Question

Regeneration of Hydra is
A) Morphallaxis interstitial cells
B) Epimorphosis by interstitial cells
C) Epimorphosis by archaeocytes
D) Epimorphosis by granular cells

Answer 1

Hint: Regeneration in Hydra is polarized and doesn't depend upon growth. When cut into two halves, the lower piece will develop into a head & the upper will develop into a foot.

Complete answer:
Hydra is an organism belonging to the phylum of cnidaria in the kingdom of animalia. It has a hollow tube-like body (0.5 cm long), with tentacles around its mouth (hypostome) and, at the other end, a basal disc is present(foot).
Let us first understand the process of regeneration in Hydra-
In regeneration, the embryo is able to undergo regulative growth when cells or tissues are removed or rearranged. In the adult, regeneration can replace missing parts by growth and remodelling of somatic tissues. Newts have a great capacity for regeneration (i.e. regeneration of lens from iris epithelium). Mammals can regenerate liver & broken bones can mend but cannot regrow lost limbs. Therefore, regeneration in Hydra is by Morphallaxis interstitial cells.

Additional information: Regeneration means the regrowth of a damaged or missing organ part from the remaining tissue. As adults, humans can regenerate some organs, like the liver. If a part of the liver is lost by disease or injury, the liver grows back to its original size, though not its original shape. Every species has the ability of regeneration, from bacteria to humans. For example, hydra perform regeneration but reproduce by budding.

Hence, the correct answer is option A (Morphallaxis interstitial cells)

Note:The hydra and hence the planarian flatworm have served for a long time, as model organisms for it's highly adaptive regenerative capabilities.