Herpetology Notes, volume 7: 723-729 (2014) (published online on 21 December 2014)

First case of conjoined twins in the Quince Monitor Lizard Varanus melinus Böhme & Ziegler, 1997

Mona van Schingen1, 2, * and Thomas Ziegler1, 2

Abstract. We report on the first case of conjoined twinning in the Quince Monitor Lizard Varanus melinus and provide a detailed morphological description of abnormally developed offspring. Parents were siblings and produced two clutches which both contained normally developed, viable offspring next to unfertilized eggs and malformed, dead individuals. This also is the first report on the development of conjoined twins in the Pacific monitor lizard species group, and the second case of conjoined twinning reported for monitor lizards in general. We further present an overview of published cases of twinning and the development of malformations in reptiles as well as potential causes such as genetic or environmental factors.

Keywords: Squamata, Varanidae, monozygotic twinning, malformations, morphology.

Introduction lizards, such as agamids (Förther, 2002) and gekkonids (Rösler, 1979). Concerning monitor lizards, reports of Several cases of twinning have been reported for conjoined twins are only known for members of the diverse taxa of reptiles, such as turtles (Lehmann, 1984; emerald tree monitor lizard (Varanus prasinus) species Piovano et al., 2011), crocodiles (Platt et al., 2001), group. Jacobs (2002) reported a case of an individual snakes (Kinkaid, 1996) and lizards (Mendyk, 2007). with a twofold developed head due to cross breeding With respect to monitor lizards, cases of twinning between the closely related species V. kordensis and V. have been reported for eight species: Varanus gouldii prasinus. Recently, Ziegler et al. (2010) reported on the (Hartdegen and Bayless, 1999), V. indicus (Speer and first F2 reproduction of the Quince monitor lizard, V. Bayless, 2000), V. kordensis (Jacobs, 2002), V. macraei melinus Böhme and Ziegler, 1997, a Moluccan species (Mendyk, 2007), V. mertensi (Eidenmüller and Stein, of the V. (Euprepiosaurus) indicus group. Parents 1991), V. ornatus (Mendyk, 2007), V. panoptes horni held at the Cologne Zoo Terrarium were siblings and (Bayless, 1999) and V. semiremex (Jackson, 2005). In produced two clutches deposited in June and September addition, a case of triplets has been reported for V. varius 2009 consisting of nine and five eggs, of which six by Krauss and Horn (2004). However, cases of conjoined and two individuals finally hatched. Of the first clutch, twins in reptiles are much rarer. Several reports of this two eggs did not show any development and one egg phenomenon exist for turtles (Mähn, 1997; Sailer et al., contained dead conjoined twins. The eggs of the second 1997; Stumpel, 2008), crocodiles (Youngprapakorn et clutch contained two eggs without development and al., 1994; Webb and Manolis, 1998; Velasco, 2010) and another egg containing a dead, malformed offspring. We herein provide a morphological description of the abnormalities of both the conjoined twins and the malformed sibling, compared with normally developed V. melinus, considering anatomy, morphometry, osteology and pholidosis. Besides documenting the 1 Cologne Zoo, Riehler Straße 173, 50735, Cologne, Germany first case of conjoined twins in a member of the Pacific 2 University of Cologne, Institut of Zoology, Department of Terrestrial Ecology, Zülpicher Straße 47b, 50674, Cologne, monitor lizard (V. indicus) species group we further Germany discuss potential causes for the development of such * Corresponding author e-mail: [email protected] malformations. 724 Mona van Schingen & Thomas Ziegler

Materials and methods Abbreviations are as follows: SVL: snout-vent length, from tip of snout to cloaca; TaL: tail length from cloaca The conjoined twins and the malformed hatchling to tip of tail; ToL: total length, tip of snout to tip of tail; of Varanus melinus were preserved in 70 % ethanol A: head length, from tip of snout to tip of tail; B: head and deposited in the herpetological collection of the width, maximum width between eyes and ears; C: head Zoologisches Forschungsmuseum Alexander Koenig height, above the eyes; G: distance from anterior eye (ZFMK) in Bonn, Germany. ZFMK 96604a and ZFMK margin to middle of nostril; H: distance from middle 96604b refer to the twins and ZFMK 96605 to the of nostril to tip of snout; ElHa: length from elbow to malformed individual. Morphological and meristic data insertion of hand; Thorn: length of a thorn-shaped scale (see Böhme and Ziegler 1997) were taken by dint of a formation at the neck on the right body side; P: scales stereo microscope (Leica MS5). For the measurements across head from rictus to rictus; Q: scales around tail (to the nearest 0.1 mm) a caliper was used. To determine base; R: scales around tail at approximately one-third the kind of divergence of the abnormal individuals, the from base; S: scales around midbody; T: transverse accordant data from the type series as given in Böhme ventral scale rows from gular fold to insertion of the and Ziegler (1997) was used as a reference. In addition, hind legs; N: gular scales from tip of snout to gular fold; a normally developed, but deceased juvenile of V. AG: scales from axilla to groin; TN: ventral scales from melinus (ZFMK 96606) with an age of maximally 10 tip of snout to insertion of hind legs; X: transverse dorsal months, which derived from the clutches deposited scale rows from hind margin of tympanum to insertion between June and September 2009 and thus descending of hind legs; c: supralabials exclusive the rostral scale; from the same parents was used for direct comparisons. Sub: sublabials exclusive the mental scale; M: scales For the study of the bone structure a radiogram was around neck anterior to gular fold; U: differentiated (= made with a Faxitron X-Ray Lx60. enlarged) supraocular scales.

