Bio Exam III

Phylum Mollusca

Large phylum (\~100,000 species)

all types of habitats (terrestrial, freshwater, marine)

PROTOSOMES

LOPHOTROCHOZOANS

relationships to other phyla are unclear

Coelom Mollusca

first non-worm phylum with a coelom

Coelom Mollusca fuctions

room for organ development

diffusion surface for gases nutrients and wastes

storage (fat)

elimination of reproductive products

hydrostatic support

In Mollusca, the coelom is

reduced to a pericardial cavity

Phylum Mollusca Anatomy

body has 3 parts: head-foot, visceral mass, mantle

well-developed head in many; with mouth, cerebral ganglion, and sensory structures

in most, mouth contains tongue-like rasping structure called RADULA-scrapes food off substrate

foot is muscular organ for attachment, locomotion, and feeding

Phylum Mollusca: Anatomy and Maintenance

visceral mass contains organs of digestion, circulation, reproduction, and excretion; located dorsally to head-foot

**complete digestive system**

heart (3-chambered except in snails)

open circulatory system in 7 of 8 classes (blood leaves vessels and directly bathes cells in sinuses)

Phylum Mollusca: Anatomy

body partially or completely enclosed by fold of tissue called the mantle

mantle may secrete a calcareous shell in some, covers visceral mass

Mantle cavity (between mantle and foot) functions

excretion, gas exchange, elimination of digestive wastes, release of reproductive products

Phylum Mollusca: Excretion, Osmoregulation, Reproduction

**Nephridia** excrete nitrogenous wastes filtered from blood into mantle cavity

\-ammonia in aquatic molluscs

\-uric acid in terrestrial molluscs

**protonephridia** in larval stages

**metanephridia** in adults

most **dioecious**, one class with monoecious members

Phylum mollusca: larvae

free-swimming trochophore larvae in most aquatic molluscs

**veliger** larvae forms next in snails and clams; first shell

Phylum Mollusca: Diversity

8 classes

Only covered 3 in class: Gastropoda, Bivalvia, Cephalopoda

Phylum Mollusca: Class Gastropoda-Snails and Slugs

largest, most varied class (35,000 species)

**intermediate hosts** for important human parasites

marine, freshwater, and terrestrial habitats

Phylum Mollusca-Class Gastropoda continued…

single spiral shell, absent in slugs

foot flattened, modified for crawling

varied in food habits, some herbivorous, some carnivorous; radula often extendable

some have **venom** or use **nematocysts** of cnidarian prey for defense

Aposematism or Aposematic coloration

bright colorations that serve as a warning that an animal is noxious or inedible

many **sea slugs** display aposematism

Class Gastropod: Torsion

torsion-180 degree twist of visceral mass, mantle, and mantle cavity

positions gills, anus, and reproductive and excretory openings behind head

twist digestive tract into U shape

Advantages of torsion

foot is last structure in shell (not head)

allows clean water (not dirty) to enter mantle cavity

mantle’s sensory organs near head

Class gastropoda:snail shells

some left-coiled and some right-coiled snails

many organs are single (not paired) because of shape of shells

many have a covering called an **operculum** on the foot that closes the shell when the snail draws inside the shell

Class Gastropoda: Respiration

single gill in mantle cavity of aquatic forms

burrowing forms have siphon tube that reaches through the substrate to inhale oxygenated water

land snails have greatly reduced or lost gills and use their **vascular-rich mantle** to exchange gases

often called **pulmonate lung**

Class Gastropoda: Maintenance

open circulatory system

two-chambered heart (sometimes 3)

**hydraulic skeleton-blood under pressure** moves some structures (extends tentacles)

mucous gland secretes a layer of slime

Class Gastropoda: Nervous System

large cerebral ganglion in head and smaller one in foot

well-developed sensory structures

eyes, often on the end of tentacles, sometimes with lens and cornea

chemoreceptors used to locate food

Class Gastropoda: Reproduction

many marine snails are dioecious with external fertilization

terrestrial and freshwater snails are often monoecious (hermaphroditic) with internal, cross fertilization

some (but not all) terrestrial snails mutually exchange sperm

some shoot their partners with love darts-involved in sperm competition

MATING DANCE

eggs are usually laid in strings or masses

Phylum Mollusca: Class Bivalvia Members

clams, oysters, mussels, scallops

Class bivalvia

second largest class (30,000 sp)

