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Home , Hinge teeth, Lira (mollusc), Pallial line, Pallial sinus, Resilifer, Spadix (zoology)

Phuhet Marine Biological Center Special Publication 21(3): 551-581 (2000) 551

ILLUSTRA TED DICTIONARY TECHNICAL TERMS AND COMMON WORDS USED IN DESCRIPTIONS OF BTVALVES

Jorgen Hylleberg

Institute of Biological Sciences Aarhus Uniuersity, Denmarh, Programme (TMMP) 552 Tlopical Marine Mollusc abaxial away from the shell axis. wards the other. Each adductor has a slow abduction movement away from the me- component (smooth muscle fibres) and fast dian axis. (striated muscle fibres). Terms relating to abductive adj. deived.from abductiorr, e.g. adductor muscle scars are also used for the abductive thrust. muscles themselves (;llD. See anterior, pos- abductor a muscle that moves something terior, equal, dimyarian, heteromyarian, outwards. monomyarian, subcentral, lucinoid, or pe- acentric see oblique sculpture, ripheral. scissulate sculpture. adnate joined to another organ of a differ- aciculate slender, tapering to sharp point. ent kind, e.g. the anterior adductor mus- actinodont teeth radiating from the um- cle joined with the pallial muscle. Syno- bones, the outer ones being longer and nym conjoined. close to the dorsal shell margin; seen in adult individuals have acquired capacity early Palaeozoic fossil bivalves. of reproducing. Juvenile and adult shells acuminate having a very sharp tapering may appear very different. See sculptural point. Compare change. with acute. adventitious accidental, found in an unu- acute ending in sual place. Term used about . a sharp point ala wing-Iike projection. (illu.). alae plur. of alaOttu.). acute the dorsal section of alate having a wing-Iike extension (ales the paIIiaI sinus may meet the ventral sec- Lat. = winged). tion directly yielding a sinus ending in a sharp point. acute rib profile ribs terminate in sharp points in a cross-section. adaptation evolutionary process by which an organism becomes fitted to its environ- ment. adaptive capable of frtting different condi- tions. adaptiveradiation evolutionaryprocess in which species descend from a common ancestor, multiply and diverge to occupy alimentary related to food uptake. different ecological niches. alivincularligament aflat,subtriangu- adaxial towards shell axis. lar in a alivincular adduction movementtowards the median subcentral position, ligament axis. extending from one adductor a muscle that brings one part to- to the other (iud.Typical of anterior adductor posterior adductor Lima, muscle scar muscle scar , and Auicula (aIes Lat. = winged; vinculum Lat. = band) amphidetic ligamentextendingbehind and in front of umbo, e.g. in Glycymeris andArcu (amphi Gr. = on both sides; daetos Phuket Marine Biological Center Special Publication 21(3): 551-581 (2000) 553

Gr. = tied together). appressed pressed together without being anachomata tubercles on the left united. margin of pteriomorphs. See chomata. aragonite a crystalline form of calcite, one anal derived from anus. of the constituents of bivalve shells. The anal = exhalant siphon. crystalline structure differs from calcite analogue structures similar in function but but the chemical composition is identical of different evolutionary origin. (calcium carbonate). analogous derived from analogue. arborescent branching, treelike. analogous teeth withsimilarfunctionbut archaic form belonging to or characteris- of different developmental and evolution- tic of a much earlier period (arkhein Gr. = ary origin. See crura. to begin). androgenous producing only male off- arciform shell shape like inArco. spring. arcuate shaped like an arch (arcus Lat. = angle of pallial sinus the ventral part of arch), e.g. many hinge-plates. the pallial sinus may meet the pallial iine areas shell areas demarcated by angles or at an angle. ridges running from the umbo toward the angulated edge along which two surfaces shell margin. meet at an angle. ascending pallial sinus the dorsal sec- anisomyaria group ofbivalves having an- tion ofthe pallial sinus is directed towards terior adductor muscles strongly reduced the umbo. or absent (an Gr. = without; isos Gr. = asiphonate absence ofsiphons, e.g. Lima, same; myos Gr. = muscle). Nucula, Pecten, Tfigonia. annulate with small rings. auricle ear-like extension on the dorsal antagonistic counteracting the effect of margin of shells in another, e.g. ligament and adductors. pectinids, limids, nearer the mouth. 2111isls anterior spondylids. - anterior adductor the adductor muscle auricle nearer the mouth. atrium of the anteroventral composed of anterior and heart. See auricle ventral, e.g. t}i'e notch may be in pericardium - an anterior position on the ventral mar- (illu.). gin. auriculate eared, having expanded bases. antecedent something that happened be- auricularctltta seecrura. fore another. aurifom ear-shaped. antecedents plur. ancestry, past history of Australian region the zoogeographical a species. region comprising former New Guinea, anus posterior opening of the alimentary Australia, New Zealand, the westernmost canal through which faeces is voided. groups of South Pacific islands, and in , tip or summit on the umbo. First- some taxa parts of the Indonesian Archi- formed part of shell. See . pelago east ofJava and Sulawesi. apices plur. of apex. autopormorphy a derived feature or char- apomorphy an advanced or derived fea- acter state unique to a particular taxon. ture. Term used in cladistic analyses. aviculoid formed like a claw. apportion ub. to divide shares of, allot pro- axial parallel or subparallel with shell axis. portionally. axis imaginary line through shell apex. apposition putting into juxtaposition, axis of revolution the laws of mechanics placed close together, or laying down of requires that this axis must be a straight material on a preformed surface. line. The part of the hinge-line function- 554 Tlopical Marine Mollusc Programme (TMMP)

ing in connection with the ligament in bisexual having both male and female re- opening and closing must be straight. productive organs. bacteriocyte symbiotic bacteria vacuoles bioturbation mixing of sediments due to in subfiIamental tissues of lucinoid gi1ls. digging, feeding, or other activities of an beak older part animal.

of a bivalve beak blood typically, bivalve blood is without pig- shell containing ment except some members of the Arcoidea the larval shell (blood cockles). (illu.). blood cells two main types occur; hyaline (See apex, opisthogSros, orthogyros, pro- Ieucocytes and granular leucocytes. Alter- dissoconch, prosog"yrous, umbo). native spelling is leukocyte. benthic derived from benthos. branchiae plur. giIls. benthos fauna living on the bottom. branchial pertaining to gills. bialate having two wing-Iike extensions branchial a septum below the (illu.). anal chamber in Pholadomyidae. branchial siphon see inhalant siphon branchiate related to gills. breath maximum inflation of shells when joined together. byssiferous foot carrying a byssus. byssal drifting use of byssus for drifting in the late pelagic stage. byssal gape ventral or ventrolateral gape for passage of, and accommodation of a bifrd tooth cardinal teeth bifid at the sum- large byssus (= byssal notch). mit. byssal hair hairs secreted by the byssus bifurcate forked, V-shaped, split into two gland and put in position on the shell sur- branches. face by the foot. Characteristic of m1'tilids. bifurcating rib the top of a radial rib is byssus tuft of tough strings by which bi- split to yield two smaller ridges (iltu.). valve species may attach to a substratum (byssos Gr. = frne fabric). byssalnotch ribs bifurcating the byssal notch I always lies l(" in the anterior \J or anteroventral part ofthe shell (illu), e.8., bioindicator species which can indicate and Chamidae. conditions ofa particular habitat. In gen- byssus gland abyssogenous eral, suspension-feedingbivalves are use- gland on the foot. ful indicators ofwater qualitybecause they byssusretractor digest a variety of suspended particles, separate muscles to including material derived from pollution. retract byssus in bipectinate structures having the two mybilids and anomids. edges furnished with teeth like a comb. byssusretractor scar Refers to ctenidia bearing two rows of gill scar (iltu.) from the leaflets. byssus retractor muscle. Phuhet Marine Biological Center Special Publication 21(3): 551-581 (2000) 555

caecum the blind end ofan area or ducU catachomata tubercles on the right valve sorting area in posterior part of stomach. margin of pteriomorphs. See chomata. calcareous matter chiefly composed of cal- cellulo-crystalline shell material com- cium carbonate. posed of small cavities having the struc- calcite crystalline forms of calcium carbon- ture ofcrystals ate (iltu.). Compare aragonite. cerebral from Greek: ofthe brain. cerebral ganglia are normally fused with pleural ganglia in bivalves, and quite sepa- rate from the visceral ganglia, but visceral brains do occur. See cerebrovisceral. cerebrovisceral nervefibresconnecting cerebral ("brain") and visceral ganglia. cerebrovisceral commissure a band of callous coated with . nerve tissue connecting cerebral and vis- callum secondary calcareous structure se- ceral ganglia. creted over the pedal gape in some Phola- chevron oblique che didae. pattern formed callus thickening of shell with calcareous by lamellar bands substance secreted by the general surface of duplivincular of the . ligaments (illu.). cancellate radial and concentric sculpture chevrongroove intersect each other to form small rectan- part of cardinal gular blocks ftttu.) (cancelli trq|. = grid). area for ligament insertion in some pte- riomorphs. chitin a white, insoluble horny polysaccha- ride (composed of acetyl-glucosamine). chitinous composed of or the nature of chi- tin. capacious capable of holding much. cardinal teeth located on the , radiating from the umbo Ottu.). See (cardinalis Lat. = peg in the hinge of a door).

