Eve Q4 Last Lectures

Molluscs

Super successful soft bodied

animals – most with a shell

More marine species in

phylum Mollusca (>100,000

species) than any other

phylum in the sea

Highly diverse morphology,

can be found in most

habitats in the sea

All molluscs have soft bodies, and most have a hard calcareous

(i.e. calcium carbonate) shell. Three Key Body Parts

Shell is secreted by a thin layer of tissue called the mantle

Muscular foot for locomotion

Radula for feeding is usually a ribbon of “teeth”

(Presence of veliger larva)

Major groups of molluscs

• Gastropods

• snails, sea slugs

• Bivalves

• clams, mussels, oysters

• Cephalopods

• octopuses and squids

• Chitons

Molluscs: Gastropods

Most snails have

spiraled shells, and their

bodies also coiled

Gastropods have a radula, a

ribbon of teeth that create

a rasping tongue

The shape of the radula

teeth is determined by diet

Teeth can be mineralized

with iron to scrape algae

from rocks

Molluscs: gastropod diets

Most gastropods are

herbivores and detritivores,

but several groups of snails

have evolved to be

predators and parasites

A few are

suspension

feeders

Nudibranchs

Molluscs

Cone Snails

Predators with a harpoon-like radula and venom

Feed on polychaetes, molluscs, some on fish.

~800 species

Molluscs

gastropods

Elysia chlorotica (a

sea slug) steals

chloroplast from

green seaweed and

incorporates them

into their bodies

Sea slugs can do some

amazing things, like steal

cnidarian stingers and

seaweed chloroplasts

Hermissenda

crassicornis (a

nudibranch) steals

nematocysts from

hydroids and stores

them in their body

projections

Molluscs: Bivalves

Bivalves have two shells that close

around the soft-bodied animal

They lack a radula

• Strong adductor muscle closes

the shell (e.g. scallop meat)

Most bivalves are

suspension feeders

They use long folded

gills to obtain

oxygens and also to

filter food particles

from the water

Often draw water

into long siphons

Most bivalves use their foot to bury themselves in sediment

Many live attached to hard substrates (e.g. oysters, mussels)

Some can swim (e.g. scallop, Lima clam)

Many bivalves live attached to hard substrates (e.g. oysters, mussels)

Some can swim (e.g. scallops, file clam

Molluscs

bivalves

Many bivalves live attached to hard substrates (e.g. oysters, mussels)

Some can swim (e.g. scallops, file clam

Molluscs: Cephalopods

Squids have 8 arms and 2

tentacles

All are strong swimmers and

live in the open ocean

They have a reduced shell called

a quill

They have an image forming

eye (independently evolved

from our eye) Squid

Squid, Octopus, Chambered Nautilus

Molluscs: cephalopods

Humbolt Squid

Bryozoans

“moss animals”

Small animals with a retractable crown of

tentacles using for feeding (lophophore) – all

are suspension feeders

Nearly all are colonial – individual zooids are

not independent

Important prey items for a variety of other

inverts and fishes

Many species on the California coast

Echinodermata (“echinoderms”)

All Echinoderms have:

• Adults have radial symmetry! – usually five-point

symmetry, but larvae are bilaterally symmetrical

• Characterized by a water vascular system (water-filled

canals)

• Tube feet extend from the water vascular system,

used for locomotion on sensing the environment

There are no freshwater echinoderms!

There are no terrestrial echinoderms!

Strictly sea creatures.

Echinoderm skeletons are formed

By ossicles that link together.

The are connected by Mutable

Collagen Tissue that can change its

mechanical properties quickly and

either allow the skeleton to deform

or stiffen.

Seastars use this to surround a prey,

stiffen the skeleton and pull open the

shell of the prey.

chordate

Phylogeny

Basic Chordate Body Plan

Chordata (Phylum)

Major Group

• Lancelets (Cephalochordata)

• Tunicates, Sea Squirts (Urochordata)

• Jawless Fishes

• Vertebrates

• includes fishes, amphibians, birds & reptiles,

turtles, and mammals

Lancelets: Cephalochordata

Has all of the features of

chordates:

Notochord, dorsal hollow

nerve cord, pharyngeal slits,

Post anal tail

~25 species

Sea Squirts & Tunicates: Urochordata

• Adults do not look like chordates, but larvae have all the chordate characteristics

• Adults can be solitary or colonial (multiple zooids), and are sessile (attached to

substrate)

