Locomotion - Aquatic Flashcards
Lecture 4 - peer
Aquatic locomotion
Water is a 3D environment
More resistance when moving through water compared to air.
Less gravity and more buoyancy.
Forwards frictional drag, body shape is important in reducing friction.
How to counteract low or neutral buoyancy?
Fats
Ionic solutions
Air
How is air used to increase buoyancy?
Better than fat or ions to achieve neutral buoyancy.
Air-filled chamber to maintain buoyancy - can be problematic for deep diving (hydrostatic pressure)
CUttlefish uses cuttlebone for buoyancy. - underlying epithelium regulates the osmotic composition fluid that partially fills the chambers.
Locomotion types of aquatic invertebrates?
Rowing
Oscillation
Undulation
Jet propulasion.
What is rowing?
HYdrodynmaic drag from rowing movemnets of rear leg produce forward thrust during the forward phase of swimming. (eg. Diving beetles)
What is oscillation?
Two types of fin movements - more of a spectrum although there are extremes.
What is undulation?
Involoves sinusodial waves passing down body/fin/fins.
Creates a “frilly” movementthat propels the animal forward through the water column.
What is jet propulsion?
Thrust can be generated by expelling water from different organs or cavities - mantle cavity of a squid, chamber if dragon gly larvea, gastrovascular cavity of jellyfish.
Jet propulsion creates movement of the animal in one direction and is achieved by the expulsion of water in the opposite direction, typically from specialised cavity.
Jet propulsion mechanim
The mantle cavity is first filled with seawater.
The squid contracts its muscular mantle to send water out of its siphon (jet orifice). The siphon is highly flexible - it can point in any direction and contract independently of the mantle.
Check how the arrows of “swimming direction” and “Jet direction” are opposite to each other!
What are specialized fins?
(squid example)
A great example of an invertebrate with specialized fins is the squid (cephalopod). Many squid species are denser than seawater, meaning they would sink without counteracting mechanisms. To counteract sinking, squids use a unique combination of jet propulsion (next slide) and fin activity to swim.
A squid can oscillate and undulate its lateral fins (red arrows below), moving them synchronously or independently, to generate lift and create fine manoeuvres.
Fin shape and size vary greatly between squid species, providing information on how they are being used but also where the species lives in the ocean.
A mechanically optimal method of swimming with elongated fins has evolved independently at least eight times in both vertebrate and invertebrate swimmers across three different phyla.
Check in red which invertebrates have these specialized fins!
How does a sea star move?
A true coelom modified into a circulatory system - water vascular system
Madreporite – special skeletal plate – controls opening to exterior
Stone canal – has ring canals and radial canals (one for each arm)
Tiedemann’s bodies – coelomocyte production. Part of stone canal
Polian vesicles – pressure regulators. Part of stone canal
Lateral canal – ending in tube foot. Consists of ampullae (hydraulic pressure regulator) and podium (hollow, muscular)
Ampulla – fluid reservoir used to operate the podium
Lateral canal valve – isolates tube foot from the rest of the system.
Ampulla contracts – forces fluid int podium – sucker pressed against surface – adhesion with mucus
Podium contracts – fluid forced back into ampulla – tube foot released from surface
