Does a bivalve have a nervous system?
Translation: Bivalves have a very simple nervous system which is not aggregated in anything like a brain. My conclusion: Bivalves do not have hardware or response consistent with the ability to feel pain. Because they have no brain, or central processing unit for stimuli, there is no ‘there’, there.
How does a bivalve obtain its food?
How do members of class bivalve obtain their food? filter-feed. what is the significance of members of the genus hapalochlaena to human health?
Are shellfish and bivalves the same thing?
There are two groups of shellfish: crustaceans (such as shrimp, prawns, crab and lobster) and mollusks/bivalves (such as clams, mussels, oysters, scallops, octopus, squid, abalone, snail). Allergy to crustaceans is more common than allergy to mollusks, with shrimp being the most common shellfish allergen for both children and adults.
Which is a bivalve a crab or an oyster?
bivalve shellfish such as clams, oysters, scallops, and mussels, other molluscan shellfish such as whelks and, the tomalley of lobster and crab. Is squid a bivalve? includes clams, snails, slugs, nudibranchs, squid, octopuses, tusk shells, chitons, and many others that are all generally called mollusksMollusk: …
What makes a bivalve a bivalve?
Clams, mussels, oysters, and scallops are members to the class Bivalvia (or Pelecypodia). Bivalves have two shells, connected by a flexible ligament, which encase and shield the soft vulnerable parts of the creature.
What are the three characteristics of bivalves?
Three of the main characteristics of bivalves are:Two equally sized shells that close together for protection using muscles.A large, muscular foot that is used to bury within the lake or ocean bottom. ... A straw-like siphon which protrudes out of the shell to take in and get rid of water and food.
What is the main characteristic of a bivalve?
A bivalve is characterized by possessing two shells secreted by a mantle that extends in a sheet on either side of the body. The oldest part of the shell, the umbo, can be recognized as a large hump on the anterior end of the dorsal side of each shell.
How do you identify a bivalve?
The bivalve shell is composed of two valves ("bi-valves"). The valves are joined by a hinge composed of tiny "teeth" and usually also an elastic ligament. The number, size and shape of the teeth as well as the position of the ligament are important characters for the identification of bivalves.
What makes an oyster a bivalve?
Bivalve mollusks (e.g., clams, oysters, mussels, scallops) have an external covering that is a two-part hinged shell that contains a soft-bodied invertebrate. A roughfile clam from the Flower Garden Bank National Marine Sanctuary—just one of many different bivalve mollusk species.
How are bivalves different from other mollusks?
As a group, bivalves have no head and they lack some usual molluscan organs like the radula and the odontophore. They include the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders.
Why are clams called bivalves?
Clams and their relatives (oysters, scallops, and mussels) are often called bivalves (or bivalved mollusks) because their shell is composed of two parts called valves. Bivalves have a long history.
What are bivalve shells made of?
The bivalve shell is made of calcium carbonate embedded in an organic matrix secreted by the mantle.
Do all bivalves have shells?
Not all bivalves still have a shell though; some have evolved a reduced shell or have completely lost the shell. Throughout history, bivalves have been one of the most important marine animals to humans.
Is sea Urchin a bivalve?
Waldo is a genus of small marine clams in the family Galeommatidae. It includes five species which are all obligate commensals of sea urchins....Waldo (bivalve)WaldoKingdom:AnimaliaPhylum:MolluscaClass:BivalviaOrder:Galeommatida12 more rows
Are all mollusks bivalves?
True oystersMusselsScallopsVenus clamsCockleLajonkairia lajonkairiiBivalvia/Lower classifications
What specialized parts do bivalves have?
The most prominent feature of bivalves is the two valves of the shell that may or may not be equal and may or may not completely enclose the inner soft parts. They have a variety of shapes and colours depending on species.
What is the defining characteristic of organisms in class Bivalvia?
bivalve, (class Bivalvia), any of more than 15,000 species of clams, oysters, mussels, scallops, and other members of the phylum Mollusca characterized by a shell that is divided from front to back into left and right valves.
What are some examples of bivalves?
True oystersMusselsScallopsVenus clamsCockleLajonkairia lajonkairiiBivalvia/Lower classifications
Do bivalves feel pain?
In addition, as we will discuss, bivalves have the ability to close their shells to avoid sources of harm, and feeling pain (which requires sentience) could allow them to do so in appropriate circumstances.
What are the characteristics of gastropods?
Gastropods typically have a large foot with a flat sole for crawling, a single coiled shell that covers the soft body, and a head that bears a pair of eyes and tentacles. However, they are so diverse that some forms lack shells, while animals in one genus have shells with two halves, like bivalves.
What is a bivalve mollusk?
Bivalve mollusks (e.g., clams, oysters, mussels, scallops) have an external covering that is a two-part hinged shell that contains a soft-bodied invertebrate.
