Phylum Annelida (segmented worms, bristle worms) some live in tubes they secrete or make with sand or shell 15,000 species Body Form large successful phylum in water & on land most are long and wormlike with head-body-pygidium include , sand worms, bristle worms, clam worms, fan worms, leeches some with bizzare forms worldwide distribution: head (prostomium & peristomium)

marine, brackish, freshwater and terrestrial most show some degree of cephalization with a distinct head (=prostomium) elongated wormlike body tentacles, palps and sensory structures new body design: hollow tube-within-a-tube peristomium behind prostomium contains the true coelom present mouth

mesoderm on inside of body wall and outside of with pharynx and chitinous jaws digestive system body with well developed metamerism one of the most successful designs (=segmentation)

! room for development of complex organs most prominent distinguishing feature

with muscle layers seen in just a few other phyla: eg arthropods, chordates

! allows for circulation of body fluids segments are separated by tissue = septae

! provides hydrostatic skeleton allows more efficient hydrostatic skeleton

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 1 : Phuylum Annelida; Ziser Lecture Notes, 2012.10 2

offers a way to achieve greater size: epidermis secretes a thin flexible cuticle and setae

rather than increasing size of each organ setae ! small chitinous bristles

! each organ is repeated in each segment most annelids have setae

the segmentation is both external and internal repeated on each segment (ie. “bristle worms”)

essential features of segmentation: used as anchors while burrowing

several systems (eg. nervous, excretory) show serial repetition to prevent capture

segmentation is produced during embryonic development some used for swimming

NOT the same as asexual budding as in tapeworms or as protection or camoflage most annelids have paired appendages on most segments beneath epidermis is two layers of muscle tissue = parapodia

thin layer of circular muscle used for locomotion

thick layer of longitudinal muscle (obliquely respiration striated)

in some, parapodia modified into fans and mucous body cavity of true coelom bags for feeding or to create water currents

lined with peritoneum (squamous epithelium) terminal pygidium with anus

lines inside of body wall & outside of digestive Body Wall tract

epidermis a single layer of cells (columnar epithelium) peritoneum also form mesenteries that hold Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 3 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 4 blood vessels and the septae between parapodia help in polychaetes segments

Movement Feeding & Digestion coelom is filled with fluid (except leeches) which serves complete digestive tract “tube within a tube” design as hydrostatic skeleton muscle layers allow modification of tract into annelids have 3 general types of movements: various structures:

1. burrowing: pharynx with teeth

esophagus waves of peristaltic contractions sweep down body crop

st gizzard 1 animal elongates !contraction of circular muscle

nd intestine 2 animal sortens ! contraction of longitudinal muscle

setae anchor hind end of body while front end mouth beneath prostomium pushes foreward some with eversible pharynx with jaws 2. crawling: in others the pharynx produces a suction to draw polychaetes use parapodia alternately to move food into mouth across surface crop: food storage area 3. swimming: gizzard: thick and muscular mainly polychaetes and leeches helps physically break up food undulating body movements intestine Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 5 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 6

most annelids also have circulatory system that helps in t in some the first part of intestine is used for ransport of materials digestion closed circulatory system secretes digestive enzymes dorsal and ventral vessel connected by capillary most of intestine is used for absorption network

on dorsal surface is infolding = typhlosole dorsal vessel pumps blood anteriorly

ventral vessel pumps blood posteriorly increases surface area for absorption dorsal vessel is main pump lining intestine are yellowish chloragogue cells several pairs of aortic arches (=”hearts”) help to ! equivalent to our liver: synthesizes glycogen and fats keep pressure up in ventral vessel

! they also travel through coelom to repair wounds thus a double transport system for foods, gasses, wastes ! function in excretion: convert amino acids to urea & ammonia fluid filled coelom Respiration

circulatory system with heart & vessels through body wall

foods, wastes and respiratory gasses are carried both some through parapodia in blood and in coelomic fluid

a few have gills blood:

