Kidney of the great Indian rhino Rhinoceros unicornis, Linnaeus

Trends and current state of research on greater one-horned rhinoceros (Rhinoceros unicornis): A systematic review of the literature over a period of 33 years (1985-2018)

Greater one-horned rhinoceros (Rhinoceros unicornis) is one of the most iconic wildlife species in the world. Once reduced to fewer than 500 during the 1960s, its global population has been recovering and is now over 3500, thanks to effective conservation programs in India and Nepal, the only two countries in the world where this species is found. It is one of the greatest success stories in biodiversity conservation given that hundreds of other species have disappeared, and thousands of species are on the verge of extinction. However, poaching is not the only threat for the long-term survival of rhinoceros. Loss and degradation of grassland habitat and the drying-up of wetlands are emerging threats predicted to worsen in the future, but the published information on rhinoceros has never been synthesized. In order to better understand the trends and current status of rhinoceros research and identify research gaps inhibiting its long-term conservation, we analyzed the themes discussed in 215 articles covering a period of 33 years between 1985 and 2018. Our findings suggest that studies on both free-ranging and captive rhinoceros are skewed towards biological aspects of the species including morphology, anatomy, physiology, and behaviour. There are no studies addressing the likely effects of climate change on the species, and limited information is available on rhinoceros genetics, diseases, habitat dynamics and the impacts of tourism and other infrastructure development in and around rhinoceros habitat. These issues will need addressing to maintain the conservation success of greater one-horned rhinoceros into the future.

Urinalysis in three species of captive rhinoceros (Rhinoceros unicornis, Dicerorhinus sumatrensis, and Diceros bicornis)

This study reports urinalysis values for three species of captive rhinoceros (Rhinoceros unicornis, Dicerorhinus sumatrensis, and Diceros bicornis) and evaluates individual and species differences. Repeated urinalysis was conducted on 11 individuals to establish normal reference ranges. Although no individual or species differences existed in urinary values for pH, all species differed in specific gravity. Rhinoceros urine demonstrated many physical and chemical properties similar to that of the horse, but reliability of this comparison was limited. Urinary pH in the rhinoceros was within range of that established for the horse and other large herbivores. However, all rhinoceros species exhibited urinary specific gravities below the lower limit of the normal equine reference range. Comparative urinalysis using an outside laboratory source confirmed the results of this study and illustrated the value of conducting in-house analysis. These results are the first data available on reference ranges for urine parameters in the greater one-horned, Sumatran, and African black rhinoceros and provide a useful diagnostic tool for the veterinary care of individuals in captivity.

Morphological evidence of marine adaptations in human kidneys

Amongst primates, kidneys normally exhibiting lobulated, multipyramidal, medullas is a unique attribute of the human species. Although, kidneys naturally multipyramidal in their medullary morphology are rare in terrestrial mammals, kidneys with lobulated medullas do occur in: elephants, bears, rhinoceroses, bison, cattle, pigs, and the okapi. However, kidneys characterized with multipyramidal medullas are common in aquatic mammals and are nearly universal in marine mammals. To avoid the deleterious effects of saline water dehydration, marine mammals have adaptively thickened the medullas of their kidneys--which enhances their ability to concentrate excretory salts in the urine. However, the lobulation of the kidney's medullary region in marine mammals appears to be an adaptation to expand the surface area between the medulla and the enveloping outer cortex in order to increase the volume of marine dietary induced hypertonic plasma that can be immediately processed for the excretion of excess salts and nitrogenous waste. A phylogenetic review of freshwater aquatic mammals suggest that most, if not all, nonmarine aquatic mammals inherited the medullary pyramids of their kidneys from ancestors who originally inhabited, or frequented, marine environments. So this suggest that most, if not all, aquatic mammals exhibiting kidneys with lobulated medullas are either marine adapted--or are descended from marine antecedents. Additionally, a phylogenetic review of nonhuman terrestrial mammals possessing kidneys with multipyramidal medullas suggest that bears, elephants and possibly rhinoceroses, also, inherited their lobulated medullas from semiaquatic marine ancestors. The fact that several terrestrial mammalian species of semiaquatic marine ancestry exhibit kidneys with multipyramidal medullas, may suggest that humans could have, also, inherited the lobulated medullas of their kidneys from coastal marine ancestors. And a specialized marine diet in ancient human ancestry could, also, explain the reactivation and enumeration of corporeal eccrine sweat glands and the copious secretion of salt tears. The substantial loss of genetic variation in humans relative to other hominoid primates, combined with the apparent isolation of early Pliocene human ancestors from particular retroviruses that infected all other African primate species, may suggest that such a semiaquatic marine phase, during the emergence of Homo, may have occurred on an island off the coast of Africa during the early Pliocene.

