No abstract

At present, the worldwide captive elephant population is not self‐sustaining. The major reason for low reproductive rates is the heretofore undiagnosed reproductive disorders of nulliparous females of prime breeding age. Recent advances in ultrasound technology have facilitated the detection of these disorders in non‐sedated animals. Approximately 2,000 ultrasonographic examinations were performed in more than 280 captive and wild African and captive Asian female elephants. The entire urogenital tract was scanned, measured, and documented to provide a reference for ultrasound specialists involved in elephant breeding programs. The primary pathological lesions that influenced reproductive rates in these females were uterine tumors and endometrial cysts and ovarian cysts that resulted in acyclicity. The detection of these disorders and their stage of development can be used by elephant managers to make decisions approximately which animals to include in breeding programs. Ultrasonography can be used as an effective tool for assessing the reproductive fitness of female breeding candidates in both African and Asian elephants. Zoo Biol 19:321–332, 2000. © 2000 Wiley‐Liss, Inc.

Major evolutionary transitions, in which animals develop new body plans and adapt to dramatically new habitats and lifestyles, have punctuated the history of life. The origin of cetaceans from land-living mammals is among the most famous of these events. Much earlier, during the Mesozoic Era, many reptile groups also moved from land to water, but these transitions are more poorly understood. We use computed tomography to study changes in the inner ear vestibular system, involved in sensing balance and equilibrium, as one of these groups, extinct crocodile relatives called thalattosuchians, transitioned from terrestrial ancestors into pelagic (open ocean) swimmers. We find that the morphology of the vestibular system corresponds to habitat, with pelagic thalattosuchians exhibiting a more compact labyrinth with wider semicircular canal diameters and an enlarged vestibule, reminiscent of modified and miniaturized labyrinths of other marine reptiles and cetaceans. Pelagic thalattosuchians with modified inner ears were the culmination of an evolutionary trend with a long semiaquatic phase, and their pelagic vestibular systems appeared after the first changes to the postcranial skeleton that enhanced their ability to swim. This is strikingly different from cetaceans, which miniaturized their labyrinths soon after entering the water, without a prolonged semiaquatic stage. Thus, thalattosuchians and cetaceans became secondarily aquatic in different ways and at different paces, showing that there are different routes for the same type of transition.

The identity of the cells that form the periosteum during development is controversial with current dogma suggesting these are derived from a Sox9-positive progenitor. Herein, we characterize a newly created Prrx1eGFP reporter transgenic mouse line during limb formation and postnatally. Interestingly, in the embryo Prrx1eGFP-labeled cells become restricted around the Sox9-positive cartilage anlage without themselves becoming Sox9-positive. In the adult, the Prrx1eGFP transgene live labels a subpopulation of cells within the periosteum that are enriched at specific sites, and this population is diminished in aged mice. The green fluorescent protein (GFP)-labeled subpopulation can be isolated using fluorescence-activated cell sorting (FACS) and represents approximately 8% of all isolated periosteal cells. The GFP-labeled subpopulation is significantly more osteogenic than unlabeled, GFP-negative periosteal cells. In addition, the osteogenic and chondrogenic capacity of periosteal cells in vitro can be extended with the addition of fibroblast growth factor (FGF) to the expansion media. We provide evidence to suggest that osteoblasts contributing to cortical bone formation in the embryo originate from Prrx1eGFP-positive cells within the perichondrium, which possibly piggyback on invading vascular cells and secrete new bone matrix. In summary, the Prrx1eGFP mouse is a powerful tool to visualize and isolate periosteal cells and to quantify their properties in the embryo and adult.

The endocrinology of the elephant estrous cycle has been well characterized, but little emphasis has been placed on evaluating corresponding changes in the reproductive tract. Ultrasound was used to document changes in reproductive tract morphology throughout the estrous cycle in four cycling female African elephants. During a 7‐month period, frequent ultrasound examinations (n = 190) during the luteal and non‐luteal phase were compared with serum progesterone and luteinizing hormone (LH) concentrations during a 7‐month period. Ultrasonographic images documented vaginal and cervical edema and changes in mucus consistency during the non‐luteal phase. The cross‐sectional diameter of the endometrium showed a dramatic increase during the non‐luteal phase and followed cyclic changes. A different pattern of follicular development on the ovary was associated with the two LH surges. Follicle growth associated with the first, anovulatory LH surge was characterized by the formation of multiple small follicles, in contrast to the maturation of a single large follicle at the second, ovulatory LH (ovLH) surge. Ovulation and the subsequent formation of a corpus luteum (CL) were observed only after the ovLH surge. Ultrasound data in combination with endocrine assessments suggest that the African elephant is non‐ovulatory, although multiple non‐ovulatory luteal structures developed during the late non‐luteal phase of each cycle. Both ovulatory CL and non‐ovulatory luteal structures were present only through one cycle and regressed at the end of the luteal phase in conjunction with the drop in serum progesterone. We conclude that periodic reproductive‐tract ultrasound assessments in association with continued endocrine monitoring of the estrous cycle should be incorporated into the routine reproductive health assessment of elephants. This information is necessary for determining reproductive fitness before making breeding recommendations. It also has proven to be an invaluable tool for use with assisted reproductive techniques and has enormous potential for evaluating the efficiency of hormonal therapies used to treat reproductive dysfunction. Zoo Biol 19:369–382, 2000. © 2000 Wiley‐Liss, Inc.

