FAU Institutional Repository

http://purl.fcla.edu/fau/fauir

This paper was submitted by the faculty of FAU’s Harbor Branch Oceanographic Institute.

Notice: © 1992 Institute of Malacology. This manuscript is an author version with the final publication available and may be cited as: Mikkelsen, P. M., & Bieler, R. (1992). Biology and comparative anatomy of three new species of commensal galeommatidae, with a possible case of mating behavior in bivalves. Malacologia, 34(1-2), 1-24.

··)·. / '{ \)' ,,,. MALACOLOGIA, 1992, 34(1-2): 1-24

BIOLOGY AND COMPARATIVE ANATOMY OF THREE NEW SPECIES OF COMMENSAL GALEOMMATIDAE, WITH A POSSIBLE CASE OF MATING BEHAVIOR IN BIVALVES

Paula M. Mikkelsen 1 & Rudiger Bieler2

ABSTRACT

Three new galeommatid bivalves, Divariscintilla octotentaculata, D. luteocrinita, and D. cordi­ formis, are described as commensals occupying the burrows of the mantis shrimp Lysiosquilla scabricauda from central eastern Florida. Morphological comparisons are made with all other known members of the genus, comprising two previously described species from the same burrow system (D. yoyo, D. troglodytes) and the type species, D. maoria, from New Zealand. Key characters defining this genus (hinge morphology, flower-like organs, "hanging foot" struc­ ture) are discussed, especially with regard to their presence in other galeommatoidean genera. Intraspecific interaction resembling mating behavior is noted and discussed as one of the few possible examples in the Bivalvia. Key words: Divariscintilla, Galeommatoidea, Bivalvia, systematics, anatomy, mating behavior, commensalism, Stomatopoda.

INTRODUCTION MATERIAL AND METHODS Investigation of the organisms associated Lysiosquilla burrows in shallow-water sand with the sand-burrowing mantis shrimp flats at several locations on the central eastern Lysiosquilla scabricauda (Lamarck, 1818) Florida coast were sampled using a stainless (Crustacea: Stomatopoda: Lysiosquillidae) in steel bait pump ("yabby pump") and sieves of shallow waters of eastern Florida has re­ 1-2 mm mesh. Sampling depths during ex­ vealed a community of seven molluscan spe­ treme low water ranged from less than 0.5 m cies that appear highly dependent on this to supratidal, when the water level lay several specialized habitat. Remarkably, all of these centimeters below the level of the sand. species were found to be either poorly known Living clams were maintained in finger or undescribed. Accounts of the two species bowls of seawater at ambient laboratory con­ of vitrinellid gastropods-Cyclostremiscus ditions (22-25°C), with variable lighting. Water beauii (Fischer, 1857) and Circulus texanus was changed every 1-2 days, and an irregu­ (Moore, 1965); Bieler & Mikkelsen, 1988- larly-supplied, unmeasured diet of mixed uni­ and two of the five species of bivalves-Di­ cellular algae (e.g., lsochrysis, Chlorella, variscintilla yoyo Mikkelsen & Bieler, 1989, Chaetoceras) was provided. Behavioral stud­ and D. troglodytes Mikkelsen & Bieler, ies were aided by video recordings taken of 1989-have appeared elsewhere. This re­ the living animals in aquaria using a standard port deals with the remaining three species of commercial 1/2-inch-format video camera galeommatoidean bivalves. Although superfi­ equipped with a macro lens. cially different from the two species previously Transfer of specimens between laboratory described, and preliminarily treated as mem­ bowls was best accomplished using small bers of another genus (as Scintilla spp.; Mik­ spoons. The spoon could be applied against kelsen & Bieler, 1989: 192; Eckelbarger et al., the glass from below the specimen to gently 1990), detailed study has revealed their break the byssus threads while also cradling proper placement in Divariscintil/a, and has the clam. Handling these kinds of animals shown them to be in fact more similar to the with forceps is awkward and frequently New Zealand type species, D. maoria Powell, causes damage to fragile shells and tissue. 1932, than were the two species previously Relaxation prior to dissection or preserva­ described from Florida stomatopod burrows. tion was most effectively accomplished with 'Harbor Branch Oceanographic Museum, Harbor Branch Oceanographic Institution, 5600 Old Dixie Highway, Ft. Pierce, Florida 34946 U.S.A., and Department of Biological Sciences, Florida Institute of Technology, Melbourne, Florida 32901 U.S.A. 2 Department of Zoology, Field Museum of Natural History, Roosevelt Road at Lake Shore Drive, Chicago, Illinois 60605 U.S.A. 2 MIKKELSEN & BIELER crystalline magnesium sulfate, added directly *USNM- National Museum of Natural to the finger-bowl water in unquantified small History, Smithsonian Institution, amounts. Methylene-blue/basic-fuchsin and Washington, D. C. neutral red were used to delineate tissues and organs in gross dissections. For histological serial sections, animals TAXONOMIC DESCRIPTIONS were fixed in 5% buffered formalin (Humason, Family GALEOMMATIDAE Gray, 1840 1962: 14). Shells were decalcified using either Genus Divariscintilla Powell, 1932 dilute (approximately 0.5%) hydrochloric acid (complete decalcification within minutes) or a Type species: Divariscintilla maoria Powell, 1% solution of ethylenediamene tetraacetic 1932: 66; by original designation. Recent, acid (EDTA, adjusted to pH 7.2; decalcification New Zealand. complete in 5-6 days). Specimens were em­ Remarks: Redescribed by Mikkelsen & bedded in paraplast, sectioned at 8 J.Lm and Bieler (1989: 193). See remarks concerning stained with Gomori's green trichrome (mod­ generic placement under Discussion. ified from Vacca, 1985). Staining reactions de­ scribed in the text refer to this method. Colors Divariscintilla octotentaculata n. sp. referred to in the text are supplied for future (Figs. 1, 4, 7-13, 23, 33) use, that is, to infer homologies of the various glands. Photomicrographs of sections were Material examined taken with an Olympus BH-2 stereomicro­ scope fitted with an Olympus OM-2 camera Holotype: 5.3 mm [shell length], FMNH with Kodak Panatomic-X (ASA 32) film. 223401. Paratypes (31 ): 4.2, 4.2 mm, FMNH For scanning electron microscopy (SEM), 223402; 3.2, 3.2, 3.2, 3.3, 3.3, 3.6, 3.8 mm, preserved specimens were passed through HBOM 064:01866; 4.2, 4.2, 3.6, 2.9 mm (pre­ an ethanol-to-acetone series and critical-point served soft-bodies + shells coated for SEM), dried. These and air-dried shells were coated HBOM 064:01867; 3.9, 4.3, 4.3 mm, HBOM with gold/palladium and examined using a 064:01865; 3.0, 3.1, 3.2, 3.4, 3.6 mm, USNM Zeiss Novascan-30 scanning electron micro­ 859443; 3.2, 3.2, 3.2, 3.4, 4.1 mm, MCZ scope. 30251 0; 1.7, 3.4, 3.4, 3.8, 3.8 mm, SBMNH All cited anatomical measurements were 35167. Total material: 262 specimens: FLOR­ taken from specimens of average size (see IDA: Ft. Pierce Inlet: 10 March 1987, 3; 2-3 under descriptions). Throughout the text, May 1987, 73; 24 June 1987, 91; 03 August "relaxed" refers to the condition of an animal 1987, 2; 14 August 1987, 10; 31 August 1987, in normal crawling posture and does not refer 1; 28 December 1987, 7; 11 March 1988, 7; to any chemical treatment. 12 April 1988, 38; 16 October 1990, 2; 03 Cited institutions are (* indicates location of February 1991; 13. -Sebastian Inlet: 30 De­ type and other voucher material): cember 1987, 26. -St. Lucie Inlet: 18 February 1982, 2. AMNH- American Museum of Natural His­ tory, New York, New York Type locality DMNH- Delaware Museum of Natural His­ tory, Wilmington Ft. Pierce Inlet, Indian River Lagoon, St. *FMNH- Field Museum of Natural History, Lucie County, eastern Florida, 27"28.3'N, Chicago, Illinois 80°17.9'W, occupying Lysiosquilla scabri­ HBOI- Harbor Branch Oceanographic In- cauda burrows on intertidal sand flats with stitution, Ft. Pierce, Florida patches of the seagrass Halodule wrightii As­ *HBOM- Harbor Branch Oceanographic cherson. Paratypes all from type locality. Museum [formerly Indian River Coastal Zone Museum], HBOI Diagnosis *MCZ- Museum of Comparative Zoology, Harvard University, Cambridge, Animal translucent white. Mantle thin, with Massachusetts retractable, papillose folds covering anterior *SBMNH-Banta Barbara Museum of Natural and posterior thirds of shell. Tentacles origi­ History, California nating at dorsal shell margin, two pairs ante­ SMSLP- Smithsonian Marine Station at riorly, two pairs posteriorly. Posterior foot­ Link Port, Ft. Pierce, Florida extension relatively short. Shell roundly NEW SPECIES OF COMMENSAL GALEOMMATIDAE 3

FIGS. 1-3. Photographs of living animals. 1. Divariscintilla octotentacuJata. 2. D. Juteocrinita. 3. D. cordi- (ormis. Scale bars = 1.0 mm. 4 MIKKELSEN & BIELER

