sign in sign up
<<
Home , Beak (bivalve), Calcareous, Caudofoveata, Chromatophore, Coleoidea, Cuttlebone

Eucoelomates a few eucoelomates (mainly and ) are having a true are referred to as being eucoelomates à the is the first to develop in an eucoelomate animals have a that is there are 2 main ways that a true coelom can develop completely lined with in an embryo: the mesoderm can develop into muscle layers & in most the coelom appears as internal skeletal elements a split in the mesoderm layer of the embryo (schizocoelous)

à a large fluid filled coelom surrounded by muscle most coelomates are protostomes layers makes a more effective hydrostatic in many in most deuterostomes, the coelom appears as outpocketings of the archenteron à mesodermal layers lead to development of (enterocoelous) and veins, ie circulatory systems; better supply to all internal organs echinoderms and chordates and a few minor phyla are deuterostomes

à since mesoderm lines the digestive tract, this allows for the development of much more elaborate digestive organs

eg. compare the digestive tract of to Ascaris.

à mesenteries to support internal organs most eucoelomates are protostomes

à the develops first in an embryo

Animals: ; Ziser Lecture Notes, 2015.10 1 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 2

Animals – Molluscs but most (80%) less than 10 cm (~4”)

110,000 living; 70,000 molluscs are mostly aquatic; found from the tropics to second largest phylum of animals in terms of number the polar of known occur from the bottom of the oceans to 7000 M above some estimate there are up to 150,000 species level most versatile of all animals typical fauna of all parts of the ocean, ponds,

lakes, streams and rivers, , intertidal range from fairly simple to some of the and terrestrial most complex and specialized of

bottom feeders, planktonic, burrowers, borers, includes: , , , , , pelagic forms , , , , ,

shells one group, , are considered the most

intelligent of all invertebrates the phylum is divided into 8 different classes but 90%

of species are in only two: bivalves & snails the phylum originated in the sea and most of them

remain there good record; since most secrete a shell

à only bivalves and snails moved to brackish all living classes were well established early in the and freshwaters fossil record

but did not become dominant until the à only snails invaded land mostly died out in the (~250 MY ago) mollusks are closely related to segmented worms

microscopic to 20 M (50-60’ = ) and up to à same larval form = 900 kg (1980 lbs; ~ 1 ton)

eg. 1.5 M and 250 kg (500 lbs) Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 3 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 4 Body Plan glands in epidermis secretes mucous, cement and sometimes a shell well developed bilateral symmetry in some mollusks the hangs down to create most are unsegmented mantle cavity around the internal organs

a few primitive forms seem to show some segmentation. houses respiratory organs; most molluscs (except bivalves) have a well developed sometimes the mantle itself serves as a respiratory bears mouth and various organs products from the digestive, excretory & in spite of wide diversity of group most share reproductive systems empty into mantle cavity some basic features in their body plan: before release

mantle - secretes shell or becomes outer body covering a continuous current of water is created by itself cilia to bring in food and and to visceral mass – most internal organs are embedded in tissue rather than being surrounded by the body cavity remove wastes and gametes shell - (internal or external) – specialized feeding organ in mouth some molluscs are able to retract head or foot into foot - usually used for locomotion mantle cavity for protection

1. Mantle 2. Visceral Mass the body wall of mollusks consists of an outer layer of epidermis that extends over most of mantle is underlain by complex layers of muscle the as a mantle and connective tissues

often contains various sense organs most of the body organs are embedded in a solid mass called the visceral mass rather than eg. ocelli, sensory papillae being located in a true cavity

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 5 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 6

the body cavity of molluscs is a true coelom but it thickens is greatly reduced to a small space around produces irridescent “mother of ” the shell appears in embryo it has become part of an open

3. Shell grows throughout à often growth lines

in most molluscs the mantle secretes a shell usually used for protection which serves as a protective but some bivalves use shell to rasp into wood great variation in shell form and structure or rock

shell made of in some such as squid and octopus the shell is internal and greatly reduced calcium extracted from water, or food the mantle serves as the animals outer shell is composed of 3 layers: covering

