Characterization of interdigital glands in the Asian elephant (Elephas maximus)

In the Asian elephant, wetness akin to perspiration is commonly observed on the cuticles and interdigital areas of the feet; this observation has lead to speculation regarding the existence of an interdigital gland. Our goal was to search for interdigital glands and characterise them morphologically, histochemically, and immunohistochemically. Necropsy samples of interdigital areas from two Asian elephants were obtained. Multiple sections were fixed and processed routinely, then stained with hematoxylin/eosin and differential mucin stains. Immunohistochemistry was also performed for cytokeratins 8 and 10. Interdigital glands resembling human eccrine glands were detected deep within the reticular dermis. Histochemical staining indicated neutral mucopolysaccharides and nonsulphated acid mucopolysaccharides in glandular secretions, and the glandular epithelium also showed immunoreactivity to cytokeratins 8 and 10. Both the histochemical and immunohistochemical staining patterns are analogous to human eccrine structures. This study shows with certainty that Asian elephants possess sweat glands as they are defined histologically.

The origin and evolution of the woolly mammoth

The mammoth lineage provides an example of rapid adaptive evolution in response to the changing environments of the Pleistocene. Using well-dated samples from across the mammoth's Eurasian range, we document geographical and chronological variation in adaptive morphology. This work illustrates an incremental (if mosaic) evolutionary sequence but also reveals a complex interplay of local morphological innovation, migration, and extirpation in the origin and evolution of a mammalian species. In particular, northeastern Siberia is identified as an area of successive allopatric innovations that apparently spread to Europe, where they contributed to a complex pattern of stasis, replacement, and transformation.

Genetic evidence for two species of elephant in Africa

Elephants from the tropical forests of Africa are morphologically distinct from savannah or bush elephants. Dart-biopsy samples from 195 free-ranging African elephants in 21 populations were examined for DNA sequence variation in four nuclear genes (1732 base pairs). Phylogenetic distinctions between African forest elephant and savannah elephant populations corresponded to 58% of the difference in the same genes between elephant genera Loxodonta (African) and Elephas (Asian). Large genetic distance, multiple genetically fixed nucleotide site differences, morphological and habitat distinctions, and extremely limited hybridization of gene flow between forest and savannah elephants support the recognition and conservation management of two African species: Loxodonta africana and Loxodonta cyclotis.

High-resolution electron microscopy of the crystallites of fossil enamels obtained from various geological ages

To elucidate the stability of the central dark line (CDL) in biologically induced hydroxyapatite crystals, we examined the diagenetic changes on the microstructures of the crystallites during the course of fossilization. Using transmission electron microscopy, we investigated the enamel crystallites of fossil animals of various geological ages ranging from Pleistocene to Cretaceous. Electron micrographs indicated that the microstructures and lattice images of each crystallite in fossil enamels were well-preserved regardless of the thickness of the enamel layer, and the presence of CDLs in fossil enamel crystals was also confirmed. The results indicated that the microstructure of hydroxyapatite crystals containing lattice images of CDLs appear stable during long geological periods. In addition, we conclude that the existence of lattice images in apatite with CDLs may be an indicator for the assessment of the evolution of dental enamel from fossil remains.

Muscle architecture of the elongated nose in the Asian elephant (Elephas maximus)

The architecture of the M. caninus in the elongated nose was examined in the Asian elephant (Elephas maximus). The following complicated musculature of the M. caninus was observed in the proximal and distal regions of the nose: (1) Proximal region: In the superficial layer, the longitudinal bundles are confirmed in the dorsal part, and the obliquely-oriented ones in the ventral part. In the middle layer, some bundles run ventro-distally, while other ones represent longitudinally-oriented running. The deep layer consists of complicated architecture of many bundles. Some muscle bundles run medio-laterally, while the others extend proximo-distally in this space. (2) Distal region: In the dorsal part of the M. caninus, the bundles run at deep-superficial direction, while in the ventral part the bundles are longitudinally arranged. The bundles run at lateral direction near the septum of the nasal conduits. The N. facialis and N. infraorbitalis send many branches in the lateral area of the M. caninus in the trunk. This muscle architecture of multi-oriented bundles and well-developed innervation to them suggest that they enable the elongated nose to act as a refined manipulator in the Asian elephant.