II by sh vgr pte

It

FIGS. 4-7. External appearance and internal shell morphology. Tentacle pairs numbered from anterior to posterior (for text reference only; identical numbers do not imply homology). 4. Divariscintilla octotentaculata, in crawling position, from left side. 5. D. luteocrinita, same as Fig 4. 6. D. cordiformis, same as Fig. 4. 7.0. octotentaculata, internal surface of right valve, showing approximate locations of muscle insertions. Scale bars = 1.0 mm. (aam, anterior adductor muscle scar; apr, anterior pedal retractor muscle scar; bag, byssus adhesive gland; by, location of byssus gland; c, cowl; est, club-shaped tentacles; exc, excurrent "siphon"; ft, foot; inc, incurrent "siphon"; ind, shell indentation; m, mantle fold; mf, point of mantle fusion; mp, mantle pouch; mpt, median pallial tentacle; pam, posterior adductor muscle scar; pdc, prodissoconch; pte, posterior foot-extension; ppm, pedal protractor muscle scar; ppr, posterior pedal retractor muscle scar; sh, shell; vgr, ventral pedal groove). triangular, with umbo slightly anterior, smooth papillae along ventral margin of shell. Two exteriorly, with weak radial ribs interiorly; pallial openings: (1) anteropedal opening, length approximately 70% of extended mantle from a point anterior to umbones to a point length. No "flower-like organ" on anterior sur­ posterior to foot (Fig. 4, mf), forming exten­ face of visceral mass. sive anterior cowl (Fig. 4, c), the edges of which are held together to form an effective incurrent "siphon" (Fig. 4, inc); and (2) pos­ Description terodorsal excurrent opening (Fig. 4, exc) be­ tween posterior tentacle pairs, either as sim­ External Features and Mantle: Living ex­ ple opening or on rounded protuberance tended animal (Figs. 1, 4) generally 5-7 mm in forming distinct siphon; appearance depen­ length, translucent white except for dark di­ dent on degree of pallial expansion. Posterior gestive gland within visceral mass. Shell mantle fusion forming a rounded, protruding largely external, with only anterior and poste­ pouch (Fig. 4, mp) containing the gills. Two rior thirds of shell covered in life by mantle pairs (one long, one short) retractable, ante­ folds (Fig. 4, m), not meeting at lateral mid­ rior tentacles arising from near shell edge; line. Mantle folds fully retractable, finely pap­ dorsalmost pair longest. Two pairs (one long, illose, with scattered larger papillae. Mantle one short) retractable tentacles in vicinity of thin, extending beyond shell edges; entire excurrent siphon, also arising from near shell surface finely papillose, with fringe of longer edge; posteriormost pair longest. A single, NEW SPECIES OF COMMENSAL GALEOMMATIDAE 5 short, mid-dorsal tentacle (Fig. 4, mpt), just Organs of the Pallial Cavity: Foot (Fig. 4, ft) as posterior to umbo. An additional 1-2 pairs of previously described for Divariscintilla yoyo short tentacles (=enlarged papillae?) in (see Mikkelsen & Bieler, 1989), including larger specimens (approximately 5 mm) at hatchet-shaped anterior portion, narrowed ventral shell edge at anterior and posterior posterior extension (Fig. 4, pfe), anterior bys­ ends of ventral papillose fringe. Each tentacle sus gland (Fig. 4, by), ciliated ventral groove with papillose surface and central core of lon­ (Fig. 4, vgr) supplied with numerous mucous gitudinal muscle and nerve fibers, visible as glands, and terminal byssus adhesive gland an inner "thread" under low magnification. In­ (Fig. 4, bag). Byssus gland of undefined ner pallial fold of non-shell areas (e.g., cowl, structure, staining turquoise in histological ventral mantle margin, posterior pouch) highly sections; byssus adhesive gland of branching muscular. lamellar folds, staining purplish-red. One to Preserved specimens completely (or nearly four byssus threads produced, emanating so) retracted into shell, however, shell usually from extreme posterior tip of foot. Opaque gaping, with tentacles (especially anterodor­ white pigment band (of unknown function) sal) slightly protruding beyond shell edges. along anterodorsal tip of foot, staining dark purplish-red in sections. Shell (Figs. 7-11, 13): Shell generally 3-5 mm Anterior and posterior adductor muscles in length, roundly triangular, longer posteri­ subequal, of moderate diameter. Anterior and orly, equivalve, rather compressed, glossy, ir­ posterior pedal retractor muscles smaller in idescent, transparent, smooth except for fine diameter, inserting on shell just dorsal and concentric growth lines and weak radial ribs medial to their respective adductor muscle most evident interiorly at ventral margin (Fig. scars. Very small pedal protractor muscle 9). Size large relative to mantle, comprising merging with anteroventral edge of anterior approximately 70% of extended mantle adductor muscle just before both attach to length. Valves held open at a 50-60x angle shell; inserting into anterior visceral mass just while crawling, capable of complete closure dorsal of labial palps. Muscles leaving very ventrally but gaping slightly anteriorly and faint attachment scars on shell (Figs. 7, 9). posteriorly. Adductor muscle scars faint, Overall morphologies of visceral mass, la­ subequal (Figs. 7, 9). Pallial line entire, indis­ bial palps and ctenidia as in Divariscintilla tinct. Periostracum colorless, most evident at yoyo (see Mikkelsen & Bieler, 1989). Palps ventral shell edge (Fig. 9, per). with 6-8 lamellae each side. Ctenidia smooth, Hinge line short (Fig. 10). One small, unpleated (appearing posteriorly loosely rounded cardinal tooth (Fig. 10, car) in each pleated in preserved specimens due to con­ valve, that of left valve sometimes slightly bi­ traction). Outer demibranch approximately fid; lateral teeth absent. Cardinal teeth abut­ 50% smaller than inner; both demibranchs ting, not interlocking. External ligament (Fig. ventrally rounded and with both interfilamen­ 10, lig) weak, amphidetic, supported by tal and interlamellar connectives. Cilial cur­ nymph. Internal ligament (resilium; Fig. 10, rents on palps and ctenidia not verified. res) stronger, opisthodetic. Flower-like organ absent (see Discussion Prodissoconch (Fig. 11) brownish-yellow, below). approximately 360 fm in length. Prodisso­ conch I corresponding in size to shell of newly Digestive System: Structure of digestive sys­ released larva, approximately 32% of length tem (mouth, esophagus, stomach, midgut, of prodissoconch II; sculpture not discernible hindgut, rectum) of same organization as that (surface abraded in adult shell). Prodisso­ in Divariscintilla yoyo (see Mikkelsen & Bieler, conch II sculptured only with coarse and fine 1989: fig. 28). concentric growth lines. Prodissoconch I and Suprabranchial Chamber: Arrangement of II stages distinct, demarcated more by openings and presence of glandular patches change in convexity than by sculpture or (?hypobranchial glands; Fig. 23, hyp) adja­ growth discontinuity (Fig. 11, single arrow). cent to rectum as in Divariscintilla yoyo (see Demarcation between prodissoconch II and Mikkelsen & Bieler, 1989: fig. 29). dissoconch abrupt (Figs. 8; 11, double arrow). Shell microstructure (Fig. 13) cross­ Nervous System: Arrangement of ganglia, lamellar centrally, with thin prismatic layer statocysts, and major nerves as described for covering each side, as in Divariscintilla yoyo Divariscintilla yoyo (see Mikkelsen & Bieler, (see Mikkelsen & Bieler, 1989). 1989: fig. 31 ). Left and right posterior tenta- 6 MIKKELSEN & BIELER cles innervated by branches from the pallial and Sebastian Inlet (Brevard County, nerve, adjacent to its junction with the visceral 27°51.6'N, 80°27.0'W). May be quite numer­ ganglion. Anterior tentacles similarly inner­ ous; largest number per burrow sample = 74. vated but both from a common branch of the pallial nerve, adjacent to its junction with the Etymology cerebro-pleural ganglion. Reproductive System: Simultaneous her­ An adjective, octotentaculatus, -a, -um, maphrodite. Ovotestis white, encompassing from the Latin octo (eight) and the late Latin most of volume of visceral mass, as in Di­ tentaculum (a "feeler"), referring to the eight variscintilla yoyo (see Mikkelsen & Bieler, long mantle tentacles, a diagnostic feature. 1989). Mature spermatozoa morphologically indis­ Remarks tinguishable from that of D. yoyo (see Eckel­ barger et al., 1990: figs. 28-29, table 1; D. This is the most common of the five Divaris­ octotentaculata as Scintilla sp.), except cintilla species in the Lysiosquilla burrows smaller in relative size. Spermatogenesis fully (see Ecology and Behavior). described by Eckelbarger et al. (1990; as Prior to the beginning of this study in March Scintilla sp.). 1987, two individuals of this species were en­ Brooding large number of small larvae for countered, and are presently the only known variable period; brooding time for individuals specimens of any of the Floridian burrow ga­ collected with larvae, 9-15 days (n = 4); total leommatoideans from previous collections. brooding time from set to release in labora­ These were collected in a shovel-and-sieve tory, 9, 10, and 12 days (n = 3). Larvae held sample from a sand bar in the Indian River within both demibranchs and in suprabran­ Lagoon, north of St. Lucie Inlet, Martin chial chamber, where they are circulated via County, Florida, 27°11.4'N, 80°11.1 'W, on 18 pallial expansions and contractions. During February 1982. These individuals were main­ brooding, excurrent siphonal opening con­ tained in the laboratory for approximately four stricted by sphincter-like muscle, sometimes months, providing material for notes and pho­ noted around free end of rectum, allowing di­ tographs on behavior, reproduction, and de­ gestive processes to continue. Larvae initially velopment. white, turning pink with shell development on day 5-7 (n = 2); released as straight-hinged Divariscintilla luteocrinita n. sp. "D" larvae with apical flagella, 115-123 ILm in (Figs. 2, 5, 14-22, 24-25) shell length ( x = 119 f.lm, n = 40; Fig. 12). Larvae expelled through excurrent siphon via Material examined strong contractions of shell and pallial mus­ cles. Adults brooding larvae collected in May, Holotype: 5.0 mm (shell length), FMNH June, December 1987, and March, April 223403. Paratypes (12): 4.6 mm, FMNH 1988; additional adults setting larvae in labo­ 223407; 4.4 mm (shell only), FMNH 223404; ratory in February, May, June 1982 and No­ 3.2, 3.9 mm, HBOM 064:01863; 4.9, 4.5, 4.1, vember 1990; one specimen setting two 2.9 mm (shells only, coated for SEM), HBOM broods in laboratory, four months apart, with 064:01864; 4.8 mm, USNM 860195; 5.5 mm second brood approximately 20% quantity of (shell only), USNM 859444; 3.4 mm, MCZ first. No apparent seasonality. 302517; 3.5 mm, SBMNH 35168. Total mate­ Circulatory and Excretory Systems: As de­ rial: 16 specimens: FLORIDA: Ft. Pierce Inlet: scribed for Divariscintilla yoyo (see Mikkelsen 10 March 1987, 1; 2-3 May 1987, 5; 24 June & Bieler, 1989). 1987, 1; 03 August 1987, 1; 14 August 1987, 2; 31 August 1987, 1; 12 April 1988, 1; 03 Distribution and Abundance February 1990; 4.

