Guide to Families 29 BIVALVES
Coastal species are of great interest to fisheries and have potential for exportation for eating purposes. Bivalves are caught mainly by divers and are also fished for pearls. Their flesh is of excellent quality. Since oysters remain alive out of the water for over 12 hours, they may exported to far destinations when still alive. Moreover, some species are collected for their nacreous shell and ability to develop pearls. The shell can be used in the mother of pearl industry. The “Guide to Families’’ andTECHNICAL ‘‘Guide to Species’’ TERMS include 5AND families MEASUREMENTS and 10 species, respectively.
posterior adductor cardinal tooth muscle scar
lateral tooth
Posterior Anterior margin margin shell height
anterior adductor muscle scar
pallial sinus pallial shell length line left valve (interior) Ventral margin
ligament left valve
right valve lunule
umbo Adductor muscle: Byssus: Chomata: Muscle connecting the two valves of a shell, tending to draw them together. Hinge: Clump of horny threads spun by the foot, by which a Bivalve can anchor to a hard substrate. Ligament: Small denticles and corresponding pits located on the inner margin of the valves (Ostreidae and Gryphaeidae). Mantle: Top interlocking margin of the valves, often with shelly projections (teeth) and corresponding recesses (sockets). Muscle scar: Horny, elastic structure joining the two valves dorsally. Pallial line: Fleshy sheet surrounding vital organs and composed of two lobes, one lining and secreting each valve. Umbo: Impression marking the place of attachment of a muscle inside the shell. A line near the internal margin of valve, marking the site of attachment of the mantle edge. The first formed part of a valve, usually above the hinge. 30 Bivalves GUIDE TO FAMILIES
PTERIIDAE Page 32
Pearl oysters § hinge line straight, teeth reduced to absent anterior ear posterior ear To about 20 cm. Marine. Two species of interest to fisheries are included in the Guide to Species.
nacreous area interior with Shell compressed, with scaly to lamellar surface
posterior adductor scar large pallial line
without sinus left valve (interior)
PECTINIDAE Page 32
Scallops §
hinge line straight, with To about 11 cm. Marine and brackish waters; umbo median well developed ears benthic. Two species of interest to fisheries are anterior ear included in the Guide to Species. ligament internal, pointing under umbo single posterior adductor scar anterior ear byssal notch on
Shell more or less pallial line inequivalve, with well developed radial ribs right valve (interior) without sinus GRYPHAEIDAE Page 33
Honeycomb oysters §
ligamental area with To about 30 cm. Marine. One species of interest to shallow median pit fisheries is included in the Guide to Species.
chomata long and sinuous, branched single posterior adductor scar
Shell irregularly shaped, inequivalve, cemented to substrate by left valve
shell structure vesicular (most visible near internal margins) GuideOSTREIDAE to Families Page 3331
ligamental area with Oysters § shallow median pit
To about 20 cm. Marine and estuarine. Three species chomata when of interest to fisheries are included in the Guide to present, simple Species. and short
Shell irregularly shaped, inequivalve, cemented to substrate by left valve
single posterior adductor scar
TRIDACNIDAE Page 34
Giant clams §
ligament two ridge–like byssal gape plicate, To about 35 cm. Marine. Two species of interest to teeth near the umbo fisheries are included in the Guide to Species. external
strong radial folds Shell thick and heavy, with
single posterior adductor
retractor scar scar, associated a foot 32 - Pteriidae - Pectinidae
PTERIIDAE Bivalves
Pinctada margaritifera FAO names: §
§ Black–lip pearl oyster (En)
Local name(s): N: § (Linnaeus, 1758) Pintadine á lèvre noire (Fr) Habitat: Gregarious species often forming natural Shaza; S: Shaza (M/K). Hinge without Anterioranterior margin ear strongly teeth protruding beyond tip of Fisheries:beds in littoral and sub–littoral zones, attached by Distinctivebyssus, at least Characters: in the young stages. Hands and knife. Shell rather thick and large, sub–circular in outline; outer surface of valves, when not worn, with densely set, flattened, imbricating concentric scales and moderately long, parallel–sided and flattened spines with tapering or rounded ends; spines lying relatively flat on Colour:surface of valves, arranged in radial rows and often strongly projecting on shell margins. Non nacreous Nacreous area often Outside greyish brown or grey, with radial Size: stripes of white spots. margin very dark with dark border To 9.8 cm (TL) * Pinctada radiata FAO names: §
Pintadine radiée § Rayed pearl oyster (En)
