Fish - Chart text
CR modes in FISHES:
Both the Alternating and Parallel modes are employed by fishes. Alternate pectoral fin action serve in balancing the undulatory thrust of the body and tail. Parallel mode actions generate thrust, lift or braking. A special parallel a
ction is found in Flyingfishes.
Explanation: Taking body-tail undulation to stand for hind limb activity needs an explanation at this point. In alternate leg movement the ancestral body undulation is still present to various degrees, and so is continuously extant through the evolu
tion of the vertebrate classes.
The Mixed mode, as well, occurs in parallel pectoral fin and alternating body-tail interaction. (Flying fishes again)
Evolution from purely undulatory method to later pectoral fin propulsion can be described as tendency for undulation to be gradually posteriorly confined to the tail, and at the same time, for pectoral fin action to take up the locomotory role anteriorly.
Undulation is one of the few fundamental methods of locomotion in animals. And it is present almost universally all vertebrates.(even in Cf. sperm cell, or in different phyla: Portg Man of War tentacles? Euglena).
This function is universal in fish and it is still found the Amphibian Caudata orders (salamanders), Anura (tadpoles), and Caecilians.
But in fish evolution developed and perfected another form of transportation, namely lift- and drag-based propulsion, which involves fin motions.
Elasmobranch fins are relatively immobile and assist in control, the pectorals act as hydroplanes. (Cambered cross section, like bird or airplane wing.)
But among Actinipterygii the development of propulsion led two different ways:
first, it led to terrestriality through the line of the lungfish, with strong limbs to crawl on land or mud and vegetation.
Second, the relatively thin, "laminar" highly plastic pectoral fin among the
Teleostei?? (advanced fishes) came to control movement generated by undulation and even to propel by paddling in complex patterns, or to
In the Elasmobranch rays and skates, the enormous pectoral fins however, undulate, acting as both hydroplanes and propulsors.
CR modes in Fishes
1. Formerly it was thought that pectoral fins only played a role in steering and maneuvering.
2. But it is often apparent through viewing visual data or fish in aquaria that certain fish move themselves with pectoral fin strokes. However, it has also been formally stated that a propulsive mechanism is are work in the pectoral fin behavior in many fi
shes. (Gibb, et al.)
Both lift and drag-based propulsion: ...
3. Also it was noted that "many reef fishes use pectoral swimming to achieve very fine motion control such as backward motion, by keeping their bodies still and using their pectoral fins like oars. (www.dgp.toronto...)
Mudskipper: both alternating and parallel pectoral fin locomotion is present. (see video).
Flying fish (Exocoetidae): Both pectoral and pelvic fins function in parallel mode in genus Cypselurus in gliding.
Drag versus Lift-based propulsion: explain!!
Studies have classified fish propulsion into two groups. IN one the body and caudal fin, in different relative proportions, generate thrust, while in the other this is done by the median and/or the pectoral fins.
Body-caudal fin propulsion
The body-caudal fin range varies from the eels (Anguilliform), where the body is the major agent, through the ... ( Subscarangiform) and the ... (Carangiform), where decreasing proportions of the body are involved, to the energetic tuna (Thunniform), where
only the tail and its short narrow peduncle connecting it to the body, moves.
In the Ostraciiform propulsion the tail does not undulate, but oscillates.
Median/paired fin propulsion:
In this group, the pectoral and median fins cooperate in varying proportions.
The two median fins are single fins, one being the dorsal, and the other the anal.
IN the Rajiform propulsion (rays and skates) the especially enlarged pectoral fins undulate in the horizontal plane.
In the bowfin (Amniiform), electric fishes (Gymnotiform), triggerfishes (Balistiform), and Ocean Sunfish (Tetraodontiform) propulsions various combinations and proportions of the dorsal and anal fins produce thrust.
In the puffersfishes (Diodontiform) mode the pectoral fins perform undulation.
In the wrasses (Labriform) behavior the pectoral fins oscillate, that is go through cyclic motion patterns. This applies widely to the entire order Perciformes (perches and allies).
The role of the caudal fins in Labriform behavior has not been examined. This may be interesting since in the advanced perches and allies the caudal fins, lying on the ventral side, are actually in line or even anterior to the pectoral fins, where they must
necessarily in some way be closely coactive with the pectorals.