Kidney of elephants

BACKGROUND

Elephants are an important and isolated order. Their kidneys need substantial investigation and hitherto have not been portrayed even by a pyelogram.

METHODS

Pyelograms and injection of vessels with colored acrylic emulsions were done initially. Dissection was under fiberoptics using a dissecting microscope with frequent measurements. Special areas were cut for microscopy (light and electron) and photography. Glomerular counts were done by macerating weighted pieces of cortex and later finding the cortical fraction of the renal parenchyma.

RESULTS

The elephant kidney is devoid of dorsoventral symmetry. It is composed of 8 +/- 2 lobes separated by fine interlobar septa. There is no reduction of lobes with maturity. The pelvis bifurcates at the sinus into primary branches or infundibula which dispatch a secondary branch or infundibulum into every lobe. Interlobar arteries and veins, nerves, fat, and connective tissue generally accompany every secondary infundibulum into its lobe. A major branch of the renal artery may perforate the renal capsule and course to the cortico-medullary (C-M) border independently of the secondary infundibulum to that lobe. The number of glomeruli per kidney is approximately 15 x 10(6). In adults the glomerular mass is 4.9 +/- 0.5% of the renal parenchyma and 6.7 +/- 0.3% of the cortex. Areae cribrosae occur generally at low papillae. They are the outlets of numerous terminal collecting ducts which may be accompanied by a tubus maximus (T.M.) A T.M. of diameter 1.6 mm and length 10 mm may act as the only substitute for an area cribrosa. Wide anastomoses between the two main renal veins occur within the renal sinus. Intralobar arteries and veins often course right through the outer medulla to and from, respectively, the C-M border.

CONCLUSIONS

Anatomically, an elephant's kidneys appear to be able to concentrate urine only moderately. Their kidneys tend to resemble those of the manatee but not of the dugong.

Renal anatomy of the pigmy hippopotamus (Choeropsis liberiensis): an overview

The adult kidney of Choeropsis liberiensis is 74.8% cortex and 22.9% medulla. The neonatal cortex is relatively less. A single kidney has about 3 x 10(6) glomeruli. These form 5% of renal mass in the adult but more so in neonates. The primary tubus maximus, TM1, follows the lateral curvature of the kidney. It gives off, toward the hilum, dorso-ventrally paired secondary tubi maximi, TM2. The tubi are a single layer of high cuboidal epithelium from which terminal collecting ducts arise throughout the surrounding inner medulla. The cranial and caudal limbs of TM1 open at a diminutive pelvis which receives a small papilla in continuity with TM1. The medulla is continuous although variably distorted by folds of cortex at the lateral curvature of the kidney. The renal lobes project toward the medial border and consist of cortex, medulla and TM2. The lobar cortex is continuous with the common cortex of the lateral curvature. The kidney, although strongly lobed, has no infundibula or rencules. A main peripheral vein courses medial and parallel to TM1. It is apparently a modified large arcuate vein and receives arcuate and interlobar tributaries. At the level of the papilla it joins the main renal vein. The arterial supply is mainly by interlobar arteries but there are also sizeable external perforator arteries which branch from the main renal artery and perforate the cortex of lobes about the hilum. The source of the arteries is illustrated.

Further studies on the kidney of the hook-lipped African rhinoceros, Diceros bicornis

A healthy, pregnant Diceros bicornis (No. 29455), with histologically normal but relatively large kidneys containing a correspondingly large number of nephrons, died suddenly from an injury. Renal lobation was studied partly from serial transverse cuts across the kidney. The fibromuscular pelvic conduits, which are a craniocaudal bifurcation of the ureter, are associated with prominent longitudinally disposed paraconduital veins which anastomose with the interlobar veins. The arcuate veins open widely into the paraconduital veins. The latter drain into the major tributaries of the renal vein at the renal sinus. The interlobar arteries enter the parenchyma through the interlobar septa. These arteries release internal perforator branches, through the septa, which pass to the corticomedullary border, branch along that border as arcuate arteries, and release cortical branches centrifugally. All these branches give off twigs to the glomeruli. Relative renal mass of mammals is inversely proportional to their adult body mass. This is indicated by a regression line which includes rhinoceroses. D. bicornis No. 29455, accordingly, has exceptionally large kidneys. The mesonephros of the 75 mm fetus of D. bicornis has mature glomeruli and tubules. The metanephros has pelvic conduits, paraconduital veins, but, as yet, no medullary loops.