= outer 4. Radula

especially thick in freshwater molluscs à protects from acidity common in fw in mouth is -like rasping organ = radula

in many marine forms this layer is thin or absent found in all groups except bivalves and () prismatic layer = middle hardened file-like, up to 250,000 tiny teeth dense prisms of in matrix the numbers and of teeth are used to identify certain species nacreous layer = inner new rows of teeth are continually added to the glossy film of calcium carbonate sheets back of the radula ad the front teeth are

secreted continuously through live worn down

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 7 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 8 the foot of many bivalves contain a gland that produces the radula is supported by a -like rod byssal threads (sea ) for attachment

(=) silky filaments of keratin and other

used to scrape, pierce, tear or cut food attached to substrate by extremely effective cement

in some molluscs a portion of the foot is modified radula also acts as a conveyor belt to move food into a long tubular for feeding toward the digestive tract

5. Foot Feeding and

all molluscs have a thick muscular foot feeders, burrowers, borers, grazers, , filter feeders, etc variously modified for locomotion: in mouth is tonguelike rasping organ = radula creeping movements - produced by waves of muscular contractions that move through foot most internal organs, including the digestive system

or by creating a slime trail from mucous glands in the are embedded in solid tissue called the visceral foot mass, instead of being free inside a body cavity (coelom) eg. snails à gliding movement

or digging into complete digestive tract divided into discrete, being extended from body into sediment functionally specialized regions: hydraulically by engorging with blood to anchor then draw rest of body into sediment foregut eg. bivalves eg. scaphopoda buccal cavity mouth, radula, salivary glands, or for attachment: receives and prepares food

may secrete to adhere to solid substrate midgut

eg. limpets, chitons, land snails and associated digestive glands sorting region, crushing region Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 9 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 10

crystalline style in some to grind food some digestion takes place in digestive gland simple heart with a few vessels

hindgut heart with 2 auricles and 1

intestine usually long and coiled absorption of nutrients extending from heart is formation of (undigested residue)

reduced coelom becomes a haemocoel surrounding heart

most mollusks have folded, ciliated gills (=ctenidia) blood contains several kinds of cells:

àthin feathery sheets of tissue covered with cilia oxygen carrying cells with to improve

efficiency of oxygen transport: also used for feeding in bivalves

haemocyanin (Cu) - most - some mollusks breath through their some with (Fe) - many terresrial snails lack gills (=pulmonates) some blood cells

no clotting agents or thrombocytes àmantle is modified into a saclike “” for breathing air cephalopods have a closed circulatory system

Circulation Endocrine Systems open circulatory system in most well developed endocrine system

à blood not entirely contained within vessels à controls laying and growth

works good for slow moving animals

à the most active molluscs, the cephalopods, have a closed circulatory system

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 11 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 12 CNS is a ring of ganglia in head area with paired some molluscs have several pairs of nephridia nerves and ganglia extending to other parts of the body some also occurs through body wall and gills

eg. pedal ganglia à control foot Reproduction & Development although the molluscs have a relatively simple nervous system most molluscs are dioecious; some, especially gastropods, are monoecious () cephalopods are considered the most “intelligent” of all invertebrates many marine forms produce characteristic = trochophore

rival some in ability to reason & learn same larval form is found in some , and a few other minor phyla unlike most molluscs, cephalopods are active predators in some gastropods and bivalves a second larval form develops = à can recognize prey with sharp it is also free swimming and has a foot, shell à can learn by watching and mantle

in many molluscs the trochophore larvae develops in the Excretion unhatched egg and a veliger hatches to become the only free swimming larva in these species usually 1 pair of nephridia (=metanephridia) some freshwater bivalves produce a parasitic larva often called kidneys (not really true kidneys) =

(metanephridium consist of a tube that opens into body cavity it attaches to gills of and at one end and drains to the outside) feeds on blood

in many species the nephridial tubule also acts as in cephalopods, many freshwater snails and some gonoduct bivalves

