Acoelomates with Radial Symmetry Flashcards
Acoelomates that have radial symmetry
Cnidaria and Ctenophora
Radial Symmetry
NO front/back, NO left/right; ONLY have endoderm (internal) & ectoderm
(external) tissues(DIPLOBLASTIC); NEITHER Protostomenor Deuterostome, not characterized in this way; NOT SEGMENTED
Cnidaria
highly diverse –include jellyfish, box jellyfish, corals, sea anemones,
Portuguese Man O’ Wars; Marine & Freshwater Predators
Cnidaria: species body forms and stages
Most species have two body forms/stages –Polyp & Medusa
however, corals & sea anemones ONLY have POLYP stage
Polyp Stage of Cnidarians
less mobility than medusa stage, generally attached to substrate; bodies & tentacles lined with stinging cells (nematocysts); used for feeding (predators) and protection
typically use asexual reproduction (budding)
Both life stages(polyp and medusa) have gastrovascular cavity for digestion of prey captured using tentacles & stinging cells
What Cnidarian only has the polyp stage?
Hydra: freshwater, no medusa stage
Medusa Stage of Cndiarians
very mobile, free-swimming, can develop from polyps; bodies & tentacles lined with stinging cells (nematocysts) –used for feeding (predation) and protection from predators
use sexual reproduction, produce sperm/egg, released into
water where fertilization occurs
Both life stages(polyp and medusa) have gastrovascular cavity for digestion of prey captured using tentacles & stinging cells
Nervous systems of Cnidarians
ALL cnidarians have well-developed sensory systems, with large nerve net to detect prey & predators…
nerve net has chemosensory (to detect dissolved substances & scents) and mechanosensory (to detect movement) abilities
integrating these sensory abilities with stinging cells leads to
high prey capture and low predation risk
Nematocysts
stinging cells lining body walls and tentacles; once triggered, stinging cell firing is one of the fastest known cellular processes
Jellyfish: Notable species
IRUKANDJI (box jellyfish): can be deadly (5 mm long), 1-m long tentacles
IMMORTAL JELLYFISH – can go back and forth between immature polyp
stage and reproductive medusa stage –seemingly never dying, just
changing form
Freshwater jellyfish example
Craspedacusta sowerbii: invasive and native to Asia, found here
Portuguese Man O’Wars
Not true jellyfish, they are SIPHONOPHORES; floating colony of individual polyps and medusae that all have specialized tasks (feeding, defense, reproduction, float); all physiologically integrated; tentacles up to 150 ft long
Sea Anemones
only in POLYP form; limited movement (sessile); have mobile larvae – nematocysts all over organism
Known for mutualism (+,+): clownfish –gain protection,
nesting site, food scraps from anemone; anemone –protection, clownfish eat parasites, get fish feces for nutrients
Corals
individual polyps living in calcium carbonate shells that secrete form reef complexes over millions of years; as they die, leave calcium
carbonate shells behind, resulting in reef growth; very high species diversity, Host even higher species diversity of animals/protists
Chemoorganoheterotroph!
Coral structures
have clear RADIAL symmetry; each coral polyp is lined with stinging cells; only has polyp stage
Each coral animal has a calcium carbonate shell, polyp is within this shell
each polyp has ZOOXANTHELLAE living on it, which are mutualistic protists/DINOFLAGELLATES that are PHOTOAUTOTROPHS; supplying energy, carbon to coral animal (up to 90% of the animal’s needs), gain nutrients/CO2 & structure
in return –CORAL ANIMAL CAN’T SURVIVE WITHOUT THEM!!
