Chapter 33: Invertebrates (Part III)
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Phylum Nemertea aka..?
Characteristics of Nemertea (ribbon worms):
- Cylindrical to flattened and very long
- Most are marine, few freshwater or live in humid terrestrial habitats
- Most range from 10 to 20 cm long
- Lineus Longissius reported to reach 60 meters!
_______ is reported to reach lengths of 60 meters!
- Lineus Longissimus
- A type of ribbon worm
The ____ body plan resembles that of a flatworm.
The nemertea (ribbion worm) has some ____ with ____ lateral nerve cords.
fluid-filled sac that serves as hydraulic power sources for proboscis
True or false: Nemertean (ribbon worms) are gonochoric
True. aka male and female worms
How do ribbon worms reproduce?
- Typically sexual reproduction.
- Some asexually via fragmentation but may fragments die and do not form a new animal.
Phylum Annelida aka:
Characteristics of Phylum Annelida:
- Segmented worms -ringlike segments
- Brain or cerebral ganglion and sensory organs at anterior
- Many species have eyes(earthworms don't)
- Head and tail develop first then segments form between them
- segments divided by septa
- each segment has pair of excretory organs, a ganglion, and locomotory structure (marine annelid segments also have reproductive organs)
- closed circulatory system
- ventral nerve cord connects ganglia in each segment with another and the brain
What is the advantage of segmentation, such as in Annelids?
Development and function of individual segments or groups of segments can differ
Which species of annelids DO NOT have eyes?
How do the segments in Annelids develop?
- Head and tail develop first
- Segments form between them
True or False: The segments found in Annelids are not divided by septa
False, they are!
Do annelids have an open or closed circulatory system?
How do annelids move?
By contracting circular and longitudinal muscles against the hydrostatic skeleton.
Define Chaetae (setae)
Bristles that help anchor annelids in substrates so they don't slip when they move
What are the two classes of Annelida?
- Class Polychaeta: Polychaetes
- Class Clitellata: Earthworms and Leeches
Annelid Class Polychaeta:
- Marine worms
- Parapodia-fleshy, paddle-like lateral projections used for swimming, burrowing or crawing
- Parapodia also have important role in gas exchange; in some species they are modified into gill-like structures
- Predatory polychaetes have powerful jaws
- Sedentary tube worms have feathery tentacles for filter feeding as well as gas exchange
- Most polychaetes are gonochoric and fertilization is external
- Palolo worms
- Fertilization>spiral clevage>ciliated mobile trochophore larve>growth to adult
Polychaetes are (freshwater/marine) worms
Fleshy, paddle-like lateral projections used for swimming, burrowing, or crawling
Other than for movement, what is the other important role of parapodia?
gas exchange, some species have modified them into gill-like structures
Fertilization is _____ in polychaetes.
Characteristics of Palolo worms:
- Annelids: Polychaetes
- gamete-filled terminal parts considered a delicacy by some South Pacific natives
Class Clitellata aka:
Earthworms and Leeches
Earthworms were formerly in class Oligochaeta and leeches were formerly in Class Hirudinea. Why were they merged together?
Because they both have a clitellim!
A thickened band on the body that secretes mucus to hold worms together during copulation and to form a cocoon for fertilized eggs to develop.
Do polychaetes have a clitellum?
No! Poly wants a clitellum.
- Head is not well developed
- no parapodia
- few chaetae & project directly from body wall
- Eat their way through soil
- No eyes, but do have light-, chemo-, and touch-sensitive cells
- Eggs develop into young worms similar to adults
- Most are freshwater, few are marine, some live in tropical terrestrial areas
- Dorsoventrally flattened
- Clitellum only develops during mating season!
- Suckers at both ends of body
- Coelom reduced and not segmented
- no chaete (except one species)
- eat detritus or devour small animals
- some suck blood--secrete anesthetics and hirudin
What do earthworms and leeches have in common?
- Both have a clitellim
What are some differences between Earthworms and leeches?
