lecture 5 - 09/10/24 Flashcards
What is phylum ectoprocta?
moss animals
typically small, aquatic, filter feeders that form sedentary colonies
filter feeding accomplished using a lophophore
sometimes referred to as phylum bryozoa
~6000 described species
What is a lophophore?
a ciliated, tentacular organ that surrounds the mouth
describe ectoproct morphology
zooids are superficially similar to coral polyps - different internally
filter feeding and respiration accomplished via lophophore
- mouth leads to a U-shaped gut that terminates just
outside the lophophore
body wall secretes an exoskeleton, which in some species is biomineralized
- soft body can be retracted inside for protection
reduced cephalization, no obvious excretory or circulatory systems
zooids are physically connected via body wall pores and/or tubes made of connective tissue
How are zooids specialized?
a colony’s zooids are often functionally specialized
- zooids for gamete production, colony anchoring,
colony defence
e.g. avicularia - non-feeding zooids with bird-like
pinching beaks
- zooids have biomineralized, hinged exoskeletons,
muscular bodies, no lophophores
- anti-predator defence
describe ectoproct ecology
most are marine, some groups are successful in freshwater habitats
a few species are reef-builders (bioconstructors)
- e.g. australia’s western port bryozoan reef
lots of variation in colony morphology
- colony form is associated with environmental factors like depth, substrate stability and sedimentation rate
Describe ectoproct reproduction and development
colonies are hermaphoditic
- individual zooids may be hermaphroditic or
male/female
sex typically involves broadcast spawning of sperm, followed by internal fertilization and brooding of embryos
larvae metamorphose (indirect development) and establish new colonies via asexual budding
many freshwater species undergo seasonal asexual reproduction
- produce statoblasts - embryonic stem cells
(survival pods), can survive unfavourable conditions
then develop into zooids when conditions improve
How are ectoprocts relevant to humans?
biofueling - colonies grow on ships, pipes causing damage and blockages
potential source of bioactive compounds
(the bryostatins - drug discovery)
- actively being studied as a potential treatment for
Alzheimer’s disease
- produced not by the ectoprocts themselves, but by
the bacterial symbionts
How are ectoprocts ‘simple’ lophotrochozoans?
ecologically reminiscent of filter-feeding poriferans
morphologically reminiscent of sessile cnidarians (superficially at least)
bilaterally symmetrical, but have limited cephalization
lack key organ systems (circulatory, excretory) that were seen in molluscs and annelids
the evolution of the bilateria is associated with increased complexity, but not a universal trait across all groups
- complexity can be lost
What is phylum platyhelminthes?
free-living flatworms
dorsoventrally flat, bilaterally symmetrical, non-segmented worm
triploblastic but lack a coelom (acoelomate)
they are lophotrochozoans according to molecular data, yet have neither a lophophore nor a trochophore
~30000 described species, with ~20000 of them being parasites
describe turbellarian morphology
dorsoventrally flattened, cephalized body plans
the gut is ‘blind’ (no anus) and the mouth is ventral and often situated far from the head of the worm
they lack circulatory and respiratory systems
- flattened body plan - (in some cases) branched gut provides high SA:V
have organ systems dedicated to excretion and gamete production (including copulating structures)
acoelomate - body lacks coelum
interior is filled with connective tissue and musculature
coordinated waves of muscle action cause the worm to ripple, facilitating crawling or swimming
the ventral surface covered in cilia and mucus-secreting glands, can also be used for locomotion (gliding)
describe turbellarian reproduction
asexual reproduction via budding and dividing
- freshwater planarians are models for studying
regeneration and stem cells
- in some tiny bits can regenerate into complete
individuals
sexual reproduction is widespread
- most are simultaneous hermaphrodites that
fertilize via reciprocal copulation, and lay eggs
- some have modified penises that function as
needles (penis fencing)
describe turbellarian development
protostome-like development seems to be the ancestral state, but some undergo ‘dispersive cleavage’
- early cell division result in unconnected (dispersed)
cells, not a cohesive connected mass of cells
- the cells float freely in the egg yolk, then eventually
reunite and differentiate
both direct and indirect development is seen
larval stages are lobed with multiple eyespots
- dont resemble trochophore larvae
describe turbellarian ecology
mostly marine, but also live in freshwater and moist terrestrial habitats
most are predators, use toxins to subdue their prey
- terrestrial hammerhead flatworms eat earthworms
and may harm soil ecosystems (especially invasive)
- some marine species eat coral and are pests of
aquarium facilities
parasitism has evolved multiple times within this group
What are parasitic platyhelminths?
main group of parasitic flatworms is called the neodermata
3 subgroups - all are vertebrate parasites, but thay vary in life cycle and anatomy:
MONOGENEANS - external parasite, direct lifecycle, non-segmented
TREMATODES (flukes) - internal parasite, indirect lifestyle, non-segmented
CESTODES (tapeworms) - internal parasite, indirect life cycle, pseudo-segmented
Describe monogeneans
external parasites, usually of fish
have a direct lifecycle - infect a single host species
- infectious larvae attach to host, mature and
reproduce (via hermaphroditic crossing, selfing, or
parthenogenesis)
- eggs or larvae released, go on to infect same host
species
non-segmented body plan, but with complex attachment structures (haptors)
