Tarentola chazaliae (Mocquard, 1895)

Nomenclature

This species is scientifically named Tarentola chazaliae (Mocquard, 1895), commonly called the helmethead gecko.

Size

Adult helmethead geckos reach a snout-to-vent length (SVL) of 7.5 cm (3.0 in), with a total body length of approximately 11 cm (4.3 in).

Head Structure

Their head is covered in small granules, and the enlarged tubercles on the back of the head form a casque structure.

Digit Morphology

The gecko's digits are flattened and shaped like spatulas.

Coloration

Dorsally, individuals range in color from light grey to dark brown, and can be uniformly colored or marked with pale or dark blotches; their underside is light in color.

Activity Pattern

Ecologically, Tarentola chazaliae is primarily nocturnal.

Visual Adaptation Background

Most diurnal lizards have lost the retinal rod structures typical of vertebrates, retaining only cones for vision, but this gecko has further adapted its eyes to maintain some degree of color vision in low nighttime light.

Optical System

It has evolved a multifocal optical system that allows it to distinguish between light of different wavelengths.

Pupil Morphology

The gecko's pupils are circular at night, but contract into a pair of pinhole-sized pupils per eye during the day.

Pupil Function Hypothesis

The exact function of this pupil shape change is not confirmed, but it has been hypothesized that the pinhole form makes the gecko less visible to potential predators while it basks in sunlight.

Low-Light Vision Capability

Helmethead geckos are the first vertebrates confirmed to be capable of color vision in very low light conditions, and their acute nighttime color vision is 350 times more sensitive than that of humans.