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Description
European snakefish (Serpentozoarces europaea)
Order: Percoid fishes (Perciformes)
Family: Eelpouts (Zoarcidae)
Habitat: rivers and swamps of Central, East and North Europe, temperate and cold climatic zones.
Seas of North Europe underwent significant changes at the boundary of Holocene and Neocene. The congelation had held down the north of Eurasia by continuous ice cover, having buried under it Baltic Sea and coast of Northern Sea (in ice age the ocean level had decreased, and the sea had substantionally receded). Inhabitants of sea coasts had been compelled to adapt to changing conditions, or died out. The part of species had receded following the sea, and the another part had passed to life in fresh water of rivers and lakes. Among survived species there were various crustaceans and some fishes. When climate had changed again, these species had occupied new habitats already in new quality.
One of such fugitives from a glacier lives in fresh waters of Europe – it is European snakefish, the freshwater species of eelpouts. Ancestors of this fish had completely left the sea in glacial epoch at the boundary of Holocene and Neocene – they appeared are off from northern seas by coming glaciers, and compelled to adapt to inhabiting in fresh water. The majority of sea fishes can not make it because of problems in development of eggs and fry. But eelpouts had easily made it – they belong to viviparous fishes, and in their life cycle there is no the stage of egg sensitive to change of external factors. Therefore right till some millenia populations of eelpouts completely passed full cycle of development in fresh water had appeared in Europe.
The snakefish has kept features of appearance characteristic for its ancestors. It is a fish more than one and half meters long with reduced unpaired fins which edge its back and tail as a continuous narrow border. In forward part of back fin there are some spikes with poisonous slime serving for protection against enemies. Pectoral fins have fleshy bases, and fin rays are strong and elastic. With their help snakefish pushes from roughnesses of ground during the movement on land and makes the way through thickets of underwater plants.
The skin of European snakefish is naked, but covered with a layer of viscous slime. It prevents the drying when fish appears on land. Besides the skin of snakefish is penetrated with a circuit of capillaries, and through it fish receives a significant part of oxygen. Colouring of skin is spotty, green with black “marble” pattern; stomach is white.
Head of snakefish is flat and wide, with slightly bulging eyes and wide mouth. Teeth are pointed and thin.
Snakefish settles in marshlands where small reservoirs alternate with sites of land. The majority of fishes does not live in such places, therefore snakefish is almost out of competition. In summer reservoirs, in which it settles, may dry up. But snakefish is well adapted to such difficulties. It can easily creep overland, respiring with the help of skin. This fish creeps pushing by bends of body and helping itself by pectoral fins. Snakefish can creep within several days in searches of water. If weather is too hot, fish hides in shady place and may escape from heat even in holes of rodents.
Snakefish is a predator. In water it eats small fish, frogs and crustaceans. Frequently snakefish traps them in shallow water, having dug in ground, or having hidden among plants. Also this fish can catch sluggish insects, snails and earthworms on land.
This species of fishes has kept ability to vivipary had helped to survive to its ancestors till the ice age. Pairing at snakefishes takes place in autumn, and female hibernates, while in its ovaries the posterity develops. Young ones of snakefish receive an additional feed – products of secretion of female’s ovoducts walls. Due to it the posterity of snakefish is born already completely developed and ready to independent life. In spring when the high water comes to an end, the female gives rise to about ten large young fishes, reaching approximately one fifth of the length of female.

Description
European snakefish (Serpentozoarces europaea)
Order: Percoid fishes (Perciformes)
Family: Eelpouts (Zoarcidae)
Habitat: rivers and swamps of Central, East and North Europe, temperate and cold climatic zones.
Seas of North Europe underwent significant changes at the boundary of Holocene and Neocene. The congelation had held down the north of Eurasia by continuous ice cover, having buried under it Baltic Sea and coast of Northern Sea (in ice age the ocean level had decreased, and the sea had substantionally receded). Inhabitants of sea coasts had been compelled to adapt to changing conditions, or died out. The part of species had receded following the sea, and the another part had passed to life in fresh water of rivers and lakes. Among survived species there were various crustaceans and some fishes. When climate had changed again, these species had occupied new habitats already in new quality.
One of such fugitives from a glacier lives in fresh waters of Europe – it is European snakefish, the freshwater species of eelpouts. Ancestors of this fish had completely left the sea in glacial epoch at the boundary of Holocene and Neocene – they appeared are off from northern seas by coming glaciers, and compelled to adapt to inhabiting in fresh water. The majority of sea fishes can not make it because of problems in development of eggs and fry. But eelpouts had easily made it – they belong to viviparous fishes, and in their life cycle there is no the stage of egg sensitive to change of external factors. Therefore right till some millenia populations of eelpouts completely passed full cycle of development in fresh water had appeared in Europe.
The snakefish has kept features of appearance characteristic for its ancestors. It is a fish more than one and half meters long with reduced unpaired fins which edge its back and tail as a continuous narrow border. In forward part of back fin there are some spikes with poisonous slime serving for protection against enemies. Pectoral fins have fleshy bases, and fin rays are strong and elastic. With their help snakefish pushes from roughnesses of ground during the movement on land and makes the way through thickets of underwater plants.
The skin of European snakefish is naked, but covered with a layer of viscous slime. It prevents the drying when fish appears on land. Besides the skin of snakefish is penetrated with a circuit of capillaries, and through it fish receives a significant part of oxygen. Colouring of skin is spotty, green with black “marble” pattern; stomach is white.
Head of snakefish is flat and wide, with slightly bulging eyes and wide mouth. Teeth are pointed and thin.
Snakefish settles in marshlands where small reservoirs alternate with sites of land. The majority of fishes does not live in such places, therefore snakefish is almost out of competition. In summer reservoirs, in which it settles, may dry up. But snakefish is well adapted to such difficulties. It can easily creep overland, respiring with the help of skin. This fish creeps pushing by bends of body and helping itself by pectoral fins. Snakefish can creep within several days in searches of water. If weather is too hot, fish hides in shady place and may escape from heat even in holes of rodents.
Snakefish is a predator. In water it eats small fish, frogs and crustaceans. Frequently snakefish traps them in shallow water, having dug in ground, or having hidden among plants. Also this fish can catch sluggish insects, snails and earthworms on land.
This species of fishes has kept ability to vivipary had helped to survive to its ancestors till the ice age. Pairing at snakefishes takes place in autumn, and female hibernates, while in its ovaries the posterity develops. Young ones of snakefish receive an additional feed – products of secretion of female’s ovoducts walls. Due to it the posterity of snakefish is born already completely developed and ready to independent life. In spring when the high water comes to an end, the female gives rise to about ten large young fishes, reaching approximately one fifth of the length of female.