What is top shell?

Top shell, any marine snail of the family Trochidae (subclass Prosobranchia, class Gastropoda), characterized by a spiral, conical shell. Tropical top shells such as Trochus, Tectus, and Cittarium tend to be larger and more colourful than the genera from other regions.

What adaptations do limpets have?

Limpets have adapted to survive the intertidal zones of the rocky shore. Their strong foot muscle attaches the shell to rocks, preventing desiccation at low tide, and anchors the animal in rough seas. Molluscs on the rocky shore are mostly univalved (one shell).

How do intertidal animals cope with desiccation?

How do animals cope with the stresses of drying out? Apart from animals that live permanently attached under large stable boulders, all intertidal animals have adaptations for either holding a reservoir of water and/or reducing the loss of water while the tide is out.

How do Chitons prevent desiccation?

The air seal is produced when the chiton’s shell is pressed down against the rock hard enough to not let any air in or out. The air in the chiton’s air seal is very moist and damp. The damp air comes from the fleshy underside of the chiton, and prevents the chiton from drying out during low tide.

Which is the best definition of dark adaptation?

Definition of dark adaptation. : the process including dilation of the pupil, increase in sensitivity of the retinal rods, and regeneration of rhodopsin by which the eye adapts to conditions of reduced illumination. Other Words from dark adaptation Example Sentences Learn More about dark adaptation. Keep scrolling for more.

How does dark adaptation affect receptive field size?

Dark adaptation reduces coupling (from space constant determinations, tracer coupling), smaller receptive-field sizes (surround-to-center ratio), and decreased sensitivity of horizontal cells. Ron Ofri, in Slatter’s Fundamentals of Veterinary Ophthalmology (Fourth Edition), 2008

Which is the best description of a top shell?

Join Britannica’s Publishing Partner Program and our community of experts to gain a global audience for your work! Top shell, any marine snail of the family Trochidae (subclass Prosobranchia, class Gastropoda), characterized by a spiral, conical shell.

When is a small test spot used during dark adaptation?

When a small test spot is used during dark adaptation, a single branch is found as only cones are present at the fovea. When a larger test spot is used during dark adaptation, a rod-cone break would be present since the test spot stimulates both cones and rods.