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 13 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 14

development is direct, ie. no larval stage Classification of Phylum Mollusca

Evolution of Molluscs : Aplacophora: now & Solanogastres new molecular evidence indicates an evolutionary Class: Monoplacophora relationship between Molluscs, Flatworms, and Annelids Class: Polyplacophora ()

Molluscs branched off the main animal line about 545 Class: Scaphopoda (tusk shells, tooth shells) MY ago Class: (mussels & clams) and animal life on land would not arise for another 100 MY Class: (snails & slugs)

Class: Cephalopoda (octopus and squid)

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 15 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 16 Class: Aplacophora Class: Monoplacophora

(sometimes divided into 2 classes; Caudofoveata & Solenogastres) means: “one plate” means “no plate or shell’ 25 species ~370 sp small; 3mm to 3 cm features may be closer to ancestral mollusc than any other modern group fossils known from all marine; most are small; 2-140mm long àwas believed to be an extinct group until discovered near Costa Rica in 1952 soft bodied, wormlike, no shell, no distinct head small, single, low rounded shell with ventral creeping foot body covered with scales or spicules superficially resemble limpets (gastropods) some are burrowers in muddy unlike other molluscs; show some evidence of

segmentation àfeed on & microorganisms and detritus

some organs are serially repeated in body: others don’t burrow and live on the sediment and feed 3-6 pairs of gills on larger organisms including 8 pairs of muscles 3-7 pairs of kidneys (nephridia) radula is present in some, absent in others [it was once believed that the mollusc ancestor was a segmented wormlike animal but current research has discredited that some have gills for respiration hypothesis]

have radula for scraping food no nephridia

ladderlike nervous system similar to flatworms monoecious or dioecious

eg. sp.

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 17 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 18

Class: Polyplacophora broad ventral foot attaches firmly to substrate (chitons) the grooves along sides of foot form closed means “many plates” “tubes” open at each end

1000 species Feeding body is flattened with convex upper surface most feed on using radula to scrape algae from surface most 2-5 cm; some to 30 cm one predatory species ( velata) prefers rocky intertidal zones; captures small invertebrates by “jumping” on them but found to 4000 M deep Respiration all marine gills suspended in mantle cavity along sides of thick clings to rocks or hard surfaces flat muscular foot fairly sedentary; may move short distances to feed water is pumped across gills within the “tube” head and cephalic sensory organs reduced at low tide when exposed, can breath air to some degree shell contains 8 overlapping plates on dorsal surface Nervous System if detached, can roll up like pill bugs/armadillo 2 long nerve cords extend along body mantle forms a girdle around margins of plates osphradia in mantle cavity near anus sometimes covers part or all of plates à samples chemical in water

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 19 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 20 Reproduction Class: Scaphopoda (tusk shells, tooth shells) sexes separate (dioecious) in most means “trough foot” often with complex courting behaviors ~900 species produce trochophore larva slender bodies in tubular shell, open at both ends

most 2.5-5 cm; some up to 25 cm

marine molluscs

subtidal to 6000 M deep

esp Atlantic

sedentary (not sessile),

à burrows into or sand

mantle wrapped around viscera and fused to form a tube

foot protrudes through larger end of shell

àused to burrow into sediment

as it burrows it always leaves the small end exposed to water

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 21 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 22

Feeding & Digestion dioecious feeds mainly on detritus and protozoa caught by cilia produces trochophore larva on foot or using -like captacula

àmucous covered extending from head

captacula may also serve a sensory function radula carries food to for crushing

Respiration no gills mantle wraps around viscera and fuses to form tube movement of foot and cilia pump water through tubular mantle cavity

àgas exchange occurs across surface of mantle

Nervous system no eyes captacula may serve some sensory function

Reproduction

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 23 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 24 Class: Bivalvia shell is mainly used for protection but does have some other uses in some species: means: “two valves” eg. use shell to burrow into wood and then feed on wood particles old name for class was pelecypoda = “hatchet foot” eg. some clams are able to bore into rock and concrete with includes mussels, clams, , oysters, shipworms spiny valves

