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) ofto Varanus the type melinus series compared(after Böhme to the andtype Zieglerseries (after1997). 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.