Circulation most with dissolved blood pigments to carry

oxygen: body cavity is filled with coelomic fluid which helps mive food and wastes around hemoglobin (Fe) red - most annelids hemerythrin (Fe) red chlorocruorin (Fe) green Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 7 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 8 other simple chemoreceptors (only 4 blood pigments known & annelids have 3 of them)

blood also contains amoeboid cells which engulf free nerve endings ! tactile?? foreign particles Endocrine System Nervous System simple endocrine system brain a pair of cerebral ganglia neurosecretory cells in ganglia leeches have another pair of ganglia at posterior end hormones regulate reproduction and regeneration paired ventral nerve cords Excretion with pair of ganglia in each segment one pair of nephrida (=metanephridia) in each segment ladderlike connections in each segment similar to that in molluscs Senses: (a few polychaetes have protonephridia or both) simple single celled photoreceptors or clusters of cells = eyespots nephric tubule:

nephrostome = funnel like opening into previous segment eyes with retina and rod-like receptors coiled ciliated tubule surrounded by capillaries a few polychaete eyes have cornea, lens, retina ! can form images bladder like structure

statocysts in some nephridipore = opening to outside

function: nuchal organ ! chemoreceptors

wastes from coelom are drawn in tentacles & palps ! well devleoped sense of touch

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 9 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 10

salts and organic wastes from blood are discharged into duct Sexual

useful stuff is selectively reabsorbed monoecious or dioecious

in earthworms and leeches chlroagogue cells larva, if present = trochophore collect NH4 or urea and deposit in blood or take directly to nephrostome some nitrogen wastes are also excreted through body wall excretory organs also help in salt and water balance in earthworms, calciferous glands along esophagus secrete excess calcium from blood into digestive tract

(lots of calcium in soil; lots gets absorbed, excess is secreted)

Reproduction and Development both asexual and sexual reproduction

quite variable within the phylum

Asexual

most can bud to some degree

other spontaneously fragment

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 11 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 12 Classification of Annelida Class: Polychaeta Class: Polychaeta (Sand Worms)

mostly marine means “many setae”; also called bristle worms distinct head with eyes and tentacles largest, most diverse and most primitive class of Annelids segments with parapodia and lots of setae

no clitellum 10,000 species; 2/3rds of all species

Class: Oligochaeta sand worms, bristle worms, fan worms, clam worms,

mainly terrestrial and freshwater etc

head absent mostly marine

fewer setae, no parapodia a few found in freshwater Class: Branchiobdellida most 5-10 cm long; some up to 3 m commensal on crayfish

no setae often brightly colored

posterior sucker only deposit feeders, filter feeders, predators, scavengers,

Class: Hirudinea live in crevasses, old shells, burrows or construct tubes terrestrial, freshwater or marine

no parapodia or setae some have elaborate filtering structures

fixed # of segments with “false segments” eg feather dusters

anterior and posterior suckers a few are pelagic ! part of the plankton

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 13 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 14

important in marine food chains both parapodia and setae are moved by internal Body Plan muscle bands distinct head with mouth and sense organs most sand worms and relatives move by crawling using appendages (parapodia) wormlike body with repeating segments as “legs”

body segments with flaplike parapodia other swim using them as paddles for swimming Head parapodia also serve as main respiratory organ have distinct head in some the anterior parapodia are modified into head has retractable pharynx with jaws used to fan-like structure to filter the water capture prey Feeding & Digestion lots of different kinds of sense organs on head free swimming polychaetes are mostly predators 1. chemoreceptors (nuchal glands) on palps and tentacles

2. touch receptors also on tentacles for locating food and sedentary polychaetes are filter feeders or deposit shelter feeders

3. eyes foregut: pharynx and jaws, esophagus some can focus an image = esp predators lined with cuticle very similar to cephalopod and vertebrate eyes

Body or Trunk midgut: secretes digestive enzymes

most body segments have appendages in posterior section absorbs nutrients = parapodia with setae hindgut: anus Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 15 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 16

Respiration basic annelid plan usually through parapodia dorsal ganglia some have paired gills on some segments double ventral nerve cords with paired ganglia in each segment some have no special organ and exchange across body surface Senses:

Circulation eyes: simple eyespots to complex organs lots of variation esp in free moving (errant) polychaetes some open some closed circulatory systems in one group can form image: cornea, lens, retina may have respiratory pigments nuchal organs: ciliated sensory pits eg. hemoglobin, chlorocruorin, hemerythrin

Excretion chemoreceptors used in food gathering protonephridia and in some metanephridia or both statocysts in burrowers and tube building forms

