Research in Veterinary Science 81 (2006) 165–169 www.elsevier.com/locate/rvsc
Computed tomographic anatomy of the head of the loggerhead sea turtle (Caretta caretta)
A. Arencibia a,*, M.A. Rivero a, I. De Miguel a, S. Contreras a, A. Cabrero b, J. Oro´s a
a Department of Morphology, Faculty of Veterinary Medicine, Las Palmas de Gran Canaria University, Trasmontan˜a 35416, Arucas, Las Palmas de Gran Canaria, Spain b Radiodiagnostic Service, Santa Catalina Clinic, Las Palmas de Gran Canaria, Spain
Accepted 3 December 2005
Abstract
The heads of three loggerhead sea turtles were disarticulated and imaged immediately to minimize postmortem changes and then fro- zen and sectioned. For computed tomography (CT) imaging, the heads were positioned in ventral recumbency. Transverse CT images with soft-tissue window were obtained from the olfactory sac region to the temporomandibular joint region. After CT imaging, the heads were sectioned and the gross sections were compared to CT images, to assist in the accurate identification of the anatomic structures. Different clinically relevant anatomic structures were identified and labelled in two series of photographs (CT images and anatomic cross-sections). CT images provided good differentiation between the bones and the soft tissues of the head. The information presented in this paper should serve as an initial reference to evaluate CT images of the head of the loggerhead sea turtle and to assist in the inter- pretation of lesions of this region. Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Computed tomography; Anatomy; Head; Sea turtle
1. Introduction lesions in the head due to boat strikes have been reported (Oro´s et al., 2005). Exudative salt gland adenitis is also fre- Two families and seven species of sea turtles are currently quently observed (Glazebrook and Campbell, 1990). recognized (Pritchard, 1997). All species of sea turtles are Esophageal lesions associated with ingestion of fishing included in the Red List of the World Conservation Union hooks (George, 1997; Oro´s et al., 2005) and crude oil are (IUCN/SSC, 2002). The IUCN emphasizes in its document also observed (Lutcavage et al., 1997). Ocular fibropapilo- entitled A Global Strategy for the Conservation of Marine mas (Brooks et al., 1994) and oral and esophageal fibromas Turtles (IUCN/SSC, 1995) the research on diseases of sea are common in several populations of sea turtles (Oro´s turtles from a multidisciplinary approach as a priority issue. et al., 1999). Many veterinary surgeons are involved in sea turtle conser- The introduction of X-ray computed tomography (CT) vation in wildlife rehabilitation hospitals around the world, has revolutionized the practice of diagnostic imaging. CT thereby contributing to improve the reptile’s medical man- has advanced significantly in veterinary medicine. In tur- agement. Several diseases involving the head of sea turtles tles, CT has been used in the diagnostics of metabolic bone have been described. Meningeal hemorrhages, meningitis, diseases (Raiti and Haramati, 1997), aural abscesses and spinal cord compression, associated with traumatic (McKlveen et al., 2000), and a nodal mass in the chest (Garland et al., 2002). However, there is no published material describing the cross-sectional anatomy of the log- * Corresponding author. Fax: +34 928451141. gerhead sea turtle (Caretta caretta) in terms of CT and E-mail address: [email protected] (A. Arencibia). macroscopic sections.