cardinal l.eeth

carina appliedto narrow ridge or keel on body chomata small marginal tubercles or or shell, e.g. an elevated ridges and corresponding pits, on internal ridge demarcating surfaces typically close to the hinge, but the posterior area extending around the margin in some spe- (illu.). cies, e.g. . Termed catachomata on carinate bearing the right valve and anachomata on the left a keel (carina). yalve 1ltu.). Programme (TMMP) 556 Tlopical Marine Mollusc chondrophore hollowed out and project- comarginal following the contour of the ing shelly part on the hinge-Iine. The elas- shell margin. tic material of the is set in the comarginal sculpture see concentric. chondrophore (illu.). Presence of a large commarginal alternative spelling of resilifer or a small chondrophore makes a comarginal. distinction commissure band of neural tissue linking

between chondrophore two sides of a nervous system. these two commissure the joining line between two terms N parts. difficult. complete without indented cilia motile, margin. thin hair-like concentric sculpture commonly used to ciliary outgrowth from junctions describe comarginal sculpture on shell the surface of surfaces. The term concentric is incorrect cells capable in a strict sense since concentric refers to of producing circles having the same centre. Concentric a flow of sculpture may be occur as lines, Iirations, material ridges, or be foliacious. In cross section the over the cell sculpture may be downcurved, recurved, surface. rounded, or vertical Ollr). ciliaryjunctions pertains concentric sculpture cilia joining neighbouring cells on the gllIs Ollu.). clade a taxonomic group consisting of an ancestral taxon and its descendants. cladistic adj. analyses of similarities be- tween species or other taxa due to recent conchin synonym of conchiolin. origin from a common ancestor. conchiolin the protein component of liga- clathrate having radial and concentric ment and periostracum (illu.). components that intersect to form a broad lattice. clavate club-shaped, thickened at one end (clavus = club) clutch number of eggs laid by one female at one time. species ofCardiidae, but also used for similar species with a rounded shell and radial ribbing like the unrelatedAna- dara. coelom body cavity formed within, and Iined with mesoderm; the true body cav- ity, which in bivalves comprises little more than the pericardium, including kidneys conchology the study of molluscan shells. and ducts from the gonad. concomitant adj. [on] occurringtogether. coelomoduct synonym of renal organs or confluent pallial sinus the ventral part kidneys. of the pallial sinus is fused with the pal- coiled beaks more or less spiral. lial line Phuket Marine Biological Center Special publication 21(J): SSl_Egl (2OO0l 557

conical shaped like a cone pallial sinus. A character of the Tellini_ co4iectural involving conjecture. oidea, but conjecture scars, in the form of a two the formation of conclusions rounded marks in each from valve, may be dif_ incomplete evidence, guess. ficult to observe (illu.). corfoined joined to another organ of a dif_ ferent kind, e.g. the anterior adductor mus_ cle scar conjoined by the pallial muscle scar. Synonym of adnate. consecutiveherrnaphroditism common form of hermaphroditism in bivalves. The individual changes from male to female (protandry) or sometimes from female to male (protoCyny). Iamellar structure conspicuous clearlyvisible convergence similarity between organs or organisms due to independent evolution along similar lines, rather than a common ancestor, i.e. convergent evolution. convexity seebreath

corbiculoiddentition heterodonthinge cruciform muscle scar with three cardinals in each valve. cord round-topped moderately coarse lin_ crura columnar structures on the hinge_ ear elevation on shell surface (the term is line of Spondylidae. Similar modificatln normally used in descriptions of Gastro_ of ridges which reinforce the auricles are poda) found in coronate bearing tubercles or lamellae at Pectinidae distal part of ribs andAnom- costae having costae see ribs (costa Lat. = iidae. rib) Crura costellae like ribs but smaller see riblets. are not costellate having costellae. derived crenate edge serially notched or bearing from hinge teeth minute rounded teeth. in the larval shell (crus crenulated Lat. =leg) (iuu1. finely crural teeth see crur:a. notched or corrugated crus singular of crura. as in the edge of a crystalline shell layer see caLcite. shell1uu.). crystalline style a translucent proteina_ crest narrowridge, ceous rod Ouu.) c,srftsining carbohydrases. the top, the highest point of something Located in a style sac opening into the cross small bar calcareous stomach ftilu.). Qsmpare with protostyle. ridges across ribs. Concentric F{4 sculpture has crossed radial 111 crystalline style Macoma balthica sculpture ri11a.r. l-lJ ."os".dla-ellarlayer ":"f"'lbT' crystalline shell material appears as thin crossing plates in sections (ittu.). cruciform muscle scar situated close to ctenidia plun of . the ventral shell margin at the end of the ctenidium respiratory organ: in a general (TMMP) 558 Tlopical Marine Mollusc Programme

cyclodont teeth seem to spring from the cavity of the beaks and to be as if it were twisted into line on the cardinal margin oesophagus Qsocqrdia and certain cardiids). cylindrical shell form found in many bor- (, ing mytilids f;zzzu.).

style

way a stem carrying a nerve and blood ves- cylindrical shell fom sels from which, on each side leaflets or slender filaments are given out laterally cyrenoiddentition synonymofcorbicu- (illu.). See bipectinate, gill filaments, Ioid dentition. fi libranchiate, foliobranchiate, monopect- deciduous falling off at the end of a growth inate, protobranchiate, reticulate gill. period, structures easily shed by an ani-

the lamellibranch gill mal. decussate radial and concentric sculptures interrupt each other to form small dia- mond-shaped biocks, Le.,ornaments con- sisting of two sets of oblique ridges that cross to form X's. ALso a term referring to protoconchs of certain gastropod larvae. (decussare Lat. = to cross). ctenodont the primary taxodont hinge of demibranch g"ill with fiIaments on only one the nuculoids. See Pseudoctenodont. side, synonym of hemibranch. See inner ctenolium small comb-like teeth set on the and outer demibranch. Demibranchs can inner margin of the byssus gape in the be single (filaments forming a V, e.g. in right valve of many pectinids (ktenos Gr. Lucinidae), or double (fiIaments forming = Cornb') ftuil. a W' typical of other heterodonts). dental laminae e.g. in Placun a.See crura. denticulate with tiny teeth on the man gin. deposit-feeding the process of feeding on material deposited in the sediment. Com- pared to detritus-feeding, there is nor- mally little sorting before ingestion. depressed flattened dorso-ventrally. cultch substratum for spat. descending pallial sinus the dorsal sec- cuneate shell form resembling Donax tion of the pallial sinus is directed towards cuneetus in outline ftUu). the ventral shell margin. desmodont hinge teeth poorly developed or absent, but thin leaf-like projections (accessory ridges) below the umbo may cuneate shell lorm surround the ligament, e.g. in Myoidea. Subumbonal desmodont tuberculation is found in Cuspidariidae (desmos Gr. = band; odons Gr. = Looth) Ottu.). cuspidate sharplypointed. Phuket Marine Biological center special publication 21(J): ssl-sgl (2000) 559

sheII-shape (illu.). dissoconch is the adult stage where the final characters detritus-feeding selective feeding on de- ofthe species are posited material rich in detritus and mi- developed 1;zzu.;. discoidal shell shape croorganisms. See deposit-feeding. See larval development see direct, lecithotrophic, development. planktotrophic. distal towards digestive system ofbivalves encompasses the outer side, an anterior mouth, oesophagus, stomach, farthest from crystalline style, , intes- the centre of tine, rectum, and a posterior anus (illu.). origin or point dissoconch Perna uiridis of attachment. distorted pulled or twisted out of usual shape. divaricate sculpture oblique sculpture angled oppositely on anterior and posterior halves of the shell. intestine The angle is typicallv formed digitation finger-like projections along the median digitiform shaped like a finger or posteromedian axis (ittu.). dilation becoming wider, further open. divergent sculpture dimorphism having two forms within a pattern where radiating species, e.g. size or colour differences be- primary ribs divide tween male and female. and the divisions dimorphic derived from dimorphism. are not in a truly dimyaria group of bivalves having anterior radial orientation divergent rib pattern and posterior adductor muscles (dis Gr. = (illu.). two; myos Gr. = muscle). dorsal in a bivalve, it pertains to the um- dioecious having the sexes separate bonal part (ittD. Opposite ventral mar- throughout life. dipper ladle, scoop dorsal used for dipping. Term used in glr descriptions of shell-shape. dipper-shaped dipper-shaped shell form,e.g. inCuspida- riq. (iltu.). ventral direct development larvae complete a larger part, or the whole development in dorsal area shell area toward the umbones. brood chambers, or within egg masses, The hinge line is always dorsal. short-cutting a pelagic phase. dorsal hood area resembling a hood in the discoid (alsodiscoidal) stomach wall, facing the head of the crys- shaped like a disk. Used in descriptions of talline sLyle ftttu.). Tlopical Marine Mollusc Programme (TMMP) 560

