LECTURE 13 STUDY GUIDE (SPONGES AND CNIDARIANS)

in what phylum are sponges classified?

poriferan

which characteristics characterize sponges?

asymmetrical, sessile, filter-feeding metazoans that lack true tissues

what habitat do sponges live in?

mostly marine, few in freshwater

what are the three constituents of a sponge?

colony of cells, mesohyl matrix, and structural elements (CaCO3 or SiO2 spicules and protein fibers)

a sponge colony is comprised of three general types of cells. what are these cell types called and what functional role(s) does/do each serve in the colony?

1. epidermal cells —> envelop the sponge

2. amoebocyte cells —> found in mesohyl, transfer food, produce gametes, and produce spicules and spongin for structure

3. choanocytes —> flagellated cells that move water through a sponge so their microvillus collars can filter food via phagocytosis

what is sponge colony matrix material called?

mesohyl

what is asconoid?

flagellated spongocoel, simplest canal system

water enters through the ostia and exits through a large osculum

what is syconoid?

flagellated canals

like an asconoid but has thicker walls allowing for greater size

walls are folded for increased surface area used for feeding

what is leuconoid?

flagellated chambers, most complex canal system

permits and increase in sponge size

walls of the small chambers filter all the water filtered through and spongocoel is reduced

common in most sponges

allows sponges to maintain water flow even after choanocytes have been poisoned

rank asconoid, syconoid, and leuconid sponges based on their degree of surface area

asconoid<syconoid<leuconoid

what is significant regarding the degree of surface area in the life of a sponge?

larger surface area allows sponge to sieve food from water quicker

what is a pore or ostium (-ia) in a sponge?

allows water to come in

what is an osculum(-a)?

acts like a mouth, allows water to go out

another type of pore

how do sponges reproduce asexually?

via fragmentation

what is the general life cycle of a sponge?

amoebocytes (2n) divide by meiosis to produce flagellated sperm (n) that exit oscula

sperm enter pores or ostia of nearby sponges

those with eggs (n) in their mesohyl are fertilized

ciliated larvae swim from a few days and become sessile

are sponges monoecious or dioecious?

they are monoecious but are sequentially hermaphroditic

what does the phrase sequential hermaphroditic mean?

they can be one sexual morphology at a time

what is a sponge larva called and what role does it serve?

ciliated larvae and it swims for a few days and sticks to something then it begins its growth as a sponge

in which phylum are jellyfish and their relatives classified?

cnidaria

which characteristics characterize cnidarians?

radially symmetrical, eumetazoans, with stinging cnidocytes

in what habitat do cnidarians live?

marine/ocean

are cnidarians diploblastic or triploblastic?

diploblastic

what germ layers do cnidarians develop?

epidermis (from ectoderm) and gastrodermis (from endoderm)

what is cnidarian matrix material called?

mesoglea matrix

what do cnidarians use their gastrovascular cavity for?

used to digest and disperse food throughout a polyp or medusa

how many openings does the gastrovascular cavity have>

only one and it serves as the mouth and the anus

describe the nervous system in a typical cnidarian

nerve-net to coordinate incoming sensory information from photoreceptors and statoliths (orientation)

what do cnidarians use their contractile microfilaments for?

change shape, swim, and feed

what is a polyp?

the sessile, tubular form of a cnidarian with the oral and tentacles at the top and the aboral at the bottom (think of a squid)

what is a medusa?

umbrella-shaped body form of a cnidarian in which the oral and tentacles are on the bottom and the aboral on top (think of jellyfish)

it is motile

what kind of symmetry does the polyp and medusa have? where are their tentacles?

radial symmetry and tentacles are on the oral side

what is a tentacle?

slender, flexible limb or appendage in an animal especially around the mouth of an invertebrate

used for grasping, moving about, or bearing sense organs

what is a cnidocyte?

stinging cell

what is a cnide organelle?

organelle that cnidocytes possess

what is a nematocyst?

protein capsule filled with a coiled thread-like tube that everts as it penetrates flesh releasing venom into prey

how are nematocysts discharged?

tactile tripping of the trigger or chemoreception

what do cnidarians do with their nematocysts?

entangle, capture, and paralyze prey

how does venom differ from poison?

venom is injected while poison is inhaling, absorption, or swallowing

what are the four major taxa of cnidarians?

hydrozoa

scyphozoa

cubozoa

anthozoa

what are the three examples of hydrozoans we explored?

portuguese man of war (physalia)

colonia polyps (obelia)

hydra

most have polyps and medusae and small

live in marine habitats

what is a physalia?

colony of specialized polyps that appear as a single individual

float is smaller than a football with tentacles 1-10 m long

what is a hydra?

inhabits fresh water and it does not have medusa morph in its LFC

reproduces asexually by budding

cooling water temps stimulates formation of gonads and sexual reproduction

most species are dioecious

fairly motile

what is a obelia?

grows as an asexual poly colony (2n) whose hydranth polyps feed and distribute food

has medusae (2n)

how does the obelia reproduce?

gonangium polyps asexually bud dioecious medusae (2n) that make and disperse gametes (n)

fertilization occurs in the water forming a diploid zygote

zygote forms into a ciliated planula larva (2n) and attaches to substrate and forms a new polyp

what two characters do scyophozoans tend to possess?

dominant medusa stage and oral arms

what is the life cycle of the moon jelly, aurelia?

medusa —> planula (larva) —> scyphistoma (polyp) —> strobilia (asexual reproduction) —> ephyra (young medusa)

what occurs during strobilization?

asexually reproduces ephyra larvae (immature medusae)

which two characters do cubozoans tend to possess?

venomous and have complex eyes located in the margin of their bells

why is the sea wasp (chironex fleckeri) feared by humans?

tentacles have extremely painful venom that can be acutely fatal due to cardiac arrest

what are anthozoans?

flower animals that are marine polyps known as corals, sea anemones, and sea fans

which morph do they exclude from their life cycle?

lack a medusa stage because they are polyps throughout their life cycle

anthozoans tend to be sessile. what does this mean?

fixed in one place, does not move

coral reefs are often considered the tropical rain forests of the ocean. why?

biodiverse habitats that sequester massive amounts of carbon

what happens to corals ability to accrete CaCO3 in an acidifying ocean?

becomes an exoskeleton and that is what forms the rocky structure of the corals

as CO2 concentration in the atmosphere increases so does the concentration of CO2 in the ocean. how does the increase of oceanic CO2 impact the ocean’s pH?

makes less HCO3- dissociate to CO3 2- to combine with Ca2+ to make CaCO3

what are zooxanthellae?

photoautotrophic dinoflagellate symbionts that form mutualism with most species of corals imparting their specific colors

why are they important for most corals?

90% of their energy comes from the metabolism of symbiont photosynthates

if the symbionts die, so do the corals

what happens to coral reeds when zooxanthellae leave or die?

reef bleaches white and dies

what factors are known to harm zooxanthellae?

when atmospheric CO2 rises, ocean temps rise which causes the zooxanthellae to leave/die because its too hot/polluted

what likely happens to other species that depend on coral reef after it bleaches?

species who rely on coral reefs to hide/breed will likely go extinct/have reduced population