagina use “hypodermic impregnation” fertilized egg is enclosed in coccoon which is attached by stalks to underside of stones or plants some marine species produce ciliated larva Animals - Vermes; Ziser Lecture Notes, 2009 8 Ribbon Worms (Phylum Nemertea) ~1000 species slender, very fragile ribbonlike worms often very brightly colored some white, red, yellow, green, purple most ~8” (<20 cm) but longest animal in existence is a nemertean = 180’ (60 M) long regardless of length most are <1” (23mm) wide almost all are marine found in every ocean; from surface to abyssal zone most are benthic; a few pelagic species fairly common on beaches; often inside dead shells resemble tangled mass of slimy string arctic ribbon worms commonly wash ashore by the billions a few are found in moist soil or freshwaters Animals - Vermes; Ziser Lecture Notes, 2009 9 (eg. Prosoma is common in fw ponds) they build slime houses they can tie themselves into inextricable knots or curl up into balls and secrete a covering of mucus around themselves general body plan similar to planarians Feeding carnivores eat earthworms, sea worms, small mollusks and any small soft bodied animal use eversible proboscis to stab prey often at front of proboscis is sharp pointed spear-like stylet that impales prey often tipped with poison “Nemertea” translates as “unerring one” refers to animals ability to very accurately shoot its long proboscis to capture prey sometimes impales with such force that it breaks off writhes for hours animal can grow a new one Animals - Vermes; Ziser Lecture Notes, 2009 10 in some the proboscis is a sticky lasso that coils around its prey proboscis (pharynx) is unusual because it is not connected to digestive tract in most ribbon worms have complete digestive tract with anus one way path from mouth to anus like snakes they can devour animals larger than themselves without food some can live up to 1 yr by self digesting like planarians most can shrink at will to < 1/3 their ordinary length Circulatory System true blood vascular system Reproduction Asexual a. some reproduce asexually by fragmentation some can break into 100’s of fragments each fragment can grow into a complete worm Animals - Vermes; Ziser Lecture Notes, 2009 11 b. regeneration some with great powers of regeneration like planarians Sexual most are dioecious (unlike flatworms) fertilized egg develops into ciliated larva some fragment in warm weather and reproduce sexually in colder weather Animals - Vermes; Ziser Lecture Notes, 2009 12 Horsehair Worms (Phylum Nematomorpha) 326 species; probably many more also called “hairsnakes” or “hairworms” worldwide distribution abundant in aquatic and moist environments free living as adults and parasitic as larvae adults mostly ~ 4” long, (~10 cm); very slender <0.1” dia range up to 3’ (100cm) (1-3mm) reddish or dark brown really do resemble the hair of a horses tail found in puddles after rain usually contorted into knots (also called gordion worms) in all types of freshwater habitats with good oxygen levels in old days were common in horse troughs once thought they were literally produced from horses hairs Animals - Vermes; Ziser Lecture Notes, 2009 13 in days past: every summer kids would pull hairs out of horses tail and place them in a jar of water put on window ledge in the sun watched and waited to see the “transformation” skin covered by cuticle secreted by epidermis adult does not feed has complete but degenerate digestive system but can absorb some nutrients through body wall simple nervous system with ganglia and nerve cord extending down trunk some have eyespot on head no circulatory, respiratory or excretory system Reproduction & Development dioecious distinguished by caudal end: gametes released through anus copulation in many species Animals - Vermes; Ziser Lecture Notes, 2009 14 male and female become tightly intertwined eggs laid on vegetation in water in long strands hatch into larva with spiny proboscis larval stages are all parasitic in many kinds of insects, esp grasshoppers, myriopods, crustaceans some bore into host; others are eaten by host then hatch out larvae absorb nutrients from host’s body cavity parasites stimulates host to seek water adults emerge only when host is in water adult then quickly become sexually active Animals - Vermes; Ziser Lecture Notes, 2009 15 Threadworms (Phylum Nematoda) = eel worms; round worms ~25,000 species; specialists estimate up to 500,000 sp a few fossils known; some in amber very common and diverse group but poorly known and difficult to identify very simple and highly adaptable design: long, threadlike cylindrical shape with few distinctive features visible difficult at first glance even to distinguish front from back end most are very small 100th of an inch to 1/5th inch (0.5-1.0mm) live in almost every habitat from arctic to tropics: ocean, hot springs, lakes, ponds, damp soil probably the most abundant animal on earth especially common in soil as numerous in soil as are arthropods Animals - Vermes; Ziser Lecture Notes, 2009 16 eg. est 6 M individuals in 1 ft3 of soil eg. upper 1” of rich soil may contain >1 Bill/acre virtually every soil sample will yield new species the animals discussed so far lacked any kind of body cavity organs when present were embedded in jelly-like secretion or simple tissue virtually all other major animal phyla have some kind of body cavity ‘tube within a tube’ body plan: allows an increase in size allows more elaborate lengthening and coiling of internal organs allows circulation of gasses, food and wastes in the absence of a circulatory system provides hydrostatic skeleton Body Wall secretes tough but flexible cuticle protects worms from abrasion in soil and sediment some have an elaborately sculpted cuticle Animals - Vermes; Ziser Lecture Notes, 2009 17 Movement unlike most wormlike animals they have only longitudinal muscle in body wall hydrostatic pressure in fluid filled body cavity maintains internal pressure and keeps body wall from collapsing body wall with a single layer of longitudinal muscles only produces whiplike or snake-like thrashing motion Feeding and Digestion all nematodes eat living cells eg. bacteria, fungi, plant & animal some are predators on unicellular life (many are also parasites) mouth is at front end of muscular pharynx leads to complete digestive tract and exits through anus near posterior end no muscles lining intestine - collapsed thin tube Nervous System Animals - Vermes; Ziser Lecture Notes, 2009 18 dorsal and ventral nerve cords controls dorsal and ventral muscle layers “brain” = nerve ring with ganglia around pharynx Senses especially chemoreceptors sometimes in head; or tail Excretory System simple excretory system a series of canals or similar to planarians no circulatory or respiratory system body fluids circulate nutrients, oxygen and wastes Reproduction usually dioecious with sexual dimorphism males distinct from females amoeboid sperm (no flagella) young go through several “juvenile” stages with molt at end of each one some can enter a state of arrested activity = cryptobiosis Animals - Vermes; Ziser Lecture Notes, 2009 19 makes them successful in seemingly unfavorable environments Animals - Vermes; Ziser Lecture Notes, 2009 20 Sand Worms (Phylum Annelida; Class Polychaeta) sand worms, bristle worms, fan worms, clam worms, etc 10,000 species; 2/3rds of all species in phylum mostly marine most 2-4” long (5-10 cm) ; some up to 10’ (3 M) often brightly colored live in crevasses, old shells, burrows some live in tubes they secrete or make with sand or shell deposit feeders, filter feeders, predators, scavengers, some have elaborate filtering structures eg feather dusters a few are planktonic important in marine food chains Body Form most long and wormlike Animals - Vermes; Ziser Lecture Notes, 2009 21 some with bizarre forms well developed segmentation seen in just a few other phyla: eg arthropods, chordates segments are separated by tissue = septae allows more efficient hydrostatic skeleton offers a way to achieve greater size: rather than increasing size of each organ; each organ is repeated in each segment most have chitinous bristles = setae repeated on each segment (ie. “bristle worms”) used as anchors while burrowing or to prevent capture some used for swimming or as protection or camoflage most have a distinct head with pharynx and chitinous jaws tentacles palps and sensory structures most have paired appendages on most segments Animals - Vermes; Ziser Lecture Notes, 2009 22 = parapodia used for locomotion respiration in some, parapodia modified into fans and mucous bags for feeding or to create water currents Movement body cavity is filled with fluid which serves as hydrostatic skeleton can also use parapodia alternately to crawl across surface