\r\ \\ \ti elliptical she1l form domcuwed embryonic shell part of shell formed be- fore hatching. Macomabalthica emphatic sharp or clear in form. downcurved concentric sculpture, or ele- endemic distribution restricted to a cer- ments on rib surfaces pointing toward the tain geographical area. shell marginftltu). endobyssate infaunal attachmentwithin D-shape larva early substratum using a mesh of byssal larval stage, usually threads. rounded or slightly endolithic living within rock. pointed at the endosymbiont living within another or- umbonal end, having prcdissoconch I ganism, usually in a type of association Perna uiridis a straight, rather long that is mutually beneficial. hinge-line (iltu). See larval development. ensiform shell form having an duplivincular li gament outline a series of lamellar as found and usually in oblique bands chev_rons Ensis ensiform on the cardinal (illu.). area typical of entire paltial line = complete; without arcids and gly- indented margin. cymerids epibenthic derived from epibenthos (duplus Lat. = epibenthos fauna living close to the bot- double; vinculum tom. Lq.t. =band) rtuu.). epibyssate bivalves that attach to the sur- dwarf male a small, usually simply formed face ofhard substrata by a byssus. male, either free living or carried by the epidermis = periostracum. female. epifauna bottom fauna living on surfaces dysodont teeth absent, of the bottom, eelgrass, and rocks. or ill defined (denticles) epithelial adj. derived from epithelium. situated either side of epithelium sheet of cells tightly bound to- the ligament, charac- gether, Iining internal and external sur- teristic of mytiiids faces of multicellular organisms. (dys Gr. - poorly, equal structures of the same size. without; odons Gr. = tooth) (ittu.). equal adductors muscles ofthe same size. ecolog:ical niche the place of an organism equilateral the in an ecosystem, including all factors af- beaks are situated fecting the life of the organism. See real- centrally, l.e. shells ized niche, fundamental niche. are symmetrical edentulous hinge line without teeth. about a transverse elevated being at a higher level. Iine drawn through elliptical shell having elliptical outline the umbo. It occurs (illu.). in e.g. pectinids lequilateral Phuhet Marine Biological center special publication 21(s): si1-sg1 (2000) 561

and glycymerids, but is not a common fea- exhalant current area where exhalant (tttu.). ture among bivalves water is expelled in species without a de- equivalve the right and left valves are veloped exhalant siphon, e.g. in Cardita. alike in form and size. It is the most com- exhalant siphon carrying water and fae- mon condition among bivalves. Compare ces from the interior outwards with inequivalve. exhalant tube a temporary tube connect- erectile capable ofbeing raised or erected. ing the exhalant siphon of lucinids with escutcheon posterior part of dorsal mar- the sediment surface. The exhalant siphon gin; usually elongate, depressed, and char- is normally withdrawn, but can be ex- acterised by different sculpture compared tended through the tube. to the surroun- escutcheon exhalent siphon alternative spelling of ding radial ribs exhalant siphon. (iUD. CsmPaY. extant still in existence, living fauna. with . external ligament located on the outer side eulamellibranch of the shell. Visible from the outside when symmetrical, the shells are closed, but in some taxa they W-shaped cteni- are sunken between the dorsal margins. dial form, with connected filaments. external the recess into which Mainly found in heterodonts. the ligament is attached is outside the eulatero-frontal s)monyrn of latero-frontal hinge-pIate. cilia. extinct species havingdied out. euryhaline tolerant to a wide range of sali- extracellulardigestion principallyoccur- nities. Opposite stenohaline. ring in the stomach eurythermic tolerant to a wide range of extrude to squeeze or force out, e.g. siphons. temperatures. Opposite stenothermic. extrusive (q.dj.) pertains extrude. everted with edge turned outward. eye bivalves may carry eyes on the mantle evolution gradual development of organi- edge, e.g. pectinids, or on papillae sur- sation. Darwin's theory: higher forms of rounding the siphons, e.g. cardiids. Eyes life have gradually developed from simpler can be provided with a lens, or just be light forms (illu.). sensitive spots. Mya Zirphaea Teredo faeces undigested material voided.through anus. false lunule depressed anterior part of dorsal margin in the family Poromyidae. feeding rate see fiIter-feeding. fibrous shell material composed of fibres. filibranch the fiIamentous gill nominally Mgw comprises two series of filaments which Modified fromYonge & Thompson 1976 may be straight, but usually descend some excretory system comprises heart, pericar- distance and then are reflected upward dial coelom, and a pair of tubes leading externally. Filaments of this giII type are from the renopericardial apertures to the attached to adjacent ones by interlocking suprabranchial chamber. Kidney, nephrid- cilia in patches or upon the distal ends of ium and coelomoduct are synonyms. the fiIaments, e.g. Anomia, Arca (f|tum exhalant chamber in septibranch bivalves Lcfi. = thread; bragchion 51L = gill). the gills are modified to form septa divid- filibranchiate pertainstofilibranch ing the mantle cavity into separate inha- filter-feeding rate is determined by the lant and exhalant chambers. rate of water pumping, efficiency of parti- Marine Mollusc Programme (TMMP) 562 Tlopical

cle retention, and concentration of food movements are regulated by pedal mus- particles in ambient water. culature, and circular, obiique, and longi- fimbriated regularly gathered into wrin- tudinal musculature. The foot may be ab- kles (puckered) at the margin. sent (Ostre(r), angularly benL (Cardiidae), fissure a deep groove or furrow dividing arcuate, expanded (Macoma, Tfigonia, the umbo. Lepton, Cellocardia, Galeommo), byssi- fissured derived from fissure. ferous, clavate (Lucina), compressed, coni- fluted scale with a rounded shallow con- cal, degenerate, deeply-grooved, disk- cave groove in the side Ottu). See imbricate. shaped, digitiform (Mytilus), flat (Nucula, Yol di a), furrowed, geniculate (C q.r diidae'), grooved (many bivalve genera), hood-like, keeled, phalliform (Poromy a, Verticordia), slender, subcylindrical. The toe ofthe foot always points in the anterior direction (iltd. T}r'e form of the foot is of little serv- fluted scales and margin ice for higher systematic classifrcation, but useful at lower levels. fluted shell margin with large rounded incisions (illu.). foliaceous concentric effi@ sculpture developed digging into the sediment into more or less vertical lamellae foot protractor muscles of the foot at- foliaceous sculpture (illu.). tached to the shell. The protractor draws foliatedcalcitelayer see calcite. the foot out ofthe shell. foliobranchiate possessing leaf-like gills foot retractor muscles of the foot attached (folium Lat. = leaf; bragchion Gr. = Crll). to the shell. Retractors may be anterior food groove demibranch's marginal groove and posterior. They draw the foot into the provided with terminal frontal cilia. The shell. grooves run anteriorly to the labial palps. free pallial sinus the ventral part of the Bivalves can control the opening and clos- pallial sinus is not fused with the pallial ing of food gtooYes (illu.). Iine. frontal cilia located at the edge of a gill filament seen in transverse section. Two tracts can be distinguished: a median tract of frontal coarse cilia and cilia a lateral tract of marginal marginai fine cilia. Frontal food groove food groove particles to food grooves open closed cilia transport the provided with terminal frontal cilia Ouu.). fulcrum supporting structure, articulation. See ligamental fulcrum. foot the bivalve foot is extended by the fundamental niche the largest niche an pumping of blood into its haemocoel. Finer organism could occupy in the absence of Phuhet Marine Biological Center Special Publication 21(3): 551-581 (2000) 563

interspecific competition. enlargement of venous blood spaces. funicular consisting of a small band or cord Literally "blood cavity" fusiform narrow cylindrical, tapering. hamrner-shaped gape distance between the valves which do shell form not meet at all points around the margin. resembling a See anterior, posterior, pedal, byssus gape hammer in gaping derived from gape. outline, a hard non-calcareous struc- e.g. MaIIeus ture in the stomachs of bivalves (ittu.). (illu.). hammer-shaped hatchet a short axe used for chopping rl\' \ wood. Used in -) a\ v:\rtsr descriptions of ;-\r, P oesophagus \ shell-shape (;llu.). hatchet-shaped gastric shield heart in the majority of taxa the heart (peri- cardium) has a median ventricle and lat- t' eral auricles Macoma bolthica which embraces geniculate sickle-shaped, e.g. the foot of the rectum. In cardiids. Anomia the genus-gloup includes all taxa at the ranks heart is not ofgenus and subgenus. enclosed in gibbose very convex or tumid, a pericardium gill see ctenidium. but lies free in the gill filaments fine lateral processes of gills pallial cavity at some distance from the which maybe plicate, reflected, reticulate, gut. See pericardium , ventricle Gttu.). or simple. height maximum dimension from dorsal globose more or less spherical to ventral margins. planktonic larva with hooklike hemibranch gill with fiIaments on only one processes for attachment to gills of or fins side, synonym of demibranch. of fish. Characteristic larva of the fresh- hepatopancreas water families, Unio and Anodonta. (glo- gland secre- chis Gr. - point, angel). ting digestive gonochoristic synonym ofdioecious. enzymes, grade a taxon consisting of independent and which lineages and based on non-homologous or is assumed plesiomorphic characters. to perform 1 granulated = granulose. a function granulose having many g:ranules, small similar to rounded knobs. t}l.eliver ftttu.). gregarious bivalves living together, grow- hermaphrodite ing in clusters. an individual with both male and female growth line surface marking indicating pe- reproductive organs. riodic change of shell growbh. Lines are not hermaphroditic derived fromhermaph- necessarily annual. rodite gyrate umbo is curved, spiralled. heterodont teeth are inclined, few in haemocoel body cavity excluding the true number, usually 2-3 cardinals and 1-2 coelom. The haemocoel is formed bv the laterals, but iaterals may be absent. Car- Marine Mollusc Programme (TMMP) 564 Tlopical

