lecture midterm 2 Flashcards
main characteristics of Phylum Platyhelminthes (7)
- triploblastic
- cephalization
- bilateral symmetry
- acoelomate
- gut with one opening
- unsegmented
- dorsoventrally flattened
— nervous system w cerebral ganglia and two nerve cords
— protonephridia appear
Phylum Platyhelminthes new characteristics:
- nervous system with cerebral ganglia and two nerve cords
- protonephridia appear
what do protonephridia do for Phylum Platyhelminthes ?
help with osmoregulation (maintain salt and water balance)
excretion of ammonia
reproduction: Phylum Platyhelminthes
sexual and asexual
body plan (key notes): Phylum Platyhelminthes
- start of cephalization
- no respiration or circulatory system
— rely on diffusion - cilia for motility
locomotion: Phylum Platyhelminthes
by muscular undulations/cilia/mucous
can crawl and swim
feeding: Phylum Platyhelminthes
pharyngeal glands secrete digestive enzymes — suck up semi-digested soup
some swallow prey whole
intentional hunting
diagnostic characteristics: Phylum Platyhelminthes
new characteristics of Phylum Annelida
- eucoelomate and gut musculature
- gut with 2 openings (linear digestive tract)
- metamerism (repeated body plans)
- blood vascular system (beginning of circulatory system)
- metanephridia
- nervous system
— dorsal brain
— ganglionated ventral nerve cord - chaetae/setae
lost characteristics: Phylum Annelida
flattened body plan
protonephridia
reproduction: Phylum Annelida
asexually and sexually
functions of coelomic compartments
- circulation of nutrients and gases
- hydrostatic skeleton - enables peristaltic burrowing
- role in excretion and osmoregulation (metanephridial systems)
- storage of gametes
difference between protonephridia and metanephridia
protonephridia :
- excretory tube without an internal opening
found in platyhelminthes and rotifers
— helps in osmoregulation with cilia creating pressure to move waste/excess metabolites from the animal
metanephridia :
- open to the body cavity and attached to duct that opens to exterior
found in annelids
— more efficient than protonephridia
— selective reabsorption is performed in the cells lining metanephridium
lost characteristics: Phylum Annelida
flattened body plan
protonephridia
locomotion: Phylum Annelida
peristaltic
Errantia vs Sedentaria
groups of annelids
Errantia : eversible pharynx w jaws
Sedentaria : eversible pharynx never armed w jaws
general
general characteristics of all lophotrochozoans
- true tissues
- bilaterial
- triploblastic
- protostome embryos
- either eucoelomate or pseudocoelomate
- extracellular digestion
Phylum Nemertea ‘Ribbon worms’ diagnostic feature
proboscis apparatus - hydrostatically eversible
characteristics: Phylum Nemertea ‘Ribbon worms’
- eucoelomate
- circulatory system w ciliated lateral blood vessels derived from mesoderm, brain and nervous system
reproduction: Phylum Nemertea ‘Ribbon worms’
- dioecious (2 sexes , not hermaphroditic)
- temporary gonads (transient gonads) — developing only when ova and sperm are ready
- free swimming larva
locomotion: Phylum Nemertea ‘Ribbon worms’
ciliated epidermis
feeding: Phylum Nemertea ‘Ribbon worms’
predatory - w thin proboscis apparatus, some species pierce & inject neurotoxin
lost characteristics: Phylum Nemertea ‘Ribbon worms’
chaetae/setae, metamerism (segmentation)
new characteristics: Phylum Rotifera
- eutly (fixed number of cells)
— develop by cell division until maturity then only cell growth - have lorica (shell-like protective outer covering)
- reinforced with sand grains
- closed at one end
- protonephridia
- colonial
- small cerebral ganglion
distinct characteristics: Phylum Rotifera
- ciliated corona (for suspension feeding)
- mictic reproduction (stressed cycle)
- cryptobiosis
what is cryptobiosis
helps rotifers and other species survive in fresh water
in one of their reproductive stages they can enter into this
essentially like a death state, can dry up completely, metabolism shuts down, can last for years, decades, or even up to a century — can recover in as little as 10 minutes when water is added
this makes them industrially useful - used to feed other organisms
locomotion: Phylum Rotifera
can be sessile or free swimming by movable ‘scales’ - can swim well
feeding: Phylum Rotifera
ciliated corona (suspension feeding)
predatory in some species
reproduction: Phylum Rotifera
sexually (mictic and amictic)
Phylum Mollusca characteristics:
dont have one trait that consistently runs thru all molluscs bc of such diversity
look for 4 things: (basic body plan of molluscs)
shell, mantle, foot, gills
2 major subphyla of Phylum Mollusca
Conchifera: all shell bearing molluscs
Aculifera: no SOLID shell, only spicule or sclerite bearing
Phylum Mollusca: Polyplacophorans (Chitons)
characteristics
- calcium carbonate shell w 8 pieces and shell valves
- ciliated gills (ctenidia)
- osphradia (sensory organs)
- mantle cavity
- shell attached muscles
- radula
- pericardium and gonads
- circulatory system w heart and dorsal blood vessel but then it is open
Phylum Mollusca: Polyplacophorans (Chitons)
body plan
- head
- visceral mass
- muscular foot (hydrostatic)
- mantle (pallium)
- gills (ciliated ctenidia)
