How the Elephant Got Its Trunk

Proceedings of the National Academy of Sciences, 1999

The early embryology of the elephant has never been studied before. We have obtained a rare series of African elephant (Loxodonta africana) embryos and fetuses ranging in weight from 0.04 to 18.5 g, estimated gestational ages 58-166 days (duration of gestation is Ϸ660 days). Nephrostomes, a feature of aquatic vertebrates, were found in the mesonephric kidneys at all stages of development whereas they have never been recorded in the mesonephric kidneys of other viviparous mammals. The trunk was well developed even in the earliest fetus. The testes were intra-abdominal, and there was no evidence of a gubernaculum, pampiniform plexus, processus vaginalis, or a scrotum, confirming that the elephant, like the dugong, is one of the few primary testicond mammals. The palaeontological evidence suggests that the elephant's ancestors were aquatic, and recent immunological and molecular evidence shows an extremely close affinity between present-day elephants and the aquatic Sirenia (dugong and manatees). The evidence from our embryological study of the elephant also suggests that it evolved from an aquatic mammal.

Journal of Morphological Sciences, 2014

PeerJ

BackgroundElephants are the largest and heaviest living terrestrial animals, but information on their histology is still lacking. This study provides a unique insight into the elephant’s organs and also provides a comparison between juvenile Asian elephants and adult Asian elephants or other species. Here we report on the histological structure of 24 organs, including the skin, brain (cerebrum, cerebellar hemisphere, vermis, thalamus, midbrain), spinal cord, sciatic nerve, striated skeletal muscle, cardiac muscle, bone (flat bone and long bone), cartilage (hyaline cartilage and fibrocartilage), heart (right atrium, right ventricle), blood vessels (aorta, pulmonary artery and caudal vena cava), trunk, trachea, lung, tongue, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine (cecum, colon, rectum), liver and pancreas, kidney, ovary, uterus (body and horn) and spleen of two juvenile Asian elephants.MethodsTissue sections were stained with Harris’s hematoxyl...

Science (New York, N.Y.), 2011

in the Doushantuo fossils [for example, opalinids are multinuclear (32)]. Only volvocalean embryos show so many rounds of palintomy, but the resulting blastomeres are connected by a system of cytoplasmic bridges (35) that are not present in the fossils. The combination of palintomy within a multilayered cyst wall and peanut-shaped germination stages as seen in the fossils conforms to the pattern seen in nonmetazoan holozoans; nonetheless, there are no discrete characters in the Doushantuo fossils that are uniquely holozoan. The "animal embryos" likely represent nonmetazoan holozoans or possibly even more distant eukaryote branches.

2012

Proceedings of The Royal Society B: Biological Sciences, 2000

The African and Asian elephants and the mammoth diverged ca. 4^6 million years ago and their phylogenetic relationship has been controversial. Morphological studies have suggested a mammoth^Asian elephant relationship, while molecular studies have produced con£icting results. We obtained cytochrome b sequences of up to 545 base pairs from ¢ve mammoths, 14 Asian and eight African elephants. A high degree of polymorp hism is detected within species. With a dugong sequence used as the outgroup, parsimony and maximum-likelihood analyses support a mammoth^African elephant clade. As the dugong is a very distant outgroup, we employ likelihood analysis to root the tree with a molecular clock, and use bootstrap and Bayesian analyses to quantify the relative support for di¡erent topologies. The analyses support the mammoth^African elephant relationship, although other trees cannot be rejected. Ancestral polymorphisms may have resulted in gene trees di¡ering from the species phylogeny. Examination of morphological data, especially from primitive fossil members, indicates that some supposed synapomorphies between the mammoth and Asian elephant are variable, others convergent or autapomorphous. A mammoth^African elephant relationship is not excluded. Our results highlight the need, in both morp hological and molecular phylogenetics, for multiple markers and close attention to within-taxon variation and outgroup selection.

