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#ascidians

2 public questions tagged with this topic.

Larva of urochordates shows chordate characters in

Urochordate tadpole larva demonstrates regionalized chordate character expression. Anterior head-trunk houses sensory vesicle with ocellus and otolith, endostyle for feeding and pharyngeal slits, whereas caudal tail comprises notochord providing stiffness, dorsal hollow nerve cord, segmental striated muscles for sinusoidal swimming and fin. Metamorphic settlement involves tail absorption, notochord degeneration and rotation of visceral organs. Confinement of chordate support and locomotor structures to tail highlights functional compartmentalization for dispersal phase, contrasting with cephal

Ref: Brusca & Brusca, Invertebrates, 3rd ed., Urochordata Larva; NCERT Class 11, Chapter 4, Protochordata

Subphylum Urochordata includes

Subphylum Urochordata, synonymous with Tunicata, includes marine filter feeders like Herdmania, Ciona, Salpa, Doliolum and Pyrosoma encased in secreted tunic composed of tunicin resembling cellulose. Adults are sessile, sac-like with incurrent and excurrent siphons, lacking notochord, dorsal nerve cord and segmented muscles due to retrogressive metamorphosis where tail resorbed. Free-swimming tadpole larva retains chordate features for dispersal. Cephalochordata contains Branchiostoma amphioxus, Agnatha contains lampreys, Chondrichthyes sharks and bony fishes. Tunicate classification emphasize

Ref: NCERT Class 11 Biology, Chapter 4: Protochordata – Urochordata; Brusca & Brusca, Chapter 23, Tunicates