Transcript Chapter 9 - animals, higher invertebrates

Who, What, When, Where, Why, and How of
Higher Invertebrates
• Who studies invertebrates?
• What is the difference between a mollusc,
an arthropod, and an annelid?
• When do arthropods molt?
• Where do you find higher invertebrates?
• Why are cephalopods considered to be
“advanced” invertebrates?
• How do arthropods “grow”?
Chapter 9
Karleskint
Turner
Small
Phylum Mollusca
• One of the most successful groups of
animals in the ocean
• Have soft bodies, usually covered by a
calcium carbonate shell
• Wide range of sizes, lifestyles and
relationships to humans (i.e., some are food,
others cause commercial damage)
Molluscan Body
• 2 major parts:
– head-foot: region containing the head with its
mouth and sensory organs and the foot, which is
the animal’s organ of locomotion
– visceral mass: dorsal body region containing the
other organ systems, including:
• circulatory (heart and vessels)
• digestive (stomach, digestive glands, intestine and
anus)
• respiratory (gill)
• excretory reproductive systems
Molluscan Body
• Mantle
– protective tissue covering soft parts, extends
from the visceral mass and hangs down on each
side of the body, secretes the shell
• mantle cavity: space between the mantle and the
body
• Radula
– a ribbon of tissue containing teeth (found in all
except bivalves) used for scraping, piercing,
tearing or cutting pieces of food
Chitin Molluscs
• Class Polyplacophora - Chitons
• Have flattened bodies often covered by 8
shell plates
• Attach tightly to rocks, usually in intertidal
zone
• Most scrape algae and other organisms off
the rocks with radulae for food
Gastropod Molluscs
• Class Gastropoda
• May have no shell (nudibranchs), or a
univalve (one-piece) shell
– as the animal grows, whorls of the shell
increase in size around a central axis
• Feeding and nutrition for gastropods
– exhibit wide variety of feeding styles
– herbivores – using their radula, most feed on
fine algae; some on large algae like kelps
– carnivores – usually locate prey using its
chemical trail; have evolved various behaviors
for capturing/subduing prey
– scavengers and deposit feeders
– filter feeders
• Naked gastropods
– Nudibranchs (naked gill): marine gastropods
that lack a shell
– some feed on cnidarians and then use their
stinging cells as defensive weapons in the tips
of cerata
– bright colors indicate toxicity to predators
Bivalve Molluscs
• Class Bivalvia
• Have shells divided into 2 jointed halves
(valves)
• Includes:
– clams
– oysters
– mussels
– scallops
– shipworms
• Bivalve anatomy
– no head or radula
– laterally compressed bodies
– shell halves attached dorsally at a hinge by
ligaments
– mantle often forms inhalant and exhalant
openings to facilitate filter feeding
• palps form the food into a mass for digestion and
move it to the bivalve mouth
• Bivalve adaptations to different habitats
– soft-bottom burrowers (infauna)
• siphons: structures formed when the mantle is
fused around inhalant and exhalant openings,
which project above the surface of sediments
• siphons facilitate filter feeding while remaining
buried in sand
Cephalopod Molluscs
• Class Cephalopoda
• Named after the foot, which is modified
into a head-like structure
• Ring of tentacles projects from the anterior
edge of the head, for use in prey capture,
defense, reproduction and sometimes
locomotion
• Except for nautiloids, they lack shells or
have small internal shells
• Types of cephalopods
– Nautiloid cephalopods
• produce large, coiled shells composed of
chambers separated by septa (partitions)
– gas-filled chambers aid with buoyancy
– siphuncle: cord of tissue connecting the nautiloid to
uninhabited chambers (it inhabits the last chamber)
which removes seawater from each chamber as it forms
• head has 60-90 tentacles coated with a sticky
substance function in sensation or bringing food to
the mouth
– nautiloids (continued)
• move using jet propulsion
• usually dwell on the bottom during the day and
migrate to the surface at night
• eat hermit crabs and scavenge for other food on
the bottom
• food is temporarily stored in a crop prior to
transport to the stomach for digestion
– Coleoid cephalopods (e.g. cuttlefish, squids,
octopods)
• cuttlefish have a bulky body, fins, 10 appendages (8
arms + 2 tentacles), and small internal shells
• squids have:
– large cylindrical bodies with a pair of fins derived from
mantle tissue
– 10 appendages (8 arms + 2 tentacles) arranged in 5 pairs
around the head and embellished with cup-shaped suckers
which are attached by a short stalk and surrounded by
toothed structures
– the pen (a degenerate shell; an internal strip of hard
protein) helps support the mantle
– coleoids (continued)