Figure 1. Conjoined twins (ZFMK 96604a, b) of Varanus melinus. A: Twins in egg; B: Cranial adhesion of the twins; C: Abdominal adhesion; D: Egg tooth of ZFMK 96604a. Photos: T. Ziegler. First case of conjoined twins in the Quince Monitor Lizard 725 1 Table 1: Mensural and selected meristic data of the conjoined twins (ZFMK96604), the Table 1. Mensural2 andmalformed selected siblingmeristic (ZFMK data of 96605), the conjoined and a normally twins (ZFMK96604), developed specimen the malformed (ZFMK 96606) sibling of (ZFMK 96605), and a normally developed3 Varanus specimen melinus (ZFMK compared 96606) of to Varanus the type melinus series compared (after Böhme to the andtype Zieglerseries (after 1997). Böhme For and Ziegler 1997). For abbreviations4 seeabbreviations material and see methods; material all and measurements methods; all measurements in mm. Bilateral in mm. values are given as left / right. 5 6 Abbreviation ZFMK96604a ZFMK96604b ZFMK 96605 ZFMK 96606 Type series SVL 49.6 40 – 50 91.1 160.0 300 – 420 TaL 111.9 84.4 134.3 238.6 520 – 730 ToL 161.5 124.4 – 134.4 225.4 398.6 920 – 1150 A 19.8 / 20.2 17.7 / 17.6 26.3 / 24.9 31.5 48 – 67 B 10.9 9.1 14.6 16.1 21 – 30 C 7.8 6.9 10.5 12.6 16 – 22.5 G 5.0 / 4.0 4.2 / 3.5 8.2 / 7.6 8.3 13 – 20 H 5.1 / 4.7 3.2 / 3.7 7.4 /6.4 6.4 7 – 11 ElHa 14.2 / 10.9 9.3 / 9.2 - 16.4 / 16.2 - Thorn 0.1 0.04 0.29 - - G/H 0.98 / 0.85 1.3 / 0.95 1.1 / 1.2 1.3 1.67 – 1.86 A/B 1.82 / 1.85 1.95 / 1.93 1.8 / 1.7 1.96 2.23 – 2.39 A/C 2.54 / 2.59 2.57 / 2.55 2.5 / 2.4 2.5 2.75 – 3.06 P 47 42 43 42 46 – 55 Q 81 64 69 81 81 – 85 R 50 50 52 58 58 – 68 S 98 - 144 126 124 – 130 T 90 56 90 / 69 90 87 – 99 N 56 49 80 / 73 84 86 – 89 AG 67 / 68 56 / 29 88 / 60 105 / 105 - TN (=T+N) 146 105 170 / 142 174 173 – 187 X 36 / 12 36 / 22 52 / 38 40.7 29 – 45 c 27 / 25 16 / 22 26 / 25 – 26 25 27 – 30 Sub 27 / 25 13 / 21 25 / 26 25 / 26 - M 100 68 104 86 83 – 90 U 5 / 4 3 / 4 0 / 2 4 – 5 / 5 - 7

Results smaller specimen (ZFMK 96604b), has less developed extremities than ZFMK 96604a and a truncated body Morphometric data and scale counts of the conjoined (Fig. 1C). The vertebral column of ZFMK 96604a is twins (ZFMK 96604a and ZFMK 96604b) and the malformed hatchling (ZFMK 96605) in comparison curved to the dorsum (Fig. 2), and that of ZFMK 96604b is likewise bound upwards and additionally looped at with the normally developed juvenile (ZFMK 96606) 1 and respective data of the type series (Böhme and the midbody, while the trunk is folded (Fig. 2). The Ziegler, 1997) are shown in Table 1. head of ZFMK 96604a is laterally bent, with the mental Description of the conjoined twins (ZFMK 96604a scale being displaced from frontal to lateral. The upper and ZFMK 96604b) jaw is reduced and the snout notched in position of the The twins are both cranially and abdominally egg tooth while the lower jaw overhangs (Fig. 1, D). (over abdominal-tissue) conjoined (so called Concerning the mouth part, ZFMK 96604b also shows cephalothoracopagus conjoined twins), generally malformations, namely a reduction of the left mouth well developed and have entire extremities and tails. part, discernible in the distinctly lower number of labial However, the belly of both individuals is open (Fig. 1, scales (13 vs. 21 sublabials and 16 vs. 22 supralabials, A-C). see Table 1). Furthermore the left hind leg of ZFMK Both individuals have distorted vertebral columns, 96604b terminates in two separated feet, which are which is visible from the radiogram (Fig. 2). The aligned between first and second toes (Fig. 2). One foot 726 Mona van Schingen & Thomas Ziegler