or as fins to swim Feeding & Digestion free swimming polychaetes are mostly predators some with eversible pharynx with jaws in others the pharynx produces a suction to draw food into mouth sedentary polychaetes are filter feeders or deposit feeders complete digestive tract “tube within a tube” design Animals - Vermes; Ziser Lecture Notes, 2009 23 muscle layers surround tract and allow modification of tract into various structures: crop: food storage area gizzard: thick and muscular; helps physically break up food intestine: in some the first part of intestine is used for digestion; secretes digestive enzymes Respiration usually through parapodia some have paired gills on some segments Circulation double transport system for foods, gasses, wastes fluid filled coelom also circulatory system with heart & vessels and blood several pairs of aortic arches (=”hearts”) help to keep pressure up in ventral vessel foods, wastes and respiratory gasses are carried both in blood and in body fluid Nervous System Animals - Vermes; Ziser Lecture Notes, 2009 24 brain a pair of cerebral ganglia paired ventral nerve cords with pair of ganglia in each segment ladderlike connections in each segment Senses: eyespots eyes with retina and rod-like receptors a few polychaete eyes have cornea, lens, retina can form images statocysts in some tentacles & palps touch other simple chemoreceptors Excretion more elaborate excretory system than previous animals discussed excretory organs also help in salt and water balance Reproduction & Development most are dioecious Animals - Vermes; Ziser Lecture Notes, 2009 25 simple reproductive system have no permanent gonads gonads appear as temporary swelling of peritoneum at certain seasons gametes are shed either through genital ducts or through nephridiopore or through rupture in body wall some sand worms live most of the year as sexually immature individuals after living 1 or 2 years as benthic organisms they become sexually mature and swollen with gametes head shrinks, body enlarges, gonads develop and produce egg or sperm sometimes only part of the body makes the transformation, breaks off and the rest of the worm lives to repeat next season eg. palolo worm males and females gather by the millions in one spot at night determined by phases of the moon female releases pheromone pheromone excites male to circle about female Animals - Vermes; Ziser Lecture Notes, 2009 26 swarms of epitokes appear at start of moon’s last quarter in oct or nov sea is literally thick with epitokes just before sun rises, epitokes burst to release gametes anterior portion of worm returns to burrows =synchronous mating ensure most eggs are fertilized predator saturation predators have a field day; but too many prey so some are always left to reproduce atokes safely in their burrows to repeat next year a Samoan holiday to feast on epitokes Ecological and Economic Impacts eg. detritus food chains eg. prominent in marine food webs eg. human food (samoa) eg. beardworms are base of entire ecosystem not based on photosynthesis discovered in 1900; today 150 known species most live in deep ocean common in hydrothermal vent communities no digestive tract Animals - Vermes; Ziser Lecture Notes, 2009 27 they get most of their nutrients from symbiotic bacteria living in an organ (=trophosome) within the trunk of the worm bacteria harvest energy from H2S and convert inorganic elements into sugars for the worm CO2 + H2S + O2 + H2O H2SO4 + sugars have well developed circulatory system containing hemoglobin use hemoglobin to carry oxygen to body cells and to carry oxygen and hydrogen sulfide to bacteria eg. Major decomposers of deep sea whale carcasses 2001 found red fuzz on whale carcasses in deep ocean 1000’s of polychaetes with red plumes up to 6 cm long new genus and species of polychaete seem to be unique to “whale fall” worms have no functional mouth or gut have symbiotic bacteria that digested oil in bones they degrade hydrocarbons the bacteria live in rootlike structures of worm that extend in and throughout the bone worm provides oxygen via blood vessels extending into the roots Animals - Vermes; Ziser Lecture Notes, 2009 28 Earthworms (Phylum Annelida; Class Oligochaeta) means “few setae” over 3000 species mostly terrestrial; most abundant ‘worms’ on land burrow in the soil most are less than ~1’ (30 cm) some tropical earthworms get up to 9’ (3 M) long