Stingray fish

These fish are widely distributed in oceans and rivers. Stingrays are members of the elasmobranch family a family of fish that includes sharks, marine and freshwater rays and sawfish.

It is a broad, flat fish with a long, whip like tail that may have one or more stingers with barbed ends.

Elasmobranch fish are unique in many ways. They do not have scales; in the place of scales, their skin has dermal denticles, giving it the texture of fine sandpaper. They do not have calcified bones; instead, their skeleton is composed of cartilage.

Stingrays bury themselves in the sand of shallow water, where they can be easily steeped on inadvertently.

The large barbed spine may cause severe and even fatal lacerating injuries, usually to the lower part of the legs but occasionally penetrating the body cavities, heart and viscera when the swimmer falls and lies on, or even swim over the fish.
Stingray fish

Temperature of the seas

Temperature of the seas
The seas and oceans have a very large heat capacity; hence, they’re not very susceptible to rapid temperature changes.

Usually the surface temperatures of sea waters range from about 28 to -25 degree C. Areas of exceptionally high temperature such as the Persian Gulf 36 degree C, are rather rare.

The temperature of the sea waters depends on the latitude, water currents the season and the depth.

Only in the surface layers influenced by the weather conditions, do the changes temperature take place within a few hours,.

In deeper waters, seasonal cycles of temperature are noticeable while at great no fluctuations in temperature take place.

The influence of temperature in the biological life in the seas is both direct and indirect.

The temperature affects the solubility of oxygen in the sea water and the intensity of the metabolism of the organisms.

Many marine organisms are very well adapted to fluctuating environmental conditions, while other can live only within a very limited range of temperatures.

The stenothermic drifting plankton organisms perish instantaneously on being brought with the sea currents into areas of very different temperature.

Such zones of convergence of warm and cold waters usually abound in nutrient, originating from mineralization of dead animals or plants.

The water temperature is one of the most essential factors affecting the distribution of fish in the seas.

Favorable thermal conditions are especially important for the development of the fertilized eggs. The density of the sea water depends on the salinity and temperature, influencing in turn the vertical distribution of the eggs.

Cold waters are generally more fertile than warm seas and are inhabited by a comparatively small number of species, reaching vast populations in years of favorable hatching and feeding conditions.

On the other hand, warm water seas are generally the habitat of many species competing for food, These species usually do not form large populations.
Temperature of the seas