Known from three locations, all on intertidal Type locality and shallow subtidal sand flats within the In­ dian River Lagoon, eastern Florida: the type Ft. Pierce Inlet, Indian River Lagoon, St. locality, Ft. Pierce Inlet (St. Lucie County, Lucie County, eastern Florida, 27"28.3'N, 27"28.3'N, 80°17.9'W), just north of St. Lucie 80°17.9'W, occupying Lysiosqui/la scabri­ Inlet (Martin County, 27"11.4'N, 80°11.1 'W), cauda burrows on intertidal sand flats with NEW SPECIES OF COMMENSAL GALEOMMATIDAE 7

FigS. 8-13. Shell of Divariscintilla octotentaculata (SEM). 8. Left valve, external view, 2.9 mm length, para- type, HBOM 064:01867. 9. Right valve, internal view, 3.6 mm length, paratype, HBOM 064:01867. 10.Hinge, anterior to left, paratype, HBOM 064:01867. Scale bar = 100 ILm. 11. Prodissoconch, 360 ILm length. Single arrow = prodissoconch I-II boundary. Double arrow = prodissoconch II-dissoconch boundary. 12. Newly released larval shell, 119 ILm length. 13. Microstructure, with internal surface at top. Scale bar = 5 ILm. (car, cardinal tooth; Iig, external ligament; nym, nymph; per, periostracum; res, resilium). 8 MIKKELSEN & BIELER

Figs. 14-20. Shell of Divariscintilla luteocrinita (SEM). 14. Left valve, external view, 2.9 mm length, paratype, HBOM 064:01864. 15. Right valve, internal view, 4.9 mm length, paratype, HBOM 064:01864. 16. Hinge, anterior to left, paratype, HBOM 064:01864. Scale bar = 100 fLm. 17. Prodissoconch, 390 fLm length. Single arrow = prodissoconch I-II boundary. Double arrow = prodissoconch II-dissoconch boundary. 18. Internal surface, showing smooth adductor muscle scar (left) and adjacent region of opaque thickening (right). Scale bar = 10 fLm. 19. Microstructure in region of adductor muscle scar; internal surface at top. Scale bar = 5 fLm. 20. Microstructure in region of opaque thickening, showing additional layer covering internal prismatic layer (pr); internal surface at top. Scale bar = 5 fLm. (pr, internal prismatic layer). NEW SPECIES OF COMMENSAL GALEOMMATIDAE 9 patches of the seagrass Halodule wrightii As­ ing most of shell surface; tentacles, cowl, cherson. Paratypes all from type locality. posterior pouch, and foot contracted but still usually extending beyond shell edges. Diagnosis Shell (Figs. 14-20): Shell generally 4-5 mm in length, roundly triangular to oval, longer pos­ Animal translucent yellow. Mantle thin, with teriorly, equivalve, rather inflated, glossy, extensive, retractable, papillose folds com­ transparent to translucent white, smooth ex­ pletely covering shell, meeting at mid-line. cept for fine concentric growth lines and irreg­ Tentacles originating at shell edge, three ular opaque thickening interiorly, imparting a pairs anteriorly, two singles and 9-11 pairs white-blotched pattern (Fig. 15). Size large rel­ posteriorly, plus one pair club-shaped tenta­ ative to mantle, comprising approximately cles adjacent to excurrent opening. Posterior 70% of extended mantle length. Valves held foot-extension relatively short. Shell roundly open at approximately 40° angle while crawl­ triangular, with umbo slightly anterior, smooth ing, incapable of complete closure. Adductor exteriorly, with opaque thickenings interiorly; muscle scars subequal, distinct due to pres­ length approximately 70% of extended mantle ence of surrounding shell thickening (Fig. 15). length. Single "flower-like organ" on anterior Periostracum as in Divariscintilla octotenta­ surface of visceral mass. culata. Hinge line short (Fig. 16), similar to that of Description Divariscintilla octotentaculata. Both cardinal teeth rounded. External Features and Mantle: Living ex­ Prodissoconch (Fig. 17) brownish-yellow, tended animal (Figs. 2, 5) generally 6-7 mm in approximately 390 f..tm in length. Prodisso­ length. Mantle and tentacles translucent pale conch I approximately 145 f..tm in length, ap­ yellow; foot white. Upper portion of digestive proximately 37% of length of prodissoconch gland showing through mantle and shell as II; sculpture not discernible (surface abraded dark elongate-oval spot. Shell entirely cov­ in adult shell). Prodissoconch II sculptured ered in life by anterior and posterior mantle with coarse concentric growth lines. Demar­ folds (Fig. 5, m), meeting at lateral dorso-ven­ cation between prodissoconch I and II stages tral midline on each side. Mantle folds thin, (Fig. 17, single arrow), and between prodis­ incompletely retractable, entirely finely papil­ soconch II and dissoconch (Figs. 14; 17, dou­ lose, with scattered, elongated papillae espe­ ble arrow) as in Divariscintilla octotentaculata. cially posteroventrally. Mantle edge extending Shell microstructure as in Divariscintilla oc­ widely beyond shell edges; entire surface totentaculata, except with additional layer of finely papillose. Pallial openings, muscula­ parallel crystals covering internal perpendic­ ture, and posterior pouch as in Divariscintilla ular prismatic layer, forming regions of octotentaculata. Numerous, long, retractile opaque thickening (Figs. 18-20). tentacles originating at shell edge: three pairs anterior to umbo; two singles plus five pairs Organs of the Pallial Cavity: Foot (Fig. 5, ft) as posterior to umbo ( = two singles on midline in Divariscintilla octotentaculata. Adductor, + two pairs + [excurrent siphon] + three pedal retractor, and pedal protractor muscles pairs). Shorter accessory pairs posterior to (including relative positions) as in D. octoten­ umbo originating from mantle fold near, but taculata. Muscles leaving distinct attachment ventrad of, shell edge: one to three pairs an­ scars on shell (Fig. 15). terior, two to three pairs posterior to excurrent Visceral mass, labial palps and ctenidia as siphon. Structure of these tentacles as in D. in Divariscintilla octotentaculata. Palps with octotentaculata; those on shell edge adjacent approximately 8 lamellae each side. Outer to cowl and posterior pouch (third and sixth, demibranch approximately 40% smaller than see numbers, Fig. 5) longest. One prominent inner. Cilial currents on palps and ctenidia un­ pair of thicker, whitish, club-shaped tentacles known. (Fig. 5, est) immediately posterior to excurrent A single "flower-like organ" (Figs. 21-22; siphon originating just inside shell edge; inter­ see Mikkelsen & Bieler, 1989, for explanation nal structure differing slightly from that of of term) on anterior surface of visceral mass other tentacles (see Remarks). just ventral to labial palps. Size variable, not Preserved specimens incompletely re­ correlated with shell length. tracted into gaping shell; mantle folds con­ Digestive System: As in Divariscintilla oc­ tracted to narrow rim along shell edge, expos- totentaculata. 10 MIKKELSEN & BIELER

Suprabranchial Chamber: As in Divariscintilla is found in the outer surfaces of the tentacles octotentaculata, except that the whitish glan­ of D. luteocrinita, which are highly papillose dular patches (?hypobranchial glands) are and convoluted rather than smooth as in D. much more extensive (Fig. 24). maoria as shown by Judd (1971: fig. 6). Inter­ nally, the club-shaped tentacles of D. luteo­ Nervous System: Arrangement of ganglia, crinita (Figs. 5, 25, est) are identical in struc­ statocysts, and major nerves as described for ture to normal tentacles except that the Divariscintilla yoyo (see Mikkelsen & Bieler, muscle fibers (Fig. 25, arrow) are dispersed 1989: fig. 31 ). Additional tentacular nerves over the surfaces of the septa instead of be­ arising (independently) from pallial nerve. ing concentrated at the core of the tentacle. Reproductive System: Overall gross morphol­ This difference may allow this particular pair ogy as in Divariscintilla octotentaculata. Re­ of tentacles to undergo stronger contraction, productive mode could not be determined resulting in the club-like shape. Under full ex­ from sectioned specimen, which showed no tension, the club shape and whitish coloration recognizable developed gametes. Adults of these tentacles disappears, indicating that brooding larvae have not been collected. these features are products of the normally contracted state. Circulatory and Excretory Systems: As in Di­ The function of the club-shaped tentacles is variscintilla octotentaculata. unknown. They are probably not homologous to the posterior "defensive appendages" of D. Distribution and Abundance maoria (see Judd, 1971: fig. 7) or Galeomma takii (Kuroda, 1945) (see B. Morton, 1973a: Known only from the type locality, Ft. fig. 5), which can be autotomized and pos­ Pierce Inlet, St. Lucie County, Florida, sess only a single, central haemocoelic tube. 2JC28.3'N, 80°17.9'W, on intertidal and shal­ No tentacles in D. luteocrinita have this mor­ low subtidal sand flats. Uncommon; only 16 phology nor were they ever seen to autoto­ specimens known. mize. However, these tentacles were often observed to hyperelongate when the animals Etymology were disturbed, for example during specimen transfer between laboratory dishes. While An adjective, luteocrinitus, -a, -urn, from the most other tentacles contracted, the club­ Latin luteus (yellow) and the Latin crinitus shaped tentacles elongated immediately to 2- (hairy}, referring to the numerous, long, yel­ 3 times the shell length just as the transfer lowish tentacles, imparting an overall "hairy" spoon made contact. This bears resemblance appearance. to the dymantic ("threatening") display of ten­ tacles in Galeomma polita Deshayes, 1856 Remarks (see B. Morton, 1975), and Ephippodonta oe­ dipus Morton, 1976 (see B. Morton, 1976), The single posterior pair of club-shaped when disturbed, and suggests defensive tentacles is distinct and consistent in both liv­ function. Unlike the dymantic tentacles of the ing and preserved specimens. Normal tenta­ latter two species, however, the club-shaped cles (Fig. 25, nt; similar morphology in all five tentacles of D. luteocrinita do not fully retract Floridian Divariscintilla spp.} show usually into the mantle at rest. four haemocoelic compartments in cross sec­ The large "?hypobranchial glands" of this tion, each of these supplied with a longitudinal species are located at sites similar to those of muscle bundle and nerve fiber, and separated the smaller glands of other Divariscintilla spe­ by connective tissue septa. The muscle and cies, i.e., adjacent to the rectum and the bran­ nerve fibers form a more-or-less concentrated chial nerves as they join the visceral ganglia. central core, appearing as a central thread In histological sections, they bear striking re­ under low magnification. Judd (1971: fig. 6) semblance to "seminal receptacles" de­ figured a similar internal morphology for ten­ scribed and figured for Aligena elevata tacles of Divariscintilla maoria, but the individ­ (Stimpson, 1851) by Fox (1979: 101, 103, fig. ual compartmental muscle-plus-nerve bun­ 32), although in the single sectioned speci­ dles are not as concentrated at the core of the men of D. luteocrinita, they contained no tentacle; this difference may not be real, but sperm. The montacutid Aligena elevata is a rather implied by Judd's interpretation of the protandrous hermaphrodite, and its seminal histological sections. An additional difference receptacles are present only during the fe- NEW SPECIES OF COMMENSAL GALEOMMATIDAE 11

