102-514: Southerndown is a village in the Vale of Glamorgan , in south Wales . It is southwest of Bridgend , and within the St Brides Major community , close to Llantwit Major and Ogmore-by-Sea . It is mostly known for its beach which backs Dunraven Bay ( Welsh : Bae Dwnrhefn ), which is a popular tourist destination during the summer months and since 1972 has been part of a Heritage Coast and
204-420: A different way, scraping detritus from the seabed, and this may be the original mode of feeding used by all bivalves before the gills became adapted for filter feeding. These primitive bivalves hold on to the bottom with a pair of tentacles at the edge of the mouth, each of which has a single palp , or flap. The tentacles are covered in mucus , which traps the food, and cilia, which transport the particles back to
306-528: A feature shared with two other major groups of marine invertebrates, the bryozoans and the phoronids . Some brachiopod shells are made of calcium phosphate but most are calcium carbonate in the form of the biomineral calcite , whereas bivalve shells are always composed entirely of calcium carbonate, often in the form of the biomineral aragonite . The Cambrian explosion took place around 540 to 520 million years ago (Mya). In this geologically brief period, most major animal phyla diverged including some of
408-403: A flexible ligament that, usually in conjunction with interlocking "teeth" on each of the valves, forms the hinge . This arrangement allows the shell to be opened and closed without the two halves detaching. The shell is typically bilaterally symmetrical , with the hinge lying in the sagittal plane . Adult shell sizes of bivalves vary from fractions of a millimetre to over a metre in length, but
510-408: A group, bivalves have no head and lack some typical molluscan organs such as the radula and the odontophore . Their gills have evolved into ctenidia , specialised organs for feeding and breathing. Common bivalves include clams , oysters , cockles , mussels , scallops , and numerous other families that live in saltwater, as well as a number of families that live in freshwater. Majority of
612-460: 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 convergent evolution . In modern times, brachiopods are not as common as bivalves. Both groups have
714-499: A pair of nephridia . Each of these consists of a long, looped, glandular tube, which opens into the pericardium , and a bladder to store urine. They also have pericardial glands either line the auricles of the heart or attach to the pericardium, and serve as extra filtration organs. Metabolic waste is voided from the bladders through a nephridiopore near the front of the upper part of the mantle cavity and excreted. The sexes are usually separate in bivalves but some hermaphroditism
816-484: A relatively small dispersal potential before settling out. The common mussel ( Mytilus edulis ) produces 10 times as many eggs that hatch into larvae and soon need to feed to survive and grow. They can disperse more widely as they remain planktonic for a much longer time. Freshwater bivalves have different lifecycle. Sperm is drawn into a female's gills with the inhalant water and internal fertilization takes place. The eggs hatch into glochidia larvae that develop within
918-644: A resting state, even when they are permanently submerged. In oysters, for example, their behaviour follows very strict circatidal and circadian rhythms according to the relative positions of the moon and sun. During neap tides, they exhibit much longer closing periods than during spring tides. Although many non-sessile bivalves use their muscular foot to move around, or to dig, members of the freshwater family Sphaeriidae are exceptional in that these small clams climb about quite nimbly on weeds using their long and flexible foot. The European fingernail clam ( Sphaerium corneum ), for example, climbs around on water weeds at
1020-736: A roofing material for houses in the Vale. As the Glamorgan Heritage Coast faces westwards out to the Atlantic, it bears the brunt of onshore (westerly and south-westerly) winds: ideal for surfing, but a nuisance for ships sailing up the Bristol Channel to Cardiff . As in North Cornwall and South-West Ireland, the fierce Atlantic gales created ideal conditions for deliberate shipwrecking , which until 100 years ago
1122-424: A shadow falling over the animal. Bivalves have an open circulatory system that bathes the organs in blood ( hemolymph ). The heart has three chambers: two auricles receiving blood from the gills, and a single ventricle . The ventricle is muscular and pumps hemolymph into the aorta , and then to the rest of the body. Some bivalves have a single aorta, but most also have a second, usually smaller, aorta serving
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#17327870364521224-436: A shell consisting of two valves, but the organization of the shell is quite different in the two groups. In brachiopods, the two valves are positioned on the dorsal and ventral surfaces of the body, while in bivalves, the valves are on the left and right sides of the body, and are, in most cases, mirror images of one other. Brachiopods have a lophophore , a coiled, rigid cartilaginous internal apparatus adapted for filter feeding,
