Sense Organs in Aurelia (With Diagram) | Phylum Cnidaria

In this article we will discuss about the sense organs in aurelia, explained with the help of a suitable diagram.

i. Sense Organs:

The sense organs include the olfactory pits, the ocelli and the tentaculocysts or rhopalia.

ii. Olfactory Pits:

Two, lined with sensory epithelium—one lie on the ex-umbrella and the other in the sense club. These are chemoreceptors and recognize the food.

iii. Ocellus:

An ectodermal pigment spot sensitive to light is present on the outer side of the sense club.

iv. Rhopalia:

These are modified tentacles, hence known as tentaculocysts. Four par-radial and four inter-radial rhopalia (Fig. 20.20) are present in the eight marginal notches.

 

a. Each rhopalium consists of a hollow club-shaped projection, called statocyst or lithostyle.

b. The statocyst remains covered over by a hood-like process of the bell margin, con­necting a pair of lateral marginal lappets.

c. The statoayst is a specialised hollow tentacle enclosing a prolongation of the cir­cular canal lined by gastro dermis. The apical gastro dermal cells contain otoliths or sta­toliths, made of calcium sulphate.

d. The rhopalia are the organs of equilib­rium. They also control the rhythmic swim­ming movements of the bell.