Keijcyoidea infralittoralis, Tsukagoshi, Okada & Horne, 2006

Okada, Reiko, Tsukagoshi, Akira, Smith, Robin J. & Horne, David J., 2008, The ontogeny of the platycopid Keijcyoidea infralittoralis (Ostracoda: Podocopa), Zoological Journal of the Linnean Society 153 (2), pp. 213-237 : 214-231

ONTOGENY OF KEIJCYOIDEA INFRALITTORALIS

The eight instars younger than adults are described here, with attention to carapace features, limbs, and other ‘soft’ parts; the ninth (i.e. adult) instar was fully described by Tsukagoshi et al. (2006), but is again described briefly here to facilitate comparisons with the juvenile instars. The carapace is well calcified in all instars, even in the A-8 instar.

FIRST INSTAR (A-8) ( FIGS 1A , 2 , 3A , 4 )

Right valve length, 230–250 Mm; height, 170–180 Mm. Carapace, subtrapezoidal in lateral view; left valve anterior margin, evenly convex; dorsal margin, gently curved; ventral margin, relatively short and almost straight; posterior margin, composed of two almost straight, oblique sections, meeting at a rounded corner at approximately mid-height. Posteroventral quarter: swollen. Marginal ridge: weakly developed anteriorly. Some fossae along anteroventral margin; puncta distributed all over except for ventral area.

Body: with four paired limbs (antennula, antenna, mandibula, and maxillula) and a furca (paired furcal rami). Antennula, uniramous, with five articulated podomeres: first podomere, large and trapezoidal, with numerous setulae along anterior distal margin; second podomere, large and triangular, with one short seta on posterior distal corner, and numerous setulae along anterior margin; third podomere, middle-sized, triangular/trapezoidal, with one stout seta on middle of anterior margin; fourth podomere, middle-sized, trapezoidal, with one long stout seta on both anterior and posterior distal ends; fifth podomere, small, irregular trapezoidal distally, with one very short seta and three long stout setae.

Antenna: biramous, with exopodite and endopodite consisting of one and three podomeres, respectively; large, nondivided protopodite, with one very long, stout plumose seta on posterior proximal edge, and two long, stout, hirsute setae on posterior distal corner. Podomere of exopodite: trapezoidal, distally with two long and one middle-length annulated setae. First podomere of endopodite: wide proximally, tapering to quadrate distal portion, and anterior proximal margin connected to proximal end of exopodite, with one long annulated seta bearing setulae, and one short spatulate seta on anterior and posterior distal end, respectively; second podomere, subsquare, with one short spatulate seta in middle of posterior margin, and one stout hirsute seta at posterior distal end; third podomere, small, irregular trapezoidal, with one short spatulate seta in middle of posterior margin, and one long annulated seta, one short hooklike seta, one short smooth seta, and one stout hirsute seta on distal end.

Mandibula consisting of four articulated podomeres: second to third podomeres, wider than long; first podomere, subtrapezoidal without seta; second podomere, bearing one very long stout plumose seta, one short smooth seta, and one short stout seta on posterior side; third podomere, bearing three setae and one very long stout plumose seta on posterior side; fourth podomere with one short smooth seta, one plumose seta, and one long smooth seta in middle of posterior margin, and one very short smooth seta, two short, smooth setae, and one stout, smooth seta on distal end.

Length (µ m)

Maxillula: consisting of lobe with numerous setulae along posterior margin and one very long, curved, smooth seta with widened, proximal portion protruding from middle of posterior margin.

Furcal ramus: consisting of triangular anlage, with setulae along posterior margin.

Caudal part of body: elongate, tapering distally and covered with numerous setulae.

SECOND INSTAR (A-7) ( FIGS 1B , 2 , 3B , 5 )

Right valve length, 270–280 Mm; height, 190–200 Mm. Carapace outline similar to but more elongate than A-8. Swollen marginal ridge weakly developed anteriorly and posteriorly. Dorsomedian sulcus weakly developed. Other features are similar to A-8.

Body: with four paired limbs (antennula, antenna, mandibula, and maxillula) and furca. Antennula uniramous, with five articulated podomeres: first podomere, large, irregular trapezoid, with two bunches of setulae along anterior margin; second podomere, large trapezoid, with one short smooth seta on posterior distal corner, and numerous setulae along anterior margin; third podomere, middle-sized, triangular/trapezoidal, with one stout hirsute seta on middle of anterior margin; fourth podomere, middlesized, trapezoidal, with one long stout seta on both anterior and posterior distal ends, respectively; fifth podomere, small and trapezoidal, with one smooth, very short seta, one long simple seta, one spatulate seta, and one long, stout, hook-shaped seta on distal end.

