الفهرس 
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Abstract
-The Skull of the Blind Snake, Rhamphotyphlops braminus
In the present study of the skull of Rhamphotyphlops braminus, the median dorsal bones (nasals, frontals and parietals), the palate (premaxillae, maxillae, septomaxillae, prevomers, palatines, pterygoids, ectopterygoids, basisphenoid and parasphenoid), circumorbital series (prefrontals, frontals and maxillae), otic capsule (prootics and laterosphenoids), bones of the upper jaw (premaxillae, maxillae and quadrates), bones of the lower jaw (dentary, splenial, angular, coronoid and the mixed bone) and the occipital ring (basioccipital, supraoccipital and exoccipital) were described.
1.1-Nasal
Nasal bones are paired and expanded to adapt for the burrowing mode of life. Each nasal bone sends a descending plate which unites with its fellow to form an interorbital septum. In a ventral view the two nasals are difficult to be seen, since they are completely covered by the two fused premaxillae. The nasals are quite apart from the two maxillae. The two nasal bones meet together along the mid-dorsal line, where they are separated from each other and from the anterior border of the cranial roof by well recognized sutures. The antero-lateral borders of the two nasals share with the premaxillae in the construction of the burrowing apparatus.
1.2-Frontal
The frontals appear as two separate enlarged bones. Each frontal bone contacts with the nasal bone anteriorly and with the parietal posteriorly. Each frontal sends postero-ventrally a lateral downgrowth which directs ventrally toward the parasphenoid
separating the orbits and forming the side walls of the anterior part of the skull.
1.3-Parietal
The parietal bones are paired and are considered to be the largest bone in the skull. Each parietal bone is bordered by the frontal anteriorly, supraoccipital-exoccipital bone posteriorly and prootic postero-laterally. Ventrally, the parietal bones send a lateral downgrowth on each side so the frontal as well as the parietal downgrowths form together a complete cranial box surrounding the mid-brain.
1.4- Premaxilla
The premaxilla appears as single enlarged bone. The great enlargement of the fused premaxillae reflects its burrowing mode of life. It curves ventrally to reach the septomaxillae and prevomers. The premaxilla is edentulous and is entirely separated from the maxilla. It sends a tapered vomerine process
which extends in between the anterior third of the two prevomers.
1.5- Maxilla
The maxillae are short, separate and movable bones that share in the formation of nasal region. Each maxillary bone lies quite apart from the premaxilla, prefrontal and frontal bones. The maxillae have a triangular shape, devoid of any processes and bear five distinct teeth.
1.6- Septomaxilla
The septomaxillae are paired large bones which construct the ventral side of the rostrum. They are surrounded anteriorly
by the fused premaxillae, laterally by the prefrontals, medially by the prevomers and posteriorly by the palatines. The two septomaxillae completely hide the two nasals ventrally. The
septomaxillae as well as the prevomers share in the formation of the bony nasal capsule surrounding Jacobson’s organ. Jacobson’s organ is situated at the ventro-lateral side of the nasal cavity and is surrounded by a cartilago-osseous capsule. Jacobson’s organ appears as dome-shaped structure in cross sections with c-shaped lumen which become narrower posteriorly and finally become circular. The shape of Jacobson’s organ varies at its length and sometimes become pear-shape or triangular in some parts and oval at its end.
1.7- Prevomer
The prevomers appear in the form of two completely separate bones in the ventral surface of the skull. Each prevomer consists of anterior and posterior broad triangular portions. On both sides, the two prevomers are surrounded by the septomaxillae anteriorly and the lateral downgrowths of the two frontals posteriorly. The posterior process of the fused premaxillae is wedged between the anterior ends of the two prevomers. The prevomer bone is perforated by the fenestra vomero-nasalis externa for the passage of the duct of Jacobson’s organ. The vomerine portion of the palate of the present snake is greatly extensive where burrowing modifications are always needed.
1.8- Palatine
In ventral view, the palatines are formed from two straight bars that overlap each other medially. They extend in front of the frontal downgrowths posteriorly, but quite apart from the septomaxilla and prefrontal anteriorly. The palatines lack any processes and the palatine teeth are completely absent.
