Biology of the geckos

The geckos are reptile S, and more precisely of the squamate S. They belong to the group of animals than one calls “Lézard” in the language running.

As a family of reptiles they are very adaptable, and one meets these animals in very many countries, such as those of the equatorial zones , tropical and moderate, as well in Désert S, bush, wet forests, mountainous areas…

Certain species of an easy breeding and being very coloured one meets some of these animals in the breedings of terrariophiles, which explains why they are relatively known of the public.

General information

The geckos, like all the reptiles, are Poïkilotherme S, i.e. their body temperature varies according to the conditions extérieures.
That does not want to say that these animals tolerate any Température. They have a préférencielle body temperature, where them organization functions as well as possible. In on this side minimal temperature, certain biological functions are disturbed, like the Digestion or the immunizing defenses, and in on this side temperature criticizes they die. Symmetrically beyond a maximum temperature their organization packs and they also end up dying.

They thus will adopt a behavior aiming at maintaining their temperature in an adequate beach, while being exposed to the sun or on the contrary in of protégeant.
These préférencielles, minimal and maximum temperatures vary enormously according to the species. The geckos alive in the deserts can tolerate higher temperatures with 35°C, whereas those living of the more moderate areas tolerate higher temperatures with 30°C with difficulty. In the same way the tolerated minimal temperatures can vary 20°C for highest with a few degrees with the top of zero for lowest. In the areas subjected to Winter S, the geckos can have one period of rest, where them activity is strongly reduced, and to sometimes even enter in hibernation for the hardest climates.

Morphology

The geckos, like all the reptiles, are Quadrupède S. They have a lengthened body, with a rather large head compared to the volume of the body. The junction between the body and the head is quasi absent. All the geckos are equipped with a tail whose morphology is very variable according to the species: more or less long, fine or thick, applatie, with scales fine or apparent. The near total of the geckos are capable of Autotomie, loss voluntary of the tail in order to escape a predator. The tail pushes back then, but generally with an aspect and degraded characteristics, and this faculty decreases with the age and the number of push back. Moreover at certain species the tail is used as reserve of grease ( kind of the Eublepharis for example) what can be fatal in period of disete.
The lower part of the body is in general clear, with scales crossing all the belly laterally, as at the snake s.
The legs very side, are anchored on the bottom of the body. The high part goes up along the body, then goes down again and ends in legs equipped with five fingers. Those can be of form very varied according to the medium of life: very broad (arboricolous in general), very fines, lengthened, sometimes webbed (walk on sand). All are equipped with generally retractable claws. Gecko has Crete will never find their tail… cest the only species which does not push back and curiously cest lespece which it PERT most easily!!

Behavior

Skin

As for the others Lizard S, the Peau of the geckos is covered with scale S. According to the species, the scales are fine and punts, almost invisible, with a glossed aspect. They can also be rather large and thick, to even form small bumps or prickles. They do not reach however the variety of form of other lizards as at some chameleon S, agamous S or others Iguane S.

The skin of the geckos can take very many colors, and certain species present of them very sharp and very contrasted as at the Phelsuma . One meets thus white, beige, all the colors of brown, green, blue, yellow, black, orange.
The reasons formed by these colors are also varied. One thus meets stripes, points, spots, lines and dégradés.
Certain species became Master in the art of the camouflage, adapting the colors and reasons for their environment. Most spectacular in this field being undoubtedly the Uroplatus whose colors, reasons and form itself imitate the sheets ( Uroplatus phantasticus ), the lichen ( Uroplatus sikorae ), barks…

It should be noted that the majority of the geckos can become more or less dark according to their requirements in heat (mechanism allowing to absorb heat more or less).

The moult

The moults is a phenomenon of renewal of the skin of the animal, this one not growing at the same time as lui.
The geckos grow all the life during, even if this growth slowed down once adult. With regular intervals the skin becomes too small and falls apart of the body. The duration of the moult is variable according to the age, of the species, the health condition and the external conditions. The moult complête can take of one or two days at more than one week. The skin is detached by large scraps, in general initially on the level of the head and the body, then of the tail and the legs. The transparent scale of protection of the eyes also moults, which can cause a fall of the vision during the duration of the mue.
Certain species consume the skin progressively. The assumptions as for the cause of this behavior are the recovery of nutrients present in the skin, or a technique of acceleration of the moult.

Several problems can appear during the moult. For the species living in moist environment a too weak Hygrométrie disturbs the separation of the skin, lengthening the total duration of the moult. This lengthening also occurs when the animal is in bad health or is not hot enough, because of the deceleration of the renewal of the news peau.
The problems of moults are not generally serious in themselves but they disturb the life of the animal, by obstructing its sight or its movements, and for the arboricolous species by reducing the effectiveness of the setæ and thus by limiting their capacity of climbing.

Setæ

A great majority of the species of geckos is arboricolous. They have under the fingers of the setæ which enable them to climb any surface (including panes or to go the upside down). In fact microscopic hairs offer to them a very large adherence thanks to the forces of Van der Waals which are exerted between the end of these hairs and the objects, at the molecular level .

