Phyla Study Guide Flashcards
Synapomorphies of Hemichordata
Stomochord - flexible, hollow tube (possible homologue to nerve chord)
No brain or prospects (nerve net and longitudinal nerves)
3 distinct segments - anterior prosome (proboscis)
intermediate collar (dorsal neural tube, nerve network)
posterior trunk (digestive tract, gonads, stalk, gill slits)
What is the Enteropneust larval form called? (Hemichordata)
Tornaria larva
What is the function of the Hemichordata proboscis?
it’s muscular and ciliated, making it the primary contributor of movement, but also helps in collection and transportation of food particles and burrowing
What makes nematodes pseudocoelomates?
they have a false coelom, and their endoderm is disconnected from their mesoderm
What is a stylet and how is it used in nematodes?
a hollow feeding structure inserted into prey (plant or animal) to suck nutrients out or inject digestive enzymes. used by parasitic organisms
How do nematodes acquire and digest their food?
food enters through the mouth and goes through Peristalsis, where the mesoderm (muscular layer) contracts and squeezes the endoderm, pushing food through the digestive tract
How do xenacoelomorphs move?
They have fully ciliated bodies that aid in locomotion
How do xenacoelomorphs reproduce?
They are hermaphrodites that are capable of sexual or asexual reproduction. They can brood or encapsulate their eggs. Direct development, regeneration.
How do acoels from xenacoelomorpha feed?
can use eversible pharynx, those without a pharynx form a sphincter around the mouth using muscle fibers. they have a syncitial gut. larger prey are coated in mucus and slowly moved towards the mouth via epidermal cilia
how do nemertodermatids from xenacoelomorpha feed?
they use a cone of gut tissues to function as a tongue and grab food, some even have an eversible proboscis called the “broom organ”, and they have a well-defined lumen rather than a syncitial gut
how do xenoturbellids from xenacoelomorpha feed?
they open their mouth and protrude their unciliated foregut
synapomorphies of xenacoelomorpha
bilateral symmetry, acoelomate body plan, xenacoelomorphan ciliated epidermis, midventral mouth, incomplete digestive system without an anus, direct development
What xenacoelomorphan species can fully regenerate and what class are they from?
symsagittifera roscoffensis (mint-sauce worm), acoela
What genus is parasitic in holothuroid guts?
Meara stichopi
synapomorphies of sipuncula
unsegmented coelomates, soft-bodied (separated by sac-like trunk and retractable introvert, introvert bears a mouth with an array of tentacles at distal end), pair of nephridia (maintain osmoregulation and have reproductive uses), unpaired nerve cord
how do sipuncula feed?
mostly deposit feeders, use tentacles to eat food particles from sediment, those on hard surfaces use introvert hooks to scrape off sediment
how do sipuncula reproduce?
most are dioecious (separate male and female reproductive organs), gonads release gametes into the coelom where they mature before being released into the water column by nephridium
What is the purpose of the nephridium in sipuncula?
maintains osmoregulation and releases fully developed gametes into the water column
What are the larval forms of peanut worms?
pelagosphera and trochophore
What is the nuchal organ in sipuncula and what is it used for?
a ciliated pit structure used for light and food detection as well as finding mates (found in class phascolosomatidea)
what genus of peanut worms are suspension feeders?
themiste
what are the 2 classes of sipuncula and what are the main differences?
sipunculoidea and phascolosomatidea, sipunculoidea doesn’t have a nuchal organ
synapomorphies of phoronida
3 body parts each with coelomic cavity (epistome - overhang on mouth, mesosome - lophophore and regenerative mass of specialized tentacles used for feeding and respiration, metasome - trunk), lophophore, no valves, ampulla (bulbous mass at end of trunk), nerve ring, bilateral symmetry, closed circulatory system
how do phoronids feed?
ciliated tentacles move water towards the oral ring with food particles trapped in mucus. once it reaches the mouth food is drawn in and moved to the digestive tract
how do phoronids reproduce?
sexual reproduction, mostly hermaphroditic, eggs or larva brooded in body cavity until secreted,