relatives of sand worms but no parapodia and very few setae no distinct head earthworms have no “eyes” but do have numerous photoreceptors in epidermis Feeding & Digestion most are detritus feeders and scavengers on decaying organic matter well developed digestive tract: mouth pharynxesophagusgizzardintestine anus Animals - Vermes; Ziser Lecture Notes, 2009 29 pharynx - pumps food in crop - temporarily stores food gizzard - muscular, lined with cuticle, grinds food intestine - most chemical digestion and absorption allows them to eat soil and then the intestine sorts out the nutrients for absorption eat as they burrow then let digestive system extract nutrients eg. Night Crawler burrow within the upper 30 cm of moist soil rich in organic matter mainly active at night on warm damp nights, forage for leaves and organic debris up to 54,000 earthworms /acre turn over 18 tons of soil per year prefer moist soil but if too much water they will move to surface sometimes in great numbers used to think they “rained” down from the sky important in keeping soil fertile since they are constantly turning over earth and mixing organic matter into it Animals - Vermes; Ziser Lecture Notes, 2009 30 if all material ever moved through earthworm gut was piled on surface of earth it would rise 30 miles above sea level (5x’s height of Mt Everest) Respiration no respiratiory organs or parapodia like polychaetes breath through skin, no lungs or gills extensive system of capillaries beneath cuticle Circulation have circulatory system with 5 pairs of hearts and hemoglobin in blood to carry oxygen Excretion main excretory organs are nephridia in each body segment Nervous System same as sand worms Sense Organs distributed all over body photoreceptors Animals - Vermes; Ziser Lecture Notes, 2009 31 chemoreceptors many free nerve endings probably tactile Earthworm Reproduction earthworms are hermaphrodites cross fertilize each other copulation involves a double exchange of sperm cells mucous secreted from clitellum holds pair together with genital pores aligned can last 2-3 hours sperm is deposited in seminal receptacle after copulation worms return to burrows fertilization and egg laying occur a few days later each worm secretes a sheath of mucous around clitellum clitellum then secretes nourishment for egg then envelopes mucous and food in tough chitin-like cocoon Animals - Vermes; Ziser Lecture Notes, 2009 32 the worm then backs out of the cocoon as cocoon slips over the genital openings it receives an egg, then sperm fertilization occurs in the cocoon cocoon is deposited in soil in 2-3 weeks a new worm emerges Ecological and Economic Impacts detritus food chain food for birds and other animals bait soil fertility important in keeping soil fertile since they are constantly turning over earth and mixing organic matter into it if all material ever moved through earthworm gut was piled on surface of earth it would rise 30 miles above sea level (5x’s height of Mt Everest) Animals - Vermes; Ziser Lecture Notes, 2009 33 Velvet Worms (Phylum Onycophora) 70 species closely related to arthropods an ancient phylum has changed little since the Cambrian (500MY) cylindrical segmented body 0.5-6” (1.4-15 cm) long blue, green, orange or black originally a marine animal (Burgess Shale) today all are terrestrial found in rainforests and semitropical habitats mostly nocturnal tend to avoid light Body Form long cylindrical segmented, wormlike body entire body is covered by bumps (=tubercles) which are covered by tiny scales Animals - Vermes; Ziser Lecture Notes, 2009 34 giving the body a velvet appearance have 14-23 pairs of legs each leg has a pair of claws looks like slugs with legs thought to be a mollusc when first discovered in 1826 anterior end with pair of antennae and ventral mouth believed to be a phylum closely related to arthropods Movement fluid filled body cavity is used as hydrostatic skeleton crawls slowly on peglike legs Feeding & Digestion well developed digestive system mouth with a pair of claw like mandibles most species are predaceous feed on snails insects and worms Animals - Vermes; Ziser Lecture Notes, 2009 35 have slime glands that shoot milky fluid that quickly congeals into slime can shoot slime up to 30” once captured they secrete enzymes (salivary secretions) into prey to partially digest it before eating Animals - Vermes; Ziser Lecture Notes, 2009 36