thorn-shaped formation of scales on their right body side behind the gular fold. With respect to scalation the specimen ZFMK 96604b further differs from its sibling, the normally developed specimen and the type series (see Table 1) in having less scales around the tail base (64 versus 81–85), and less ventral scale rows between the gular fold and the insertion of the hind limbs (56 versus 87–99). ZFMK 96604a has a reduced number of scales around the midbody compared with the normally developed specimen and the type series (98 versus 124–130). Both conjoined twins have a distinctly lower number of gular scales (49–56 versus 84–89) and a reduced number of ventral scales between the snout and the hind limbs (105–146 versus 173–187), compared Figure 2. Radiogram of the conjoined twins (ZFMK 96604a, with the normally developed specimen and the type b) of Varanus melinus. series. Furthermore we found differences between the two body sides in both siblings: ZFMK 96604b has 56 and 29 ventrolateral scales between the insertions of the fore- and hind limbs on its two body sides, while ZFMK 96604a has about 67–68 ventral scales on each side, contains six toes, of which two are truncated and end in which is distinctly fewer than the 105 scales counted a thickened claw. The foot of the right hind limb features in the normally developed individual (ZFMK 96606); two coadunate toes. Both twins dorsolaterally show a ZFMK 96604a in addition shows an asymmetry in fore

Figure 3. Malformed Varanus melinus (ZFMK 96605). A: Curved vertebral column; B: Opened vent; C: Malformed cranium; D: Lateral thorn-shaped formation of scales. Photos: T. Ziegler. First case of conjoined twins in the Quince Monitor Lizard 727

and Böhme (1999) for an adult male V. melinus. The sulcus spermaticus is discernible, stretching terminally to the outer lobe. The apical platform is asymmetrically prolonged towards the outer lobe. Terminally, from both asymmetrical lobes, the two elastic hemibacula are protruding. The inner hemibacula are larger, shovel- shaped, apically-directed and with broadened ends. The smaller, outer and laterally-oriented hemibacula are also discernible. At the outer lobes there are hints of paryphasman rows discernible.

Discussion The three analyzed, malformed hatchlings of Varanus melinus differ in several traits from normally developed individuals. The conjoined twins are noticeably smaller Figure 4. Radiogram of the malformed individual (ZFMK compared to their normally developed siblings (SVL 96605) of Varanus melinus. 49.6 and 40–50 mm versus 109–116 mm, see Ziegler et al., 2010). Also the malformed individual ZFMK 96605 is slightly smaller (SVL 91.1 mm). However, the fact that terminal structures (such as spikes and spines) are not discernible in the hemibacula of the individual limb lengths (elbow-hand on the left 14.2 mm vs. 10.9 ZFMK 96605 cannot be regarded as malformation, mm on the right, see Table 1). because such indifferent development might be due to Description of the malformed hatchling (ZFMK the developmental stage. This is also the reason for the 96605) everted condition of the hemipenes, which in general are The vertebral column of ZFMK 96605 (see Fig. 3) only retracted into the tail base shortly before hatchling is flexed at the most posterior part of the trunk and (e.g., Ziegler and Böhme, 1997). The three analyzed, the insertions of the hind limbs are not symmetrically malformed individuals differ with respect to modified developed, which is apparent from the radiogram (Fig. scale counts, malformations of body parts and thus 4). The following asymmetries in the outer body shape also proportions from normally developed individuals. were noted: abnormal proportions of the head; truncated maxilla; overlaying and right-bent mandible; rostral scale being in contact with the third left sublabial scale instead of the mental scale; cut from the left nostril to the middle of the third and fourth supralabial and a cranial swelling on the front between the eyes (Fig. 3). With respect to the normally developed specimen and the type series, the individual ZFMK 96605 furthermore differs in the following characters: notched tail base and thus less scales around tail base (69 vs. 81–85); a greater number of scales around the midbody (144 vs. 124–130) and a lower number of ventral scales on the right body side (170 left, 142 right vs. 173–187 ventral scale rows from snout to insertion of hind limbs). Furthermore, ZFMK 96605 dorsolaterally shows a thorn-shaped formation of scales on the right side, pointing to the dorsolateral fold. Both hemipenes of ZFMK 96605 are everted (Fig. 5). They are longish, passing apically into two Figure 5. Everted hemipenes of the malformed Varanus asymmetrically-shaped lobes as described by Ziegler melinus (ZFMK 96605). Photo: T. Ziegler. 728 Mona van Schingen & Thomas Ziegler