• All are suspension feeders that actively pump water through a filter basket to capture

small food items (and breathe)

• About 3000 specie

Tunicates

The only chordates that are sessile as adults. Likely this is possible because they are

suspension feeders with efficient filter mechanism that works well in low water flow

Tunicates: solitary & colonial

Some are colonial - asexual reproduction

Jawless fishes: the hagfish

Hagfishes support important fisheries

sometimes for food, but also for skin (“eel skin”)

Lampreys: Jawless fish

• Lampreys can be parasitic

• They have many teeth on a round

mouth

• Their teeth are made of keratin

• They are eaten in many parts of the

world

The evolution of jaws

Jaws evolved from gill arches

In vertebrates, there are

seven gill arches

We call them either

“pharyngeal arches” or

“gill arches”

The evolution of jaws

Most cartilaginous and bony

fishes have 7 pharyngeal

arches:

1. Jaws

2. Hyoid arch

3-7. Gill arches (5)

Jaws

Hyoid arch Gill arches

Jaws evolved from gill arches

Most cartilaginous and bony

fishes have 7 pharyngeal

arches:

1. Jaws

2. Hyoid arch

3-7. Gill arches (5)

Extreme suction feeding: the slingjaw wrasse

Accomplished by

extreme protrusion of

the jaws (up to 60% of

the fish’s body length!)

Biting with the oral jaws: the parrotfish

Accomplished with

direct application of

the jaws to the

substrate

Cartilaginous Fishes:

Sharks, Rays, Chimaeras

Blacktip shark, Chimaera, Stingray

Cartilaginous fishes have claspers for reproduction

Claspers function during internal fertilization

May lay eggs or give birth to live offspring

Electroreception

Electroreception allows fishes to detect

muscle contractions close to the receptors.

It is a devastatingly effective tool in locating prey!

Metal Detectors

Transmit electromagnetic field which

cause metal to become energized and

retransmit their own electromagnetic field.

Sharks use Ampullae

in skin to detect

electricity

Sharks are surprisingly diverse!

Some sharks feed on

plankton

Plankton feeding evolved three times

in living sharks

Anatomy of Rays

• Dorso-ventrally flattened

• Pectoral fins fused to head

• Ventral mouth

• Dorsal spiracle for breathing

• Many have barbs on tail

Ray diversity

White Sharks

Reach 19 ft.

Live up to 70 years

Eats marine mammals

Endothermic (warm-blooded)

Independent Evolution of the Sawfish form

in Rays and Sharks

The saw functions in prey capture

Thresher Shark

Thresher sharks have a

very long dorsal lobe of

caudal fin.

What is the function of

this elongate tail?

Air Bladder

Function in most fish is buoyancy control, several fish also use as a lung.

Air bladder has a specialized region where capillaries exchange gasses

between the air bladder and blood.

Some fish have a direct connection

between esophagus and air bladder.

They use the bladder as a lung.

Tarpon, catfish (more common in

freshwater)

Lateral line – a unique fish organ for mechanosensation

detect minute changes in pressure – helps fish detect

prey, predators, or conspecifics (schooling), and orient to current

How does lateral line mechanosensation work?

1) Changes in pressure from pore to pore push

water of canal to different pores

2) Water pushes on jelly

3) Jelly moves hairs

4) Hairs trigger nerves

Species Richness in Chordate Groups is

unevenly distributed

Bony Fishes – 36,000 species (~18,000 are Marine)

Tetrapods – 30,000 species

Cartilaginous Fishes – 1,000 species

Jawless Fishes – 100 species

Urochordata – 3,000 species

Cephalochordata – 25 species

Two major types of swimming

Swimming by undulating the body

Swimming with paired or median fins

- Pectoral fins

- Dorsal fin

- Anal fi

Fish morphology

Fish shape is related to swimming and feeding

functions (“form follows function”)

See if you can guess what lifestyles the fishes on the

left have.

Fish swimming motions use different body parts and

different amounts of the total body

Trunkfishes swim with their fins

a hard, inflexible carapace protects them from

predators, but limits undulation of the body axis

Fish reproduction and life history

Fish reproductive modes:

Oviparous fish – most marine fishes are oviparous, with mothers releasing eggs into

the water (“free spawning”) or depositing them on or in something

Ovoviviparous fishes – mother retains egg inside body, which then hatch and live

young are released – mostly in cartilaginous fishes but also some bony fishes

Viviparous – embryos obtain nutrition from the walls of the mother’s reproductive

tract – for example, surf perches, some rays, and many sharks

Fish fertilization can be internal or external

All cartilaginous fishes have internal

fertilization (as we saw last week!)