1 mm to 1.5 M (Tridacna) eg. scallops use shell for propulsion by quickly closing them together to force out water up to 500 lbs à can swim in any direction all are aquatic mostly marine, Mantle many brackish, some freshwater shell is secreted by mantle most are filter feeders their mantle can also produce “”

pearl production is a protective action toward some foreign no head, no radula, almost no body between shell and mantle

Shell eg. sand grain, parasite, etc

mantle secretes layers around object shell is laterally compressed; 2 valves (right & left) commercial pearls are produced by some oysters & some freshwater bivalves “bulging” part of shell on dorsal side near hinge = posterior portions of mantle come together to form incurrent and excurrent siphons is the oldest part of shell; grows from edges in some bivalves the siphons can be quite long shell held together dorsally by hinge and adductor muscles extending between shells Foot

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 25 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 26

thick muscular foot used for locomotion some bivalves are predators: changes in blood pressure as hydrostatic skeleton eg. septibranchs slurp up tiny by creating a strong allow foot to dig in and anchor itself in sediment suction in mantle cavity to draw in prey

then muscles constrict and pulls rest of animal in eg. razor clams thrust proboscis between shells of other bivalves to kill and eat them some mussels are sessile and attach to substrate by some bivalves get most of their food from symbiotic byssal threads secreted by glands in the foot algae () that live in mantle tissue

Feeding & Digestion eg. Tridachna

food enters mouth and enters stomach most bivalves are filter feeders: in stomach, food is sorted gills are used to filter food out of water a gelatinous rod (= crystalline style) spins food is strained out as water passes over gills slowly (by cilia) & dissolves to release digestive enzymes trapped in mucous and moved by cilia to mouth particles are sorted by size: some bivalves are deposit feeders: àlarger particles move to intestine àsmaller particles move to digestive gland use long proboscis like organ formed from modified foot to collect food in sand or mud Respiration some bivalves use their shell to bore into solid objects gills used for respiration to extract food: cilia on gills create incurrent and excurrent flow eg. shipworms “termites of the sea” have long, wormlike appearance; long siphons use small valves as rasping organs to drill through wood oxygen is extracted from water passing over gills and eat wood particles excavated in gut digest the wood and fix nitrogen for host Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 27 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 28 Circulatory System in most à fertilization is external

3 chambered heart (2 atria, 1 ventricle) in develop into characteristic trochophore larva pericardial cavity in some marine forms a second free swimming larval wraps around intestine form is produced = veliger beats slowly (has shell, foot and mantle) pumps blood to gills for oxygenation and to kidney for eg. :

excretion 50 Million eggs released per season

Nervous System embryo develops into trochophore à veliger à spat sense organs poorly developed freshwater bivalves have in foot gills become brood chambers tactile cells in mantle cavity bivalved glochidia larvae (specialized veliger) are released eyes in scallops along mantle edge some moms can “shoot” larvae into water column

à each has cornea, lens, , layer others produce a structure that looks like a small fish to entice predatory when fish bites the “bait” it gets a mouthful of glochidia which then attach to the usually dioecious; they parasitize gills of fish for 1 - 3 weeks generally causing little some (eg some oyster species) are prodandrous harm to their host but dispersing far and wide

then release and sink to bottom to become filter feeders gametes discharged into mantle cavity and out excurrent

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 29 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 30

Class: Gastropoda Body Plan means “belly foot” unlike clams, snails and slugs have a distinct head with , sense organs and mouth 70,000 living species; 15,000 fossils sense organs: simple eyes à 1/3rd of all molluscs tentacles chemical receptors largest and most successful class of molluscs mouth with radula extremely diverse group: snails, slugs, , à rasps and scrapes algae limpets, , conchs, periwinkles, sea slugs, sea hares elongated body with foot below for gliding microscopic to 1 M long; most 1-8 cm mantle secretes shell and forms dorsal surface of animal marine, freshwater and terrestrial representatives in slugs the mantle forms a hollow breathing à virtually every mode of life except aerial chamber

marine: littoral to deepest ocean Shell some pelagic in open ocean some brackish most have a single heavy shell for defense freshwater: rivers, lakes, streams ponds, etc tropics to poles some shells with

terrestrial: woodlands, pastures, , cliffs, some specialized for climbing a few have no shell usually sluggish and sedentary snails are very well protected: some sea slugs are brightly colored àgenerally secretive habits

