1. UNIT 7
INVERTEBRATES
PART 2

2. ARTHROPODS

3. ARTHROPOD CHARACTERISTICS
Largest phylum of animals
Most marine arthropods are crustaceans
Body is segmented, bilaterally symmetrical
Jointed appendages
Exoskeleton made of chitin
Molt (shed exoskeleton)
small

4. CRUSTACEANS 68,000 known species Most marine Have gills
2 pairs of antennae
Examples; copepods, barnacles, amphipods, isopods, krill, shrimp, lobster, crabs

5. BIOLOGY OF CRUSTACEANS
Filter feeding
smaller crustaceans
Use bristles on appendages to gather particles
Use appendages in some for sucking and piercing
Stomach has chitinous teeth
Predators- decapods
Stomach is two chambered; digestive enzymes
Extracellular digestion; have anus

6. Open circulatory system Gill exchange gases
Simple brain; but well developed sensory organs
Compound eyes
Keen sense of smell
Communicate with signals

7. REPRODUCTION & LIFE HISTORY
Separate sexes
Internal fertilization
In decapods, females carry their eggs in their pleopods or swimmerets
Most have planktonic larvae

8. SMALL CRUSTACEANS
COPEPODS: planktonic; use mouthparts to filter and capture food
Some parasitic

11. Barnacles- filter feeder; live attached to surfaces; body enclosed with heavy calcareous plates; have feathery filtering appendages called cirri

13. AMPHIPODS- have a curved body that is flattened sideways
Under ¾ in
Head and tail typically curve downward
Ex: whale lice, beach hoppers
5000 species
Beach hopper

14. Whale lice
Right whale with whale lice

15. ISOPODS- similar in size to amphipods but have legs that are similar to each other and the body is dorsoventrally flat (flat back)
Pill bugs (land)
Fish lice
Fish lice

16. Giant deep sea isopod

17. KRILL OR EUPHAUSIIDS- shrimp-like crustaceans; up to 2
KRILL OR EUPHAUSIIDS- shrimp-like crustaceans; up to 2.5”; planktonic; head is fused with some of the body segments to form a carapace
Most filter feeders
Polar waters
Deep water
Main food source for large marine mammals

18. krill

19. School of krill

20. DECAPODS Shrimps, lobsters, and crabs 10000 species
Largest group of crustaceans
Five pairs of legs or perapods
1st which is the heavier- the claw or cheliped
3 pairs of maxillipeds- close to the mouth; used for eating
Well-developed carapace and encloses the cephlathorax (fused head and thorax)
abdomen

21. Shrimps and lobsters
Laterally compressed bodies with elongated abdomens
Shrimps are scavangers-some are cleaners
Some burrow in muddy bottoms
Lobsters are mostly nocturnal; scavangers and predators;
Hermit crabs (they are not true crabs) are scavangers; hide in snail shells

22. Giant lobster
Mantis shrimp

23. Hermit crab

24. OTHER MARINE ARTHROPODS
HORSESHOE CRABS
5 living species
Last of the class Merostomata; “living fossils”
Live on soft bottoms in shallow water
5 pairs of legs

25. SEA SPIDERS 4 or more pairs of jointed legs w/small body
Large proboscis w/mouth at the tip used to feed on small invertebrates
Cold water

26. Insects 3 prs of legs as an adult Rare in the sea Marine water strider
Most live on water’s edge or high tide mark
Marine water strider

27. BRYOZOANS, PHORONOIDS, LAMP SHELLS
LOPHOPORATES
BRYOZOANS, PHORONOIDS, LAMP SHELLS

28. LOPHOPHORATE CHARACTERISTICS
3 groups
Have a unique feeding structure called the lophophorate which is a set of ciliated tentacles arranged in a horseshoe shape
Suspension feeders
No segmentation
Bilateral symmetry
U-shaped gut

29. BRYOZOANS- form colonies on seaweeds, rocks and other species
4500 species; almost all marine
In phylum Ectoprocta
Colonies of individuals called ZOOIDS that secrete skeletons of various shapes
Lopophore is retractable
U-shaped gut ends in an anus outside the edge of the lophophore

