At what point in vertebrate radiation does the swim bladderl

Solution

Ques-1: At what point in vertebrate radiation does the swim bladder/lung develop?

The genes responsible for the generation of “embryonic organizer” are gene “Goosecoid” and the ventral genes Vent1 and Vent2 in case of vertebrate fish models (Zebra fish) for gastrulation. In case of vertebrate mouse models Goosecoid –organizer specific genes are essential for mesodermal patterning at the time of gastrulation. For example, during embryonic development, vertebrate radiation does the swim bladder/lung to develop as an “oupocketing extension from gut” during gastrulation & this extension continues in vertebrate fishes as the primitive pneumatic duct (ex. ray-finned fishes) for breathing activity

Ques-2: Is phystocliestous or physostomous more ancestral?

Physostomous are more ancestral than Physoclistous because these are primitive ancestral teleosts evolved from bony fishes, which possess swim bladder as respiratory organ mainly in the fish species such as eels, salmons etc. The additional organ is “swim bladder” in the teleost fish shares a similar function to that of the liver in the elasmobranchs in which swim bladder is absent. The functions of swim bladder in tuna, teleosts is to promote buoyancy through monitoring gaseous exchange in the water currents when teleost is going to move ascend or descend inside the water. Elasmodbrachs do not possess swim bladder but possess liver to generate liver oil to maintain buoyancy in the deep sea.