Greater weever facts for kids
Quick facts for kids Greater weever |
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Trachinus lineatus Bloch & Schneider, 1801 |
The greater weever (Trachinus draco) is a venomous fish that lives on the seafloor. It belongs to the Trachinidae family. You can find the greater weever along the eastern Atlantic coast, from Norway all the way to Morocco. It also lives in the Mediterranean, Aegean, and Black Seas.
This fish usually lives in muddy or sandy areas, from shallow waters down to about 150 meters deep. The greater weever is famous for its venomous spines, which can cause painful stings to humans. Because of these spines and its strong venom, it's known as one of the most venomous fish in the Mediterranean. The name "weever" might come from an old Anglo-Saxon word, "wivre," which means "viper."
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Physical Appearance
The greater weever has a long, flat body. Its eyes stick up, and its mouth points upwards, with the lower jaw longer than the upper one. Its head is flat and quite large, with the eyes almost on top. It has small spines above each eye. The first fin on its back has five to seven spiny rays, and there are thorns on each of its gill covers. These spines and thorns have venom glands at their base.
Colouration
On its back, the greater weever is greenish-brown with dark spots on its head. Its sides are yellowish-brown with bright blue and yellow stripes that run in a zig-zag pattern towards its front. It also has black stripes on its sides, which some people describe as looking like a tiger's stripes.
Body Dimensions
The size of greater weevers can be different depending on where they live. In some areas, females can grow up to 25.8 cm long, and males up to 22.5 cm. Their weight can vary too, from about 5 grams to over 130 grams. However, in other places like the coast of Southern Portugal, much larger females have been found, reaching almost 40 cm in length! Many things can affect how big a greater weever grows, such as water temperature, how salty the water is, the amount and quality of food, and the time of year.
Ecology and Behaviour
Diet and Feeding Behaviour
The greater weever is an "ambush predator." This means it hides and waits for its prey. During the day, it digs itself into the sand, leaving only its eyes and the tip of its back fin showing. When a tasty meal swims by, it quickly attacks!
At night, the greater weever is thought to swim around more freely, even in open water. This idea is supported by the fact that fish caught during the day often have mostly digested food in their stomachs, suggesting they ate earlier, likely at night.
Greater weevers are carnivores, meaning they eat meat. They mainly feed on crabs, small fish, and shrimp. They also eat smaller amounts of other sea creatures like sea lice, tiny shrimp-like animals, and clams. Crabs, fish, and shrimp make up most of their diet.
What they eat can change as they grow. Smaller weevers mostly eat tiny shrimp, but as they get bigger, they start eating more fish and squid. Their diet doesn't change much throughout the year, with crabs being a favorite in summer and autumn, and fish more common in winter.
Sometimes, greater weevers have empty stomachs, especially in winter. This might be because the water is colder, which slows down their body processes and makes them less active in feeding.
Reproduction and Life Cycle
Greater weevers usually reproduce from June to October, with the most active period in July. They are "oviparous," which means they lay eggs. Their eggs are released into the open water, where they float around.
The tiny baby weevers, called larvae, hatch after about three months. Both the eggs and larvae can be found floating near the surface of the water. These young weevers might need warm water with less salt to hatch successfully. Greater weevers don't seem to protect their eggs or young, and they probably don't have their own territories, even during mating season.
Toxicity
Venomous Spines
The greater weever has venomous spines on its gill covers and on its back fin. There's one spine on each gill cover, pointing towards its tail. These spines are covered by a thin skin. If something pushes against the spine, this skin breaks, and venom flows out from glands along a groove in the spine, into the wound.
The spines on its back fin are also covered by individual skin sheaths. These spines vary in length and are arranged in a curve. The way they deliver venom is similar to the gill cover spines.
Venom Glands
The glands that make the venom are located in the fish's skin. These glands are made of special cells that produce the venom. These cells are packed together and contain many small sacs. Other cells help hold the venom glands together and help them regrow if they are damaged.
Venom
The main part of the greater weever's venom that can cause harm is a protein called Dracotoxin. This venom can affect cell membranes and cause red blood cells to break down.
When someone is stung by a weever, the area around the sting often first looks pale, then turns red. This might be because the venom contains substances like histamines, which affect blood flow.
The venom itself is clear and has a grayish color. It's said to have a "fishy taste" and a smell like ammonia. The venom is slightly acidic.
The strength of the venom depends on how it's collected and stored. Venom from live fish that are quickly frozen is the most potent. A single average-sized fish can produce a significant amount of venom.
Relationship with Humans
The most common way people get stung by a greater weever is by accidentally stepping on it. This often happens in summer when people are swimming or walking in shallow, sandy waters where the fish likes to bury itself. Fishermen are also at risk when they handle the fish caught in their nets.
A weever sting is known for causing extreme pain very quickly after the sting. This pain can last for a few hours or even several days. In rare cases, people have reported feeling effects for months. The pain can be so severe that in one old story from 1782, a fisherman reportedly cut off his own finger to stop the pain.
While there have been reports of deaths from weever stings, it's generally believed that these are due to other problems like serious infections rather than the venom itself.
Treatment
There are many old remedies for a weever sting, from putting hot water or vinegar on it to more unusual ideas like fish liver or tobacco juice.
Modern medicine recommends applying heat to the affected area. The best way is to soak the stung limb in hot water (around 40-42°C). This helps to ease the pain. After this first aid, it's important to clean the wound and see a doctor. A doctor might suggest antibiotics to prevent infection, more pain medicine, or a tetanus shot.
Commercial Use
Even though the greater weever is sometimes caught by accident with other fish, it is sold in France and considered a special food. In some parts of the Mediterranean, if it's caught with other mixed fish, it might be sold in a category called "morralla."
Images for kids
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Greater weever
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Greater weever
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A greater weever, half-buried in the sand in shallow water.