1 pair per segment Reproduction & Development opens into coelomic compartments most are dioecious tubule absorbs any useful materials and concentrates simple reproductive system wastes as fluid passes to nephridiopore have no permanent gonads Nervous System ! gonads appear as temporary swelling of Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 17 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 18

peritoneum at certain seasons anterior portion of worm returns to burrows gametes are shed either =synchronous mating

! through genital ducts !ensure most eggs are fertilized

! or through nephridiopore !predator saturation predators have a field day; but too many prey so ! or through rupture in body wall some are always left to reproduce some polychaetes live most of the year as sexually !atokes safely in their burrows to repeat next year immature individuals = atokes a Samoan holiday to feast on epitokes after living 1 or 2 years as benthic organisms they become sexually mature and swollen with gametes = epitokes

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

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

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 19 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 20 Examples of Polychaetes front with great mass of long red hairlike filaments used as gills eg. clam worm or sand worm (Nereis) eg. Blood Worms (Glycera) up to 10” long red worms, all marine, several species live in mucus tubes in or near low tide eg. Sedentary Polychaetes males - iridescent bluish-greenish color many polychaetes burrow or live in tubes rather females - light green with yellow, orange-red than crawling around on the sediment mottling often develop various food gathering structures for most active at night filter feeding

move out onto sand to search for food leads to tagmosis ! fusion and reduction of metamerism

can also swim by undulatory movements eg. Sabella (tubeworm)

eg. Chaetopterus (parchment worm) they are predators secretes parchment like tube use their jaws to capture small animals tubeworm must maintain a flow of water to get oxygen jaws open as pharynx is everted and get rid of wastes

jaws close as pharynx is retracted ! uses modified parapodia as paddles eg. Tangleworms (Cirratulus grandis) can emit strong bioluminescent flashes

on east and west coasts of US burrows often shared by commensal crab

eg. Fanworms, tubeworms, featherduster worms) yellow to green; 5-6” long secrete many kinds of tubes: firm calcareous tubes Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 21 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 22

glue sand grains together bits of shell cemented together thin, transparent, segmented trunk has several some burrow pairs of setae and is enclosed in a chitinous may extend long tentacles out of tube to filter particles tube from the water

the trunk ends in a small segmented eg. Scale Worms opisthosoma

very abundant the best known of the group are the giant tubeworms

found around deep sea hydrothermal vents flattened and coverd with scales formed by the

modified parapodium some up to 6’ long,

most are small; some up to 19 cm a red plume that extends from the tube

carnivores; bright red ! hemoglobin in blood

many are commensals with other marine inverts used to absorb nutrients from the water

eg. Beard Worms (pogonophorans) & Giant Tube ! tubeworms have no mouth, stomach Worms

once thought to be a separate phylum, now known to be an unusual their trunk contains a large sac (trophosome) kind of polychaete that is filled with symbiotic bacteria

discovered in 1900; today 150 known species Feeding

all are marine only non-parasitic animals without a digestive tract most live in bottom ooze of deep ocean no mouth, anus or digestive tract in many the forepart bears long tentacles giving it a bearded appearance Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 23 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 24 they get most of their nutrients from symbiotic the larvae will drift through the deep water until bacteria living in an organ (=trophosome) they locate a hydrothermal vent within the trunk of the worm they will then settle to a rocky perch

bacteria harvest energy from H2S and convert inorganic elements into sugars for the worm the young tubeworms do have a mouth and gut and feed

CO2 + H2S + O2 + H2O ! H2SO4 + sugars as the worm matures the muth and gut have well developed closed circulatory system degenerate and the area once holding the containing hemoglobin digestive systems becomes a bacteria filled sac use hemoglobin to carry oxygen to body cells and to carry oxygen and hydrogen sulfide tube worms seem to have few predators to bacteria although sometimes crab and shrimp will feed on reproduction the worm’s red plume

usually sexual

dioecious

male releases packet of sperm into water

females release eggs into the water

fertilization produces a worm shaped embryo

poor swimmer; probably carried by water currents

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 25 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 26

