Importance Of Nails In Primates

Title: Nails in primates: Introduction, evolution and significance.

Introduction:

Nails along with few other characteristics differentiate primates (refer to the endnote for classifications in primates), which include “any mammal of the group the lemurs, lorises, tarsiers, monkeys, apes, and humans” (From Britannica encyclopaedia) from other mammals. Even though few spices in marsupials have nails it merely is an exception and also indicates convergent evolution . And not all species in primates have nails. Daubentonia madagascariensis (commonly known as Aye-aye) of the family Daubentoniidae has claws on all its fingers. All the species of the family Callitricidae, have claws on all their fingers except the hallux , which has a toilet

And then the for microscopic analysis the nails were decalcified and were cut into sections of different thickness stretching from 7 μ to 10 μ and were stained with haematoxylin and azan . For histological study, the 1st and the 4th digit were used from species lacking toilet claw and 1st, 2nd, 3rd and 4th digit from species with toilet claw. The 5th digit was never examined in any species because the 4th digit always represented the 5th digit in primates.

To check the minimum number of changes required to make a claw into a nail or toilet claw the results from histological studies were compared to the phylogenetic tree of primates.

Results:

1. All the species except Daubentonia madagascariensis and the species in Callitrichidae lack functional claws.

2. All strepsirhines including D. madagascariensis have a toilet claw on 2nd digit of the foot.

3. All the analysed species of Neotropical primates have both deep and superficial layer irrespective of whether they were claw or nail shaped breaking the older structure proposed by Le Gros Clark that nails do not have a deep layer. Three out of five analysed species of old world monkeys, all apes except hylobates and humans had a deep