Antenna: biramous, with exopodite and endopodite consisting of one and three podomeres, respectively. Large trapezoidal coxa: with one very long and stout plumose seta on posterior proximal area; large triangular basis, with three long stout, hirsute setae on posterior distal corner. Podomere of exopodite: trapezoidal, with three long, annulated setae, and one incipient seta on distal end. First podomere of endopodite, trapezoidal, with one long annulated seta and one incipient seta on anterior distal end, and one spatulate seta on posterior distal corner; second podomere, subtrapezoidal, with one incipient seta on anterior distal end and one stout seta on posterior distal end; third podomere, small, trapezoidal/ triangular, distally with one long, annulated seta, one stout bifurcating seta, one short spatulate seta, and one stout, hirsute seta.

Mandibula consisting of four articulated podomeres: first podomere (coxa), trapezoidal, with one short smooth seta on posterior distal corner; second podomere (basis), trapezoidal, bearing exopodite, with two very long, stout, plumose and one long, smooth setae, and with four stout, smooth setae along posterior margin; anterior distal end of podomere with small swell, supporting one bunch of setulae. Third podomere (first endopodite podomere), trapezoidal/triangular, with two stout, smooth setae on posterior margin and one smooth seta on distal end; fourth podomere (second endopodite podomere), small, bearing one very short, smooth seta, one short, stout seta, one stout, plumose seta, and one smooth seta on distal end.

Maxillula: lobate, without clear segmentation; with numerous setulae along posterior margin, and one hirsute, spatulate seta at posterior distal area.

Furcal ramus: trapezoidal, with one very long seta, one middle-length seta, and one short, stout, smooth seta on distal end.

Caudal part of body: developing several comb-like rows of setulae and stout hirsute seta on distal end.

THIRD INSTAR (A-6) ( FIGS 1C , 2 , 3C , 6 )

Right valve length, 310–320 Mm; height, 200–210 Mm. Carapace similar in shape and ornament to previous instar but with more rounded posterior margin. Swollen marginal ridge: continuous except for midventral area.

Body: with five paired limbs (antennula, antenna, mandibula, maxillula, and fifth limbs) and furca. Antennula uniramous, with five articulated podomeres: first podomere, large and irregular polygon, bearing one short stout plumose seta, with one bunch of setulae at anterior distal corner; second podomere, large and trapezoidal, with one short annulated seta on posterior distal corner and numerous setulae along anterior margin; third podomere, middle-sized and triangular, with one stout, hirsute seta and one short, annulated seta on anterior and posterior distal corners, respectively; fourth podomere, small and trapezoidal, with one long, stout seta on both anterior and posterior distal ends, respectively; fifth podomere, small and irregular trapezoidal, distally with one smooth, very short seta, one long, smooth seta, one middle-length seta, and one long, stout, hook-like seta.

Antenna: biramous, with exopodite and endopodite consisting of one and three podomeres, respectively; large trapezoidal coxa without seta; large triangular basis, with two long, stout, hirsute setae on posterior distal corner. Podomere of exopodite: almost square, with five long, annulated setae and one incipient seta on distal end. First podomere of endopodite, trapezoidal, with one short, spatulate seta in middle of posterior margin, one long, annulated seta on distal end, one long, annulated and one incipient setae on anterior distal corner; second podomere, subtrapezoidal, broadening distally, with one short, spatulate seta on ledge in middle of posterior margin, one long annulated and one incipient setae on anterior distal corner, and one stout, hirsute seta on posterior distal end; third podomere, small and irregular, with one short spatulate seta on ledge in middle of posterior margin, and distally with one long, annulated seta, one stout, bifurcating seta, and one long, stout, hirsute seta.

Mandibula: consisting of four podomeres, second to fourth podomeres fused. First podomere (coxa), trapezoidal, with one endite bearing fine teeth on posterior distal end; second podomere (basis), elongate, bearing exopodite with two stout plumose setae proximally on anterior margin, four long plumose setae along posterior margin, and one large triangular lateral lobe distally; third podomere (first endopodite podomere), with two long plumose setae along posterior margin; fourth podomere (second endopodite podomere), with two long, one middle-length, and one short, smooth setae.

Maxillula: consisting of basis, exopodite, and endopodite; basis subsemicircular, bearing three separate endites, each with between one and three short setae distally; endopodite (palp) consisting of elongate lobe, with numerous fine setulae along distal margin; exopodite consisting of large branchial plate with about 15 flattened plumose long setae, and one swollen seta (innermost).

Fifth limb: large, lobate, with numerous setulae along posterior margin.

Furcal ramus: trapezoidal, with one very long, smooth seta, one middle-length hirsute seta, and three short, stout, hirsute setae on distal end.

Caudal part of body: with several comb-like rows of setulae, and stout, hirsute seta on distal end.

FOURTH INSTAR (A-5) ( FIGS 1D , 2 , 3D , 7 )

Right valve length, 340–360 Mm; height, 220–230 Mm. Carapace: similar in shape and ornament to previous instar, but posteroventral quarter less swollen.

