Modified neck muscular system of the giraffe (Giraffa camelopardalis)

Endo, Hirahito; Yamagiwa, Daishiro; Fujisawa, Masahiko; Kimura, Junko; Kurohmaru, Masamichi; Hayashi, Yoshihiro

doi:10.1016/s0940-9602(97)80055-6

Cited by 8 publications

(7 citation statements)

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“…Camelids, giraffids, equids, and some antilopin bovids are characterized by a well-developed nuchal ligament permitting the stabilization of a long neck (Mobarak and Fouad 1977;Dimery et al 1985;Bianchi 1988;Endo et al 1997;Gellman and Bertram 2002;Preuschoft and Klein 2013). This is permitted by the extension of passive bracing elements.…”

Section: Body Size and Neck Length In Mammalsmentioning

confidence: 99%

“…This is permitted by the extension of passive bracing elements. Camelids, giraffids, equids, and some antilopin bovids are characterized by a well-developed nuchal ligament permitting the stabilization of a long neck (Mobarak and Fouad 1977;Dimery et al 1985;Bianchi 1988;Endo et al 1997;Gellman and Bertram 2002;Preuschoft and Klein 2013). It is often associated with a coelongation of the limbs (Simmons and Altwegg 2010), which increases cursoriality while allowing the head to reach the ground.…”

Section: Body Size and Neck Length In Mammalsmentioning

confidence: 99%

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Differential scaling patterns of vertebrae and the evolution of neck length in mammals

2017

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Almost all mammals have seven vertebrae in their cervical spines. This consistency represents one of the most prominent examples of morphological stasis in vertebrae evolution. Hence, the requirements associated with evolutionary modifications of neck length have to be met with a fixed number of vertebrae. It has not been clear whether body size influences the overall length of the cervical spine and its inner organization (i.e., if the mammalian neck is subject to allometry). Here, we provide the first large-scale analysis of the scaling patterns of the cervical spine and its constituting cervical vertebrae. Our findings reveal that the opposite allometric scaling of C1 and C2-C7 accommodate the increase of neck bending moment with body size. The internal organization of the neck skeleton exhibits surprisingly uniformity in the vast majority of mammals. Deviations from this general pattern only occur under extreme loading regimes associated with particular functional and allometric demands. Our results indicate that the main source of variation in the mammalian neck stems from the disparity of overall cervical spine length. The mammalian neck reveals how evolutionary disparity manifests itself in a structure that is otherwise highly restricted by meristic constraints.

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Section: Body Size and Neck Length In Mammalsmentioning

confidence: 99%

Section: Body Size and Neck Length In Mammalsmentioning

confidence: 99%

Differential scaling patterns of vertebrae and the evolution of neck length in mammals

2017

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“…The origin of giraffe's iconic long neck and legs, which combine to elevate its stature to the tallest terrestrial animal, has intrigued mankind throughout recorded history and became a focal point of conflicting evolutionary theories proposed by Lamarck and Darwin. Giraffe's unique anatomy imposes considerable existential challenges and three systems bear the greatest burden: the cardiovascular system to maintain blood pressure homeostasis 1 , the musculoskeletal system to support a vertically elongated body mass 2 and the nervous system to rapidly relay signalling over long neural networks 3 4 . To pump blood vertically 2 m from the heart to the brain giraffe has evolved a turbocharged heart and twofold greater blood pressure than other mammals 1 5 .…”

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confidence: 99%

“…The blood vessel walls in the lower extremities are greatly thickened to withstand the increased hydrostatic pressure, and the venous and arterial systems are uniquely adapted to dampen the potentially catastrophic changes in blood pressure when giraffe quickly lowers its head to drink water 1 5 6 7 8 9 10 11 . To sustain the weight of the long neck and head, the nuchal ligament, which runs down the dorsal surface of the cervical vertebrae and attaches to the anterior thoracic vertebrae, is greatly enlarged and strengthened 2 12 .…”

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Giraffe genome sequence reveals clues to its unique morphology and physiology

et al. 2016

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The origins of giraffe's imposing stature and associated cardiovascular adaptations are unknown. Okapi, which lacks these unique features, is giraffe's closest relative and provides a useful comparison, to identify genetic variation underlying giraffe's long neck and cardiovascular system. The genomes of giraffe and okapi were sequenced, and through comparative analyses genes and pathways were identified that exhibit unique genetic changes and likely contribute to giraffe's unique features. Some of these genes are in the HOX, NOTCH and FGF signalling pathways, which regulate both skeletal and cardiovascular development, suggesting that giraffe's stature and cardiovascular adaptations evolved in parallel through changes in a small number of genes. Mitochondrial metabolism and volatile fatty acids transport genes are also evolutionarily diverged in giraffe and may be related to its unusual diet that includes toxic plants. Unexpectedly, substantial evolutionary changes have occurred in giraffe and okapi in double-strand break repair and centrosome functions.