1326-424: A steady pull. Paired pedal protractor and retractor muscles operate the animal's foot. The sedentary habits of the bivalves have meant that in general the nervous system is less complex than in most other molluscs. The animals have no brain ; the nervous system consists of a nerve network and a series of paired ganglia . In all but the most primitive bivalves, two cerebropleural ganglia are on either side of
1428-528: A warm, shallow sea during the early part of the Carboniferous Period when the future Wales lay on or near the equator. Continental drift and earthquakes folded and fractured the Earth's crust, and during the next 100 million years the rocks suffered extensive erosion. The movements left the upfolded Carboniferous Limestone as high ground, the slopes and cliffs of the Vale of Glamorgan . During
1530-508: Is Barry . Other towns include Penarth , Llantwit Major , and Cowbridge . There are many villages in the county borough. The area is the southernmost part of the county of Glamorgan . Between the 11th century and 1536 the area was part of the Lordship of Glamorgan. In medieval times, the village of Cosmeston , near what is today Penarth in the south east of the county, grew up around a fortified manor house constructed sometime around
1632-753: Is a county borough in the south-east of Wales . It borders Bridgend County Borough to the west, Cardiff to the east, Rhondda Cynon Taf to the north, and the Bristol Channel to the south. With an economy based largely on agriculture and chemicals, it is the southernmost unitary authority in Wales. Attractions include Barry Island Pleasure Park , the Barry Tourist Railway , Medieval wall paintings in St Cadoc's Church, Llancarfan , Porthkerry Park , St Donat's Castle , Cosmeston Lakes Country Park and Cosmeston Medieval Village . The largest town
1734-520: Is also situated in the Vale of Glamorgan. The Vale of Glamorgan is twinned with: and has friendship agreements with: The following people and military units have received the Freedom of the Borough of the Vale of Glamorgan. As of the 2021 United Kingdom census , the county borough's ethnic groups are as follows: As of the 2021 United Kingdom census , the county borough's religious make-up
1836-472: Is as follows: Bivalvia And see text Bivalvia ( / b aɪ ˈ v æ l v i ə / ) or bivalves , in previous centuries referred to as the Lamellibranchiata and Pelecypoda , is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half- shells known as valves . As
1938-432: Is composed of two calcareous valves held together by a ligament. The valves are made of either calcite , as is the case in oysters, or both calcite and aragonite . Sometimes, the aragonite forms an inner, nacreous layer, as is the case in the order Pteriida . In other taxa , alternate layers of calcite and aragonite are laid down. The ligament and byssus, if calcified, are composed of aragonite. The outermost layer of
2040-613: Is further served by Great Western Railway services to destinations in South West England and CrossCountry services to the Midlands . The Barry Tourist Railway is a short heritage railway and museum on Barry Island. Bus services in the Vale of Glamorgan are principally operated by New Adventure Travel (NAT) and Cardiff Bus . The Vale of Glamorgan Council operates a community ' on-demand ' transport service in rural communities called Greenlinks. Cardiff Airport
2142-481: Is in the Vale of Glamorgan, near Rhoose. In 2019, Cardiff Airport claimed to have a £135 million direct economic benefit to the region. Destinations from Cardiff Airport at the time included Alicante , Amsterdam , Anglesey , Dublin , and Doha . A "Masterplan" for the airport sets out the Welsh Government's ambition to grow the airport's passenger numbers and freight operations by 2040. MOD St Athan
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#17327870364522244-557: Is known. The gonads either open into the nephridia or through a separate pore into a chamber over the gills. The ripe gonads of males and females release sperm and eggs into the water column . Spawning may take place continually or be triggered by environmental factors such as day length, water temperature, or the presence of sperm in the water. Some species are "dribble spawners", releasing gametes during protracted period that can extend for weeks. Others are mass spawners and release their gametes in batches or all at once. Fertilization
2346-561: Is part of the Southerndown Coast SSSI . When the tide is out there is an expanse of sand and pools. The cliffs are an obvious example of sedimentary rock . As Southerndown, along with nearby Ogmore-by-Sea , is a west-facing beach (and hence on the Atlantic coast), off-shore winds usually generate much good-quality surf, helped by the warming effects of the Gulf Stream . A larger rocky shore platform and beach to
2448-408: Is secreted by the mantle edge, and the valves themselves thicken as more material is secreted from the general mantle surface. Calcareous matter comes from both its diet and the surrounding seawater. Concentric rings on the exterior of a valve are commonly used to age bivalves. For some groups, a more precise method for determining the age of a shell is by cutting a cross section through it and examining
2550-472: Is the ventral or underside 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 anterior edge of the animal towards the viewer's left, the valve facing the viewer is the left valve and the opposing valve the right. Many bivalves such as clams, which appear upright, are evolutionarily lying on their side. The shell