• males have two “claspers” and insert

one into female

• much of their reproductive lives are still

a mystery

Internal fertilization is rare among bony

fish, but it does happen in some groups

• Most bony fishes have external

fertilization and are oviparous

Not all oviparity is the same

Spawning

Aggregations

Note clouds of

eggs and sperm

Fish reproduction can involve migrations between

freshwater and saltwater

Catadromy (spawn in sea

Northern Pacific Bluefin Tuna migrate huge distances

under high fishing pressure

Vertical Daily Migration in Bigeye Tuna

What is the “deep scattering layer”?

• layer of deep-living fishes

and other animals

• ”scatters” sonar

• air bladder reflects

sonar!

• many make vertical diel

migrations

• Tuna can swim down to

them and eat them

Tunas are Endothermic

Endothermy:

- Ability to raise body temperature above ambient

and defend body temperature.

• High energetic costs of constant, fast swimming

• Allows fish to move across temperature gradients

Tunas use a counter-current system – similar concept

to getting oxygen into blood stream with gills, but also

used to transfer heat between veins and arteries

Being endothermic helps tunas ignore water

temperature thresholds, and perform constantly at a

high rate

Tuna heat

their

blood by

moving

blood next

to their

warm

muscles

There are other endothermic marine fishes!

• Tunas (15 species)

• Lamnid Sharks

(Great white,

Mako, Salmon

shark)

• Opah (bony fish)

Major Evolutionary Novelties in Fishes

Endothermy – Evolved 3 times

2 jaws !! Found in all Ray-Finned fishes.

Antifreeze proteins in Antarctic fish. Evolved at least 3 times

Bioluminescence. Evolved more than 20 times

2 Jaw Systems

Oral Jaws & Pharyngeal Jaws

Oral jaws are the same as our jaws

Pharyngeal jaw develops from the last two gill arches

Oral jaws collect prey, pharyngeal jaws process prey

2 Jaw Systems

Oral Jaws & Pharyngeal Jaws

Oral jaws at the front of the head

Pharyngeal jaw at the back of the mouth cavity

Oral jaws collect prey, pharyngeal jaws process prey

Pharyngeal jaws develop from gill arches

Advantage of Endothermy

Maintain body temperature close to optima

Tunas are Endothermic

(warm-bodied)

Advantage of Tuna Endothermy:

• constant, fast swimming, requires high

energetic expenditure.

• Endothermy allows tuna to move across

temperature gradients and maintain high

physiological performance.

Antifreeze Proteins

Proteins that bind to ice crystals preventing ice forming in blood

Evolved in many metazoan groups, ~5 times in marine fishes

Allows fish to occupy very cold water

Bioluminescence

Biological Production of Light

- Produced by a chemical reaction

- May be produced by the fish or symbiotic bacteria

- Functions in camouflage, defense, predation,

and communication.

Bioluminescence can be intrinsic

or from symbiotic bacteria

Phylogenetic

Distribution of

Bioluminescence

In

Ray-Finned Fishes

For crab experiment of planktonic an benthic

In this case temperature

constraints on larval growth

limit the species range

Ghost Crabs are Different!

They appear to be limited by

temperature effects on

adults in winter

Even closely related species in the same region may

have range limits set by different factors

Atlantic Ghost Crab

(Ocypode quadrata)

Mud Fiddler Crab

Biological Pump

movement of

carbon and other elements to

the deep sea through sinking

of shallow water organisms

and detritus (marine snow)

Sinking material stays buried

for long periods if

thermohaline circulation slow

Natural vs Anthropogenic

climate change

Observed

temperature changes

far exceed

predictions from

natural causes only

Tropicalization

s planet Earth warms,

the distribution of many

species may shift

Basic hypothesis: move

toward the poles (away

from the equator)

On land, populations can

also move higher in

elevation (mountains).

What about the sea?

What if you live near the

poles

Tropicalization in California

Resurveying old plots from 1933 in 1992 (60 years later)

– Pacific Grove rocky intertidal

Southern species became more common and northern species became less common

Species invasions – global homogenization

warming waters may give

advantage to non-native species

that can handle the temperatures

of their new homes

Examples: fouling invertebrate

communities and estuarine algae in

CA (and worldwide)

Some species of tunicates and

bryozoans can now be found

worldwide

Melting ice raises sealevel

by 1.8 mm per year.

