1. to determine whether difference in birth body mass influenced growth performance in pipistrellus kuhlii we studied a total of 12 captive-born neonates. bats were assigned to two body mass groups: light birth body mass (lbw: 0.89 ± 0.05, n=8) and heavy birth body mass (hbw: 1.35 ± 0.08, n=4). heavier body mass at birth was associated with rapid postnatal growth (body mass and forearm length) faster epiphyseal gap closure and higher survival rate. during first 3 weeks body mass increased by 0.11 ± 0.18 g/day in hbw and rate of forearm length was 0.67 ± 1.13 mm/day. corresponding values for lbw were 0.10 ± 0.11 g/day and 0.62 ± 0.69 mm/day respectively. the initial rapid growth in hbw gradually decreased to merge single asymptomatic maxima at about 60 days after birth. the hbw class attained maximum epiphyseal phalangeal gap of 4.9 mm on day 19 and closed the gap faster (-0.07 mm/day) than the lbw class with a maximum epiphyseal gap of 4.78mm on day 23 and closure rate of - 0.06 mm/d. pup mortality was nil in hbw while four lbw males died at age 4-6 weeks. 2. postnatal growth of body mass, forearm, epiphyseal phalangeal gap and changes in wing morphology including wingspan, wing area, handwing length, handwing area, armwing length, armwing area, aspect ratio and wing loading were studied in 12 kuhl’s pipistrelles, p.kuhlii, which were born and reared in a flight cage. the pups at birth had a mean (± se) of 1.04 ±0.08g of body mass and forearm length of 11.48 ±0.45mm. at 60 days mean body mass had reached 87.56% of adult postpartum mass and mean forearm length of was 89.46% of adult length. the rate of body mass gain and forearm growth during the first 23 days was 0.10± 0.10 g/days and 0.64± 0.61 mm/day respectively. the wingspan and wing area increased linearly until 33 days of age by which time the young bats exhibited clumsy flight with gentle turns. analysis of changes occurring on wing morphology indicates that seven wing characteristics perform a rapid growth rate at “pre-flight” and second slower growth rate at “post-flight” periods. wingspan, handwing, length and area, armwing length and area, and total wing area increased linearly until the age of first flight, after which the growth rates decreased significantly (all p<0. 000). wing loading decreased linearly (-0. 80 nm-2/days) until 41 days of age and thereafter increased to a maximum of 25 nm_2 at 88 days of age. the aspect ratio showed a high degree of scatter at early stages of life which decreased at the later period of growth. additionally, linear regression equations, confidence intervals and prediction intervals used for age estimation based on data available for the forearm, body mass, the total gap of the 4th metacarpal-phalangeal joint, armwing length, handwing length and wingspan. 3. this study documents the postnatal growth of body mass, forearm and the epiphyseal phalangeal gap in a free ranging population of the long fingered bat miniopterus schreibersii in a maternity roost in mahidasht cave in western iran. the pups at birth had a mean birth body mass of 3.74g±0.09 and forearm length of 24.32 mm±0.31. the length of forearm and body mass increased linearly during first 2 weeks, and thereafter maintained an apparent stability. the epiphyseal gap of the fourth metacarpal phalangeal joint increased until 13 days, then decreased linearly until 70 days and thereafter fused. the rate of body mass gain and forearm growth during the first 13 days was 0.54 g/d and 1.39 mm/d respectively. initiation of flight occurred 3 weeks after birth. a method of estimation of age was derived from values of length of forearm and the total gap of the fourth metacarpal-phalangeal joint during the preflight and post flight periods. 4. anatomical, histological and histochemical examinations were made from pharynx, esophagus, stomach, duodenum and large intestine in neurergus microspilotus and neurergus kaiseri. sections were stained with (h&e), (pas) and (ab). in both species the pharynx and esophagus are covered by psudostratified ciliated columnar epithelium with goblet cell which is positive with pas and ab. the stomach in n. kaiseri and n. microspilotus is a straight, expanded conical tube, laying slightly to the left side of the body cavity, and terminating at the pylorus. the stomach in both species is divided into three distinct parts, the cardia, fundus and pylorus. although in both species the epithelium of the stomach surface and of the lining of the crypts consists of a single layer of high columnar cell, but the apical portion of the cells in n.kaiseri consists of homogeneous acidophilic granules while in n.microspilotus is foamy. the duodenum is short and is sharply reflexed along the medial aspect of the stomach. duodenum in n. kaiseri and n. microspilotus shows villi which consists of the epithelial covering and a core of connective tissue containing blood and lymph capillaries. the large intestine in both n. kaiseri and n. microspilotus is located along the median line. the intestine is a coiled tube of a regular diameter, larger than, that of the duodenum. histologically, these are no villi in large intestine and goblet cells rise to numerous. the epithelium is simple columnar, and the lamina propria and submocosa are strongly reduced. in n. kaiseri and n. microspilotus the major digestive glands are the very large liver and the small pancreas. the liver in n. kaiseri and n. microspilotus has two distinct lobes, right and left. histologically, the parenchyma of liver in n. kaiseri and n. microspilotus is contained within a thin capsule of fibroconnective tissue. sinusoids are lined with endothelial cells forming a very thin cytoplasmic sheet. bile ducts also occur within the parenchyma of the liver. the ducts are lined by simple cuboidal epithelium. the gall bladder is a storage depot for bile. its mucosa thrown into numerous folds. the pancreas in n.kaiseri and n.microspilotus is roughly triangular in shape, and lies rather to the dorsal side of the duodenum, between it and the stomach. the exocrine pancreas consists of clusters of pyramidal cells mostly organized in acini. the cells have a dark basophilic cytoplasm, distinct basal nuclei, and many large eosinophilic zymogen granules containing enzymes responsible for the digestion of proteins, carbohydrates, fats and nucleotides. 