• octopods have 8 arms (no tentacles) with suckers without
stalks or teeth, and sac-like bodies without fins
• coleoids cloud water with a dark fluid called sepia containing
melanin (a brown-black pigment) when disturbed
• swim by jet propulsion by forcing water through a ventrallylocated siphon or by fin undulation (in squids)
• octopods – better adapted to crawling over bottom
• have the most advanced, complex nervous system among
invertebrates
• Color and shape in cephalopods
– arm/body movements and color changes are
used in communication
– chromatophores: special skin cells containing
pigment granules which are concentrated or
dispersed to change color
– cephalopods can produce general body color
changes or stripes and other patterns
• Feeding and nutrition
– carnivores – prey is located with highly
developed eyes and captured by tentacles or
arms
– a pair of powerful, beak-like jaws in the oral
cavity is used to bite or tear tissues; octopods
use radula to drill holes in shells
– diet depends on and varies with habitat
• squids are pelagic: fish, crustaceans, squid
• cuttlefish find invertebrates on the bottom
• octopods forage or lie in wait near the entrances to
their dens
Fun octopus links
• https://www.youtube.com/watch?v=PmDTt
kZlMwM
• https://www.youtube.com/watch?v=IvvjcQI
JnLg
• https://www.youtube.com/watch?v=5MHJb
xWO6OM
Ecological Roles of Molluscs
• Food for humans and other animals
– snail shells are a calcium source for some marine birds
– sperm whales consume masses of squid
• Some snails are intermediate hosts to parasites
• A few bivalves have commensal relationships
(attaching to other animals)
• Now we will talk about Annelids
(segmented worms)
Annelids: The Segmented Worms
• Annelids—worms whose bodies are divided
internally and externally into segments
– segments increase mobility by enhancing leverage
– hydrostatic skeleton – compartment contained fluid
providing support to worm body
– setae—small bristles used for locomotion, digging,
anchorage and protection
• Types of marine annelids
– polychaetes
– echiurans
– Pogonophorans – tube worms
Polychaetes
• Polychaetes (class Polychaeta) are the most
common marine annelids
Polychaetes
• Feeding and digestion
– some errant species have mouth equipped with
jaws and teeth and are active predators; tube
dwellers may partially or completely leave the
tube to feed
– many sedentary species are filter or suspension
feeders
– digestive tract is usually a straight tube from the
mouth to the posterior anus
• food enters the mouth, nutrients are absorbed in the
intestine, and wastes are excreted through the anus
Polychaetes
– deposit feeders: animals that feed on bottom
organic material mixed with mineral deposits
• Now we will talk about Nematodes
Nematodes
• Class Nematoda (Roundworms)
• Round, slender, elongated bodies, tapering
at both ends
• Critical role as scavengers
• Some are parasitic
• Mast are hermaphroditic, some have
separate sexes
Ecological Role of Marine Worms
• Nutrient cycling
– through burrowing in sediment, release nutrients
buried in the ocean bottom back to the surface
for use by producers
• Predator-prey relationships
– Important links in food chains – consume
organic matter unavailable to larger consumers,
and then become food for largaer consumers
themselves
Ecological Role of Marine Worms
– nematodes are the most abundant members of
meiofauna
– echiurans may be significant in the diet of some
fishes
– polychaetes are a major food source for
invertebrates and vertebrates
• Symbiotic relationships
– tubes and burrows of non-carnivorous
polychaetes provide protected and ventilated
retreat for many commensals, e.g., scale
worms, bivalves, small crabs
• Now we will talk about the Arthropods
• Arthropods include insects and crustaceans
• Most numerous animals on Earth
• Very successful
Arthropods: Animals with Jointed
Appendages
• Phylum Arthropoda = 75% of identified species
(include insects)
• Have exoskeleton—a hard, protective exterior
skeleton composed of protein and chitin
• Molting—shedding and replacement of
exoskeleton to permit animal’s growth
• Body is divided into segments
• Usually, each segment has a pair of jointed
appendages, for locomotion, mouthparts,
sensation, ornamentation
Arthropods: Animals with Jointed
Appendages
• Have highly developed nervous systems
– sophisticated sense organs
– capacity for learning
• 2 major groups of marine arthropods:
– chelicerates – have a pair chelicerae (oral
appendages) and lack mouthparts for
chewing food
– crustaceans – have appendages called
mandibles that can be used to chew food
Arthropod Chelicerates
• Primitive group include spiders, ticks,
scorpions, horseshoe crabs and sea spiders
