Anatomy of the brachial plexus in the Mongolian gerbil (Meriones unguiculatus Milne-Edwards, 1867)

Abstract

The Mongolian squirrel is a murine rodent widely used as an experimental model and kept as a pet. With respect to the significance of the brachial plexus, we aimed to describe the origin and the nerves that constitute it, providing new information about the neuroanatomy of this species. Twenty adult animals were used, which were fixed in a 10% formaldehyde solution at the Applied Animal Morphophysiology Laboratory of the Brazilian Federal University of the Semi-Arid Region (UFERSA). The animals were medially incised with an opening of the thoracic cavity, and then bilateral dissection was carried out. Once the nerves were identified, cotton wool soaked with a 2% hydrogen peroxide solution was added for bleaching and better visualisation of structures. The gerbil brachial plexus derived from ventral roots of the fourth, fifth, sixth, seventh and eighth cervical nerves (C<sub>4</sub>–C<sub>8</sub>) and the first thoracic root (T<sub>1</sub>). The suprascapular nerve was formed from the nerve roots C<sub>4</sub> and C<sub>5</sub>; the subscapular and cranial pectoral nerves from C<sub>5</sub> and C<sub>6</sub>; the musculocutaneous and axillary nerves from C<sub>5</sub>, C<sub>6</sub> and C<sub>7</sub>; and the caudal pectoral, radial, median, ulnar, thoracodorsal, lateral thoracic and long thoracic nerves from C<sub>7</sub>, C<sub>8</sub> and T<sub>1</sub>. This resembles what is described in other rodents, such as the rat and capybara. The gerbil has a pre-fixed plexus conformation.

The Structure of the Brachial Plexus in Selected Representatives of the Caniformia Suborder

“…The authors of the study conducted on animals of the Rodentia order, noted a wider range of branches included in the brachial plexus. For example, the range of the brachial plexus in representatives of the Muroidea superfamily, e.g., Mongolian gerbil ( Meriones unguiculatus ), is C4-T1 [ 4 ]. However, there was one case each where it was C6-T3, the Spix’s yellow-toothed cavy ( Galea spixi ), and C5-T1—the Gambian pouched rat ( Cricetomys gambianus ) [ 21 , 22 ].…”

“…The subclavian nerve was also listed in some studies on the brachial plexus of rodents [ 38 , 39 ]. However, it was not mentioned in studies on some felids and rodents [ 4 , 21 ]. These changes in nomenclature may have resulted from significant differences in the occurrence of collarbones among mammals.…”

“…These animals were obtained from breeders and hunters. The methodology that was used to fix and dissect the plexuses follows the pattern used by other researchers focusing on this topic [ 4 , 5 ].…”

“…As a result of scientific publications, the structure of the brachial plexus is characteristic of specific groups of animals [ 4 , 5 , 6 , 7 , 8 , 9 ]. Additionally, canids have characteristic variants of the range of the brachial plexus.…”

The Structure of the Brachial Plexus of the Djungarian Hamster (Phodopus sungorus)

“…The majority of brachial plexus related studies on Myodonta have been conducted on members of species belonging to the Muroidea superfamily. Species described from this group are, for example, the Mongolian gerbil ( Meriones unguiculatus ), mole-rats ( Spalax leucodon ), albino rat ( Mus norvegicus albinus ) (Araujo et al 2018 ; Aydin and Karan 2012 ; Greene 1963 ). Studies devoted to this family are particularly relevant due to the similarity of species from Myodonta to human.…”