dinal teeth may be bifid. This arrangement is characteristic of the majority ofbivalves. The lucinoid type has only two cardinals in each valve (3a, 3b in the left valve) and (2, 4b in the right valve), e.g. Cardiodea, Carditoidea, Crassatelloidea. The corbicu- Ioidean type has 3 cardinal teeth in each valve (3a, 1, 3b in the right valve) and(2a, 2b, and 4b in the left valve), e.g. Corbi- culoidea, Veneroidea. It is not possible to determine the correct teeth numbers of

most bivalves because the ontogenetic ori- hinge teeth originating gin of the teeth is not known. See hinge fromseriesl&2 teeth. (heteros Gr. = tlne other, different; odons Gr. tooth) ft\\il. = ffi".,32123 all 4 series ofhinge teeth

heterodont hinges heteromyarian anterior adductors much smaller postel1or than the adductor posterior (heteros heteromyarian Gr. = diffe- anterior Hinge teeth develop from lamellae on the rent; myos adductor hinge of post-larval shells. There are usu- Gr. = muscle) Ottu.). ally 2 anterior lamellae in the right valve hinge ligament elastic substance joining and 1 anterior lamella in the left valve fit- the shell valves; usually referred to as liga- ting between them. Another lamella may ment only. be developed as a marginal rim on the left hinge-line of articulation in ' valve. The anterior lamellae give rise to constituting the axis of motion for the cardinals and anterior laterals. Posterior valves in opening and closing. lamellae may give rise to posterior hinge-margin true teeth owe their initia- laterals. The post-larval lamellae on the tion to the influence of external sculpture right valve carry odd Roman numbers (I, upon the hinge-margin. See hinge-line. III, V), and even numbers (II, IV VI) on hinge-plate the thickened part of the the ieft valve. Cardinais developing from hinge-line bearing the cardinal teeth rittu.). the post-larval lamellae carryArabic num- hinge teeth calcareous knobs and ridges bers. Lamella I forms only a single cardi- guiding movement of the valves and fit- nal (1), but lamella III may be bent to form ting into sockets on the opposite valve. two cardinals (3a, 3b). Lamellae II and IV Phuket Marine Biological Center Special Publication 21(3): SS1-S8I (2000) 565

may each form two cardinals designated terbreed although they are prevented from 2a, 2b and 4a,4b respectivelv. The full doing so by barriers. suite ofcardinal teeth are never developed. inconspicuous obscure, noteasilynoticed Dentition is considered to be a conserva- or seen tive character. Teeth are categorised ac- incubation larvae are brooded within the cording to the size, form and position valves ofthe adult. They are retained un- (illu.). See actinodont, cardinal teeth, til at Ieast the stage is crt)ra, desmodont, dysodont, heterodont, achieved (e.g.. oyster). isodont, lateral teeth, pachydont, incubatory adj. pertains to incubation. schizodont, taxodont, transverse striation. incurved curved upwards or bent back. homologue structures of similar evolution- inequilateral the beaks lie in front of or ary and developmental origin, but serving behind the midline, l.e. shells are not sym- different functions. metrical about a transverse line drawn homologous derived from homologue. through the umbo. homomyarian This is the most anterior and ff;f:iil.,ffi common condition posterior adduc- 7() D\ among biv alves ( ittu.). tormuscles of the -_>- f Compare with I .'! (homos \ *' I 't:' same size ant.rror\--'.'.- / equilateral. Gr. same; myos adductor ----l inequivalve the = homomvarian Gr. = muscl.d riuu.l. left and right shells $tih homoplasy correspondenceinmorphology are different in form inequilateral of different organisms as a result of evolu- and size (illd. Compare tionary convergence or parallel evolution. with equivalve, which is the most common hydrostatic skeleton blood serves as a condition among bivalves. hydrostatic skeleton against which mus- cles can contract. a distinctive gland found inFimbria. hypoplax elongate accessory plate along postero-ventral margin valves of some inequivalve Pholadidae. infauna bottom fauna living buried in the imbricate flattened, interrupted elements sediment. of concentric infaunal adj. derived from infauna, €.€. overlapping infaunal bivalve. imbricate sculpture inflated swollen. projected infrabranchial from the rib below the gills surface ftItu.). infrabranchial See scale. chamber immure ub. to enclose within or as within the lower walls. chamber of incised with deeply notched margin. the mantle incision a cut, gash, or notch. cavity, incipient just starting to be or happen. receiving incipient species populations that are the incurrent diverging towards the point of becoming flow of water [X*; strong different species, but which can still in- (illu.). currents 566 Tlopical Marine Mollusc Programme (TMMP)

infoabranchial space the space between recess into which the ligament is attached, gl-lls (iUu). is set on the hinge-piate. inhalant chamber in septibranch bivalves interspace the gills are modified to form septa divid- the sunken ing the mantle cavity into separate inha- area between lant and exhalant chambers. ribs. Inter- inhalant current area where inhalant spaces can Go'ouu water enters in species without a devel- be flat, nar- oped inhalant siphon, e.g. in Cardita. row, rectangular, rounded, or wide ftItu.). inhalant siphon carrying water and food interspecific between species, e.g. compe- from the exterior to the interior. Synonym tition between members of the different with branchial siphon. species for the same resource. inhalant tube a temporary mucous tube intracellulardigestion principallyoccur- connecting the anterior end of lucinids ring in the digestive diverticula (hepato- with the sediment surface. The highly ex- pancreas). tensible foot forms the tube. The inhalant intraspecific within species, e.g. competi- siphon is absent in lucinids. tion between members of the same spe- inhalent siphon alternative spelling of cies for the same resource. inhalant siphon isodont the hinge has only a few similar inner teeth, usually demibranch referred to as left and right lmer crura, placed parts ofthe demibrmch symmetrically ctenidium either side of o closer to the the ligament, outer visceral mass. demibrmch characteristic Ademibranch of placunids, isodont carries descen- plicatulids, hinge ding and ascen- and spondyiids (isos Gr. = the same;odons ding lamellae. Gr. = Looth) ftttu.). (illil. See also outer demibranch isomyariatt seehomomyarian. intercalary cells inserted between others; juvenile the younger stage of individuals in lucinids cells with microvillar borders before they have acquired adult capacity on gill filaments. of reproducing. Juvenile and adult shells intercalated synonym of intercalary. may appear very differenL. See sculptural internalcharacters importantcharacters change. on the inside of shells are cardinal and juxtaposition placed side by side or close lateral teeth, myophore, nymph, pallial together (juxta Lat. = next to). Iine, pallial sinus, ridges, muscles scars Keber's gland see pericardial glands. internal ligament located on the inner keel prominent ridge. side of the labial of the lips, i.e. surroundingthe mouth shell. Not internal labial palp always located in the anterior visible from ligament in resilifer part ofthe body. the outside See palps. when the lamella plur.lamellae \\ lamellae shells are thin plates forming closed ftttu.). concentric (comarginal) \ section of internal resilium with chondrophore the shell sculptrre (iuu.). fi?i; ntric sculpture Phuket Marine Biological center special Publication 21(J): isi-s8l (2000) 567