• 6 pairs of appendages; 1 pair are chelicerae
for feeding
• Horseshoe crabs
– 3 body regions
• cephalothorax – largest region with the most obvious
appendages
• abdomen – contains the gills
• telson – a long spike used for steering and defense
– body is covered by a carapace—a hard outer
covering
Arthropod Chelicerates
• Horseshoe crabs (continued)
– locomotion by walking or swimming by flexing
the abdomen
– mostly nocturnal scavengers
– smaller males attach to females to mate, and
eggs are laid in a depression on the beach;
larvae return to the sea to grow
Arthropod Chelicerates
• Sea spiders
– have small, thin bodies with 4 or more pairs of
walking legs
– only marine invertebrate known where the
male carries the eggs (with an extra pair of
appendages)
– palps—appendages used in sensation
– feed on juices from cnidarians and other softbodied invertebrates, using a long sucking
proboscis
Arthropod Crustaceans
• Crustaceans—marine mandibulates
• Crustacean anatomy
– 3 main body regions:
• head
• thorax
• abdomen
– appendages:
• 2 pairs of sensory antennae
• mandibles and maxillae used for feeding
• walking legs, swimmerets (swimming legs), legs
modified for reproduction, chelipeds (legs modified for
defense)
Arthropod Crustaceans
– gas exchange
• small crustaceans exchange gases through their
body surface
• larger crustaceans have gills
• Molting
– Crucial part of the life cycle
– Frequency of molting decreases with age
– Controlled by specific hormones produced in a
gland in the head, initiated by environmental
conditions, e.g., temperature, photoperiod
Decapod Crustaceans
• Order Decapoda
– Crustacean animals with 5 pairs of walking
legs:
– crabs
– lobsters
– true shrimp
• 1st pair of walking legs are chelipeds—
pincers used for capturing prey and for
defense
• Wide range in size
Decapod Crustaceans
• Specialized behaviors
– hermit crabs inhabit empty shells
– decorator crabs camouflage carapaces with
bits of sponge, anemones, etc.
– common blue crabs are agile swimmers
Decapod Crustaceans
• Nutrition and digestion
– chelipeds are used for prey capture
– appendages are used for scavenging
– predation and scavenging are usually
combined
– some decapods are deposit or filter feeders
Arthropod Crustaceans
• Order Stomatopoda – mantis shrimp
• Highly specialized predators of fishes,
crabs, shrimp and molluscs
• 2nd pair of thoracic appendages
– enlarged
– has a movable finger that can be extended
rapidly for prey capture/defense
– can either spear or smash prey
Arthropod Crustaceans
• Order Euphausiacea - Krill
• Pelagic, shrimp-like, 3-6 cm long
• Important part of plankton - filter feeders that
eat zooplankton
• Most are bioluminescent
– photophore: specialized light organ
– swarms: large masses of individuals;
bioluminescent is thought to signal swarming
behavior
• Food source for some whales, seals,
penguins, and many fishes
Arthropod Crustaceans
• Order Amphipoda - amphipods
• Shrimp-like, laterally compressed, with
posterior 3 pairs of appendages directed
backward
• Many are burrowers; some construct tubes
which they inhabit
• Most are detritus feeders or scavengers,
some are herbivores
Arthropod Crustaceans
• Class Copepoda – the largest group of
small crustaceans
• Usually the most abundant member of the
zooplankton
• Mostly suspension feeders; some rely on
detritus, some are predators
Arthropod crustaceans
• Class Cirripedia (barnacles)– the only
sessile crustaceans
• Most have calcium carbonate shell
• Attach directly to a hard surface, or have a
stalk for attachment
• Filter feed using cirripeds—feathery
appendages which extend into the water
when the shell is open
Antennae
Shell plate
Eye
Appendages
2 Nauplius larva
1 Adult barnacle
Carapace
Stalk
Cirripeds
Antennae
Shell plate
Carapace
Appendages
5 Shell plate
Cirripeds
develops
3 Cyprid larva
Cirripeds
4 Attached cyprid
Stepped Art
Fig. 9-40, p. 247
Ecological Roles of Arthropods
• Arthropods as food
– important food sources for marine animals
and humans
– copepods form link in marine food chain
between phytoplankton they eat and many
animals that use copepods as a major food
source
– krill are consumed in large quantities by
whales and other organisms
Ecological Roles of Arthropods
• Arthropods as symbionts
– cleaning shrimps remove ectoparasites and
other materials from reef fish
– some copepods are ectoparasites for fish
– some copepods are endoparasites or
commensals within polychaete worms,
echinoderms, tunicates, bivalves or cnidarians
– an antarctic species of amphipod carry sea
butterflies
– barnacles are commensal with a wide
diversity of hosts
Ecological Roles of Arthropods
• Role of arthropods in recycling and fouling
– grass shrimp feed on detrital cellulose