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 31 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 32 àstrong shell, some with door tortion àsome can produce toxic

à brings gills up front for better àsome can deliver an active blow with sharp operculum to deter

attack à makes more room in shell for retraction

àsome can even redeploy stinging cells from cnidarian prey à but puts anus over head; greater chance of fouling mouth

still many are eaten by , fish, & some shells also show spiral winding instead of mammals straight coil

and parasitized by a variety of helminths makes shell more compact

slugs have lost their shell but unbalanced à shell tipped over

(but still produce one temporarily during ) gills, auricle, and kidney on right have been lost most shells show some degree of coiling; a few do this assymetrical loss helped reduce fouling of not tortion

coiling occurred early in the fossil record of à water is brought into left front side of gastropods shell and out right side of shell

all living gastropods, whether coiled like snails or uncoiled like limpets and slugs, descended from coiled ancestors Locomotion in addition to coiling, some animals also show tortion unlike other molluscs, gastropods glide on their “foot” by secreting a mucus trail tortion was a separate evolutionary event from coiling; occurred later in a wave of muscular contractions propels them along animal begins with basic bilateral symmetry but becomes assymetrical due to tortion

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 33 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 34

it takes a lot more energy to move this way than it does to run, walk, swim or feed on dead and decaying organisms

the “most expensive” part is mucus production 4. some are carnivores

many snails follow the mucus trail of other feed on a variety of animals snails to conserve their own mucus eg. other mollusks, especially bivalves; soft , fish, worms, etc Feeding & Digestion some carnivores can follow chemical trails to wide variety of feeding types in the group locate their prey

1. most gastropods are often have a long tubelike proboscis that they can thrust between the shells of bivalves and a. use radula to scrap algae off of hard surfaces kill and digest prey such as rocks some use to subdue their prey eg. aquarium snails

eg. cone shells b. some are browsers one of the most specialized of the group eg. holds with foot and breaks off pieces with radula to eat radula consists of individual teeth; each charged with a highly toxic venom c. some are feeders when prey is located the extends wormlike proboscis they drift in plankton as they eat algae to attract prey, eg a fish

2. some are filter feeders its proboscis is loaded with one of its toxic teeth

when close enough, the tooth is expelled like a harpoon to eg. limpets use cilia to draw in water current with food paralyze the prey particles then filters out food this allows a slow moving predator to catch often a 3. others are much faster prey such as fish

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 35 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 36 the stings of some species are lethal to humans some sea slugs are able to harvest chloroplasts from eg. moon snail () & oyster borer () the algae they eat and use them temporarily for

uses radula to help bore hole through bivalves

also secretes digestive chemicals to help drill through shell new data indicates that not all such slugs are able to do photosynthesis with the “stolen” chloroplasts. What are once hole is complete, snail thrusts proboscis through hole they used for? and spends hours or days feeding on prey Respiration using its radula to cut and tear off pieces of flesh

simple gills (=ctenidia) are variously modified in some predatory gastropods are pelagic or swimming aquatic forms forms that have lost their shells = Nudibranchs

eg. sea slugs terrestrial snails (=pulmonates) lack gill but have highly vascularized mantle cavity that serves as an nearly all are marine air breathing “lung”

widely distributed, mostly shallow waters some pelagic lung opens to outside through a small opening (= brilliant colors; some contain to subdue their prey )

unique coloration may be warning draw air in over moist surface of the mantle to some feed on sea anemones and corals extract oxygen

à draw color from their prey many pulmonates have returned to water and à the undischarged nematocysts of their prey are therefore must surface periodically to breath preserved and transported to the surface of their bodies and used for defense Nervous System

eg. sea sense organs: some secrete a mucus net to capture simple photoreceptors that detect light and dark

then draw their web into their mouth and eat web and all a few have image forming eyes with cornea and lens trapped food

