Question

The tadpole of Herdmania exhibits:
a. Absence of notochord
b. Retrogressive metamorphosis
c. Absence of tail
d. None of above

Answer 1

Hint: The Herdmania is an organism belonging to the genus of Ascidian tunicates in the family of Pyuridae. This organism is an inactive filter feeding tunicate that is found in marine habitats and are gregarious in nature, that is they socialize among themselves.

Complete answer:
Herdmania are filter feeders, (filter feeders are the organisms that feed by straining the suspended matter and food particles from water by passing the water over a specialized filtering structure). It is a hermaphrodite animal that is capable of producing male and female gametes by its own. The fertilized eggs undergo holoblastic unequal cleavage and develop into blastula. After its development and differentiation, a tailed larva is produced called Ascidian Tadpole larva.

This larva has a length of 3mm and a tail with a short oval body. This larva exhibits all chordate characters. Some of the features are, body covered with thin test (covering), long tail with caudal fin and tail is supported by presence of notochord, hollow nerve cord is present, muscles help in locomotion, digestive system present with pharynx and few gill slits, muscular heart is present for blood circulation and three adhesive papillae are present which help the larvae to attach to substratum.

Since the tadpole exhibits all chordate characters, this larva undergoes retrogressive metamorphosis to further develop into adult Herdmania. In retrogressive metamorphosis, the larva of that organism possesses some of the main characters that are lost when they enter the mature state. The advanced features that are present during the larval stage or juvenile stage are lost during its development and the adult stage is immobile or sedentary.

Hence, The correct answer is option (B).

Note: The Urochordate adults are sedentary (they are characterized by much sitting and little physical exercise) and show degenerative characters, on the other hand the tadpole is free swimming organism which exhibit advanced chordate characters which are lost during the stage of metamorphosis.