- Earthworms do not have eyes
- Leeches only develop a clitellum during mating season
- Leeches are mainly freshwater
Phylum Arthropoda aka:
- The Arthropods
- The most successful of all animals
- Two-thirds of all animals are arthropods
Great economic importance of Arthropods:
- Pollinate crops
- food for humans and other animals
- Damage to crops; insects are voracious herbivores
- Carriers or spreaders of disease to plants and animals including humans
Four extant plus one that is extinct (CCHMT):
- Class Chelicerata: spiders, mites, ticks, horshoe crabs
- Class Crustacea: crabs, shrimp, lobsters, barnacles, pill bugs
- Class Hexapoda: Insects
- Class Myriapoda: centipedes, millipedes
- Class Triloboita: trilobites (extinct)
What is the most successful of all animals?
Arthropod key features-Mouthparts:
- Chelicera (pincers) in chelicerates
- Mandibles (biting jaws) in hexapods, crustaceans, and myriapods
Segmentation in Arthropods:
- Body segments look alike in some arthropods
- tagmatization: the fusion of segments into specialized functional groups
- Tagmata include: head, thorax, abdomen
- In some arthropods, head and thorax are fused to form a cephalothorax
- fusion of segments into specialized functional groups.
- Includes: head, thorax, abdomen
- Some arthropods: cephalothorax
Exoskeleton in Arthropods:
- Made of chitin and protein
- provides antagonism for muscles, support for body, protection against physical forces
- Can protect against water loss
The exoskeleton in arthropods is made of ____ and ___.
Chitin and protein
Limitation to arthropod exoskeletons include:
- Size (weight gets too great with increased size)
- Rigidity (must undergo ecdysis or molting)
Jointed appendages in Arthropods:
- May be modified into antennae, various kinds of mouthparts, legs
- Can bend to extend or retract
- Joints serve as fulcrum for appendage movement so leverage is possible
Circulatory system of Arthropods
- Open circulatory system
- Heart pumps blood anteriorly
- Blood flows towards posterior through spaces between tissues, when heart relaxes blood returns to posterior region of heart through one-way valves.
Nervous system of arthropods:
- Double chain of segmented ganglia along ventral surface
- three fused ganglia form brain
- functions such as eating, moving, copulation, can be carried out even when brain is removed.
- compound eyes composed of ommatidia (individual visual units)
- ocelli= simple eyes present in some arthropods
Individual visual units that form compond eyes in arthropods.
Simple eyes present in some arthropods
Respiratory system in Arthropds:
- Gills: in marine crustaceans
- book gills: horseshoe crabs
- outer epithellium or gut for gas exchange: in some tiny arthropods
- Trachea: in terrestrial arthropods; tracheae branch into tracheoles
- Spiricles: openings in exoskeleton where air enters, can be closed to prevent water loss
- Book lungs: in many spiders
Book gills vs Book lungs:
- Book gills: horseshoe crabs
- Book Lungs: spiders
openings in exoskeleton where air enters; they can be closed to prevent water loss
Excretory system in arthropods
- In aquatic arthropods, waste diffises from blood in gills
- Malpighian tubules occur in terrestrial insects, myriapods, and chelicerates
- Occur in terrestrial insects, myriapods, chelicerates
- slender projections from digestive tract
- attached at junction of midgut and hindgut
- tubules contain fluid, are nitro-genous wastes from blood that bathes tubules
- precipitated as uric acid or guanine that are then emptied into hindgut for elimination
- water and salts are reabsorbed by hindgut and returned to arthropod's body
- Key adaptation to life on land
______ in arthropods are key adaptations to life on land.
Class chelicerata contains:
Spiders, mites, ticks, scorpions, daddy long-legs, horseshoe crabs
- Two tagmata (body sections)
- Pair of chelicera (fangs or pincers)
- Pair of pedipals
- foud pairs of walking legs
- mostly carnivorous, but mites are mostly herbivorous
Chelicerates have ____ tagmata. Which section bears all appendages and opisthosoma?