Body: with five paired limbs (antennula, antenna, mandibula, maxillula, fifth limb) and furca. Antennula uniramous, with five articulated podomeres: first podomere, large and irregular polygon, bearing one short, stout, plumose seta, and one bunch of setulae at anterior distal corner; second podomere, large and subtrapezoidal, with one incipient seta on anterior distal corner, one short, annulated seta on posterior distal corner, and numerous setulae along anterior margin; third podomere, middle-sized and triangular, with one stout, hirsute seta and one annulated seta at anterior and posterior distal corners, respectively; fourth podomere, small and trapezoidal, with one long, hirsute seta on anterior end, and one long, hirsute and one short, spatulate setae on posterior distal end; fifth podomere, small and irregular trapezoidal, distally with one hook-like seta, one very short, smooth seta, one stout, claw-like seta, and one subapical, straight, smooth seta.

Antenna: biramous, with exopodite and endopodite consisting of two and four podomeres, respectively. Large trapezoidal coxa: without setae. Large triangular basis: with two long, stout, hirsute setae and one incipient seta on posterior distal corner, and with numerous setulae along anterior margin. First podomere of exopodite almost square, with three long annulated setae on posterior distal end, and numerous setulae along anterior margin; second podomere, small, wider than long, with two long setae, one middle-length, annulated seta, and one incipient seta on distal end. First podomere of endopodite, trapezoidal, broadening distally, with two short spatulate setae on proximal part of posterior margin, and distally with one long, annulated seta, one incipient seta, two smooth setae, and one hirsute seta on distal end; second podomere, irregular trapezoidal, with one short, spatulate seta on ledge in proximal part of posterior margin, one incipient seta on ledge of distal part of anterior margin, one stout, hirsute seta at posterior distal corner, and one smooth and one annulated setae on anterior distal corner; third podomere, small and irregular, with one smooth and one stout, bifurcating setae on distal end; fourth podomere, very small and irregular, with one spatulate seta and one stout, hirsute seta on posterior proximal and distal ends, respectively.

Mandibula consisting of four podomeres, with second to fourth podomeres fused: first podomere (coxa), trapezoidal, with one endite bearing fine teeth on posterior distal end, second podomere (basis) elongate, bearing exopodite, with one long and three short, stout, plumose setae proximally on anterior margin; comb or screen of about 20 long, flattened, plumose setae laterally; third podomere (first endopodite podomere), somewhat elongate, with one short, stout, smooth seta on posterior proximal end, one long, plumose seta at posterior distal end, and one short, stout, smooth seta on distal end; fourth podomere (second endopodite podomere), small, with one somewhat long, curved seta and two straight smooth setae on distal end.

Maxillula: consisting of basis, exopodite, endopodite, and three endites. Basis: irregular, with three separate endites, each bearing between one and three short setae distally. Endopodite (palp): elongate lobe, with two short, stout setae on distal end, and numerous fine setulae along distal margin. Exopodite: consisting of large branchial plate with about 18 flattened, plumose, long setae and some short setae proximal to basis.

Fifth limb: consisting of large, rounded lobe with one long plumose seta and numerous setulae along posterior margin.

Furcal ramus: trapezoidal, distally with one very long, smooth seta, two middle-length hirsute setae, two short, stout, hirsute setae, and one incipient seta.

Trunk: with at least five indistinct segments, including caudal part of body. Caudal part of body: developing several comb-like rows of setulae, and one stout hirsute seta and one incipient seta on distal end; next most-distal segment with one short seta.

FIFTH INSTAR (A-4) ( FIGS 1E , 2 , 3E , 8 )

Right valve length, 390–410 Mm; height, 250–260 Mm. Carapace: similar in shape and ornament to previous instar, except for a more truncated posterior margin and a less swollen posteroventral quarter.

Body: with five paired limbs (antennula, antenna, mandibula, maxillula, and fifth limbs), anlagen of sixth limbs, and furca. Antennula uniramous, with six articulated podomeres: first podomere, large and irregular polygon, bearing two stout, plumose setae in middle of anterior margin; second podomere, large and trapezoidal, with one incipient and one stout, hirsute setae on anterior distal corner, one short, smooth seta on posterior distal corner, and numerous setulae along anterior margin; third podomere, middle-sized and triangular, without setae; fourth podomere, rectanglar, wider than long, bearing one long seta on each anterior and posterior distal corner; fifth podomere, square, with one long, hirsute seta and one incipient seta on anterior distal end, and one long, smooth seta and one short, spatulate seta on posterior distal end; sixth podomere, small and irregular trapezoidal, with three middle-length, smooth setae on ledge in middle of anterior margin, and one stout, claw-like seta on distal end.

Antenna: biramous, with exopodite and endopodite consisting of two and three podomeres, respectively. Large, trapezoidal coxa: with one smooth seta on each anterior proximal and anterior distal margin. Large, triangular basis: with one very long and two long, stout, plumose setae on posterior distal corner, and numerous setulae along anterior margin. First podomere of exopodite, trapezoidal, with four very long annulated setae on posterior distal end, and numerous setulae along anterior distal margin; second podomere, small and rectangular, distally with two very long, one middle-length, and one short annulated setae. First endopodite podomere, trapezoidal, broadening distally, and proximal part elongating to proximal part of first podomere of exopodite, with two short spatulate seta in middle of posterior margin, five hirsute, one smooth, and two incipient setae on distal end; second podomere, irregular square, with two short, spatulate setae in posterior proximal margin, one short, smooth seta on ledge in middle of posterior margin, three long, annulated setae and one stout hook-like seta on anterior distal corner, and one stout, hirsute seta on posterior distal corner; third podomere, small and trapezoidal, with one stout, hirsute seta and one smooth seta on posterior distal corner, and one long, annulated seta and one stout bifurcating seta on distal end.