**aquatic**, both marine and freshwater

**laterally-compressed,** soft body in a two-valve shell that are closed by two adductor muscles

sheet-like mantle inside shell; some form pearls

**no head, no radula**

Class Bivalvia: Movement

wedge-shaped foot for most movement

some creep along bottom, soome attach to solid objects, some burrow

scallops can propulsion swim by clamping valves together

Class Bivalvia: Gas Exchange and Feeding

**thin, plate-like gills** used for gas exchange and assist in feeding

feed by filter-feeding

extremely important environmentally for removing pollutants and sediment

**complete digestive system** with esophagus, stomach, and intestine

Class Bivalvia: Maintenance

specialized open circulatory system

three pairs of ganglia-associated with the esophagus,foot, and posterior adductor muscle

mantle margin is primary sense organ

may have sensory tentacles and photoreceptors (scallops have complex eyes)

Class Bivalvia: Reproduction

most are **dioecious**

marine forms-**external fertilization** and free-swimming larvae

freshwater forms-**internal fertilization**, brood young (larvae) in specialized maternal gills

some freshwater forms have larval stage (glochidia) that is parasitic on fish gills

Glochidia

parasitic larvae of freshwater mussels

freshwater mussels reproduction

some species have lures to attract host fish

Members of Class Cephalopoda

octopus, squid, nautilus, cuttlefish

Class Cephalopoda Characteristics

shell present (nautilus) or absent (squid, octopus) or reduced (cuttlefish)

\~550 species, all marine

once more diverse (\~9,000 sp); competition with fish caused decline

**among largest invertebrates** (giant squid up to 20 m)

Class Cephalopoda:locomotion

anterior foot modified into circle of tentacles, some having suction cups

mantle cavity is **funnel-shaped** and used for jet-like propulsion

muscular mantle pumps water into mantle cavity

many release ink-like liquid when disturbed

Class Cephalopoda: feeding

all have beak like jaws and a radula

predators, feeding on invertebrates (especially crustaceans) and fish

some have venom

Class cephalopoda:circulation

**closed circulatory system** (blood confined to vessels throughout body)

**systemic heart and branchial hearts** increase blood flow; very efficient

Class Cephalopoda: Nervous System

extremely complex, extreme cephalization

\-neurons well distributed throughout body

most intelligent invertebrates (can learn, have memory)

complex eyes, similar to vertebrate eyes

many have chromatophores, pigment cells that enable color change

\-some bioluminescent

Class Cephalopoda:reproduction

all species are dioecious

male transfers sperm in packets called spematophores to females with a special tentacle, **hectocotylus**

females deposit eggs on substrate (ex. ceiling of octopus’ den)

larvae develop in eggs

hatchlings resemble adults

no parental care after hatching

Phylum Arthropoda

largest animal phylum (75-84% of all animals-800k to 1 million species described)

4 characteristics contributed to their success

metaterism/tagmatization

exoskeleton

hemocoel

metamorphosis

Metamerism/tagmatization

external, but not internal (unlike annelids)

permits specialization of body regions for specific functions (tagmatization)

exoskeleton (cuticle)

covers all body surfaces and invaginations of body wall

non-living, made chiefly of chitin and proteins (some have calcium carbonate)

Arthopod exoskeleton functions

structural support-attachment sites for muscles and internal organs

protection against physical injury or invasion of pathogens

retards water loss

provides color

joint formation

Phylum Arthropoda:Hemocoel

internal cavity for open circulatory system (derived from different tissue than coelom)

organs bathed by blood to provide for exchange of nutrients, wastes, gases

true coelom forms small cavities around gonads and excretory organs

Matamorphosis

drastic change in body form and physiology in transition from larval to adult forms

reduces competition between adults and immature stages

can aid in dispersal

Phylum arthorpoda:other characteristics

paired, jointed appendages

ventral nervous system

complete digestive system

most dioecious

Subphylums of Arthropoda

Chelicerata, Crustacea, Myriapoda, Hexapoda

Subphlyum Chelicerata: Spiders, mites, ticks, horseshoe crabs, allies

2 body regions

\-prosoma (sensory, feeding, locomotion)