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“…The nuchalsupraspinous ligament is extraordinarily developed in the thoracic region of the one-humped camel [3][4][5] in comparison with the horse and cow [2]. It has been thought that the nuchal-supraspinous ligament may bear the long neck weight and support the action of the head in the camel or the giraffe [1], however, we suggest that the nuchalsupraspinous ligament is a substantial attachment apparatus of the cranial hump in the two-humped camel.…”

Section: Discussionmentioning

confidence: 82%

Hump Attachment Structure of the Two-Humped Camel(Camelus bactrianus).

Endo

Cao

Borjihan

et al. 2000

The Journal of Veterinary Medical Science

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ABSTRACT. The hump attachment structure was morphologically examined in the two-humped camel (Camelus bactrianus). The cranial hump is fixed by the trapezius and rhomboid muscles in the thoracic region. The strong collagen sheet in the basement of the hump is attached to the segmented bellies of the trapezius muscle, and the thoracic rhomboid muscle and the nuchal-supraspinous ligament support the attachment function of the trapezius muscle. The basement sheet possesses the line structure of collagen fibers, which are fitted to the segmented bundles of the trapezius muscle, and we observed that the muscle cells of the trapezius muscle are intermingled with the collagen fibers around the attachment line structure. In contrast, the caudal hump is directly attached to the subcutaneous tissue in the superficial region of the lumbar longissimus and lumbar iliocostal muscles. These findings demonstrated that the caudal hump of the twohumped camel is consistent with the hump of the one-humped camel in the attachment structure. -KEY WORDS: hump, rhomboid muscle, trapezius muscle, two-humped camel.The hump structure of the camels has been examined in the dromedary [3,5]. It has been demonstrated that the characteristic hump is attached to the subcutaneous adipose tissue on the latissimus dorsi muscle and fixed on the dorsal part of the lumbar region. While, in the two-humped camel, the cranial hump is expected to be different from the caudal in its attachment structure, since the cranial hump is located on the thoracic region and near the nuchal-supraspinous ligament. So, we dissected the dorsal region of the trunk in the two-humped camel and morphologically examined the attachment mechanism of both cranial and caudal humps. MATERIALS AND METHODSWe obtained one male two-humped camel (Camelus bactrianus) from a livestock farm in Huhehot district in the Inner Mongolia of China. The animal was exsanguinated from the common carotid artery, and was euthanized. We separated the head and four limbs from the trunk, and set the trunk in horizontal plane, and removed the skin. The animal was dissected in the dorsal superficial area of the trunk, and the hump attachment structure was observed by naked eyes.The three skeletal specimens of the two-humped camel were examined in the vertebrae related to the attachment of humps. The skeletons have been stored in the Department of Veterinary Anatomy, Inner Mongolian Agricultural University, however, any biological data have not been recorded in the skeletons.The tissues were excised from the basement sheet of the cranial hump. The tissue blocks were fixed in 10% phosphate-buffered formalin. After 10 days of fixation, the tissues were dehydrated in ethanol, treated by xylene and embedded in paraffin. The blocks were sectioned at 4 µm, stained by haematoxylin and eosin, and observed with the light microscope. RESULTSThe cranial and caudal hump bodies consist of the white adipose and connective tissue, and show the sharp triangle in lateral aspect (Fig. 1). The former is located in the dors...

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Modified neck muscular system of the giraffe (Giraffa camelopardalis)

Cited by 8 publications

References 3 publications

Differential scaling patterns of vertebrae and the evolution of neck length in mammals

Differential scaling patterns of vertebrae and the evolution of neck length in mammals

Giraffe genome sequence reveals clues to its unique morphology and physiology

Hump Attachment Structure of the Two-Humped Camel(Camelus bactrianus).

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