How do bivalves gather food?
As filter feeders, bivalves gather food through their gills. Some bivalves have a pointed, retractable "foot" that protrudes from the shell and digs into the surrounding sediment, effectively enabling the creature to move or burrow. Bivalves even make their own shells.
What is a bivalve?
Bivalve, (class Bivalvia), any of more than 15,000 species of clams, oysters, mussels, scallops, and other members of the phylum Mollusca characterized by a shell that is divided from front to back into left and right valves.
How big are bivalves?
Bivalves range in size from about one millimetre (0.04 inch) in length to the giant clam of South Pacific coral reefs, Tridacna gigas, which may be more than 137 centimetres (54 inches) in length and weigh 264 kilograms (582 pounds). Such an animal may have a life span of about 40 years.
What is a byssus?
The byssus is a larval feature that is retained by adults of some bivalve groups , such as the true mussels (family Mytilidae) of marine and estuarine shores and the family Dreissenidae of fresh and estuarine waters. Such a shell form and habit evolved first within sediments (endobyssate), where the byssus serves for anchorage ...
Where do bivalves live?
In shallow seas, bivalves are often dominant on rocky and sandy coasts and are also important in offshore sediments. They occur at abyssal and hadal depths, either burrowing or surface-dwelling, and are important elements of the midoceanic rift fauna.
Do bivalves have circular shells?
From the simple burrowing, equivalve ancestor, the various bivalve groups have repeatedly evolved an elongated, triangular or circular shell; thus, similar body adaptations have been responses to similar modes of life.
Is a bivalves a terrestrial or terrestrial species?
There are no terrestrial bivalves, although some high-intertidal and freshwater species can withstand drought conditions.
Do bivalves eat sediment?
Primitive bivalves ingest sediment; however, in most species the respiratory gills have become modified into organs of filtration called ctenidia. In keeping with a largely sedentary and deposit-feeding or suspension-feeding lifestyle, bivalves have lost the head and the radular rasping organ typical of most mollusks.
What are bivalves used for?
The shells of bivalves are used in craftwork , and the manufacture of jewellery and buttons. Bivalves have also been used in the biocontrol of pollution. Bivalves appear in the fossil record first in the early Cambrian more than 500 million years ago. The total number of known living species is about 9,200.
How big is a bivalves shell?
Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length, but the majority of species do not exceed 10 cm (4 in).
What is the etymology of bivalvia?
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. More recently, the class was known as Pelecypoda, meaning " axe -foot" (based on the shape of the foot of the animal when extended).
What is the name of the clam that has an empty shell?
Empty shell of the giant clam. ( Tridacna gigas) Empty shells of the sword razor. ( Ensis ensis) Bivalvia ( / baɪˈvælviə / ), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts.
How many species are there in marine bivalves?
Marine bivalves (including brackish water and estuarine species) represent about 8,000 species, combined in four subclasses and 99 families with 1,100 genera. The largest recent marine families are the Veneridae, with more than 680 species and the Tellinidae and Lucinidae, each with over 500 species. The freshwater bivalves include seven families, ...
Where are the sensory organs of bivalves located?
The sensory organs of bivalves are not well developed and are largely located on the posterior mantle margins. The organs are usually mechanoreceptors or chemoreceptors, in some cases located on short tentacles. The chemoreceptor cells taste the water and are sensitive to touch. They are typically found near the siphons, but in some species, they fringe the entire mantle cavity. The osphradium is a patch of sensory cells located below the posterior adductor muscle that may serve to taste the water or measure its turbidity, but is probably not homologous with the structure of the same name found in snails and slugs. Statocysts within the organism help the bivalve to sense and correct its orientation. Each statocyst consists of a small sac lined with sensory cilia that detect the movement of a mineral mass, a statolith, under gravity. In the order Anomalodesmata, the inhalant siphon is surrounded by vibration-sensitive tentacles for detecting prey.
What is the most common source of pearls?
A better understanding of the potential hazards of eating raw or undercooked shellfish has led to improved storage and processing. Pearl oysters (the common name of two very different families in salt water and fresh water) are the most common source of natural pearls.
Where do bivalves live?
Bivalves are found in most parts of the ocean from the intertidal zone to abyssal depths. Internal structure of a clam.
What is the internal structure of a clam?
Internal structure of a clam. A ligament hinges the shell's two halves (valves) open, and the beating motion of cilia on the gills causes water to enter through the incurrent siphon. As water moves over the gills, oxygen diffuses into the blood, and food particles become trapped in mucus and are moved to the mouth.
What muscles are used to hold a clam's shell?
A pair of adductor muscles can hold the shell tightly closed. A fold of tissue (mantle) encloses the body's organs and releases the material that forms the shell. A large muscular foot allows the clam to creep and burrow.
How are fossil bivalves formed?
