GROUP 3

The development of an unfertilized egg into an adult

organism. Activation of development normally occurs after an

egg is fertilized by a sperm; in parthenogenesis, however, the

stimulus for the egg to cleave occurs spontaneously or can be

induced experimentally. The mechanism or events occurring

during egg activation are not known but apparently include

certain changes in the egg membrane

• . In a female, an egg undergoing the first

meiotic division produces two cells, both of

which contain a diploid number of

chromosomes. One of these cells atrophies; in

this state it is known as the first polar body

and remains attached to the other cell.

Parthenogenic activation occurs at this stage

of development.

The self-induced releasing of a specific body part. In certain

lizards, it is the tail that autotomizes; in plethodontid salamanders

(terrestrial salamanders lacking gills and lungs in the adult form), it

is their tails, digits, and portions of their limbs.

•Lizards do not autotomize their digits or

limbs. If your lizard's toes have are falling

off, this is a serious medical problem that

requires veterinary attention now. In a

few lizards, it is pieces of skin that

autotomize, a defense strategy known as

"fragile skin."