Snorkel breathing in the elephant explains the unique anatomy of its pleura

It has been known for over 300 years that the anatomy of the elephant lung is unique among mammals in that the pleural cavity is obliterated by connective tissue. However no satisfactory explanation has been advanced. Recent studies suggest that the elephant has an aquatic ancestry and the trunk may have developed for snorkeling. In addition, the modern day elephant is the only mammal that can remain submerged far below the surface of the water while snorkeling. The resulting differences of pressures within the thorax mean that the small blood vessels of the pleura are in great danger of rupturing or causing severe edema. The same distribution of pressures occurs when the animal raises water inside its trunk prior to drinking although in this case the pressure differences are relatively short-lived. Evolution has provided a remarkable solution to this problem by replacing the normally delicate parietal and visceral pleurae by dense connective tissue, and separating the two pleurae by loose connective tissue to allow some sliding movement.

An overview of the central nervous system of the elephant through a critical appraisal of the literature published in the XIX and XX centuries

The two species of elephants (Indian: Elephas maximus and African: Loxodonta africana) possess the largest brain among land mammals. Due to its size, the elephant brain is discussed in virtually every paper dealing with the evolution of the central nervous system of mammals and comparative brain size. Studies on the social habits of elephants also deal with the skills and the "intelligence" and brain size of these species. Yet most of the descriptions and conclusions reported in comparative studies rely on second-hand data derived from investigations performed several decades before, often dating as far back as the XIX century. Furthermore, many of the original papers actually describing gross and detailed features of the brain of elephants are either no longer available, are written in languages other than English, or are difficult to trace. The present study gives a short description of the anatomy of the central nervous system of elephants, with special attention to its distinctive features, reports all available literature on the subject, and briefly discusses its origins and rationale.

Elephant dental pulp tissue: where are the nerves?

Dental pulp tissue from three elephants was examined histologically with hematoxylin and eosin and s-100 protein stains. In all specimens, normal pulp was found with the exception that no nerve fibers (myelinated or non-myelinated) were demonstrable in any of the numerous sections prepared.

Histogenesis of the chequered pattern of ivory of the African elephant (Loxodonta africana)

This study aimed to propose a hypothesis on the events which lead to the development of the characteristic chequered pattern of elephant ivory. Twenty fragments of ivory and six elephant tusks were obtained through the National Parks Board of South Africa. Polished surfaces were prepared in sagittal and longitudinal planes and the characteristics of the distinctive chequered pattern described. Light- and electron-microscopical techniques and image analyses were employed to determine the morphological basis of the pattern and to describe the spatial distribution, density and morphology of the dentinal tubules. These investigations showed that the distinctive pattern was the result of the sinusoidal, centripetal course followed by dentinal tubules. The apical, slanted part of the sinusoidal curve is the result of the centripetally moving odontoblast, which, during formation of ivory, progresses towards the centre of the tusk on a decreasing circumference. It is suggested that this leads to cell crowding, increased pressure between odontoblasts and subsequent apical movement of their cell bodies, cell degeneration and fusion. Odontoblastic degeneration and fusion probably relieve the pressure between the crowded odontoblasts by reducing their numbers and the remaining odontoblasts now orientate their centripetal course towards the tip of the tusk, thereby forming the anterior-directed part of the sinusoidal path of the tubule. As odontoblasts progress centripetally the diameter of the pulpal cavity decreases further and the processes of apical movement, fusion and degeneration of odontoblasts are repeated. This occurs until the pulpal cavity is obliterated.

