Question

Trochophore larva is found in
A. Annelida and Mollusca
B. Annelida and cnidaria
C. Annelida and Ctenophora
D. Annelida and Arthropoda

Answer 1

Hint: Larva is a stage of development in many organisms after their birth and before they reach their adult stage. These structures are different from both the adult forms and the post birth forms. The development of the adult form from the larva is termed as metamorphosis and is observed in many insects and amphibians. In many cases the larva adapt to different environmental conditions as compared to the adult forms.

Complete answer: The term trochophore is derived from Greek words trichos and phero which means wheel and to bear or carry respectively. Trochophore larvae are described as small, un-segmented, translucent having broad anterior end and narrow posterior end and are free swimming larvae that are found in marine forms of many organisms. These larvae contain a ring of cilia around them also known as the prototroch that helps them to swim. Below the prototroch are located the mouth, anus and other organs that help to maintain proper salt and water concentrations in them. They complete their development in three stages- the early trochophore, complete trochophore and late trochophore. Their mode of nutrition is mainly planktotrophic. Trochophore larvae are most commonly found in Mollusca and Annelida.

So the correct option is A) Annelida and Mollusca.

Note: Many organisms cannot develop into their adult forms just after birth and hence go through various developmental stages. These stages are better suited to their surrounding environment and thus help in their proper growth and development which is why larval stages are important in organisms.