Question

Retia mirabilia specially in thoracic region are extensively developed in
A. Artiodactyla
B. Perrisodactyla
C. Cetacea
D. All of the above

Answer 1

Hint:-A rete mirabile is a complex of arteries and veins found in some vertebrates, primarily warm-blooded ones, lying very close to each other. The ocular rete mirabile is supplied with arterial blood only indirectly, via a special organ.

Complete answer:
The rete, which serves the retina, is called the mirabile choroid rete. Vessels of similar diameter have the retia supporting the eyes and the swimbladder, but the vessels of the rete choroid are narrower. In order to fulfil the high metabolic demand of the avascular retina, the rete produces a high oxygen partial pressure for diffusion. The retina is well vascularized in most other vertebrates, with an abundant supply of capillaries to provide oxygen to the metabolically active tissue.
The retina is well vascularized in most other vertebrates, with an abundant supply of capillaries to provide oxygen to the metabolically active tissue. The retina is not vascularized in fish and oxygen demand must be met over wide distances through diffusion, hence the need for a high partial pressure of oxygen. The distance over which oxygen has to be diffused is approximately 6 times greater than in mammals. Therefore, most fish, but not all, have a rete behind the retina. The choroid rete lies at the back of the retina inside the eyeball in the retinal cells of the choroidal layer. The ophthalmic artery, one on either side of the retina, is divided into two branches. Many smaller arteries branch off from the main ophthalmic artery and subdivide to form the choroid rete's small vessels many times. The larger choriocapillaris vessels that provide oxygen and nutrients are formed.
When a complex structure is created by the arteries and veins lying very close to each other, it is known as a rete mirabile, found in some vertebrates. In the thoracic zone, the retia mirabilia of cetaceans is seen as one of the morphological adaptations that modulate hemodynamics during diving and resurfacing.
Hence, the correct answer is (c) Cetacea.

Note:- A full aquatic order of mostly marine Eutherian mammals consisting of whales, dolphins, porpoises, and related forms, all of which have a very large head, a tapering body like a fish and almost devoid of hair, forelimbs like paddles, no hind limbs, a tail ending in a wide horizontal fin, a large brain, a complex stomach of four or more chambers, and two posterior mammae in place.