Reproductive assessment of male elephants (Loxodonta africana and Elephas maximus) by ultrasonography

Transrectal ultrasonography was performed on five wild and two captive male African elephants (Loxodonta africana) and four captive male Asian elephants (Elephas maximus) to develop standards for assessment of reproductive health and status. The entire internal urogenital tract was visualized ultrasonographically by using a 3.5 MHz or a 7.5-MHz transducer in combination with a probe extension adapted for elephant anatomy. The findings were verified by postmortem ex situ ultrasound examinations in several individuals of each species. Each part of the internal urogenital tract was sonographically detectable except for the bulbourethral glands and the cranial portion of the ureters and ductus deferentes, which were only observed in situ in the neonate. Each structure visualized was measured and described. The size and morphology of the urogenital structures, especially the accessory glands, were indicative of breeding status, if known. There was a notable difference between African and Asian males in the size and morphology of the prostate gland and a slight difference in the shape of the ampullae. No other structure showed significant species differences. The detection of the location and description of the testes may provide information for modifying present castration procedures. Furthermore, ultrasound examination of the male accessory glands may aid in the identification of potential semen donors for assisted reproduction programs in captive elephants.

Predicting body weight from body measurements in Asian elephants (Elephas maximus)

Accurate estimates of body weight can be useful in the evaluations of feeding programs, nutritional status and general health, and in calculation of dose levels (such as for anesthesia)-thus providing a valuable tool for captive elephant management. We used body measurements of 75 Asian elephants (Elephas maximus) to predict body weight. Weight, heart girth, height at the withers, body length, and foot-pad circumference were measured. All possible linear regressions of weight on one, two, three, or four body measurements were calculated. The highest correlation with a single measurement was that between heart girth and weight (R2 = 0.90). The data were also divided into age groups (1-13, 18-28, 29-39, and 40-57 yr), and all possible linear regressions were calculated for each group (there were no elephants aged 14-17 yr). Adding body length or pad circumference to heart girth resulted in a slight increase in R2. We conclude that body weight in Asian elephants can be predicted from body measurements and that heart girth is the best predictor. A second body measurement might improve predictive accuracy for some age groups.

The intestine and endocrine pancreas of the African elephant: a histological immunocytochemical and immunofluorescence study

Histological, immunocytochemical and immunofluorescence methods were employed to study the intestine and endocrine pancreas of the elephant. The histological findings were in line with those in monogastric mammals. In the mucosa of intestine, endocrine cells were immunoreactive to somatostatin, gastrin, CCK, GIP, secretin, motilin, glucagon and NPY. Nerve cells immunoreactive to somatostatin, substance P, VIP, PHI, NPY, bombesin and CGRP were detected. No immunoreactivity to neurotensin was observed, islets of the pancreas had insulin cells in their cores and glucagon and somatostatin cells in their mantles. The antisera employed failed to demonstrate PP cells in the pancreas, but NPY-immunoreactive cells were present.

The sensorineural specializations of the trunk tip (finger) of the Asian elephant, Elephas maximus

BACKGROUND

The dorsal extension of the tip of the trunk of Asian elephants (Elephas maximus), often referred to as "the finger," possesses remarkable mechanical dexterity and is used for a variety of special behaviors including grasping food and tactile and ultimately chemosensory recognition via the vomeronasal organ. The present study describes a unique sensory innervation of this specialized region of the trunk.

METHODS

The tip of the dorsal aspect of the trunk is referred to as the trunk tip finger and has been studied grossly in 13 living elephants. One tip from a male Asian elephant was obtained for histologic study when it was accidentally severed. The tissue was fixed in 10% neutral buffered formalin, and portions were either sectioned frozen or embedded in paraffin and serial sectioned. Sections were stained with silver in both cases.

RESULTS

The skin of the trunk tip finger differs from that of the surrounding areas; it contains a high density of free nerve endings, numerous convoluted branched small corpuscles, and vellus vibrissae that resemble vellus hairs, which do not protrude beyond the skin surface. The finger is thus densely innervated with three distinctive types of sensory terminals. Corpuscular receptors consist of small Pacinian corpuscles and convoluted branched simple corpuscles. Both are present in the superficial dermis. Abundant regular vibrissae are present in the skin surrounding the trunk tip finger. Short vibrissae that do not protrude from the skin surface, referred to as vellus vibrissae, are abundant in the finger tip. Both types of vibrissae are innervated by hundreds of axons resembling the mystacial vibrissae of rodents. Free nerve endings are numerous in the superficial dermis, often making intimate contact with the basal cells of rete pegs.

