The Reptilian Renal Portal System - A Review

Transcription

1 R e v i e w A r t i c l e The Reptilian Renal Portal System - A Review Peter H. Holz, BVSc, DVSc, MACVSc, DACZM Healesville Sanctuary, PO Box 248, Healesville, Victoria 3777 Australia A bstract : The anatomy of the reptilian renal portal system is reviewed. Its structure is fundamentally similar in all species examined. The renal portal system functions to provide blood to tubule cells during periods of dehydration to prevent them undergoing ischaemic necrosis. Blood flows from the tail and hindlimbs through the kidneys and then on to the heart. However, anastomoses exist capable of shunting blood around the kid neys to the liver. Current data suggests that the renal portal system does not affect drug kinetics. K ey w o rds: renal portal system, squamata, rhyncocephalia, crocodilia, testudines, extremitatenanastomose INTRODUCTION A renal portal system is present in most fish and all amphibians, reptiles and birds. It is absent in mammals, except embryologically (Dantzler, 1985). The anatomy of the reptilian renal portal system has been described for a number of different species. Although it is fundamentally similar among the various groups of reptiles, some differences do exist. In general, blood flows from the tail by the caudal vein and from the limbs, where present, by the iliac or femoral veins. These vessels connect to the afferent renal portal veins which convey blood into the kidneys. Once the blood has fil tered through the kidneys, it emerges in the efferent renal portal veins and flows to the heart via the post caval vein. The literature describing the anatomy of the renal portal system is quite confusing, since various authors have given different names to the same vessel, making interpretation somewhat challenging. In many instances, only scientific names were used for the species described. Common names could not always be determined and so are missing in some instances. Those that are used are based on common current taxonomy. ANATOMY Order Squamata Suborder Sauria The renal portal system of lizards has been described by a number of authors (Jourdain, 1859, Hochstetter, 1893, Beddard, 1904, Beddard, 1905, Beddard, 1906a, Zarnik, 1910, Thapar, 1921, Spanner, 1925, Spanner, 1929, NawThan-Kyaing, 1968, Splechtna, 1970, Duda, 1972) and is anatomically similar among species (Figure 1). A single caudal vein drains the tail region and bifurcates to form two afferent renal portal veins. These vessels continue along the ventral surface of the kidneys, sending branches into the parenchyma. The exception to this occurs in the Moorish gecko, Tarentola mauritanica, where the afferent renal portal veins enter the kidneys on their lateral aspect (Zarnik, 1910). The common iliac veins are formed by the fusion of the internal and external iliac (which is an extension of the 4 Bulletin of the Association of Reptilian and Amphibian Veterinarians femoral) veins, and thus serve to drain the hind limbs. They connect with the afferent renal portal vein on each side, approximately two thirds of the way caudal to the cranial pole of the kidney, via an anastomosis (termed the extremitate nanastomose by Spanner, 1929). Exceptions to this are seen in the spiny-tailed agamid, Uromastix spinipes, and the Eastern water dragon, Physignathus lesueurii, where the com mon iliac veins penetrate the kidneys in their cranial third (Hochstetter, 1893, Splechtna, 1970), and in Varanus griseus, the Gila monster, Heloderma suspectum, and the whitethroated monitor, Varanus albigularis, where the common iliac veins connect to the afferent renal portal veins caudal to the kidneys (Hochstetter, 1893, Beddard, 1906a, Spanner, 1929). In all species examined the common iliac veins form the pelvic veins anteriorly. The pelvic veins receive branches from the parietal veins (draining the area dorsal to the kidneys), lateral parietal veins (which drain the lateral abdominal musculature), hypogastric veins (draining the bladder) and adipose veins (which collect blood from the fat body). The pubic vein drains the muscula ture ventral to the pubis. The two pelvic veins and the single pubic vein unite in the midline to form a single abdominal vein. This vessel runs anteriorly to empty into the liver. In the Nile monitor, Varanus niloticus, following fusion, the abdom inal vein splits and then reunites before entering the liver (Beddard, 1906a). In Green Iguana Iguana i. rhinolopha and the common blue-tongued skink, Tiliqua scincoides, lateral abdominal veins arise from the femoral veins. They course cranially towards the lungs, bypassing the liver and kidneys. These ves sels are also present in the desert monitor, Varanus griseus, but arise near the adrenals, instead of from the femoral vein (Beddard, 1904). In the European glass lizard, Ophisaurus apodus, the lateral abdominal veins arise from the abdominal vein as no femoral veins are present (Beddard, 1905). After perfuming the nephrons, blood leaves each kidney through an efferent renal portal vein. These vessels connect anteriorly via a transverse anastomosis, just caudal to the gonads. The resulting vessel is known as the post caval vein. This vein continues cranially and drains into the heart. In the slow worm, Anguis fragilis, viviparous lizard, Lacerta vivipara, and rock lizard, Agama tuberculata, a pos Volume 9, No. 1,1999