lamellar composed of thin plates. frontal cilia seen in transverse section. lamellate withlamellae. Synonym of eulatero- frontal Ouu.). lanceolate shaped like a lance-head; lecithotrophiclarvae have averyshort sharply pointed at one end and broad at pelagic life. They are feeding on stored the other end. yolk. larval development from a left valve When shells are oriented, the stage, the prodissoconch I develops. It is umbo should point toward the observer an embryonic formation. The hinge-Iine is and the anterior margin toward the head straight. Prodissoconch II is a larval for- of the observer. Then the observer holds mation. The hinge-Iine starts to curve. the left valve in the left hand. In species Nepioconch is a juvenile stage. It is dis- with a byssal notch this always lies in the tinguished by shell texture, shape, and anterior part, thereby giving a mark of hinge characters. Dissoconch is the adult correct the orientation in , stage where the final characters are de- pteriaceans, and malleoids. veloped. Observed from the outside, the umbo larval shell hard part of pelagic larva be- pointing away from the observer, and pos- fore it settles down and undergoes meta- terior edge pointing to the right, the left morphosis. valve is observed. With the same orienta- lateral cilia located at the side of a gill tion of umbo but observed from the inside, fiIament seen in transverse section. See and the posterior edge pointing to the left, latero-frontal cilia. the left valve is observed. The left valve lateral compression pertains to evolution carries the ligament, either the whole or of bivalves. the greater part ofit on the left hand side. Lateral The majority of shells are illustrated us- compression ing the above orientation of the umbo rela- is speculated tive to the observer, although it would be to have been more logical to orient the umbo (the dor- the first step, sal part) towards the observer and the followed by dorsal view shell margin (the ventral part) pointing formation of of shells away from the observer. a ligament length of shell maximum distance! from and a splitting of the shell along the ante- anterior to posterior margins. (See ante- rior-posteri or axis ( illu.) . rior, dorsal, posterior, right, ventral). lateral teeth number 1-2 either side ofthe lens transparent structure (multicellular cardinal in cardiids) in the eye through which light area some is focused onto the retina. distance lenticular shaped like \.-. from the a biconvex lens. Shaped /"/\,r-' cardinals Iike the seed of ,Lens t,'/1 and sub- esculentq. Used in parallel descriptions of shell- lenticuiar form to the shell margin; lateral lamella = lat- shape ftllu.). eral tooth Gttd. See hinge teeth. leucocyte colourless cells ofblood. latero-frontal cilia leukocyte alternative spellingleukocyte Iocated lateral laterofrontal cilia ligament external, tough, elastic, and to the fine nonfibrous substance (tanned glycopro- lateral tein) that joins the right and left shells laterofrontal tracts of - cil ia (illil QigamentumLat. = band; ligare = tie (TMMP) 568 Tlopical Marine Mollusc Programme

together). The ligament is a fundamental ture clearly raised above the shell surface character and universally present in (illu.). , though rudimentary in some lithodesma accessory shelly piece divid- taxa (Pholadacea). Nearly every stage of ing and reinforcing the resilium, e.g. in position of the ligament can be observed Thracict. The function is to secure ad- from truly central to posterior. See alivin- equate abductive thrust in a ligament cular, amphidetic, external, internal, (Iithos Gr. = rock; desmos Gr. = band) multi- vincular, opisthodetic, parivincular, lucinoid dentition form of heterodont and prosodetic ligament. Compare with hinge dentition with two cardinal teeth in resilium, the internal fibrous bond. each valve. lucinoid scar anterior adductor elongated as in Lucinidae. lunar see lunate (l.una Lat. = moon). lunate somewhat Lunate sculpture crescent-sh aped {tttu.). lunule anterior part of dorsal margin; of- ten heart-shaped, depressed, and charac- terised by different sculpture compared to nymph the surroun- ligamental edge a thin, more or less flex- ding ible deposit of radial ligamentary ribs escutcheon rumbo substance at (illu.). the hinder end of opisthodetic ligaments, e.g. in cardiids f;zzu.). ligamental fulcrum in thin shells, the equivalent to the nymph in, e.g. cardiids. maculated provided with rather large ligostracum thin calcareous layer that spots. binds the ligament to the shell. mamillate shaped like a breast, gently line very fine rounded papillae. radiating rib or mantle the soft tissue underlying shells of concentric molluscs. sculpture not mantle cavity divided by the ctenidia into visibly raised lower (infrabranchial) and upper (supra- ffi@radial & concentric lines above the branchial) chambers, thereby separating surface (illu.). incurrent from excurrent flows. frne linear elevation mantle fold soft tissue underlying the on shell surface. shell, and enclosing the mantle cavity. At lirate bearing lirae. the marginal edge of the mantle there are liration concentricsculp- @lirations typically three folds, an outer secretory Phuhet Marine Biological Center Special Publication 21(3): 551-881 (2000) 569

fold close to the periostracum and shell, a monoecious having male and female or- middle sensory fold, and an inner muscu- gans in the same Iar fold (tttu.). individual. monomyarian outer fold having only one adductor muscle (the posterior), e.g. Tridacnidae (monos Gr. = one; mantle lobes may myos Gr. = muscle) be free all the way (illu.). round except dorsally monopectinate ctenidia bearing one row (e.9. Arcoidea, of gill lamellae. Neotrigonia) monophyly comprising an ancestor and all or fused to make its descendants. See paraphyly and poly- up to four openings. phvlv. See pallial monophyletic pertainstomonophyly. (illu.). monotype a single type which constitutes marsupium part of species or genus. gill modified pouch movements as of mantle edge monot5ryic genera having only one species; for keeping larvae species having no subspecies. before release in unionoids. morphology the form and structure of an medial situated in or towards the middle. organism. median adj.lytng or running in the axial morphospecies a group of individuals plane. which are considered to belong to the same median n. middle point, straight line join- species on grounds of morphology alone. ing the midpoints of the nonparallel sides mosaicostracum a thin calcareous layer of a trapezium. binding the periostracum to the prismatic median area the area between anterior outer shell layer in pteriomorphs. and posterior slopes. multivincularligament a series of trian- melamin black or dark brown pigment gular ligaments mesoplax elongate accessory plate across characteristic multivincular umbo in some Pholadidae. of isognomonids. metamorphosis larvae change to This ligament juvenile stage. The velar lobes disappear is a reduplication and adult organs and shell structure de- of the alivincular velop. type (multi metaplax elongate accessory plate cover- Lat. = many; ing postero-dorsal gap between valves in vinculum some Pholadidae. Lat. =band) 6ttu.). microstructure see shell microstructure. muricate spiny. mobile fauna capable of moving (mobilis muscular septum separating the anal and Lat. = easy to branchial chambers. move). myophore calcareous process where mus- modioliforrn cles are attached, e.g. pedal protractors shell shape and anterior adductor muscles. See pho- like in ladmyophore. (myos Gr. = muscle; pherein Modiolus 1llu.), Gr. * modiollform =to carry Lat. fero). (TMMP) 570 TVopical Marine Mollusc Programme myostracum neritic living in coastal waters. shell material nervous system simple with fused cerebral secreted in the and pleural ganglia, visceral, and pedal areas for musc- ganglia. le attachment. niche see ecological niche. mytiliform nodose with small protuberances. m1'tiliform shell shape non-symbiotic absence of symbiosis, e.g. like in Mytilus (ittu.). bacteriocytes mother of . Always made of absent. aragonite, and deposited as either polygo- nuculiforrn nal or round tablets growing upon an or- shell shape ganic matrix. Nacre may grow as sheet like in nacre, Nucula. organrc columnar mattel' nymph nacre, or calcareous row stack support of nacre. the ligament Nacre is on the hinge nacl'e typical of Iine (ittu.). palaeotaxo- obconical donts, but occurs in other Laxa, e.g. pearl bluntly conical. oysters (illu.). oblique nacreous shell material consisting of, or asymmetrical, having the lustre of nacre. diagonal nacreous shell layer composed of arago- oblique sculpture nitic crystals formed in a vertically and oblique to the oblique sculpture horizontally deposited organic matrix. shell margin. neoteny synonym of paedomorphosis. (illu.). nephridia two symmetrically situated or- oblong gans, lateral to the pericardium, with having an which they communicate by ciliated ca- elongated, nals. Externally they open near and be- subrectan- hind the genital openings. gular oblong shell form nephroliths sphaericalconcretions, mainly shape 1tttu.1. calcium phosphate, in some cells of the obovate egg-shaped with narrower end kidney. downward. nephroproct opening from the kidney. oesophagus first part of the digestive sys- nepioconch an tem connecting pharynx to stomach. early-formed part ontogenetic derivedfromontogeny. ofthe dissoconch, ontogeny history of development and separated from growth of an individual. the later part by ontogenesis =ontogeny. a discontinuity. opisthodetic ligament extendingbehind See larval umbo, e.g. in Tellina andVenus (opisthen development (illu.). Gr. = behind; daetos Gr. = tied together). nepionic stage stationary stage of glochi- opisthogyrous beaks point in the poste- dia, which become encysted on the fins or rior direction (opisthen Gr. = behind;gyros gills of frshes (nepa Gr. = scorpion). Gr. = circle). Phuket Marine Biological Center Special Publication 21(S): ES1-581 (2000) 577 opisthogyrate derivedfiom opisthog5rrous. phons are retracted in teredinids. High opisthopodium accessoryfin-like organ diagnostic value. developed at the posterior end ofthe vis- pallial relating to the mantle. ceral mass (Pholadomya, Halicard,ia). pallial aperture the mantle edges may be oral of the mouth, belonging to the mouth free all the way round except dorsally (one or on the same side as the mouth. opening), two openings exist in species orbicular subspherical shape. with a developed the exhalant siphon, ornament relief pattern on surface of shell three openings ifboth exhalant and inha- (see sculpture). lant siphons are developed, four openings orthogyrous erect beaks, face each other if there is a pallial aperture between the across the dorsal margin. inhalant siphon orthog;rrate derived from orthog5n'ous (or- and the thos Gr. = straight; gyros Gr. = circle). pedal bivalves have paired osphra- gape (e.9. in dia, chemical sense organs associated with Solenoidea, visceral ganglia, near the ctenidia. Mactroidea, ossicle synonymous with ossiculum. and some ossiculum synonymous with lithodesma. Anomalo- ostracum calcifiedlayers ofthe shell. desmata). ostreiform shell shape like in Ostree. pallialline orientation shells display lateral symme- linear scar try. See anterior, dorsal, Ieft, posterior, indicating former attachment of muscles right, ventral. keeping the mantle in position along the outer demibranch left and right parts of inner shell margin (iud. See pallial sinus. the ctenidium closer to the mantle. A pallial retractors pertains to muscles demibranch has descending and ascend- along the pallial line. At the base of the ing lamellae. See also inner demibranch. siphons they become siphonal retractors. outline shell form of bivalves is ofben com- pallial sinus curved scar along the poste- pared with the outline of well known bi- rior pallial valves: ensiform (Ensis), modioliform line indicat- (Modiolus), mytiliform (Mytilus), nuculi- ing attach- form (Nuculo), ostreiform (Ostreo), pecti- ment of niform (Pecten), pectunculoi d (Glycyme- muscles rls), pteriform (Pterineo), soleniform connected (Solen), submodioliform (Modiolus). See to the siph- also shell shape. ons. A pal- ovate shaped like an Iial sinus els (illu.). may be shal- pachydont 1-3 thick, low or extend right peg-like, unsymme- up to the anterior adductor scar (iilu.). trical teeth fitting palps two ciliated appendages close ovate shell form to the into deep sockets on mouth. Palps may be free, united laterally the opposite valve, seen in extinct hippu- above, degenerate, or obsolete (paIpoLat. ritid bivalves (pachys Gr. = thick; odons = to touch gently). Gr. = tooth). palp proboscis process on each labial palp paedomorphosis see pedomorphosis. used for feeding on surface detritus in pallets paired calcareous periostracal protobranchs. structures that close the burrow when si- papilla small tapered or rounded epider- 572 Tlopical Marine Mollusc Programme (TMMP)

