X-Ray Radiological Study for Skeleton of Rounded Fantail Stingray Taeniura grabata from Susah, Libya

A sample of Round Fantail Stingray Taeniura grabata was brought, from Susah harbor in east Libya, to establish radiographically, it was situated Dorsal-ventrally, to diagnose skeleton and tooth plate, using Siemens X-ray System (Multix Fusion). In the Multi-graded radiograph, the specimen skeleton was so pale white in most of the axial skeleton and parts of the cranium, and poorly calcified. 88 pectoral radials: 41 propterygials, 15 mesopterygial

Anatomical studies of these species are essential to appreciating their biology, Enault et al. (2016) indicated that the skeleton of cartilaginous fishes is notoriously difficult to study, and the literature caping this subject is very rare compared to other vertebrates.The importance of skeletal specimens in research collections, using a few ways to study, which including radiographs.Especially the skeletal system and vertebral column; that plays an important mechanical role in movement of these fishes (Learm, 1976;Lindsey, 1978;and Weihs, 1989).Nowroozi and Brainerd, (2012) indicated that the vertebral column plays a dichotomous role during locomotion across vertebrate taxa, providing both the stiffness and flexibility required for locomotion (Symmons, 1979;Smeathers, 1981;Hurov, 1987;Gal, 1993;Schmitz, 1995;Long et al., 2011;Porter et al., 2009).To some extent, different mechanical properties in different regions of the vertebral column can meet the conflicting demands of stiffness and flexibility (White & Panjabi, 1978;and Panjabi et al., 2001).Ultimately, the structure of the individual vertebra and its interaction with the adjacent vertebra via the inter-vertebral joint (IVJ) determine the mechanics of not only individual segments but also across entire regions, and along the full length of the column as well (Smeathers, 1981;Hurov, 1987;Gal, 1993;Bond, 1996;Ward & Brainerd, 2007;Porter et al., 2009).The Vertebral column varies in regionalization degrees across vertebrates (Qasim, 1995;and Al-Shubka, 2009).These degrees can be revealed by biometrical studies (Kubo & Asano, 1987;1990;Desse et al., 1989).In batoid fishes, wing vessels are located between the ceratotrichia, which are cartilaginous raylike projections that make up the wings (Culpepper and Mylniczenko, 2017).Stepanek and Kriwet (2012) mentioned that the shape of the neuro-cranium (the skull) is related to functional aspects of the jaws and locomotion.It encloses the brain and the olfactory, auditory, and visual organs.The tesserae in the skull are functionally important in stiffening the parts of the cranium; such as jaws as adaptation to durophagy, when arranged in several layers; because of the high level of kineticism in fish skulls, and more than 20 movable skeletal elements in the pharyngeal apparatus in these skulls (Dean and Summers, 2006), the primary cranial skeletal elements couplings involved in feeding behavior are presented here.Westneat (2006) mentioned that batoids are characterized by a spectacular diversity of skull form and feeding mechanisms, from sit and wait predators that use high suction forces to engulf their prey species, even fishes; that get remove pieces of them to feed in a biting strategy.This pattern is the widespread use of suction during prey capture as a strategy to transport food into the mouth.Suction feeding is the most used mode to prey capture of bony fishes (Liem, 1980;Muller & Osse, 1984;Lauder, 1985;Alfaro et al., 2001;Ferry-Graham et al., 2003 andWestneat, 2006).Most batoids employ jaw protrusion and suction feeding; thus a current area of active research is focused on the mechanics and evolution of these behaviors, and how the suction profiles compare to those of other fishes.
This study aims to use X-ray graphs for the vertebral column, jaws, and teeth of the round fantail stingray; because there is no such information available in the literature for this species on the Libyan eastern coast, as well as, this study could be as a prelude to future anatomical studies of elasmobranches.

Radiograph Machine:
A radiograph of frozen specimen was made on Siemens X-ray System (Multix Fusion) (Figure 1.C).

