1. The Animal Kingdom Mollusks, Arthropods, and Echinoderms
Nancy G. Morris
Volunteer State Community College

2. Subgrade Coelomata Mollusks
Includes chitons, oysters, clams,
snails, slugs. octopus, squid
General Characteristics:
molluscus = soft body
coelom greatly reduced
main cavity is hemocoel - blood-filled cavity in open circulatory system
show no segmentation
bilateral symmetry obscure

3. Subgrade Coelomata Mollusks
Soft body composed of 3 main parts:
foot – large muscular, usually ventral, locomotion
2) visceral mass – contains digestive system, kidneys, heart, internal organs
3) mantle – heavy folds of tissue which cover the visceral mass; secrete shell; form siphons, develop gill & mouth

4. Subgrade Coelomata Mollusks
radula – rasping, tongue-like organ found in all except bivalves
trochophore larvum – free-swimming; links mollusks and annelids to a common flatworm ancestor

5. Anatomy of a Clam

6. Phylum Mollusca Classes
Class Amphineura - chiton
Class Bivvalvia - clams, oysters, mussels
Class Cephalopoda – squid, octopus, chambered nautilus
Class Gastropoda – snails, slugs, abalones, whelks, periwinkles, giant conch

7. Review: Animal Classification

8. Phylum Mollusca Classes
Class Amphineura -
“both nerves”
no eyes or tentacles
marine
elliptical, shell of 8 plates
chiton

9. Polyplacophora: chiton

10. Phylum Mollusca Classes
Class Bivalvia -
soft body between two halves of a hinged shell
highly developed muscular foot
bilateral symmetry obscured
most marine, some fresh water
no tentacles, head, radula
clams, oysters, scallops, mussels

11. Phylum Mollusca Classes
Class Bivalvia -
Pearl Production – protective function; foreign substance gets between mantle & shell, mantle secretes pearly layers of nacre around substance
clams, oysters, scallops, mussels

13. Phylum Mollusca Classes
Class Cephalopoda –
“head foot”
shell reduced & internalized in squid
no shell in octopus
largest invertebrates
possess eyes and tentacles
most active & intelligent
squid, octopus, chambered nautilus

14. Phylum Mollusca Classes
Class Cephalopoda –
most highly developed mollusk
squid & octopus possess ink sacs which produce melanin ; protective function
head-foot arrangement forms a siphon through which water can be forcibly expelled producing “jet propulsion”
squid, octopus, chambered nautilus

16. Phylum Mollusca Classes
Class Gastropoda –
“stomach foot”
univalve – single or one-piece shell
some have no shell
largest – giant conch – 1 foot length
Urosalprix – “oyster drill” bores hole in oyster + digests
snails, slugs, abalones, whelks, periwinkles, giant conch

18. Phylum Onychophora missing link between annelids and arthropods ???
Peripatus
Figure Campbell
suggests a stage in evolution of arthropods from a segmented, coelomate ancestor common to both the annelids & arthropods

19. Phylum Onychophora Annelid characteristics: Arthropod characteristics:
segmentally arranged nephridia
muscular body wall
ciliated reproductive tract
eye structure
Arthropod characteristics:
tubular heart
tracheae
hemocoel
large ganglion
mouth parts modified appendages

20. Subgrade Coelomata Phylum Arthropoda
General Characteristics:
most successful and adaptable of all animals
largest phylum in terms of numbers of species
means “jointed foot”
all have segmented bodies & exhibit metamerism
suggests a common ancestry w/annelids
segments fused into specialized regions

21. Subgrade Coelomata Arthropods
General Characteristics:
Exoskeleton of chitin – semi-rigid but flexible; permeable to water; waxy cuticle prevents dessication
coelom & hemocoel
exhibit metamorphosis (change in form)
exhibit molting (ecdysis)

22. Trilobite fossil

23. Phylum Arthropoda Classes
Class Archnida -
spiders, ticks, scorpions, mites
arthropod w/ 8 legs

24. Arachnids: scorpion & mites

25. Phylum Arthropoda Classes
Class Crustacea -
lobsters, crayfish, shrimp, crabs
Class Chilopoda -
“100 leggers” - centipeds; 1 pr legs per segment carnivorous; poisonous
Class Diplopoda -
“1000 leggers”- millipedes; 2 pr legs per segment; herbivorous

26. Crustraceans

27. Diplopoda: Millipede

28. Anatomy of a Crayfish

29. Phylum Arthropoda Classes
Class Insecta -
terrestrial & aquatic insects
Class Merostomata -
horseshoe crab, king crabs; “thigh mouth”

30. Insect metamorphosis

31. Limulus: A living fossil

32. Anatomy of a Grasshopper

33. Subgrade Coelomata Echinoderms (Campbell p. 625)
General Characteristics:
“spiny skin”
all members marine
exhibit secondary radiality (adults radials, but ancestors & larval forms bilateral)
bipinnaria larvum resembles hemichordate larvum
nearest in relation to chordates

34. Subgrade Coelomata Echinoderms
General Characteristics:
endoskeleton w/ external spines or ossicles
unique water vascular system for locomotion
body parts in 5’s or multiples of 5
dioecious
external fertilization

35. Subgrade Coelomata Echinoderms
General Characteristics:
no segmentation or well defined head region
autotomy (self-amputation) survival mechanism
regeneration
no parasitic members
deutrostomes (embrylogic development resembles chordates)

36. Phylum Echinodermata Classes
Class Asteroidea –
characterized by “star”
starfish, sea stars
Class Echinoidea –
characterized by “spines”
sea urchins, sand dollars
Class Holothuroidea –
characterized by “whole”
sea cucumbers

37. Echinoderms

38. Sea Cucumber

40. Echinoderm water vascular system
bivium
trivium
madreporite
stone canal
ring canal
radial canal
ampulla
ampulacral groove
tube feet
aboral
oral
This is where you draw and label the essential components of a starfish. The list on the left should guide you.