2 Figure 1. Renal portal system of the Order Squamata, Suborder Sauria (dor sal view). Arrows indicate direction of blood flow. The oval, stippled organs represent the kidneys. EA = Extremitatenanastomose. 1 = Connection of lymph heart directly to extremitatenanastomose, found in the viviparous lizard. 2 = Connection of lymph heart to pelvic vein, found in the slow worm and white-throated monitor. 3 = Connection of lymph heart to iliac vein, found in the bearded lizard and common chameleon. 4 = Mesenteric vein, found in the common chameleon and wall gecko. 5 = Lateral abdominal vein, found in Iguana i.rhinolopha and the common blue-tongued skink. terior anastomosis is also present, connecting the two efferent renal portal veins at the anterior part of the kidney (Spanner, 1925, Spanner, 1929, Duda, 1972). Varanus griseus possesses a similar anastomosis connecting the efferent renal portal veins, but this is situated at the posterior end of the kidney (Hochstetter, 1893). In the Indian bloodsucker, Calotes mystaceus, bearded dragon, Pogona barbata, brown water dragon, three-horned chameleon, Chamaeleo jacksoni, Fischer s chameleon, Chamaeleo fischeri, and short-homed chameleon, Calumma brevicornis, the efferent renal portal vein begins as a single vein, collecting blood from both kid neys via sm aller tributaries which divides into two Volume 9, No. 1,1999 (Naw-Than-Kyaing, 1968, Splechtna, 1970). In the panther chameleon, Furcifer pardalis, the left efferent renal portal vein starts as a vessel receiving blood from both kidneys. As it passes cranially, it deviates to the left and follows a course adjacent to the left kidney. The right efferent renal portal vein drains the cranial portion of the right kidney. The two efferent renal portal veins fuse at the cranial end of the kidneys and the resultant single post caval vein continues to the heart (Splechtna, 1970). The homed lizard, Phrynosoma aculeatum, viviparous lizard and Agama tuberculate are noted to have a larger right efferent renal portal vein (Hochstetter, 1893, Spanner, 1929, Duda, 1972) whereas Zamik, (1910), in his study of the sand lizard, Lacerta agilis, found the left to be larger. Splechtna, (1970) found that the bearded lizard possesses a larger right afferent renal portal vein, plus an anastomosis that permits blood to flow from the right kidney to the left. Vertebral veins deliver blood to the cranial pole of each kidney. In some instances blood from the vertebrae also reaches the kidney through connections with the caudal vein or the extremitatenanastomose. The common chameleon, Chamaeleo chamaeleon, pos sesses small anastomoses connecting each afferent renal portal vein with the mesenteric vein. This feature is very prominent in the Moorish gecko (Hochstetter, 1893, Spanner, 1929). The mesenteric vein becomes the hepatic portal vein and empties into the abdominal vein before it reaches the liver. In the Bengal monitor, Varanus bengalensis, Thapar (1921) described a vessel arising from each femoral vein. These two vessels fuse to form the ischio-mesenteric vein, which becomes part of the hepatic portal vein. The kidneys of the European glass lizard each receive six veins from the body wall. Three of these empty into the affer ent renal portal vein, while the other three empty directly into the kidneys (Beddard, 1905). Several authors have noted the existence of two lymph hearts, one on each side of the body. These are contractile structures consisting of connective tissue and striated muscle, and lined by endothelium (Ottaviani and Tazzi, 1977). In the viviparous lizard, the lymph hearts pump lymph into the extremitatenanastomose (Spanner, 1929), and in the bearded dragon they pump it into the iliac veins (Splechtna, 1970) and thence to the afferent renal portal veins. However, an anasto mosis exists which can allow the lymph to bypass the afferent renal portal veins by entering the abdominal vein. In the com mon chameleon, no such anastomosis exists and all lymph enters the afferent renal portal veins (Spanner, 1929). In the slow worm and white-throated monitor, the lymph is pumped into the abdominal vein and bypasses the renal portal system altogether (Spanner, 1929). Suborder Serpentes The renal portal system of snakes is described by Beddard, (1906b) for the yellow anaconda, Eunectes notaeus, anaconda, Eunectes murinus, African rock python, Python sebae, Coral Pipe snake Anilius scytale and rhinoceros viper, Bulletin o f the Association o f Reptilian and Amphibian Veterinarians 5