Positioning:
It was in horizontal beam (Ventro-dorsal view), with sagittal section of whole (Summers, 2000;and Alhamroni, 2018 -personal meeting).2.3.3.Radiographic density: of the studied specimen in the radiograph-desk had an image, with different densities (black, dark grey, light grey, white, and so on) in the scale of contrast (Thrall et al., 2013).

Biometrically
A male Rounded stingray Taeniura grabata from Susah harbor, Libya, it was measured the total length, disk length, width and depth and Tail length as well as 770, 370, 40, 38, and 400 mm, respectively.

Radiographically
In Figure ( 2), talking about the calcified cartilages in the skeleton of study specimen was so pale white in most the axial skeleton and parts of the cranium, and poorly calcified, obscured in radiographs.According to denticles on overlying integument, there is multiplication in the mineralized tesserate layers in the jaws of this batiod, and it was analogous to cortical thickening (Summers, 2000).These tesserae are perichondrial in origin.In general, there is mineralized and un-mineralized tissue, and the response of the element to load is determined by both materials (Wroe et al., 2008;andLiu et al., 2010, 2014).These higher degrees of stiffness and differing Poisson's ratios were seen even though uniform cubes of bone were used for compression testing.The difference between axes of compression is due to the sub-structural properties of the bone, such as the orientation of the mineralized collagen fibril bundles (Weiner & Wagner, 1998;and Shahar et al., 2007).However, this issue has effect to investigate the elemental composition of vertebral bands, and by association, the factors that may influence their deposition, elemental distribution within vertebrae was assessed in five diverse species of sharks using Scanning X-ray Fluorescence (Raoult et al., 2016).

Pectoral and caudal radials count
In this work: Pectoral radials (88 in total): Propterygial radials, Mesopterygial radials and Metapterygial radials in count to 41, 15, and 32 units, respectively.As well as Pelvic radials (22) were counted in Taeniura grabata in this work, in general cartilaginous radials highly branched distally and extend to margins of pectoral fin (displacing ceratotrichia) (Compagno, 1999).As shown in  and Compagno (1993) in Dasyatis chrysonota.The pelvic radials in male are more than in females.The pectoral girdle is unique in batoids, with the scapulacoracoid either fusing together dorsally by means of the suprascapula or articulating directly to the synarcual (fused vertebra) by means of a ball-and-socket joint (Compagno, 1999).In T. grabata, the fin radials are attached to the scapulacoracoid via three enlarged basal radials (Figure 2), the same subject has been found in Taeniura lymma (Rosenberger and Westneat, 1999).The muscles of T. grabata are darker in coloration to approximately half-way to the fin margin, where the superficial muscles end (Figure 2).This coloration has not been documented in any other stingray species (Rosenberger and Westneat, 1999).Lying proximally on top of the dorsal superficial muscle are thick bands of tendons that run along the anteroposterior axis of the pectoral fin.The mesopterygium, (Mesopterygial radials) in most stingrays is a single element that articulates medially with the scapulocoracoid and laterally with pectoral-fin radials.The mesopterygium, in Gymnura and Myliobatis; consists of several distinct components that all articulate with the scapulocoracoid (Nishida, 1990).In this work it was counted to 15 in T. grabata (Table 1).A hypothesis for this character is based on the progressive fragmentation and appearance of the mesopterygium.In this work, caudal fins are absent in this species, matching for Heemstra & Smith (1980).The absence of cartilaginous fin-fold radials in some other stingrays is considered the derived state, out-group analysis of caudal radials reveal their presence or absence a plesiomorphic condition and thus be of little significance in defining groups (Lovejoy, 1996).

X-Ray Radiological Study for Skeleton of Rounded Fantail Stingray…………
Faculty of Marine Resources, Alasmarya Islamic University, Libya.

