Morphological adaptations during development of the kidneys in Vampire bats.

Tissue changes during embryonic and postnatal development are critical for the success of physiological processes later in mammalian life. Dietary transition from milk to a variety of other food items is one of the factors inducing these changes in mammal species. Blood is utilized as food by only three species of vampire bats among all living mammals. Considering its high protein content, this unique diet is known to induce several metabolic changes, including fasting susceptibility. However, changes in the renal function to meet the excretory needs associated to the blood diet are unknown. Here we aimed at investigating morphological alterations in vampires' kidneys during embryonic and post-natal development in order to better understand the evolutionary adaptations allowing sanguivory. Common vampire bats (Desmodus rotundus) were captured and had their kidneys removed for histological, morphometrical and stereological analysis. Our results showed increased glomerular area and higher glomerular and uriniferous tubules volumetric densities in adults compared to developing bats. These results, together with a higher Renal Somatic Index and a thicker inner medulla also reported for adults, support renal hypertrophy due to increased renal function in blood-feeding vampires as compared to the earlier life stages. We also report a lower foot process density and its different arrange inside the glomerular capsule in adults, indicating an adaptation to a larger extracellular volume formed by increased glomerular filtration. Taken together, kidney morphological changes reported here for vampire bats may reflect in adults' adaptations to a monotrophic strategy.

Aspects regarding renal morphophysiology of fruit-eating and vampire bats.

Bats have adapted to many different feeding habits, which are known to induce morphophysiological adaptations in several tissues, especially those particularly involved with absorption, metabolism and excretion. The common vampire bat (Desmodus rotundus) has a very unique diet (blood), which, among other challenges, seems to pose a risk to their kidneys, due to the increased nitrogen excretion imposed by their remarkably high protein meal. Fruit-eating bats (Artibeus lituratus) consume a high carbohydrate diet and may be taken as a suitable species for this dietary comparative study. Here we aimed at investigating the renal morphology and stereology, kidneys antioxidant capacity, and plasma antidiuretic hormone (ADH) concentrations in adult fruit-eating and vampire bats. Sixteen animals were captured and used in this study, being 8 adult males from each species. Our results showed higher morphological standards of glomerular area, volumetric density of glomeruli, and renal somatic index for vampire bats, as well as higher reactive species of oxygen (ROS) production, such as nitric oxide (NO), higher plasma iron reduction ability (FRAP), higher activity of the antioxidant enzyme glutathione-S-transferase (GST) and a higher malondialdehyde production (MDA) in vampires' kidneys, compared to the fruit-eating species. The activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) were higher in fruit-eating bats. Plasma ADH concentrations were not different between species. Taken together, the renal morphophysiology conditions presented by vampire bats might be associated with a high demand for nitrogenous products excretion imposed by protein and iron overload. These features may play an important role on preventing protein-overload nephropathy, allowing vampires to survive under such a unique diet.

The spermatogenic process of the common vampire bat Desmodus rotundus under a histomorphometric view.

Among all bat species, Desmodus rotundus stands out as one of the most intriguing due to its exclusively haematophagous feeding habits. However, little is known about their spermatogenic cycle. This study aimed at describing the spermatogenic process of common vampire bats through testicular histomorphometric characterization of adult specimens, spermatogenic production indexes, description of stages of the seminiferous epithelium cycle and estimative of the spermatogenic process duration. Morphometrical and immunohistochemical analyzes for bromodeoxiuridine were conducted under light microscopy and ultrastructural analyzes were performed under transmission electron microscopy. Vampire bats showed higher investment in gonadal tissue (gonadosomatic index of 0.54%) and in seminiferous tubules (tubulesomatic index of 0.49%) when compared to larger mammals. They also showed a high tubular length per gram of testis (34.70 m). Approximately half of the intertubular compartment was found to be comprised by Leydig cells (51.20%), and an average of 23.77x106 of these cells was found per gram of testis. The germline cells showed 16.93% of mitotic index and 2.51% of meiotic index. The overall yield of spermatogenesis was 60% and the testicular spermatic reserve was 71.44x107 spermatozoa per gram of testis. With a total spermatogenesis duration estimated at 37.02 days, vampire bats showed a daily sperm production of 86.80x106 gametes per gram of testis. These findings demonstrate a high sperm production, which is commonly observed in species with promiscuous mating system.