1. LOCOMOTION Evolution of swimming
PELAGOS BIOLOGY
LOCOMOTION
Evolution of swimming
Swimming evolved a number of times in unrelated lineages.
Supposed jellyfish fossils occur in the Ediacaran, but the first free-swimming animals appear in the Early to Middle Cambrian.
These are mostly related to the arthropods, and include Anomalocaris, which swam by means of lateral lobes in a fashion reminiscent of today's cuttlefish.

2. PELAGOS BIOLOGY
LOCOMOTION
Among the radiata jellyfish, the main form of swimming is to flex their cup shaped bodies. All jellyfish are free-swimming.
Comb jellies use giant cilia (associated to form combs) to move. They move with the mouth onward, contrarily to medusae.

3. LOCOMOTION Ctenophores bears usually 8 comb rows, for swimming.
PELAGOS BIOLOGY
LOCOMOTION
Ctenophores bears usually 8 comb rows, for swimming.
The combs are oriented to run from near the mouth ("oral pole") to the opposite end ("aboral pole").
Each comb consists of thousands of unusually long cilia, up to 2 mm.
When trying to escape predators, one species can accelerate to six times its normal speed. 
Some species reverse direction as part of their escape behavior, by reversing the power stroke of the comb plate cilia.

4. PELAGOS BIOLOGY
LOCOMOTION

5. PELAGOS BIOLOGY
LOCOMOTION
the array of outer doublets does not twist when the beat direction reverses. This result provides strong support for the existence of a switching mechanism
the switching mechanism that signals the pattern of doublet sliding, does not involve rotation of the central pair

6. PELAGOS BIOLOGY
CILIARY LOCOMOTION

7. PELAGOS BIOLOGY
CILIARY LOCOMOTION

8. LOCOMOTION Jet propulsion
PELAGOS BIOLOGY
LOCOMOTION
Jet propulsion 
animals fill a muscular cavity and squirt out water to propel them in the opposite direction.
two designs for jet propulsion;
water from the rear and expulsion from the rear, such as jellyfish,
water from front and expulsion from the rear, such as salps.
Because of the expanse of the contracting cavity, the animal’s velocity fluctuates, accelerating while expelling water and decelerating while introduce it

9. PELAGOS BIOLOGY
LOCOMOTION
All Cephalopoda can move by jet propulsion, a very energy-consuming way to travel compared to the tail propulsion used by fish. The relative efficiency of jet propulsion decreases as animal size increases.
The stop-start motion
provided by the jets,
however, continues
to be useful for
providing bursts of
high speed - at least
when capturing prey
or avoiding
predators.
It makes cephalopods
the fastest marine
invertebrates.

10. PELAGOS BIOLOGY
LOCOMOTION
Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the funnel, created by a fold in the mantle.
Direction can be controlled somewhat by differently moving the funnel. Most cephalopods float (i.e. are neutrally buoyant), thanks to the chambered shell.
Squids swim more slowly than fish, but use more power to generate their speed. The loss in efficiency is due to the amount of water the squid can accelerate out of its mantle cavity.

11. PELAGOS BIOLOGY
LOCOMOTION
Salps move with mouth ahead, pumping water out of the back opening, after to have filtered it.

12. PELAGOS BIOLOGY
LOCOMOTION
In bilateria, there are many methods of swimming. The arrow worms (Chaetognatha) undulate their finned bodies, like fish. 

13. PELAGOS BIOLOGY
LOCOMOTION
Crustacea and Polychaeta usually swim by paddling with special swimming legs (pleopods, peraeiopods, or antennae in Crustacea; parapodia in Annelida).

14. PELAGOS BIOLOGY
LOCOMOTION
Swimming sea slugs (as the sea angels), flap fin-like structures.
The molluscs most evolved for swimming are the Cephalopoda.

15. LOCOMOTION Fish Swimming
PELAGOS BIOLOGY
LOCOMOTION
Fish Swimming
It is obtained by exerting force against the surrounding water by the contracting muscles on either side of the body in order to generate waves of flexion from nose to tail.
Most fishes generate thrust using lateral movements of their body & caudal fin. But there are also a huge number of species that move mainly using their median and paired fins.

16. LOCOMOTION PELAGOS BIOLOGY Body/caudal fin propulsion
Anguilliform locomotion
In long, slender fish, there is
little increase in the amplitude
of the FLEXION WAVE as it
passes along the body.
Sub-carangiform locomotion
a more marked increase in wave amplitude along the body with the vast majority of the work being done by the rear half of the fish.
Carangiform locomotion 
stiffer and faster-moving than the previous groups. The vast majority of movement is concentrated in the very rear of the body and tail.
Thunniform locomotion
high-speed long-distance swimmers. Here, virtually all the lateral movement is in the tail and the peduncle.
Ostraciiform locomotion
no appreciable body wave when they employ caudal locomotion. Only the fin itself oscillates (often very rapidly).

17. LOCOMOTION PELAGOS BIOLOGY Median/paired fin propulsion
Ocean sunfish, for example, and many small fish use their pectoral fins for swimming as well as for steering and dynamic lift.
Fish with electric organs, such as those in Gymnotiformes, swim by undulating their fins while keeping the body still, presumably so as not to disturb the electric field that they generate.