\-opisthosoma (digestive, reproductive, excretory, respiratory organs)

chelicera-modified 1st pair of appendages (pinchers, fangs, etc)

pedipalps-2nd pair of appendages (sensory, feeding, locomotion, reproduction)

NO antennae

Subphylum Chelicerata:Class Merostomata-horseshoe crabs

ancient group

chelicera, pedipalps, 4 pairs of walking legs with the first 3 pairs of walking legs all being chelate (pincher-like)

respiratory system-book gills

spike-like tail:telson

Horseshoe crabs

consume annelids and other invertebrates

dioecious

congregate in intertidal areas to mate

\-eggs are shed in a depression dug by female; male fetilizes externally

\-eggs are covered and unattended

4 species of horseshoe crabs alive today, one common in Atlantic and gulf

“The real blue bloods”

cerulean blood

\-contains coppers

\-contain amebocytes, protect them from pathogens

we use to make Limulus amebocyte lysate (LAL) to test items/medicines

Subphylum Chelicerata: Class Arachida-spiders, mites, ticks, scorpions,allies

4 pairs of non-chelate walking legs

chelicerae modified for piercing or chewing

mostly carnivorous

**respiratory system**-book lungs or tracheae (branched system of air ducts)

\-air enters through spiracles and circulates btwn page-like lamellae

Class Arachnida:excretion

excrete uric acid (semi-solid, little water loss) from one of 2 organs:

coxal glands-sacs bathed by blood that collect wastes and excrete through pore at base of posterior appendages

malpighian tubules-blind ending tubules of the gut tract that collect nitrogenous wastes and empties them to the gut tract (go out with digestive wastes)

Class arachnida: general characteristics

variety of sensory structures (sensilla)

excellent chemical sense

one or more pairs of eyes

dioecious, sometimes sexually dimorphic

males often transfer spermatophores (packets of sperm to females)

many tend to their developing eggs

young resemble adults at hatching

Orders of Class Arachnida

scorpionida, araneae, opiliones, acarina, pseudoscorpions

Class Arachnida:Order Scorpionida

\~1,250 species in warm climates (deserts)

nocturnal and secretive predators

pedipalps modified into large pinchers

opithosoma divided into 2 sections

\-preabdomen with body slits, chemical receptors, genital openings

\-postabdomen (tail) with stinger

venom usually not toxic to humans

courtship “dance” can last 5 min to hours

male deposits spermatophore

male positions female (through dance) over spermatophore for uptake of sperm

Order scorpionida continued…

ovovivparous (eggs develop inside female) or viviparous (nourishment from mother)

most other arthropods are oviparous (eggs develop outside female)

young carried on mother’s back

Class Arachnida: Order Araneae

widespread \~34000 species

chelicerae modified into venom glands and fangs; all are predators

some external digestion (secrete enzymes into prey)

pedipalps leg-like;modified for sperm transfer in males

variable hunting strategies (stalking, trap doors, webs, ambush)

6 to 8 eyes (in pairs)

pedicel (like a slender waist) attaches prosoma to opisthosoma

Class Arachnida:Order araneae (pt. 2)

spinnerets on abdomen emit silk

spider silk is variable and very strong

mating involves complex behaviors

mostly oviparous (lay eggs) often wrapped in silk

young disperse by ballooning

Class Arachnida:Order Opiliones Members

harvestmen

Class Arachnida:Order Opiliones

\~3,000 species

resemble long-legged spiders (sometimes called daddy longlegs)

no venom glands

many omnivores, others carnivores

oviparous, deposit eggs on ground

Class Arachnida:order acarina members

mites and ticks

Class Arachnida:Order acarina-mites and ticks

widespread:\~10,000 species

chelicerae and pedipalps modified for piercing, biting, anchoring, and sucking

many ectoparasites (feed on blood from vertebrates)

some herbivores (spider mites) or scavengers

prosoma and opisthosoma fused and covered by single carapace

some spread diseases (lyme diseae, rocky mtn spotted fever, ehrlichiosis)