The vertebral count
In T. grabata; compare to De Carvalho and Ragno (2011).It was relatively high caudal vertebrae count, with a modal count of 130; In Dasyatis chrysonota, it was stated similar values, according to (Cowley and Compagno, 1993).As more details, about 80 Pre-sting vertebrae and 50 Post-sting vertebrae, with 62 for the pre-caudal vertebrae, they were counted in T. grabata of this study (Table 1 & Figure 2).Le Port et al. (2013) recorded higher insignificantly number (71 -88) Pre-sting diplospondylous vertebrae and less than 50 Post-sting vertebrae in Dasyatis brevicaudata.This to prove the significant higher variation in Dasyatids.
In the study specimen, there was 60 diplospondylous vertebrae (in front or behind the pelvic girdle), they were less than De Carvalho and Ragno (2011) recorded in the species of freshwater stingray.This greater extension does not have direct influence on the number of total vertebrae (Tables 2), but is associated to the presence of a longer cartilaginous rod which supports the distal part of tail posterior to vertebral centra (individual centra do not occur posterior to caudal stings).Generally, Officer et al. (1996) stated that location in the vertebral column in species can have a statistically significant effect on increment counts.

Teeth rows count
In the specimen of T. grabata by presenting the following characters (Table 2): adult specimen with numerous tooth rows, ranging from about 32 upper tooth rows and 36 lower tooth rows (Figure 2).These teeth were small, blunt, and arranged into flattened surfaces, not rounded or oval in section as Underwood et al. (2016) described the typical shape of teeth for the nonsqualiformes.Round ribbontail ray Taeniura meyeni has much fewer of tooth rows till 46 in the upper jaw and to 45 in the lower jaw.De Carvalho and Ragno (2011) indicated to higher counts (40 -64) in freshwater species.

Neurocranium
Which locates dorsally in most stingrays, is rectangular broadening anteriorly because of the large nasal capsules in T. grabata as a box-like lateral view, with horizontal base (Figure 2).Stepanek and Kriwet (2012) mentioned that fresh-water stingrays lack a rostral cartilage.In our round fantail stingray, a dorsal-ventrally position, neurocranium is slightly elongate, longer than 1.5 times of width, it is wider at postorbital processes and nasal capsules (Figure 2).In Dasyatis violacea, as pelagic stingray, nasal capsules and rest of the neurocranium were formed an angle, whereas the non-pelagic stingrays had the nasal capsules and the rest of the neurocranium are in the same plane.Nasal capsules are relatively large, oval, broadly rounded slightly toward midline; its length posterior to postorbital processes about 30% of neurocranial desk length (Figure 2).Meckel's cartilage in this specimen is stout, dorsally projecting lateral process low and broadly triangular, not slender and elongate.Angular cartilage is less straight, slightly thicker closer to Meckel' cartilage (De Carvalho and Ragno, 2011).The examined specimen has the same character; other studies showed nasal capsules ventro-laterally, that shape is difficult to identify (Miyake, 1988;and Lovejoy, 1996).Looking to the mandibular arch and hyomandibulae; the wing-shaped mandibular process in the examined specimen, which is close to be attached between mandibular arch and angular overlap both jaws, which are also overlapped well in Dasyatis Spp. and Himantura Spp.(Lovejoy, 1996).Also, jaws are very robust and smaller than those of other stingrays (Figure 2).The mandibular symphysis and the hyomandibular symphysis are entirely fused (Summers, 2000).The wing-shaped gill rays were 10 at the epibranchials.