The conjoined twins also differ from each other and monitor lizards, Jacobs (2002) described a case of show asymmetries in scalation even between their conjoined twins as an outcome of the cross breeding own body sides. But the differing scalation apparently between the closely related species V. kordensis and does not follow a general principle, as e.g., one of the V. prasinus. Two of three fertilized eggs included conjoined twins (ZFMK 96604a), and the malformed embryos, which died before hatching. The remaining individual ZFMK 96605 developed increased numbers egg contained a specimen with a twofold developed of scales around the gular fold (100 and 104) whereas head, three forelegs but only one abdomen and tail. This the other twin (ZFMK 96604b) rather showed a reduced individual proved not to be viable and died quickly after number of scales around the gular fold (68) compared hatching. Similar to the situation in V. melinus reported to normally developed individuals (83–90). But in herein, the hybrid between V. kordensis and V. prasinus general a tendency towards scale number reduction is showed a strongly curved backbone and an opened vent discernible, most apparently in the individual ZFMK with some organs being arranged outside of the body. 96604b. This individual is also the less developed and Mähn (1997) supposed, that the disposition of the smaller conjoined twin. The case that one conjoined twin parents might be a cause for the development of twins is better developed than the other one was also reported (see also Heimann 1993). Further evidence for a by Rösler (1979) and Eidenmüller and Stein (1991). In correlation between the development of malformations addition, the ratios of measurements (G/H, A/B, A/C, and the genotypic variability of the parents was given see Tab. 1) show that the proportions of the abnormal by Gautschi et al. (2002). These authors found out hatchlings of V. melinus differ remarkably from the type that the snake Natrix tessellata showed an increased series. All three analyzed malformed hatchlings have development of anomalies in introduced, bottlenecked a relative broader, shorter and higher head and show a populations, implicating a lower genetic variability than different position of the nostril between the snout and in native populations. Another cause for the development eye. Although the three malformed individuals show of malformations was given by Velsaco (2010), who distinct differences compared with the type series, found an individual of the crocodile species Crocodylus from each other and their own body sides, we found acutus with a twofold body and 8 extremities in a clutch some joint features, such as an opened vent, a curved in the National Park Laguna de Tacarigua, Venezuela, or flexed vertebral column and a lateral thorn-shaped which is under influence of chemicals from agriculture. skin structure. Here, it is interesting to note that the In general, malformations can derive based on genetic three malformed individuals all derived from the same or environmental influences (Youngprapakorn et al., parents but developed from different clutches. Thus, 1994). Such phenomena can be traced back to the genetic predispositions as reason for the development lower Cretaceous for choristoderan reptiles (Buffetaut of identical or at least similar malformations cannot be et al., 2007). However, a potential relation between excluded, in particular as the parents were related to each relatedness of parents and probability of occurrence other. A low genetic variation is frequently contemplated of malformations and conjoined twins, which could be as reason for the development of malformations (e.g., possible based on the herein reported case, still needs Gautschi et al. 2002). In addition, conjoined twinning further verification and research. and the generating of further malformations apparently is often linked (e.g., Mähn, 1997; Rösler, 1997; Förther, Acknowledgements. We thank the ichthyology section of the 2002; Jacobs, 2002). ZFMK (Dr. Fabian Herder) for kindly taking radiograms. Concerning the occurrence of conjoined twins, Sailor et al. (1997) reported one case of well-developed References conjoined twins (only with anomalies in the lateral shields) in the turtle Testudo hermanni boettgeri over Bayless, M.K. (1999): Varanus gouldii horni: twins. Dragon News a period of ten years (opposed to 98 healthy offspring 2: 4. hatched from 117 eggs, which all were treated under the Böhme, W., Ziegler, T. (1997): Varanus melinus sp.n., ein neuer Waran der V. indicus- Gruppe von den Molukken, Indonesien. same conditions). Another isolated case of conjoined Herpetofauna 19: 26-34. twins (which were cranially conjoined, but otherwise Buffetaut, E., Jianjun, L., Haiyau, H., Zhang, H. (2007): A two- fully developed and which died shortly before hatching) headed reptile from the Creataceous of China. Biology Letters, was reported for the agamid Pogona vitticeps, which 3: 80-81. was successfully bred for a noticeable period of time Eidenmüller, B., Stein, R. (1991): Zwillingsanlage bei Varanus (Förther, 2002). 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Accepted by Christoph Liedtke