Zoo Biology, 1988

Detailed gross examinations of the reproductive tracts of three mature female nulliparous Asian elephants were conducted to develop artificial insemination (AI) techniques. Of primary concern was the determination of the length characteristics and the size and configuration of the foramina between segments of the tract. The elephants were 13, 28, and 40 years of age and had been maintained in captivity for most of their lives. One elephant died naturally and two were euthanized for health reasons. The reproductive tracts of two of the elephants were manually palpated in situ via the urogenital canal. A fibreoptoscope was used to visualize the internal structures of the terminal reproductive tract of one elephant and to deposit dye into the vagina. The reproductive organs were removed from the body cavity, dissected, measured, and photographed. The major anatomical obstacles to overcome for standard A1 procedures (the passage of an AI pipette into the reproductive tract) were the length of the urogenital canal (85-97 cm), the constriction at the urogenital-vaginal junction, and the tight cervix. The reproductive anatomy was compared to that of previous dissections reported in the literature.

Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, 2009

In 1973, Vincent Maglio published a seminal monograph on the evolution of the Elephantidae, in which he revised and condensed the 100+ species named by Henry Fairfield Osborn in 1931. Michel Beden further revised the African Elephantidae in 1979, but little systematic work has been done on the family since this publication. With addition of new specimens and species and revisions of chronology, a new analysis of the phylogeny and systematics of this family is warranted. A new, descriptive character dataset was generated from studies of modern elephants for use with fossil species. Parallel evolution in cranial and dental characters in all three lineages of elephants creates homoplastic noise in cladistic analysis, but new inferences about evolutionary relationships are possible. In this analysis, early Loxodonta and early African Mammuthus are virtually indistinguishable in dental morphology. The Elephas lineage is not monophyletic, and results from this analysis suggest multiple migration events out of Africa into Eurasia, and possibly back into Africa. New insight into the origin of the three lineages is also proposed, with Stegotetrabelodon leading to the Mammuthus lineage, and Primelephas as the ancestor of Loxodonta and Elephas. These new results suggest a much more complex picture of elephantid origins, evolution, and paleogeography. Anat Rec, 2010. © 2009 Wiley-Liss, Inc.

Animal Reproduction Science, 2011

Information on the ovarian follicle reserve in the African elephant (Loxodonta africana) is lacking. This study set out to determine the ratios of early preantral follicles and their relative dimensions in the ovaries of 16 African elephant aged 10 to 34 years. The ovaries were sectioned histologically. Follicles were counted and classified according to expansion of the pre-granulosa cells. Early primary follicles were the most common (75.8% ± 11.8%), followed by true primary follicles (23.8% ± 11.8%), whereas primordial follicles were the most rare (< 2%). Measurements made on at least 100 early preantral follicles from each animal (n = 1464) indicate that growth in oocyte and nuclear diameters started with transition to the true primary stage P < 0.01. This, together with the observed ratios between the three types of early preantral follicles suggest that both classical primordial and early primary follicles contribute to the ovarian reserve in the African elephant.

Zoological Journal of the Linnean Society, 2014

The understanding of Earth's biodiversity depends critically on the accurate identification and nomenclature of species. Many species were described centuries ago, and in a surprising number of cases their nomenclature or type material remain unclear or inconsistent. A prime example is provided by Elephas maximus, one of the most iconic and well-known mammalian species, described and named by Linnaeus and today designating the Asian elephant. We used morphological, ancient DNA (aDNA), and high-throughput ancient proteomic analyses to demonstrate that a widely discussed syntype specimen of E. maximus, a complete foetus preserved in ethanol, is actually an African elephant, genus Loxodonta. We further discovered that an additional E. maximus syntype, mentioned in a description by John Ray (1693) cited by Linnaeus, has been preserved as an almost complete skeleton at the Natural History Museum of the University of Florence. Having confirmed its identity as an Asian elephant through both morphological and ancient DNA analyses, we designate this specimen as the lectotype of E. maximus.