- Two tagmata
- The anterior prosoma bears all appendages and opisthosoma
- copulatory organs in male spiders
- large pincers in scorpions
- sensorial in most other chelicerates
Name the two orders found under Class Chelicerata:
- Order Araneae: Spiders
- Order Acari: Mites and Ticks
- From phylum Chelicerate
- Important as predators of insects
- produce silk that is forced out of spinnerets
- all spiders have poison glads with channels through their chelicerae
- poison/venom paralyzes prey
Wolf spiders and tarantulas prefer to ___ than spin webs.
Bites from ____ and ____ can be fatal to humans and large mammals.
black widows and brown recluse
- Mites and Ticks
- found in every habitat
- predators and parasites of various organisms
- most mites less than 1 mm long
- in mites, cephalothorax and abdomen fused into ovoid body
- Respiration using tracheae or directly through body surface
- ticks are blood-sucking parasites of humans and other animals
In ____ the cephalothorax and abdomen are fused together forming a ____ body.
Some ticks carry disease-causing agents such as:
- Rocky Mountain spotted fever
- Lyme disease
- Red-water fever (affects cattle, horses, sheep, and dogs)
- Three tagmata= cephalon, thorax, and adbomen
- Two pairs of antennae (crustaceans are the only arthropods)
- Three pairs of appendages for chewing and manipulating food
- vairous pairs of legs (located on abdomen and thorax)
- Crustacean appendages are biramous("two-brached")
- large crustacean have feathery gills for respiration
- Gas exchange in smaller crustaceans occurs directly through thin regions of cuticle or through entire body
Which class of arthropod has two pairs of antennae?
- Gonochoric (except barnacles)
- Characteristic naupilus larva with three pairs of appendages
- nauplius is evidence for single common ancestor
Decapod crustaceans include:
- "Decapod" means ten feet
- shrimp, lobsters, crabs, crayfish
- five pairs of thoracic appendages
- calcium carbonate reinforced exoskeleton
- cephalothorax covered by carapace
- pincers used for obtaining food
- swimmerates on ventral surface of abdomen in lobsters and crayfish
- Uropods are paired flattened appendages at posterior that form a paddle
- Telson- tail pipe
- uropods and telson push water anteriorly, propelling animal posteriorly
found on the ventral surface of abdomen in lobsters and crayfish
paired flattened appendages at posterior that form a paddle
Tail spine in decapods
____ and ___ work together to push water _____.
- Uropods and telson; anteriorly
- this propels the animal posteriorly
Sessile crustaceans aka...
Sessile crustaceans Barnacles:
- Sessile adults, but nauplius larva is mobile
- adults are filter-feeders; sweep legs through water in order to gather small food particles
- Hermaphroditic condition is thought to be related to their sessile lifestyle
- Have the longest penis relative to their size; allows sessile animals to cross-fertilize
_____ have the longest penis relative to their size.
Barnacles; allows sessile animals to cross fertilize.
Arthopod Class: Hexapoda aka?
- The Insects
- largest group of animals in terms of number of species and number of individuals
- found in every habitat on land and in freshwater; few found in the sea
External characteristics of insects:
- Digestive tract is tube about same length as body in many
- digestion occurs in stomach or midgut
- Malpighian tubules for excretion
- trachea for gas exchange
- spiracles are openings between segments along side of abdomen and thorax where air enters
In insects that feed on juices, digestive system is ____ and may be several times longer than body.
Sensory receptors of insects:
- Sensory setae sensative to mechanical and chemical stimuli; numerous on antennae and legs
- tympanum: thin membrane that acts like eardrum, detects sound waves and vibrations
- pheromones are chemicals released by insects for communicating mating signals, trail markers, etc.
Insect life histories:
- Metamorphosis: change in form
- simple metamorphosis: eggs>nymph stages>adult
- Complete metamorphosis: egg>larva>pupa(chrysalis)>final molt into adult or imago.