Figs. 21-22. Flower-like organ of Divariscintilla Juteocrinita (SEM). Anterior tip of foot has been severed to enhance visibility. 21. Scale bar = 100 fLm. 22. Scale bar = 50 fLm. (ct, ctenidium; fl, flower-like organ; ft, foot; Ip, labial palp; m, mantle).

male stage. The occurrence of such struc- cauda burrows on intertidal sand flats with tures in Galeommatoidea was summarized by patches of the seagrass Halodule wrightii As- Fox (1979: table 8, as Leptonacea, 15 spe- cherson. Paratypes from type locality (FMNH, cies), who noted that sperm storage organs USNM, HBOM 064:01861) or Ft. Pierce Inlet were unknown outside of Montacutidae. How- (HBOM 064:01862). ever, protandry is known in members of other families (e.g. Lasaeidae: Arthritica crassi- Diagnosis (ormis Powell, 1933 (see B. Morton, 1973b); see also Fox, 1979: table 11). The reproduc- Animal translucent white. Mantle thin, with tive mode of D. Juteocrinita is presently un- extensive, retractable papillose folds covering known, but seminal receptacles and/or shell completely, meeting at midline. Tenta- protandry would be no surprise within the cles originating at shell edge, six pairs ante- context of this reproductively complex super- riorly, eight pairs posteriorly. Posterior foot- family. extension relatively short. Shell oval, with umbo slightly anterior; length approximately Divariscintilla cordiformis n. sp. 65% of extended mantle length. Small, ven- (Figs. 3, 6, 26-32) tral, anteriorly directed indentation in each valve. Coarse growth lines and slightly Material Examined beaded radial ribs restricted to edges of oth- erwise-smooth shell. Single "flower-like Holotype: 5.6 mm (shell length), FMNH organ" on anterior surface of visceral mass. 223405. Paratypes (4): 6.4 mm (sectioned on 29 microslides), FMNH 223406; 5.4 mm, Description HBOM 064:1861; 4.9 mm (partially dissected; prodissoconch coated for SEM), HBOM 064: External Features and Mantle: Living ex- 01862; 6.4 mm (shell only, coated for SEM), tended animal (Figs. 3, 6) generally 7-10 mm USNM 859445. Total material: 6 specimens: in length, translucent white except for dark FLORIDA: Ft. Pierce Inlet: 24 June 1987, 2; digestive gland within visceral mass. Shell en- -Peanut Island: 10 August 1987, 4. tirely covered in life by anterior and posterior mantle folds (Fig. 6, m) meeting at lateral Type locality dorso-ventral mid-line. Mantle folds thin, in- completely retractable, entirely finely papil- Peanut Island, near Lake Worth Inlet, Palm lose, with scattered larger papillae, which are Beach County, eastern Florida, 26°46.6'N, longest at posteroventral section. Mantle 80002.7'W, occupying Lysiosquilla scabri- edge extending widely beyond shell edges; 12 MIKKELSEN & BIELER

25

Figs. 23-25. Histological sections. 23. ?Hypobranchial gland adjacent to rectum in D. octotentaculata. 24. ?Hypobranchial gland adjacent to rectum in D. luteocrinita. 25. Cross-sections of normal and club-shaped tentacles in D. luteocrinita. Arrow = muscularized septum. Scale bars = 100 ~m. (cst, club-shaped tentacle; ct, ctenidium; hyp, ?hypobranchial gland; mus, muscle fibers; n, nerve fiber; nt, normal tentacle; pam, posterior adductor muscle; r, rectum; sbc, suprabranchial chamber; sep, connective tissue septum; sh, shell; ten, tentacle). entire surface finely papillose, with additional octotentaculata. Excurrent opening (Fig. 6, enlarged papillae near shell edge. Ventral exc) between ninth and tenth tentacle pairs. mantle edge entire, not cleft in vicinity of ven- Preserved animals not fully retracted into tral shell indentation. Pallial openings, mus- gaping shell; mantle folds contracted to nar- culature, and posterior pouch as in Divariscin- row rim along shell edge, exposing most of tilla octotentaculata. Paired, retractable, shell surface; tentacles, cowl, and posterior pallial tentacles numerous, originating near pouch contracted but still usually extending shell edge. Six anterior pairs, those adjacent beyond shell edges; foot usually completely to cowl area (third and fourth, see numbers, withdrawn into pallial cavity. Fig. 6) longest. Eight posterior pairs, those adjacent to excurrent siphon (tenth) longest, Shell (Figs. 26-30, 32): Shell generally 5·7 but shorter than longest anterior tentacles. A mm in length, nearly evenly oval, longer pos- single median tentacle (Fig. 6, mpt) between teriorly, equivalve, compressed, glossy, trans- first and second posterior pairs (Fig. 6, nos. parent to translucent white. Small indentation 7,8). Structure of individual tentacles as in D. (Figs. 6, ind; 27, arrow; 28). at mid-ventral NEW SPECIES OF COMMENSAL GALEOMMATIDAE 13

Figs. 26-32. Shell of Divariscintilla cordiformis (SEM). 26. Right valve, external view, 6.4 mm length, para- type, USNM 859445. 27. Right valve, internal view, 6.4 mm length, paratype, USNM 859445. Arrow = ventral indentation. 28. Close-up of ventral indentation, interior view. Scale bar = 100 IJom.29. Hinge, anterior to left. Scale bar = 200 IJom.30.Prodissoconch, 360 IJomlength, paratype, HBOM 064:01862. Single arrow = prodissoconch 1-11 boundary. Double arrow = prodissoconch II-dissoconch boundary. 31. Newly released larval shell, 1461Jomlength. 32.Microstructure, with internal surface at top. Scale bar = 5 IJom.(per, periostracum). 14 MIKKELSEN & BIELER margin, slanting anteriorly toward umbo, evi­ confirmation of structure through gross dis­ dent only on distal 1 mm or so of shell growth section. (as evidenced by growth lines). Exterior Suprabranchial Chamber: As in Divariscintilla sculpture smooth except for fine concentric octotentaculata. growth lines, heavier at anteroventral margin, anterior to indentation. Beaded radial ribs re­ Nervous System: Arrangement of ganglia, stricted to distal 1 mm or so of shell edge, statocysts, and major nerves as described for most prevalent interiorly at posteroventral Divariscintilla yoyo (see Mikkelsen & Bieler, margin (Fig. 27) and exteriorly at antero- and 1989: fig. 31 ). Additional tentacular nerves posterodorsal margins (Fig. 26), forming dis­ arising (independently) from pallial nerve. tinct, fine crenulation at shell edge, absent Reproductive System: Simultaneous her­ only at ventral margin immediately anterior to maphrodite. Overall gross morphology as in indentation. Size large relative to mantle, Divariscintilla octotentaculata. comprising approximately 65% of extended One specimen brooding larvae collected in mantle length. Valves held open at 20-30° an­ August 1987. Larvae released one day after gle while crawling, incapable of complete clo­ collection. Newly-released larval shells 136- sure. Adductor muscle scars subequal, faint. 148 J..tm in length (x = 143 J..tm, n = 40; Fig. Periostracum as in Divariscintil/a octotentac­ 31 ). Adult preserved and subsequently sec­ ulata; also evident covering ventral indenta­ tioned; apparently intact larvae found in su­ tion (Fig. 28, per). prabranchial chamber and throughout diges­ Hinge line (Fig. 29) short, as in Divariscin­ tive system, including intestine and rectum tilla octotentaculata, with two small rounded (therefore not being digested). cardinal teeth. Prodissoconch (Fig. 30) brownish-yellow, Circulatory and Excretory Systems: As in Di­ approximately 360 J..tm in length. Prodisso­ variscintilla octotentaculata. conch I corresponding in size to shell of newly released larva, approximately 45% of length Distribution and Abundance of prodissoconch II; sculpture not discernible (surface abraded in adult shell). Prodisso­ Known from the type locality at Peanut Is­ conch II sculptured with coarse concentric land, Palm Beach County, and from sand flats growth lines. Demarcation between prodisso­ at Ft. Pierce Inlet, St. Lucie County, Florida, conch I and II stages (Fig. 30, single arrow), 27°28.3'N, 80°17.9'W. Rare; only 6 speci­ and between prodissoconch II and disso­ mens known. conch (Fig. 30, double arrow) as in Divaris­ cintilla octotentaculata. Etymology

