Question

Osculum occurs in

A.Star fish
B.Ray fish
C.Hydra
D.Sponge

Answer 1

Hint: Wastes spread through the bath and the water is pumped into the osculum, taking the sponge's waste along with it.

Complete answer:
First we should know about osculum to answer this question. The osculum is an excretory organ, a wide opening to the outside from which the water current escapes after flowing through the spongocoel.
 Now, let us find the solution from the options-
- Starfish or sea stars belong to class Asteroidea and are star-shaped echinoderms. Popular use also finds that these names, which are correctly related to brittle stars and basket stars, are often attributed to ophiuroids. Because of being in the class Asteroidea, starfish are also classified as Asteroids. Starfish belong to the Echinodermata phylum. Thus, option A is not the correct option.
- Ray, one of the shark-related cartilaginous fish of the Batoidei order, was classified with them in the Chondrichthyes class. There are 534 species included in the order. Ray Fish is a member of the Chordata phylum. Thus, option B is not the correct option.
- Hydra is a genus of minute, fresh-water species in the Cnidaria phylum and Hydrozoa class. The temperate and tropical areas are native to them. Because of their regenerative capacity, biologists are highly interested in Hydra-they do not appear to die of old age, or even to age at all. Thus, option C is not the correct option.
- As a sister of the Diploblasts, Sponges, members of the phylum Porifera, are really a basal Metazoa clade. These are multicellular species that have structures full of pores that cause water to flow through them, composed of jelly-like mesohyl placed between two thin cell layers. Nervous, metabolic or circulatory processes do not occur in sponges. Instead to receive food and oxygen and to eliminate waste, most rely on maintaining a steady water flow via their bodies. Via Ostia, water joins the body of sponges and leaves via osculum.

Hence, the correct answer is option (D)

Note: Sponges pump huge amounts of water: every five seconds, usually, a volume of water comparable to the body size of the sponge is drained. Contractile myocytes control the size of the osculum. In essence, its size is one of the variables that define the quantity of water flowing via the sponge. In addition to excess silt in the bath, it can be closed entirely.