Ecological and Economic Impacts of Polychaetes seem to be unique to “whale fall”

worms have no functional mouth or gut eg. detritus food chains have symbiotic bacteria that digested oil in bones eg. prominent in marine food webs ! they degrade hydrocarbons eg. beardworms entire ecosystem not based on the bacteria live in rootlike structures of worm that extend in and photosynthesis throughout the bone

worm provides oxygen via blood vessels extending into the roots discovered in 1900; today 150 known species

most live in deep ocean eg. human food (samoa) !common in hydrothermal vent communities eg. insecticides no digestive tract

eg. Padan – a powerful insecticide produced from a polychaete worm they get most of their nutrients from symbiotic bacteria living in

an organ (=trophosome) within the trunk of the worm eg. anticancer drugs

bacteria harvest energy from H2S and convert inorganic elements into sugars for the worm eg. dolastatins from sea hare (Dolabella auricularia) has potential anticancer properties 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

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 27 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 28 Class Oligochaeta (Earthworms) segments contain pores for coelomic fluid to leak out and lubricate outer surface of animal means “few setae” also has numerous mucous glands over 3000 species Feeding & Digestion mostly terrestrial; most abundant ‘worms’ on land most are scavengers on decaying organic matter !burrow in the soil mainly burrowers also many live in freshwaters eat as they burrow then let digestive system and a few marine or brackish extract nutrients most are less than 30 cm (~1’) well developed digestive tract:

mouth! pharynx!esophagus!gizzard!intestine! anus some tropical earthworms get up to 3 M long pharynx - pumps food in relatives of sand worms but no parapodia crop - temporarily stores food gizzard - muscular, lined with cuticle, grinds food intestine - most chemical digestion and absorption and very few setae allows them to eat soil and then the intestine sorts most with 4 prs of setae/segment out the nutrients for absorption no distinct head typhlosole in intestine improves absorption of nutrients Body Wall chloragogue cells surround outside of intestine protective layer of collagenous cuticle secreted by epidermis store nutrients

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 29 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 30

synthesize glycogen and fats in aquatic forms nephridia release ammonia

cells break off and deliver fats through coelom to other organs in terrestrial forms nephridia release urea (conserves water) in body in fw and terrestrial oligochaetes nephridia not only eliminate some metabolic wastes eliminate wastes but also eliminate excess water (osmoregulation) Respiration also, terrestrial worms have calciferous glands no respiratiory organs or parapodia like polychaetes worms eat soil; soil has lots of calcium breath through skin, no lungs or gills high levels of calcium in blood extensive system of capillaries in epidermis calciferous glands remove excess calcium from blood Circulation and deposit it in the intestine for removal double circulatory system: Nervous System

coelomic fluid have both CNS and PNS

closed pumping system CNS: cerebral ganglia and ventral nerve cord have circulatory system with 5 pairs of hearts with paired fused ganglia in each segment

and hemoglobin in blood to carry oxygen PNS: nerves branch off fused ganglia to supply body wall and body organs Excretion Sense Organs main excretory organs are nephridia rather than concentrated in head they are distributed paired nephridia in each body segment all over body

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 31 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 32 together with genital pores aligned numerous sensory cells (chemo- and mechano- receptors) on skin can last 2-3 hours

chemoreceptors esp on prostomium sperm is deposited in seminal receptacle

many free nerve endings ! probably tactile after copulation worms return to burrows earthworms have no “eyes” but do have numerous photoreceptors in epidermis fertilization and egg laying occur a few days later

Endocrine System each worm secretes a sheath of mucous around clitellum neurosecretory cells in brain and ganglia clitellum then secretes nourishment for egg secrete hormones that regulate: then envelopes mucous and food in tough reproduction chitin-like cocoon

secondary sex characteristics the worm then backs out of the cocoon

regeneration as cocoon slips over the genital openings it

receives an egg, then sperm Reproduction

fertilization occurs in the cocoon earthworms are hermaphrodites

cocoon is deposited in soil cross fertilize each other

in 2-3 weeks a new worm emerges copulation involves a double exchange of

sperm cells

mucous secreted from clitellum holds pair

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 33 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 34