Sensors and nervous system

Sight

The geckos are equipped with a good sight and they perceive the colors. Their eye can take two forms according to the species:

a round Pupil, adapted to the diurnal vision;
a vertically split pupil, as in the cats for example, for the night species.

The eye is almost deprived of white, and the color of the iris is very variable according to the species: gray, chestnut, orange, gilded, rosy. The iris often presents reasons, in the form of darker scratches or fine lines.

It should be noted that, like the snakes, the true geckos are deprived of Paupière S and have a transparent scale which protects the eye. This is not the case of the animals of the Sous-famille of the Eublepharinae which them have eyelids, contrary to the other subfamilies.

Hearing

The geckos are equipped with excellent a hearing. They perceive sound frequencies on a very wide range (to be specified).

Sense of smell

Like the other lizards, the geckos can feel the odors thanks to a specific body: the body of Jackobson.
They collect the odorous molecules on their language (they then give the impression of “lêcher” the air) and pose them in contact with this body which plays the same part then as the sense of smell at the Mammifère S.

Contrary to the majority of the lizards, the language of the geckos is not bifide (language “fourchue” of the snakes and lizards) but fleshy, generally pink more or less dark.

Touched

The direction of touched is developed relatively little at the geckos. They have a good sensitivity to the level of the mouth and language, but the remainder of the body is little sensible.
They are moreover conditioned by their environment and cannot sometimes identify unusual stimulis. It is for example the case of the heat which comes only seldom from the ground in nature. Some geckos were thus burned on the ventral face while being posed on an extreme object, without having the reflex to move.

The nervous system

Other bodies

The heart

Lungs

The digestive system

The reproductive system

The large majority of the geckos lays eggs and is thus oviparous animal. Certain species are however ovoviviparous S, i.e. the eggs are preserved inside the female until blossoming. This is in general the case for the species living in rather cold medium, where the eggs would have little chance to finish their development only.

The males geckos are equipped with two Hémipénis (as in the snakes). It is about a double penis, each one being placed in a housing at the base of the tail, close to the Cloaque. Only one of these hémipénis serves at the time of the reproductive act, in order to deposit the Sperme in the Cloaque of the female. The act itself can last of a few tens of minutes to several heures.
According to the species the female will couple itself several times during the season or will preserve alive sperm in it. It can thus fertilize eggs without another contact with a male.

After the copulation the eggs develop during a few weeks in the body of the female. Its requirements in Calcium are then very large and certain species have “bags” containing of the reserves accumulated in preparation for gestation. With the approach of the laying, the females become often agitated and seek a sure place to deposit eggs. They can also cease feeding, the compressing eggs the ways digestives.
The majority of the females lay two eggs at the same time. Those according to the species deposited on plants, buried in the ground, are hidden in cracks… Certain species stick their eggs on a support.
Fruitfulness varies much from one species to another. The least prolific lay from four to six eggs per season, figure which can exceed ten eggs for most productive.

Eggs

The eggs are round or slightly ovoid. Their size varies between one and two centimetres diameter according to the espèces.
Certain eggs have a hard shell, relatively thick, and others are fine with a semi-flexible envelope. The first generally correspond to species living in dry and/or cold medium, the shell insulating the Embryon.
During its development an air pocket is formed in top of egg. The embryo is connected there and uses it to feed out of oxygen. Beyond a certain development the reversal of egg can break this pocket or take down the embryo, with for consequence the death of this one.

According to the conditions and the species the eggs incubate between three weeks and nearly two months. At some geckos the temperature determines the sex of small (at many Phelsuma for example). At an intermediate temperature (variable according to the species) the proportion of males and females is balanced. With beyond and in on this side this temperature this proportion leans in favor of the one of the two kinds. It seems that at certain species - still Phelsuma - other criteria also influence the sex of small.

Sexual dimorphism

The sexual Dimorphisme is the difference of aspect, size and behavior which present male and females between them.

These differences vary enormously between the species. Most current are:

size. Most of the time the male is a little taller than the female, and generally a little more massive also. There exist however exceptions, the females being largest (thus the female Aeluroscalabotes felinus can reach 16 cm whereas the male seldom exceeds 12 cm).
the bulges hémipéniens. These are in the males of the side bulges at the base of the tail which correspond to the housing of the Hémipénis. At certain species these bulges are on the other hand invisible.
pre-anal and femoral pores. In fact pores appear close to the cesspool or along the thighs by which the males produce a substance generally being used for marking of the territory. These pores are in general absent or definitely smaller in the females.
colors. For the majority of the species the females are duller. They have colors minus sharp, sometimes even one delivered completely different (several species of Phelsuma for example).

According to the species one or more of these differences will be visible, with more or less marked degrees.

Dependant articles

the general article on the geckos;
the family of the geckonidé S (biological classification);
the Lizard S, the squamate S, the reptile S;
New pets (NAC), the Terrariophilie.

References

Atlas of the terrariophile Vol.3: the lizards . Animalia Editions, 2003. ISBN 2-9517895-2-1
Philippe Gerard, the breeding of the diurnal geckos and Uroplatus . Philippe Gerard editions, 1998. EAN 97822912521125. ISBN 2-912521-12-2

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