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Vermes (Worms) with various sense organs to inspect and evaluate the environment Linnaeus – 1st to propose a formal classification of all life on earth the elongated shape also allows the animal to fit into cracks and crevices and to easily burrow through à most invertebrates were lumped together the sediment as “vermes” = worms in most worms the mouth is also at the front end of here we will use the term to refer to an assortment of the animal animals (Many different Phyla) that share a similar wormlike body plan worms are poorly known in the fossil record but “trace fossil” such as burrows & trails have been found 1. elongate cylindrical body from 565MY ago à probably were the first kind of animals that 2. all are invertebrate animals moved (ie. were not sessile) (doesn’t include snakes, eels, etc) à may be first animal to have a head & tail 3. here we are only including those in which the adults are free –living today worms occur in almost every kind of habitat from arctic to tropics: ànot worms that are parasites ocean, hot springs, lakes, ponds, soil, ice, etc the worm-shaped body is one of the most common, versatile and adaptable forms in the animal live in crevasses, old shells, burrows or self kingdom constructed tubes it allows for a distinct “front end” or head most worms live in or on the bottom sediment in marine and freshwater habitats, or in soil on land since the head is the part of the body that meets the environment first it is usually equipped most worms are microscopic to several inches Animals - Vermes; Ziser Lecture Notes, 2017.5 1 Animals - Vermes; Ziser Lecture Notes, 2017.5 2 but the longest animal in existence is a ribbon Acorn Worms (Hemichordata) worm = ~180’ (60 M) long Movement as a group worms are probably the most abundant most worms have a muscular body wall with 2 animals on earth layers of muscles: eg. est 6 M individuals in 1 ft3 of soil circular and longitudinal muscles eg. upper 1” of rich soil may contain >1 Bill/acre allows worm to both constrict and elongate the à virtually every soil sample will yield new body by contracting against a fluid filled body species cavity in the ocean worms are also probably the most abundant animal in and on the sediment =hydrostatic skeleton many worms are brightly colored some have pairs of stubby legs or flaps that help them some white, red, yellow, green, purple to move, swim, crawl, and dig today many different unrelated animal groups have Feeding & Digestion these wormlike characteristics in common: most worms have a complete digestive tract Ribbon Worms (Nemertea) Gastrotrichs (Gastrotricha) Thread Worms (Nematoda) with both a mouth and an anus Horsehair Worms (Nematomorpha) Sand Worms (Polychaetes) à one way path from mouth to anus Earth Worms (Oligochaetes) Velvet Worms (Onycophora) much more efficient than the digestive sac of corals Peanut Worms (Sipuncula) jellyfish & planarians Spoon Worms (Echiura) Beard Worms (Pogonophora) Priapulids (Priapulida) worms feed in a variety of ways: Horseshoe Worms (Phoronida) Arrow Worms (Chaetognatha) a. carnivores Animals - Vermes; Ziser Lecture Notes, 2017.5 3 Animals - Vermes; Ziser Lecture Notes, 2017.5 4 b. scavengers & deposit feeders c. filter feeders usually have two nerve cords extending from the ____________ simple brain down the length of the body from the mouth, food moves into the digestive tract often with ladder-like interconnections the complete digestive tract is typically modified into a head usually contains several sense organs: variety of specialized structures: simple eyes (=ocelli) pharynx – surrounded by muscles to pumps food in most can’t form images, only detect light crop: food storage area a few polychaete eyes have cornea, lens, retina gizzard: thick and muscular; helps physically break up food à can form images intestine: the first part of intestine is used for chemical chemical receptors digestion; secretes digestive enzymes eg. planarians have auricles for touch and chemical senses the remainder is used for absorption on the sides of their head Circulatory System balance organs (=statocysts) most worms have a true closed circulatory system tentacles & palps à touch with a pumping heart and blood to carry oxygen and protect from pathogens Nervous System worms were probably the first creatures to have some semblance of a “brain” very simple brain-like ganglia in head mostly reflex responses, no higher processing Animals - Vermes; Ziser Lecture Notes, 2017.5 5 Animals - Vermes; Ziser Lecture Notes, 2017.5 6 use eversible proboscis (=pharynx) to capture eg. Ribbon Worms prey slender, very fragile ribbonlike worms often at front of proboscis is sharp pointed spear- like stylet that impales prey