Class Cephalopoda Flashcards
(23 cards)
What are some characteristics of their lifestyle?
- active
- pelagic
- predatory
What are some molluscan characteristics of cephalopods? (4) Are any modified?
- Have Radula
- Ctenidium (but is non-ciliated)
- Shell-secreting mantle (but reduced or lost in most extant species)
- The foot
Distinctive characteristics of Nautiloids (2)
- Septate shell
2. Modified foot
What is the septate shell?
Heavily calcified external shell internally divided by septal partitions (has many internal chambers)
How is the foot modified?
- Prehensile appendages on anterior end (arms/tentacles)
2. Funnel (where water escapes mantle cavity)
How do we know the tentacles and funnel were derived from the foot?
Nerves from pedal ganglia innervate arms and tentacles
What are the 3 subclasses?
Nautiloidea
Ammonoidea (extinct)
Coleoidea
How are the tentacles of Nautilus distinct?
No suckers
Do they use their air chambers to undergo diel-vertical migration?
No. Manipulating air: fluid ratio WOULD alter buoyancy BUT takes too long
How do they undergo diel-vertical migration?
Muscular contraction of the muscle (brings water into mantle cavity and jets out)
What are the internal separations of a nautiloid shell? What fills these with gas?
- Septa
2. Siphuncle->tubes that runs in between shell perforations
What have squids lost? How has this changed their mantle?
- have lost shell
- mantle has become extremely muscular
How are the appendages modified in squids?
- Appendages in form of 8 shorter arms and 2 longer tentacles
- Tentacles have suckers only at tips
How do squids they do gas exchange?
- muscular pumping of mantle cavity pumps water in
- water enters mantle cavity on either side of head, pass past gill filaments and out funnel
How do fast vs slow contraction of the mantle cavity cause differences in the motion of the squid?
Fast: jet propulsion locomotion by jetting water out funnel
Slow: just for breathing
How is water sucked into the mantle?
Radial muscle contraction expands the volume of the mantle cavity to create negative pressure (and seawater sucked in on either end)
What type of predators are squids?
What feature enables this?
- Visual predators
- Image-forming eyes
What are 4 features of the circulatory system?
- Closed (capillary beds)
- systemic and branchial hearts
- high pressure for rapid circulation to deliver oxygen to tissue
Other molluscs vs cephalopods circulatory system
- Cephalopods have branchial, systemic hearts and capillaries
- Others have only 1 heart and interconnected haemal spaces
What does the high metabolic rate of squids require? (3)
- ventilation of gills by muscular pumping of mantle
- closed circulatory system (capillary beds)
- branchial/systemic hearts
How do cephalopods change colour?
Chromatophores
-contract to look more white and expand to colour themselves
Reflectors to display dif colours of light
What is unique about the flamboyant cuttlefish?
- toxic venom
- aposematic colour warning
How does cephalopod reproduction work?
- average lifespan is ~1yr
- lay eggs on substrate
- no free-swimming larval stage