Phylum Mollusca: Polyplacophorans (Chitons)
key notes on body plan:
- radula
- well developed digestive system
Phylum Mollusca: Polyplacophorans (Chitons)
diagnostic characteristics:
radula and shell valves
Phylum Mollusca: Polyplacophorans (Chitons)
locomotion:
slow moving
never detached from substrate
body regions of molluscs
visceropallium:
all collective dorsal parts (includes body organs and shell)
cephalopodium:
all collective ventral parts (includes head -mostly mouth- and foot)
Phylum Mollusca: Polyplacophorans (Chitons)
feeding:
radula w magnetite teeth (rasping and feeding)
ctenidia - cilia create water flow to increase ability to take gases out of water
Phylum Mollusca: Polyplacophorans (Chitons)
reproduction:
broadcast sperm and females retain eggs and then they are fertilized
water flow in Chitons (polyplacophorans)
from head w mouth to anus
anterior to posterior
— from ciliated water flow
clears waste — exhausted near the anus but not thru the anus
runs past paired osphradia (sensory) - olfactory or chemosensory epithelian areas near gills
Phylum Mollusca: Polyplacophorans (Chitons)
radular teeth
diagnostic trait
magnetite (Fe3O4 : loadstone) makes radular teeth very hard for scraping rock substrates
can bind these minerals to teeth to make them harder - 3 fold harder than human enamel
shows up on rocks in “fan pattern”
Phylum Mollusca: Polyplacophorans (Chitons)
nervous system:
basic nerve plan for molluscs
- related to annelids
— 2 pedal nerve cords then split into 2 areas - these 2 areas correspond to 2 body areas (visceropallium and cephalopodium)
pedal nerve cords on bottom (cephalopodium)
visceropallium nerve cords on top
ring of nerve tracks that surround pharynx
BRAIN SURROUNDS ESOPHAGUS
coelom vs hemocoel
coelom - principal body cavity in annelids, echinoderms, and chordates
- fully lined w mesothelium
hemocoel - principal body cavity in arthropods and molluscs (not annelids) - with reduced form of coelom
BOTH: structures filled w fluid and act as cushion or hydrostatic skeleton, protecting organs
Phylum Mollusca: Polyplacophorans (Chitons)
circulatory system:
Pericardium space with muscular heart is confined to just the posterior end
Blood goes anteriorly via dorsal blood vessel
Blood enters the connective tissue spaces directly, surrounding the organs in the hemocoel
Blood percolates eventually into the afferent blood vessel of the ctenidia, and is then returned to the heart
circulation looles familiar - heart in same position - no ventral blood vessel (not returning in single vessel be the blood is coming back thru the coelomic space = hemocoel
- blood entering connective tissue space directly that are surrounding organs - eventually comes back thru other vessel and denidia then back to heart
Phylum Mollusca: Polyplacophorans (Chitons)
digestion:
Digestive glands (pair)
secrete digestive
enzymes and store lipid energy
Anterior has characteristic radula, formed in deep invagination ventral to buccal cavity, secretes ribbon of teeth
now we see radula
- vegetative matter that the mollusc consumes
- posterior side to the right
- head here is just mouth in polyplacophorans
radula = constantly regenerated - teeth in radula sac
-to provide grinding motion
sac is secreting hard radula
- represents feature that we didnt have in annelids at all
Present in all extant molluscs except bivalves
Phylum Mollusca: Polyplacophorans (Chitons)
visual apparatus:
light sensing thru multiple lenses and openings on the back — called ocelli
can detect movement and shapes
made of CaCO3
Essential for sensing light regimes, hence nocturnal behavior patterns
— need to know when light and dark for feeding
Phylum Mollusca: Gastropoda
new characteristics
- shell as protective retreat — long coiled cone (chitinous operculum - hard door that seals them in)
- torsion in body plan (both internally and externally)
- development of head with tentacles and eye spots
Phylum Mollusca: Gastropoda
lost characteristic:
bilateral symmetry
Phylum Mollusca: Gastropoda
body plan key notes:
- downside of torsion is fouling of ctenidia — solved by loss of right ctenidium
- shift of anus to right side
- osphridium to left and oblique current over ctenidium through mantle cavity and out hole vent in shell
Phylum Mollusca: Gastropoda
diagnostic characteristic:
torsion - (twisted shape, not elongated like Poly- and Monoplacophorans, cephalopodium 180o from visceropallium, mantle cavity over back of head, anus opens into anterior mantle pocket, gill(s) in this anterior cavity)
evidence = cross-over of visceropallial nerve cords
Phylum Mollusca: Gastropoda
conservation biology:
scaly-foot or volcano snail - A remarkable deepsea gastropod, with metallic armour and symbiotic feeding
— just discovered and already under conservation
— International conservation bodies are largely ineffective against national policies
— Depth is no refuge from anthropogenic impact
queen conch - as they get older and reach maturity, this is when highest reproductive output. conservation and current policies only for length but should be for shell thickness at flare