2652-432: Is usually external. Typically, a short stage lasts a few hours or days before the eggs hatch into trochophore larvae. These later develop into veliger larvae which settle on the seabed and undergo metamorphosis into adults. In some species, such as those in the genus Lasaea , females draw water containing sperm in through their inhalant siphons and fertilization takes place inside the female. These species then brood
2754-567: The Celtic Sea coastline (i.e. Cornwall , Wales , Ireland and Brittany ) as they are formed of a combination of Liassic limestone , shale and Carboniferous Limestone . The rocks were formed between 360 and 200 million years ago when the whole area lay underneath a warm, shallow sea at the start of the Jurassic period. Thus today the cliffs contain traces of Jurassic sea creatures, such as ammonites. The calcium carbonate ( limestone ) in
2856-612: The Early Silurian , the gills were becoming adapted for filter feeding, and during the Devonian and Carboniferous periods, siphons first appeared, which, with the newly developed muscular foot, allowed the animals to bury themselves deep in the sediment. By the middle of the Paleozoic , around 400 Mya, the brachiopods were among the most abundant filter feeders in the ocean, and over 12,000 fossil species are recognized. By
2958-526: The Glamorganshire , Southerndown and Wenvoe Castle clubs. Owing to its close proximity to Cardiff, most of the major roads in the county borough originate in the capital. Running east–west, the A48 runs through the centre portion of the Vale of Glamorgan between Cardiff and Bridgend , passing along the northern edge of Cowbridge . The M4 motorway also runs east–west along the northern edge of
3060-513: The M4 technology corridor , according to the Welsh Government. The Vale of Glamorgan Line is the county borough's principal rail connection. The line runs between Cardiff Central and Bridgend , with spurs to Barry Island and Penarth . All services on the line are operated by Transport for Wales , linking the Vale directly to other areas of the capital region, including Cardiff Queen Street , Pontypridd , and Merthyr Tydfil . Railway stations in
3162-726: The Permian–Triassic extinction event 250 Mya, bivalves were undergoing a huge radiation of diversity. The bivalves were hard hit by this event, but re-established themselves and thrived during the Triassic period that followed. In contrast, the brachiopods lost 95% of their species diversity . The ability of some bivalves to burrow and thus avoid predators may have been a major factor in their success. Other new adaptations within various families allowed species to occupy previously unused evolutionary niches. These included increasing relative buoyancy in soft sediments by developing spines on
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3264-587: The Veneridae , with more than 680 species and the Tellinidae and Lucinidae , each with over 500 species. The freshwater bivalves include seven families, the largest of which are the Unionidae , with about 700 species. 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,
3366-408: 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. These species are placed within 1,260 genera and 106 families. 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
3468-597: 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. On a large beach in South Wales , careful sampling produced an estimate of 1.44 million cockles ( Cerastoderma edule ) per acre of beach. Bivalves inhabit the tropics, as well as temperate and boreal waters. A number of species can survive and even flourish in extreme conditions. They are abundant in
3570-517: The oesophagus . The cerebral ganglia control the sensory organs, while the pleural ganglia supply nerves to the mantle cavity. The pedal ganglia, which control the foot, are at its base, and the visceral ganglia, which can be quite large in swimming bivalves, are under the posterior adductor muscle. These ganglia are both connected to the cerebropleural ganglia by nerve fibres . Bivalves with long siphons may also have siphonal ganglia to control them. The sensory organs of bivalves are largely located on
3672-400: The " crystalline style " projected into the stomach from an associated sac. Cilia in the sac cause the style to rotate, winding in a stream of food-containing mucus from the mouth, and churning the stomach contents. This constant motion propels food particles into a sorting region at the rear of the stomach, which distributes smaller particles into the digestive glands, and heavier particles into
3774-583: The 12th century by the De Costentin family. The De Costentins, who originated on the Cotentin peninsula in northern France, were among the first Norman invaders of Wales in the early 12th century following William the Conqueror 's invasion of neighbouring England in 1066. The village would have consisted of a number of small stone round houses, or crofts, with thatched roofs. Clemenstone , to
3876-458: The Arctic, about 140 species being known from that zone. The Antarctic scallop, Adamussium colbecki , lives under the sea ice at the other end of the globe, where the subzero temperatures mean that growth rates are very slow. The giant mussel, Bathymodiolus thermophilus , and the giant white clam, Calyptogena magnifica , both live clustered around hydrothermal vents at abyssal depths in