33. PHORONOIDS-worm-like and build tubes
Horseshoe-shaped or circular lophopore
20 species
Burrow in sand or attach tubes to hard surfaces
Very small

35. LAMP SHELLS OR BRACHIOPODS
350 SPECIES
Shell w/2 valves that are dorsal and ventral to the body
Have a lophophore- w/2 ciliated and coiled arms
Attached to rocks or burrowed in soft sediment

37. ARROW WORMS
CHAETOGNATHS

38. Characteristics of Arrow worms
About 100 species
Transparent; streamlined; fish-like fins and tail
Head has eyes, grasping spines and teeth
Up to 4”
carnivores

39. Arrow worm

40. 5-WAY SYMMETRY “spiny-skinned” movie
ECHINODERMS
5-WAY SYMMETRY
“spiny-skinned”
movie

41. ECHINODERM CHARACTERISTICS
Radially symmetrical-adults
Pentamerous – based on 5-parts
Bilaterally symmetrical- planktonic larvae
No head
No anterior/posterior end; no ventral/dorsal side
Refer to the oral and aboral side
Complete digestive tract
Well-developed coelom

42. Water-vascular system- waterfilled canals
Endoskeleton
Water-vascular system- waterfilled canals
Tube feet- muscular extensions of canals
Extended when filled with water- have muscular sacs called ampullae
Used for movement, attachment, and receiving chemical and mechanical stimuli
Madeporite- or sieve plate- in sea stars and sea urchins; on the aboral side; where water enters the water vascular system

43. BIOLOGY OF ECHINODERMS
Radial symmetry = sedentary life style
Feeding and digestion- sea stars are carnivorous; they extend their stomach out through their mouth and excrete digestive enzymes; the food is then carried into the digestive gland and the stomach moves back into the body; if intestines are present, they are very small
Brittle stars- no anus; very simple guts
Crinoids- simple guts

44. Feeding and digestion cont.
Sea urchins and sea cucumbers have long coiled guts (sea urchins need this because they are herbivores and the sea cucumbers need this because they need to process sediment)
In all echinoderms, nutrients are passed in the coelomic fluid within the coelom
Also transports oxygen because they don’t have a circulatory system
Sea cucumbers have respiratory trees- which are thin, branched tubes that are connected to the gut and extend out to the anus

45. REPRODUCTION AND LIFE HISTORY-
NERVOUS SYSTEM AND BEHAVIOR- have a nerve net- more complex actions than cnidarians though
REPRODUCTION AND LIFE HISTORY-
Separate sexes
External fertilization
Zygote develops into a ciliated larva
Some don’t have larva but brood their offspring in specialized pouches
Some reproduce asexually by the separation of the central disc or body into two pieces- REGENERATION

47. TYPES OF ECHINODERMS 7000 KNOWN SPECIES- all marine Bottom dwellers
1. Class Asteroidea= sea stars
5 arms that radiate from central disk
Amulacral groove= the radiating channels on the arms
Can move in any direction
Endoskeleton = interconnected plates of calcium carbonate creating very flexible arms; aboral surface may be covered with spines that are modified into pincer like organs called pedicellariae which helps to keep the surface clean

48. Class Ophiuroidea= brittle stars; 5 arms are very long and brittle
Asteroidea cont.
Most are predators of bivalves, snails, barnacles or other attached or slow moving animals
Class Ophiuroidea= brittle stars; 5 arms are very long and brittle
Most eat detritus and small animals
Tube feet don’t have suckers, used for feeding
No anus
Most species (2000)

49. Indian Sea Star
Anthenea crassa

50. Sunflower Sea Star
Choriaster granulatus , the dough-boy star

51. Astropectin polyacanthus
Arctic Sea Stars eating
a Clam

52. Brittle star (Ophiocoma imbricatus)
Orange-banded Brittle Star (Ophiothrix)

53. Brittle star larvae

54. CLASS ECHINOIDEA OR SEA URCHINS
Endoskeleton forms a round, rigid, shell-like test with movable spines and pedicellariae
Body forms a sphere
Mouth on bottom; anus on top
Graze on seaweeds and seagrasses
Have Aristotle’s Lantern- the set of jaws and associated muscles used by sea urchins to bite food
1000 species

