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Adhesive toe pads have evolved numerous times over lizard evolutionary history, most notably in geckos. Despite significant variation in adult toe pad morphology across independent origins of toe pads, early developmental patterns of toe pad morphogenesis are similar among distantly related species. In these distant phylogenetic comparisons, toe pad variation is achieved during the later stages of development. We aimed to understand how toe pad variation is generated among species sharing a single evolutionary origin of toe pads (house geckos—Hemidactylus). We investigated toe pad functional variation and developmental patterns in three species of Hemidactylus, ranging from highly scansorial (H. platyurus), to less scansorial (H. turcicus), to fully terrestrial (H. imbricatus). We found that H. platyurus generated significantly greater frictional adhesive force and exhibited much larger toe pad area relative to the other two species. Furthermore, differences in the offset of toe pad extension phase during embryonic development results in the variable morphologies seen in adults. Taken together, we demonstrate how morphological variation is generated in a complex structure during development and how that variation relates in important functional outcomes.

 

The auditory papilla of geckos contains two zones of sensory hair cells, one covered by a continuous tectorial membrane affixed to the hair bundles and the other by discrete tectorial sallets each surmounting a transverse row of bundles. Gecko papillae are thought to encode sound frequencies up to 5 kHz, but little is known about the hair cell electrical properties or their role in frequency tuning. We recorded from hair cells in the isolated auditory papilla of the crested gecko, Correlophus ciliatus , and found that in both the nonsalletal region and part of the salletal region, the cells displayed electrical tuning organized tonotopically. Along the salletal zone, occupying the apical two-thirds of the papilla, hair bundle length decreased threefold and stereociliary complement increased 1.5-fold. The two morphological variations predict a 13-fold gradient in bundle stiffness, confirmed experimentally, which, when coupled with salletal mass, could provide passive mechanical resonances from 1 to 6 kHz. Sinusoidal electrical currents injected across the papilla evoked hair bundle oscillations at twice the stimulation frequency, consistent with fast electromechanical responses from hair bundles of two opposing orientations across the papilla. Evoked bundle oscillations were diminished by reducing Ca 2+ influx, but not by blocking the mechanotransduction channels or inhibiting prestin action, thereby distinguishing them from known electromechanical mechanisms in hair cells. We suggest the phenomenon may be a manifestation of an electromechanical amplification that augments the passive mechanical tuning of the sallets over the high-frequency region. 

Abstract How developmental modifications produce key innovations, which subsequently allow for rapid diversification of a clade into new adaptive zones, has received much attention. However, few studies have used a robust comparative framework to investigate the influence of evolutionary and developmental constraints on the origin of key innovations, such as the adhesive toe pad of lizards. Adhesive toe pads evolved independently at least 16 times in lizards, allowing us to examine whether the patterns observed are general evolutionary phenomena or unique, lineage-specific events. We performed a high-resolution comparison of plantar scale development in 14 lizard species in Anolis and geckos, encompassing five independent origins of toe pads (one in Anolis, four in geckos). Despite substantial evolutionary divergence between Anolis and geckos, we find that these clades have undergone similar developmental modifications to generate their adhesive toe pads. Relative to the ancestral plantar scale development, in which scale ridges form synchronously along the digit, both padded geckos and Anolis exhibit scansor formation in a distal-to-proximal direction. Both clades have undergone developmental repatterning and, following their origin, modifications in toe pad morphology occurred through relatively minor developmental modifications, suggesting that developmental constraints governed the diversification of the adhesive toe pad in lizards. 

We report on the longest body length record for the Philippine Pit Viper, Trimereserus flavomaculatus. 

Among the most specialized integumentary outgrowths in amniotes are the adhesive, scale-like scansors and lamellae on the digits of anoles and geckos. Less well-known are adhesive tail pads exhibited by 21 gecko genera. While described over 120 years ago, no studies have quantified their possible adhesive function or described their embryonic development. Here, we characterize adult and embryonic morphology and adhesive performance of crested gecko ( Correlophus ciliatus ) tail pads. Additionally, we use embryonic data to test whether tail pads are serial homologues to toe pads. External morphology and histology of C . ciliatus tail pads are largely similar to tail pads of closely related geckos. Functionally, C . ciliatus tail pads exhibit impressive adhesive ability, hypothetically capable of holding up to five times their own mass. Tail pads develop at approximately the same time during embryogenesis as toe pads. Further, tail pads exhibit similar developmental patterns to toe pads, which are markedly different from non-adhesive gecko toes and tails. Our data provide support for the serial homology of adhesive tail pads with toe pads. 

Gekkotan lizards of the genusHemidactylusexhibit derived digital morphologies. These include heavily reduced antepenultimate phalanges of digits III and IV of the manus and digits III–V of the pes, as well as enigmatic cartilaginous structures called paraphalanges. Despite this well‐known morphological derivation, no studies have investigated the development of these structures. We aimed to determine if heterochrony underlies the derived antepenultimate phalanges ofHemidactylus. Furthermore, we aimed to determine if convergently evolved paraphalanges exhibit similar or divergent developmental patterns. Herein we describe embryonic skeletal development in the hands and feet of four gekkonid species, exhibiting a range of digital morphologies. We determined that the derived antepenultimate phalanges ofHemidactylusare the products of paedomorphosis. Furthermore, we found divergent developmental patterns between convergently evolved paraphalanges.

 

Lycodon alcalai is a small, terrestrial snake endemic to the northern Philippines where it is known from the islands of Batan (70 km2), Sabtang (16 km2), and Calayan (196 km2; Ota and Ross 1994. Copeia 1994:159–174; Oliveros et al. 2011. Sci. Pap. Nat. Hist. Mus. Univ. Kans. 43:1–20). Although L. alcalai has been reported to prey upon Common Tree Frogs (Polypedates leucomystax) and unidentified, soft-shelled reptilian eggs (Ota and Ross 1994, op. cit.), little natural history information is available for this species. Here, we report on a new diet item for L. alcalai: an as of yet undescribed species of scaly-toed gecko (Lepidodactylus).