1.9-Pterygoid
In the present snake, the pterygoids appear as cylindrical elongated bone. The anterior tip of the pterygoid is bifurcated
and articulated with the posterior border of the palatine, while its posterior extremity stops slightly after the posterior limit of the basioccipital. The pterygoids lie ventrally and quite apart from the quadrate. The pterygoid teeth are entirely absent. The ectopterygoids and epipterygoids are lacking.
1.10- Parasphenoid and Basisphenoid
The basisphenoid bone constitutes the greatest and chief part of the cranial floor. The anterior part of the basisphenoid is continous completely with the parasphenoid without any distinct suture. The anterior tip of the parasphenoid extends to reach the postero-ventral ends of the lateral downgrowths of the frontals. The posterior broad end of the basisphenoid articulates with the basioccipital while its lateral side articulates with the parietal downgrowth. The basisphenoid articulates the prootics postero-laterally.
1.11- Prefrontal
The prefrontals appear as curved expanded bones with an outer convex surface and inner concave one in the dorsal view of the skull. The anterior end of the prefrontal is separated from the fused premaxillae by a wide nostril, while its posterior extremity reaches the anterior tip of the frontal bone. In a lateral view of the skull, the prefrontals appear as vertical bone which curve ventrally, and lie ventral to the nasal and the frontal bones.
1.12-Prootic
The paired prootics are large convex bones covering the otic region and meeting the three occipital bones to the rear and the parietal and basisphenoid in front. In lateral view, the prootic bone shows well defined perforation with two foraminae, an anterior one for the departure of the maxillary branch of the trigeminal nerve and posterior one for the exit of the mandibular
branch of the same nerve. The opisthotic bone is completely absent.
1.13- Laterosphenoid
The laterosphenoid bone takes the position between the two foraminae of the maxillary and mandibular branches of the trigeminal nerve of the prootic. The laterosphenoid bone is completely fused with the lateral side of the prootic.
1.14- Quadrate
In lateral view, the quadrate appears as an elongated, slender and flattened bone. It is directly connected with the cranium via ligaments and muscles so the temporal bones are totally missed. The anterior end of the quadrate is provided with anterior and antero-dorsal process, the former process appears to articulate with an excavation in the posterior part of the mixed bone of the mandible. The posterior extremity of the quadrate is connected firmly with a calcified cartilage.
1.15- Dentary
The dentary is represented by relatively short triangular bones. The two dentaries are joined together anteriorly. In the present snake, the dentary is edentulous.
1.16- Splenial
The splenial is a triangular bone and is greatly hidden behind the dentary. The broad surface of the splenial faces the angular bone and extends just beneath the anterior-most portion of the mixed bone. In the present snake, the splenial bone is extremely reduced.
1.17- Angular
The angular is an elongated triangular bone which lies ventro-lateral to the anterior portion of the mixed bone. The angular is provided with an anterior broad surface which reaches the posterior end of the splenial, while the posterior portion of
the angular ends freely. It is long as the splenial is so much reduced.
1.18- Coronoid
The coronoid bone is triangular in shape. It has a broad base resting on the anterior part of the dorsal surface of the mixed bone and is provided with a sharp coronoid process which directs dorsally. In the present snake, the coronoid bone lies posterior to the dentary and quite apart from the splenial as well as the angular.
1.19- Mixed Bone
The mixed bone represents a fused prearticular, articular and supra-angular. In the present snake, the mixed bone appears as an elongated cylindrical rod. It has an anterior broad end and posterior tapered extremity. Anteriorly, the mixed bone articulates loosely with the dentary, while posteriorly it is firmly attached to the quadrate bone.
1.20- Supraoccipital
The supraoccipitals are paired rectangular bones which fuse with the two exoccipitals forming a single supra- exoccipital bone.
1.21- Basioccipital
The basioccipital is flat roughly triangular, with its apex directed posteriorly. The anterior edge (the base of the triangle) is straight or slightly concave to meet the end of the basisphenoid. Laterally, the basioccipital bone is bordered by the lower edges of the exoccipitals and prootics. The posterior end of the basioccipital articulates with the hypocentrum of the atlas, fitting against a calcified cartilage facet of the latter. In the examined species, the basioccipital bones share in the formation of the ventral boundary of the foramen magnum and the two exoccipitals meet each other behind the basioccipital.
1.22- Exoccipital
In the present snake, the exoccipital is fused with the supraoccipital. The major part of each exoccipital forms the lateral wall of foramen magnum and the occipital region of the skull.