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 37 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 38

statocysts for balance after cross copulation, each partner deposits its tactile organs – one or two pairs of tentacles one pair usually contains the eyes eggs in shallow burrows

chemoreceptors – especially in incurrent areas of some sea slugs have a “disposable penis”; after copulating, the penis just falls Reproduction it takes 24 hours to regrow a replacement monoecious or dioecious a few snails (eg ) are protandrous many gastropods perform elaborate courtship ceremonies they live stacked on top of each other

in some, courtship can last up to 20 hours each begins life as a male

some use a syringe-like stylet to inject their paretner’s brain with the original male reproductive tract ‘manipulative’ chemicals while to enhance their degenerates and the animal regenerates success either a female or another male tract many terrestrial snails eject a dart from dart sac à if attached to a female males will remain males into partners body to heighten excitement before copulation à if too many males in the “pile” then some will become females some hold onto the dart and use it as a dagger, once female, they remain female for life stabbing their partner up to 3000 times during

mating a few primitive gastropods eject and eggs into

water it contains a chemical that improves chances

of their sperm fertilizing the other’s eggs in aquatic forms eggs may be attached to substrate or

float freely in plankton as hermaphrodites, they often cross fertilize each other some marine forms enclose eggs in wide variety of Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 39 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 40 tough capsules Class: Cephalopoda

eg. welk 800 living species; 10,000 fossil species a few freshwater forms brood their eggs in oviduct or means “head foot” the main mass of the animal bear live young (ovoviviparus)

with a cluster of prehensile arms and tentacles extending from one end

include squid, octopus, nautilus,

extensive fossil record back to Cambrian

dominant life in ancient oceans after declined

all marine

2 cm to 60’ (giant squid, weighs almost a ton)

giant squid is most massive invertebrate

recent genetic analysis indicates that giant squid (Architeuthis dux) anywhere in the world are all members of a single global population.

the young apparently disperse globally the settle as adults in one place

most active & most advanced of all molluscs

à some argue: most advanced of all invertebrates

Shell Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 41 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 42

much thicker and more muscular than in other groups most fossil forms (eg. ammonites common in Texas) had very large heavy shells kept buoyant by gas protects internal organs filled inner chambers most cephalopods are excellent swimmers today only Nautilus has a large external shell can forcefully expel water from the mantle cavity eg. Nautilus through a ventral funnel (siphon) creating

shell spiral as some gastropods “jet propulsion”

but divided into chambers allows them to maneuver quickly to flee predators

chambers not found in gastropods the funnel can be pointed to quickly move in any chambers connected by cord of living tissue = direction

can adjust gas in chambers for neutral buoyancy squid are streamlined and have lateral fins some have internal shell completely enclosed by that greatly improve their swimming ability mantle octopus is better adapted to crawling than swimming eg. cuttlefish, squid crawls over rocks and corals & into crevices using suction discs some have completely lost shell and mantle encloses on its tentacles to pull or anchor itself and protects animal some deep water octopi have webbed tentacles and eg. octopus swim like

shell was sacrificed for speed to avoid the surface of the mantle and the rest of animal is Mantle covered by pigment cells called in most cephalopods the mantle serves as the is an elastic pigment cell animals outer covering tiny muscles surround each one

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 43 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 44 tentacles and arms have rows of suction discs contraction expands chromatophore and changes color of body arms have suckers along their entire length

tentacles have suckers only at distal end allows animal to rapidly change color as gets closer to prey it can shoot out under nervous and hormonal control tentacles to quickly capture it

can produce general darkening and lightening a mouth is at center of arms flashes of pink, , lavender contains chitinous or jaws

can form bars, stripes, spots and blotches the rest of the foot is modified into a funnel for directed movement the ability to change color quickly offers considerable protection (in lieu of a shell) – provides instant Digestive System camoflage almost all cephalopods are predators also can be used for communication only the “” is not a predator

can indicate danger, protection, or used it is a using tiny mucous lined filaments to fish during courtship for organic matter

it in low oxygen zones where predators could not many forms are bioluminescent survive

