UNIT 7 INVERTEBRATES PART 2. ARTHROPODS ARTHROPOD CHARACTERISTICS Largest phylum of animals Most...
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Transcript of UNIT 7 INVERTEBRATES PART 2. ARTHROPODS ARTHROPOD CHARACTERISTICS Largest phylum of animals Most...
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
CRUSTACEANS 68,000 known species Most marine Have gills 2 pairs of antennae Examples; copepods, barnacles,
amphipods, isopods, krill, shrimp, lobster, crabs
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
Open circulatory system Gill exchange gases Simple brain; but well developed sensory
organs Compound eyes Keen sense of smell Communicate with signals
REPRODUCTION & LIFE HISTORY Separate sexes Internal fertilization In decapods, females carry their eggs in
their pleopods or swimmerets Most have planktonic larvae
Barnacles- filter feeder; live attached to surfaces; body enclosed with heavy calcareous plates; have feathery filtering appendages called cirri
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
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
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
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
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
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
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
Insects 3 prs of legs as an adult Rare in the sea
Most live on water’s edge or high tide mark Marine water strider
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
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
PHORONOIDS-worm-like and build tubes Horseshoe-shaped or circular lophopore 20 species Burrow in sand or attach tubes to hard surfaces Very small
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
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
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
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
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
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
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
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
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)
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
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
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
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
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
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
3 major groups or subphyla Vertebrata Urochordata Cephalochordata Protochordates- invertebrate
Chordata- lack the backbone
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
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
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 squirtLarva and adult
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
Tunicates cont. Class Larvacea or appendicularians
Planktonic tunicate Body of tadpole larva throughout life Delicate house for protection and to filter for
food
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