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BIOL 3454:Chapter 17
phyla, order, classes, & representatives in ch, 17
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Phylum: Annelida
>Polychaeta ----- Nereis, ScaleWorms, FireWorms, TubeWorms
>Siboglinidea ("beardworms")
>Oligochaeta ("the worms")
>Hirudinea ("the leeches")
+Order Hirudinea
+Order Acanthobdellida
+Order Brachiobdellida
Phylum: Echiura & Phylum: Sipuncula
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Annuli
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Rings within phylum annelida
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Setae
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Chitinous bristles that some annelids have
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# of body layers anong annelis
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3, thus annelids are triploblatic
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They have a cuticle secreted by...
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The epithelium, which secretes a MOIST CUTICLE
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Annelus
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Latin root for "little ring"
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Annelid reproduction is ____ done by ____ & ____.
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Asexual, by fission & fragmentation.
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They typically have a pair of ____ per segment for waste removal.
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Kidney like organs
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Characteristic of their circulatory system...
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They have a CLOSED circulatory system.
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Terminal portion of their body is called a...
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Pygidium
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Location of the newest and oldest segments.
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Newest segments at END of body.
Oldest segments at FRONT of body.
***(opposite if the tapeworm)
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Each segment of annelids usually has its own....
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Circulatory, respiratory, nervous, and excretory structures.
***except for leeches, whose coleom is filled with fluid to make a hydrostatic skeleton***
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Greek roots: polys & chaite
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Many/hair
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There are three major annelid classes: Name them
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>Class Polychaeta are the polychaetes worms
>Class Oligochaeta are the earthworms offland and freshwater habitats
>Class Hirudinea are the leeches.
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Habitats of the worms in the class Polychaeta
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They live under rocks, in crevices, shells, in sediment, a few planktonic
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Polychaete
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Marine Annelids that have paired paddle like appendages (parapodia) tipped with setae
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Polychaete head parts
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well differentiated, with good sense organs...many settae
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Prostomium
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Most anterior part of worm body.
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Prostomium Characteristics
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Sometimes retractable, holds eyes, tentacles, sensory palps. Proboscis is what comes out pf prostomium when the jaws are showing.
It surrounds the mouth, has setae, palps, and chitinous jaws in predatory forms
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polychaete general body segments (3)
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Foregut, Midgut, & Hindgut
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Polychaete mobile species vs. sedentary species feeding habits
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mobile species - scavenger or predators
sedentary species - usually filter feeders
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use of parapodia within class polychaetes
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Used along side gills for they are used for gas exchange.
Some small species can use diffusion across the body.
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kidney characteristics among polychaetes
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3 types of kidneys depending on species
1. protonephridia
2. metanephridia
3. mixture of both
the nephrostome opens into the coelom.
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nerve characteristic
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**DOUBLE ventral nerve cord...rare quality, we only have one!**
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t/f polychaetes possess eyes, statocysts, nuchal organs...
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T.
They have everything from simple eye spots to eyes with good visual acuity and complicated structures (w. lens & cornea)
The Nuchal pits are chemoreceptive ---> [(chemoreceptor) a sensory receptor that responds to chemical stimuli]
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Facts about the sex organs of the Polychaetes
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>usually no permanent sex organs
>usually separate sexes
>gonads temporary swelling
>gametes shed into the coelom
>EXTERNAL fertilization
>larvae called TROCHOPHORE
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Trochophore
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Polychaete LARVAE
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representative polychaetes: NEREIS
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>clam or sand worms
>live in mucus-lined burrows in sediment
+hunt at night
+feed on small animals
+seize food with jaws & food is swallowed as worm withdraws pharynx
>creeps along on land, but can swim quickly by undulation
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representative polychaetes: SCALE WORMS
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>back looks as if it has scales
>very diverse and abundant
>flattened bodies
>carnivorous
>most are commensal, live in burrows of other polychaetes or with cnidarians, molluscs, or echinoderms
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representative polychaetes: FIRE WORMS
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>hollow, brittle setae that secrete venom
+setae puncture attacker and break off in the wound, depositing venom
**feed on cnidarians....no surprise!**
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representative polychaetes: TUBEWORMS
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***aka: "feather-duster worms"
>burrow in sand or mud
+line burrows with mucus to make a tube
>some are sedentary FILTER FEEDERS
>some are DEPOSIT FEEDERS by extending tentacles to find bigger food
>have radioles for filter feeding
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classes within phylum annelida
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(SHOP)
1. Siboglinidae
2. Hirudinea
3. Oligochaeta
4. Polychaete
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Characteristics of the class Siboglinidae (beard worms)
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>no mouth or digestive tract
+mutualistic relationship with chemoautotrophic bacteria, contained in an organ called a TROPHOSOME.
>CLOSED circulatory system
>separate sexes with gonads on trunk.
>cleavage poorly unknown
>worm shaped embryo ciliated, carried by water currents
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Clade Clitellata
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>Clade Clitellata contains Class Oligochaeta and Class Hirudinida
>Members of this clade share a unique reproductive structure called aCLITELLUM
>It is monophyletic
>do NOT have parapodia (like in the polychaetes)
>hermaphroditic (monoecious)
>Young develop inside a cocoon secreted by the clitellum, and emerge as small worms
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Clitellum
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>Unique repro. structure of those within the clade Clitellata
>Ring of secretory cells in epidermis (band on a worm)
>always visible on oligochaetes, but only during repro. season for leeches
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Class Oligochaeta - the worms
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>more than 3000 species
>terrestrial, marine, and a few parasitic
>usually have setae, not as many as polychaetes though
+aquatic = usually longer setae
>use PERITALTIC MOVEMENT
+contract & relax the CIRCULAR muscles while using an anchor point by contracting LONGITUDINAL muscles.
