Herpetology Notes, volume 14: 588-589 (2021) (published online on 29 March 2021)

Description of an abnormal tail bifurcation in Gehyra oceanica (Lesson, 1830)

Lawrence G. Bassett1,*, Ferris E. Zughaiyir1, and Michael R. J. Forstner1

Tail autotomy is a behaviour utilised by many lizard taxa only on oceanic islands (Tonione et al., 2016) and is to avoid predation or escape aggressive encounters with commonly encountered on the vertical surfaces of conspecifics (Pianka and Vitt, 2003). In this behaviour, tree trunks and anthropogenic structures. In French lizards can release a portion of their tail once it is grasped Polynesia, G. oceanica is sympatric with Lepidodactylus by a predator thereby gaining an opportunity for escape. lugubris (Duméril & Bibron, 1836), Hemidactylus Autotomy is achieved via intense muscle contractions frenatus Duméril & Bibron, 1836, and Gehyra mutilata in the base of the tail and generally results in minimal (Wiegmann, 1834). Gehyra oceanica is the largest of blood loss (Vitt and Caldwell, 2009). Following release, the aforementioned gekkonid species, attaining a snout the tail will often continue to thrash about for several to vent length of 59–84 mm (Sabath, 1981). To avoid minutes by using anaerobic metabolism (Pianka and predation, this gekkonid will shed large patches of skin Vitt, 2003). This continued movement further distracts and drop its tail (Ferris E. Zughaiyir, pers. obs.). the predator and facilitates the lizard’s escape (Dial and At 04:45 h on 23 October 2016, one of the authors Fitzpatrick, 1983). (Ferris E. Zughaiyir), observed an adult G. oceanica In the species for which tail regeneration is possible, with a bifurcated tail on the interior wall of a residential the rate of regrowth varies widely depending on building in Paopao, Moorea-Maiao, French Polynesia environmental temperature and taxon (Noble and (17.4904°S, 149.8261°W; WGS 84; Fig. 1). The gecko Bradley, 1933; Hughes and New, 1959; Bryant and made an attempt to escape prior to capture and in the Bellairs, 1976). Additionally, vertebrae of the tail process exhibited slightly abnormal locomotion with are not regenerated and are instead replaced with a cartilaginous rod (Lozito and Tuan, 2017). Regeneration malformations, also known as multi-furcations, can range from simple tail bifurcations to hexafurcations. This phenomenon of malformation is currently known to occur in 175 lepidosaurian species spanning 22 families (Barr et al., 2020). Recently, tail regrowth has also been documented in an archosaur, the America alligator (Alligator mississippiensis) (Xu et al., 2020). Within the family Gekkonidae, abnormal tail regeneration has been documented in 2.09% of all currently recognised species (Barr et al., 2020). Herein we provide what we believe to be the first report of abnormal tail regeneration and tail bifurcation in the gekkonid species Gehyra oceanica. Gehyra oceanica is an arboreal gecko endemic to the Pacific Basin (Beckon, 1992). This species exists

1 Department of Biology, Texas State University, 601 University Figure 1. Gehyra oceanica in situ on the interior wall of Drive, San Marcos, Texas 78666, USA. a residential building in Paopao, Moorea-Maiao, French * Corresponding author. E-mail: [email protected] Polynesia. Note that the tail on this individual is bifurcated at © 2021 by Herpetology Notes. Open Access by CC BY-NC-ND 4.0. the distal end. Photo by Ferris E. Zughaiyir. 589 Lawrence G. Bassett ������ exaggerated lateral trunk bending. Upon capture, the gecko was briefly photographed (Fig. 2) and then released. Given the atypical movement observed in this individual, we speculate that tail malformation may have negatively affected locomotion in this specimen of G. oceanica and thus interfered with important activities such as prey acquisition and predator escape. It is possible, however, that the abnormal locomotion observed was the result of a separate injury the lizard sustained in conjunction with the event that caused tail autotomy and subsequent bifurcation. Further research is needed to determine the prevalence of tail malformations in this population as well as any associated fitness costs. Such an investigation would be particularly worthwhile given the marked vulnerability of some island-dwelling herpetofauna to introduced predators (e.g., Hays and Conant 2007; Towns et al., 2007; Medina et al., 2011).

Acknowledgments. We thank James Barr for his thoughtful and meticulous review of an earlier version of this manuscript.

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