3 dal to its insertion in the kidney. These two veins unite cranially. The resulting vessel continues ventrally to the gut, where it is known as the mesenteric vein, and will eventually become the hepatic portal vein (as described in the common chameleon and the wall gecko). The abdominal vein is present and has its origin in the fat body. In the common grass snake, Tropidonotus natrix, it receives only minor tributaries from the afferent renal portal veins and empties into the hepatic portal vein (Hochstetter, 1893, O Donoghue, 1912). However, in the yellow anaconda it receives a major branch only from the left afferent renal portal vein (Beddard, 1906b). In the African rock python, a branch arises from each afferent renal portal vein (Beddard, 1906b). According to Spanner, (1929), the abdominal vein of the Indian rock python originates from branches off each extrem itatenanastomose before it enters the kidney. As there are no hindlimbs in snakes, and consequently no iliac veins, the extremitatenanastomosen function only to collect lymph from the two lymph hearts. According to Spanner, (1929) the extremitatenanastomose is absent in the grass snake. Therefore, the lymph hearts connect directly to the afferent renal portal veins shortly after their origin from the caudal vein. O Donoghue, (1912) describes pelvic veins in the grass snake, while Saunders and Manton, (1969) state that they are absent in this species. There are two efferent renal portal veins which unite to form the post caval vein. Order Rhynchocephalia The tuatara, Sphenodon punctatus, follows the funda mental lizard pattern, with a few minor variations. There is no direct connection between the iliac veins and the abdomi nal vein. Therefore, all blood from the hindlimbs and tail must enter the kidneys. However, Beddard, (1905) postulated that a connection to the abdominal vein may exist within the body of the kidneys. Also the right efferenfrenal portal vein is larger than the left (Beddard, 1905). Figure 2. Renal portal system of the Order Squamata, Suborder Serpentes (dorsal view). Arrows indicate direction of blood flow. The oval, stippled organs represent the kidneys. EA = Extremitatenanastomose. 1 = Origin of the abdominal vein from the afferent renal portal vein, found in the African rock python. 2 = Origin of the abdominal vein from the extremitatenanastomose, found in the Indian python. Bitis nasicomis, and by Zamik, (1910) for the boa constric tor, Boa constrictor, and smooth snake, Coronella austriaca by Spanner (1929) for the Indian python, Python molurus and by Hochstetter, (1893), O Donoghue, (1912), Spanner, (1929) and Saunders and Manton (1969) for the grass snake, Natrix natrix. Beddard, (1906b) described a vascular anatomy in snakes similar to that of lizards (Figure 2). In the yellow ana conda, the afferent renal portal veins receive drainage from a caudal vein and a number of vertebral and parietal veins, which collect blood from the spine and abdominal muscula ture. The right afferent renal portal vein is considerably smaller than the left. Hochstetter, (1893) and O Donoghue, (1912) described a large vein arising from each afferent renal portal vein cau 6 Bulletin of the Association of Reptilian and Amphibian Veterinarians Order Crocodylia The crocodilian renal portal system has been described by Rathke, (1866), Hochstetter, (1893), Beddard, (1906b), Zamik, (1910), Spanner, (1929) and Splechtna, (1970), and generally appears similar to that already described for the lizards. In the Nile crocodile, Crocodylus niloticus, the iliac veins (called ischiatic veins by Rathke, 1866) enter the cau dal vein. There is no extremitatenanastomose. The iliac veins in the American alligator, Alligator mississippiensis, are sim ilar to those found in lizards, and enter the afferent renal portal veins (called renal advehent veins by Rathke, 1866 and Hochstetter, 1893) via the extremitatenanastomose, into which the lymph hearts pump lymph. Rathke, (1866) also describes crural and obturator veins, both of which enter the renal advehent veins. Prior to its entry into the kidney, each renal advehent vein (sensu Rathke, 1866) gives off a vessel which proceeds to the oviduct or vas deferens. Upon reaching the kidney, the renal advehent veins (sensu Rathke, 1866) divide into two vessels. One branch flows along the dorsal aspect of the kid ney and the other along the ventral aspect. Volume 9, No. 1,1999

4 Figure 3. Renal portal system of the Order Testudines (dorsal view). Arrows indicate direction of blood flow. The oval, stippled organs represent the kid neys. EA = Extremitatenanastomose. A = Name given to vessel by Ashley, (1955). B = Name given to vessel by Bojanus, (1819). S = Name given to ves sel by Spanner, (1929). Two abdominal veins are present (called internal epigas tric veins by Rathke 1866), originating from the iliac veins. They are connected by a transverse anastom osis in Crocodylus spp. which is absent in the American alligator and the African dwarf crocodile, Osteolaemus tetraspis (Beddard, 1906b). These vessels course cranially to the liver and collect blood from the hepatic portal vein. In the Cuban crocodile, Crocodylus rhombifer, the left vessel is only about half the size of the right, whereas in the dwarf caiman, Paleosuchus palpebrosus, both vessels are of equal size (Rathke, 1866). As in the Moorish gecko, the afferent renal portal veins connect to a prominent mesenteric vein (Spanner, 1929). Order Testudines (Chelonia) The general chelonian system of venous drainage from the caudal body varies somewhat from that described previ ously (Figure 3), and has been detailed by Perschmann, (1956) and Zwart, (1963) for the Greek tortoise, Testudo hervolume 9, No. 1,1999 manni, by Bojanus, (1819) and Spanner, (1929) for the European pond turtle, Emys orbicularis, by Jourdain, (1859), Zarnik (1910) and Spanner, (1929) for the spur-thighed Mediterranean tortoise, Testudo graeca, by Zarnik, (1910) for the European pond turtle, Emys orbicularis, by De Ryke, (1926) and Ashley, (1955) for the Western painted turtle, Chrysemys picta belli, by De Ryke, (1926) for