The bronchial skeleton
Which is part of the viscerocranium, comprises five arches in T. grabata (Figure 2).The ventral bronchial skeleton consists of an enlarged central medial plate, which resulted from the fusion of the basibronchial copula and the basibronchial components (De Carvalho et al., 2004), a short and transversely directed basihyal, a pair of short and anteriorly directed hypobronchials, and five pairs of ceratobronchials.Duncan et al. (2015) indicated to the gills are a multifunctional organ involved in gas exchange, acid-base, and ion regulation; where the structure and dimensions of gills of the potamotrygonid are important to assess their function.Gill measurements include gill filament's length and abundance, number of respiratory lamellae on the filaments, surface area of lamellar bilateral, total gill surface area, mass-specific gill area, and the water-blood diffusion barrier, are species-specific as reported from Hughes et al. (1986).In addition, some respiratory factors; such as the anatomical diffusion and diffusing coefficient, are obtained from these measurements, and may reflect the gills' performance under specific environmental conditions (Perry, 1990).
In the examined T. grabata; a single small bridge projects ventrally from the medial plate (Figure 2).According to Lovejoy (1996), this bridge forms a shelter for the aorta and afferent bronchial vessels.Such projections also are present in Plesiobatis, Hexatrygon, Urobatis, Urotrygon, Urolophus, and Gymnura, but are absent in some potamotrygonids and some other stingrays; such as Dasyatis spp.and pelagic Myliobatis spp.

The tessellated cartilage (Jaws and Teeth)
To describe it in a typical batoid jaw, as exemplified by a rounded fantail stingray: Two thick, parallel-fibered ligaments limit the relative mobility of the upper and lower jaws to just a little portion of freedom; as a block of that size would not fit between the jaws for an open mouth radiograph.The upper and lower jaws' left and right sides are not firmly connected, meanwhile teeth are tiny and sharply pointed.
A radiograph of a stingray Dasyatis sabina elaborated an independent motion in sides of the jaws during prey processing (Summers, 2000).However, it is not suited to exerting the large forces needed for crushing hard prey.Nishida (1990) mentioned Myliobatid stingrays are particularly interesting clade of pelagic stingrays; to examine the evolution of morphological novelties related with eating hard prey.
Talking about crushing prey; in batoids (propterygia) the skeletal element associated with the pelvic girdle, has tessellated cartilage, and is used to punt or to push off of the sea floor with the appendages (Dean &Summers, 2006, andMacesic &Summers, 2012); with more

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ISSN (Print): 2413-5267 ISSN (Online): 2706-9966 stiffness with higher mineralization levels, and greater stiffness in the propterygia cartilages of benthic species that punt.This hyper-mineralization strategy is reminiscent of the thick outer layers, and even trabeculation of the jaw cartilages in hard prey crushing elasmobranches (Summers, 2000;and Summers et al., 2004).
The dentition is set in an elastic ligament that may absorb energy as the tooth plates, relatively to one another during crushing.To amplify the force of the jaw adductors; the fused mandibular and palatequadrate symphyses, and the reduced mobility of the upper and lower jaw relative to each other, are combined.Summers (2000) suggested the "nutcracker" to clarify morphology and function of the jaw of stingrays, with muscle acting at a large force advantage.In a lever system; force advantage occurs when the input lever arm is longer than the output lever arm (Withers, 1992).The nutcracker model could be tested directly, by measuring force production in live animals, with simultaneous confirmation that the jaw adductors are firing asynchronously.Its difficulties are associated with eliciting a natural behavior like feeding under experimental conditions as stated by (Liem, 1976;and Motta et al., 1991).There are dietary records on the hard prey specialists, including an eagle ray crushed a clam, that weighed about 1360 g according to Coles (1910) and Summers (2000).This shows the complex architecture of the adductors, including at least six separate slips of muscle, would make the computation of effective cross-sectional area difficult.

Conclusion
This study is considered a first step to elucidate the skeleton anatomy of stingrays in general and to assemble reliable anatomical characters for inferring relationships and evolutionary aspects of this highly interesting group, motivating for more chondrichthyan skeletal specimens, especially the rare species, in more extensive biological studies of these species and other cartilaginous fishes in the Libyan coast.
Radiological Study for Skeleton of Rounded Fantail Stingray…………Faculty of Marine Resources, Alasmarya Islamic University, Libya.

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-Ray Radiological Study for Skeleton of Rounded Fantail Stingray………… Faculty of Marine Resources, Alasmarya Islamic University, Libya.

Table 1 .
Radiographic characters in skeleton of male Rounded Stingray Taeniura grabata, from Susah Harbor.