The kidney of tapirs: a macroscopical study

The renal cortex of tapirs, water-loving primordial ungulates, was continuous, nonlobed, and about 80% of renal mass in adult and 71% in term-neonate. In the neonates even the peripheral glomeruli were moderately mature. Tapirus bairdi had about 4 million glomeruli per kidney and T. pinchaque about 3 million smaller glomeruli. Number of glomeruli per gm of cortex was 12,444 in T. bairdi and 13,400 in T. pinchaque. Cortical loops were common in the medullary rays. The medulla was the simple crest-type. The terminal collecting ducts (T.C.D.) opened separately at the crest and not into a tubus maximus. The "outer stripe" of the outer medulla apparently was telescoped into the deep cortex. The medullary loops turned at a thick portion and at nearly all levels of the medulla. The medullary crest was lined by urothelium which extended into the ends of the T.C.D. Otherwise the T.C.D. were made of columnar epithelium. The pelvic urothelium was continuous with that of the medullary crest at the dorsal and ventral fornices. The fornices were well within the inner medulla. Hence only inner medulla could be exposed to pelvic urine. The hilar arteries, unlike the other two perissodactyl families (rhinoceri and equids), passed through the cortico-medullary (C-M) border and some large arteries and veins passed through the outer medulla to and from the C-M border without branches or tributaries. Unlike kidneys with a medullary crest in diverse eutherian mammals, tapirs lacked pelvic extensions along the major intrarenal blood vessels and thus lacked pelvic intervascular eminences.

Renal morphology of the hook-lipped African rhinoceros, Diceros bicornis, Linnaeus

The kidney of Diceros bicornis has about 60 lobes, all appearing peripherally. These are separated by interlobar septa, except for small septal defects through which tubules pass. Renal capsule and interlobar septa are fibromuscular and contain small blood vessels. The kidney is about 65% cortex. It contains about 12.5 x 10(6) glomeruli, which form about 7% of the cortical mass and 4.6% of the renal mass. Diameter of a glomerular capsule is about 244 microns, there being no difference in size across the cortex in these adults. The ureter bifurcates into a cephalic and a caudal, fibromuscular, urothelial-lined conduit, into which open about 23 urothelial-lined infundibula. The common large collecting duct, or tubus maximus, of every lobe opens at the apex of its infundibulum. Two tubi may join into one infundibulum. The tubi and their terminal collecting ducts (of Bellini) are part of the inner medulla. Musculature of conduits and infundibula is largely longitudinal. The calyx may be represented by a circular muscle bundle near the apex of every infundibulum. The large intralobar veins are partly adherent to their infundibulum and calyx and receive arcuate veins via valved orifices. Most branches of the renal artery enter via the interlobar septa. Within a septum they branch again and also supply numerous perforators, which thence enter the cortex. Remaining branches of the renal artery enter cortex directly from without. A fibromuscular scaffolding lies deep to arcuate veins where they contact medulla. Where these veins contact cortical tubules; however, their walls become merely endothelium, like the walls of the interlobular veins.

Renal anatomy of the manatee, Trichechus manatus, Linnaeus

The manatee kidney is composed of several closely apposed lobes. These are formed by cortical folds (plicae corticales) that completely isolate the medullae, except where the medullae of adjacent lobes are partially fused. The cortex is continuous; its folds usually are separated, but only partially, by interlobar septa extending from the renal capsule. The cortex makes up approximately 57% of renal mass in adults and 68% in the calf. There are about 3 million glomeruli per kidney. The average is somewhat less than that expected of an adult eutherian of equal mass. The glomeruli, however, are large; they form 7.38% +/- 1.33 of cortical mass, which is above that for at least ten unrelated adult eutherians. The number of glomeruli per gram of cortex is considerably greater in the calf than in the adult. The medullae are about 43% of renal mass. The cortico-medullary thickness ratio is 0.08 to 0.24. All terminal collecting ducts open at a crater (cratera cribrosa) of varying depth. Hair-pin loops occur at all levels of medulla, and apparently all loops bend at their thick segment. Cortical loops occur in the medullary rays. Vascular bundles were evident at the cortico-medullary border and thin tubules extended into the medulla from the central ends of the medullary rays (cortical) in seven out of the nine kidneys. The renal pelvis is separated from the central ends of the cortical folds by delicate fascia through which pass the interlobar vessels. There are no fornices and no infundibula. The collagenous tissue of the pelvic wall extends across most of the pelvic surface of the outer medulla.