mal structure. plu. papillae. pedigree a diagram showing the ancestral papilliform like a papilla in shape. history ofa group ofrelated individuals. paraphyly pertains to a group including pediveliger veliger stage with the foot de- the ancestor but not all ofits descendants. veloped for feeding and locomotion, the See monophyly and polyphyly. velum is lost, and the larva is ready to set- parivincularligament alwaysposterior tIe. (opisthodetic), parivincular ligament pedomorphic adj. pedomorphosis. Alter- t^ strongly arched ,G:S\ native spelling paedomorphic. and protruding zq(\ -D\ pedomoryhosis retentionofjuveniletraits above the shell /(\ in adults. Synonym paedomorphosis, neo- margins ftUu.). t ) )) teny. Typical of cardiids, \-'--1-l pedunculate with a stalk (peduncle). TeIIina and Psam- pericardiac derivedfrom pericardium. mobiq (paries Lof. = walll vinculum Lof. pericardial derived frompericardium. = band). pericardial glands occur as lappets either paucicostate sparselyribbed. on the auricles ofthe heart or as pouches pectibranch synonym of bipectinate. on the pericardial wall itself, either inside pectiniform shell shape llke inPecten. or outside the pericardial space. pectunculoid shell shape like in Glycy- pericardium membrane surroundingthe meris. heart, or the cavity delimited by this mem- pedal ofthe foot or feet. brane. The pericardium of bivalves en- pedal elevator scar showing former at- closes two lateral auricles attached to a tachment of muscles by which the foot is median ventricle. The rectum may be dor- lifted. Elevator muscles are attached to the sal to the ventricle or the ventricle may be inner shell surface under the umbo. traversed by the rectum, the common con- pedal elevator posterior pedal elevators dition. are found in,e.g. Protobranchia, Trigonio- peripheral adductors distant from the idea, and Arcoidea. centre, close to the periphery ofthe shell. pedal feeding the foot is used in collection peripheral scar distant from the centre offood particles. Pedal feeding habit is a close to the periphery ofthe shell. universal feature of juvenile bivalves. periostracum quinone-tanned proteinace- pedal gape anterovental gape for the ex- ous outer tension ofthe foot. Iayer of mol- pedal protractor scar showing former Iusc shells attachment of muscles by which the foot (illu.). is drawn out of the shell. Periostracum pedal protractor posterior protractors are may be smooth found in, e.g. Protobranchia, Trigonioidea, (homogenous), and Arcoidea. wrinkled, or projected into hairs, bristles, pedal retractor scar showing former at- or lamellae. The hairy periostracum of tachment of muscles by which the foot is mytilids is not a true part of the perio- drawn into the shell stracum. The hairs are secreted by the bys- pedalretractor s include anterior andpos- sus gland and put in position on the shell terior retractors, which may be free or in- surface by the foot. ternal to each adductor. periphery part of shell farthest from axis. pedal scars may be invisible, feeble, dis- perisiphonal surroundingthe siphon. The tinct anteriorly, or separate from and be- perisiphonal area may be smooth or pap- hind the anterior adductors. illose. Phuhet Marine Biological Center Special Publication 21(3): 551-581 (2000) 573 pholad myophore shelly process for porcellaneous alternative spelling of por- subumbonal attachment of the mantle. cellanous. The pholad myophore supports the vis- porcellanous shell materiai resembling ceral mass and the large fleshy palps in shiny porcelain. Barnea and Zirphaea. porcelanous alternative spelling of photoreceptor see eye. porcellanous. phylogeny evolutionary history and line posterior nearer the anus. If a pallial si- if descent of a species or higher taxonomic nus is present it is always in the posterior group. end of the shell. pigment red, yellow, and orange coloura- posterior adductor muscle nearer the tion is caused by porphyrin based pig- anus. ments. Purple pigment in the internal posterior gape along the posterior slope shell layers probably has a different ori- usually reflecting the presence oflarge si- gin, and is very resistant. phons. pilose hairy (illu.). posterior pedal retractor scar often a pinnate with small big scar in byssally attached heteromy- lateral branches arian bivalves. (pinnules) divided predator any organism that catches and in a feathery man- kills other organisms (prey) for food. ner. prey an animal being hunted or captured plantar of or on the by another for food. sole ofthe foot primary describing element appearing (plantaris Lat. = sole of the foot). early in ontogeny. planktotrophic larvae feeding on plank- primaryrib ton during early development, typically for radial ribs can a month or longer before metamorphosis. be complete, plesiomorphous having a similar form. bifurcate, plesiomorphy retainedprimitive charac- or split {ittu.). state shared with one or more sister prismatic primary ribs ter complete & split taxa. shell material pleura membrane lining thoracic cavity composed of prisms. and extending to cover surface of respira- prismatic layer outer calcified layer of the tory organs. shell ott"). Various prismatic layer pleural adj. pertains to pleura as pleural types of prismatic ganglia. layers can be plicate densely folded like a fan; folded or discerned: ridged. simple, fibrous, plicate gills ctenidia folded like afan, e.g. composite, in oysters and cardiids. and spherulitic podocyte epithelial cell of kidney having layers. numerous processes which rest on the prodissoconch the basement membrane. embryonic shell corresponding to the polyphyly group comprising two or more taxa derived from distinct lineages. See monophyly and paraphyly. polyspermy fertilisation involving the en- trance of several sperm into the egg, but only one sperm forms the pronucleus. (TMMP) 574 Tlopical Marine Mollusc Programme