abalone - density matters, if not enough wont support the population due to being broadcast spawners — population continues to fail even after stopping fishing bc of alee effect
— positive correlation between population size or density and the mean individual fitness of a population or species, usually at low populations
—POSSIBLE CAUSES OF REPRODUCTIVE FAILURE:
- Fertilization failure due to spawning distance
- Poorly provisioned trocophore larvae (malnutrition)
- Competition with other benthic organisms, and starvation
- Environmental stress
Phylum Mollusca: Gastropoda
feeding:
radula, proboscis is everted for grazing, moon snails drill into bivalves and eat them, cone snails use conotoxins, injected via proboscis to stab fish and immobilize them
Phylum Mollusca: Gastropoda
reproduction:
internal sexual reproduction
heterobranchia
Phylum Mollusca: Bivalves
new characteristics:
- new muscle arrangements for shell contraction – adductor muscle
- evolution of hinge on bivalve shell
- muscular arrangements for burrowing
- shell secretion system
- compared to polyplacophorans these are now bent over to close up (example of evolutionary change)
- Enlarged singular muscle here where in polyplacophorans there were 8 pairs of muscles
Phylum Mollusca: Bivalves
lost characteristics:
NO radula
laterally compressed body (opposed to horizontally)
Phylum Mollusca: Bivalves
why are they how they are:
shell hinges (ligaments) keep it open, muscles close it
Phylum Mollusca: Bivalves
key notes on body plans:
- laterally compressed body (opposed to horizontally)
- deep mantle cavity
- single pair of ctenidia
- new muscle for shell contraction (adductor muscle)
- dorsal hinge for shell open and close
- retaining nerve ring and dual cord structure but minimal external cephalization
—In many species: dual siphons (incurrent and excurrent siphon)
Phylum Mollusca: Bivalves
diagnostic characteristics:
- adductor muscle
- could also be dorsal hinge
- NO radula
Phylum Mollusca: Bivalves
conservation biology:
heat dome effects show drying out from osmotic stress or desiccation, leading to death (not snapping back like when cooked)
Phylum Mollusca: Bivalves
locomotion:
burrowers – deep and shallow, digging action w foot, 1. expansion of foot terminus creates anchor, 2. contraction of adductor muscle closes shell, 3. contraction of dorso-ventral muscles pulls animal down into substrate
Mussels – byssal threads hold onto substrate on exposed intertidal rocky shore
Phylum Mollusca: Bivalves
feeding:
protobranchia = deposit feeding – using ciliated palp tentacles, each tentacle has a ciliated groove carrying particles back to mouth
autobranchia = suspension/filter feeding – ctenidium used for gas exchange AND suspension feeding –> lateral cilia create water current, laterofrontal cilia intercept particles, frontal cilia carry particles down filament
Phylum Mollusca: Bivalves
defense:
hinge ligament very important – main defense mechanism bc it will snap shut when released from stretching
Phylum Mollusca: Bivalves
alternative lifestyles and feeding modes:
wood borers, septibranchia, fish parasites
Phylum Bryozoa
new characteristics:
- zooecium (exoskeleton or ‘house’)
- operculum (protective door)
- U-shaped digestive tract
- 2 coelomic compartments (lophophoral coelom and perivisceral coelom)
Phylum Bryozoa
lost characteristics:
no specialized organs (backtracking away from molluscs)
Phylum Bryozoa
why are they how they are:
colonial bc polymorphism – non-feeding non-reproductive zooid for defense purposes only = avicularium (large operculum and strong muscles, no digestive tract)
- brown bodies = not able to excrete accumulated metabolic waste so cells of the gut become storage spots for waste –> brown bodies where older zooids undergo senescence – defecate brown body and regenerate itself using stem cells – brown body ejected out
Phylum Bryozoa
key notes on body plans:
zooecium = exoskeleton (doesn’t join up which allows for passing of nutrients and for specialization)
operculum = protective door (different structure than what we’ve seen before but same function)
mesothelium
lophophore and lophophore retractor muscles
U-shaped gut (anus ejecting waste thru lophophoral sheath when tentacles extended)
anus outside of exoskeleton when tentacles are extended
Phylum Bryozoa
diagnostic characteristics:
- zooecium (house) exoskeleton – often calcified
- lophophoral coelom (comprised of the hollow tentacles
Phylum Bryozoa
locomotion:
colonial
sessil
Phylum Bryozoa
Feeding:
suspension feeders – lophophore (funnel w ciliated tentacles, goes up and brings stuff back in)
Phylum Bryozoa
Reproduction:
sexual and asexual, typically sequential androgynous hermaphrodites (male first then switch to female)
broadcast spawners - most are “spermcasters” (only sperm released, eggs retained)
sperm released thru pores in tentacular lophophoral coelom (tentacles filled w ciliated mesoderm)
then ends w free-swimming ciliated larvae
Note: this reproductive approach important for growing and expanding colonies
Phylum Bryozoa
Defensive strategies:
heterozooids (e.g. avicularia & vibracula)
colonialism (defense against partial predation)
calcification of frontal membrane (requires ascus) - hydrostatic ball w muscles can send out for defense