0034-5288/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.rvsc.2005.12.009 166 A. Arencibia et al. / Research in Veterinary Science 81 (2006) 165–169
The objective of this study was to describe the post-mor- section were compared to the corresponding gross ana- tem CT anatomy of the head of the normal loggerhead sea tomic sections. In addition, literature of sea turtle anatomy turtle (Caretta caretta) to optimize the diagnosis of head (Gaffney, 1972; Frick, 1996; Wyneken, 2001) and Nomina diseases. Anatomica Veterinaria (Schaller, 1992) were used to iden- tify the normal anatomy of the structures of the head. 2. Materials and methods 3. Results CT images of three normal subadult loggerhead sea tur- tles heads were selected. The turtles were euthanatized for Clinically relevant anatomic structures were identified medical reasons unrelated to diseases of the head. The and labeled in the two photographs presented in Figs. 1–6 heads were disarticulated at the level of atlanto-occipital (CT soft-tissue window and anatomic section). Detailed joint and were imaged immediately to minimize postmor- anatomy of the head was acquired with a CT soft-tissue win- tem changes. CT imaging was performed at the Radiodiag- dow. Thus, the bones of the skull (prefrontal, frontal, pari- nostic Service of the Santa Catalina Clinic of Las Palmas etal, postorbital, supraoccipital, squamosal, quadratojugal, de Gran Canaria using a third-generation CT equipment jugal, and maxilla), mandible (dentary, angular, surangular, (Toshiba 600 HQ). The images were obtained in sagittal and transverse planes using the following parameters: exposure time, 1.8 s; 120 kVp; mAs. 220; with 1.0 cm slice thickness. A soft-tissue window (WL, 465; WW, 1880) was used. After CT exploration, the heads were frozen, and then sectioned using an electric saw to correspond with the CT images. All sections were cleaned and photo- graphed. CT images that most closely matched each gross
Fig. 1. (A) Sagittal CT image and (B) gross section of the sea turtle head. 1 = prefrontal bone, 2 = olfactory tract and salt gland, 3 = frontal bone, 4 = cerebrum, 5 = parietal bone, 6 = optic lobe, 7 = supraoccipital bone, 8 = temporal muscle, 9 = cranial cavity, 10 = basioccipital bone, 11 = basi- Fig. 2. (A) Transverse CT and (B) gross section at the level of region of sphenoid bone, 12 = rectus ventralis and longus capitis muscles, 13 = naso- olfactory sac; cranial view. 1 = prefrontal bone, 2 = cartilage of nasal pharynx and oesophagus, 14 = trachea, 15 = pterygoid bone, 16 = glottis, septum, 3 = dorsal nasal concha sinus, 4 = ventral nasal concha sinus, 17 = soft palate, 18 = hard palate, 19 = tongue, 20 = dentary bone, 5 = vomer, 6 = oral cavity, 7 = meckelian groove, 8 = dentary bone, 21 = oral cavity, 22 = ramphotheca (maxilla), 23 = ramphotheca (premax- 9 = ramphotheca (dentary bone), 10 = ramphotheca (maxilla), 11 = pre- illar bone), 24 = premaxillar bone, 25 = maxilla, 26 = external nares, maxilla bone, 12 = ventral nasal concha, 13 = maxilla and 14 = dorsal 27 = olfactory sac and 28 = nasopharyngeal duct. nasal concha. A. Arencibia et al. / Research in Veterinary Science 81 (2006) 165–169 167
Fig. 3. (A) Transverse CT and (B) gross section at the level of Fig. 4. (A) Transverse CT and (B) gross section at the level of salt gland; nasopharyngeal duct; cranial view. 1 = cranial cavity, 2 = olfactory tract, cranial view. 1 = cranial cavity, 2 = salt gland, 3 = postorbital bone, 3 = frontal bone, 4 = prefrontal bone, 5 = orbit and left eye, 6 = eye 4 = left eye, 5 = orbit, 6 = soft palate, 7 = coronoid bone, 8 = nasophar- muscles, 7 = vomer, 8 = soft palate, 9 = left mandible, 10 = geniohyoi- ynx, 9 = angular bone, 10 = tongue, 11 = intermandibularis muscle, deus muscle, 11 = intermandibularis synchondrosis, 12 = tongue, 12 = geniohyoideus muscle, 13 = meckelian groove, 14 = prearticular 13 = nasopharyngeal duct, 14 = meckelian groove, 15 = oral cavity, bone, 15 = surangular bone, 16 = palatine bone, 17 = jugal bone, 16 = ramphotheca (maxilla), 17 = maxilla, 18 = inferior eyelid, 18 = vomer, 19 = interorbital septum, 20 = cerebrum and 21 = parietal 19 = scleral ossicles, 20 = superior eyelid, 21 = right eye, 22 = interorbital bone. septum and 23 = salt gland.