Local name(s): N: (Leach,§ 1814) (Fr) Habitat: Shaza; S: Shaza (M/K). Hinge with 2 Anterior margin slightly protruding or small teeth not at all beyond tip of anterior ear Byssally attached to seagrass leaves, rocks, dead corals and various hard objects often Fisheries:forming natural banks from low tide levels to Distinctiveslightly deeper Characters: waters. Maximum depth 30 m. Hands and knife. Shell rather thin and small; outer surface of shell, with densely set, appressed and flattened, imbricating concentric Colour:scales and moderately small, radially projecting spines mostly preserved towards the margins. Remarks: Outside tan to brown or reddish, often with darker radial bands. Size: Collected for its edible muscle, nacreous To 9.5 cm (SH) shell and ability to develop pearls. PECTINIDAE
Chlamys senatoria FAO names: §
Pétocle sénateur § Senatorial scallop (En)
Local name(s): N: (Gmelin,§ 1791) (Fr) Habitat: Shaza; S: Shaza (M/K). Anterior ear much 22 or more shallow radial ribs, with larger than posterior relatively fine transverse scales Attached by byssus to hard elements, usually in sandy to muddy bottoms with gravel, Fisheries:coral and shell debris or rocks littoral and sub– Distinctivelittoral zones. Characters: Hands and knife. Shell solid, medium sized, higher than long and rounded–ovate in outline; both valves convex and subequal, the right (lower) valve a little flatter than the left (upper) Colour:valve; interior shiny, with low, rounded radial ribs ',Ì corresponding to the outer sculpture. Size: Yellow to reddish brown with creamy patches. To 8 cm (SH) Guide to Species Pectinidae - Gryphaeidae - Ostreidae - 33 Gloripallium pallium FAO names: §
Pétoncle manteau § Royal cloak scallop (En)
Local name(s): N: § (Linnaeus, 1758) (Fr) Habitat: Anterior ear slightly Shaza; S: Shaza (M/K). larger than posterior Attached by byssus under coral heads and Fisheries:rocks in the intertidal and littoral zones, to about Distinctive30 m. Characters: Hands and knife. Colour: About 13 large radial ribs, with strongly projecting transverse lamellae. Various shades of deep reddish purple, with roughly concentric whitish maculations.
Size:
To 11 cm (SH) GRYPHAEIDAE
Hyotissa hyotis FAO names: §
§ Honeycomb oyster (En)
(Linnaeus,§ 1758) Local name(s): N: Pycnodonte géante (Fr) Habitat: Shaza; S: Shaza (M/K). Cemented to hard substrate, mostly in Fisheries:coral reefs areas and in littoral to shallow sub–tidal Distinctivezones. Characters: Hands and knife. Colour: Shell large and thick, sub– orbicular in outline. Interior milky–white, becoming brown to black on periphery.
plicate Margins strongly Radial ribs large with imbricated lamellae giving a few tubular spines Size:
To 30 cm (SH) OSTREIDAE
Lopha cristagalli FAO names: §
§ Cock’s comb oyster (En)
Local name(s): N: (Linnaeus,§ 1758) Huître crête–de–coq (Fr) Habitat: Shaza; S: Shaza (M/K). Attached to rocks or corals by clasping Fisheries:spines of the left valve from the intertidal zone to Distinctiveabout 30 m. Characters: Hands and knife. Surface roughened by many small rounded protuberances; a few sharp– Colour:edged radial folds; peripheral margin finely granulose; recurred clasping spines. Dull brown to deep purple.
clasping spines Peripheral margin Recurved Size: finely granulose To 20 cm (SH) (Fr) (Fr) (Fr) § § § (En) (En) (En) § § § valves Bi To 40 cm (SH) Size: To To 35 cm (SH) Size: To To 20 cm (SH) Size: To Hooded oyster oyster Hooded Bénitier allongé Huître capuchon capuchon Huître Bénitier écailleux Fluted giant clam Fluted Undulating Elongate giant clam Elongate reduced marginal folds marginal Byssal openingByssal names: FAO
,¡i names: FAO / names: FAO Crescent–like Crescent–like - pallial imprints with blade–like projecting scales projecting Strong radial ribs radial Strong broad hinge elongate ribs narrow Posterior end Posterior Byssal openingByssal Recess underRecess Spaces between TRIDACNIDAE TRIDACNIDAE ; S: Shaza (M/K); S: Shaza ; S: Shaza (M/K). ; S: Shaza ; S: Shaza (M/K). ; S: Shaza § § § Shell exceedingly variable variable exceedingly Shell
Lamarck, 1819 squamosa Lamarck, Tridacna (Röding, 1798) maxima (Röding, Tridacna (Born, 1778) (Born, cucullata Saccostrea Attached by byssus to the to of surface coral byssus by Habitat: Attached waters. and shallow in littoral reefs, hands. by Fisheries: Caught Umbo Characters: submedian; spaces Distinctive shell sub equilateral. ribs large; between Colour: Greyish white, sometimes orange. tinged with Occurs on reefs, particularly embedded in embedded particularly reefs, on Occurs Habitat: subtidal waters. and shallow littoral in corals, hands. by Fisheries: Caught Characters: Distinctive Umbones ribs. radial scaly stout anteriorly; situated or yellow with tinged often Greyish–white, Colour: orange. Habitat: Attached to various hard substrates marine in to estuarine waters; gregarious environments species in often forming colonies. shallow dense and knife. Fisheries: Hands Characters: Distinctive developed. in shape; chomata well black. deep purple to margins Internal Colour: N: Shaza Local name(s): N: Shaza Local name(s): N: Shaza Local name(s): - Ostreidae - Tridacnidae Ostreidae 34 -