Mandibula: consisting of coxa, basis and endopodite with two podomeres. Coxa: bearing one large endite, with numerous fine teeth on distal end. Basis: elongate, bearing one smooth seta on posterior proximal margin and exopodite with one middle-length and three short, stout, plumose setae proximally on anterior margin; comb or screen of about 20 long, flattened, plumose setae laterally, with one incipient seta and one smooth seta on distal end. First endopodite podomere, somewhat elongate, with one short seta, and one middle-length smooth seta, on posterior distal end; second podomere very small, with three smooth setae of unequal length on distal end.

Maxillula: consisting of basis, exopodite, and endopodite. Basis, irregular, with three separate endites: innermost two each bearing seven setae, outermost bearing three setae. Endopodite (palp): elongate, proximally with two nodes, each with one short seta at top; distally with three short setae and numerous setulae along ventrodistal margin, and comb or screen of about 20 long, flattened, plumose setae laterally. Exopodite: consisting of large branchial plate with over 20 flattened, plumose, long setae.

Fifth limb consisting of basis and exopodite (endopodite absent): basis terminating distally in a rounded endite, with numerous setulae along distal margin; exopodite consisting of branchial plate bearing more than ten flattened, plumose setae.

Anlage of thin small-lobed sixth limb.

Furcal ramus: trapezoidal, rounding distally, with one long smooth seta, seven plumose setae of unequal length, and one incipient seta along distal margin.

Trunk and caudal parts of body with seven body segments: caudal (terminal) part with several comblike rows of setulae and two short, stout, hirsute setae on distal end; three next most-distal segments with one short seta each.

SIXTH INSTAR (A-3) ( FIGS 1F , 2 , 3F , 9 )

Male right valve length, 440–470 Mm; height, 270– 280 Mm. Female right valve length, 460–470 Mm; height 290 Mm. Carapace similar in shape to previous instar, but more quadrate, and with weak development of a curved, swollen ventrolateral longitudinal ridge joined to a pair of short, swollen, radial ridges posteriorly. Dorsomedian sulcus: clearly developed. Fossae and puncta: deeper than those of smaller instars. Sexual dimorphism: in size, with females larger than males.

Body: with six paired limbs (antennula, antenna, mandibula, maxillula, fifth limbs, and sixth limbs) and furca, plus anlagen of seventh limbs and copulatory limbs. Antennula uniramous, with six articulated podomeres: first podomere, large and irregular polygon, bearing three stout, plumose setae on anterior dorsal margin, and one plumose seta at ventroproximal corner; second podomere, large and triangular, with two hirsute setae on anterior distal corner, one short smooth seta on posterior distal corner, and several patches of numerous setulae along anterior margin; third podomere, middle-sized and triangular, with one smooth seta on posterior distal corner; fourth podomere, rectangular and wider than long, anterior and posterior distal corners each bearing one pair of long and short seta; fifth podomere, middle-sized, irregular square, with one incipient and three stout setae on anterior margin, and 1 smooth and 1 short spatulate setae on posterior distal end; sixth podomere, small and irregular trapezoidal, with two middle-length, hirsute setae, one middle-length, smooth seta, and one stout, hook-like seta at distal end, and one very short, smooth setae on ledge in middle of anterior margin.

Antenna: biramous, with exopodite and endopodite consisting of two and three podomeres, respectively. Large semielliptical coxa: with midpoint of dorsal margin and anterior distal end each with one smooth seta. Large triangular basis: with one very long, one long, and one middle-length, stout, hirsute setae on posterior distal corner, and numerous setulae along anterior margin. First podomere of exopodite, trapezoidal, with four very long, annulated setae on posterior distal end, and numerous setulae along anterior distal margin; second podomere, small and rounded distally, with two very long, four long, one middle-length, two short, annulated, and one incipient setae on distal end. First podomere of endopodite: trapezoidal, broadening distally, and proximal part elongating to proximal part of first podomere of exopodite, with one short spatulate seta on posterior proximal end, two long spatulate, one incipient, four short, smooth, one middle-length, hirsute, and two long, stout, hirsute setae, in order, anterior to posterior on distal end, with a row of setulae; second podomere, irregular polygon, with three short, spatulate setae on posterior proximal margin, three long, annulated, two incipient, and one large, hook-like setae on ledge in middle anterior margin, and one stout, hirsute seta on posterior distal corner; third podomere, small and trapezoidal, with one short, spatulate seta on ledge in posterior middle margin, and one long, annulated, one stout, bifurcating, and one stout, hirsute setae on distal end.

