Chaetognatha Flashcards
synapomorphies (5)
Bilaterally symmetrical, torpedo-shaped marine predators.
Possess grasping spines (chaetae) on the head, used to capture prey.
Transparent or translucent body with fins.
Have a coelom, but their exact classification among bilaterians is debated.
Exhibit both protostome and deuterostome characteristics, making their
evolutionary relationships complex.
body form adult
Size: Typically 2–120 mm in length.
body wall and support
Body Wall: Covered by a thin, flexible cuticle.
Support: Hydrostatic skeleton (fluid-filled coelom provides structure).
locomotion (2) and body cavity
Locomotion:
-Move using longitudinal muscles for rapid darting movements.
- Stabilized by paired lateral and caudal fins (though not true vertebrate
fins).
Body Cavities: Coelomate, with a divided body cavity.
feeding/digestion (3) and circulation
Nutrition (Feeding/Digestion):
- Predators feeding on plankton, small crustaceans, and fish larvae.
- Capture prey with spiny grasping jaws, then inject neurotoxins to
immobilize it.
- Digestive tract is a straight tube from mouth → gut → anus.
Circulation: No heart or specialized circulatory system; coelomic fluid helps
distribute nutrients.
Excretion (2) and respiration
Excretion (Osmoregulation):
- Excrete waste via diffusion across body walls.
- Some species have protonephridia for osmoregulation.
Gas Exchange (Respiration): Oxygen diffuses through the body surface.
nervous system (3)
Have a simple dorsal brain and ventral nerve cord.
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Possess sensory bristles (mechanoreceptors) for detecting water
movement.
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Have ocelli (simple eyes) that sense light.
Reproduction and development (3)
Hermaphroditic (each individual has male and female reproductive
organs).
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Internal fertilization; sperm are exchanged using spermatophores.
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Direct development (no larval stage); hatchlings resemble miniature
adults.
habitat (3)
Exclusively marine, found in both coastal and deep-sea environments.
Mostly planktonic, drifting in the water column.
Some species exhibit vertical migration, moving deeper during the day to avoid
predators.
what are they also called?
Sometimes called “tigers of the plankton” due to their predatory nature.
what poison do they have?
tetrodotoxin
evolutionary position
Their evolutionary position is controversial—they share traits with both
protostomes and deuterostomes but do not fit neatly into either group.
role in the environment
Play an essential role in marine food webs, serving as prey for fish, whales, and
larger invertebrates.