the snapping turtle, Chelydra serpentina, and by Holz, et al, (1997) for the red-eared slider, Trachemys scripta elegans. According to Bojanus, (1819), Spanner, (1929) and Holz, et al, (1997) there is no actual caudal vein. Instead, a network of smaller vessels (coccygeal, lateral coccygeal and cloacae veins) drain the tail and surrounding areas. However, Ashley, (1955) describes two distinct caudal veins in the painted turtle. These veins empty into the ischiatic veins. The vessels described by Bojanus, (1819), Spanner, (1929) and Holz, et al, (1997) empty into two analogous veins, which they term circumflex iliac veins. In all cases, the circumflex iliac veins (sensu Bojanus, 1819) or ischiatic veins (sensu Ashley, 1955) bifurcate. One branch enters the afferent renal portal vein running along the ventral surface of each kidney. This is called the iliac vein by Bojanus, (1819), or the extremitatenanastomose by Spanner, (1929), and continues to be called the ischiatic vein by Ashley, (1955). The other branch moves ventrally and becomes the umbilical vein (Bojanus, 1819), or abdominal vein (Spanner, 1929, Ashley, 1955) and continues to the liver. The segment of this vein located between the ischiatic vein (sensu Ashley, 1955) and the junction with the femoral vein is termed the iliac vein by Ashley, (1955). Neither Bojanus, (1819) nor Spanner, (1929) consider this a separate vessel, and call it the umbilical vein (Bojanus, 1819) or abdominal vein (Spanner, 1929) as soon as the circumflex iliac vein bifurcates. Bojanus, (1819) and Spanner, (1929) both describe an ischiatic vein. This is different from the one mentioned by Ashley, (1955) and arises from the hindleg. It connects to the circumflex iliac vein caudal to its bifurcation. This vein is not described by Ashley, (1955) in the painted turtle. Bojanus, (1819) mentions an unnamed vein emerging from each hindleg, which Ashley, (1955) calls the femoral vein in the painted turtle. The ischiatic veins (sensu Bojanus, 1819) have their origin in these vessels, which course cranial ly and link up with the umbilical veins (sensu Bojanus, 1819). Spanner, (1929) does not mention a femoral vein. Cranial to the femoral veins lie the smaller crural veins which join the umbilical veins (sensu Bojanus, 1819), or abdominal veins (sensu Ashley, 1955) anterior to the femoral veins. The hypogastric veins, (the posterior renal advehent veins of De Ryke, 1926, Perschmann, 1956, Zwart, 1963) collect blood from the penis, oviduct, rectum, cloaca and bladder and enter the caudal pole of the kidneys. These ves sels continue along the ventral surface of the kidneys as the afferent renal portal veins. Two abdominal veins (or umbilical veins, Bojanus, 1819) are present in chelonians. In all species, they are con nected by a transverse anastomosis and penetrate the liver. A vertebral vein (the anterior renal advehent vein of De Ryke, 1926, Perschmann, 1956, Zwart, 1963) penetrates the cranial pole of each kidney and joins to the afferent renal por tal veins, as they course along the underside of the kidneys. Bulletin of the Association of Reptilian and Amphibian Veterinarians 7

5 In all cases, the post caval vein receives a variable num ber of efferent renal portal veins from both kidneys. This large vessel then runs along the midline, dorsal to the liver, to the heart. In the painted turtle, three efferent renal portal veins arise from the left kidney and two from the right (Ashley, 1955). The converse occurs in the red-eared slider (Holz, et al, 1997). In the snapping turtle two vessels arise from the left and only one from the right (De Ryke, 1926). Spanner, (1929) is the only author who mentions the existence of lymph hearts in chelonians. They appear to pump lymph into the circumflex iliac veins before they bifurcate. De Ryke, (1926) and Holz, et al, (1997) produced casts of the renal portal vessels of the painted turtle, snapping turtle and red-eared slider. These studies demonstrated several direct connections between the afferent renal portal veins and the efferent renal portal veins in the snapping turtle and red eared slider, which were absent in the painted turtle. RENAL PORTAL BLOOD FLOW IN REPTILES From a review of the anatomy of the renal portal system in reptiles, it is apparent that in all species blood returning to the heart from the caudal part of the body may bypass the kidneys. In the majority of cases this can occur through the abdominal vein. However, even in those species where the abdominal vein fails to connect with the renal portal system, for example in the grass snake, an alternative route through the mesenteric vein is available (O Donoghue, 1912). As well, within the kidneys, direct connections between the afferent and efferent renal portal veins may permit blood to bypass the nephrons (De Ryke, 1926, Holz, et al, 1997). There are two published studies (Spanner, 1929, Holz, et al, 1997) which examine blood flow through the reptilian renal portal system. The study by Spanner (1929) observed the flow of blood directly in the living European turtle, and found that the blood was partitioned evenly into the abdomi nal veins and the extrem itatenanastom osen w here the circumflex iliac veins bifurcate. Holz, et al, (1997) traced the path of a radiopaque dye injected into the femoral and dorsal coccygeal