material, helps to break down algae and
grasses in tidal marsh ecosystems
– barnacles are a serious fouling problem on
ship bottoms
• attached barnacles can reduce ship speed by 30%
• Economic significance – boat hulls require special
paints and other anti-fouling measures
• Now we will talk about Echinoderms
Echinoderms: Animals with Spiny Skins
• Phylum Echinodermata
• Include sea stars, sea urchins and sea
cucumbers
• Larval forms exhibit bilateral symmetry but
most adults exhibit a modified form of radial
symmetry
• Mostly benthic, and found at nearly all
depths
• Sea cucumbers and brittle stars are
commonly found in deep-sea samples
Echinoderm Structure
• Endoskeleton: internal skeleton that lies
just beneath the epidermis
– ossicles: plates of calcium carbonate
Echinoderm Structure
• Water vascular system: unique hydraulic
system that functions in locomotion,
feeding, gas exchange and excretion
– water enters by the madreporite
– passes through a system of canals
– attached to some canals are tube feet—
hollow structures with a sac-like ampulla
within the body and a a sucker protruding
from the ambulacral groove
Echinoderm Sea Stars
• Class Asteroidea – sea stars
• Typically composed of a central disk + 5
arms or rays
• On underside, ambulacral grooves with
tube feet radiate from the mouth along
each ray
• Aboral surface: the side opposite the
mouth, which is frequently rough or spiny
Sea Stars
• Feeding in sea stars
– most are carnivores or scavengers of
invertebrates and sometimes fish
– prey are located by sensing of substances
they release into the water
– sea stars envelope and open bivalves, evert a
portion of the stomach, and insert it into the
bivalves to digest them
Echinoderm Ophiuroids
• Class Ophiuroidea
– e.g. brittle, basket and serpent stars
• Benthic with 5 slender, distinct arms,
frequently covered with many spines
• Lack pedicellariae and have closed
abulacral grooves
• Tube feet lack suckers and are used in
locomotion and feeding
• Brittle stars shed arms if disturbed
Echinoderm Sea Urchins
• Class Echinoidea (“like a hedgehog”) –
echinoids
• Body enclosed by test—a hard exoskeleton
• Benthic on solid surfaces (sea urchins) or in
sand (heart urchins, sand dollars)
• Regular (radial) echinoids: sea urchins;
spheroid body with long, moveable spines
• Irregular (bilateral) echinoids: heart urchins
and sand dollars; have short spines on their
tests
Echinoderm Sea Cucumbers
• Class Holothuroidea
• Have elongated bodies, and usually lie on
1 side
• Respiratory trees: a system of tubules
located in the body cavity which
accomplish gas exchange
• Sexes are generally separate
• Eggs may be brooded or incubated; larvae
are planktonic
Echinoderm Crinoids
• Class Crinoidea–sea lilies and feather stars
• Primitive, flower-like echinoderms
• Most are feather stars, which seldom move
and cling to the bottom with grasping cirri
• Suspension feeders
• Can regenerate lost arms
Ecological Roles of Echinoderms
• Spiny skins deter most predators
• Predators of molluscs, other echinoderms,
cnidarians, crustaceans
– crown-of-thorns sea star eats coral
– sea urchins destroy kelp forests
• Black sea urchins (Diadema antillarum)
control algal growth on coral reefs
• Sea cucumber poison, holothurin, has
potential as a medicine
• Now we will talk about hemichordates
Hemichordates
• Acorn worms (phylum Hemichordata)
• Sessile bottom dwellers that burrow in
sediments of intertidal mud or sand flats or
under stones
• Collects food with a large proboscis
• Some species use their proboscis to dig
burrows; the head protrudes from one end
of the burrow, while the anus deposits
fecal material near the other
Invertebrate Chordates
• Phylum Chordata
• Have 4 key anatomical characteristics at
some point in their life cycle:
1) notochord
2) pharyngeal gill slits
3) postanal tail
4) dorsal, hollow nerve tube
Invertebrate chordates -Tunicates
• Subphylum Urochordata
• Mostly sessile, widely distributed
• Named for their body covering
– tunic: body covering, largely composed of a
substance similar to cellulose
• Types:
– sea squirts
– salps
– larvaceans
Sea Squirts
• Lifestyles: solitary, colonial, compound
– compound: organisms composed of several
individuals (zooids) that share a common
tunic
• Filter feed on plankton in the water
passing through their pharynx
– some have symbiotic algae or bacteria
• Can regenerate lost body parts
Invertebrate Chordates - Cephalochordates
• Subphylum Cephalochordata- lancelets
• Fish-like chordates; slender, laterally
compressed and eel-like in form and
behavior
• Benthic; burrow in coarse sands
• Suspension feed by projecting their heads
above the sand
• Separate sexes practice internal
fertilization