2-The Alimentary Tract of the Blind Snake, Rhamphotyphlops braminus
2.1- Scanning Electron Microscopy
The alimentary tract of the typhlopid snake, Ramphotyphlops braminus was anatomically, histologically and histochemically investigated. The gut is differentiated anatomically into the basic ophidian pattern. The present study proved that constrictions were absent between the different parts of the alimentary tract (oesophagus-stomach, stomach-small intestine and small intestine-large intestine). The large intestine lacks caecum.
The Scanning E.M. examination revealed that the mucosal surface of the oesophagus is thrown into numerous prominent longitudinal folds leaving long furrows in between. These folds showed irregular patterns. The gastric mucosa forms large number of short longitudinal folds. Small furrows were detected in between. The luminal surface of the columnar cells appeared pentagonal. Simple tubular gastric glands open into the gastric pits. The luminal surface of the small intestine appeared as irregular wavy mucosal folds in the fashion of Zig-Zag pattern. The mucosal folds of the small intestine contained short and blunt projections representing the villi. Pentagonal absorptive columnar cells and goblet cells were detected in between these columnar epithelial cells. The internal surface of the large intestine is provided with many irregular wavy folds which
anastomose with each other to form complex reticulated pattern leaving shallow cup-shaped depressions. The mucosal surface of the large intestine consisted of simple columnar cells which have pentagonal shape. Many goblet cells were detected between these columnar cells.
2.2- Alimentary Tract Histology
The wall of the oesophagus, stomach, small and large intestine is built up from the peripheral inwards of serosa, muscularis, submucosa and mucosa. The muscularis of oesophagus is very thin and is consisted of smooth unstraited muscle fiber, while this layer in case of stomach is composed of thick and well developed layer of smooth muscle fibers mainly of longitudinal type. In the small intestine, the muscularis has an
outer thin layer of smooth circular muscle fibers (more continous) and inner thicker one of smooth longitudinal muscle fibers (less continous). The muscularis of the large intestine is formed of an outer thin longitudinal muscle layer (less continous) and inner slightly thicker circular muscle layer (more continous).
The oesophageal mucosa is consisted of simple columnar epithelium. The oesophageal glands were completely absent. The gastric mucosa is consisted of simple columnar epithelial cells. The mucosa of small intestine is composed of two types of cells including absorptive and goblet cells. The mucosal epithelium of the large intestine is represented by simple columnar epithelial cells and scattered goblet cells. Mucosa of both small and large intestine lacks intestinal glands as well as crypts of lieberkhün.
2.3- Alimentary Tract Histochemistry
The PAS-Positive materials, mucopolysaccharides (acid and neutral), and total proteins were histochemically investigated in the different regions of the alimentary tract. PAS-Positive
materials are evident in the mucosa of oesophagus, gastric glands of stomach and goblet cells of small and large intestine and are responsible for energy production required for the peristaltic movement. High content of both acidic and neutral mucins is displayed in the mucosal epithelium of oesophagus (allowing an easier passage of the prey) and stomach (passage of the digested food to small intestine), gastric glands and goblet cells of small and large intestine. The positive response of the goblet cells of large intestine mucosal epithelium to PAS-Alcian blue stain is considered an adaptive character to perform its function of water absorption and defecation. High protein content was detected in the muscularis and mucosa of oesophagus, stomach, small and large intestine.
In conclusion, the skull shape affects feeding strategy in the present snake, Rhamphotyphlops braminus. The prey is ingested and transported via a rapid maxillary raking mechanism. The lower jaws of R. braminus are toothless and relatively rigid whereas the upper jaw arches bear teeth and highly mobile. The mandible is much longer and is suspended from the braincase via relatively short quadrate. The dentary is greatly reduced and lacks teeth (a condition which is unique for typhlopid snakes). There is an extensive contact between the relatively long angular and the large triangular coronoid. Thus the intramandibular joint is bridged completely by the angular and consequently, the lower jaws are relatively rigid and akinetic. The upper jaws of R. braminus are kinetic. The maxillae lie horizontally against the roof of the mouth with their transversely oriented tooth rows directed posteriorly. The maxillae are suspended from the braincase largely by ligaments and muscles rather than through bony articulation.