veins and found that the dye in the femoral vein bypassed the kidneys and flowed to the liver. The path of the dye injected into the dorsal coccygeal vein was variable, flowing through the kidneys in two animals but bypassing the kidneys in two others. There are no data available concerning possible control of blood flow through or around the kidneys in reptiles. In birds, a valve which governs the flow of blood through the renal portal system is present within each external iliac vein at its confluence with the renal vein (Akester, 1964, Akester, 1967, Oelofsen, 1977). When the valve opens, blood bypasses the kidneys, and when it closes blood flows through the kid neys. In isolated preparations, the valve opened in response to adrenaline and closed in response to acetylcholine (Rennick and Gandia, 1954, Gilbert, 1961, Akester and Mann, 1969). This was also demonstrated to occur in vivo (Oelofsen, 1973). Holz, et al, (1997) found a possible valve in the abdominal Association of Reptilian and Amphibian Veterinarians vein of red-eared sliders. The likelihood of its existence is strengthened by the observation that blood in the dorsal coc cygeal vein can follow two different routes (Holz, et al, 1997). The implications of these findings are that drugs injected in the hindlimbs are not excreted prematurely by the kidneys, as has been stated by some authors (Mader, 1991, Pokras, et al, 1992). Recent work has shown that injection site has no significant effect on the pharmacokinetics of gentamicin in the eastern box turtle, Terrapene Carolina (Beck, et al, 1995) or on the pharmacokinetics of gentamicin or carbenicillin in the red-eared slider (Holz, et al, 1997b). These findings ren der the caudal region of the reptilian body available for the injection of therapeutics. FUNCTION OF THE RENAL PORTAL SYSTEM IN REPTILES The veins of the reptilian renal portal system drain into capillaries which provide blood to the proximal and distal convoluted tubules of the nephrons. They do not perfuse the glomeruli (Perschmann, 1956). As in mammals, the glomeru lar capillary tufts receive blood from the afferent arterioles. Following filtration, this blood leaves the glomeruli via the efferent arterioles, which then ramify to capillaries perfuming the renal tubules. The arterial and renal portal blood mixes at this point, before the capillaries combine into venules which eventually form the efferent renal portal veins and drain into the post caval vein. The function of the renal portal system has been described by Dantzler, (1985). Fish, amphibians and reptiles cannot produce a hypertonic urine, as' they lack a loop of Henle. Therefore, to decrease water loss, glomerular filtration rate must decrease. This is accomplished through the action of arginine vasotocin, which causes constriction of the affer ent glomerular arteriole (Forster, 1942, Sawyer, 1951, LeBrie and Sutherland, 1962, Braun, 1976). Consequently, blood flow through the glomerulus ceases. The renal portal system then continues to supply blood to tubule cells and prevents ischaemic necrosis. In piscine species such as the lamprey which do not prac tice glomerular intermittency, a renal portal system is absent (Dantzler, 1985). In birds, the reptilian-type nephrons cease glomerular filtration during dehydration, while the mam malian-type nephrons continue (Braun, 1976). However, because of the presence of a loop of Henle in the mammaliantype nephrons, birds can concentrate urine. The avian renal portal system does not provide blood to the loops of Henle but only to the proximal and distal tubules (Dantzler, 1985). Acknowledgments This work was supported in part by a grant from the Ontario Veterinary College Pet Trust and the Metropolitan Toronto Zoological Society. The author acknowledges the valuable input of IK Barker, and also V Lounsbury for artistic work. Volume 9, No. 1,1999

6 REFERENCES Akester AR Radiographic studies of the renal portal system in the domestic fowl, Gallus domesticus. J Anat, 98: Akester AR Renal portal shunts in the kidney of the domestic fowl. J Anat, 101: Akester AR, Mann SR Adrenergic and cholinergic innervation of the renal portal valve in the domestic fowl. J Anat, 104: Ashley LM Laboratory anatomy of the turtle. WmC Brown Co Pub, Dubuque, IA. Beck K, Loomis M, Lewbart G, Spelman L, Papich M Preliminary comparison of plasa concentrations of gentamicin injected into the cranial and caudal limb musculature of the eastern box turtle (Terrapene Carolina Carolina). J Zoo Wildl Med 26: Beddard FE Contributions to the anatomy of the Lacertilia-(l) On the venous system in certain lizards. Proc Zool Soc, Beddard FE Some additions to the knowledge of the anatomy, principally of the vascular system, of Hatteria, Crocodilus, and certain Lacertilia. Proc Zool Soc, Beddard FE. 1906a. On the vascular system of Heloderma, with notes on that of the monitors and crocodiles. Proc Zool Soc, Beddard FE. 1906b. Contributions to the anatomy of the Ophidia. Proc Zool Soc, Bojanus LH Anatome Testudinis Europaeae. Reprinted by Society for the Study of Amphibians and Reptiles, Department of Zoology, Univ Ohio, Athens, OH. Braun EJ Intrarenal blood flow distribution in the desert quail following salt loading. Am J Physiol, 231: Dantzler WH Comparative aspects of renal function. In Seldin DW, Giebisch G (eds): The Kidney: Physiology and Pathophysiology. Raven Press, New York, NY: De Ryke W The vascular structure of the kidney in Chrysemys marginata belle (Gray) and Chelydra serpentine (L.). AnatRec, 33: Duda PL The venous system of Agama tuberculate. Brit J Herp, Forster RP The nature of the glucose reabsorptive process in the frog renal tubule. Evidence for intermittency of glomerular function in the intact animal. J Cell Comp Physiol, 20: Hochstetter F Beitrage zur Entwicklungsgeschichte des Venensystems der Amnioten. 