UNIT 7 INVERTEBRATES PART 2. ARTHROPODS ARTHROPOD CHARACTERISTICS Largest phylum of animals Most marine arthropods are crustaceans Body is segmented,

UNIT 7

INVERTEBRATES PART 2

ARTHROPODS

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

SMALL CRUSTACEANS COPEPODS: planktonic; use mouthparts to

filter and capture food Some parasitic

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

Whale liceRight whale with whale lice

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

Giant deep sea isopod

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

krill

School of krill

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

Giant lobster

Mantis shrimp

Hermit crab

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

LOPHOPORATES

BRYOZOANS, PHORONOIDS, LAMP SHELLS

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

ARROW WORMS

CHAETOGNATHS

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

Arrow worm

ECHINODERMS

5-WAY SYMMETRY“spiny-skinned”

movie

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)

Indian Sea Star Anthenea crassa

Sunflower Sea Star Choriaster granulatus , the dough-boy star

Astropectin polyacanthus

Arctic Sea Stars eatinga Clam

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

Brittle star larvae

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

Purple Sea Urchin with spines

Purple Sea urchin’s test w/ospines

Pencil Sea urchinBanded Sea urchin

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

Heart Urchin with and without spines

Internal Sand dollar

Keyhole sand dollar with and without spines

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

Orange sea cucumber Warty Sea cucumber

Sea cucumber eviscerating

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

Class Crinodea cont. Can have up to 200 arms

Passion flower feather star

Feather star

Sea lily

Sea lily reef

HERMICHORDATES

PHYLUM HERMICHORDATA

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

Acorn worm

Acorn worm feces

Acorn worm larvae

Phylum Chordata

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