ORIGINS OF PLEXUS BRACHIAL IN Iguana iguana iguana ORIGENS DO PLEXO BRAQUIAL DA Iguana iguana iguana

Rozana Cristina ARANTES; Frederico Ozanam CARNEIRO E SILVA; Ana Kelen Felipe LIMA; Maria de Jesus Veloso SOARES; Hassen JERBI 1. Course of Veterinary Medicine of Veterinarian Medical College of Tocantins Federal University of Campus Araguaína, TO, Brazil. rozanacristina.arantes@gmail.com; 2. Course of Veterinary Medicine of Veterinarian Medical College, Federal University of Uberlândia, Uberlândia, MG, Brazil. 3. Ecole Vétérinaire Sidi Thabet, Tunisie


INTRODUCTION
There are 10,032 of reptiles species in world.In Brazil there were identified 760 species, belonging to 718 Squamata order, which includes snakes, lizards and amphisbaenians, 36 turtles and six alligators.Every year there are new species cataloged (SOUZA et al., 2013;BENÍCIO et al., 2015).They inhabit the most different and diverse environments, especially warm areas (SOUZA et al., 2013).
Iguana iguana iguana is a lizard of Iguanidae Family, and its body has spines along the back and tail looking like thorns, and also a large, round scaly under the eardrums and a gular fold well developed.The iguana displays varied colors, usually young ones have an vivid green color, while in adults, diversifies color and may have diffuse dark vertical stripes on the body and tail (ANDRADE, 2009).
In vertebrates, the ventral rami of spinal nerves, located in regions of deployments of forelimbs and adjacencies constitutes the nerves that form the brachial plexus.The spinal nerves are named according to position that they occupy in the spine.The first cervical spinal nerve, C1, emerges lateral vertebral foramen atlas', while the second spinal nerve, C2, emerges from the intervertebral foramen, located between the first cervical vertebrae, atlas, and the second cervical vertebrae, the axis (SCAVONE et al., 2008).
The knowledge about Nervous System of reptiles is deficient, requiring research with emphasis on descriptive anatomy, histological and pathological these animals.This research aimed to describe the origins of iguana brachial plexus in order to be a compilation of Nervous System of species, with application in clinical and surgery practice.

MATERIAL AND METHODS
The Wild Animal Screening Center and Independent Company Highway and Environmental of Military Police donated 12 dead iguanas, eight males and four females, from different ages and length ranging from 0.6 to 1.25 meters, to Veterinary Anatomy Laboratory of Federal University of Tocantins, situated at Araguaína of Tocantins State.
These animals were fixed in 10% formalin solution with intramuscular injections.Following that, a parallel incision to dorsal midline from skull to last rib was made, and all epiaxial muscles, eight ribs and periosteum were removed, exposing and individualizing the spinous processes for counting the vertebrae and identification of ventral rami of corresponding spinal nerves to the nerves that compose the brachial plexus.It was made a statistical analysis using the arithmetic average, schemed and photographed and the nomenclature is according to Baumel et al. (1993)

RESULTS
There are five iguanas with eight cervical vertebrae, 14 thoracic vertebrae, two sacral and a variable number of caudal vertebrae and seven iguanas with eight cervical vertebrae, 15 thoracic vertebrae, two sacral and various number of caudal vertebrae.The ventral rami of spinal nerves C6, C7, C8, T1 and T2 form the brachial plexus of 12 iguanas and exhibit symmetry between the antimeres, consisting: in 41.6% of cases by ventral rami of spinal nerves C6, C7, C8 and T1; in 33.4% of cases by ventral rami of spinal nerves C6, C7, C8, T1 and T2; in 16.6% of cases by ventral rami of spinal nerves C7, C8, T1 and T2; and in 8.4% of cases by ventral rami of spinal nerves C7, C8 and T1.There are formed three trunks: cranial trunk: the ventral rami of spinal nerve C7; medium trunk: the ventral rami of spinal nerve C8 and the caudal trunk: the ventral rami of spinal nerve T1.And when presents, the ventral rami of spinal nerves C6 and T2 consist of nervous fillet.
There are several anastomoses between the ventral rami of cervical spinal nerves and ventral rami of spinal thoracic nerves in the formation of nerves that innervate the forelimbs, as shown in Table 1.In Figure 1, schematic representation of origin and distribution of brachial plexus nerves in one Iguana iguana iguana.

DISCUSSION
The brachial plexus of these 12 iguanas comes from the ventral rami of last three cervical spinal nerves, C6, C7 and C8 and first two ventral rami of spinal thoracic nerves, T1 and T2.
The data relating to set of nerves that make up the brachial plexus facilitate access to procedures such as anesthetic block the forelimb, achieving maximum effectiveness of anesthetic agent, decreased surgical time and anesthetic dose.The scarcity of reports about the origin of brachial plexus in wild animals especially lizards, possibility of comparison to representatives of Reptila class, however, is not always reliable because of large diversity of group.
In origin of brachial plexus of iguana, compared to animals Reptila class, such as crocodiles and tortoises, there are contradictions since in crocodiles, the brachial plexus originates from ventral rami of spinal nerves 7, 8, 9, 10 and 11, which constitutes four nerve trunks and a nervous fillet (WYNEKEN, 2007;SUZUKI;HAYASHI, 2010) while in red-legged tortoises, the brachial plexus originates from ventral rami of spinal nerves 5, 6, 7, 8 and 9 (CARVALHO et al., 2011).It is expected the lack of consensus because despite belonging to the same class, have order, family and different genres, and these factors cause changes in the number of vertebrae and on-site implementation of thoracic member.
By relating the origin of brachial plexus of iguana comparing with lizards from Squamata order, there is consonance with species Uracentron azureum, Lacerda lépida, Xenosaurus grandis, Chalcides acellatus, Gekko gecko, Uroplatus fimbriatus, Tarentola annularis, Agama agama, Chalarodon madagascariensis and Sphenodon punctatus.In these species, the origin of brachial plexus corresponds to ventral branches spinal nerves 6, 7, 8, 9 and 10 (GREGORY; CAMP 1918;LÉCURU, 1968;RENOUS-LÉCURU, 1972).This correlation relates the presence of equal amounts of cervical vertebrae and consequently same site forelimb, however these species belong to different genera and families as a result of high variability, habitat interference, presence of food and predators.
However, there is unconformity related to the origin of the brachial plexus of iguana with other lizard species such as Chamaeleon verrucosus, Chamaeleon parsoni, Brookesia spectrum and Lanthanotus borneensis.In these lizards three ventral branches of the spinal nerves are the source of brachial plexus, though there is variation in location of these branches, the Lanthanotus, plexus originates in ventral branches of spinal nerves 7, 8 and 9 and Chamaeleon and Brookesia, brachial plexus corresponds to the ventral rami of spinal nerves 4, 5 and 6 (LÉCURU, 1968).This contradiction exemplifies the discrepancy in number of cervical vertebrae and the forelimb mounting location in axial skeleton.
In the current study, there is the presence of anastomoses in ventral rami of spinal nerves to form the axillary, subscapular, cutaneous, pectoral, coracobrachialis, radial, median, ulnar, thoracodorsal nerves, which are some of main nerves for thoracic limb.This characteristic is in agreement with findings of Renous-Lécuru (1972) who found variations in composition of nerves to the brachial plexus.This variability allows the survival of strains because conditions the maintenance of species to different individuals, making the changes and adaptations to habitat.
. The use of dead animals is consistent with Normative Instruction number154/2007 of IBAMA and Law No. 11,794 /  2008.

Table 1 .
Origins of main nerves that compose the brachial plexus in Iguana iguana iguana.