8 Şubat 2013 Cuma

you porn watch



What makes a fish a fish? Fins, scales, gills, living in the water?

Surprisingly enough there are fishes without true fins or scales whose respiration does not rely mainly on "gills", and those that spend a great deal of time out of the water. One trait that all living fishes do have in common however, is that they have body slimes, a mucoid covering on their very outsides. This trait is very important, particularly for properties.

First off, where does this slime come from? The answer is that it originates from dispersed glandular cells, uni- or multicellular in the fish's epidermis. The type and displacement of these glands is of importance in classification. They produce a glycoprotein called mucin which, when mixed water, produces mucus. As an example in the extreme, consider a hagfish (closest family to the Lampreys), Psychedelic Gobies (aka Mandarins, family Callionymidae), or some species amongst the true eels. Hagfishes are particularly slimy; one of their common namses is "slime eel" though they are not closely related phylogenetically to the eels.

One method of capturing Hags is to fill a steel drum with fish heads and/or other offal, puncture this drum and lower it over a boat side on the continental shelf where these fishes are found. Hagfish will squeeze in to the holes in the punctured drum and eat so much they can't squeeze back out when the drum is hauled to the surface. Once captured, there is difficulty preserving the catch. First they must be cleaned of the copious amounts of slime they produce. If you can grab one well enough to stick it in a bucket of clean water, this medium quickly becomes slimy as well. These animals possess large (pea-sized) multicellular slime glands. Ultimately, what has been done to prepare Hagfishes for preservation is to place a batch of these fishs in a hapless researcher's washing machine with jumbo amounts of enzymatic detergent on a continuous rinse cycle. This finally results in a slime-free hagfish ready for formalin preservation.

General Structure of the Skin:

The skin of fishes, like that of all vertebrates (amphibians, reptiles, birds, mammals) consists of two principal layers:

1) Superficial epidermis, and

2) Deeper dermis.

The epidermis in turn consists of two or more layers. The deepest is a series of close-paced, discrete cells called the germinal layer, or stratum germinativum. The outer cells areformed of its daughter cells. There is much variation in the outer cells, depending on the group of fishes being investigated. Body slimes are the products of these daughter cells and their degradation and, as such, are continuously replaced.

The dermis consists of thick connective tissue made up of two basic layers. It is thicker and more stable than the epidermis.

What the Slime Does for Fishes:

The fact that all fishes have these body coverings is some indication of their importance. With either too much or too little of this slimy coat, any fish will soon die. The slime serves three functions for all fishes. It aids in:

1) Osmoregulation/Gas Transport: Slime provides a selective interface to maintain internal/externail ionic balance. One of the reasons freshwater fishes are constantly urinating is their bodies are "saltier" than the water around them and they tend to absorb water. The fish cwauctions.com of this excess water by elimination. The opposite rationale applies to saltwater fishes. In addition to salt balance, the slime plays important roles in dermal respiration. Fish breathe through their skins, as do humans. If the amount or quality of the slime changes, it effects the efficiency of gas transport through the skin.

2) External Protection: Body slime prevents attachment of ectoparasites by making the surface of the fish slippery, sloughing off with the parasite and suffocating pathogens. It also acts as a bandage by covering over a wound caused by trauma or infection. Usually fishes with poorly developed scales are more slimy, for example, Characins (some known as Tetras) and their relatives.

3) Reduces Turbulence: Especially in fast-moving fishes the drag resulting from small spaces between scales and projecting body parts accounts for considerable energy loss (up to 30% by some estimates) in locomotion. The slime acts to smooth out these gaps.