What is the difference between simple and complete metamorphosis?
Complete metamorphosis includes a pupa(chrysalis) stage.
Class myriapoda includes:
Centipedes and Millipedes
Class Myriapoda characteristics:
- Both have head followed by numerous segments
- both are gonochoric
- fertilization is internal
- all lay eggs
- One pair of legs per segment
- some centipedes hatch with a final number of legs; others add legs after hatching
- poison fangs
Centipedes that do not add legs tend to do what?
Tend to care for their young, a rather uncommon behavior among invertebrates
- two pairs of legs per segment
- roll into flat coil or sphere for defense
- glands produce foul-smelling fluid
- some produce cyanide gas
This type of myriapod can produce cyanide gas
Which is the poisonous type of myriapod?
Centipedes are (carnivorous/herbivorous) but Millipedes are (carnivorous/herbivorous).
- Centipedes: carnivorous
- Millipedes: herbivorous
Phylum Echinodermata: The Echinoderms
- "Spiney skin"
- Exclusively marine
- Deuterostome development (only other phylum beside vertebrates)
- Endoskeleton of calcium carbonate plates
- Pentaradial symmetry (parts of 5)
- water-vascular system aids in movement and feeding
- larva have bilateral symmetry
What is different about echinoderm larvae?
- Echioderms have pentaradial symmetry but larvae is bilateral
- thought to have evolved from bilaterally symmetrical ancestors.
The oral surface of asteroids (star like), ophiiroids (snake like), and echinoids (spike like) face (away/towards) subrtrate.
Towards the substrate
The oral surface of crinoids(sea lillies) faces (towards/away) from substrate.
Away from substrate
Holothuroids have a ______ axis and oral surface that faces _____.
- horizontal axis
- surface faces forward
- Ossicles = calcium carbonate plates that make up endoskeleton
- Depending on the class, ossicles may be more loosely arranged, tightly fit together to form a test, or scattered throughout the body.
- mutable callagenous tissue can change texture from tough and rubbery to fluid in seconds if animal is disturbed.
Echinoderms can automize body parts. This means they can?
Cast off body parts
Echinoderm Water-Vascular System (WVS)
- Radially organized
- WVS extends out into each arm of a sea star
- Ampulla allows tube foot to extend or contract
- gas exchange occurs across body surface and the tube feet.
Holothuroidans (sea cucumbers) also have respiratory tree that branch off the hindgut, this means?
water enters through the anus
Structure on aboral(away from the mouth) surface where water enters Echinoderms
The bulb that allows tube feet in echinoderms to extend or contract
Echinoderm regeneration and reproduction:
- Many echinoderms can regenerate body parts
- Sexual reproduction is the norm
- fertilization is external
- larvae are bilateral
- Each class of echinoderm has a characteristic larva
These echinoderms can automize their arms
Asteroids and ophiuroids
These echinoderms can eviscerate their digestive system entirely
Holothuroidians (sea cucumber)
True or false: Some echinoderms can reproduce asexually by splitting
What are the 5 extant classes of echinodems (ACHOE)?
- Sea Stars
- Orginized in parts of five or multiples of five
- Brittle stars
- Arms are slender and "snake-like"
- Arms join central disk very abruptly
- tube feet for feeding not locomotion
- brittle stars have no anus
- Sea urchins and sand dollars
- no arms
- five double rows of tube feet extend through calcareous test (shell)
- Spines are moveable and have a ball-and-socket joint
- Sea Cucumbers
- Oriented horizontally to substrate
- Parts of five
- Filter feeders
- Have repiratory tree
- If skin is rubbed, can go from rigit to liquid in a couple minutes
- Sea lilies and feather stars
- oral surface faces up
- filter feeders
What class of Echinoderm has no anus?
Ophiuroidea: Brittle Stars
Which class of echinoderm has movable spines with a ball-and-socket joint?
Class Echinoidea: sea urchins and sand dollars
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