Head & Foot use tentacles and arms to capture and handle prey with its suction cups in cephalopods, the head is indistinguishable from the foot strong beaklike jaws enclose tongue-like radula the “head-foot” is elongated into 8 or 10 arms (up to octopus and cuttlefish have glands to help 90 in nautilus) and 2 longer tentacles subdue prey

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 45 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 46

the beak bites pieces of prey off and the radula mantle but force water to exit through funnel for further tear it into pieces locomotion from the mouth, food travels through a long thin closed circulatory system esophagus to a small stomach à more efficient for gas exchange and transport

secretions from pancreas and liver help digest accessory (brachial) at base of each gill the food into a mush improves pumping efficiency even more food is then passed to the where digestion is Nervous System and completed and nutrients are absorbed into the (blood) for distribution largest brain of any invertebrate undigested wastes are passed to the rectum and out several lobes with millions of nerve cells the anus, and finally out the siphon more elaborate than in other classes Excretion much of our current knowledge of nerve cell function is based on studies of the large nerve fibers of the squid Kidneys extract wastes from the hemolymph and release wastes through the funnel brain is located behind mouth

Respiration & Circulation octopus and cuttlefish actual “think & plan” since the cephalopods are so active they require more learn and react to their environment oxygen than other molluscs level surpassed only by some most have 1 pr of large gills; no cilia generally considered the cleverest of all invertebrates mantle cavity expands and contracts to draw water and rival mammals in some ways over gills à more efficient than cilia masters of disguise 1-way valves allow water to enter along edges of Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 47 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 48 most versatile use of chromatophores in the animal , esp. cuttlefish verts: receptors point away from light source, are behind several layers of nerve cell and have great curiosity; can solve problems “blind spot” where optic nerve exits the

can easily learn behaviors by reward/punishment cephs: receptors are in front of the “wiring”, no blind spot, more light reaches receptors if they see another rewarded for a particular choice they will do the same thing to hopefully get the same reward statocysts: large and more complex than in other classes important in controlling eye position one octopus would short circuit the light over her tank by squirting water at it if someone forgot to turn it off at tentacles: use tentacles for tactile exploration night Protection: can use rudimentary tools most cephalopods have an ink sac for protection biologists have recently (2010) reported the first example of “tool use” by an invertebrate: along the side of rectum a species of octopus in Australia has been observed carrying around shells and pigment (same as in our skin) using them for cover when threatened

European Union has recently (2012) offered them the à creates smoke screen to facilitate escape same protections as lab rats from danger sensory organs are better developed in cephalopods Reproduction than in other mollusk classes cephalopods are dioecious eyes: most have very well developed eyes with cornea, lens retina in the male:

eyes show remarkable to eye; cornea, lens, retina, etc sperm are produced in a single large testis and pass to the vas deferens for storage differences:

verts: adjust shape of lens to focus image on retina the male packages sperm in a packet called a cephs: lens is rigid, adjust shape of eyeball to focus Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 49 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 50

male must be careful since female will often spermatophores and stores it in mantle cavity escape so quickly that she rips the arm off the male each spermatophore can contain up to 10 M sperm not too serious since male dies soon after mating in squid a spermatophore is about the size of a rice grain after several the female can select which

sperm to use to fertilize her eggs in the female:

eggs are fertilized as female lays them a single large ovary produces eggs

eggs attached to stones in long strings of 1000’s of 2 large nidamental glands produce a hard, foul eggs tasting (to deter predation) capsule that encloses

the eggs or in some species, eggs are brooded by the female

males often fight for the attention of a female female squid dies after laying her eggs

courtship sometimes includes numerous color changes direct development; no free-swimming larvae & body movements

juveniles hatch from eggs the female typically chooses her mate

generally, cephalopods don’t show parental care but a a specialized arm of male is used to transfer sperm to few cases are known: female = arm eg. one group of deep water squid carries and protects and egg sac carrying up to 3000 eggs for several months (proximal suckers are longer and thinner than on its other arms) eg. some spend months caring for the eggs they have laid male plucks spermatophore from its own mantle cavity and inserts it into females mantle cavity protecting them from predators and keeping them clean

by the time the eggs hatch the mothers are so exhausted that they die outright or easily succumb to predators Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 51 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 52 Ecological Impacts of Molluscs Major Groups of Cephalopods

