Question

The middle layer in the body wall of Porifera is
A. Mesoderm
B. Mesenchyme
C. Mesentery
D. None of the above

Answer 1

Porifera is the first phylum of kingdom Animalia. The body of Porifera is Vase shaped and is completely porous thus, named Porifera. Porifera is sometimes referred to as sponges.

Complete answer: The numerous pores are called Ostia through which water enters the body.
They have one or more large openings called Oscula by which the water exists.
They are multicellular organisms with the cellular level of body organization. No distinct tissues or organs are present.
They have outer ectoderm and inner endoderm with an intermediate layer of mesenchyme, therefore, Porifera are diploblastic.
Mesoderm is the middle layer out of three germ layers in the body of an organism. So, option A is incorrect.
The body wall of a sponge i.e. Porifera consists of two layers, the outer layer is called pinacoderm and the inner layer is called choanoderm, with non-cellular mesenchyme in between. It is the interconnecting proteinaceous gelatinous matrix.
Mesoglea, also known as the mesophyll layer, is present in between the outer and inner layers of the body wall of sponges. It is a non-cellular and gelatinous connective tissue.
The mesentery is a fold of tissue by which organs are attached to the body wall.

So from the above information, the correct answer to the given question is option B.Mesenchyme.

Note: Study of sponges is called spongiology.
Examples for Porifera are Clathrina , Sycon , Euplectella , Hyalonema , Thenea , Cliona , Halichondria , Cladorhiza , Spongilla , Euspondia , etc.