Polypterids fossil records,natural history,and anatomy

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FINS
The fins on fish serve many purposes on polypterids starting at the front.
The lobed pectoral fins are used for braking and manuvering,and casual swiming
The dorsal finlets are raised and lowered in threat assesment,defense and courtship,
The pelvic fins are used as stabilizers.
The anal fin serve a two fold purpose,one is stabilization the other during mating
The cadual fin and the rear of the body as their main propulsion when speed or power is required.

 

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LATERAL LINE
The lateral line system consists of bendable nerve endings in a series of mucous-filled canals Vibrations in the water or differential pressure in different parts of the canal cause the fluid to move and distort the nerve endings.
Because of it's name, we think of the lateral-line system as being oriented laterally on
the fish.Closer inspection shows a concentration of sensory receptors on the head
branching into 4 lines.The occipital,The supraorbital, The suborbital and The
hyomandibular.
The lateral line system enables detection of both vibrations in the water and changes in the pressure field set up as the fish swims. It provides information to the fish about movements of nearby organisms, very-low-frequency sound, differential current velocity, and back pressure built up as the fish approaches an obstacle.The lateral line sense is sufficiently directional to enable blinded fish to find and capture prey.
A swimming fish sets up a pressure wave in the water that is detectable by the lateral line systems of other fishes. It also sets up a bow wave in front of itself, the pressure of which is higher than that of the wave flow along its sides. These near-field differences are registered by its own lateral line system. As the fish approaches an object, such as a rock or the glass wall of an aquarium, the pressure waves around its body are distorted, and these changes are quickly detected by the lateral line system, enabling the fish to swerve or to take other suitable action. Because sound waves are waves of pressure, the lateral line system is also able to detect very low-frequency sounds of 100 Hz or less.

 

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SLIMECOAT
Is a mucous created by the continal replacement of glandular cells know in the fishes skin that produce a glycoprotein which is called mucin. This when mixed with water forms the mucus that makes up the slime coat of fish.Fish with poorly developed scales tend to produce more of this slime coat.. The slime coat does threee basci things- it reduces turbulence for the fish when swimming by smoothing over the areas between the fishes scales-it helps regulate the internal/external ionic balance and the efficiency of gases exchanged through the skins surface-ie-osmoregullation and it provides a slipery surface that in it's sloughing off prevents bacteria from attching themselves to the skin. Bacteria is simply washed away from the skin with this process. It also aids in acting as a wound bandage.Stressed fish have a change in their slime coat-either too much or too little.One sign of a stressed bichir is usually overproduction of its slimecoat.-Anne

 

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drawing of lower jaw Polypterid skull (journal of anatomy)

 

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Lower jaw skull in comparison to upper jaw Polypterid skull

 

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Skeleton

 

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Polypterid bite force
The mechanics of jaw closing are highly variable in
basal actinopterygians. The homologies of the adductor
mandibulae complex are detailed in Lauder (1980),
and their mechanical advantage for jaw closing force
ranges across an order of magnitude from Lepisosteus
osseus (0.05) to Polypterus senegalus (0.42). This
means that L. osseus transmits only 5% of adductor
muscle force at the jaw tip, whereas P. senegalus
transmits up to 42% of muscle force to the jaw tip for
biting. Conversely, L. osseus multiplies jaw muscle
speed by a factor of 20, and P. senegalus by a factor
of just 2.4, illustrating the trade-off between force and
speed in jaw lever systems.

 

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Diet composition of P.senegalus from PRU river,Ghana
Odonata nymphs-dragon fly
orthoptera larvae-locust
tricoptera-cadis fly
hemiptera-Hemiptera is an order of insects, comprising around 80000 species of cicadas, aphids, planthoppers, shield bugs and others
diptera larvae-The order Diptera includes all true flies.They live in aquatic (fresh water), semi-aquatic, or moist terrestrial environments.

 

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Sexual Dimorphism

Sexing Polypterids is the same for one species as it is for all.The anal fin on the male is approx.twice as wide
as the female it is also more muscular.This is the only truly dependable way it is done.
On the smaller species this can be seen at approx.7-8inches.On the larger species 10-12inches.

 

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BICHIR BREEDING
Breeding seasons in the wild
Of species I could find listed on fishbase.org

Polypterus senegalus senegalus
June and July -CHAD,-- basin
August, thru Oct. -Gambia,-- gambia river
Aug. thru Nov. -Senegal,-- lower senegal river
June thru Nov. -CHAD ,--no location given
May and June, --upper white nile river
there seems to be no mating from Dec. thru April in the wild or at least not reported or
recorded.
P.Bichir bichir March thru November in-CHAD
P.lapradeiJuly thru Sept in- GAMBIA
P.lapradei July thru Oct -- senegal river
P.delhezi - no reports
P.endlicheri--May thru Aug --cotre d'lvoire- Bandama river
P.endlicheri--Sept-Oct -Chad-Chad basin
P.endlicheri--July-Aug-Sudan --White nile river, Khartoum
P.endlicheri--July-Nov-Chad