1. 1. important in food webs in aquatic 2. ammonoids -all extinct and even in terrestrial ecosystems 3. - all living forms except nautilus

mollusks are eaten by a large number of animals

2. snails are major source of calcium for birds

3. oysters are keystone species since they tend to form reefs nearshore

the cracks and crevices provide homes for a large variety of animals creating a complex of interactions

4. threatened & endangered mollusks

freshwater bivalves are now the most threatened group of invertebrates in the US

some can live up to 50 years

once >300 species in rivers, lakes, etc

today: ~24 are extinct >160 endangered or threatened

11 species in Texas about to be listed in the

endangered list (2010)

especially due to: Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 53 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 54

now found throughout the hunting and harvesting & poaching voracious eaters that disrupt food chains by competing for

same food as native species were actively harvested by native americans for food,

tools, jewelry extremely fertile and can disperse at any stage of life

early settlers collected massive quantities for food and able to strongly attach to any hard surface by tough byssal pearls threads

even today 1000’s are collected for pearls & à have found 15000 attached to a single 4” often sold as food; some human consumption

able to completely bock water inlet pipes of water treatment damming rivers and power plants

pollution, highly costly to remove

have been found clinging to boats and are quickly spreading since they filter the water they are throughout the US especially sensitive to pollutants and sediment not yet in Texas but already have been found in Oklahoma

they are often the first species to disappear or decline when environmental conditions change

due to mining, industry & agriculture

5. Bioinvasives

eg. asian clam

eg. zebra

named for distinctive striped shell pattern

arrived in US in 1986 via ballast water from Eiuropean freighter into Lake Erie

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 55 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 56

Human Impacts of Molluscs natural pearls take many years to grow and are very expensive 1. : tusk shells used as (=wampum) by native Americans cultured pearls use “blank” of polished shell placed under mantle of oyster, then allows layers to deposit for 3-6 years 2. as food: oysters, scallops, mussels, octopus, squid much quicker process, much cheaper, preferred today eg. >2 Billion pounds of oysters are eaten each year 4. ink à dye oysters first cultivated for food for 2000 yrs

oyster are found from ancient roman times and are 5. from cuttle fish common at coastal archaeological sites 6. Pharmaceuticals certain species consumed cooked or raw eg. derived from venom alleviates some eg. octopus, squid & cuttlefish: 3 million tons/yr are consumed; kinds of chronic pain that even morphine can’t control an industry valued at >$6 Billion 7. Materials Science Research eg. (1990): each night 1000 SE Asian boats set out ~25,000

miles of nylon drift nets that extend about 30 ft down from eg. mussels have an amazing ability to attach to rocks. their glue the surface to catch red squid is made from protein strands that can attach strongly to

even teflon the bycatch from this nightly activity;

~2000 dolphins applications to develop aquatic glues, antifouling ~300,000 tons of pomfret (a kind of fish) paints, stronger sutures à these are discarded

1000’s tons of , , à are kept and sold on the market 8. shell collecting

3. precious “stones” 9. pollution control

shell à buttons, cameos, etc oysters consume nitrates and helping to some species of oysters and some fw clams produce pearls clean & purify eutrophic waters

generally produced when a parasite gets between the shell and mantle of the animal

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 57 Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 58

a project in Chesapeake Bay is using oyster reefs to remove 19 million pounds (8.6 M kg) of nitrogen compounds/yr from the bay waters

10. destructive species

snails and slugs à gardens

boring snails destroy oyster beds

shipworms à damage wooden ships and warves

some are not deterred by creosote treatment

some bivalves can even bore into concrete

bioinvasions; eg

intermediate hosts to parasitic helminths

Animals: Phylum Mollusca; Ziser Lecture Notes, 2015.10 59