Organs of the Pallial Cavity: Foot and shell An adjective, cordiformis, -e, from the Latin muscles (adductors, pedal retractors, pedal cordis (heart) and the Latin forma (shape), protractors, including relative positions) as in referring to the ventrally indented shell out­ Divariscintilla octotentaculata. Muscles leav­ line. ing very faint attachment scars on shell (Fig. 27). Remarks Visceral mass, labial palps and ctenidia as in Divariscintilla octotentaculata. Palps with As in Divariscintilla maoria (see Judd, approximately seven lamellae each side. 1971 ), the ventral indentation in the shell of Outer demibranch approximately 35% smaller this species does not seem to be functionally than inner. Cilial currents on palps and ctenidia important. In both species, it is present in both unknown. valves, anteriorly inclined, not developed in Single "flower-like organ" (see Mikkelsen & juveniles, and not reflected by soft anatomy. Bieler, 1989) on anterior surface of visceral mass just ventral to labial palps. ECOLOGY AND BEHAVIOR Digestive System: Similar to that of Divaris­ cintilla octotentaculata (relative positions of As in the two previously described com­ gastric shield, style sac, digestive diverticula, mensal galeommatids (Mikkelsen & Bieler, midgut, etc.), based on histological sections. 1989), no specimens of the newly described Limited number of specimens did not permit species were ever found physically attached NEW SPECIES OF COMMENSAL GALEOMMATIDAE 15 to a mantis shrimp, either in the field or in row when offered a substrate of loose sand in museum specimens (HBOM). They are as­ the laboratory. sumed to be free-living within the vertical por­ All three Divariscintilla species previously tions of the U-shaped burrow, although spec­ described (D. maoria, Judd, 1971: fig. 4; D. imens were never visible at the opening prior yoyo and D. troglodytes, Mikkelsen & Bieler, to pumping. Again as with the previous spe­ 1989: fig. 32) are known to "hang" from a cies (Mikkelsen & Bieler, 1989), these clams vertical substrate by the posterior foot-exten­ were never found free-living outside of the sion, which in these species is extremely long burrows or associated with any other burrow­ and elastic; byssus threads secreted by the ing invertebrate in the area (e.g. other mantis anteriorly located byssus gland are laid down shrimps, callianassid shrimps, polychaetes, within the ventral groove of the foot and sipunculans), nor were any empty shells lo­ emerge from the terminus to attach to the cated in dry collections (AMNH, DMNH, substrate. The threads are secured within the FMNH, HBOM, USNM), probably because of groove by secretions of the posteriorly lo­ their fragile nature. cated byssus adhesive gland. Byssus and Divariscintilla octotentaculata was the most byssus adhesive glands of similar morpholo­ frequently encountered commensal mollusk in gies are present in each of the three new spe­ the Lysiosquilla burrows; of the 35 burrows cies described here and are assumed to func­ containing mollusks, 31 contained D. octoten­ tion in the same way. This has been taculata, 20 D. yoyo, 19 D. troglodytes, 8 D. confirmed for D. octotentaculata and D. luteo­ luteocrinita, 6 Cyclostremiscus beauii, 7 Cir­ crinita, in which secretion of byssus threads, culus texanus, and only 2 D. cordiformis. Di­ accompanied by distinct pulsing of the byssus variscintilla octotentaculata was usually col­ gland area, was observed as described for D. lected with other commensals, occurring alone yoyo and D. troglodytes (Mikkelsen & Bieler, in only 6 of the 31 samples. Divariscintilla lu­ 1989). Following this activity, the clam hangs teocrinita was always collected with other from the posterior foot-extension, with the commensals. Divariscintilla cordiformis was byssus threads emerging from the posterior collected once with D. octotentaculata, and terminus of the foot in the vicinity of the bys­ once alone. Densities of D. octotentaculata sus adhesive gland. The posterior foot-exten­ varied greatly, ranging from 1-74 per sample sion of these species, as well as of D. cordi­ (x = 8.3, n = 31 ). Divariscintilla luteocrinita formis, is not as elongated and extensible as was usually present in numbers of only one or in those previously described, therefore the two specimens per burrow; one sample con­ distinctive "hanging" posture, wherein the tained four specimens. Divariscintilla cordi­ clam "dangles" from an elongated foot, is not formis was encountered only twice, once as as pronounced. 3 two specimens, once as four. Only a small A peculiar interaction between pairs of Di­ number of burrows sampled contained com­ variscintilla species was observed in the lab­ mensals. And, as previously reported (Mik­ oratory on three occasions. In two instances kelsen & Bieler, 1989), it must be emphasized involving D. octotentaculata, one animal of a that in no case could an entire burrow be sam­ pair was noted reaching its foot into the man­ pled using the yabby pump, which only effec­ tle cavity of the second specimen, either from tively samples its own length (0.5-1.0 m) of the in front of or behind its partner. On one of vertical parts of the U-shaped burrow. Esti­ these occasions, the two individuals per­ mates of occurrence and/or density of any formed this activity simultaneously, "facing" clams living in the deeper horizontal section of one another, with each one reaching around the burrow was thus not possible. the visceral mass of the other to contact the Animals of all three species spent most of posterior surface with the tip of its foot (Fig. their time in the laboratory attached to the 33). Two specimens of D. yoyo have been glass surface of laboratory bowls by up to four byssus threads, and it is assumed that this is 3 Careful notes were not recorded on the behavior of D. also their habit on the smooth walls of the cordiformis in the early phase of the study, and the inavail­ Lysiosquilla burrow. When dislodged, they ability of additional living specimens prevented confirma­ actively crawl about using an even, gliding tion of the presence or absence of "hanging" behavior. motion produced by ciliary action on the cen­ Morphology suggests that this behavior does occur, how­ ever, the shorter posterior extension and the absence of tral surface of the foot. This was equally ef­ any mention in our preliminary written observations indi­ fective on the underside of the water surface cates that the "hanging'' posture was inconspicuous, as in as on glass. They made no attempts to bur- D. octotentaculata and D. luteocrinita. 16 MIKKELSEN & BIELER

Fig. 33. Mating (?) behavior between two specimens of Divariscintilla octotentaculata, as observed in laboratory. noted performing this same type of activity. In We regarded the presence of an apparently all three instances, the interaction was initi­ functionless (Judd, 1971) shell notch in D. ated by the smaller of the two specimens of maoria, as well as the difference in degree of the pair, and the activity was sustained for 3-7 shell coverage by the mantle, as species­ minutes. Although there is no direct evidence, level rather than generic characters. At the it seems likely that this observed interaction is time, we also considered placement of D. part of some sort of reproductive activity, per­ yoyo and D. troglodytes in the monotypic haps stimulation of sperm transfer (external genus Phlyctaenachlamys Popham, 1939, gonadal openings are located on the poster­ based on P lysiosquillina Popham, 1939. odorsal surface of the visceral mass). Each of However, there are a number of anatomical the two specimens involved in the simulta­ characters that distinguish the Divariscintilla neous behavior described above had larvae species (flower organs, hindgut typhlosole, in their suprabranchial chambers within three interlamellar ctenidial junctions, relative size weeks of the noted activity. (If this behavior is of adductor muscles, hinge teeth; compare in fact copulatory in function, then this con­ data of Popham, 1939, and Mikkelsen & firms simultaneous hermaphroditism in these Bieler, 1989). species.) Divariscintilla luteocrinita and D. cordi­ Observed animals of these Divariscintilla formis fit well within Divariscintilla, as rede­ species do not respond to changes in light scribed. In fact, these new species actually intensity (e.g. photographic strobes) and did bridge several morphological gaps between not seek darkness when offered "artificial bur­ D. maoria and D. yoyo!D. troglodytes, that is rows" (in the form of black plastic tubes) in the shell notch, posterior shell prolongation, less laboratory. shell internalization, and more numerous pos­ terior tentacles. Divariscintilla octotentaculata does not possess the flower-like organs; how­ DISCUSSION ever, in all other taxonomic characters (hinge, mantle, ctenidia, etc.), it does conform to the Generic Placement redefined genus. The hinge teeth of this spe­ cies, comprised (as in other Divariscintilla The genus Divariscintilla was redescribed species) of only one small cardinal tooth in in a previous part of this study on Lysiosquilla­ each valve, was an important element in de­ associated mollusks (Mikkelsen & Bieler, ciding generic placement. Hinge structure is 1989). Major emphasis was placed on two presently considered taxonomically important features, the presence of flower-like organs at the generic level in Galeommatoidea (P. H. and a bipartite foot with both byssus and bys­ Scott, in litt., October 1990). Most members of sus-adhesive glands, shared between these the superfamily possess more than one car­ species and the type species, D. maoria Pow­ dinal tooth in at least one valve; some show ell, 1932 (the latter described by Judd, 1971 ). distinct lateral teeth as well. The genus Scin- NEW SPECIES OF COMMENSAL GALEOMMATIDAE 17

TABLE 1. Distinguishing characteristics of all described species of Divariscintilla: an expansion of table 1 from Mikkelsen & Bieler (1989).