11. Reptilien. Morph Jb, 19: Holz P, Barker IK, Burger JP, Crawshaw GJ, Conlon PD. 1997b. The effect of the renal portal system on pharmacokinetic parameters in the re-eared slider, Trachemys scripta elegans. J Zoo Wild Med, 28: Holz P, Barker IK, Crawshaw GJ, Dobson H The Volume 9, No. 1,1999 anatomy and perfusion of the renal portal system in the red-eared slider, Trachemys scripta elegans. J Zoo Wild Med, 28: Jourdain S Recherches sur la veine porte renale. Annales des Sciences Naturelles. Zool Biol Anim, 12: LeBrie SJ, Sutherland LDW Renal function in water snakes. Am J Physiol, 203: Mader DR Antibiotic therapy. In Frye FL. (ed): Biomedical and Surgical Aspects of Captive Reptile Husbandry, 2nd ed. Krieger Publishing Company, Malabar, Florida, USA: Naw-Than-Kyaing The anatomy and histology of Calotes mystaceus Dum & Bibr., Union Burma J Life Sci, 1: O Donoghue CH The circulatory system of the com mon grass-snake, Tropidonotus natrix. Proc Zool Soc, Oelofsen BW Renal function in the penguin, Spheniscus demersus, with special reference to the role of the renal portal system and renal portal valves. Zool Afr, 8: Oelofsen BW The renal portal valves of the ostrich Struthio camelus. South AFR J Sci, 73: Perschmann C Ober die Bedeutung der Nierenpfortader insbesondere fur die Ausscheidung von Hamstoff und Hamsaure bei Testudo hermanni Gml. und Lacerta viridis Laur. sowie uber die Funktion der Hamblase bei Lacerta viridis Laur. Zool- Beitr, 2: Pokras MA, Sedgwick CJ, Kaufman GE Therapeutics. In Beynon PH (ed): Manual of Reptiles, British Small Animal Veterinary Association, Shurdington, Gloucestershire, UK: Rathke H Von dem Herzen und den Blutgefassen. In Untersuchungen uber die Entvvickelung und den Korperbau der Krokodile, Vieweg, Braunschweig, Germany: Saunders JT, Manton SM The lizard, Lacerta viridis. In A Manual of Practical Vertebrate Morphology, 4th ed, Clarendon Press, Oxford, UK. Sawyer WH Effect of posterior pituitary extracts on urine formation and glomerular circulation in the frog. Am J Physiol, 164: Spanner R Bau und Kreislauf der Reptilienniere. Zeitschrift fur Anatomie und Entwicklungsgeschichte, 76: Spanner R Uber die Wurzelgebiete der Nieren-, Nebennieren-und Leberpfortader bei Reptilien. Morph Jb, 63: Splechtna H Zur Struktur und Gefassversorgung der Reptilienniere. Zoologica (Stuttgart): 41: Thapar GS On the venous system of the lizard, Varanus bengalensis (Daud). Proc Zool Soc, Zarnik B Vergleichende Studien uber den Bau der Niere von Echidna und der Reptilienniere. Jenaische Zeitschr f Naturwiss, 46: Zwart P Anatomy, histology and physiology of the normal reptilian kidney. In Studies on renal pathology in reptiles, Stichting Pressa Trajectina Lepelenburg 1, Utrecht, Netherlands:8-25. Bulletin of the Association of Reptilian and Amphibian Veterinarians 9

7 V et e r in a r y S u rgery The Official Journal of the American College o f Veterinary Surgeons, Inc., The American College of Veterinary Anesthesiologists, and The European College of Veterinary\ Surgeons #< IlF Editor-in-Chief: Philip B. Vasseur, DVM A subscription to VETERINARY SURGERY brings you more than original, peer-reviewed articles and developments in veterinary surgery and anesthesia. It gives you the inside track on how to use this inform ation to m ake your work reflect the state-of-the art and save lives. S ubscription Ra t e s: Every issue brings you articles from leading veterinarians in the United States and abroad. Coverage ranges from surgical techniques and diagnostic aids to advances in surgically related diseases of small and large animals. In addition, detailed illustrations underscore key concepts and clinical techniques, making it easier for you to apply new procedures in your practice. E ach issue of V eterinary S urgery: Correlates research with clinical applications to ensure greater accuracy in treatment and diagnosis. Addresses significant problems in veterinary surgery and anesthesiology, providing relevant case histories and observations. Places developments in perspective, encompassing new concepts and commentary, to help you better understand and evaluate your surgical patients. I n s i d e US Individuals $ Institutions $ Students* $81.00 O u t s i d e US Individuals $ Institutions $ Students $ *To receive the student rate, orders must be accompanied by the name o f the affiliated institution, dates of study and the signature of program coordinator on institution letterhead. Orders w ill be billed at the individual rate until proof of status is received. P l e a s e d i r e c t o r d e r s t o t h e f o l l o w in g ADDRESSES: I n TH E US: W.B. Saunders Company, Periodicals Department, 6277 Sea Harbor Drive, Orlando, FL A g e n t s f o r A u s t r a l ia : Harcourt Brace & Company Pty. Ltd., Locked Bag 16, Marrickville, N ew South Wales 2204, Australia A g e n t s f o r E u r o p e : Harcourt Brace & Com pany Ltd., Oval Road, London NW1 7DX, England A g e n t s f o r J a pa n a n d K o r e a : Harcourt Brace Japan, Inc., Ichibancho Central Building, 22-1 Ichibancho, Chiyoda-Ku, T okyo 102, Japan A l l O t h e r C o u n t r ie s : Contact the US address O r v is it OUR HOME p a g e : Browse t h e Journal o nlin e a t : W.B. S a u n d e r s C o m pa n y A Division o f Harcourt Brace & Company ) W.B. Saunders Company Add the applicable sales tax for your area. All prices subject to change w ithout notice. ISSN:

