The jaws of Pterophyllum scalare

By Juan Fco. Fernández Roca
(Atreyu on The Angelfish Society Forum)

Publications:
FinTAStic Issue-30
http://www.theangelfishsociety.org/newsletters/2013_Sept_LowRes_v30.pdf (Baja resolución)
http://www.theangelfishsociety.org/newsletters/2013_Sept_HighRes_v30.pdf (Alta resolución)
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Summary: Analyzing the characteristics of Scalare pterophyllum jaws, teeth types, functions, pharyngeal jaws location.

Introduction: When we analyze the jaws of the fish and especially as your teeth are made, we provide a fairly accurate figure of feeding habits. Our Angelfish have also a second pair of jaws, cichlids show us their pharyngeal jaws.

The Mouth

The mouth of our fish is a “Terminal,” located on the front of the head and the size of the mouth is related to prey capture, typically small minnows and other varied live food.


Figura-1
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The Jaws

The jaws of the Angelfish are exceptional, formed by the premaxilla (top) and alveolar (bottom). They are equipped with tiny monocusp teeth, ending in a single point and are cuneiform. This gives us an idea that nature has set this mouth for a predatory diet. Despite having numerous small teeth, the primary function of the upper jaw is suction. The function of food shredding is reserved for the pharyngeal jaws.

The premaxilla, also called the upper jawbone, is composed of a pair and both bones are closely united by the maxilla symphysis.


Figura-2
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A left- right- pair forms the dentary lower jawbone and both are joined through the mandibular symphysis.


Figura-4
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A rather curious feature is its ability to project forward enlarging it and thereby allowing greater suction, this peculiarity of projecting the mouth is what we call “protractile” and is produced by a joint bone set in the middle the maxilla.


Figura-6
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A wide plate that is attached via connective fibers forms the dental base, known as the root of the teeth.

The teeth are conical shapes are composed of ortodentina or osteodentin. The pulp cavity is filled conjunctival cells, blood vessels and osteodentin. Enamel outer layer composed of vasodentina, vitrodentina, etc. The teeth do not last long; they deteriorate, fall out and are replaced by new ones.

So far we have presented the characteristics of the mouth and jaws, but there are other jaws cichlids possess.

The pharynx connects the mouth to the gastrointestinal tract and houses the “pharyngeal jaws.” These jaws are very important to Angelfish because they are live prey predators.


Figura-7
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These are almost undoubtedly the first obtained photos of these “pharyngeal jaws.” In the section “The dissection fresh,” we will see integrated into their respective bodies “ceratobranchial.”

Both jaws, both the lower and upper pairs are formed bone containing the teeth.

The photographs are for an Angelfish with a standard length of around 5 cm.

The teeth that make both jaws unlike the mouth are bicuspid, are numerous and cover the surface of the jaws, are more like those of a “cuneiform,” coinciding with our scalare predatory diet.


Figura-9
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Figura-11
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The pharyngeal jaw is attached to the two lower ceratobranchial, (see “fresh dissection”). Most bony fish have pharyngeal gill arches modified to process their prey (Liem 1986, Wainwright 1989), however our Angelfish Cichlidae family has new joints in the upper jaw throat, presenting a muscular sling and suture (junction point) in the past ceratobranchial.


Figura-12
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Figura-13

Discussion

Significant differences are established between the teeth of the jaws and pharyngeal jaws located on. Being monocusp type teeth in the jaws and bicuspid type in the pharyngeal jaws. The division of tasks is determined by the type of tooth.

Conclusions

Analyzed dietary habits under laboratory conditions, the teeth and jaws of the mouth are used especially to catch small prey, pharyngeal jaws being responsible for crushing the food and those doing the most important work in their food.

Acknowledgments

I would like to thank the Newsletter Committee for the great efforts in adaptations and translations from texts trying to bridge differences between English and Spanish and the deference shown.

References Graphics

Fig. 1 - Jaws Pterophyllum scalare.
Fig. 2 - Premaxila - 1.
Fig. 3 - Premaxila - 2.
Fig. 4 - Dentario - 1.
Fig. 5 - Dentario - 2.
Fig. 6 - Mouch protactile.
Fig. 7 - Approximate location of the pharyngeal jaws.
Fig. 8 - Pharyngeal Jaws.
Fig. 9 - Side view of the Pharyngeal Jaws.
Fig. 10 - Detail - 1. Pharyngeal Jaw top.
Fig. 11 - Detail - 2. Pharyngeal Jaw top.
Fig. 12 - Pharyngeal Jaw bottom Detail.
Fig. 13 - Lower pharyngeal jaw attached to the lower pair ceratobranchial latter.

References

Hulsey, C Darrin. Function of a key morphological innovation: fusion of the cichlid pharyngeal jaw Avila Botello, Mireya. 2008.

Organogénesis del sistema digestivo del pez Pterophyllum scalare (Perciformes: Cichlidae). Rev. Biol. Trop. (Int. J. Trop. Biol.) Vol. 56 (4). pags: 1857-1870. ISSN-0034-7744

De La Hoz U, Eduardo. 1994. Capacidades de modulación y plasticidad funcional de los mecanismos de captura de alimento en Atherinopsinae sudamericanos (Teleostei, Atherinidae). Invest. Mar., Valparaíso, 22 pags: 45-65.

Tibbets, lan R. 2004. Anatomy of the Pharingeal Jaw Apparatus of Zenarchopterus (Gill) (Teleostei: Beloniformes). Journal of Morphology 262. Pags: 750-759

Shadwick, Robert E. 2006. FISH BIOMECHANICS. Pags: 79-101. Elsevier Academic Press. ISBN-13: 978-0-12-350447-0