D. maoria (from Judd, D. D. D. D. 1971) D. yoyo troglodytes octotentaculata luteocrinita cordiformis

Shell: General shape oval elongate- oval roundly roundly oval pointed triangular triangular Ventral indentation present absent absent absent absent present Prolongation posterior anterior anterior posterior posterior posterior Internal sculpture unribbed unribbed radially radially unribbed, with radially ribbed ribbed ribbed internal (marginally) (marginally) (marginally) thickening Length relative to extended mantle length 68% 40% 50% 70% 70% 65% Prodissoconcll length (JJ.m) "small" 360 380 360 390 360 Mean newly-released larval shell length (JJ.m) unknown 132 126 119 unknown 143 Mantle: Color, thickness (not whitish, yellowish, whitish, thin yellowish, whitish, thin given) thick thin thin Extent covering margins entire, entire, anterior and entire, entire, shell only umbonal anterior slit posterior thirds midline midline foramen overlap overlap Papillae very sparse, numerous, numerous, numerous, numerous, small very small small, small, small, small, evenly- longer at evenly- evenly- distributed ventral distributed distributed edge Anterior tentacles 2 pairs 1 pair 2 pairs 2 pairs 3 pairs 6 pairs Posterior tentacles 1 single 1 single 1 single, 1 single, 2 singles, 1 single, 1 pair 2-3 pairs 5 pairs, 8 pairs + 3-6 pairs accessory, + 1 pair club-shaped Defensive appendages 6-8 absent absent absent absent absent present Pedal protractor muscle insertion relative to anterior adductor muscle (not dorsal dorsal ventral ventral ventral given) Flower-like organs: number 3-7 0 (usually 5) Labial palps: Lamellae per palp approx. 9 10-14 14-20 6-8 approx. 8 approx. 7 Ctenidia: smooth pleated pleated smooth smooth smooth? Geographical range: New eastern eastern eastern eastern eastern Zealand Florida Florida Florida Florida Florida

til/ona Finlay, 1927, is the only other genus bers of the latter genus are all attached ecto- known to us in which members have a single commensals on echinoderms, and in addi- cardinal tooth in each valve. However, mem- tion, are distinguished by a highly specialized, 18 MIKKELSEN & BIELER laterally compressed and furrowed foot. Both prefer not to call these structures "lateral of these considerations exclude the new teeth." species described here. In view of the taxo­ According to Popham (1939: 66, text-fig. 6), nomic confusion present in this group, we the hinge of Phlyctaenachlamys lysiosquillina prefer to use an existing genus until a generic has two discrete cardinal teeth in the right revision of this superfamily based on both valve, one cardinal in the left, and an inter­ shell and anatomical characters can be ac­ locking set of posterior laterals. This is dis­ complished. tinctly different from the situation in Divaris­ Coney (1990), in a review of "ventrally cintilla yoyo, D. troglodytes, and D. maoria. notched galeommatid genera," assigned Di­ Ligament morphology in all Divariscintilla variscintilla yoyo and D. troglodytes to the ge­ species (by our definition) consists of an ex­ nus Phlyctaenachlamys, and reinstated ternal amphidetic ligament (inappropriately Divariscintilla as a monotypic genus. His rea­ called "periostracal webbing" at one point in soning revolved around (1) the shell notch, (2) our earlier paper; Mikkelsen & Bieler, 1989: hinge teeth and ligament morphology, (3) 178) supported by a nymph, and an internal shell ultrastructure, (4) mantle tentacles, (5) opisthodetic resilium. The resilium is also ap­ degree of shell coverage by the mantle, and parently present in Phlyctaenachlamys lysios­ (6) ctenidial morphology. We disagree with quillina, but the external ligament was not his taxonomic decisions and address these mentioned by Popham (1939). points as follows: In total, these findings do not agree with (1) Shell notch: The newly described spe­ Coney's (1990: 142) statement that "the cies Divariscintilla cordiformis has an appar­ hinge teeth and ligament are remarkably sim­ ently functionless ventral shell notch very sim­ ilar between the three species [lysiosquillina, ilar to that of the type species D. maoria, and yoyo, troglodytes], but are quite different than agrees well anatomically with the "un­ those of Divariscintilla maoria . ... " notched" species assigned to Divariscintil/a. (3) Shell ultrastructure: This feature was Importantly, the notch does not influence also utilized by Coney (1990) in his discus­ mantle or other soft-part morphology. sion of distinguishing characteristics of Di­ (2) Hinge and ligament: Coney (1990: 131, variscintilla and Phlyctaenachlamys species, 135) offered conflicting statements regarding although he also (1990: 142) admitted that hinge teeth. His table of generic characters the "shell ultrastructure of Phlyctaenach­ and description of Divariscintil/a maoria lamys lysiosquillina is unknown". Studies of stated that there was one cardinal tooth in the the three new species described here (Figs. right valve, whereas his generic description 13, 19-20, 32), as well as a reevaluation of indicated two. Although his scanning photo­ this character in D. yoyo and D. troglodytes micrograph of the right hinge (Coney, 1990: (see Mikkelsen & Bieler, 1989: figs. 11, 15), fig. 11) seemed on first examination to reveal indicate that both the inner and outer non­ two cardinal teeth, comparison with our pho­ cross-lamellar layers may be prismatic rather tomicrographs as well as Coney's subse­ than "homogenous" as previously labelled by quent text indicated that the posteriormost us. Variability in thickness and/or presence of "knob" was actually the resilium, not a sec­ the various layers among individuals and ond cardinal tooth. Coney (1990) upheld the among different locations on a single valve original interpretation by Powell ( 1932) that (e.g. extra internal layer in D. luteocrinita, see the left valve was edentulous, although his above) has also been noted. A more exacting scanning photomicrograph (Coney, 1990: fig. study using more appropriate methodology 12) featured a small structure that may corre­ (e.g. sections rather than fractions, see Taylor spond to Powell's (1932: 67) "minute and et al., 1973) is necessary before differences shapeless vestige" of a left cardinal. Addition­ at this level should be employed in taxonomic ally, Coney (1990) noted a ridge in the left decisions. valve that he called a posterior lateral tooth. (4) Mantle tentacles: Coney (1990: 142) All Divariscintilla species (by our definition) maintained that "number and placement of possess strengthened or thickened hinge mantle tentacles and defensive appendages lines to varying degrees, but without develop­ is strongly similar between P{hlyctaenach­ ment into distinct and/or interlocking lateral lamys] lysiosquillina and those of P. yoyo and teeth/lamellae. As we lack relevant ontoge­ P. troglodytes," noting that none of these spe­ netic data on shell development, we do not cies possess the numerous posterior defen­ wish to infer homology in this instance and sive tentacles seen in Divariscintilla maoria. NEW SPECIES OF COMMENSAL GALEOMMATIDAE 19

The three new species described here in Di­ D. octotentaculata, has a shell that is similarly variscintilla all possess a number of posterior incompletely covered by the mantle. Another tentacles, albeit none "defensive." The two species, D. cordiformis, shows a similar ven­ primary anterior tentacles, also mentioned tral indentation that is likewise apparently specifically by Coney (1990: 142) to combine functionless. These similarities effectively re­ P lysiosquillina, D. yoyo, and D. troglodytes, move most of the dissimilarity between the are in fact also present in Divariscintilla mao­ New Zealand type species and the included ria. eastern Florida species that existed at the (5) Shell coverage: Although there is a dis­ completion of the previous paper (Mikkelsen tinct difference in the degree of shell cover­ & Bieler, 1989). Divariscintilla maoria is the age by the mantle between the type species only species in the genus for which detach­ and Divariscintilla yoyo and D. troglodytes, able defensive papillae have been described. the three newly described species show inter­ mediate conditions. All Divariscintilla species Distribution (by our definition) show at least some degree of shell exposure, thus differing from the con­ The peculiar pattern of geographic distri­ dition in Phlyctaenachlamys lysiosquillina bution of Divariscintilla species, with now ("the shell is completely embedded"; Pop­ five members in the western Atlantic and one ham, 1939: 65). A similar range of variability in New Zealand, is most likely a result of in­ was described for the genus Ephippodonta sufficient sampling of burrow fauna. No eco­ Tate, 1889, by Arakawa (1960: 57), and can logical niche separation between the five also be found in Entovalva Voltzkow, 1890, sympatric species was recognized, leaving in­ sensu lata, wherein the genus Devonia was teresting questions for future research. distinguished by Winckworth (1930: 14) for a species with incomplete shell coverage. Comparison with Other Genera (6) Ctenidial morphology: Coney (1990: 142) noted that the ctenidia in Divariscintilla Divariscintilla was formerly treated as a maoria are smooth, whereas those of Phlyc­ subgenus of Vasconiella Dall, 1899, by Cha­ taenachlamys lysiosquillina, D. yoyo and D. van (1969), apparently on the basis of troglodytes have been described as pleated. notched shells. However, members of V. jef­ However, unlike pleated ( = plicate) gills in freysiana (P. Fischer, 1873), type and sole other bivalve groups (e.g. Pecten; see Rice, species of the genus, possess a deep inden­ 1897), pleating in these species is not based tation only in the comparatively smaller right on structural differences in the filaments valve, and importantly, there are modifica­ (pers. obs.; Popham, 1939: 71 ). Some degree tions in the right mantle and ctenidial tissues of "pleating" caused by contraction in pre­ corresponding to the notch (Cornet, 1982). served specimens has been noted during the This species is also the only other galeomma­ present study. An additional ctenidial charac­ toidean with a published account of a "flower­ ter separates P lysiosquillina and the five Flo­ like organ" (Table 2). Unfortunately, although ridian species of Divariscintilla, in that the lat­ recognizably illustrated by Cornet (1982: fig. ter have interlamellar junctions (unknown for 5), no details on structure or possible function New Zealand D. maoria). were provided for the briefly mentioned Comparative characteristics for all six "rounded tubercle just under the labial palps" known species of Divariscintilla are presented (Cornet, 1982: 39). Vasconiellajeffreysiana is in Table 1. The three new species described probably also commensally associated with a here more closely resemble the type species, mantis shrimp, Lysiosquilla eusebia (Risso, D. maoria (see Judd, 1971: fig. 1), in general 1816) (Table 2; Cornet, 1982). Differences of morphology than do the other species previ­ Vasconiella from Divariscintilla (i.e. two cardi­ ously described during this study (D. yoyo nal teeth in the left valve, lack of a posterior and D. troglodytes, see Mikkelsen & Bieler, foot-extension, ?lack of ctenidial interlamellar 1989: figs. 1, 2). Like D. maoria, the three new junctions) prevent synonymy of the two gen­ species have posteriorly prolonged, relatively era as currently defined, but clearly, their re­ large shells and smooth ctenidia (differences lationship should be investigated further. in percent reduction of the outer demibranch Mention has been made several times as cited in the text may not be reliable, as they above to the relationships of galeommatoide­ were taken from preserved specimens and ans with certain phyla of host invertebrates were affected by contraction). One species, (e.g. echinoderms versus stomatopods). Evi- 20 MIKKELSEN & BIELER

TABLE 2. Galeommatoidean species, hosts, and occurrences of flower-like organs and hanging foot structure (x = presence; - = absence).

