Comparative craniometric study of fat sand rat [Psammomys obesus] and four toed jerboa [Allactaga tetradactyla] live in the similar habitats

The present study deals with the skull structure in two species of rodents, namely Psammomys obesus, the common name is Fat Sand rat, and Allactaga tetradactyla, the common name is four toed jerboa that lives in the same habitat. The skulls of Psammomys obesus and Allactaga tetradactyla are studied. The skull of Psammomys obesus, is triangular, strongly ridged and the sutures between its components are fairly apparent. It has two large parietals which are quadrate in shape. The frontal bone have triangular shape. The squamosal bone is triangular in shape. The zygomatic arch is slender and weak. The tympanic bullae are greatly expanded and the external auditory meatus is swollen. It has irregular shaped sphenoid bone consists of two unfused parts, presphenoid and basisphenoid. The occipital bone encloses the foramen magnum which is guarded laterally by two smooth articular occipital condyles. Exoccipital is broad. The mandible of Psammomys obesus consists of right and left halves firmly united in life at the mandibular symphysis. The body of the mandible can be divided into two parts, one bears the incisor teeth and the other contains the molar teeth. However, the cranium in Allactaga tetradactyla is broadly flattened in shape and the sutures between its component bones are apparent. It has two large parietals and the interparietal is narrow and triangular in shape. The frontal bones are flattened. On each side of the cranium, the squamosal which lies between the tympanic bullae and orbit. Supraoccipital is large, the zygomatic arch is slender, weak and consists of two parts, the zygomatic process of maxilla and zygomatic process of temporal. The nasal bones are elongated. The maxillary bone is irregular in shape. The tympanic bulla, exoccipital and paraoccipital process are short

Anatomical, histological and histochemical studies on some organs of true desert rodents in the Egyptian habitats

The present study aimed to compare between the anatomy, histology and histochemistry of two species belonging to two different families namely Muridae and Dipodidae. Muridae is the largest family of rodents in the world; it is represented in this work by fat sand rat Psammomys obesus. Four-toed jerboa Allactaga tetradactyla represents the other family, Dipodidae. Psammomys obesus lives in coastal presaharan region; the preferred habitat is saline marshes ,and wadis where halophytic plants were abundant. However, Allactaga tetradactyla, inhabites the salt marshes and clay desert areas of coastal plains. The investigated animals were collected from desert, weighed and transferred alive to the laboratory in separate cages then anaesthetized with ether, after which they were carefully dissected, organs are taken out and prepared for the histological and histochemical studies. The nucleocytoplasmic index of liver cells was calculated, kidney weighed and the relative thickness of cortex,, outer and inner medulla was measured and total glomerular number was recorded. The liver, as in mammalian species, is consists of five separate lobes. The mitotic index of Psammomys obesus is smaller than that found in Allactaga tetradactyla. This may he due to the increased activity of'Allactaga tetradactyla. In the kidney, the cortex is classified into three regions namely superficial, midcortical and juxtamedullary zones. Both number and diameter of glomeruli, glomerular volume and relative glomerular blood volume is greater in Psammomys obesus than that in Allactaga tetradactyla. These observations indicate the ability of Psammomys obesus to produce highly concentrated urine than that of'Allactaga tetradactyla