3978-464: The Pacific Ocean. They have chemosymbiotic bacteria in their gills that oxidise hydrogen sulphide , and the molluscs absorb nutrients synthesized by these bacteria. Some species are found in the hadal zone , like Vesicomya sergeevi, which occurs at depths of 7600–9530 meters. The saddle oyster, Enigmonia aenigmatica , is a marine species that could be considered amphibious . It lives above
4080-637: The Vale is Barry Town United F.C. , of the Cymru Premier who play their home games at Jenner Park Stadium in Barry. The club was founded in 1912 and enjoyed success in the 1990s, when they won the League of Wales and the Welsh Cup . The club experienced declining fortunes in the following decade and were relegated to Welsh Football League Division Two , but were promoted to Division One after winning
4182-568: The Vale of Glamorgan Borough was created, with a population of 103,000. The Vale of Glamorgan was a second tier district , part of the new county of South Glamorgan , under the Local Government Act 1972 . It created several problems in local governance, between the South Glamorgan County Council , Cardiff City Council and the Vale of Glamorgan Borough Council owing to their conflicting interests. It
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4284-561: The Vale of Glamorgan are: The South Wales Main Line passes through the Vale, but trains do not stop. The nearest stations on the South Wales Main Line are (from east to west): Cardiff Central; Pontyclun ; Llanharan ; Pencoed ; Bridgend. Most services are operated by Transport for Wales, but Bridgend and Cardiff are additionally served by Great Western Railway services between Swansea and London Paddington . Cardiff Central
4386-513: The Vale, linking the area to major cities such as London, Bristol, Newport , and Swansea . Junctions 33 ( Cardiff West ) and 34 ( Llantrisant ) provide direct access to the Vale of Glamorgan. The M4 is economically important to the county borough as it "facilitates the movements of goods and people" from the region to other areas of the UK, enabling local firms "access to domestic and international markets." The county borough benefits from its location in
4488-472: The air, can gape the shell slightly and gas exchange can take place. Oysters, including the Pacific oyster ( Magallana gigas ), are recognized as having varying metabolic responses to environmental stress, with changes in respiration rate being frequently observed. Most bivalves are filter feeders , using their gills to capture particulate food such as phytoplankton from the water. Protobranchs feed in
4590-469: The alternating blue-grey limestones and shales of the Blue Lias. The Jurassic rocks are generally rich in fossils. Shells of bivalves , and ammonites , fragments of crinoids , corals and pieces of carbonised fossil wood are quite common. During the last 200 million years further earth movements have seen some folding and fracturing of the rocks and, during the relative stasis but higher waters since
4692-588: The class are benthic filter feeders that bury themselves in sediment, where they are relatively safe from predation . Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as scallops and file shells , can swim . Shipworms bore into wood, clay, or stone and live inside these substances. The shell of a bivalve is composed of calcium carbonate , and consists of two, usually similar, parts called valves . These valves are for feeding and for disposal of waste. These are joined together along one edge (the hinge line ) by
4794-572: 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 door'. ("Leaf" is an older word for the main, movable part of a door. We normally consider this the door itself.) Paired shells have evolved independently several times among animals that are not bivalves; other animals with paired valves include certain gastropods (small sea snails in
4896-537: The constituency of Cardiff South and Penarth ) sway between Labour control and Conservative Party control in both the Senedd and Westminster. The UK parliament constituency was created in 1983 and the Welsh Assembly (later Senedd) constituency in 1999. There is substantial Labour support in the east of the constituency and in the town of Barry , and substantial Conservative support in the agricultural area in
4998-741: The county, though none of its clubs compete in the higher leagues. As of the 2015–6 season, Penarth RFC competes in the WRU Division Three South East , Llantwit Major RFC in WRU Division Four South East , and Old Penarthians RFC and Cowbridge RFC in the WRU Division Five South East . Several of the clubs are feeders for Cardiff Blues . There are cricket grounds in Cowbridge and Sully and several golf clubs, including
5100-791: The early Jurassic Period, a shallow sea spread northwards over the land. As the water deepened the higher areas became islands before finally being inundated. Water depth influenced the kinds of sediments that were deposited. Rocks formed close to the shore (Sutton Stone and Southerndown Beds) are strikingly different from the Blue Lias , which was deposited at the same time but farther offshore. Sutton Stone consists of massive, white, conglomeratic limestones with pebbles of black chert (silica) and Carboniferous Limestone. The overlying Southerndown Beds are blue/grey conglomeratic limestones and limy sandstones with thin shale partings. The Sutton Stone and Southerndown Beds pass laterally into, and are overlain by,
