Skin Deep – Judging Nature’s Book By Its Cover
The cells that together comprise the surface of living things perform a variety of functions, all critical to survival. Quite apart from being, literally, the organ that holds invertebrates together, the integumentary system plays an important role in homoeostasis. This includes the overall protection of vulnerable internal organs, regulation of body temperature, sensory perception and the synthesis of crucial biochemical compounds.
1. Nettle caterpillar of a Limacodid moth – Isaac Kehimkar
This slug-like caterpillar has a bush of hairs or spines, capable of a painful nettle-like sting – hence the name. An adhesive belly makes up for the lack of prolegs. Newly-hatched caterpillars congregate on leaf undersurfaces. The spines and gaudy aposematic (warning) colouration serve to discourage predators.
2. Leopard: Panthera pardus – Anish Andheria
Every mammal has hair or fur. The leopard’s dark spots on a yellow background camouflage it under the dappled canopy that is its home. The spots are scattered on its flanks, head and legs and are set in small groups or rosettes on the back. No two skins are alike and the spots of the African leopard are smaller than those of the Asian subspecies.
3. Cross crab: Charybdis cruciata – Isaac Kehimkar
The size, shape, architecture, colour, habits and habitat of different families of crabs vary widely. In a typical crab, the forepart is covered by a broad shield that is expanded laterally, under which its water-breathing organs or gills are well-protected. In land crabs, the gills function using the moisture in air.
4. Rock gecko: Hemidactylus maculates – Ashok Captain
The trihedral leg scales of this rock gecko are made up of dead cells that will be replaced. Reptile skin aids in camouflage, courtship and aggression display. Transverse rows of supple laminae on the undersides of the digits serve as adhesive pads to enable the lizard to walk upside down and on vertical surfaces. Plate-like scales are largely restricted to the underparts, the soft skin of the back being covered with sparse horny tubercles.
5. Common tortoise-shell beetle: Aspidomorpha milaris – Isaac Kehimkar
Belonging to a sub-family of the leaf beetles, tortoise beetles sport many-hued elytra that extend beyond the lateral outline of the body. No one has conclusively explained why they evolved the transparent shell seen in this image. Perhaps transparency offers protection from attack, while the warning colouration simultaneously deters would-be predators from attacking.
6. Indian chameleon: Chameleo zeylanicus– Isaac Kehimkar
The chameleon’s ability to change colour is a camouflage and defence mechanism. Photo-sensitive skin aids the movement of pigments inside melanophore cells. The colour cells expand and contract under stimuli causing the skin to lighten or darken to suit the background on which it is located. Male chameleons use this capability to great advantage to impress prospective mates.
Single-celled protozoans, sponges, corals and even plants, all have exoskeletons. The armour of crustaceans, such as lobsters, crabs, shrimps and barnacles have an obvious purpose. Some animals, however, turn their skins into cases and tubes within which they are able to live in relative safety. Structural adaptations such as hair, claws, hooves, horns and pads are a part of an animal’s ‘skin’, fabricated by evolution to suit the circumstances in which each creature must survive. So while elephants and rhinos have a thick outer skin, bears and wolves compensate for thin and soft skins by growing fur. Interestingly, in the case of Homo sapiens the skin is the largest organ in the body and makes up just under 15 per cent of the total body weight!
7. Medo pit viper: Trimeresurus medoensis – Ashok Captain
The venomous medo pit viper has a triangular head, thin neck and a long slender body. Patterns and shapes vary widely in the 16 species of pit vipers found in India. Snake skin is covered with scales. Flat belly scales called scutes grip the ground and aid movement, an adaptation that permitted them to abandon the legs they once had. Snakes shed their skins every few weeks or months.
8. Elephant: Elephas maximus – Bittu Sahgal
Elephants and rhinos are both pachyderms (thick-skinned animals). An elephant’s skin may be as thick as 5 cm.Around their ears however, it is thinner to allow them to fan their ears to dissipate heat. Mud wallows, water and dust baths are used to care for the skin and to regulate body temperature.
9. One-horned rhino: Rhinoceros unicornis – Thakur Dalip Singh
The ‘armour plated’ skin is one of the rhinoceros’ most striking characteristics. A uniform grey-brown colour, the skin also has deep folds around the neck and is studded with tubercles or granules. Despite its crude appearance, the rhino’s skin is extremely sensitive and the animals are greatly troubled by mites and infestations, hence their love of mud, which soothes and protects them.
10. Moulting grasshopper: Orthoptera – P. Karunakaran
The cuticular exoskeleton made of chitin moults in grasshopper nymphs periodically, when the old cuticle is detached from the epidermis and partially digested by enzymes. A thin cuticle is already laid down beneath the old one. Pigments present in and under the cuticle provide the protective camouflage colouration.
Sanctuary Asia, XXI No. 6, February 2001.