Examples of Oligochaetes spits at predators eg. Aquatic “Earthworms” eg. ice worms

smaller, benthic, longer setae, more active small worms <1” long

better developed sense organs only found on surface of glaciers at temperatures below freezing (~7ºC), they die at temperatures of 5ºC or more some have gills can appear by the 100’s

generally eat algae and detritus eat algae and pollen

some with great powers of asexual reproduction ! budding eg. tubifex

red worms to 10 cm long

live on bottoms of lakes, ponds and polluted streams

live in very low oxygen concentrations

have large amounts of hemoglobin

keep their heads in tubes while waving bright red tails

in heavily polluted areas banks appear bright red at low water

absorb dissolved nutrients (DOM) across skin eg. giant earthworm

in

thought extinct but recently rediscovered

up to 3 ft long, lives in burrows 15’deep

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 35 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 36 Ecological and Economic Impacts in some parts of Asia, Africa and Latin America people regularly eat worms 1. Detritus food chain usually because there is not much other food available eg. Night Crawler a few restaurants in the US offer them as novel food fare burrow within the upper 30 cm of moist soil rich in organic matter 4. Fishing bait in soft soil earthworms move by peristaltic contractions worms are commonly used for freshwater fishing setae prevent back sliding

this type of movement only works because segments are separated by septa

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

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)

2. Food for birds and other animals

3. Food for Humans Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 37 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 38

Class Hirudinea coelom is filled with connective tissue and muscle

Leeches) ( except for a system of spaces (=coelomic sinuses and channels) filled with coelomic fluid 500 sp probably should be in same class as oligochaetes ! acts as secondary circulatory system mainly freshwater Movement

a few marine and terrestrial no parapodia (except 1 genus) most 2-6 cm long; some to 20 cm no setae often brightly colored leeches have poor hydrostatic skeleton many are carnivores; some are parasites aquatic species use muscle layers to make undulating body is dorsoventrally flattened swimming movements anterior and posterior suckers can also use suckers to move like inchworms fixed number of true segments some terrestrial forms are able to “stand up” on hind sucker to search for prey ! usuall 32 plus prostomium & pygidium Feeding & Digestion each segment with 2-14 annuli (=false segments) most are predators of snails, worms and insect larvae Body Wall protrusible pharynx with 3 jaws armed with teeth coelom functions as a single large chamber ! no septae between segments some are scavengers

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 39 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 40 some are blood sucking parasites Circulation

adaptations to parasitism by leeches: many species have no blood vessels

attach to host with suckers coelomic fluid does the work of blood in open

pierce skin with sharp teeth on end of proboscis haemocoel

while cutting, secrete local anesthetic and histamine-like may be hemoglobin in haemocoel fluid chemical that dilates blood vessels of host

consume large blood meals Nervous System

!blood is sucked by muscular pharynx nervous system similar to other annelids

while being swallowed, blood mixes with hirudin (anticoagulant) to prevent clotting but leeches have two “brains” very slow digestion ! one composed of paired cerebral ganglia around pharynx as in other annelids

gut secretes very few digestive enzymes ! the other in posterior of animal consists of 7 pairs of fused ganglia !depend on bacterial digestion simple sense organs are much better developed in can live for almost a year on one meal terrestrial species which tend to be blood suckers

may take up to 200 days to digest one meal Excretion

can live for another 100 days afterwards 10-17 pairs of nephridia Respiration Reproduction most exchange gasses through skin hermaphroditic a few aquatic forms have gills ! cross fertilize during copulation

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 41 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 42

Human Impacts mating process similar to earthworms 1. medicinal uses do have clitellum in past centuries medicinal leech, Hirudo, was used to !produce coccoon that receives eggs and sperm suck out “bad blood”

believed many bodily disorders were the result of bad blood or too much blood

! were collected almost to extinction in Europe

now a protected species

introduced into US but rare in nature

today leeches used in medicine to speed healing of reattached fingers and limbs

2. commonly used in biology labs

3. leeches have become leading research models for understanding how the nervous system works

4. some chemicals used by the leech in obtaining and digesting blood are being studied for treating circulatory diseases

5. leeches have also affected history:

eg. land leeches of India

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 43 Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 44 live in extremely large numbers in humid forests of India

live in trees and shrubs and fall like “drops of dew” onto any humans passing underneath

their mass attack caused the retreat of a British regiment during the Sikh rebellion in India in mid 1850’s!

Animals: Phuylum Annelida; Ziser Lecture Notes, 2012.10 45