8 Seminars in Avian & Exotic Pet Medicine Alan M. Fudge, DVM, Editor Seminars in Avian and Exotic Pet Medicine provides concise, topical, and authoritative reviews that address the problems you face in your practice. Guest Editors all selected for their expertise in treating birds and exotics prepare every issue and invite contributors to survey optimal diagnostic methods, therapeutic strategies, follow-up, and health maintenance. These concise, clinically oriented issues concentrate on a single topic, so you can refer to them continually in your daily practice. A rapid publication schedule ensures that you receive current, clinical information long before it appears in monographs and traditional references. Each issue is devoted to a single topic in avian medicine. In addition, a non-avian column included in every issue will keep you informed of therapies of choice for a single exotic species, such as rodents, lagomorphs, cavids, pot-bellied pigs, reptiles, ornamental fish, exotic carnivores, and amphibians ISSUES January April July October Anesthesia & Analgesia (J. Comick-Seahom) Renal Diseases (D.N. Phalen) Nutrition and Nutritional Disorders (S. Donoghue) Endoscopic Surgery (M. Taylor) SUBSCRIPTION RATES Domestic: Individuals: $95.00 Institutions: $ Students: $54.00* Outside U.S.: Individuals: $ Institutions: $ Students: $ *To receive the student rate, orders must be accompanied by the name of affiliated institution, dates of your term of study, and the signature of your academic advisor on school letterhead. Orders will be billed at the individual rate until proof of status is received. TO ORDER Please Direct Orders to the Following Addresses: In the U.S.: W.B. Saunders Company, Periodicals Department, 6277 Sea Harbor Drive, Orlando, FL Agents for Australia: Harcourt Brace & Company Pty, Ltd., Locked Bag 16, Marrickville, New South Wales 2204, Australia. Agents for Europe: Harcourt Brace & Company Ltd., Oval Road, London, NW1 7DX, England. Agents for Japan and Korea: Harcourt Brace Japan, Inc., Ichibanco Central Building, 22-1 Ichibanco, Chiyoda-Ku, Tokyo 102, Japan. All Other Countries: Contact the U.S. address. Or visit our home page: W.B. SAUNDERS COMPANY A Division of Harcourt Brace & Company 1998 W.B. Saunders Company. All prices subject to change without notice. Add the applicable sales tax for your area.

9 ARAV Externship Opportunities/Instructional Database Name of Practice/Institution: Address: Telephone: Fax:.. . Contact/Extern Mentor Please check all interests/specialties: gimphibians chelonians lizafds snakes venomous reptiles basic husbandry breeding nutrition surgery Number or percentage of herptile cases seen weekly: How many hours per week will the extern-mentor spend with the student? Application deadline: Application materials requested: Student/Extern prerequisites (eg. senior veterinary student, previous experience, etc.): Preferred time of year/dates: Equipment in use (check all that apply): Isoflurane anesthesia Endoscope Electrosurgery Ultrasonography Microbiology (in-house) Radiology Hematology (in-house) Other: Are you willing to lecture to interested groups of veterinary students? yes no How far would you travel?. What would you expect in the way of renumeration?. What is your availability? Please list the topic or topics you would cover in lecture?. Would you be able to run a wetlab and if so, on what subject? If you are aware of an advanced herpetoculturist who you believe would be able to lecture to interested veterinary students, please provide their name, address and telephone below or photocopy this form and ask them to complete the information for our database. Name: Organization:. Address: Telephone: Fax: - Please return to: Michael S. Bodri, DVM, PhD, Small Animal Science and Conservation, 112 Feldman, Delaware Valley College, 700 E. Butler Ave., Doylestown, PA Fax: , BodriM@devalcol.edu The A sso c ia tio n o f R e p t il ia n a n d A m p h ib ia n V e t e r in a r ia n s

10 T he A sso ciatio n o f R e ptilia n a n d A m ph ibia n V eterinarians What is the ARAV? The A ssociation of R eptilian and Amphibian Veterinarians (ARAV) is a nonprofit international organization of veterinarians and herpetologists founded in O ur goal is to im prove reptilian and amphibian husbandry and v eterin ary care through education, exchange of ideas and research. The I ARAV prom otes co n serv atio n and humane treatment of all reptilian and amphibian species through education, captive b reeding and rep tilian and amphibian habitat preservation. Benefits of Membership Membership is open to anyone with an interest in veterinary care of reptiles and amphibians. Membership benefits include subscription to the quarterly Bulletin of the ARAV, reduced tuition for the annual conference, annual