Mandibula consisting of four podomeres: coxa, basis, and two endopodite podomeres, the first of which is fused with the basis. Coxa: bearing one large endite with numerous fine teeth on distal end. Basis: elongate, bearing one smooth seta on posterior proximal margin, and exopodite consisting of six short, stout, plumose setae proximally on anterior margin; comb or screen of more than 20 long, flattened, plumose setae, laterally. First endopodite podomere with one long seta proximally, and one short, smooth seta distally; second podomere very small, with two long and one short, smooth setae on distal end.

Maxillula: consisting of basis, exopodite, and endopodite. Basis: small and irregular, bearing three separate endites, each bearing three short setae. Endopodite (palp): elongate, with one blunt node terminating with one seta and two well-developed nodes, each terminating with two short setae; distally bearing three unequal-length, short setae, and with one short, plumose seta on dorsodistal margin, and with numerous fine setulae along distal and dorsoproximal margins; comb/screen of more than 20 long, flattened, plumose setae along lateral side. Exopodite consisting of large branchial plate with about 25 flattened, plumose, long setae.

Fifth limb: consisting of basis, exopodite, and rudimentary endopodite. Basis terminating distally in elongate, rounded endite bearing distally one long and two very short smooth setae, more proximally, one long and one very short smooth setae, and with setulae along its dorsodistal margin. Endopodite: consisting of short, rounded lobe bearing one long, plumose seta and three very short, smooth setae distally. Exopodite: consisting of branchial plate with 15 flattened, plumose, long setae.

Sixth limb: lobed, with one short, smooth seta on anterior and posterior margins, respectively, and with numerous setulae along distal end.

Anlage of seventh limb: small, elongate, lobed, with rounded end. Anlage of copulatory organ (indeterminate, male or female): elongate, wider and longer than seventh limb anlage.

Furcal ramus: with one long, smooth seta, and seven unequal-length plumose setae along rounded distal margin.

Trunk and caudal parts of body bearing fewer than ten body segments (proximal ones indistinct), with comb-like rows of setulae distally; caudal (terminal) segment with two short, stout, hirsute setae on distal end; next five distalmost segments each with one hirsute or incipient seta.

SEVENTH INSTAR (A-2) ( FIGS 1G , 2 , 3G , 10 )

Male right valve length, 510 Mm; height, 310 Mm. Female right valve length, 530–570 Mm; height, 320– 340 Mm. Carapace similar in shape and ornament to previous instar, but dorsal margin (= hingeline) weakly sinuous. Sexual dimorphism: in size, with females larger than males.

Body: with six paired limbs (antennula, antenna, mandibula, maxillula, fifth limbs, and sixth limbs) and furca, plus anlagen of seventh limbs and copulatory limbs. Antennula uniramous, consisting of seven articulated podomeres: first podomere, large and trapezoidal, bearing four stout, plumose setae, one patch of setulae on dorsal margin, and one plumose seta in ventroproximal area; second podomere, large and triangular, with two hirsute and one incipient setae on anterior distal corner, one short, smooth seta on posterior distal corner, and some patches of numerous setulae along anterior margin; third podomere, middle-sized and triangular, with one smooth seta on posterior distal corner; fourth podomere, polygonal, wider than long, tapering distal-proximally, bearing two unequal-length, hirsute setae on anterior distal margin, and two unequal-length, annulated setae on ledge in middle of posterior margin; fifth podomere, trapezoidal, wider than long, tapering distalproximally, with two unequal-length, smooth setae, and two incipient setae on anterior distal margin; sixth podomere, middle-sized, irregular and trapezoidal, with one incipient and two stout setae on anterior margin, and one smooth and one short, spatulate setae on posterior distal end; seventh podomere, small, elongate, irregular trapezoidal, with three smooth setae on ledge in middle of anterior margin, and one large, stout, hook-like seta on distal end.

Antenna: biramous, with exopodite and endopodite consisting of two and three podomeres, respectively. Large elongated coxa, with one smooth seta in middle of dorsal margin and anterior distal end, respectively. Large triangular basis: with two very long and one middle-length, stout, hirsute setae on posterior distal corner, and numerous setulae along anterior margin. First podomere of exopodite: trapezoidal, with five very long, annulated setae and one long, smooth seta on posterior distal margin, and numerous setulae along anterior distal margin; second podomere, small and rounded distally, with three very long, one long, two middle-length, two short, annulated, and one incipient setae on distal end. First podomere of endopodite: trapezoidal, broadening distally, and proximal part elongating to proximal part of first podomere of exopodite, with three short, spatulate setae on ledge in posterior proximal margin, three long, smooth setae in anterior to middle distal margin, one short, one middle, and two long, stout, hirsute setae on posterior distal end, with marginal setulae; second podomere, irregular polygon, with one short, spatulate seta on posterior proximal margin, two short, smooth setae on ledge in middle proximal posterior margin, two very long, annulated setae on ledge in middle of anterior margin, three long, annulated and one long, stout, hook-like setae on anterior distal end, and one stout, hirsute seta on posterior distal end; third podomere, small and trapezoidal, with one long, annulated, one stout, bifurcating, and one stout, hirsute setae on distal end.

