Ryan Photographic - Bivalvia - Clams, mussels, oysters etc.


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Class Bivalvia

As and when I get more photographs of bivalves I will probably split them into orders - as there are 106 families I doubt I'll ever get to the family level. But for now, when I have relatively few species, it makes more sense to bundle them together. There are currently around 9,200 bivalve species but new ones are being added on a regular basis. Bivalves are found in fresh, brackish and marine waters. Humans have long exploitd these shellfish - mainly for food but also for money and decoration. A still hinged pair of bivalve shells makes a very handy tweezers and some cultures used these to pull beard hairs. Many bivalves live buried in sand or mud with only their inhalent and exhalent siphons visible. A strong muscular foot enables them to retract into the sand or bury themselves if they are exposed. Their primary predators are sea stars which are able to exert force over a long enough period of time that the adductor muscles of the bivalve become weakened and the shells slowly open.

Mussels and oysters are able to attach themselves to rocks even in very strong surge conditions and their quick drying biological cements have come under scrutiny from materials scientists. Pearl oysters ae cultured for their exquisite pearls and mussel farms provide fresh, frozen and smoked animals to the markets.

Most bivalves are filter feeders. They pump water in through a siphon and pass it over feeding/respiratory structures called ctenidia. Labial palps scrape food off the ctenidia and pass it to the mouth. A few specialized bivalves, such as the shipworm, live in wood. Once sustained purely by timber washed down rivers and streams they found human vessels very much to their liking. Many ships, their timbers weakened by ship worm, sank without trace. Eventually we learned to sheath the hulls of our boats with copper and thus kept the shipworms at bay. The advent of iron ships mostly did away with the problem.

In the Great Lakes of the United States, the zebra mussel causes economic damage as the tiny bivalves clog up cooling water and other intakes.

Some bivalves such as the scallop can swim up opening and closing their valves. They typically do this to avoid predation.

Most bivalves release eggs and sperm into the water. The fertilized egg develops into a free-swimming larvae. In some freshwater mussels the eggs are internally fertilized and remain within the female until they become glochidia. Some mussels develop an appendage that looks like a bait fish to the larger fish predators. When they come to investigate, the mussel spits the glochidia into the mouth of the fish. The glochidia clamp onto the gills of fish and feed on the blood until they release and settle on the bottom in a filter feeding mode.

 

Atrina pectinata

Atrina pectinata Puerto Galera, Philippines

MOLL 7439 Atrina pectinata Puerto Galera, Philippines.

Atrina zelandica New Zealand horse mussel

New Zealand horse mussel

Atrina zelandica New Zealand horse mussel, Fiordland, New Zealand.

Ctenoides ales Electric clam

Electric clam

MOLL 1945 Ctenoides ales Electric clam, Raja Ampat, West Papua

electric clam

MOLL 1947 Ctenoides ales Electric clam, Raja Ampat, West Papua

Pecten novaezelandiae Common scallop

common New Zealand scallop

Pecten novaezelandiae Common scallop, Fiordland,New Zealand.

common scallop closeup

Pecten novaezelandiae Common scallop, close-up, Fiordland,New Zealand.

Pedum species

Pedum species

MOLL 2744 Pedum species (maybe) Raja Ampat, West Papua.

Pedum spondyloideum

Pedum clam

MOLL 9329 Pedum spondyloideum, Kadavu, Fiji

Pedum

Pedum spondyloideum, Kadavu, Fiji

Pteria penguin Penguin wing oyster

penguin oyster

MOLL 2745 Pteria penguin Penguin wing oyster on Antipatharian coral, the shell is covered by an encrusting sponge and several ascidians. Raja Ampat, West Papua.

MOLL 2744 Pteria penguin Penguin wing oyster on Antipatharian coral, the shell is covered by an encrusting sponge and several ascidians, Raja Ampat, West Papua.

Pteria tortirostris

oyster on black coral

MOLL 3641 Pteria tortirostris (maybe), Raja Ampat, West Papua

Spondylus varians Variable thorny oyster

thorny oyster

MOLL 1934 Spondylus varians Variable thorny oyster, Raja Ampat, West Papua.

thorny oyster mantle detail

MOLL 1475 Spondylus varians Variable thorny oyster mantle detail Raja Ampat, West Papua.

thorny oyster mantle detail

Spondylus varians Variable thorny oyster mantle detail, Fiji.

Tridacna crocea Burrowing clam

Tridacna corcea burrowing clam

MOLL 4248 Tridacna crocea Burrowing clam, Kri Eco, Raja Ampat, West Papua

Tridacna gigas Giant clam

tridacna gigas, giant clam

MOLL 9417 Tridacna gigas, Giant clam, Raja Ampat, West Papua. This arguably one of the world's biggest giant clams. It is as long as my outstretched arms.

World's largest giant clam?

MOLL 9409 Tridacna gigas, Giant clam, Raja Ampat, West Papua. The world's largest giant clam?

Tridacna gigas and Kerstin Rawlins Kri Eco, Raja Ampa

MOLL 2117 Tridacna gigas and Kerstin Rawlins Kri Eco, Raja Ampat.

Giant clam in Fiji

IMG 3530 Tridacna gigas, Giant clam, Mamanucas, Fiji.

Tridacna maxima Maxima giant clam

Tridacna maxima Maxima giant clam, Ledge-end, GBR IMG_8223.jpg

MOLL 8223 Tridacna maxima Maxima giant clam, Ledge-end, Great Barrier Reef.

 

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