conference proceedings and membership directory, support of conservation and research funds, and pride in supporting the advancement of reptilian and amphibian medicine and surgery. The B ulletin o f the A R A V is peer reviewed, referenced, indexed and features state-of-the-art approaches to quality veterinary care of diverse reptiles and amphibians. Sections within the Bulletin include: Message to Members In My Experience Case Reports Care-in-Captivity Original Articles Techniques Pathology Pages Nutrition Notes Literature and Book Reviews Announcements The Bulletin o f the A R A V is primarily designed to benefit practicing veterinarians, from novice to advanced. The Annual Conference and Proceedings includes the most current information on nutrition, husbandry, infectious diseases, basic and advanced diagnostics, surgical and medical therapeutics and veterinary care, and tips you can incorporate immediately into practice. A variety of wetlabs and workshops are designed to keep you current with this ever changing field. The membership directory provides an alphabetical as well as geographical listing of members, addresses, phone and fax numbers. The ARAV needs your participation! We invite you to join forces with over a thousand other professionals by filling out the membership application and supporting the organization that is improving veterinary care for reptiles and amphibians. Membership Dues North America $55.00, Libraries North America $90.00, Veterinary Technicians $45.00, Veterinary Students $35.00, (add $15.00 to all previous categories if outside North America). Payments must be in US dollars drawn on a US bank, or by International/World Money Order, or by Visa or Mastercard. Dues payable on a calendar year basis to the Association of Reptilian and Amphibian Veterinarians (ARAV), PO Box 1897, Lawrence, Kansas, , USA. ARAV Membership Application Please Print or Type Legibly (information supplied hereon will appear in the membership directory). Name Renewal Professional Establishment Telephone: New Member Mailing Address Business ip Home (optional) - Degree/Year of graduation/ School Fax Interests Dues*: North America $55.00 Veterinary Technicians $45.00 *Add $15.00 to all categories if Libraries North America $90.00 Veterinary Students $35.00 outside North America. Amount Enclosed: Credit Card Payment Visa Mastercard. Amount Card No Exp Name (print) : Signature For more information contact Wilbur Amand, VMD, ARAV Executive Director, , fax Volume 9, No. 1,1999 Bulletin of the Association of Reptilian and Amphibian Veterinarians 13

11 1999 Advertising Rates f \ m a Drr* B a K lh The BULLETIN, the official publication of the Association of Reptilian and Amphibian Veterinarians (ARAV), is considered one of the major sources of information on the biology and veterinary aspects of reptiles and amphibians. The BULLETIN is published quarterly, peer reviewed and international in scope and distribution. The ARAV has over 1300 members from around the world. The BULLETIN reaches more than 2000 readers, including practicing veterinarians, zoo and wildlife veterinarians, academic veterinary faculty, veterinary school libraries, veterinary students and professional and amateur herpetologists. These are the exact sizes for placement in the BULLETIN of the ARAV. Use these as your guide for correct sizing. M BLACK & WHITE Display Advertising Rates Per Issue (US Dollars) Size (in inches) lx 2x 3 and 4x Full Page (77<" x 10") Half Page (774" x 4 7s ) DHC (41I/f«" x 47s") DQC (4n/.6" x 2'U') QC (274 x 2'U') m Inside Front Cover 650 Inside Back Cover 550 Outside Back Cover 750 Classified Ads (per issue) 50 m CONTRACT AND DISCOUNT TERMS Advertisers will be required to sign a contract for ads that run more than once. This is a binding contract and once signed will be payable as the contract implies. Advertisements for one issue does not require a contract but must be pre-paid in full. Consecutive issue advertisements will need the first run paid in full, and after a signed contract is received, the balance of runs will be due within 30 days. - 1 Mi WwiKL BLACK & WHITE ADVERTISEMENTS Line Art: The highest quality line art ad can be obtained by paying for an RC, created by a graphic arts company. Good laser print copies will be accepted at an additional one time charge of $ Photocopies of advertisements WILL NOT be accepted. Film Form: Right-reading, emulsion-side-down negative and 133-line screens are recommended to protect advertisers from copyright infringement, plagerism or libel resulting from their ad. Publication of advertisement shall constitute final acceptance of the advertiser s order. We are not liable for the quality of how camera-ready ads appear after they are printed (follow the above guidelines and your ads will be of good quality). We prefer not to accept ads that list live animals but welcome advertisements for animal dealers. Advertiser Contact Person Address City State Zip Phone Signature Fax Size _# of issues Amt. enclosed To advertise your products and services to our readers, simply complete the above information and send a copy of your ad along with a check payable to the ARAV to: Wilbur Amand, VMD, Executive Dirrector, ARAV, 6 North Pennel Road, Media, PA Bulletin of the Association of Reptilian and Amphibian Veterinarians Volume 9, No. 1,1999