follicle mites live in hair follicles

oviparous, often lay eggs on ground

6 legged larvae of ticks are called seed ticks

Class Pycnogonida members

sea spiders

Subphylum Myriapoda:Millipedes, centipedes and allies classes

diplopoda, chiopoda, symphyla, pauropoda

Subphylum:myriapoda-millipedes, centipedes, and allies

2 body regions:head and trunk

uniramous (unbranched) appendages

terrestrial

Class Diplopoda:millipedes

usually 30 or more pairs of legs, 2 pairs per segment

body usally round in cross section

worldwide in distribution

habitat-leaf litter, under decaying logs

detrivores-eat decaying vegetation

slowmoving-diurnal or nocturnal

produce repellant (hydrogen cyanide) as defense-roll

dioecious

Class Chilopoda-centipedes

usually 15 or more pairs of legs, 1 pair per segment

body usually flattened in cross section

habitat-forest floor debris or buildings (moist)

fast-moving; nocturnal

predatory and venomous, 1st pair of legs modified into venom claws (maxillipeds)

female may brood eggs and young

Subphylum Crustacea Classes

Malacostraca, Branchiopoda, Maxillopoda

Subphylum Hexapoda Class

Class Insecta

Subphylum Crustacea: shrimp, crabs, lobsters, crayfish, barnacles, and relatives

2 pairs of antennae (other arthropods have one or none)

biramous (branched) appendages

mostly aquatic; many marine forms

\~42,000 species

Class Malacostraca

some laterally compressed (shrimp) mostly swim

others are dorso-ventrally compressed(lobster, crab) mostly crawl

Class Malacostraca:body form

two body regions-cephalothorax (partially fused) and abdomen (segmented)

shield-like carapace protects soft parts of cephalothorax

abdomen of crabs greatly reduced

muscular tail (abdomen region) flexible and used for swimming

Class Malacostrac:appendages

paired appendages (n=18 pairs in most)in both body regions

first 2 pairs in cephalothorax are first and second attenae

3rd through 5h pairs are associated with mouth

\-3rd pair:madnibles for chewing/grinding

\-4th and 5th pair:maxillae-food handling and bearing gills

--the second maxilla bears a gill and thin, bladelike scaphognathite (gill bailer) that circulates water over the gills

6th thru 8th appendages

maxillipeds-acts as accessory sensory and food handling appendages

\-last 2 pairs also bear gills (7,8)

appendage pairs 9-13

pereopods (walking legs)

first pereopods, the CHELIPEDS, are modified into large pinchers for defense and capturing food

appendages 14-18

on the abdomen and called PLEOPODS (swimmerets) and used for swimming

1st pair of pleopods are modified for sexual reproduction in males into claspers (gonopods)

the final pair of pleopods are modified to be fin like UROPODS (flank the telson)

Class Malacostraca: Gas Exchange and circulation

gills attach to base of appendages and exchange gases with blood in a gill chamber under carapace

dorsal and ventral blood vessels connect sinuses of the hemocoel

respiratory pigment (hemocyanin) carries gases

muscular heart pumps blood

Class Malacostraca:nervous system

ventral nervous system with fused ganglia at each segment (similar to annelids) with largest ganglion in head region

antennae are primary receptors

many other receptors (compound eyes on stalks, simple eyes, chemoreceptors, tactile receptors on appendages)

statocyst with cemented sand grains

Class Malacostraca:excretion and reproduction

excrete ammonia from antennal glands or maxillary glands (structurally similar to coxal glands of arachnids)

gill surfaces important for osmoregulation

dioecious with copulation

females brood eggs until hatching

young resemble adults in some (crayfish), but planktonic (drifting) larvae in others (crabs)

Class Malacostraca-orders isopoda and amphipoda

most are predatory or scavengers

some are detritovores or parasitic

some crabs and pillbugs (rolly pollies) are terrestrial

subphylum crustacea-class branchipoda (brine shrimp cladocerans)

mostly freshwater

very small, many planktonic

some are parthenogenetic

many adapted to life in ephemeral pods

subphylum crustacea-class maxillopoda (copepods)

subclass copepoda

copepods are tiny and mostly planktonic

marine and freshwater

may be most abundant animal on earth

mostly filter feeding, some predatory or parasitic

subphylum crustacea-class maxillopoda BARNACLES

subclass thecostraca

barnacles have planktonic larvae, but becomes sedentary as adults

attach to rocks, ships, and animals

adults have calcareous plates (resemble shells of molluscs)

filter feed, few parasitic

exclusively marine

mostly monecious

Subphylum hexapoda:class insecta

highly successful, 75% of arthropod species

750,000 described species (some estimate 30 million species)

