Bivalves
Everything about Bivalves!
This week all about bivalves. Yes, it is a day later than usual but there have been a number of technical errors that have slowed things down. So with this blog and it is extra interesting if I want to see a recent one like the fossil bivalves (bivalves).
This week all about bivalves. Yes, it is a day later than usual but there have been a number of technical errors that have slowed things down. So with this blog and it is extra interesting if I want to see a recent one like the fossil bivalves (bivalves).
Anatomy of bivalves
Bivalves specifically strong in shape and habits. For example, you have species that burrow themselves into the soil. Species that are semi-buried, species that are stuck to the bottom and species that can even swim freely. The mantle is the thin membrane that covers the animal. Bivalves have less complex nerves than other mollusks and they lack brains. Sensory organs are not well developed and are located behind the mantle. For example, the tatocysts, which help to detect and correct orientation. Many bivalves do not have eyes but species from the family of the; acroidea, limopsoidea, mytiloidea, anomoidea, ostreoidea and limoidea have simple eyes on the edge of the mantle. Bivalves have a circulatory system and a three-chambered heart. Oxygen word recorded from the gills. The gills hang in the mantle cavity. Although all bivalves have gills, some species can survive for an hour without water. These are mainly tidal zone species. Most species are filter feeders that trap food particles such as phytoplankton from the water. There are also species that scrape the soil in search of food. The shell also has a number of characteristics that are very important to collectors. After all, the shell is the part that is collected. You will see some of these characteristics in the images below.
Bivalves specifically strong in shape and habits. For example, you have species that burrow themselves into the soil. Species that are semi-buried, species that are stuck to the bottom and species that can even swim freely. The mantle is the thin membrane that covers the animal. Bivalves have less complex nerves than other mollusks and they lack brains. Sensory organs are not well developed and are located behind the mantle. For example, the tatocysts, which help to detect and correct orientation. Many bivalves do not have eyes but species from the family of the; acroidea, limopsoidea, mytiloidea, anomoidea, ostreoidea and limoidea have simple eyes on the edge of the mantle. Bivalves have a circulatory system and a three-chambered heart. Oxygen word recorded from the gills. The gills hang in the mantle cavity. Although all bivalves have gills, some species can survive for an hour without water. These are mainly tidal zone species. Most species are filter feeders that trap food particles such as phytoplankton from the water. There are also species that scrape the soil in search of food. The shell also has a number of characteristics that are very important to collectors. After all, the shell is the part that is collected. You will see some of these characteristics in the images below.
Evolution
The first bivalves appear at the beginning of the Cambrian about 500 million years ago. However, the numbers only exploded after the Perm Triassic extinction. This is because their competitors dealt a huge blow to the brachiopods here and many brachiopods also disappeared back then. Which gave room for the bivalves to develop further into the diverse group they still are today. There are therefore very many modern species, about 9,200 in contrast to the brachiopods, of which only about 200 species are still alive.
The first bivalves appear at the beginning of the Cambrian about 500 million years ago. However, the numbers only exploded after the Perm Triassic extinction. This is because their competitors dealt a huge blow to the brachiopods here and many brachiopods also disappeared back then. Which gave room for the bivalves to develop further into the diverse group they still are today. There are therefore very many modern species, about 9,200 in contrast to the brachiopods, of which only about 200 species are still alive.
Recognize fossil bivalves
In our country there are plenty of opportunities to collect fossils of bivalves, but how do you recognize them? Holocene so relatively young fossil shells often have a bluish color while older shells are often pale white or gray. They are also often thicker and do not allow light to pass through when you hold a light from, for example, your mobile phone underneath.
In our country there are plenty of opportunities to collect fossils of bivalves, but how do you recognize them? Holocene so relatively young fossil shells often have a bluish color while older shells are often pale white or gray. They are also often thicker and do not allow light to pass through when you hold a light from, for example, your mobile phone underneath.
Collecting fossil bivalves
Now that you know how to recognize fossils, you just need to know where they are found. This can be done, for example, along the entire Dutch coast with hotspots; Het Zwin, De Zwarte polder, Cadzand, the 2nd Maasvlakte, the Sand Motor and the Wadden Islands. Fossil shells can also be found in the chalk of Limburg, in the Miocene of Miste and in the Triassic of Winterswijk. However, some of these locations are closed to collectors.
Now that you know how to recognize fossils, you just need to know where they are found. This can be done, for example, along the entire Dutch coast with hotspots; Het Zwin, De Zwarte polder, Cadzand, the 2nd Maasvlakte, the Sand Motor and the Wadden Islands. Fossil shells can also be found in the chalk of Limburg, in the Miocene of Miste and in the Triassic of Winterswijk. However, some of these locations are closed to collectors.
Micro bivalves
In addition to the largest species, the baptismal scallop (Tridinca gigas) that can reach 120cm, there are also very small species. As soon as they are smaller than an inch we call them micro shells. A good binocular is often required to view these shells. Storing, collecting and identifying is also a difficult job. When collecting you do not pick up individual copies as one would normally do, they are simply too small for this. That is why we just scoop some of the top layer of sand in a bag on a beach, after which we investigate this further at home. If the shells are still around the centimeter, then micromount boxes are in principle sufficient, but test tubes are often used for even smaller ones.
In addition to the largest species, the baptismal scallop (Tridinca gigas) that can reach 120cm, there are also very small species. As soon as they are smaller than an inch we call them micro shells. A good binocular is often required to view these shells. Storing, collecting and identifying is also a difficult job. When collecting you do not pick up individual copies as one would normally do, they are simply too small for this. That is why we just scoop some of the top layer of sand in a bag on a beach, after which we investigate this further at home. If the shells are still around the centimeter, then micromount boxes are in principle sufficient, but test tubes are often used for even smaller ones.
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