Mandibula consisting of four podomeres: coxa, basis, and two endopodite podomeres, the first of which is fused with the basis. Coxa: bearing one large endite, with numerous fine teeth on distal end. Basis: elongate, bearing one smooth seta on posterior proximal margin, and exopodite consisting of one long and five short, stout plumose setae, proximally on anterior margin; inner edge with comb/screen of about 27 long, flattened, plumose setae laterally; one short, smooth seta on distal end. First endopodite podomere, with one blunt, short seta on proximal end, and one middle-length and one short, smooth setae on distal end; second podomere, very small with one long and one middle-length, smooth setae on distal end.

Maxillula: consisting of basis, exopodite, and endopodite. Basis: small and irregular, with three separate endites, each bearing some short setae. Endopodite (palp): elongate, bearing three blunt nodes with between two and four short setae on top of each; one short, plumose seta on dorsodistal margin, three unequal-length, short setae on distal end, and numerous setulae along distal margin; comb/screen of more than 20 long, flattened, plumose setae. Exopodite consisting of large branchial plate with about 28 flattened, plumose, long setae.

Fifth limb: consisting of basis and exopodite. Basis: with one middle-length, smooth setae on lateral side; distally, a blunt, elongate endite with three very short setae in middle of lateral side, one plumose seta (possibly representing a reduced endopodite) on ventrodistal margin, three very short setae on ventrodistal end, and numerous setulae along dorsodistal margin. Exopodite consisting of branchial plate with about 18 flattened, plumose, long setae.

Sixth limb: with weakly developed sexual dimorphism. In male, lobe with one short, smooth seta on anterior margin, one short smooth and one middlelength setae in middle of posterior margin, and one hirsute seta on ledge of anterior distal margin. In female: simple lobe with four plumose setae distally, and one short, smooth seta on anterior margin.

Seventh limb anlage: small, elongated lobe, tapering to blunt point distally. Copulatory limb anlage (male or female, indeterminate): large, elongated, rounded lobe.

Furcal ramus: with one long, smooth seta, and nine unequal-length, hirsute setae along rounded distal margin.

Trunk and caudal parts of body bearing fewer than ten body segments (proximal ones indistinct) with several comb-like rows of setula; distalmost (caudal) segment with two short, stout, hirsute setae on distal end; seven next most-distal segments each with one hirsute or incipient seta.

EIGHTH INSTAR (A-1) ( FIGS 1H , 2 , 3H , 11 , 12 )

Male right valve length, 530–590 Mm; height, 310– 340 Mm. Female right valve length, 620–640 Mm; height, 360–380 Mm. Similar in shape and ornament to previous instar, but dorsal margin is conspicuously sinuous, ventral margin is weakly sinuous, and posterior radial ridges are more elongate. Sexual dimorphism in size is more marked than in previous instars. Sinuous dorsal margin indented above dorsomedian sulcus; ventral margin slightly convex. Deep fossae and puncta distributed over most of valve. Approximately 15 small triangular denticles equally spaced along anterior margin of left valve.

Body: with six paired limbs (antennula, antenna, mandibula, maxillula, fifth limbs, and sixth limbs) and furca, plus paired anlage of copulatory limb. Antennula uniramous, consisting of seven articulated podomeres: first podomere, large and trapezoidal, bearing five stout, plumose setae, and some patches of setulae in middle of anterior margin; second podomere, large and triangular, with three hirsute setae on anterior distal corner, one short, smooth seta on posterior distal corner, and some patches of numerous setulae along anterior margin; third podomere, middle-sized and triangular, with one smooth seta at posterior distal corner; fourth podomere, polygonal, depressed distal-proximally, bearing two unequallength, hirsute and one incipient setae on anterior distal margin, and three unequal-length, annulated setae on posterior distal corner; fifth podomere, trapezoidal, and depressed distal-proximally, with two hirsute and one incipient setae on anterior distal margin; sixth podomere, middle-sized, irregular polygon, with one incipient and two stout setae on anterior margin, and one middle-length seta on posterior distal end; seventh podomere, small, irregular, and trapezoidal, with three smooth setae on ledge in middle of anterior margin, and one large, stout, hooklike seta on distal end.

Antenna: biramous, with exopodite and endopodite consisting of two and three podomeres, respectively. Large elongate coxa, dorsal margin, and anterior distal end: each with one smooth seta. Large triangular basis: with two very long and one middlelength, stout, plumose setae on posterior distal corner, and numerous setulae along anterior margin. First podomere of exopodite, trapezoidal, with five very long, annulated setae and one long, smooth seta on posterior distal margin, and numerous setulae along anterior distal margin; second podomere, small, round distally with five pairs of annulated setae, posterior of which is longest, and one very short seta on distal end. First podomere of endopodite, trapezoidal, broadening distally with marginal setulae, bearing three short, spatulate seta on posterior proximal margin, three very long, annulated setae and four smooth setae on anterior to middle distal margin, three long, one middle-length, stout, plumose setae and four short, spatulate setae on posterior distal end; second podomere, irregular polygon forming ledges in anterior and posterior, with three long, annulated setae on ledge in middle of anterior margin, one middle-length, one short, smooth and two hirsute setae on ledge of posterior middle margin, one stout, hook-like seta, one middle-length, smooth, one long, annulated, and one small incipient setae on anterior distal end, and one middle-length, smooth seta on posterior distal end; third podomere, small, irregular polygonal, with one middle-length, spatulate seta on ledge of posterior middle margin, two middle-length, smooth, one stout, bifurcating, and one stout, hirsute setae on distal end.