of gastropods. Prodissoconch I proximal nearest to the centre of origin or ftllu.) is secreted by the larval shell gland, point of attachment. and prodissoconch II lttu) is secreted by pseudocardinals cardinalswithsimilar the larval mantle edge. See larval devel- function but of different developmental opment. (pro Gr. = before; dissos Gr. = dou- and evolutionary origin. ble; kogchae Gr. = concha Lat. = mollusc pseudofaeces particulate matterrejected shell). by the sorting surfaces after ingestion and prosocoelous pertains to beaks with a subsequently expelled through the inha- narrow cavity. (proso Gr. = in front; koilos lant siphon. Gr. = hollow). pseudolateral tooth lateral tooth with its prosodetic remnant of ligament extend- proximal end close to the beak. ing anterior to the beaks (proso Gr. = in pseudoctenodont designates a taxodont front; daetos Gr. = tied together). hinge ofArcoidea which is believed to be a prosogyrous beaks point in the anterior secondary development in the evolution of direction (proso Gr. = in front; gyros Gr. = this type of hinge. circle). pteriiform prosog'yrate derived from prosogyrous. shell shape protandry see consecutive hermaphrodi- Iike in tism. Pterinea (illu.). protobranch gills havingflat punctate non-reflected covered with pteriform frlaments (itlu.) fine pores or pits. (proto Gr. = punctate pallial line first; bragchion dotted, having surface coveredvith small 61. = gill). protobranch gills holes, pores, or dots. protobranchiate pertainsprotobranch. punctum plur. puncta, minute pit on shell protoconch larval shell, indicated by a scar surface. on adult shell, ofben clearly demarcated pustule small calcareous, blister-like pro- from subsequent growth. jections on ribs or shell surfaces. More di- protoryny see consecutive hermaphrodi- minutive than tubercle. tism. pustulose provided with pustules. protostyle pyriform shapedlike a pear. mucus-bound Quenstedtmuscle food string one pair of (rod) projecting small muscl- into the stomach es, probably Quenstedt from the midgut of Nuculanidae Gttu.). homologous muscle scar protractor see footprotractor. with ante- protractor scar on the inner shell surface rior pedal indicating attachment of muscles bywhich muscles the foot is drawn out of the shell. The pro- (illu.). tractor is associated with the anterior ad- rachis ductor muscle (proLat. = forward; trahere central Lat. = to pull). stalk or axis, provinculum in Pectinoidea a vertically e.g. of gill. striated area on each side ofthe resilifer. radialsculpture provinculum in bivalve larvae the central ribs growing out like rays from the umbo. area of the hinge. See lines, threads, riblets, ribs. Phuhet Marine Biological Center Special Publication 21(3): 551-58-l (2000) 575 ramose branched. resiliophore s)monymous with resilifer. ray line of shelly material extending from See chondrophore. some point. resilium usually describing the internal realized niche the actual place and role bond while the external bond is termed an organism occupies in an ecosystem. See Iigament. Occasionally used to describe fundamental niche. the recess into which the ligament is at- rectangular tached = resilifer. outline of shell resorption removal of once-formed shell has the shape by action of the living mollusc. of a rectangle reticulate network of intersecting radial (iIIu.). rectangular shell form and concentric sculpture. rectangular rib reticulate gill successive frlaments are profile connected by vascular branches or connec- ribs are tive tissue forming a reticulate gill, e.g. rectangular Cardiids, Mactra. in cross-secLion ( illu.). retina the inner light-sensitive layer of the rectum the posterior part of the alimen- eye. tary canal leading to the an:us (iIIu.). retractors see foot retractor, byssus retrac- recurved concentric sculpture or elements tor. on rib surfaces pointing toward the umbo retractor scar on the inner shell surface (illu.). indicating attachment of muscles used to \{\ draw the foot anterior posterlor into the shell. retractor retractor \r\{ Pedal retrac- recur-ved are loca- sculpture tors ted near the anterior and/ or posterior adductor mus- reflected turned or folded back on itself. cles Gttu.) (re Lat. reflected gill filament is folded back on = back again; trahere Lat. = to pull). itself. rheotaxis locomotory response to the renal ducts from the kidneys into the su- stimulus of a water current. prabranchial chamber. rhomboidal shell renopericardial ducts fromthekidneys outline resembles into the pericardium. the shape of a reproduction bivalves are generally rhombus (dia- dioecious, although many are hermaphro- mond-shaped) dites and some are protandrous. See also (illu.). gonochoristic, consecutive hermaphro- rib in the simplest dites, simultaneous hermaphrodites, or form radial ribs protandric hermaphroditism. consists of equally resilialbuttress the chondrophoremaybe sized elements supported by a calcareous ridge extend- separated by inter- ing from the umbonal cavity. spaces. Primary ribs can be entire, bifur- resilifer smaller hollowed out depression cating, or fully split. In cross section they in the hinge-plate. Wher-r larger and spoon- can be acute, over-hanging, rectangular, shaped it is termed chondrophore. rounded, round topped, skewed, or tabu- (TMMP) 576 Tlopical Marine Mollusc Programme

Iate (iltu.). Smaller ribs are referred to as pertains to rostrum riblets, threads, or lines. (illu.). riblet term used to describe smaller ribs rostrum the posteri- on the shell surface. Often thicker ribs (pri- or end of bivalves is mary ribs) occur together with smaller prolonged, beak-like riblets, and even smaller threads. Riblets process. can be entire or just emerg1ng (illu.). rugose with highly irregular surface; many wrinkles or ridges (ruga = fold or wrinkle) scales roof tile-shaped bars or hood-Iike structures across ribs. Concentric ffi@w sculpture rib sculpture the surface of ribs may carry has crossed scales cross bars, pustules, scales, spines, or tu- radial bercles. sculpture ridge prominent concentric sculpture, or (illD. See fluted, imbricate. Iow walls of calcareous material, or thick- scar mark left on shell indicating former ened periostracum running over the um- attachment of muscles. bones to the schizodont a triangular cardinal tooth is ventral margin. split in Anterior, but two parts most commonly as seen in posterior shell Trigoni- surfaces may be rounded oidea. The demarcated by schizodont ridges. Seen in cross-section, concentrtc arrangement ridges may be downcurved, foliaceous, la- is now considered a variation of the het- mellar, recurved, or rounded Gttu.). erodont hinge {tttu.) (schizein Gr. = to split; right valve seen from the outside, the odons Gn = tooth). umbo pointing away from the observer, scissulate sculpture and posterior edge pointing to the left, the concentric lines run at right valve is observed. With the same ori- different angles on the entation of umbo, but looked at from the anterior and posterior inside, and the posterior edge pointing to parts ofthe surface scissulate the right, the right valve is observed. The respectively (illa). right valve has the ligament, either the sculpture (= ornamentation) ridges in re- whole or the greater part of the ligament liefon shell surface. See concentric, radial, on the right hand side. The majority of oblique, acentric sculpture. shells are illustrated using the above ori- sculptural change in some species the entation of the umbo relative to the ob- umbonal region can be differently sculp- server. (See anterior, dorsal, left, posterior, tured from the rest of the shell, l.e. iuve- ventral). nile and adult shells may appear very dif- rounded pallial sinus the anterior sec- ferent. tion of the paIIiaI sinus is rounded yield- scutes large scales onribs ofTlidacna spe- ing an oval sinus. cies. roundedribprofile see rib. secondary describingelement appearing rostrate ad,i.beaked iater than the earliest one in ontogeny. Phuket Marine Biological Center Special Publication 21(3): 551-581 (2000) 577 secondaryriblet smaller inhalant, exhalant, completely or partially ribs between primary ribs fused, separated, or absent. Exhalant and are called secondary riblets. inhalant siphons are usually located close SmaIIer ribs between together in the posterior end, but devia- secondary rjblets are tions occur, e.g. in galeommatid genera called tertiary fibIets 1ttu.). where the inhalant siphon is anterior and sedentary see sessile the exhalant posterior. septibranchia small gills transformed into siphonal retractors muscles at the base a transverse muscular pumping partition of the siphons. See pallial sinus, pallial (septum Lqt.= fence; bragchion 6t'. = gill). retractors. septum transverse structure separating siphonal septum in some siphonate taxa things, closing off, see siphonal septum. a septum (partition) extends forward prac- serrate shellmargin tically separating the mantle cavity into saw-toothed margin an anal and a branchial chamber. (illu.). shelly adj. derived from shell. sessile non mobile skewed ribs where fauna, free living or the slope of one attached. Sedentary side is steeper than skewed ribs has the same meaning. (sessilis Lof. - pos- the other side Gttu.). sible to sit on) slope shell area at an angle to the central shell layers shells may be nacreous, part ofthe shell and characterised by dif- subnacreous, prismatic, cellulo-crystal- ferent sculpture on radial ribs. Slopes may Iine, porcellanous, fibrous, tubuliferous. be anterior, or most commonly posterior. shell material shells are composed of smooth shellmargin aragonite, calcite, and nacre in various no resistance if, e.g. proportions. touched by a finger shell microstructure mineral and organic (illu.). composition of the layers of bivalve shells. socket groove accom- See nacre, prismatic layers. modating a tooth on smooth she1l margin shell outline see outline. the opposite valve. shell shape shells may be alate (winged), soleniform elongated shell shape like in auriculate, bialate (double-winged), cylin- Solen. drical, dipper-shaped, discoid, finger- solitary bivalves living alone, not growing shaped, hammer-shaped, hatchet-shaped, in clusters. lenticular, globular, oval, rectangular, sortingarea rhomboidal, spathulate, subauriculate, ciliated area in subquadrate, subrectangrlar, triangular, stomach of bi- truncate, trapezoidal, tubular. See also valves where outline. ingested partic- stomach ofprotobranch simple pallial line = complete pallial iine. les are sorted simultaneoushermaphroditism func- according to size and density (illu.). tion of male and female sex organs in the spat a newly settled bivalve, such bivalve same individual. Compare consecutive larvae collectively. hermaphroditism. spatfall the settling and attachment of sinuated pallial line having a wavy in- pediveliger larvae. dented margin. spathulate spathe-shaped, a leaf envelop- siphon funnel-shaped structure from the ing the of the flower wild arum mantle cavity to exterior. Siphons may be (spatheGr.=ablade). 578 Tlopical Marine Mollusc Programme (TMMP) spatulate shaped like a spatula, a utensil subcentraladductor nearlycentral. with a broad flat blade, spoon-shape d.Ott".). subcentral scar nearly in a central posi- tion. subdentate slightlytoothed. subequal adductors nearly of the same size. subexternal ligament external but tend- ing to be in an internal position. subinternal ligament internal but tend- ing to be in an external position. subinternal resilium descends into the spherulitic layer prismatic shell Iayer hinge-plate and becomes more or less in- composed of rounded units. ternal. spine pointed, submarginal below the margin. thornlike submytiliform shell shape nearly like in protuberance Mytilus. on rib surfaces. subnacreous Can be derived shell material ( )'t/::'/t/ttht'l from a scale oltu.). resembling spinose provided with spines. nacre. squamose with scales. subovate paired, innervated, ciliated, somewhat spherical organs of balance; may hold a egg-shaped subovate shell form statolith. (illu.) statolith calcareous concretion in the sta- subquadrate somewhat square. tocyst. subrectangular somewhat rectangular. stenohaline tolerant only to a narrow subtrigonal form close to triangular. range of salinities. Opposite euryhaline. subulate slender and tapering to a point. stenothermic tolerant only to a narrow subumbonal placed under the umbo. range of temperatures. Opposite sulcated grooved or furrowed. eurythermic. sulcus radial depression or groove in the straight pallial sinus the anterior section anterior, median or posterior areas. of the pallial sinus is straight yielding a super prefix in classification signifying a rectangular sinus. taxon above, e.g. family - superfamily. stria plur. striaq very narrowly incised supra prefix meaning situated above. shallow groove, see transverse striation. suprabranchial chamber the upper striate marked with fine grooves. chamber of the mantle cavity, receiving the style see crystalline style. excurrent flow ofwater. style sac contains crystalline style or symbiont organism living in symbiosis. protostyle. symbiosis close and usually obligatory as- sub prefix meaning under, below, nearly, or sociation oftwo different species. See zoo- not quite. xanthellae, bacteriocyte. subapical below the tip. symplesiomorphy aprimitive character subauricular below the ear. state shared by two or more taxa. subauriculate somewhatauriculate. synapomorphy derived charactershared subcircular somewhat circular. by two or more sister taxa. subequal structures of nearly the same synonym name of a taxon which is identi- size. cal with another taxon. Phuket Marine Biological Center Special Publication 21(3): 551-587 (2000) 579

