Spleen is one of the important lymphoid organs with wide variations of morphological and physiological functions according to species. Morphology and function of the spleen in bats, which are hosts to several viral strains without exhibiting clinical symptoms, remain to be fully elucidated. This study aims to examine the spleen morphology of fruit bats associated with their physiological functions. Spleen histological observations were performed in three fruit bats species: Cynopterus titthaecheilus (n = 9), Rousettus leschenaultii (n = 3) and Pteropus vampyrus (n = 3). The spleens of these fruit bats were surrounded by a thin capsule. Red pulp consisted of splenic cord and wide vascular space filled with blood. Ellipsoids in all three studied species were found numerously and adjacent to one another forming macrophages aggregates. White pulp consisted of periarteriolar lymphoid sheaths (PALS), lymphoid follicles and marginal zone. The lymphoid follicle contained a germinal centre and a tingible body macrophage that might reflect an active immune system. The marginal zone was prominent and well developed. This study reports some differences in spleen structure of fruit bats compared to other bat species previously reported and discusses possible physiological implications of the spleen based on its morphology. K E Y W O R D S flying foxes, histology, immunology, morphology, physiology, viral reservoir

This study was conducted to investigate the histological characteristic, type, and distribution of connective tissue in Sunda porcupine skin. The investigation was carried out in three adult of sunda porcupines at microscopic level using hematoxylin eosin, Masson thrichrome, Verhoeffs van Gieson, alcian blue pH 2.5 and periodic acid Schiff staining methods. Skin consists of epidermis, dermis hypodermis, and subcutaneous muscle. Quill follicles were the main and dominant structure as well as the specific characteristic on Sunda porcupine skin. The connective tissue was distributed well in basal membrane, dermis, quill follicle, and hypodermis with various intensity and density. The collagen was the main fiber found in the skin while the elastin fiber was not observed. The acid carbohydrate was found distributed well in the skin while the neutral carbohydrate was not detected in this study. In addition the fibers of connective tissue associated with the adipose tissue which found plentifully in quill follicles and hypodermis. The present results showed that the wide distribution of connective tissue might have an important role on the wound healing physiology of Sunda porcupine skin.

Fruit bats have been reported as the natural reservoir of many emerging and re-emerging zoonotic diseases. Infected bats usually do not show any clinical symptoms and are infected persistently. This unique characters indicate that bats have high immune activity to combat viruses even in its physiological state. High immune activity will affect the size of lymphoid organ and produce high level of reactive oxygen species (ROS). Spleen is one of the important lymphoid organ which have a strategic function in elimination of blood borne pathogens. This study was undertaken to provide information on the normal size of spleen and to analyze malonaldehyde (MDA) and super oxide dismutase (SOD) levels of free range fruit bats (Cynopterus brachyotis). The ratio of body weight/spleen was 0.4% and there were no significance differences between the male and female bats. The spleen MDA levels which represent ROS generation was higher than those of the liver. Male bats with higher levels of MDA tend to have bigger spleen size than the female which has lower MDA levels. High levels of MDA might indicate a high immune activity inside the spleen. Despite the negative effect of ROS to genetic material, high level of ROS can be advantageous to support the bats immune system as a viral reservoir. High levels of MDA are generally accompanied by high levels of SOD which might reduce the negative impact of oxidative stress in the C. brachyotis.

Haematological profile is important to determine the physiological condition of an individual, and morphology of red blood cells can also be helpful in making a diagnosis of a disease. The size of red blood cells affects the ability of red blood cells to carry oxygen. In some clinical events shape and size of red blood cells will be changed. Bats are the only mammals that have the ability to fly. The ability of bats to fly would require bats to be able to bind more oxygen, therefor bat should have enough of energy while flying. The present study was conducted on 12 Cynopterus tithaecheilus (7 males and 5 females) to study about haematological profile. Blood samples were taken using tuberculin needle and analyzed by hematology analyzer for hematological value. Size of red blood cells was taken using bloods smear and analyzed by imageJ software. Cynopterus tithaecheilus show the higher number of red blood cells, but the size were smaller compared to the other mammals which has same body size. Mean while the concentration of hemoglobin and hematocrit were higher. The present result suggested that these haematological values might provide a greater transport oxygen capacity in the Cynopterus tithaecheilus.

The distribution and composition of extracellular matrix (ECM) of the spleen in two species of fruit bats, namely Cynopterus titthaecheilus and Rousettus leschenaultii, were examined by histochemistry and immunohistochemistry. Reticular fibres accompanied by laminin were identified to make up the splenic stromal network. Types I and III collagen were identified in various spleen compartments with varying intensities. Thin and short elastin fibres were scattered in several parts of the spleen. Visualization of the ECM of the spleen can better demonstrate spleen compartmentalization. The alleged vascular space structure in the fruit bats spleen was the sinus structure that was strengthened by the presence of reticular fibres that limit the sinus basement membrane. The present study identified periellipsoidal lymphoid sheath (PELS)‐like structure in fruit bats spleen that had never been identified in mammals before. In addition to describing the structure, this study highlighted the variations in ECM composition of the spleen between species that can provide new insight into the phylogenetic study of spleen morphology.