most <20 cm(~8”) often tipped with poison some of the longest known animals, up to 180’ eat earthworms, sea worms, small mollusks and regardless of length most are <1” (23mm) wide any small soft bodied animal almost all are marine “Nemertea” translates as “unerring one” they build slime houses: curl up into balls and secrete à refers to animals ability to very accurately shoot its long proboscis to capture prey a covering of mucus around themselves sometimes impales with such force that it breaks fairly common on beaches; often inside dead off shells writhes for hours; animal can grow a new one à resemble tangled mass of slimy string like snakes they can devour animals larger than themselves arctic ribbon worms commonly wash ashore by the billions have complete digestive tract with anus often very brightly colored without food some can live up to 1 yr by self digesting like planarians some white, red, yellow, green, purple most can shrink at will to < 1/3 their ordinary length a few are found in moist soil or freshwaters ribbon worms reproduce both asexually and sexually ribbon worms are carnivores Animals - Vermes; Ziser Lecture Notes, 2017.5 7 Animals - Vermes; Ziser Lecture Notes, 2017.5 8 some reproduce asexually by fragmentation eg. Horsehair Worms can break into 100’s of fragments also called “gordion worms” or “hairworms” each fragment can grow into a complete worm adults are free living and abundant in aquatic and moist environments have a circulatory system and simple excretory system àworldwide distribution have a nervous system with brain and nerve cord often found in puddles after rain usually contorted into knots sexually, most are dioecious in old days were common in horse troughs some fragment in warm weather and reproduce sexually in colder weather once thought they were literally produced from horses hairs in days past: Human Impacts of Ribbon Worms 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 one species found near San Francisco is blamed for watched and waited to see the “transformation” the collapse of the dungeness crab fishery long thin dark reddish-brown it eats about half of the egg production of the crab really do resemble the hair of a horses tail population other coastal nemerteans have devastated clam beds have digestive and nervous systems and a few sense organs In South America a couple of species are sold as fish bait (locals call them “tapeworms”) Animals - Vermes; Ziser Lecture Notes, 2017.5 9 Animals - Vermes; Ziser Lecture Notes, 2017.5 10 Threadworms (Round Worms) à anywhere there is organic matter = eel worms; round worms have been found in deep ocean trenches and in hot springs & ice long, threadlike cylindrical shape, tapered at both ends, with few distinctive features visible the deepest living animal known is a nematode that lives in fractured rock 0.8 miles deep difficult at first glance even to distinguish front from back à almost 3 times deeper than any other animal most are very small 100th of an inch to 1/5th inch (its DNA was found >2 miles below ground) most are colorless or transparent threadworms are especially common in soil very common and diverse group but poorly known as numerous in soil as arthropods nematodes may actually be second only to arthropods eg. est 6 M individuals in 1 ft3 of soil in number of species eg. upper 1” of soil may contain <1 Bill/acre over two hundred species have been found in a spoonful of beach mud eg. 3.5M/m2 in tundra soils to 9M/m2 in grassland soils in terms of sheer numbers, nematodes are probably à virtually every soil sample will yield new the most abundant animal on earth species à 4 of every 5 animals on planet are nematodes à 90,000 nematodes were found in a single rotting apple occur in virtually all habitats from arctic to tropics; marine, freshwaters, and especially in soil there is virtually no part of the biosphere that doesn’t harbor nematodes Animals - Vermes; Ziser Lecture Notes, 2017.5 11 Animals - Vermes; Ziser Lecture Notes, 2017.5 12 à some can survive mercuric chloride solutions that would “If all the matter in the universe except the kill most other animals nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied à only living organisms to survive a space shuttle explosion spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and eg. 6 canisters of C. elegans survived the Columbia oceans represented by a thin film of nematodes. disaster The location of towns would be decipherable, since for every massing of human beings there would be allows them to survive in many unusual habitats a corresponding massing of certain nematodes. Trees would still stand in ghostly rows eg. hot springs representing our streets and highways.

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