5202-436: The edges of lakes and ponds; this enables the clam to find the best position for filter feeding. The thick shell and rounded shape of bivalves make them awkward for potential predators to tackle. Nevertheless, a number of different creatures include them in their diet. Many species of demersal fish feed on them including the common carp ( Cyprinus carpio ), which is being used in the upper Mississippi River to try to control
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#17327870364525304-428: The end of the last Ice Age , the coastline has in most places resumed a fast pace of erosion, retreating in places by several miles by subaerial and marine erosion . 51°27′15″N 3°36′45″W / 51.45417°N 3.61250°W / 51.45417; -3.61250 Vale of Glamorgan The Vale of Glamorgan ( Welsh : Bro Morgannwg [ˈbroː mɔrˈɡanʊɡ] ), locally referred to as The Vale ,
5406-402: The family Juliidae ), members of the phylum Brachiopoda and the minute crustaceans known as ostracods and conchostracans . 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
5508-421: The female's shell. Later they are released and attach themselves parasitically to the gills or fins of a fish host. After several weeks they drop off their host, undergo metamorphosis and develop into adults on the substrate . Some of the species in the freshwater mussel family, Unionidae , commonly known as pocketbook mussels, have evolved an unusual reproductive strategy. The female's mantle protrudes from
5610-434: 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 crown group. Watsonella and Anabarella are perceived to be (earlier) close relatives of these taxa. Only five genera of supposed Cambrian "bivalves" exist,
5712-434: The fish's gills, where they attach and trigger a tissue response that forms a small cyst around each larva. The larvae then feed by breaking down and digesting the tissue of the fish within the cysts. After a few weeks they release themselves from the cysts and fall to the stream bed as juvenile molluscs. Brachiopods are shelled marine organisms that superficially resemble bivalves in that they are of similar size and have
5814-467: The gills are also much longer than those in more primitive bivalves, and are folded over to create a groove through which food can be transported. The structure of the gills varies considerably, and can serve as a useful means for classifying bivalves into groups. A few bivalves, such as the granular poromya ( Poromya granulata ), are carnivorous , eating much larger prey than the tiny microalgae consumed by other bivalves. Muscles draw water in through
5916-595: The high tide mark in the tropical Indo-Pacific on the underside of mangrove leaves, on mangrove branches, and on sea walls in the splash zone . Some freshwater bivalves have very restricted ranges. For example, the Ouachita creekshell mussel, Villosa arkansasensis , is known only from the streams of the Ouachita Mountains in Arkansas and Oklahoma, and like several other freshwater mussel species from
6018-434: The hind parts of the animal. The hemolymph usually lacks any respiratory pigment. In the carnivorous genus Poromya , the hemolymph has red amoebocytes containing a haemoglobin pigment. The paired gills are located posteriorly and consist of hollow tube-like filaments with thin walls for gas exchange . The respiratory demands of bivalves are low, due to their relative inactivity. Some freshwater species, when exposed to
6120-399: The incremental growth bands. The shipworms , in the family Teredinidae have greatly elongated bodies, but their shell valves are much reduced and restricted to the anterior end of the body, where they function as scraping organs that permit the animal to dig tunnels through wood. The main muscular system in bivalves is the posterior and anterior adductor muscles. These muscles connect
6222-526: The inhalant siphon is surrounded by vibration-sensitive tentacles for detecting prey. Many bivalves have no eyes, but a few members of the Arcoidea, Limopsoidea, Mytiloidea, Anomioidea, Ostreoidea, and Limoidea have simple eyes on the margin of the mantle. These consist of a pit of photosensory cells and a lens . Scallops have more complex eyes with a lens, a two-layered retina , and a concave mirror. All bivalves have light-sensitive cells that can detect
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#17327870364526324-421: The inhalant siphon which is modified into a cowl-shaped organ, sucking in prey. The siphon can be retracted quickly and inverted, bringing the prey within reach of the mouth. The gut is modified so that large food particles can be digested. The unusual genus, Entovalva , is endosymbiotic , being found only in the oesophagus of sea cucumbers . It has mantle folds that completely surround its small valves. When
6426-443: The intestine. Waste material is consolidated in the rectum and voided as pellets into the exhalent water stream through an anal pore. Feeding and digestion are synchronized with diurnal and tidal cycles. Carnivorous bivalves generally have reduced crystalline styles and the stomach has thick, muscular walls, extensive cuticular linings and diminished sorting areas and gastric chamber sections. The excretory organs of bivalves are
6528-494: The invasive zebra mussel ( Dreissena polymorpha ). Birds such as the Eurasian oystercatcher ( Haematopus ostralegus ) have specially adapted beaks which can pry open their shells. The herring gull ( Larus argentatus ) sometimes drops heavy shells onto rocks in order to crack them open. Sea otters feed on a variety of bivalve species and have been observed to use stones balanced on their chests as anvils on which to crack open