This study quantifies the shape change in elephant manus and pes anatomy with increasing body mass, using computed tomographic scanning. Most manus and pes bones, and manus tendons, maintain their shape, or become more gracile, through ontogeny. Contrary to this, tendons of the pes become significantly more robust, suggesting functional adaptation to increasingly high loads. Ankle tendon cross-sectional area (CSA) scales the highest in the long digital extensor, proportional to body mass 1.08G0.21 , significantly greater than the highest-scaling wrist tendon (extensor carpi ulnaris, body mass 0.69G0.09 ). These patterns of shape change relate to the marked anatomical differences between the pillar-like manus and tripod-like pes, consistent with differences in fore-and hindlimb locomotor function. The cartilaginous predigits (prepollux and prehallux) of the manus and pes also become relatively more robust through ontogeny, and their pattern of shape change does not resemble that seen in any of the 10 metacarpals and metatarsals. Their CSAs scale above isometry proportional to body mass 0.73G0.09 and body mass 0.82G0.07 respectively. We infer a supportive function for these structures, preventing collapse of the foot pad during locomotion.

This study provides the first evidence of pronounced temporary laryngeal descent in a bovid species. An elaborate acoustic display is prominent in male courtship behavior of polygynous Mongolian gazelle. During rut, rounding up of females is accompanied by continuous head-up barking by dominant males. Throughout the rut their evolutionarily enlarged larynx descends to a low mid-neck resting position. In the course of each bark the larynx is additionally retracted toward the sternum by 30% of the resting vocal tract length. A geometric model of active larynx movements was constructed by combining results of video documentation, dissection, skeletonization, and behavioral observation. The considerable distance between resting position and maximal laryngeal descent suggests a backward tilting of the hyoid apparatus and an extension of the thyrohyoid connection during the retraction phase. Return to the resting position is effected by strap muscles and by the elastic recoil of the pharynx and the thyrohyoid connection. An intrapharyngeal inflation of the peculiar palatinal pharyngeal pouch of adult males is inferred from a short-time expansion of the ventral neck region rostral to the laryngeal prominence. The neck of adult dominant males is accentuated by long gray guard hairs during the rut. The passive swinging of the heavy larynx of adult males during locomotion gives the impression of a handicap imposed on rutting males. Apparently, this disadvantage becomes outweighed by the profits for reproductive success.

Pneumatic vertebrae of Brachiosaurus and Dicraeosaurus 65 ABSTRACT The presacral vertebrae of sauropod dinosaurs were surrounded and invaded by a complex system of pneumatic diverticula, which originated most probably from cervical air sacs connected with the respiratory apparatus. Cervical vertebrae of Brachiosaurus brancai and Dicraeosaurus sp., two sauropods from the Late Jurassic (?Oxfordian-Kimmerigian-Tithonian) eastern African locality Tendaguru, were examined with computed tomography to visualize internal pneumatic structures. With this method, comparative reconstructions of pneumatic diverticula in the neck of these sauropods were done that help to understand the biomechanical role of vertebral pneumaticity in sauropods. Internal pneumatic structures in Brachiosaurus brancai are semicamellate with few large camerae in the vertebral centrum, surrounded by pneumatic camellae. Dicraeosaurus exhibits a procamerate pneumatization pattern with few deep fossae penetrating to a broad median strut in the vertebra, but no internal pneumaticity was found. The semicamellate pneumatization pattern of Brachiosaurus brancai corresponds with another Late Jurassic Brachiosaurus specimen, whereas in Cretaceous brachiosaurid taxa like Sauroposeidon, the complexity of internal pneumatization increases to form a fully camellate pneumatization pattern. In Dicraeosaurus, internal pneumatization has most likely secondarily been reduced.Brachiosaurus and Dicraeosaurus possess a similar distribution of main external pneumatic diverticula, with Brachiosaurus having much more subdivided diverticula. Due to the weight reduction achieved by these pneumatic diverticula, the neck of Brachiosaurus was up to 25 per cent lighter than without pneumatic structures, whereas that of Dicraeosaurus was only 6 per cent lighter. Pneumatization of the cervical vertebrae therefore can play an important role in lightening some sauropods. ZUSAMMENFASSUNGDie Präsacralwirbel sauropoder Dinosaurier waren von einem komplexen System pneumatischer Diverticula umgeben und ausgehöhlt. Die pneumatischen Diverticula entstammten wahrscheinlich einem paarigen cervicalen Luftsack, der mit dem Atemapparat verbunden war. Zur Darstellung der internen pneumatischen Strukturen wurden Halswirbel von Brachiosaurus brancai und Dicraeosaurus sp. der spätjurassischen (?Oxfordium-Kimmeridgium-Tithonium) Fundstelle Tendaguru aus dem östlichen Afrika mit Computertomographie untersucht. Die daraus resultierenden vergleichenden Rekonstruktionen der pneumatischen Diverticula im Halsbereich dieser Sauropoden-Taxa dienen dazu, die biomechanische Bedeutung pneumatischer Strukturen in den Wirbeln von Sauropoden besser zu verstehen. Interne pneumatische Strukturen bei Brachiosaurus brancai sind semicamellat mit wenigen großen Camerae in den Wirbelkörpern, welche von Camellae umgeben sind. Dicraeosarus zeigt hingegen ein procamerates Pneumatisierungsmuster ohne interne Pneumatisierung, bei dem wenige tiefe pneumatische Fossae bis zu einem breiten medianen Septum im Wirbel vordringen. ...