4. Discussion prearticular, splenial, and articular bones) and hyoid bones were easily identifiable because of the high CT density in CT imaging is a noninvasive cross-sectional diagnostic cortical bone appearing white and the intermediate CT den- technique that offers considerable advantages over tradi- sity in their medullary cavities. Cartilages of many bones tional radiography: a lack of superimposition of the tissues and articular sutures were clearly detected and appeared and a higher differentiation of tissue densities. The use of grey. Air-filled structures of the respiratory (nasal cavity, CT imaging in exotic animals medicine is currently limited glottis, and trachea) and digestive (oral cavity and esopha- because of the expense, availability, and logistic problems gus) systems gave negligible CT-tissue density and appeared of acquiring CT images in these animals (Raiti and Hara- black. Muscles, salt glands, eyes and associated structures mati, 1997; McKlveen et al., 2000; Garland et al., 2002). gave an intermediate CT density and appeared grey. The Diagnostics of diseases, such as traumas, neoplasms, nervous structures (myelencephalon, cerebellum, optic infections, inflammations and others involving the head lobes, olfactory bulb, and nerves) were clearly appreciated of loggerhead sea turtles can be improved using CT imag- in this modality CT window (Figs. 1, 3–6). ing. CT provided excellent details of clinically relevant 168 A. Arencibia et al. / Research in Veterinary Science 81 (2006) 165–169
Fig. 5. (A) Transverse CT and (B) gross section at the level of glottis; cranial view. 1 = parietal bone, 2 = cranial cavity, 3 = opisthotic bone, Fig. 6. (A) Transverse CT and (B) gross section at the level of 4 = postorbital bone, 5 = jugal bone, 6 = basisphenoid bone, 7 = meck- temporomandibular joint; cranial view. 1 = supraoccipital bone, 2 = sple- elian groove, 8 = nasopharynx, 9 = hyoid bone, 10 = glottis, 11 = inter- nius capitis muscle, 3 = exoccipital bone, 4 = quadrate bone, 5 = trans- mandibularis muscle, 12 = soft palate, 13 = pterygoid bone, versus cervicalis muscle, 6 = left squamosal bone, 7 = otic cavity, 14 = geniohyoideus muscle, 15 = angular bone, 16 = prearticular bone, 8 = quadratojugal bone, 9 = temporomandibular joint: articular disc, 17 = surangular bone, 18 = transversus cervicalis muscle, 19 = splenius 10 = surangular bone, 11 = articular bone, 12 = hyoid bones, 13 = cor- capitis muscle, 20 = myelencephalon and 21 = cerebellum. acohyoideus muscle, 14 = trachea, 15 = oesophagus, 16 = longus colli muscle, 17 = depressor mandibulae muscle, 18 = pterygoideus muscle, 19 = basioccipital bone, 20, auricular fat, 21 = blood vessels and cranial anatomy and correlated well with the corresponding gross nerves, 22 = right squamosal bone, 23 = spinal cord, 24 = spinal canal and 25 = parietal bone. specimens. In CT, the grey scale is directly related to the radiation attenuation of the head structures. In addition, With developing technology in the wildlife rehabilitation it provides excellent discrimination of soft tissues and min- hospitals, CT imaging may soon become more readily eralized tissues of the head (Fike et al., 1981; Kaufman available for exotic animals imaging. In the same way, it et al., 1981; Feeney et al., 1991; Smallwood et al., 2002). will be quite useful to be able to establish some reference In our study, both soft-tissue window and gross section set- points on the head of the loggerhead sea turtle, to scan only tings were compared in all images. The planimetric or sec- these selected parts during an experimental approach or to tional anatomy of the head in the loggerhead sea turtle assist in the interpretation of lesions of this region. allows a correct morphologic and topographic evaluation of the anatomic structures, which is a useful tool for the References identification of the CT images. Sagittal images were used to evaluate the midline structures of the head. The ana- Brooks, D.E., Ginn, P.E., Miller, T.R., Bramson, L., Jacobson, E.R., tomic relationships were appreciated most easily in the 1994. Ocular fibropapillomas of green turtles (Chelonia mydas). transverse planes. Veterinary Pathology 31, 335–339. A. Arencibia et al. / Research in Veterinary Science 81 (2006) 165–169 169
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