3 body regions:head, thorax, and abdomen

3pairs of legs on thorax

1 pair of antennae

many have wings

Class Insecta:flight

first animals to fly (contributed to their success)

wings have thickened, hollow veins for strength

limited abilites to thermoregulate (needed for flight muscles to function)

most can fold their wings over their backs

many are very maneuverable, and some can hover

Class Insecta: types of flight

direct or synchronous flight - muscles attached to wings; contract for downward thrust

\-one nerve impulse per wing beat

\-butterflies, dragonflies, and grasshoppers

\
indirect or asynchronous flight-muscles change the shape of the exoskeleton to create thrust

\-one nerve impulse for several wing beats

\-flies, beetles, and wasps

Class Insecta: other forms of locomotion

walk, run, jump, and swim

many have enlarged back legs

energy often stored as elastic energy in exoskeleton for some forms of flight (flies) and jumping (fleas)

fleas can jump up to 100x their body length

Class Insecta: feeding and digestion

four types of mouthparts: labrum, mandibles, maxillae, and labium)

mouthparts are modified for biting, chewing, piercing, licking (sponging), and sucking

long straight digestive system typical of all arthropods

foregut (muscular pharynx and crop), midgut (site of digestion and absorption), and hindgut (intestine, reabsorbs water)

Class insecta:gas exchange

tracheae-branched chitin-lined tubes that open to the outside via spiracles

\-most branched in metabolically active tissues (flight muscles)

\
most insects have ventilating system (various strategies-muscle contraction or biochemical vacuums) to move air

\
aquatic insects have gills or diffuse gas across body walls (some carry bubbles underwater)

Class Insecta: circulation and excretion

circulatory system similar to other arthropods but less developed (blood not used in gas exchange if terrestrial)

some insects (moths) generate heat by rapid contraction of flight muscles

in the winter, bees use shivering thermogenesis for warmth

excrete uric acid via malpighian tubules (like some spiders)

Class Insecta: nervous system

similar in structure to nervous system of annelids and other arthorpods

SUPRAESOPHAGEAL GANGLION occur along the ventral nerve cord

some functions (mating) occur even if the head is removed

some insects are capable of learning and memory

Class Insecta: sensory organs

excellent chemoreceptors and touch receptors (numerous hair-like setae)

many insects can hear with Johnston’s organs (at base of antennae) or tympanal organs (in legs, abdomen, or thorax)

all insects detect light

most have compound, multi-faceted eyes

\-best used for detecting motion

\-can detect ultraviolet light

and simple eyes:ocelli

\-best used for regulating daily rhythms

\-sensitive to changes in light intensity

Class Insecta:chemical regulation

like other arthropods, insects have endocrine glands that release hormones which control biological processes (molting)

pheromones are released chemical that cause behavioral or physiological changes in other individuals of the species

\-sex pheromones attract mates

\-alarm pheromones warn others of danger

Class Insecta:reproduction

most have complex mating behaviors and internal fertilization

pheromones(moths), visual signals (fireflies), or auditory signals (cicadas) may be involved

females of many species deposit eggs with an ovipositor

3 types of metamorphosis

ametabolous, hemimetabolous, holometabolous

Ametabolous development

immature stages like like small adults

silverfish

Hemimetabolous development

immature stages (nymphs) differ from adults

aquatic immature stages:naiads

gradually assume adult form

grasshoppers, bugs, dragonflies, mayflies

Holometabolous development

immature stages (larvae) very different from adult (75% of all insect species)

resting stage called pupa

butterflies, houseflies, wasps

Social insects

some insects (especially bees, wasps, ants, and termites) have highly developed social systems

sterile working castes with only one or few breeding females (queen)

colony acts as a superorganism

evolutionary origin has caused much debate

Insects are essential to ecological functions

food web dynamics

pollination of plants (65% of all plant species)

soil aeration and decay processes

some produce human-consumed products (honey, silk, wax)

some are pests

some spread diseases

Big 4 (Insecta Orders)

Order Coleoptera-beetles (350,000 sp)

Order Lepidoptera- moths, butterflies (180,000 sp)

Order Diptera- flies (120,000 sp)

Order Hymenoptera- ants, bees wasps (115,000 sp)