Flower- Hanging like foot Host organs structure References( s)

Divariscintilla maoria Powell, Heterosquilla tricarinata X X Judd, 1971 1932 (Claus) D. yoyo Mikkelsen & Bieler, Lysiosquilla scabricauda X X Mikkelsen & Bieler, 1989 (Lamarck) 1989 D. troglodytes Mikkelsen & Lysiosquilla scabricauda X X Mikkelsen & Bieler, Bieler, 1989 (Lamarck) 1989 D. octotentaculata n. sp. Lysiosquilla scabricauda X This study (Lamarck) D. luteocrinita n. sp. Lysiosquilla scabricauda X X This study (Lamarck) D. cordiformis n. sp. Lysiosquilla scabricauda X X This study (Lamarck) Parabornia squillina Lysiosquilla scabricauda X X Boss, 1965a; this study Boss, 1965 (Lamarck) Vasconiella jeffreysiana ?L. eusebia (Risso) X Cornet, 1982 (P. Fischer, 1873) Phlyctaenachlamys L. maculata (Fabricius) X Popham, 1939 lysiosquillina Popham, 1939 Ceratobornia longipes Callianassa major Say or X Jeffreys, 1863; Dall, (Stimpson, 1855) Upogebia affinis (Say) 1899; Norman, 1891; Jenner & McCrary, 1968 C. cema Narchi, 1966 Callianassa major Say X Narchi, 1966

dence suggests that host specificity applies walls (Bruun, 1938) of burrowing holothuri­ mainly to those cases where modifications for ans. locomotion and attachment have occurred. An elongate posterior foot-extension for at­ Most "generalist" species (sensu B. Morton & tachment to a smooth vertical substrate is Scott, 1989; e.g. Mysella bidentata (Montagu, found in three specialist genera: Divariscin­ 1803), associated with a wide variety of inver­ tilla, Phlyctaenachlamys Popham, 1939, and tebrates [Boss, 1965b]) possess a simple foot Ceratobornia Dall, 1899 (Table 2). All species structure consisting of a strong crawling por­ involved are associated with crustaceans that tion (similar to the anterior foot of Divariscin­ produce smooth-walled burrows in sand tilla spp.) ending in a bluntly rounded "heel" (Table 2). Most are believed to live attached from which byssus threads emanate (B. Mor­ to the crustacean burrow walls (Ceratobornia. ton & Scott, 1989: fig. 1 [Lasaea], figs. 9-10 cema may also "temporarily" attach to its host [Pseudopythina]). This is probably the plesio­ (Narchi, 1966); the biology of C. longipes is morphic condition in the superfamily, com­ unknown). Although insufficiently studied in pared to the more derived states seen in Phlyctaenachlamys and Ceratobornia, all some of the host specialists. For example, the species apparently possess the same flattened foot of Scintillona spp. (J. E. Morton, "hanging apparatus" comprised of an anterior 1957) may be a modification for laterally ap­ byssus gland, ventral groove, and posterior plied locomotion among the vertical spines byssus adhesive gland (see Popham, 1939: and papillae of echinoderms to which they at­ fig. 2, P. lysiosquillina, hanging behavior not tach (Dall et al., 1938: 145; Yamamoto & specifically described; Narchi, 1966: figs. 1, 5, Habe, 1974; 6 Foighil & Gibson, 1984: 75}. C. cema; Dall, 1899: pl. 88, figs. 10-11, 13, C. Also, the sucker-like anterior foot of Entovalva longipes). They also all possess similar gen­ ( = Devonia) perrieri (Malard, 1903) (see An­ eral morphologies of the pallial, ctenidial, di­ thony, 1916) allows attachment to the gestive, circulatory, excretory, and nervous smooth, outer body walls and/or inner cloacal systems (C. /ongipes incompletely known). NEW SPECIES OF COMMENSAL GALEOMMATIDAE 21

TABLE 3. Distinguishing characteristics for the three galeommatoidean genera possessing the "hanging foot." See text for included species and sources of data. [L, left; R, right]

Divariscintilla Phlyctaenachlamys Ceratobornia Shell internalization incomplete complete incomplete Hinge: Cardinal teeth 1 R, 1 L 2 R, 1 L 2 R, 2 L Lateral teeth absent 1 posterior, 1 posterior, reduced reduced Retraction into shell yes (1 sp.) no yes no (5 spp.) Adductor muscles subequal posterior reduced subequal Flower-like organs present (5 spp.) absent absent absent (1 sp.) Interlamellar ctenidial present absent absent junctions: Hindgut typhlosole present absent absent Hypobranchial gland present? absent absent Supportive chondroid absent absent present edge in foot

The anatomical differences among the three anteriorly elongated, with the main enlarged genera that presently prevent their synonymy crawling portion located posteriorly. Members are listed in Table 3. Until the importance of of this species are not known to hang; they each of these characters can be reassessed, burrow into sand to avoid illumination, and are it is uncertain whether possession of a apparently free-living. The hinge of R. retifera "hanging foot" reflects convergence or phylo­ (see Bernard, 1975: fig. 1) is distinctly "mon­ genetic relationship, and the three genera are tacutid." Close relationship with the three best treated separately. genera discussed above is unlikely. Another possible difference between Di­ The mantis shrimp Lysiosquilla scabri­ variscintilla on one hand and Phlyctaenach­ cauda also serves as host to Parabornia /amys and Ceratobornia on the other lies in squillina Boss, 1965, a galeommatoidean that the mode of reproduction. Members of Di­ attaches to the inner surface of the abdominal variscintilla for which such data are available sclera of the shrimp (Table 2). Parabornia (D. yoyo, D. troglodytes, D. octotentaculata, squillina has been collected in the region of D. cordiformis) are known to be simultaneous this study (Sebastian Inlet, Peanut Island), hermaphrodites. From literature data, it but has not been collected in burrows contain­ seems that Phlyctaenachlamys lysiosquillina ing Divariscintilla species. Interestingly, the and Ceratobornia cema are forms with sepa­ animal of P. squillina also possesses a single rate sexes (Popham, 1939, p. 80: "specimen "flower-like organ" (pers. obs.), although this sectioned was a male"; and Narchi, 1966, p. was not mentioned in the original species de­ 521: "sectioned specimen was a female"). scription based on preserved material. (Boss, However, while simultaneous hermaphrodit­ 1965a: fig. 3 shows an unexplained five-part ism can be documented from individuals with­ zig-zag outline for the visceral mass below out observations over extended periods of the gills and labial palps.) Its foot (Boss, time, "males" or "females" could belong to 1965a: fig. 3) appears morphologically similar forms with consecutive hermaphroditism. to the "hanging type" described above; a Protandrous and protogynous hermaphrodit­ deep ventral groove ends with an opaque ism have both been reported for the super­ white area at the end of a very short posterior family (summarized by Fox, 1979: tab. 11, as extension (pers. obs.). Boss (1965a: 4) inter­ Leptonacea). preted the white area at the end of the foot as Rhamphidonta Bernard, 1975, represented the byssus gland (as did Judd [1971] for D. by the single species R. retifera (Dall, 1899), maoria, and Narchi [1966] for Ceratobornia also possesses a bipartite foot but one which cema). In view of the byssus adhesive gland is different from that discussed above, both described here and previously (Mikkelsen & morphologically and functionally. According Bieler, 1989), this organ (which was depicted to Bernard ( 1975), the foot of R. retifera is with internal lamellae by Boss, 1965a: fig. 3) 22 MIKKELSEN & BIELER warrants reinvestigation. If this structure is the mone-emitting organs, would be the attraction primary byssus gland, what is the function of of larvae to settlement sites). the ventral groove? (Histological study of the structure of the entire foot, and observations of living animals producing byssus threads ACKNOWLEDGMENTS would resolve this question.) Boss (1965a) placed Parabornia in the Erycinidae (Erycini­ nae), in part, because its hinge has two car­ The following are gratefully acknowledged: dinal teeth in each valve and a central resil­ Dr. Raymond B. Manning (USNM), for bring­ ium. If hinge structure is eventually confirmed ing this interesting fauna to our attention; as a reliable taxonomic character based on William D. ("Woody") Lee (SMSLP), for in­ phylogeny of the group, the "hanging foot" valuable field help; Paul H. Scott (SBMNH), and "flower-like organs" would need to be ex­ for comments on generic placement; Patricia plained as results of evolutionary conver­ A. Linley and Pamela Blades-Eckelbarger gence and/or symplesiomorphies. (both HBOI) for SEM assistance; Tom Smoyer (HBOI) for photographic work; Dr. Kerry B. Clark (Florida Institute of Technol­ Mating Behavior in Bivalves ogy, Melbourne) and John E. Miller (formerly HBOI) for the use of and help with video re­ The observed "mating" behavior (Fig. 33) cording equipment; Paul S. Mikkelsen (for­ between individuals of Divariscintilla octoten­ merly HBOI), for behavioral and developmen­ taculata as well as of D. yoyo is of special tal notes and the photograph in Fig. 1; Chris interest. Mating behavior has not been con­ Bauman (Vero Beach, Florida) for the illustra­ firmed for bivalves (Mackie, 1984: 362). tion in Fig. 33; Paul H. Scott (SBMNH), Dr. Mackie (1984: 363) summarized the reported Kenneth J. Boss (MCZ), and two anonymous cases of associations between females and reviewers for valuable comments on the dwarf males in bivalves and concluded that manuscript. those interactions would qualify as mating be­ This research was supported in part by the havior if it can be shown that the associations Smithsonian Marine Station at Link Port; the are confined to a breeding period. cooperation of Dr. Mary E. Rice and her staff True copulatory behavior is absent in bi­ is gratefully acknowledged. Funding for this valves because they lack copulatory organs. project was derived in part from a National However, several authors (Clapp, 1951: 7; Capital Shell Club scholarship toP. M., and a Townsley et al., 1966: 49) have observed NATO Postdoctoral Research Fellowship at male teredinids (Bankia spp.) inserting their SMSLP to R. B. This is Harbor Branch exhalent siphons into the inhalent siphons of Oceanographic Institution Contribution no. females during sperm release. Purchon 862 and Smithsonian Marine Station Contri­ (1977: 295), and subsequently Mackie (1984: bution no. 273. 362), interpreted this as the use of an intromit­ tant organ, the development of which would be of "great survival value to species ... living LITERATURE CITED in isolated pieces of drift wood (Purchon, 1977: 295). Similarly, quasi-copulatory be­ ANTHONY, R., 1916, Contribution a l'etude de havior in Divariscintil/a would be advanta­ I'Entovalva (Synapticola) perrieri Malard, mol­ geous for these small bivalves with limited ga­ lusque acephale commensal des synaptes. Ar­ mete production, living in restricted, relatively chives de Zoologie Experimentale et Generale, isolated populations within the burrows of 55: 375-391, pis. 6-7. their hosts. Selective mating in burrows that ARAKAWA, K. Y., 1960, Ecological observations contain several other congeneric species on an aberrant lamellibranch, Ephippodonta mu­ would guarantee successful fertilization and rakamii Kuroda. Venus, Japanese Journal of Ma­ make conservative use of male gametes. In lacology, 21 (1 ): 50-60, pis. 7-8. BERNARD, F. R., 1975, Rhamphidonta gen. n. our previous discussion of flower-like organs, from the northeastern Pacific (Bivalvia, Leptona­ now known from five species of Divariscintilla, cea). Journal de Conchyliologie, 112(3-4): 105- we (Mikkelsen & Bieler, 1989: 191) specu­ 115. lated that these organs might emit a phero­ BIELER, R. & P.M. MIKKELSEN, 1988, Anatomy mone for attracting reproductive partners and reproductive biology of two western Atlantic (another possibility, if they are indeed phero- species of Vitrinellidae, with a case of protan- ..

