Larva of Herdmania is

(a) Muller’s larva

(b) Tadpole

(c) Tornaria

(d) All of the above

Herdmania, commonly known as sea squirts, is a hermaphroditic animal belonging to the genus of ascidians. Fertilization in Herdmania occurs externally, and usually, cross-fertilization takes place.

After fertilization, the eggs undergo holoblastic and unequal cleavage, leading to the formation of a blastula. This blastula consists of upper micromeres and lower macromeres. Through the process of gastrulation, the blastula develops into a gastrula, which later transforms into a tailed larva known as the ascidian tadpole larva.

The ascidian tadpole larva:

• Measures about 1.5 mm in length.
• Is motile and covered by a thin tunic secreted by the ectoderm.
• Has a short oval head and a long posterior tail.
• The tail bears a caudal fin, an oval body, and contains a notochord with muscles on one side.

This larva actively swims in search of a surface to attach to. For its free-swimming lifestyle, it shows all the fundamental chordate features. However, during development, it undergoes retrogressive metamorphosis, losing its advanced features as it transforms into the sedentary adult form of Herdmania.

Hence, the correct answer is: ‘tadpole’.