18. LOCOMOTION PELAGOS BIOLOGY Dynamic lift
Bone and muscle tissues of fish are denser than water. To maintain depth some fish increase buoyancy by means of a gas bladder or by storing oils or lipids. Fish without these features use dynamic lift instead. It is done using their pectoral fins in a manner similar to the use of wings by airplanes and birds.
Sharks depend on dynamic lift; notice their well-developed pectoral fins.
these fish must stay moving to stay afloat and that they are incapable of swimming backwards or hovering.

19. LOCOMOTION PELAGOS BIOLOGY Median-paired fin
Combination of two pectoral fins or both
or anal and dorsal fins.
Different uses of Median Paired
Fin (MPF) can include:
UNDULATORY
Rajiform: thrust is produced by
vertical undulations along large pectoral fins.
Amiiform: undulations of a long dorsal fin while the body axis is held straight and stable
Gymnotiform: undulations of a long anal fin (upside down amiiform)
Balistiform: both anal and dorsal fins undulate.
OSCILLATORY
Tetradontiform: dorsal and anal fins are flapped as a unit, either in phase or opposing one another. The ocean sunfish is an example.
Labriform: oscillatory movements of pectoral fins can be classified as drag based or lift based in which propulsion is generated either as a reaction to drag produced by dragging the fins through the water in a rowing motion or via lift mechanisms.

20. LOCOMOTION PELAGOS BIOLOGY Flying Family Exocoetidae.
these species glide directly over the surface of the water without ever flapping their "wings." Flying fish have evolved abnormally large pectoral fins that act as airfoils and provide lift when the fish launches itself out of the water.
Additional forward thrust and steering forces are created by dipping the hypocaudal lobe into the water and vibrating it very quickly,
Of the 64 extant species of flying fish, only two distinct body plans exist, each of which optimizes two different behaviors.

21. LOCOMOTION PELAGOS BIOLOGY Monoplane body plan
In the Exocoetus or monoplane body plan, only the pectoral fins are enlarged to provide lift. Fish with this body plan tend to have a more streamlined body, longer, narrow wings, and higher wing loading, making these fish well adapted for higher flying speeds.
Flying fish with a monoplane body plan launch from the water at high speeds at a large angle of attack (sometimes up to 45 degrees). In this way, monoplane fish are taking advantage of their adaptation for high flight speed, while fish with biplane designs exploit their lift production abilities during takeoff.

22. Tradeoffs
Tail Structure: flying fish have an enlarged ventral (hypocaudal) lobe which facilitates dipping only a portion of the tail back onto the water for additional thrust production and steering.
Larger mass: Because flying fish are primarily aquatic animals, they are heavier than other habitual fliers, resulting in higher wing loading and lift to drag ratios for flying fish compared to a comparably sized bird. 
Biplane body plan
In the Cypselurus, both the pectoral and
pelvic fins are enlarged. They also tend
to have "flatter" bodies which increase
the total lift.
As a result, they are well dapted for
maximizing flight distance and duration.
Cypselurus have broader wings than
Exocoetus. In flying fish with the biplane
design the hypocaudal lobe remains in the water to generate thrust even after the trunk clears the water's surface and the wings are opened with a small angle of attack for lift generation.

23. LOCOMOTION PELAGOS BIOLOGY Adaptation
a balance of stability and maneuverability.
Swimming relies on more caudal body structures that can direct powerful thrust only rearwards. Body-Caudal Fin swimming is, therefore, stable and useful for large migration patterns to maximize efficiency over long distances/periods. Propulsive forces in Median-Paired Fin swimming is generated by multiple fins located on either side of the body that can be coordinated to execute elaborate turns. As a result, MPF swimming is well adapted for high maneuverability and is useful in elaborate escape patterns.
fish do not rely exclusively on one locomotion mode, but are rather locomotion "generalists,“ choosing among many available behavioral techniques.

24. PELAGOS BIOLOGY
LOCOMOTION
Tetrapods re-evolved the ability to swim or have indeed returned to a completely aquatic lifestyle.
Primarily or exclusively aquatic animals have re-evolved from terrestrial tetrapods multiple times: example. include reptiles (also extinct), marine mammals, and marine birds.
dogs swim recreationally. Umbra,
a world record-holding dog, can
swim 4 miles (6.4 km) in 73 min,
placing her in the top 25% of
human long-distance
swimming competittors.  

25. PELAGOS BIOLOGY
LOCOMOTION
The fishing cat is one wild species of cat that has evolved special adaptations for an aquatic or semi-aquatic lifestyle. Tigers and some individual jaguars are the only big cats known to go into water

26. PELAGOS BIOLOGY
LOCOMOTION
Birds can either be aquatic or simply capture fish underwater.
In both cases they swim flying (they use the wings = anterior legs)

27. LOCOMOTION Some reptiles can swim flying, too As some mammalians do
PELAGOS BIOLOGY
LOCOMOTION
Some reptiles can swim flying, too
As some mammalians do

28. LOCOMOTION Some birds can use posterior legs to swim
PELAGOS BIOLOGY
LOCOMOTION
Some birds can use posterior legs to swim
As some mammalians do

29. PELAGOS BIOLOGY
LOCOMOTION
Cetaceans evolved a caudal fin, oriented perpendicularly to that of fish, and loose the posterior legs (mutica)

30. PELAGOS BIOLOGY
LOCOMOTION
In any cases, reptiles, birds, and mammalians living into the sea, they have to resolve the problem of how to breath air.