CONCLUSIONS

The dorsal finger of the trunk tip of Asian elephants has a unique sensory innervation that resembles aspects of sensory innervation of mystacial skin of rodents or lip tissue of monkeys. This dense sensory innervation can be correlated with the tactile ability of these animals to use the trunk finger to grasp small objects for feeding and to insert chemically active samples into the ductal orifices of the vomeronasal organ for subsequent chemosensory processing.

The osteology of the African elephant (Loxodonta africana): vertebral column, ribs and sternum

The vertebral column, sternum and ribs of the African elephant were studied and illustrated. In the cervical series, the vertebrae are characterized by very short (compressed) vertebral bodies and short spinous processes. There are 20-21 thoracic vertebrae that carry ribs, and three lumbar vertebrae. The neural arches of the five sacral vertebrae fuse with each other as well as with the wings of the ilium, while the intervertebral discs do not ossify and the vertebral bodies remain separate. There are 19-21 caudal vertebrae. In the latter, the neural arches of only the first five to six vertebrae fuse dorsally, the vertebral foramens of the other vertebrae as well as the vertebral canal remain open dorsally. The body of the first rib is greatly expanded while that of the last three to four ribs are reduced. The cartilages of the first six ribs articulate with the sternum, the last five to six ribs do not bear costal cartilages and are not attached to the costal arch. The sternum consists of five sternabrae that form three approximately equal, but separate, segments. The first segment is formed by the first sternabra, the second segment is formed by the second to fourth sternabrae and the last segment is formed by the fifth sternabra. The first and second sternabrae articulate with each other by means of a synovial joint, the second to fourth sternabrae are fused to each other and the fourth and fifth sternabrae are loosely attached to each other by connective tissue.

Ultrastructure of cardiac myocyte in the Asian elephant (Elephas maximus)

Cardiac myocytes of an Asian elephant (Elephas maximus) were observed by transmission electron microscopy. Typical ultrastructural features of cardiac myocytes are exhibited in the musculature of both the left and right atria, and left ventricle of the heart. Myofibrils, mitochondria, T-system and sarcoplasmic reticulum are well-developed within the cytoplasm. Many mitochondria are characteristically concentrated is some myocytes. Cardiac musculature is also distributed in the root of the caudal vena cava. Many atrial granules are detected not only in atrial myocytes, but also in the myocytes of the caudal vena cava. Atrial natriuretic polypeptide may be secreted from the caval venous wall in the elephant.

The skull and mandible of the African elephant (Loxodonta africana)

In the present study the bones of the skull, excluding the hyoid apparatus, are described. All the bones are aerated by sinuses. In the occipital bone the squamous part is aerated from the sinus of the parietal bone, the lateral part is aerated from the tympanic bulla and the basal part from the sinus of the basisphenoid bone. Condylar foramens and hypoglossal canals are absent. A small interparietal bone is present at birth. At an early age it fuses with the surrounding cranial bones. The squamous part of the temporal bone lies sagittally in young animals, but moves progressively to a transverse plane as the animals age. A foramen lacerum is represented by jugular and oval foramens and the carotid canal. The body of the basisphenoid bone is excavated by the massive maxillary tuberosity. The latter extends to the oval foramen and contains the developing molar teeth. The ethmoturbinate, nasal and lacrimal bones are exceptionally small. In old bulls the palatine process of the incisive bones and their sinuses are gradually displaced by the palatine process of the maxillae.

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.

Morphology of the deciduous tusk (tush) of the African elephant (Loxodonta africana)

The tusk of the African elephant is preceded by a deciduous tooth generally known as the tush. Tushes from nine elephant fetuses and six calves younger than 1 year were exposed by dissection and described morphologically. All tushes consisted of a crown, root and pulpal cavity, the formation of which is completed soon after birth. They reached a maximum length of 5 cm, appeared not to erupt through the skin and were pushed aside and resorbed during enlargement of the distally located primordium of the tusk. Dental enamel, which covered the crown, could easily be removed and consisted of rods with an interwoven arrangement; the dentine-enamel junction was flat. Cellular cementum extended for variable distances over the crown and the dentine was tubular in nature. Although the tush apparently has no function, it provides the anlage and orientation for the development of its permanent successor.