Mandibula: consisting of coxa, basis, exopodite, and two endopodite podomeres. Coxa: bearing one large endite, with numerous fine teeth on distal end. Basis: elongate, bearing one smooth seta on posterior proximal margin, and exopodite proximally on anterior margin consisting of two long and four short plumose setae; comb/screen of about 32 long, flattened, plumose setae laterally; one short, smooth seta on distal end. First endopodite podomere with one blunt, short seta on proximal end, and one middle-length seta and one short, smooth seta on distal end; second podomere very small, with one long, one middlelength, and one very short, smooth setae on distal end.

Maxillula: consisting of basis, exopodite, and endopodite. Basis: small and irregular, bearing three separate endites, each with some short, hirsute setae. Endopodite (palp): elongate, consisting of three podomeres. First podomere elongate, with comb/ screen of more than about 27 long, flattened, plumose setae along lateral side, two groups of four and three short, sharp setae, respectively, along ventral margin, one blunt, short seta on distal end, and numerous fine setules along dorsal margin; second podomere, with three short, sharp setae along ventral margin, and one short, hirsute seta on dorsodistal end; third podomere, small, narrowing distally, with one middlelength, stout, one short, spatulate, and one short, smooth setae on distal end, and numerous setulae along ventral and dorsal margins. Exopodite consisting of large branchial plate with about 31 flattened, plumose, long setae.

Fifth limb strongly sexually dimorphic: endopodite developed in male, absent in female. In male, basis bearing two long, hirsute setae on distal part and some groups of short setae on lateral part, with finger-like, distal endite bearing three long, plumose setae and several short setae; anterior margin of basis and endite bearing fringe of short setulae; exopodite consisting of well-developed branchial plate with about 20 flattened plumose setae, attached proximally on outer posterior edge of basis; endopodite pediform, consisting of three podomeres (second and third podomeres separated only by a weak constriction), second podomere with one very short setula at distal third, one middle-length, smooth and one very short setae on distal end, third podomere sharpening distally with one very short seta on distal end. In female, basis and exopodite as in male, but endopodite is absent.

Sixth limb: strongly sexually dimorphic. In male, basis bearing two long and two middle-length setae on ventrodistal end (endite), and one short annulated seta on dorsodistal end, plus one distal endite consisting of blunt process, with two middle-length, annulated setae, and one very short, simple seta; exopodite small, almost fused to basis, bearing eight hirsute setae; endopodite consisting of finger-like process tapering distally, with constriction suggestive of two incipient podomeres. In female, only a simple flattened lobe with seven plumose setae.

Seventh limb: absent.

Copulatory limb anlage: elongated lobe with rounded end; larger in male than in female.

Furcal ramus: with one long, smooth, and nine unequal-length, hirsute setae along rounded distal margin.

Trunk and caudal parts of body: consisting of 11 body segments; caudal part of body (distalmost segment) with two hirsute setae in both sexes. Next seven distalmost segments each bearing one hirsute seta in male, with between one and three hirsute setae in female; two or three comb-like rows of setulae developed on each segment.

NINTH INSTAR (ADULT) ( FIGS 1I, 1J , 2 , 3I, J )

Details of the adult instar were previously described and illustrated by Tsukagoshi et al. (2006).

Male right valve length, 610–640 Mm; height, 360– 380 Mm. Female right valve length, 690–720 Mm; height, 410–430 Mm. Sexual dimorphism in size and shape: remarkable. Male: similar in shape to previous instar. In both sexes: dorsal margin conspicuously sinuous; ventral margin slightly convex. Posterior radial ridges: stronger; fossae and puncta in marginal areas, larger and deeper. Dorsomedian sulcus: conspicuous. Approximately 20 small triangular denticles equally spaced along anterior margin of left valve. Body: with six paired limbs (antennula, antenna, mandibula, maxillula, fifth limbs, sixth limbs), and paired furca and copulatory limb. Very strong sexual dimorphism: in fifth and sixth limbs.

We note that in the original description and illustrations by Tsukagoshi et al. (2006), figure 5f and l were erroneously stated to show dorsal views of male and female carapaces, whereas in fact they show anterior views.