5. anatomy and histology of the female genital system of two closely mountain newts are studied. in both species a thin layer of tunica alboginae covers the ovary. according to morphological characteristic the ovarian cycle in these two species can be divided into three main phases and five stages. the previtellogenic, vitellogenic and mature oocytes phase. during previtellogenic phase, the oocytes show homogenous strong basophilic, migration of nucleoli beneath the nucleolemma and appearance of cortical alveoli. in the vitellogenic phase, the nucleolemma become convoluted and yolk droplet appears. in mature phase increase in size and migration of nucleus to the animal pole happen. the oviducts in these species are a pair highly convoluted tube, which is placed ventral to the vertebral column from base of lung to cloaca. that can be divided into three parts according to their morphological characteristic: infundibulum, ampula and ovisac. the oviduct is composed of a luminal mucosa, a lamina propria, a circular muscle layer, and an outer serosa. 6. this study deals with the histomorphology of the mesonephros in male and female neurergus microspilotus. the slender and narrow kidneys lie in the retro peritoneal position up against the ventral aspect of vertebral column and can extend from the esophagio-stomach junction to cloaca. the kidney in both sex composed of sexual (anterior) and pelvic (posterior) parts. the structure of sexual kidney is different in male and female. in the male sperm leave the testis through efferent ducts after entering the sexual kidney, vasa efferent join together and make bidders duct. this duct is joining the bowman’s capsule of kidney before leaving the sexual kidney. they make collecting ducts which are filled with both sperm and urine. after leaving the kidney, all these collecting ducts are connected to wolffian duct. wolffian duct joines the ureters (merge from definite kidney) just before entering the cloaca. based on serial sections in paraffin nephrons are consists of different parts. they are composed of a filtration unit, the malpighian corpuscle, and a renal tubule, which can be divided into 4 morphologically distinct segments: proximal tubule (first and second segment), distal tubule, and collecting tubule. collecting tubules merge and form a branch system that opens into collecting ducts. 7. sperm storage in cloacal spermathecae was studied in female n. kaiseri during the breeding season in two specimens kept at a captive breeding facility using light microscopy.two individuals showed stored sperm with similar spermathecal ulterastucture. the spermathecae exhibited characteristics of secretory epithelium with irregular nuclei surrounded by thin cytoplasm and without organelles involved in synthetic activities. within spermathecal tubules filled with secretory material, relatively small groups of sperm are aligned along their entire lengths in parallel arrays. some of these spermatozoa are embedded in the secretory matrix or pushed deeper into the spermathecal epithelium. considering the onset of courtship behavior in early december, and deposition of first eggs in late february, it is inferred that sperm storage in this species lasts for 1.5-2 months. this study provides the ?rst description of sperm storage at the tissue and cellular levels in n.kaiseri. 8. we studied variation in the sizes of erythrocytes and their nucleus in two closely related species of mountain newts neurergus kaiseri and neurergus microspilotus living in two differing environments. blood smears stained with giemsa were utilized. the erythrocytes were found to be more elongated and bulky in n. kaiseri with a broader nucleus. in n. microspilotus, the erythrocytes were small with relatively elongated nucleus. the nuclear membrane showed crenation in both species, which is located central or eccentric in both n. kaiseri and n. microspilotus. 9. during first few months of establishing the captive breeding facility for n. microspilotus at razi university a group of n.kaiseri and n.microspilotus kept at this facility inflected with several diseases and suffered heavy mortality. here, we briefly describe several cases of chytridiomycosis diagnosed based on histological evidence, one case of red-leg syndrome (rls) based on clinical syndromes and one case of bacterial infection linked to the mortalities and discuss possible environmental factors associated with these mortalities in the cbf. we also provided recommendations for a better husbandry and well being of the newts. details on several casual symptoms found in dead newts including hepatic enlargement, hepatic melanomacrophage, and accumulation of gelatinous material are provided. details descriptions of death causes resulted from chytridiomycosis, red-leg syndrome (rls) and bacterial infection will be reported in separate articles.