Fossil bivalves were formed when the sediments in which they were buried hardened into rock. Many closely resemble living forms, which helps us to understand how they must have lived. The animal. The geologists’ tool. Myths and legends. 3D fossil models.
How do bivalves live?
Most bivalves live by filtering waterborne food particles, although some extract nutrients directly from the sediment. In the Mesozoic Era, the evolution of extendable tubes of soft tissue (siphons) enabled bivalves to burrow more deeply whilst keeping their food supply accessible.
How long have bivalves been around?
Bivalves. Bivalves have inhabited the Earth for over 500 million years. They first appeared in the midddle Cambrian, about 300 million years before the dinosaurs. They flourished in the Mesozoic and Cenozoic eras and they abound in modern seas and oceans; their shells litter beaches across the globe. Some also occur in lakes and rivers.
What is a bivalves tool?
The geologists’ tool. Bivalves can be used to show if the rocks in which they occur were formed in a marine, brackish or freshwater environment. For example, abundant fossil oysters might suggest deposition in shallow water or proximity to ancient shorelines.
What are the enemies of bivalves?
Bivalve environments and enemies. Bivalves are vulnerable to attack from gastropods, crustaceans, starfish, fish and birds. Large, thick shells and spines protect some, while others hide themselves by burrowing into the sea bed using an extendable muscular ‘foot’.
What are the functions of bivalve shells?
The most important functions of fossil bivalve shells were to protect against predators and prevent dehydration in intertidal environments . The inside surface of a bivalve shell is marked by the attachment areas of the muscles and ligament responsible for opening and closing the valves.
What is the name of the shells that are found in a bivalves?
Bivalves, which belong to the phylum Mollusca and the class Bivalvia, have two hard, usually bowl-shaped, shells (called valves) enclosing the soft body. The valves are the parts usually found as fossils, but decay of the elastic hinge tissue that joins them means that they are rarely preserved together.
Overview
Anatomy
Bivalves have bilaterally symmetrical and laterally flattened bodies, with a blade-shaped foot, vestigial head and no radula. At the dorsal or back region of the shell is the hinge point or line, which contain the umbo and beak and the lower, curved margin is the ventral or back region. The anterior or front of the shell is where the byssus (when present) and foot are located, and the posterior of the shell is where the siphons are located. With the hinge uppermost and with the a…
Etymology
The taxonomic term Bivalvia was first used by Linnaeus in the 10th edition of his Systema Naturae in 1758 to refer to animals having shells composed of two valves. More recently, the class was known as Pelecypoda, meaning "axe-foot" (based on the shape of the foot of the animal when extended).
The name "bivalve" is derived from the Latin bis, meaning "two", and valvae, meaning "leaves of a …
Comparison with brachiopods
Brachiopods are shelled marine organisms that superficially resembled bivalves in that they are of similar size and have a hinged shell in two parts. However, brachiopods evolved from a very different ancestral line, and the resemblance to bivalves only arose because they occupy similar ecological niches. The differences between the two groups are due to their separate ancestral origins. Different initial structures have been adapted to solve the same problems, a case of con…
Evolutionary history
The Cambrian explosion took place around 540 to 520 million years ago (Mya). In this geologically brief period, all the major animal phyla diverged and these included the first creatures with mineralized skeletons. Brachiopods and bivalves made their appearance at this time, and left their fossilized remains behind in the rocks.
Possible early bivalves include Pojetaia and Fordilla; these probably lie in the stem rather than cro…
Diversity of extant bivalves
The adult maximum size of living species of bivalve ranges from 0.52 mm (0.02 in) in Condylonucula maya, a nut clam, to a length of 1,532 millimetres (60.3 in) in Kuphus polythalamia, an elongated, burrowing shipworm. However, the species generally regarded as the largest living bivalve is the giant clam Tridacna gigas, which can grow to a length of 1,200 mm (47 in) and a weight of more than 200 kg (441 lb). The largest known extinct bivalve is a species of Platyceram…
Distribution
The bivalves are a highly successful class of invertebrates found in aquatic habitats throughout the world. Most are infaunal and live buried in sediment on the seabed, or in the sediment in freshwater habitats. A large number of bivalve species are found in the intertidal and sublittoral zones of the oceans. A sandy sea beach may superficially appear to be devoid of life, but often a very large number of bivalves and other invertebrates are living beneath the surface of the sand. …
Behaviour
Most bivalves adopt a sedentary or even sessile lifestyle, often spending their whole lives in the area in which they first settled as juveniles. The majority of bivalves are infaunal, living under the seabed, buried in soft substrates such as sand, silt, mud, gravel, or coral fragments. Many of these live in the intertidal zone where the sediment remains damp even when the tide is out. When buried in the sediment, burrowing bivalves are protected from the pounding of waves, desiccatio…