Figures

Figure 1. External views of the carapace of Keijcyoidea infralittoralis at different stages of ontogeny. A, first (A-8) instar (SUM-CO-1541); B, second (A-7) instar (SUM-CO-1542); C, third (A-6) instar (SUM-CO-1543); D, fourth (A-5) instar (SUM-CO-1544); E, fifth (A-4) instar (SUM-CO-1545); F, sixth (A-3) instar (SUM-CO-1546); G, seventh (A-2) instar (SUM-CO-1547); H, eighth (A-1) instar (SUM-CO-1548); I, ninth (final) instar (adult male; SUM-CO-1393, holotype); J, ninth (final) instar (adult female; SUM-CO-1399, paratype). The scale is not the same for all of the carapaces illustrated.

Figure 2. Length and height of carapaces in each instar of Keijcyoidea infralittoralis.

Figure 3. Ontogeny of Keijcyoidea infralittoralis: internal views with limbs. A, first (A-8) instar (SUM-CO-1549); B, second (A-7) instar (SUM-CO-1550); C, third (A-6) instar (SUM-CO-1551); D, fourth (A-5) instar (SUM-CO-1552); E, fifth (A-4) instar (SUM-CO-1553); F, sixth (A-3) instar (SUM-CO-1554); G, seventh (A-2) instar (SUM-CO-1555); H, eighth (A-1) instar (male, SUM-CO-1556); I, ninth (adult) instar (male, SUM-CO-1557); J, ninth (adult) instar (female, SUM-CO-1558). A–C, E, G–I, right valve with soft parts; D, F, J, left valve with soft parts. Scale bar: 100 Mm.

Figure 4. Limbs of the first (A-8) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, caudal part with anlagen of maxillula and furca. Arabic numerals indicate the order of podomeres from proximal to distal; cp, caudal process; en, endopodite; ex, exopodite; f, furca; l4, fourth limb; pp, protopodite. Scale bar: 50 Mm. A, B, D, SUM-CO-1559; C, SUM-CO-1560.

Figure 5. Limbs of the second (A-7) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, anlage of maxillula; E, caudal part with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; cp, caudal process; cx, coxa; en, endopodite; ex, exopodite; f, furca. Scale bar: 50 Mm. A, B, D, E, SUM-CO-1561; C, SUM-CO-1562.

Figure 6. Limbs of the third (A-6) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, maxillula; E, anlage of fifth limb; F, trunk and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca. Scale bar: 50 Mm. A, B, SUM-CO-1563; C, D, SUM-CO-1564; E, F, SUM-CO-1565.

Figure 7. Limbs of the fourth (A-5) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, maxillula; E, anlage of fifth limb; F, trunk and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca. Scale bar: 50 Mm. A, B, SUM-CO-1566; C, SUM-CO-1567; D, SUM-CO-1568; E, F, SUM-CO-1569.

Figure 8. Limbs of the fifth (A-4) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, maxillula; E, anlage of fifth limb; F, segmented trunk, with anlage of sixth limb, and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca; l6, sixth limb. Scale bar: 50 Mm. A, B, D–F, SUM-CO-1570; C, SUM-CO-1571.

Figure 9. Limbs of the sixth (A-3) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, maxillula; E, fifth limb; F, segmented trunk with intermediate form of sixth limb, anlagen of seventh limb, copulatory organ, and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; co, copulatory organ; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca; l6, sixth limb; l7, seventh limb. Scale bar: 100 Mm. A, B, SUM-CO-1572 (male); C, SUM-CO-1573 (male); D, SUM-CO-1574 (male); E, SUM-CO-1575 (female); F, SUM-CO-1576 (male).

Figure 10. Limbs of the seventh (A-2) instar of Keijcyoidea infralittoralis. A, antennule; B, antenna; C, mandibula; D, maxillula; E, fifth limb of male; F, fifth limb of female; G, segmented trunk with intermediate form of sixth limb, anlagen of seventh limb, copulatory organ, and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; co, copulatory organ; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca; l6, sixth limb; l7, seventh limb. Scale bar: 100 Mm. A–E, G, SUM-CO-1577 (male); F, SUM-CO-1578 (female).

Figure 11. Limbs of the eighth (A-1) instar of Keijcyoidea infralittoralis (1 of 2). A, antennule; B, antenna; C, maxillula; D, fifth limb of female; E, sixth limb of female. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; cx, coxa; ed, endite; en, endopodite; ex, exopodite; pp, protopodite. Scale bar: 100 Mm. A–C, SUM-CO-1579 (male); D, SUM-CO-1580 (female); E, SUM-CO-1581 (femele).

Figure 12. Limbs of the eighth (A-1) instar of Keijcyoidea infralittoralis (two of two). A, mandibula; B, fifth limb of male; C, sixth limb of male; D, male segmented trunk, with anlage of copulatory organ, and caudal part, with furca and caudal process; E, female segmented trunk, with anlage of copulatory organ, and caudal part, with furca and caudal process. Arabic numerals indicate the order of podomeres from proximal to distal; ba, basis; co, copulatory organ; cp, caudal process; cx, coxa; ed, endite; en, endopodite; ex, exopodite; f, furca; pp, protopodite. Scale bar: 100 Mm. A, SUM-CO-1582 (male); B–D, SUM-CO-1579 (male); E, SUM-CO-1581 (female).