Sea Creature Analysis - Jellyfish Morphology & Ecology

Jellyfish:

- Relies on NERVOUS SYSTEM to survive
- Perceive Stimuli, such as Light and Odor.
- Not Hydrodynamic
- But, not a problem, Jellies rely on current of water to move.
- Rythmically Open and Close bell shape body when in water.
- Not adapted for Closed Spaces or with walls.
- Formation of “smack” or “Bloom” of jellies is a COMPLEX SYSTEM that depends on Ocean Currents, Nutrients, Temperature, and Oxygen Content.
- Transdifferentiation

In order to swim, jellyfish contract the circular muscles that line the undersurface of their bell (also called the subumbrellar surface). This contracts their mesoglea bell. The motion of the bell from the relaxed position to the fully contracted position results in the mesoglea interacting with the surrounding water in such a way that causes the jellyfish to move forward.

The shape of the bell, the size of the velum (relative to the bell diameter) and contraction characteristics determine how medusae interact with the surrounding fluid. In other words, these traits of a medusa interact to determine the flow that a medusa generates when swimming and how they generate thrust for swimming. Consequently, prolate and oblate medusae propel through the water differently.

Bullet shaped medusae (i.e., prolate medusae) generally possess large velums relative to their diameter and contract their bells rapidly. Their shape in conjunction with their contraction kinematics results in a rapid ejection of fluid from inside their bell while entraining minimal fluid from outside the bell into their wake. Consequently, they generate swimming thrust via jet propulsion.

Flatter medusae (i.e., oblate medusae) do not generally possess large velums and they contract their bells slower than prolate medusae. Consequently, they throw large amounts of water behind them as they swim that comes from both inside and outside the bell and forms a series of large closely spaced vortex rings in their wake. In addition, as their bells expand, after each contraction, water rushes in and refills the bell in the form of a large vortex ring the rotates in the opposite direction of the ring created when the bell contracted. This motion generates swimming thrust via rowing propulsion (also termed jet-paddling).

Prey selection by prolate medusae who swim using jet propulsion and forage as ambush predators is determined by a combination of their encounter rates and retention efficiencies with different types of prey. As a result, they often are highly selective and feed on larger more motile prey. Jet propulsion is ideal for ambush foraging because, while it may be energetically expensive, it is highly effective at enabling the medusae to reposition rapidly and minimize the time spent swimming and not feeding. Another consequence of jet propulsion for medusae is that it constrains their maximum size. Consequently, the combination of prey capture mechanisms, small size and gut capacity of ambush medusae limits the trophic impact they have on prey standing stocks.

Oblate rowing jellyfish species who forage as cruising predators generally exhibit overlapping diets consisting of slow-moving soft-bodied prey. Rowing propulsion enables cruising medusae to efficiently entrain and feed on large volumes of water as they swim and, in addition, it eliminates the size constraints imposed by jet propulsion. Consequently, the larger sizes and high clearance rates of cruising medusae have enabled them to have large trophic impacts such that they have been repeatedly observed limiting prey standing stocks and structuring pelagic ecosystems.

For More Info, Please See Below Link:

http://fox.rwu.edu/jellies/index.htm