6630-485: 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 Platyceramus whose fossils measure up to 3,000 mm (118 in) in length. In his 2010 treatise, Compendium of Bivalves , Markus Huber gives the total number of living bivalve species as about 9,200 combined in 106 families. Huber states that
6732-467: The league in the 2014–15 season. In 2014 it was announced that Jenner Park stadium would undergo a £350,000 plus development with the laying of a synthetic pitch. There are several other smaller football clubs in the county such as Llantwit Major F.C. , established in 1962, which competes in the Cymru South , and Penarth Town AFC in the Vale of Glamorgan League . Rugby has a strong presence in
6834-482: The majority of species do not exceed 10 cm (4 in). Bivalves have long been a part of the diet of coastal and riparian human populations. Oysters were cultured in ponds by the Romans, and mariculture has more recently become an important source of bivalves for food. Modern knowledge of molluscan reproductive cycles has led to the development of hatcheries and new culture techniques. A better understanding of
6936-418: The mantle lobes secrete the valves, and the mantle crest secretes the whole hinge mechanism consisting of ligament , byssus threads (where present), and teeth . The posterior mantle edge may have two elongated extensions known as siphons , through one of which water is inhaled, and the other expelled. The siphons retract into a cavity, known as the pallial sinus . The shell grows larger when more material
7038-452: The mantle though the valves. In sedentary or recumbent bivalves that lie on one valve, such as the oysters and scallops, the anterior adductor muscle has been lost and the posterior muscle is positioned centrally. In species that can swim by flapping their valves, a single, central adductor muscle occurs. These muscles are composed of two types of muscle fibres, striated muscle bundles for fast actions and smooth muscle bundles for maintaining
7140-559: The modern administrative area derives its name is the slightly larger, generally low-lying area which extends from the River Kenfig in the west, eastwards as far as the Rhymney . The Pennant Sandstone scarp forms its northern boundary. The largest centre of population in the borough is Barry (51,502 inhabitants). Other towns include Cowbridge (6,180), Dinas Powys (7,799), Llantwit Major (10,621) and Penarth (22,083). Much of
7242-422: The number of 20,000 living species, often encountered in literature, could not be verified and presents the following table to illustrate the known diversity: 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
7344-538: The occasional TV production, including on Doctor Who : as Bad Wolf Bay in " Doomsday " and " Journey's End ", as the surface of the alien planet in " The Time of Angels " and " Flesh and Stone ", and as the engine room of the ark ship in " Dinosaurs on a Spaceship ". It also appeared in Merlin in the first-season episode 'The Labyrinth of Gedref' and in Sherlock during the fourth-season episode 'The Final Problem'. It
7446-507: The others being Tuarangia , Camya and Arhouriella and potentially Buluniella . Bivalve fossils can be formed when the sediment in which the shells are buried hardens into rock. Often, the impression made by the valves remains as the fossil rather than the valves. During the Early Ordovician , a great increase in the diversity of bivalve species occurred, and the dysodont, heterodont, and taxodont dentitions evolved. By
7548-400: The palps. These then sort the particles, rejecting those that are unsuitable or too large to digest, and conveying others to the mouth. In more advanced bivalves, water is drawn into the shell from the posterior ventral surface of the animal, passes upwards through the gills, and doubles back to be expelled just above the intake. There may be two elongated, retractable siphons reaching up to
7650-523: The period is before the larva first feeds, the larger the egg and yolk need to be. The reproductive cost of producing these energy-rich eggs is high and they are usually smaller in number. For example, the Baltic tellin ( Macoma balthica ) produces few, high-energy eggs. The larvae hatching out of these rely on the energy reserves and do not feed. After about four days, they become D-stage larvae, when they first develop hinged, D-shaped valves. These larvae have
7752-554: The population inhabits villages, hamlets and individual farms. The area is low-lying, with a maximum height of 137.3 metres (450 ft) above sea level at Tair Onen to the east of Cowbridge. The borough borders Cardiff to the north east, Rhondda Cynon Taf to the north, Bridgend to the north west and the Bristol Channel to the south. The yellow-grey cliffs on the Glamorgan Heritage Coast (which stretches between Gileston and Ogmore-by-Sea ) are unique on
7854-409: The posterior mantle margins. The organs are usually mechanoreceptors or chemoreceptors , in some cases located on short tentacles . 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 . Statocysts within the organism help the bivalve to sense and correct its orientation. In the order Anomalodesmata ,
7956-425: 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 . 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
8058-527: The prominence of modern bivalves over brachiopods seems due to chance disparities in their response to extinction events . 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