NEW SPECIES OF COMMENSAL GALEOMMATIDAE 23

drous hermaphroditism in the Rissoacea. The tropod" bivalve, commensal on Squilla empusa Nautilus, 102(1 ): 1-29. (Abstract). Annual Report for 1968, American BOSS, K. J., 1965a, A new mollusk (Bivalvia, Ery­ Malacological Union: pp. 20-21 . cinidae) commensal on the stomatopod crusta­ JUDD, W., 1971, The structure and habits of Di­ cean Lysiosquilla. American Museum Novitates, variscintilla maoria Powell (Bivalvia: Galeomma­ no. 2215: 11 pp. tidae). Proceedings of the Malacological Society BOSS, K.J., 1965b, Symbiotic erycinacean bi­ of London, 39: 343-354. valves. Malacologia, 3(2): 183-195. MACKIE, G. L., 1984, Bivalves. Pp. 351-418, BRUUN, A. F., 1938, A new entocommensalistic in: A. S. TOMPA, et al., The Mollusca, Vol. 7, Re­ bivalve, Entovalva major n.sp., from the Red production. Academic Press, Orlando, xix + 486 Sea. Videnskabelige Meddelelser fra Dansk pp. naturhistorisk Forening i Kobenhavn, 102: 163- MIKKELSEN, P. M. & R. BIELER, 1989, Biology 167. and comparative anatomy of Divariscintilla yoyo CHAVAN, A., 1969, Superfamily Leptonacea Gray, and D. troglodytes, two new species of Galeom­ 1847. Pp 518-537, in: R. C. MOORE, ed., matidae (Bivalvia) from stomatopod burrows in Treatise on Invertebrate Paleontology, Part N. eastern Florida. Malacologia, 31(1): 1-21. Mollusca 6. Bivalvia 2. Geological Society of MORTON, B., 1973a, The biology and functional America (Boulder, Colorado) & University of Kan­ morphology of Galeomma (Paralepida) takii (Bi­ sas (Lawrence), ii + N491-N952 pp. valvia: Leptonacea). Journal of Zoology, 169(2): CLAPP, W. F., 1951, Observations on living Tere­ 133-150. dinidae. Fourth Progress Report on Marine Borer MORTON, B., 1973b, Some factors affecting the Activity in Test Boards Operated during 1950. location of Arthritica crassiformis (Bivalvia: Lep­ Report no. 7550, W. F. Clapp Laboratories, Inc., tonacea) commensal upon Anchomasa simi/is Duxbury, Massachusetts, 9 pp. (Bivalvia: Pholadidae). Journal of Zoology, 170: CONEY, C. C., 1990, Bellascintilla parmaleeana 463-473. new genus and species from the tropical eastern MORTON, B., 1975, Dymantic display in Ga­ Pacific, with a review of the other, ventrally /eomma polita Deshayes (Bivalvia: Leptonacea). notched galeommatid genera (Bivalvia: Galeom­ Journal of Conchology, 28: 365-369. matacea). The Nautilus, 104(4): 130-144. MORTON, B., 1976, Secondary brooding of tem­ CORNET, M., 1982, Anatomical description of Vas­ porary dwarf males in Ephippodonta (Ephipp­ coniellajeffreysiana (P. Fischer, 1873) (Mollusca, odontina) oedipus sp. nov. (Bivalvia: Leptona­ Bivalvia, Leptonacea). Journal of Molluscan cea). Journal of Conchology, 29: 31-39. Studies, 48(1 ): 36-43. MORTON, B. & P. H. SCOTT, 1989, The Hong DALL, W. H., 1899, Synopsis of the Recent and Kong Galeommatacea (Mollusca: Bivalvia) and Tertiary Leptonacea of North America and the their hosts, with descriptions of new species. West Indies. Proceedings of the United States Asian Marine Biology, 6: 129-160. National Museum, 21 (1177): 873-897, pis. 87-88. MORTON, J. E., 1957, The habits of Scintillona ze­ DALL, W. H., P. BARTSCH & H. A. REHDER, landica (Odhner) 1924 (Lamellibranchia: Ga­ 1938, A manual of the Recent and fossil marine leommatidae). Proceedings of the Malacological pelecypod mollusks of the Hawaiian Islands. Ber­ Society of London, 32(5): 185-188. nice P. Bishop Museum Bulletin, 153: iv + 233 NARCHI, W., 1966, The functional morphology of pp., 58 pis. Ceratobornia cema, new species of the Erycina­ ECKELBARGER, K. J., R. BIELER & P. M. MIK­ cea (Mollusca, Eulamellibranchiata). Anais da KELSEN, 1990, Ultrastructure of sperm develop­ Academia Brasileira de Ciencias, 38(3-4): 513- ment and mature sperm morphology in three 524. species of commensal bivalves (Mollusca: Ga­ NORMAN, A. M., 1891, Lepton squamosum (Mon­ leommatoidea). Journal of Morphology, 205: 63- tagu), a commensal. Annals and Magazine of 75. Natural History, (6) 7(39): 276-278. FOX, T. H., 1979, Reproductive adaptations and life 6 FOIGHIL, D. & A. GIBSON, 1984, The morphol­ histories of the commensa/leptonacean bivalves. ogy, reproduction and ecology of the commensal Ph.D. dissertation, University of North Carolina, bivalve Scintillona bellerophon spec. nov. (Ga­ Chapel Hill, ix + 207 pp. leommatacea). The Veliger, 27(1 ): 72-80. HUMASON, G. L., 1962, Animal Tissue Tech­ POPHAM, M. L., 1939, On Ph/yctaenachlamys niques. W. H. Freeman & Co., San Francisco & lysiosquillina gen. and sp. nov., a lamellibranch London, xv + 468 pp. commensal in the burrows of Lysiosquilla macu­ JEFFREYS, J. G., 1863, British Conchology, or an lata. British Museum (Natural History), Great Bar­ account of the Mollusca which now inhabit the rier Reef Expedition 1928-29, Scientific Reports, British Isles and the surrounding seas. Vol. II. 6(2): 549-587. Marine Shells, comprising the Brachiopoda, and PURCHON, R. D., 1977, The Biology of the Mol­ Conch ifera from the family of Anomiidae to that of lusca, 2nd ed. Pergamon Press, Oxford, xxv + Mactridae. London, John Van Voorst, xiv + 465 560 pp. pp., 8 pis. RICE, E. L., 1897, Die systematische Verwert­ JENNER, C. E. & A. B. McCRARY, 1968, A "gas- barkeit der Kiemen bei den Lamellibranchiaten. 24 MIKKELSEN & BIELER

Jenaische Zeitschrift fur Naturwissenschaft, 31 VACCA, L. L., 1985, Laboratory manual of his­ (N.F. 24): 29-89, pis. 3-4. tochemistry. Raven Press, New York, xvii + 578 TAYLOR, J.D., W. J. KENNEDY & A. HALL, 1973, pp. The shell structure and mineralogy of the Bi­ WINCKWORTH, A., 1930, Notes on nomenclature. valvia. II. Lucinacea-Ciavagellacea, conclu­ Proceedings of the Malacological Society of Lon­ sions. Bulletin of the British Museum (Natural don, 19(1): 14-16. History), 22(9): 253-294, pis. 1-15. YAMAMOTO, T. & T. HABE, 1974, Scintillona stig­ TOWNSLEY, P. M., A. A. RICHY & P. C. TRUS­ matica (Pilsbry) new to Japan. Venus, Japanese SELL, 1966, The laboratory rearing of the ship­ Journal of Malacology, 33(3): 116. worm, Bankia setacea (Tryon). Proceedings of the National Shellfisheries Association, 56: 49-52. Revised Ms accepted 1 August 1991