synonJflnous often followed by ruith,being of the mantle between the teeth. Striations a synonym. are always in the line of motion and par- synonymy the character of being synony- allel to it. mous, a list of synonyms. trapezoidal tabulate ribs with shaped nearly a flat surface and like a trapezium sloping sid.es (illu.). (illu.). trapezoidal tactile papillae serving the sense of touch. trapeziforrn taxa plur. oftaxon. shaped like a trapezium; rectangular in taxodont many teeth of same form and form having two of its sides parallel. similar size trigonal triangular situated in a outline Gttu.). row along the trochophore dorsal margin, free-swimming larval symmetrical stage. It has a ring of around the umbo, cilia around the rim trigonal characteristic of nuculids, arcids, and and a terminal tuft of limopsids (taxis Gr. = arranged in order; cilia in front of the mouth (trochos Gr. = odons Gr. = tooth) ottu.). ring; phorein Gr. = to carry). taxon plur. taxa, any defined unit (e.9. spe- trophic connected with food and feeding. cies, genus family) in the classification of trophic level a division of organisms based organisms. on the method of obtaining food. Four lev- tentacle elongate structure, usually with els are generally sensory function. identified: primary tertiary riblet see secondary riblet. producer, primary -, Tethyan affinity to fauna of the Tethys secondary -, and Sea that lay between the two ancient tertiary consumers. supercontinents, Laurasia and Gondwa- truncate terminating naland (Predecessor of the today's Medi- abruptly as if the end was cut off Gttu). terranean). tubercle thickness applies to shell layers in single small rounded knob shells. on afib Gttu.). thread fine radiating tuberculose havingmany riblets slightly raised tubercles 1ltu.). above the shell tubular having surface ftllu.) the form of a tube tooth projection found (illu.). on the hinge line. See tubuliferous shell hinge teeth, cardinal, Iateral. material transverse perpendicular to the long axis. having transverse ligament posterior extended smaII ligament which remains between the tubes. valves and typical of mybilids and pinnids tumidity see breath of shell. transverse striation an additional pro- twisting asymmetrical twisting of the tection against irregularityin opening and valves. It is supposed to assist in obtain- closing the valves, e.g. inMactra, Spisula, ing rigidity bringing about an exact clo- TYigonia, Unlo. Possibly a result of trans- sure of shells, e.g. in Tlisidos tortuosa. verse friction acting on the proliferations typhlosole median longitudinal fold of the (TMMP) 580 Tlopical Marine Mollusc Programme

intestine projecting into the lumen of the gut. umbo plur. umbones, older part of a mol- Iusc shell containing the larval shell (ittd. (See verrucose warty surface, sma1l wart-Iike apex, beak, projections. opisthogyros, vinculum part of term describing ligament orthogyros, such as parivincular (vinculum Lat. = and prosogyrous). band). umbonal fissure a non-accidental fracture viscera (plur.) internal organs collectively. across the umbonal region present in visceral od7. derivedfromviscera; visceral Laternula and Periploma. MASS. umbonal foacture disproportionate stress wing more or less flattened expansion. created zooxanthellae microalgae capable of pho- by the tosynthesis in the siphons and mantle tis- adductors sue, e.g. Tridacnidae and the cardiid Cor- may cause culum cardissa. an umbo- nal fracture behind the line of the chondrophores, e.g. in Thracia. Chon- chiolin is deposited along the fracture (illu.). umbonal ridge extending from the beaks toward the basal margin. umbones plur.,umbo. vacuolation containing vacuoles. Term used about periostracum. valvular siphonal membrane a valve at the base of the inhalant siphon, e.g. in the mytilid Botula. varicose bearing a or varices. varix elevation, more prominent than costa and generally spaced more widely. Evi- dence ofgrowth halt in certain gastropods. veliger larval stage developing from ,velurr. trochophore. Velum developed. Lat. - sail; gerereLat. = to carry). velum wing-like, ciliated flaps used by lar- vae for swimming; planktonic larvae also capture of food particles. ventral the shell margin, opposite the hinge, is ventral. In species with a byssal notch this is always in anterior or anteroventral position. ventricle contractile chamber of the heart (illu.) Phuhet Marine Biological Center Special Publication 21(3): 551-581 (2000) 581

REFERENCES Feeding: Hydrodynamics, Bioenergetics, Beesley, P.L., Ross, G.J.B. & Wells, A. (eds.). Physiology and Ecology. Olsen & Olsen, 1998. : The Southern Synthesis. Denmark. 140 pp. Fauna ofAustraliaVolume 5. CSIRO Pub- Kristensen, J. Hylleberg. L972. Structure lishing, Melbourne. Part A viii, 563 pp. and function of crystalline styles of bi- Collins Shorter English Dictionary. 1993. valves. - Ophelia 10: 91-108 Harper Collins Publishers. Latest reprint Longman Dictionary of Contemporary Eng- 1994. 1392 pp. Iish. New Edition. 1987. Longman. 1229 DaIl, W. H. 1895. Contributions to the Terti- pp. ary fauna of Florida, with especial refer- Nielsen, C. 1986. Fauna associated with the ence to the Miocene Silex-beds of Tampa coral Porites from Phuket Thailand (Part and the Pliocene beds of Caloosahatchie 1): bivalves with description of a new spe- River. Part III. A new classification. - cies og Gastro-chaena.- Phttket Marine Transactions of the Wagner Free Institu- Biological Center Res. Bull. 42:7-24. tion of Sciences Philadelphia, Part III: p. Ockelmann, K. 1995. Ontogenetic characters 482-570. of Mytilaceans. Phuket Marine Biological Henderson's Dictionary of Biological Terms. Center Special Publication 15: 85-88. 1989. Longman Group UK Limited. 637 Oliver, P. G. 1992. Bivalved Seashells of the pp. Red Sea. Verlag Christa Hemmen, Hylleberg, J. 1978. Data og termer- Wiesbaden and National Museum of Biologiske Studier No. 4. Akademisk Wales, Cardiff. 330 pp. with 46 plates. Forlag, Kobenhavn. 100 pp (In Danish). OxfordAdvanced Dictionary of Current Eng- Hylleberg, J. 1994. Indo-Pacific cockles Iish. 1988. Oxford University Press. 1041 (Bivalvia:Cardiidae). Part 1. Generic di- pp. agnoses and an overview of species with ZiegIer, H. E. & E. Bresslau. 1927. mention of taxonomic problems encoun- Zoologisches Wdrterbuch. Verlag von tered in Thailand. - Phuket marine bio- Gustav Fischer, Jena. 784 pp. logical Center Special Publication 13: 113- 1 36. I have modified and redrawn illustrations Jgrgensen, C. Barker, 1990. Bivalve Filter from the above references.