Retrogressive metamorphosis is found ina)Hemichordatab)Urochordatac)Ce...
Metamorphosis is a change from the juvenile to adult stage in which larval stage is quite different from the adult stage. In retrogressive metamorphosis the larva possesses advanced characters which are lost during the development and the adult is either sedentary or degenerated with primitive characters. Urochordate adults, being sedentary show degenerative characters while the free swimming tadpole larva shows advanced chordate characters which are lost during metamorphosis. Parasitic crustaceans, like Sacculina and copepod parasites and stylopids and scale insects (Insecta) also show retrogressive metamorphosis.
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Retrogressive metamorphosis is found ina)Hemichordatab)Urochordatac)Ce...
Metamorphosis is the phenomena in which there are changes which transform the organism from its juvenile stage to adult stage. In the case of retrogressive metamorphosis, the larva possesses the advanced features which get lost during the development. The adult is sedentary or degenerated with the primitive characters. Retrogressive metamorphosis is a characteristic of ascidians. They are from the group of Urochordates or Tunicates. The active and alert larva metamorphoses into a retrograde and sedentary bag-like creature. The adult remains attached to a rocky substratum.
Thus, the correct answer is option B.
Retrogressive metamorphosis is found ina)Hemichordatab)Urochordatac)Ce...
Urochordata
Retrogressive metamorphosis is a process seen in the class Urochordata, also known as tunicates or sea squirts. This phenomenon involves the regression of complex structures and functions in the adult form compared to the larval form.
Explanation:
- In Urochordates, the larval form, also known as the tadpole larva, possesses a notochord, dorsal nerve cord, and a post-anal tail, resembling characteristics of chordates.
- However, during metamorphosis, the tadpole larva undergoes retrogressive changes where it loses its notochord, nerve cord, and tail.
- The adult Urochordate, which is sessile and filter-feeder, bears little resemblance to its larval form and shows a simpler body plan.
- This simplification of body structures and functions is known as retrogressive metamorphosis.
- The process of retrogressive metamorphosis in Urochordates reflects adaptation to their sedentary lifestyle as adults.
Therefore, retrogressive metamorphosis is a characteristic feature of Urochordates, distinguishing them from other chordates such as Hemichordates, Cephalochordates, and Cyclostomata.
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