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Oligochaete (worm) Circulation & Respiration
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> double transport system
+ coelom fluid & circulatory fluid
> five main blood trunks through body
+ DORSAL VESSEL: above the alimentary canal from the pharynx to that anu
+ AORTIC ARCHES: maintain steady blood pressure in dorsa >>>>
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Oligochaete (worm) Excretion
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>Almost all segments have a metanephridia
+segment has the end of a kidney and the start of another kidney, which ends in the next segment
>ciliated funnel called a NEPHROSTOME leads to loops then an opening called the NEPHRIDOPHORE, which acts like a bladder. waste removed by another nephridophore.
>aquatic - secrete ammonia/terrestrial - urea &or ammonia
>salts and water can pass across the integument.
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Oligochaete (worm) Nervous & Sensory Systems
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>DOUBLE ventral nerve cord
>pair of cerebral ganglia act as a brain
>neurosecretory cells in the brain perform endocrine finctions
>possess "giant axons" in nerve cord
+very efficient signal transmission
>have some learning ability
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Oligochaete (worm) Reproduction & Development
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>Monoecious, usually simultaneously hermaphrodites
>multiple sets of gonads
>clitellum secretes mucus that holds mates together
>sperm travel via SEMINAL GROOVES
>CHITIN-LIKE COCOON forms around clitellum
+collects eggs, sperm, & albumin & that's where fert. occurs!
>cocoon falls off worm, seals and then young worms hatch out
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Class Hirudinea (leeches) Segments and body form
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>TRUE leeches = ORDER HIRUDINEA
+34 segments
+no setae
+ANTERIOR & POSTERIOR suckers
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How many orders are there under the class Hirudinea? What are they?
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3
>Order Hirudinea
>Order Acanthobdellida
>Order Branchiobdellida
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Phylum Annelida,
Class Hirudinea & its 3 orders!!!
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>Order Hirudinea
+34 segments/NO SETAE/anterior&posterior suckers
>Order Acanthobdellida
+27 segments/setae on FIRST FIVE segments/POSTERIOR sucker only
>Order Branchiobdellida
+14or15 segments/NO SETAE/ANTERIOR sucker only
+commensal or parasitic on crayfish
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Class Hirudinea (leeches) BROAD INFO
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>Most freshwater, plenty terrestrial in rainforest
>Hermaphroditic - clitellum ONLY during breeding season
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What makes the smaller rings with leech body segments?
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segments are marked by transverse grooves to make smaller rings
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Lacunae - among the leeches
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septa in coelom reduced or absent, SPACES CALLED LACUNAE
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movement of the leeches
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>crawl by loops or body forward
>swim by undulation
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eating habits of leeches
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many are BLOOD parasites, but many eat DECAYING ANIMAL MATTER
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respiration & excretion among leeches
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>gas exchange - via SKIN, a few species have GILLS
>10-17 pairs of nephridia plus coelomocytes
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sensory organs of the leech
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>TWO BRAINS, one anterior with SIX PAIRS of GANGLIA & one posterior with SEVEN PAIRS of ganglia
>21 PAIRS OF SEGMENTAL GANGLIA
>sense organs = SENSILLAE
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SENSILLAE in leeches
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their sense organs
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leech reproduction
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>Hermaphroditic cross fertilization
+sperm given via PENIS or HYOPDERMIC IMPREGNATION=spematophore
+Sperm given via liquid or sperm packet (cocoon like oligochaetes!) (to prevent drying out)
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Class Hirudinea (leeches) circulatory function
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some have a true circulatory system, but most use coelomic sinuses as a blood-vascular system
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Phylum Echiura - name derivation
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>echis (viper or serpent) & oura (tail)
~140 species
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Phylum Echiura - HABITAT
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>burrow in mud, sand, or live in holes & crevices
>found worldwide, shallow to very deep in the ocean
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Phylum Echiura - BODY characteristics
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>sausage-shaped body, flattened, extensible PROBOSCIS
>sometimes called "spoon worms"
>ciliated groove that leading to the mouth
+used for extending out & searching for food (mostly detritus)
>cuticle and epithelium
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Phylum Echiura - digestive characteristics
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>large coelom
>LONG, COILED, COMPLETE digestive tract
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Phylum Echiura - gas exchange
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>mostly in hindgut through cloacal irrigation
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Phylum Echiura - reproductive characteristics
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>separate sexes
>EXTERNAL fertilization
>TROCHOPHORE larval stage
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Phylum Sipuncula - name derivation
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>Latin - Sipunculus ("little siphon")
>sometimes called "peanut worms" bc they contract into a peanut shape
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Phylum Sipuncula - habitats
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~250 species
>shallow to very deep
>same habitats as echiurans - BURROWS --- some make their own by chemical & mechanical means
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Phylum Sipuncula - body characteristics
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>NO SEGMENTATION
>NO SETAE
>slender, retractile, introverted proboscis
+mouth @ tip of crown of cilliated tentacles
+some detritovores, some deposit feeder
>muscular trunk walls
>large, fluid filled coelom
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Phylum Sipuncula - digestive characteristics
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>U-shaped
>COMPLETE digestive tract
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Phylum Sipuncula - excretion
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one pair of large nephridia
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Phylum Sipuncula - circulation & respiration
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Circulatory & respiratory systems lacking
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Phylum Sipuncula - reproduction
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>sexes mostly separate
>sex cells released through nephridia
>SOMETIMES asexual repro by FISSION
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Coelom characteristics
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evolution of coelom poorly understood
>hydrostatic skeleton
>primitive circulatory fluid
>gamete storage for synchronous release
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Why have repeated segments (metamerism)?
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segmentation probably arose multiple times.
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