There are over 1700 known species, all inhabiting the sea-bed, mostly in deep waters, but can be found on the continental shelf in many areas.
An echinoderm (alongside sea-urchins and starfish), belonging to the family Holothuroidea, they distinguish themselves from sea urchins by "lying on their sides". They're radially symmetrical ...
Aquatic insect comprising 6 subfamilies and 55 genera. (The Wikipedia page's right-hand panel contradicts the detail below that).
Size 2 - 15 mm long (0.1 - 0.6 inches), six legs, the front pair are hairy and shaped like oars. Feeding on aquatic plants and algae they range worldwide except Antarctica.
If I couldn't guess from the ...
Thermoregulation and echolocation both depend on evolutions that occurred on land and seem to be less accessible to fish than to the ancestors of mammals. The heat capacity of water is much greater than air, so maintaining an elevated temperature in body tissues is both more difficult and less necessary. Still, some fish lineages have independently evolved ...
Advantages of air breathing over gills? Keeping in mind water-breathing animals could still evolve lungs.
Not being vulnerable to parasites and diseases of the gills, which are obliged to have blood supply close to the water.
Able to colonise water regardless of salinity, able to survive warm water.
This is a "sand hopper" (Talitridae), also known as "land hoppers" or "sand fleas". The Talitridae are a cosmopolitan family of arthropods, known for their hopping behaviour when disturbed.
Which of the genera it is from would be impossible to determine without detailed close-up pictures and a bit of expert knowledge which is ...
No, there isn't a perfect link between eye colour and behaviour
The full claim, as reproduced here is as follows:
Yellow eyes point to day-active species, such as little owl.
Orange eyes indicate that the species is active at dusk and dawn, such as
long-eared owl (Asio otus).
Black eyes are for night-active species, such as tawny owl (Strix aluco).