First record of tail bifurcation in Lygodactylus klugei (Smith, Martin & Swain, 1977) (Sauria: Gekkonidae), with comments on caudal adhesive pads

The process of caudal regeneration in lizards does not always occur perfectly, which can cause some abnormalities, such as the appearance of warped or supernumerary tails. Here we report the first cases of tail bifurcation in the Dwarf Gecko, Lygodactylus klugei, and observations about the caudal adhesive pads in individuals with bifurcated tails. Our observations represent a new case of caudal bifurcation for lizard species that have tails with functional specializations and elaborate morphological structures and are the first records of this type of anomaly for the genus Lygodactylus.

During studies carried out with the species, we recorded two cases of an individual with a bifid tail. The first specimen was an adult female (CHUFCL 7260; SVL = 27.9 mm, Figure 1A, 1B) collected on July 6, 2018, in the municipality of Pentecoste (-3.81843 S, -39.33923 W; 65 m a.s.l.), Ceará, Brazil. The bifurcation occurred 19.37 mm posterior to the cloaca. The first branch was 5.1 mm long and a second branch was 3.57 mm long. Both branches were uniform in color, with no apparent differentiation of the scales. The second specimen was an adult male (CHUFCL 7319; SVL = 25.55 mm, Figure 1C Tail bifurcation in Lygodactylus klugei a.s.l), Paraíba, Brazil. In this case, the bifurcation was very inconspicuous and located in the terminal portion of the tail, 17.52 mm posterior to the cloaca. The longest branch was 2.06 mm, and the second branch was 1.16 mm and darker.
According to Alibardi (2010), these deformities can be caused by incomplete caudal autotomy, as well as by a crushed spinal cord and ependymal within the tail. Although it is not possible to confirm this with our data, we suggest that both cases of bifurcation were derived from previous injuries where there was incomplete autotomy, but the damage was sufficient to start the process of regeneration and growth of a new tail in the affected places (DUDEK; EKNER-GRZYB, 2014), which resulted in a supernumerary tail in each individual.
The tip of the tail of L. klugei has specialized glandular structures similar to the adhesive pads found on the fingers (SMITH et al., 1977). Studies using scanning electron micrographs report that the regenerated tail in this species has the same structures and performs the same functions as the original tail, although there are imperfections (VITT; BALLINGER, 1982). Although we did not investigate the ultrastructure of the region, we did not observe adhesive pads on any of the caudal branches of both individuals at macroscopic levels (Figure 2A-D). The visual absence of these structures compared to the original tails in other individuals ( Figure 2E) leads us to believe that the bifurcation processes described here occurred in previously regenerated tails.
Although there are no studies on the effects caused by supernumerary tails, occasional reports suggest that the presence of these anomalies can negatively affect the fitness of individuals, but without apparent changes in survival rates (see HENLE; GRIMM-SEYFARTH, 2020). Visually, we did not observe any type of locomotor deficiency or difficulty in escaping during the capture process of both individuals compared to other L.
klugei specimens with non-bifurcated tails. Although tail loss can impair the ability to escape on vertical surfaces in Lygodactylus (VITT; BALLINGER, 1982;MEDGER et al., 2008), the effects of multiple tails with additional adhesive structures, and whether these are functional in the natural environment, are still unknown.
During our studies developed over a year in 12 populations of L. klugei, 249 individuals were captured. The findings of bifurcated tails described here represent an occurrence of 0.8%, a value similar to those found for some lizard populations, such as Ophisops elegans Ménétries, 1832(TAMAR et al., 2013 When we analyze the populations of L. klugei from this research independently, the total number of individuals sampled in each location corresponds to 23 and 21 for the Patos and Pentecoste populations, respectively. In addition to the results obtained by Henle and Grimm-Seyfarth (2020), the cases described here are a new record of tail bifurcation for lizard species that have tails with functional specializations and elaborate morphological structures and are also the first reports of this type of anomaly for the genus Lygodactylus.