8160-496: The sea cucumber sucks in sediment, the bivalve allows the water to pass over its gills and extracts fine organic particles. To prevent itself from being swept away, it attaches itself with byssal threads to the host 's throat. The sea cucumber is unharmed. The digestive tract of typical bivalves consists of an oesophagus , stomach , and intestine . Protobranch stomachs have a mere sac attached to them while filter-feeding bivalves have elongated rod of solidified mucus referred to as
8262-419: The seabed, one each for the inhalant and exhalant streams of water. The gills of filter-feeding bivalves are known as ctenidia and have become highly modified to increase their ability to capture food. For example, the cilia on the gills, which originally served to remove unwanted sediment, have become adapted to capture food particles, and transport them in a steady stream of mucus to the mouth. The filaments of
8364-469: The sediment remains damp even when the tide is out. When buried in the sediment, burrowing bivalves are protected from the pounding of waves, desiccation, and overheating during low tide, and variations in salinity caused by rainwater. They are also out of the reach of many predators. Their general strategy is to extend their siphons to the surface for feeding and respiration during high tide, but to descend to greater depths or keep their shell tightly shut when
8466-435: The shell and develops into an imitation small fish, complete with fish-like markings and false eyes. This decoy moves in the current and attracts the attention of real fish. Some fish see the decoy as prey, while others see a conspecific . They approach for a closer look and the mussel releases huge numbers of larvae from its gills, dousing the inquisitive fish with its tiny, parasitic young. These glochidia larvae are drawn into
8568-468: The shell is the periostracum , a thin layer composed of horny conchiolin . The periostracum is secreted by the outer mantle and is easily abraded. The outer surface of the valves is often sculpted, with clams often having concentric striations, scallops having radial ribs and oysters a latticework of irregular markings. In all molluscs, the mantle forms a thin membrane that covers the animal's body and extends out from it in flaps or lobes. In bivalves,
8670-571: The shell, gaining the ability to swim, and in a few cases, adopting predatory habits. For a long time, bivalves were thought to be better adapted to aquatic life than brachiopods were, outcompeting and relegating them to minor niches in later ages. These two taxa appeared in textbooks as an example of replacement by competition. Evidence given for this included the fact that bivalves needed less food to subsist because of their energetically efficient ligament-muscle system for opening and closing valves. All this has been broadly disproven, though; rather,
8772-420: The shells and open them more easily when they could tackle them from different angles. Octopuses either pull bivalves apart by force, or they bore a hole into the shell and insert a digestive fluid before sucking out the liquified contents. Certain carnivorous gastropod snails such as whelks ( Buccinidae ) and murex snails ( Muricidae ) feed on bivalves by boring into their shells. A dog whelk ( Nucella ) drills
8874-400: The shells with their pincers and starfish use their water vascular system to force the valves apart and then insert part of their stomach between the valves to digest the bivalve's body. It has been found experimentally that both crabs and starfish preferred molluscs that are attached by byssus threads to ones that are cemented to the substrate. This was probably because they could manipulate
8976-740: The shells. The Pacific walrus ( Odobenus rosmarus divergens ) is one of the main predators feeding on bivalves in Arctic waters. Shellfish have formed part of the human diet since prehistoric times, a fact evidenced by the remains of mollusc shells found in ancient middens. Examinations of these deposits in Peru has provided a means of dating long past El Niño events because of the disruption these caused to bivalve shell growth. Further changes in shell development due to environmental stress has also been suggested to cause increased mortality in oysters due to reduced shell strength. Invertebrate predators include crustaceans, starfish and octopuses. Crustaceans crack
9078-484: The soil allows crops to be grown which would be difficult elsewhere in Wales. The Liassic limestone and Carboniferous Limestone are also used in the Vale as building materials; in previous centuries it was taken by sloops across the Bristol Channel to North Cornish ports such as Bude, Boscastle and Port Isaac to fertilise Cornwall's poor slate soils; the hard Devonian slate was brought back from Cornwall as
9180-422: The southeast is separated by a headland on which are the remains of Dunraven Castle (Welsh: Castell Dwnrhefn). This beach is lesser used for inconvenience and severing of its land link — it has access by steep steps that reach the beach/sea away from the cliffs which has led to people having to wait for the tide to change at high tide . It stretches to Nash Point near Llantwit Major . It has been used in