55. Purple Sea Urchin with spines
Purple Sea urchin’s test w/o
spines

56. Banded Sea urchin
Pencil Sea urchin

57. Class Echinoidea cont.
Heart urchins and sand dollars have flattened bodies and short spines
They are deposit feeders using tube feet and mucus to pick up particles

58. Heart Urchin with and without spines

59. Internal Sand dollar

60. Keyhole sand dollar with and without spines

61. CLASS HOLOTHUROIDEA OR SEA CUCUMBER
Worm like
No spines and no obvious radial symmetry
Look stretched
Lies on one side where the 5 rows of tube feet are; oral and aboral surface on the ends
Endoskeleton has microscopic spicules
Deposit feeders; tube feet around mouth are modified into branced tentacles

62. Class Holothuroidea cont.
Defensive mechanisms
Secrete toxic chemicals in filament
Might expel the gut or other internal organs; this is called evisceration
Prickly red sea cucumber

63. Orange sea cucumber
Warty Sea cucumber

64. Sea cucumber eviscerating

65. CLASS CRINOIDEA OR CRINOIDS
Suspension feeders
Feathery arms
600 species of feather stars and sea lilies
Sea lilies are in deep water and attached to bottom
Feather stars perch and crawl in both shallow and deep water
An upside down brittle star with the amulacral grooves and mouth facing upward

66. Class Crinodea cont. Can have up to 200 arms
Passion flower feather star

67. Sea lily
Feather star

68. Sea lily reef

69. HERMICHORDATES
PHYLUM
HERMICHORDATA

70. HERMICHORDATA CHARACTERISTICS
Share the same basic developmental characteristics of chordates and echinoderms
With chordates….
Dorsal, hollow nerve cord
Openings along the anterior part of the gut
With echinoderms…
Some have larvae
85 known species
Acorn worms or enteropneusts- live free or in u-shaped tubes

71. Acorn worm
Acorn worm feces

72. Acorn worm larvae

73. Phylum Chordata

74. 3 major groups or subphyla
Vertebrata
Urochordata
Cephalochordata
Protochordates- invertebrate
Chordata- lack the backbone

75. Chordata characteristics-
Single hollow nerve cord that runs along the dorsal length of the animal
Gill or pharyngeal slits
Notochord- a flexible rod for support that lies between the nerve cord and the gut
In vertebrata- surrounded or replaced by the backbone
Post-anal tail- a tail that extends beyond the anus
Ventral heart

76. TUNICATES Largest group of protochordates Subphylum Urochordata
3000 species; all marine
Sea squirts (Class Ascidiacea)
Saclike bodies; sessile; fouling organisms
Body protected by a tunic- a leathery gelatinous outer covering
Filter feeders; water flows through the mouth or incurrent siphon and out through the excurrent siphon
Ciliated, sieve-like sac- the pharynx
Can be colonial

77. Sea squirts cont.
Planktonic larvae have chordate characteristics; not the adult; known as tadpole larvae
Have gill slits, dorsal nerve cord, notochord and postanal tail
Has an eye as well
Sea squirt
Larva and adult

78. Tunicates cont Salps (Class Thaliacea) Planktonic entire life
Transparent, barrel-shaped body with muscle bands for locomotion
Water through the incurrent siphon on posterior end
Warm water
Some colonial

79. Tunicates cont. Class Larvacea or appendicularians Planktonic tunicate
Body of tadpole larva throughout life
Delicate house for protection and to filter for food

81. LANCELETS 23 known species Subphylum Cephalochordata
Body is laterally compressed and elongated like a fish; only up to 3 in long
Have all chordata characteristics throughout life except for backbone
Filter feeders; using gill slits to capture food
Live on soft bottoms