Class Bivalvia, powerpoint

Class Bivalvia

Parts of bivalve shell

ANISOMYARIAN. Shell with the anterior adductor muscle much reduced or absent.

HETEROMYARIAN. With one adductor muscle (anterior) much reduced. ISOMYARIAN. With two adductor muscles equal in size, or almost so.

With distinctly differentiated cardinal and lateral teeth. Heterodont- With small, weak teeth close to beaks. Dysodont- With heavy, blunt, amorphous teeth. Pachydont-

With one tooth, median of left valve, broad and bifid. Schizodont-

numerous alternating small teeth and sockets occur along the hinge of a bivalve shell, some or all transverse to the hinge margin.

Taxodont-

HINGE AREA NOMENCLATURE

Dysodont Heterodont

Taxodont Schizodont

Pachydont

Types of bivalve hinge teeth

Life habits of bivalvesEpifaunal suspension feeder, one valve cemented to

substrate (oysters) Epifaunal suspension feeder, attached by byssus (mussels) Infaunal siphonate suspension feeders, rock boring (Pholas) Infaunal non-siphonate suspension feeder, partly buried (pen

shells) Infaunal non-siphonate deposit feeder, partly buried (nucula)

Infaunal siphonate deposit feeders, completely buried (Yoldia, tellina)

Infaunal mucus tube feeder, deeply buried (lucinids) Infaunal siphonate suspension feeder, deeply buried (Mya,

Mercinaria) Infaunal siphonate carnivores (Cuspidaria)

a)-(d) Surface dwelling, suspension-feeding bivalves: (a) Crassostrea, a cementer; (b) Pecten, a bivalve capable of short pulses of swimming; (c), (d) Pinctada (pearl oyster) and Mytilus (mussel), moored to the substrate by organic threads. (e)-(o) Bivalves living within rock or sediment substrates: (e) Pholas, a rock-borer; (f) Hiatella, a rock nestler; (g), (h) Nucula and Yoldia, shallow-burrowing deposit feeders; (i) Atrina, a semiinfaunal bivalve; (l) Mya, a relatively deep infaunal suspension feeder: (m) Mercenaria, a shallow infaunal suspension feeder; (n) Tellina, infaunal deposit feeder: and (o) Cuspidaria, an infaunal carnivore.

Diagram of parts of typical Pholas shell

Nucula sulcataYoldia glaucaLucina

Mya arenaria

Cuspidaria nobilis

Subclass Pteriomorphia

Epibenthic; most are attached by byssus threads; with lamellibranch gills; includes mussels, scallops, penshells, and oysters

Order ArcoidaMostly epibyssate, some cemented; mostly marine; shell solid, elongate or circular-oval, often heavily ribbed; periostracum fibrous; well-developed taxodont dentition; hinge straight; filterfeeders

Arca clathrata

Arca turonicaArca barbata

Order Arcoida

Anadara ovalis, Brugiere

Anadara notabilis

Anadara granosa

Order Mytiloida

Two valves equal except in oysters and some scallops, but each very inequilateral

Mytilus edulis

Mytilus edulis

Perna viridis

Pinna nobilis

Pinctada margaritifera

Pteria penguin

Ostrea edulis

Crassostrea gigas

Chlamys nobilis

Pecten

Spondylus imperialisS. japonicus

Subclass Paleoheterodonta

Order Unionoida (freshwater bivalves)

Anodonta cignea

Unio tumidus

conglutinateglochidia

Subclass Heterodonta- shell w/o nacreous layer; siphons usually present; gills lamellibranchiate

Order Veneroida

Trachycardium magnum

Dreissenia polymorpha

Callista erycina (Venus clams)

Tridacna gigas

Order Myoida

Pholas sp. (Pholadidae)

Teredo navalis

Teredinidae (woodboring shipworms)

Bactronophorus thoracites