Expansion of water due to

increasing temperature

raises sea level by 0.6 mm/yr

Ocean Acidification:

Increase in CO2 causes ocean to become more acidic (lower pH)

CO2 dissolves in water in proportion to its concentration in air

low pH can compromise the ability of organisms with shells and skeletons

to biomineralize calcium carbonate, and can disrupt neurological function

(larval fish may be unable to smell)

extra CO2 can boost plant growth, but not always the case

• some marine seaweeds also have calcium carbonate skeletons

(coralline red algae)

• not all marine primary producers are CO2 limited

Climate Change: Effects on Ocean Processes

The ocean has moved faster in past 30 years (caused by increased surface winds,

that are caused by increased water temperature)

Dead Zones – Oxygen depleted water due to too much nutrients and abundance of

microbes eating decaying vegetation. These are happening more with higher temps.

Also, caused by polluted run-off (Mississippi River mouth is a major dead zone)

Methyl mercury – concentrates in big ocean fish and is toxic to humans. Since 1970 there is

a 55% increase in Bluefin tuna due to higher water temperature.

Biodiversity loss – Temperatures increasing faster in deep ocean

National Marine Sanctuaries

Gulf of the Farallones

• expanded in 2016

California Current Ecosystem

CA’s National Marine Sanctuaries are home to some of the most productive

waters on Earth – CA Current Upwelling System!

• largest concentration of breeding seabirds in continental US

• >240 fish species

• many commercially important species (e.g. salmon, Dungeness crab)

• one-third of the world’s whale and dolphin species

largest concentration of blue whales on Earth

145 ton animal

takes 1 ton of krill to fill their stomachs

nearly 0.5 million krill

Cordell Bank National Marine Sanctuary

deep rich seamounts – 400ft average depth

used to be heavily fished

trawling banned

closed to fishing since 2005

Cordell Bank National

Marine Sanctuary

As of 2020, these are the current restrictions

on commercial fishing activity in Cordell Banks

*No fishing gear can contact bottom in main bank

* Only demersal seines can contact bottom

Waste Disposal in the Sea

garbage, sewage, radioactive material

US signed an international treaty banning burial of radioactive materials until 2018

The U.S. dumps 242 million

pounds of plastic trash in

the ocean every year.

Exxon is the single biggest

contributor at 5.9 million

pounds

Great Pacific Garbage Patch

8 million tons

per year is

dumped in the

ocean

mall plastic particles – including microplastic beads that

were used in toothpaste & cosmetics (now banned in the US).

Eaten by a wide range of animals.

Poorly understood impact on marine health – active area of research

Climate Change:

What is Changing

1. Greenhouse gasses in the atmosphere are increasing (e.g. CO2)

2. Increased CO2 causes acidification of the ocean

3. Higher greenhouse gasses causes increased temperature

-this alters species ranges and stresses some directly

-warm water causes coral bleaching on reefs

-causes higher surface wind which moves water faster

-increases methyl mercury concentration in food chain

-loss of ice causes sea level rise

What makes a mammal a mammal?

• Mammary glands that produce milk

for nursing

• Possess fur or hair

• Warm-blooded

• Four limbs (tetrapod)

Marine Mammals 5 groups

Manatees\

Pinnipeds

sea otters

cetaceans

polarbear

General morphological patterns in marine

mammals

Drag reduction:

• Streamlining of body shape

• Loss or modification of rear limbs

• Loss or modification of fur

• Elaboration and modification of sensory capabilities

Blubber

a thick layer of

connective tissue and fat that

provides strong insulation.

It is highly vascularized and

organized with connections to

deeper muscle by tendons

2 inches thick in dolphin,

up to 2 ft thick in whales.

Often gives shape to cetacean body.

Found in cetaceans, pinnipeds, manatees, penguins

Rich in Vitamin D, omega-3 fatty acids – important nutrients

Cetaceans: whales and dolphins

Marine fishes -> land mammals -> marine mammals

An evolutionary reversal:

the first “whale” was a land

mammal

What living mammal are

cetaceans most closely

related to? hippo

Cetaceans: whales and dolphins

Two major groups:

1.Toothed whales (Odontocetes)

2.Baleen whales (Mysticetes)

Cetaceans

*Dolphins are toothed whales

Toothed whales

• About 73 species

• Diverse and can be

abundant in all the

world’s oceans

• Typically do not make

major migrations

• Extreme development of

acoustic capabilities