9282-584: The southeastern US, it is in danger of extinction. In contrast, a few species of freshwater bivalves, including the golden mussel ( Limnoperna fortunei ), are dramatically increasing their ranges. The golden mussel has spread from Southeast Asia to Argentina, where it has become an invasive species . Another well-travelled freshwater bivalve, the zebra mussel ( Dreissena polymorpha ) originated in southeastern Russia, and has been accidentally introduced to inland waterways in North America and Europe, where
9384-416: The species damages water installations and disrupts local ecosystems . 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
9486-590: The tide goes out. They use their muscular foot to dig into the substrate. To do this, the animal relaxes its adductor muscles and opens its shell wide to anchor itself in position while it extends its foot downwards into the substrate. Then it dilates the tip of its foot, retracts the adductor muscles to close the shell, shortens its foot and draws itself downwards. This series of actions is repeated to dig deeper. Other bivalves, such as mussels , attach themselves to hard surfaces using tough byssus threads made of collagen and elastin proteins. Some species, including
9588-558: The true oysters, the jewel boxes , the jingle shells , the thorny oysters and the kitten's paws , cement themselves to stones, rock or larger dead shells. In oysters, the lower valve may be almost flat while the upper valve develops layer upon layer of thin horny material reinforced with calcium carbonate. Oysters sometimes occur in dense beds in the neritic zone and, like most bivalves, are filter feeders. Bivalves filter large amounts of water to feed and breathe but they are not permanently open. They regularly shut their valves to enter
9690-402: The two valves and contract to close the shell. The valves are also joined dorsally by the hinge ligament , which is an extension of the periostracum. The ligament is responsible for opening the shell, and works against the adductor muscles when the animal opens and closes. Retractor muscles connect the mantle to the edge of the shell, along a line known as the pallial line . These muscles pull
9792-592: The west, was the seat of several high sheriffs of Glamorganshire , including John Curre who was known to have occupied the estate in 1712. William Curre, known to have lived in Clemenstone in 1766, was also an occupant of Itton Court in Monmouthshire . In the early 19th century, Lady Sale née Wynch, wife of Sir Robert Sale , spent much of her early life on the Clemenstone Estate. In 1974,
9894-494: The west. Since 1996 local government is led by Vale of Glamorgan Council . The Labour Party had a large majority initially, though between 1999 and 2012 the Conservatives were the largest group. Since 2017, there has been no overall political majority on council. All except one (Rhoose) of the Vale's communities elects a community (or town) council, the lowest tier of local government. The principal football club in
9996-417: The young inside their mantle cavity, eventually releasing them into the water column as veliger larvae or as crawl-away juveniles. Most of the bivalve larvae that hatch from eggs in the water column feed on diatoms or other phytoplankton. In temperate regions, about 25% of species are lecithotrophic , depending on nutrients stored in the yolk of the egg where the main energy source is lipids . The longer
10098-611: Was a turbulent time for governance in the city of Cardiff, as for the first time in its history it had to share authority with the county council, which was larger and better resourced. In April 1996, the Vale of Glamorgan became a county borough (unitary authority) of Wales. Located immediately to the west of Cardiff between the M4 motorway and the Severn Estuary , the county borough of Vale of Glamorgan covers 33,097 hectares (130 square miles) and has 53 km (33 mi) of coastline. The physiographical district from which
10200-808: Was also featured in the Bob Dylan film Hearts of Fire , with Dylan looking out over the second beach down onto Rupert Everett . During the summer, Southerndown Lifesaving Club use the beach as opposed to St Donat's Castle. Adjoining is Southerndown Golf Club . The Southerndown Cliffs are a suicide spot. All the rocks exposed in the area of Southerndown are sedimentary rocks. They were laid down as deposits of mud, silt, sand and lime (calcium-rich deposits from shells and bones) that, over long periods of time, were compacted and solidified into limestone, shale (compacted mud) and conglomerate (rock of pebbles of various size). The oldest rocks are hard, grey, often shelly, Carboniferous Limestone . These were laid down in
10302-452: Was determined to be the wealthiest area in Wales in a 2003 survey conducted by Barclays Bank that measured disposable income . Chemical industries are located to the east of the port of Barry while further inland the main activity is agriculture, especially beef and dairy cattle, with marketing facilities at Cowbridge. The Vale of Glamorgan UK parliament and Senedd constituencies (which do not include Penarth and Sully which are in
10404-473: Was very common along the coast. Nash Point , Southerndown and Ogmore-by-Sea have some of the highest shipwreck victims on the coast of Wales; as recently as 1962 an oil tanker, the BP Driver, crashed into Nash Point during a violent westerly storm, was torn to shreds by the reefs and eventually sank, although the crew were saved by various Bristol Channel lifeboats and helicopters. The Vale of Glamorgan
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